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• • 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
  • C08F14/185—Monomers containing fluorine not covered by the groups C08F14/20 - C08F14/28
• • 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
  • C08F6/00—Post-polymerisation treatments
  • C08F6/14—Treatment of polymer emulsions
  • C08F6/16—Purification
• • 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
  • C08F114/00—Homopolymers 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
  • C08F114/18—Monomers containing fluorine
  • C08F114/26—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
  • C08F2/20—Suspension polymerisation with the aid of macromolecular dispersing agents
• • 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
  • C08F2/22—Emulsion polymerisation
  • C08F2/24—Emulsion polymerisation with the aid of emulsifying agents
  • C08F2/26—Emulsion polymerisation with the aid of emulsifying agents anionic
• • 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
  • C08F214/00—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
  • C08F214/18—Monomers containing fluorine
  • C08F214/26—Tetrafluoroethene
  • C08F214/262—Tetrafluoroethene with fluorinated vinyl ethers
• • 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
  • C08F214/00—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
  • C08F214/18—Monomers containing fluorine
  • C08F214/26—Tetrafluoroethene
  • C08F214/265—Tetrafluoroethene with non-fluorinated comonomers
• • 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 disclosure relates to a method for producing an aqueous fluoropolymer dispersion and to an aqueous fluoropolymer dispersion.
• Patent Documents 1 and 2 describe, in an example of polymerizing tetrafluoroethylene, that the supply of tetrafluoroethylene to the autoclave was stopped, and the autoclave was kept under nitrogen bubbling for 16 hours to remove residual monomers from the polymerization, and the latex was then removed.
• the present disclosure aims to provide a new method for producing a fluoropolymer and a new aqueous dispersion containing a fluoropolymer.
• a method for producing an aqueous fluoropolymer dispersion comprising: polymerizing a fluoromonomer in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion containing a fluoropolymer; and blowing an oxygen-containing gas into the aqueous dispersion, or contacting the aqueous dispersion with an oxidizing agent, or contacting the aqueous dispersion with an alcohol to obtain the aqueous fluoropolymer dispersion.
• the present disclosure aims to provide a new method for producing a fluoropolymer and a new aqueous dispersion containing a fluoropolymer.
• FIG. 1 shows first differential spectra obtained by analyzing the aqueous dispersions obtained in Examples 6, 8, 13, and 14 and Comparative Example 1 using an electron spin resonance method.
• melt processable means that the polymer can be melted and processed using conventional processing equipment such as extruders and injection molding machines. Therefore, melt processable fluororesin typically has a melt flow rate of 0.01 to 500 g/10 min, as measured by the measurement method described below.
• polytetrafluoroethylene is preferably a fluoropolymer in which the content of tetrafluoroethylene units relative to the total polymerized units is 99 mol % or more.
• the content of each monomer constituting the fluoropolymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.
• organic group means a group containing one or more carbon atoms, or a group formed by removing one hydrogen atom from an organic compound.
• the organic group is preferably an alkyl group which may have one or more substituents.
• ranges represented by endpoints include all numbers within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).
• At least 1 includes all numbers equal to or greater than 1 (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).
• a fluoropolymer-containing aqueous dispersion is prepared by polymerizing a fluoromonomer in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium, and an aqueous fluoropolymer dispersion is obtained by blowing an oxygen-containing gas into the aqueous dispersion, or by contacting the aqueous dispersion with an oxidizing agent, or by contacting the aqueous dispersion with an alcohol.
• a fluoromonomer is polymerized in the presence of a fluorine-containing surfactant, a polymerization initiator and an aqueous medium to prepare an aqueous dispersion containing a fluoropolymer.
• the polymerization of fluoromonomers can be carried out by charging a reactor with fluoromonomers, a fluorine-containing surfactant, a polymerization initiator, an aqueous medium, and other additives as necessary, stirring the contents of the reactor, and maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the polymerization reaction has begun, additional fluoromonomers, polymerization initiators, fluorine-containing surfactants, chain transfer agents, etc. may be added depending on the purpose.
• the method for polymerizing fluoromonomers is not particularly limited, but emulsion polymerization is preferred.
• the fluorine-containing surfactant used in the polymerization of the fluoromonomer is not particularly limited as long as it is a surfactant containing at least one fluorine atom, and any conventionally known fluorine-containing surfactant can be used.
• fluorine-containing surfactants examples include anionic fluorine-containing surfactants.
• Anionic fluorine-containing surfactants may be, for example, surfactants containing fluorine atoms with a total carbon number of 20 or less excluding the anionic group.
• the fluorine-containing surfactant may also be a surfactant containing fluorine in the anionic moiety having a molecular weight of 1,000 or less.
• anionic portion refers to the portion of the above fluorine-containing surfactant excluding the cation.
• F(CF 2 ) n1 COOM represented by formula (I) described below, it is the portion "F(CF 2 ) n1 COO”.
• the above-mentioned fluorosurfactant also includes a fluorosurfactant having a LogPOW of 3.5 or less.
• the LogPOW is a partition coefficient between 1-octanol and water, and is expressed as LogP [wherein P represents the ratio of the fluorosurfactant concentration in octanol to the fluorosurfactant concentration in water when a 1:1 octanol/water mixture containing the fluorosurfactant undergoes phase separation].
• a standard substance heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid
• fluorine-containing surfactants include those described in U.S. Patent Application Publication No. 2007/0015864, U.S. Patent Application Publication No. 2007/0015865, U.S. Patent Application Publication No. 2007/0015866, U.S. Patent Application Publication No. 2007/0276103, U.S. Patent Application Publication No. 2007/0117914, U.S. Patent Application Publication No. 2007/142541, U.S. Patent Application Publication No. 2008/0015319, and U.S. Patent No. 3,250,808. Examples of such compounds include those described in U.S. Pat. No.
• the anionic fluorine-containing surfactant may be a compound represented by the following general formula (N 0 ): X n0 - Rf n0 - Y 0 (N 0 ) (In the formula, X n0 is H, Cl or F. Rf n0 is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms in which some or all of the H's are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H's may be substituted with Cl. Y 0 is an anionic group.
• the anionic group of Y 0 may be -COOM, -SO 2 M or -SO 3 M, and may be -COOM or -SO 3 M.
• M is H, a metal atom, NR 7 4 , an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent
• R 7 is H or an organic group.
• the metal atom includes alkali metals (group 1) and alkaline earth metals (group 2), such as Na, K, or Li.
• R 7 may be H or a C 1-10 organic group, may be H or a C 1-4 organic group, or may be H or a C 1-4 alkyl group.
• M may be H, a metal atom or NR 7 4 , which may be H, an alkali metal (group 1), an alkaline earth metal (group 2) or NR 7 4 , which may be H, Na, K, Li or NH 4 .
• Rf n0 may be one in which 50% or more of H is substituted with fluorine.
• the compound represented by the above general formula (N 0 ) includes a compound represented by the following general formula (N 1 ): X n0 - (CF 2 ) m1 - Y 0 (N 1 ) (wherein X n0 is H, Cl or F, m1 is an integer of 3 to 15, and Y 0 is as defined above), a compound represented by the following general formula (N 2 ): Rf n1 -O-(CF(CF 3 )CF 2 O) m2 CFX n1 -Y 0 (N 2 ) (wherein Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, X n1 is F or CF 3 , and Y 0 is as defined above), a compound represented by the following general formula (N 3 ): Rf n2 (CH 2 ) m3 - (Rf n3 ) q - Y 0 (
• the compound represented by the above general formula (N 0 ) includes perfluorocarboxylic acid (I) represented by the following general formula (I), ⁇ -H perfluorocarboxylic acid (II) represented by the following general formula (II), perfluoroether carboxylic acid (III) represented by the following general formula (III), perfluoroalkyl alkylene carboxylic acid (IV) represented by the following general formula (IV), perfluoroalkoxy fluorocarboxylic acid (V) represented by the following general formula (V), perfluoroalkyl sulfonic acid (VI) represented by the following general formula (VII), ⁇ -H perfluoro sulfonic acid (VII) represented by the following general formula (VII), perfluoroalkyl alkylene sulfonic acid (VIII) represented by the following general formula (VIII), alkyl alkylene carboxylic acid (IX) represented by the following general formula (IX), fluorocarboxylic acid (
• the perfluorocarboxylic acid (I) is represented by the following general formula (I): F (CF 2 ) n1 COOM (I) (wherein n1 is an integer of 3 to 14, M is H, a metal atom, NR 7 4 , an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, and R 7 is H or an organic group.)
• ⁇ -H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF 2 ) n2 COOM (II) (wherein n2 is an integer from 4 to 15, and M is as defined above).
• the perfluoroether carboxylic acid (III) is represented by the following general formula (III): Rf 1 -O-(CF(CF 3 )CF 2 O) n3 CF(CF 3 )COOM (III) (wherein Rf1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above).
• the perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): Rf 2 (CH 2 ) n4 Rf 3 COOM (IV) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.)
• the alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): Rf 4 -O-CY 1 Y 2 CF 2 -COOM (V) (wherein Rf 4 is a linear or branched partially or completely fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond and/or a chlorine atom, Y 1 and Y 2 are the same or different and are H or F, and M is as defined above).
• the perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F (CF 2 ) n5 SO 3 M (VI) (wherein n5 is an integer from 3 to 14, and M is as defined above).
• the ⁇ -H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF 2 ) n6 SO 3 M (VII) (wherein n6 is an integer from 4 to 14, and M is as defined above).
• the perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII): Rf5 ( CH2 ) n7SO3M (VIII ) (wherein Rf5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is as defined above).
• the alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): Rf 6 (CH 2 ) n8 COOM (IX) (wherein Rf6 is a linear or branched partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer from 1 to 3, and M is as defined above).
• the fluorocarboxylic acid (X) is represented by the following general formula (X): Rf 7 -O-Rf 8 -O-CF 2 -COOM (X) (wherein Rf 7 is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms which may contain an ether linkage and/or a chlorine atom; Rf 8 is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms; and M is as defined above).
• the alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf 9 -O-CY 1 Y 2 CF 2 -SO 3 M (XI) (In the formula, Rf 9 is a linear or branched alkyl group having 1 to 12 carbon atoms which may contain an ether bond and which is partially or completely fluorinated and may contain chlorine; Y 1 and Y 2 are the same or different and are H or F; and M is as defined above.)
• the compound (XII) is represented by the following general formula (XII): (wherein X 1 , X 2 and X 3 may be the same or different and are H, F and a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms which may contain an ether bond, Rf 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y 0 is an anionic group). Y 0 may be -COOM, -SO 2 M or -SO 3 M, and may be -SO 3 M or COOM, where M is as defined above. Examples of L include a single bond, and a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.
• the compound (XIII) is represented by the following general formula (XIII): Rf 11 -O-(CF 2 CF(CF 3 )O) n9 (CF 2 O) n10 CF 2 COOM (XIII) (wherein Rf 11 is a fluoroalkyl group containing chlorine and having 1 to 5 carbon atoms, n9 is an integer from 0 to 3, n10 is an integer from 0 to 3, and M is as defined above).
• Compound (XIII) is represented by CF 2 ClO(CF 2 CF(CF 3 )O) n9 (CF 2 O) n10 CF 2 COONH 4 (a mixture having an average molecular weight of 750, wherein n9 and n10 are as defined above).
• anionic fluorine-containing surfactant examples include carboxylic acid surfactants and sulfonic acid surfactants.
• the fluorine-containing surfactant may be one type of fluorine-containing surfactant or a mixture containing two or more types of fluorine-containing surfactants.
• the fluorine-containing surfactant preferably has no methylene group (-CH 2 -), and more preferably has no C-H bond.
• a fluorine-containing surfactant that has no methylene group (-CH 2 -) or no C-H bond in the molecule the polymerization of the fluoromonomer in the presence of an aqueous medium can be smoothly carried out.
• the number of H atoms in the hydrophobic group of the fluorine-containing surfactant is preferably 0 or 1, more preferably 0.
• the number of carbon atoms in the hydrophobic group of the fluorine-containing surfactant having a hydrophobic group and a hydrophilic group is preferably 1 to 50, more preferably 3 to 20, and even more preferably 6 to 12.
• the hydrophobic group usually constitutes the above-mentioned "part other than the anionic group" in the molecular structure of the fluorine-containing surfactant.
• the hydrophilic group include the groups exemplified as the anionic group of Y 0.
• the fluorine-containing surfactant may be a saturated fluorinated surfactant in which all the carbon atoms bonded to the hydrophobic group are substituted with fluorine atoms.
• fluorine-containing surfactant examples include, among the above-mentioned anionic fluorine-containing surfactants, perfluorocarboxylic acid (I) represented by general formula (I), ⁇ -H perfluorocarboxylic acid (II) represented by general formula (II), perfluoroether carboxylic acid (III) represented by general formula (III), perfluoroalkyl alkylene carboxylic acid (IV) represented by general formula (IV), perfluoroalkoxy fluorocarboxylic acid (V) represented by general formula (V), perfluoroalkyl sulfonic acid (VI) represented by general formula (VII), ⁇ -H perfluoro sulfonic acid (VII) represented by general formula (VII), perfluoroalkyl alkylene sulfonic acid (VIII) represented by general formula (VIII), and perfluoroalkyl alkylene sulfonic acid (VIII) represented by general formula (X): Rf 7
• fluorine-containing surfactant examples include compounds represented by the following formula:
• the fluorine-containing surfactant may be a mixture of these compounds.
• the amount of the fluorine-containing surfactant added is preferably 10 ppm by mass to 10% by mass, more preferably 100 ppm by mass or more, even more preferably 300 ppm by mass or more, more preferably 5% by mass or less, and even more preferably 1% by mass or less, relative to the aqueous medium.
• the polymerization initiator used for the polymerization of the fluoromonomer is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and/or water-soluble polymerization initiators can be used. Furthermore, it can also be combined with a reducing agent or the like to initiate polymerization as a redox.
• concentration of the polymerization initiator is appropriately determined depending on the type of monomer, the molecular weight of the desired fluoropolymer, and the reaction rate.
• an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used as the polymerization initiator.
• the oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and also di( ⁇ -hydro-dodecafluoroheptanoyl) peroxide, di( ⁇ -hydro-tetradecafluorooctanoyl) peroxide, di( ⁇ -hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(per
• Representative examples include di[perfluoro(or fluorochloro)acyl]peroxides such as di( ⁇ -hexafluorobutyryl) peroxide, di( ⁇ -chloro-decafluorohexanoyl) peroxide, di( ⁇ -chloro-tetradecafluorooctanoyl) peroxide, ⁇ -hydro-dodecafluoroheptanoyl- ⁇ -hydrohexadecafluorononanoyl-peroxide, ⁇ -chloro-hexafluorobutyryl- ⁇ -chloro-decafluorohexanoyl-peroxide, ⁇ -hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(
• the water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium, potassium, or sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, or percarbonic acid; organic peroxides such as disuccinic acid peroxide or diglutaric acid peroxide; t-butyl permaleate; or t-butyl hydroperoxide.
• a reducing agent such as sulfites may also be included, and the amount used may be 0.1 to 20 times the amount of the peroxide.
• a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator.
• oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and cerium ammonium nitrate.
• reducing agents include sulfites, bisulfites, bromates, diimines, and oxalic acid.
• persulfates include ammonium persulfate and potassium persulfate.
• sulfites include sodium sulfite and ammonium sulfite.
• a copper salt or an iron salt to the combination of redox initiators.
• copper salts include copper (II) sulfate
• iron salts include iron (II) sulfate.
• the redox initiator may be, for example, potassium permanganate/oxalic acid, ammonium persulfate/bisulfite/ferrous sulfate, manganese triacetate/oxalic acid, cerium ammonium nitrate/oxalic acid, bromate/bisulfite, etc., with potassium permanganate/oxalic acid being preferred.
• potassium permanganate/oxalic acid either the oxidizing agent or the reducing agent may be charged in advance into the polymerization tank, and then the other may be added continuously or intermittently to initiate polymerization.
• potassium permanganate/oxalic acid it is preferred to charge oxalic acid into the polymerization tank and continuously add potassium permanganate thereto.
• the amount of polymerization initiator to be added is not particularly limited, but it is sufficient to add an amount at least to the extent that the polymerization rate does not decrease significantly (for example, a few ppm relative to the water concentration) all at once at the beginning of the polymerization, or gradually, or continuously.
• the upper limit is the range in which the reaction temperature can be increased while removing heat from the equipment surface using the heat of polymerization reaction, and a more preferable upper limit is the range in which the heat of polymerization reaction can be removed from the equipment surface.
• the amount of polymerization initiator added is preferably an amount that remains in the aqueous dispersion containing the fluoropolymer without the entire amount of the fluoromonomer being consumed in the polymerization.
• the amount of polymerization initiator added is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, even more preferably 20 ppm by mass or more, and particularly preferably 50 ppm by mass or more, based on the mass of the aqueous medium.
• the amount of polymerization initiator at the end of polymerization can be calculated from the polymerization temperature, reaction time, and half-life of the initiator.
• the concentration of polymerization initiator at the end of polymerization is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, even more preferably 20 ppm by mass or more, and particularly preferably 50 ppm by mass or more, based on the mass of the aqueous medium.
• adding a decomposer can adjust the radical concentration during polymerization.
• decomposers include sulfites, bisulfites, bromates, diimines, oxalic acid, copper salts, and iron salts.
• sulfites include sodium sulfite and ammonium sulfite.
• copper salts include copper (II) sulfate
• iron salts include iron (II) sulfate.
• the amount of decomposer added is in the range of 25 to 300 mass% based on the amount of oxidizing agent combined as a polymerization initiator (redox initiator).
• the amount of decomposer added is preferably 25 to 150 mass%, more preferably 50 to 100 mass%. In addition, it is preferable to add the decomposer after 5 mass% of the total fluoromonomer consumed in the polymerization reaction has been polymerized, and more preferably after 10 mass% has been polymerized.
• the amount of decomposer added is preferably an amount equivalent to 0.1 to 20 mass ppm of the mass of the aqueous medium used, and more preferably an amount equivalent to 3 to 10 mass ppm.
• the aqueous medium used for the polymerization of the fluoromonomer means a liquid containing water, which is a reaction medium for carrying out the polymerization.
• the aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as ether or ketone, and/or a fluorine-containing organic solvent having a boiling point of 40° C. or less.
• an aqueous medium containing only water or an aqueous medium containing only water and a non-fluorine-containing organic solvent is preferred, since it allows the polymerization of the fluoromonomer to proceed smoothly and also suppresses a decrease in the efficiency of removing the fluorine-containing surfactant and fluorine-containing compound due to heat treatment after the preparation of the aqueous dispersion, and an aqueous medium containing only water is more preferred.
• the water content in the aqueous medium is preferably 90% or more, more preferably 95% or more, even more preferably 99.0% or more, still more preferably 99.5% or more, particularly preferably 99.9% or more, and may be 100%, based on the mass of the aqueous medium, because this allows the polymerization of the fluoromonomer to proceed smoothly and also prevents a decrease in the efficiency of removing the fluorinated surfactant and fluorinated compound due to heat treatment after the preparation of the aqueous dispersion.
• the fluoromonomer used in the polymerization has at least one fluorine atom and at least one double bond.
• fluoromonomer tetrafluoroethylene [TFE], hexafluoropropylene [HFP], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VdF], trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, fluoromonomer represented by the general formula (100): CHX 101 ⁇ CX 102 Rf 101 (wherein, X 101 and X 102 are one H, the other F, and Rf 101 is a straight-chain or branched fluoroalky
• the perfluoroalkyl group may contain etheric oxygen and a -SO 2 F group.
• n represents an integer of 0 to 3.
• the n Y 151 may be the same or different.
• Y 152 represents a fluorine atom, a chlorine atom or a -SO 2 F group.
• m represents an integer of 1 to 5.
• the m Y 152 may be the same or different.
• a 151 represents -SO 2 X 151 , -COZ 151 or -POZ 152 Z 153.
• X 151 represents F, Cl, Br, I, -OR 151 or -NR 152 R 153.
• Z 151 , Z 152 and Z 153 are the same or different and each represents -NR 154 R 155 or -OR 156.
• R 151 , R 152 , R 153 , R 154 , R 155 and R 156 are the same or different and represent H, ammonium, an alkali metal, an alkyl group which may contain a fluorine atom, an aryl group, or a sulfonyl-containing group.
• perfluoro organic group refers to an organic group in which all hydrogen atoms bonded to carbon atoms are replaced with fluorine atoms.
• the perfluoro organic group may have an ether oxygen.
• fluoromonomer represented by the general formula (110) is a fluoromonomer in which Rf 111 is a perfluoroalkyl group having 1 to 10 carbon atoms.
• the perfluoroalkyl group preferably has 1 to 5 carbon atoms.
• Examples of the perfluoro organic group in the general formula (110) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.
• the fluoromonomer represented by the general formula (110) further includes those in which Rf 111 in the above general formula (110) is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and those in which Rf 111 is a group represented by the following formula:
• Rf 111 is a group represented by the following formula: CF 3 CF 2 CF 2 -(O-CF(CF 3 )-CF 2 ) n - (wherein n is an integer of 1 to 4).
• CF 2 CF-ORf 161 (wherein Rf 161 represents a perfluoroalkyl group having 1 to 10 carbon atoms) is preferred. Rf 161 is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.
• the fluoroalkyl vinyl ether is preferably at least one selected from the group consisting of fluoromonomers represented by the general formulas (160), (130) and (140).
• the fluoromonomer represented by general formula (160) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).
• the fluoromonomer represented by general formula (130) is preferably at least one selected from the group consisting of CF 2 ⁇ CFOCF 2 OCF 3 , CF 2 ⁇ CFOCF 2 OCF 2 CF 3 and CF 2 ⁇ CFOCF 2 OCF 2 CF 2 OCF 3 .
• fluoromonomer represented by the general formula (100) a fluoromonomer in which Rf 101 is a linear fluoroalkyl group is preferred, and a fluoromonomer in which Rf 101 is a linear perfluoroalkyl group is more preferred.
• the carbon number of Rf 101 is preferably 1 to 6.
• Rf 111 in the general formula (180) is the same as Rf 111 in the general formula (110).
• Rf 111 is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms.
• the fluoroalkyl allyl ether represented by general formula (180) is preferably at least one selected from the group consisting of CF 2 ⁇ CF-CF 2 -O-CF 3 , CF 2 ⁇ CF-CF 2 -O-C 2 F 5 , CF 2 ⁇ CF-CF 2 -O-C 3 F 7 and CF 2 ⁇ CF-CF 2 -O-C 4 F 9 , more preferably at least one selected from the group consisting of CF 2 ⁇ CF-CF 2 -O-C 2 F 5 , CF 2 ⁇ CF-CF 2 -O-C 3 F 7 and CF 2 ⁇ CF-CF 2 -O-C 4 F 9 , and even more preferably CF 2 ⁇ CF-CF 2 -O-CF 2 CF 2 CF 3 .
• the fluorinated vinyl heterocycle may be represented by the general formula (230): (Wherein, X231 and X232 are independently F, Cl, a methoxy group or a fluorinated methoxy group, and Y231 is a group of formula Y232 or formula Y233 .
• CX 191 2 CX 192 -R f 191 X 193 (wherein X 191 and X 192 are independently a hydrogen atom, a fluorine atom or CH 3 , R f 191 is a fluoroalkylene group, a perfluoroalkylene group,
• Z 221 is a linear or branched alkylene group having 1 to 18 carbon atoms, which may have an oxygen atom, a cycloalkylene group having 3 to 18 carbon atoms, an at least partially fluorinated alkylene group or oxyalkylene group having 1 to 10 carbon atoms, or -(Q) p -CF 2 O-(CF 2 CF 2 O) m (CF 2 O) n -CF 2 -(Q) p - (wherein Q is an alkylene group or an oxyalkylene group, p is 0 or 1, and m/n is 0.2 to 5), and is a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10,000.
• X 183 and X 193 are preferably iodine atoms.
• R f 181 and R f 191 are preferably perfluoroalkylene groups having 1 to 5 carbon atoms.
• R 181 is preferably a hydrogen atom.
• X 201 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH 2 I.
• X 211 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH 2 OH.
• the fluoromonomer and a non-fluorine-containing monomer may be polymerized.
• the non-fluorine-containing monomer include hydrocarbon monomers that are reactive with the fluoromonomer.
• the hydrocarbon monomer include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, vinyl para-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochlor
• vinyl esters such as vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester; and (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate,
• the fluorine-free monomer may also be a functional group-containing hydrocarbon monomer (excluding monomers that provide crosslinking sites).
• the functional group-containing hydrocarbon monomer include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; fluorine-free monomers having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; fluorine-free monomers having a sulfo group such as vinyl sulfonic acid; fluorine-free monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl
• the desired fluoropolymer particles can be obtained by polymerizing one or more of the above fluoromonomers.
• the fluoromonomer can be polymerized in the presence of a chain transfer agent.
• the polymerization rate and molecular weight can be adjusted by using the chain transfer agent.
• the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, methanol, isopropanol, acetone, various mercaptans, various halogenated hydrocarbons such as carbon tetrachloride, and cyclohexane.
• the chain transfer agent is preferably a hydrocarbon chain transfer agent or alcohol.
• the hydrocarbon chain transfer agent is not particularly limited as long as it contains only carbon atoms and hydrogen atoms, but is preferably an alkane having 1 to 5 carbon atoms, and more preferably at least one selected from the group consisting of isopentane, methane, ethane, and propane.
• the alcohol is preferably an alcohol having 1 to 3 carbon atoms, and is preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol.
• Bromine compounds or iodine compounds may be used as chain transfer agents.
• the polymerization method using bromine compounds or iodine compounds includes, for example, a method of polymerizing fluoromonomers in an aqueous medium in the presence of bromine compounds or iodine compounds in a substantially oxygen-free state (iodine transfer polymerization method).
• bromine compounds or iodine compounds used include, for example, compounds represented by the general formula: R a I x B ry (wherein x and y are each an integer of 0 to 2 and satisfy 1 ⁇ x+y ⁇ 2, and R a is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom).
• R a I x B ry wherein x and y are each an integer of 0 to 2 and satisfy 1 ⁇ x+y ⁇ 2, and R a is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom.
• bromine compound or iodine compound examples include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF 2 Br 2 , BrCF 2 CF 2 Br, CF 3 CFBrCF 2 Br, CFClBr 2 , BrCF 2 C
• 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane in terms of polymerization reactivity, crosslinking reactivity, and ease of availability.
• the amount of chain transfer agent used is usually 1 to 50,000 ppm by mass, preferably 1 to 20,000 ppm by mass, based on the total amount of fluoromonomer supplied.
• the amount of chain transfer agent used is preferably an amount that is completely consumed during polymerization of the fluoromonomer and does not remain in the aqueous dispersion containing the fluoropolymer, so as not to reduce the efficiency of removing the fluorinated surfactant and fluorinated compound by heat treatment after the preparation of the aqueous dispersion as much as possible.
• the amount of chain transfer agent used is more preferably 10,000 ppm by mass or less, even more preferably 5,000 ppm by mass or less, still more preferably 1,000 ppm by mass or less, particularly preferably 500 ppm by mass or less, and most preferably 200 ppm by mass or less, based on the total amount of fluoromonomer supplied.
• the chain transfer agent may be added to the reaction vessel all at once before the start of polymerization, may be added all at once after the start of polymerization, may be added in multiple portions during polymerization, or may be added continuously during polymerization.
• additives such as buffers, pH adjusters, stabilizing aids, and dispersion stabilizers can be used.
• radical scavengers and decomposers can be added to adjust the polymerization rate and molecular weight.
• fluorine-free anionic surfactants, fluorine-free nonionic surfactants, fluorine-free cationic surfactants, and the like can be used.
• the stabilizing aid is preferably paraffin wax, fluorine-based oil, fluorine-based solvent, silicone oil, etc.
• the stabilizing aid may be used alone or in combination of two or more.
• the stabilizing aid is more preferably paraffin wax.
• Paraffin wax may be liquid, semi-solid, or solid at room temperature, but is preferably a saturated hydrocarbon having 12 or more carbon atoms.
• the melting point of paraffin wax is usually preferably 40 to 65°C, more preferably 50 to 65°C.
• the amount of the stabilizing aid used is preferably 0.1 to 12 mass % based on the mass of the aqueous medium used, and more preferably 0.1 to 8 mass %. It is desirable that the stabilizing aid is sufficiently hydrophobic and completely separates from the aqueous dispersion after polymerization so as not to become a contaminating component.
• the polymerization of the fluoromonomer can be carried out under normal pressure and temperature.
• the polymerization temperature is 5 to 120°C
• the polymerization pressure is 0.05 to 10 MPaG.
• the polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer, the molecular weight of the target fluoropolymer, the reaction rate, etc.
• the polymerization pressure is preferably more than 0.05 MPa, more preferably more than 0.10 MPaG, and even more preferably more than 0.20 MPaG.
• Fluoropolymers such as fluororesins and fluororubbers can be obtained by polymerization of fluoromonomers.
• Fluoropolymers include polytetrafluoroethylene [PTFE], TFE/FAVE copolymer [PFA], TFE/fluoroalkyl allyl ether copolymer, TFE/HFP copolymer [FEP], ethylene [Et]/TFE copolymer [ETFE], Et/TFE/HFP copolymer, polychlorotrifluoroethylene [PCTFE], CTFE/TFE copolymer, Et/CTFE copolymer, polyvinyl fluoride [PVF], polyvinylidene fluoride [PVdF], VdF/TFE copolymer, fluoromonomer/vinyl ester copolymer, and polymers of fluoromonomers represented by the general formula (150).
• At least one type selected from the group consisting of PTFE, PFA and FEP is preferred, as the effects of the manufacturing method of the present disclosure are most pronounced, and at least one type selected from the group consisting of PTFE and PFA is more preferred.
• PTFE may be homo-PTFE or modified PTFE.
• Modified PTFE contains TFE units and modified monomer units based on modified monomers copolymerizable with TFE.
• PTFE may be high molecular weight PTFE that is non-melt processable and fibrillable, or low molecular weight PTFE that is melt processable and not fibrillable.
• the modified monomer is not particularly limited as long as it can be copolymerized with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene [HFP]; chlorofluoroolefins such as CTFE; hydrogen-containing fluoroolefins such as trifluoroethylene and VdF; fluoroalkyl vinyl ethers [FAVE]; fluoroalkyl allyl ethers; perfluoroalkyl ethylene; ethylene; fluorine-containing vinyl ethers having nitrile groups, etc.
• the modified monomer used may be one type or multiple types.
• the fluororubber may be partially fluorinated rubber or perfluororubber.
• partially fluorinated rubber examples include VdF-based fluororubber, TFE/propylene (Pr)-based fluororubber, TFE/propylene/VdF-based fluororubber, ethylene/HFP-based fluororubber, ethylene/HFP/VdF-based fluororubber, ethylene/HFP/TFE-based fluororubber, and ethylene/HFP/FAVE-based rubber.
• at least one selected from the group consisting of VdF-based fluororubber and TFE/propylene-based fluororubber is preferred.
• VdF-based fluorororubbers include VdF/HFP-based rubber, VdF/HFP/TFE-based rubber, VdF/CTFE-based rubber, VdF/CTFE/TFE-based rubber, VdF/fluoromonomer-based rubber represented by general formula (100), VdF/fluoromonomer/TFE-based rubber represented by general formula (100), VdF/perfluoro(methyl vinyl ether) [PMVE]-based rubber, VdF/PMVE/TFE-based rubber, VdF/PMVE/TFE/HFP-based rubber, etc.
• perfluororubber at least one selected from the group consisting of perfluororubbers containing TFE, for example, TFE/fluoromonomer copolymers represented by general formula (110), (130) or (140), and TFE/fluoromonomer copolymers representing general formula (110), (130) or (140)/monomer copolymers providing crosslinking sites is preferred.
• the fluoropolymer contains a fluoropolymer containing fluoroalkyl vinyl ether units.
• An aqueous dispersion containing a fluoropolymer containing fluoroalkyl vinyl ether units can be prepared by polymerizing a fluoroalkyl vinyl ether as a fluoromonomer.
• a fluoroalkyl vinyl ether is used as a fluoromonomer
• a compound represented by general formula (2) perfluoroalkanoic acid
• An aqueous dispersion containing a fluoropolymer containing fluoroalkyl vinyl ether units may contain a compound represented by general formula (2) as a water-soluble fluorine-containing compound.
• the content of fluoroalkyl vinyl ether units in the fluoropolymer is preferably 0.0000001 to 30 mol %, more preferably 0.000001 mol % or more, even more preferably 0.00001 mol % or more, preferably 25 mol % or less, even more preferably 20 mol % or less, and particularly preferably 8 mol % or less, based on the total polymerized units constituting the fluoropolymer.
• fluoropolymers containing such polymerized units include: Fluororesins such as PTFE modified with fluoroalkyl vinyl ether (FAVE) and TFE/FAVE copolymer (PFA); partially fluorinated rubbers such as ethylene/HFP/FAVE rubbers, VdF/PMVE rubbers, VdF/PMVE/TFE rubbers, and VdF/PMVE/TFE/HFP rubbers; Perfluororubber; etc.
• Fluororesins such as PTFE modified with fluoroalkyl vinyl ether (FAVE) and TFE/FAVE copolymer (PFA); partially fluorinated rubbers such as ethylene/HFP/FAVE rubbers, VdF/PMVE rubbers, VdF/PMVE/TFE rubbers, and VdF/PMVE/TFE/HFP rubbers; Perfluororubber; etc.
• the fluoropolymer contains low molecular weight PTFE.
• Low molecular weight PTFE can generally be produced by polymerization employing polymerization conditions for producing low molecular weight PTFE, or by reducing the molecular weight of the high molecular weight PTFE obtained by polymerization using known methods (thermal decomposition, decomposition by radiation exposure, etc.).
• an aqueous dispersion containing low molecular weight PTFE can be prepared by polymerization employing polymerization conditions for producing low molecular weight PTFE.
• high molecular weight PTFE refers to PTFE that is non-melt processable and has fibrillating properties.
• low molecular weight PTFE refers to PTFE that is melt processable and does not have fibrillating properties.
• Non-melt processable means that the melt flow rate cannot be measured at temperatures above the crystallization melting point in accordance with ASTM D 1238 and D 2116.
• the presence or absence of fibrillation properties can be determined by paste extrusion, a typical method for molding high molecular weight PTFE powder, a powder made from TFE polymers.
• Paste extrusion is usually possible because high molecular weight PTFE has fibrillation properties. If the unsintered molded product obtained by paste extrusion has no substantial strength or elongation, for example if it breaks when pulled with an elongation of 0%, it can be considered not to have fibrillation properties.
• the high molecular weight PTFE preferably has a standard specific gravity (SSG) of 2.130 to 2.280.
• SSG standard specific gravity
• the standard specific gravity is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D4895 89.
• "high molecular weight” means that the standard specific gravity is within the above range.
• the low molecular weight PTFE has a melt viscosity of 1 ⁇ 10 2 to 7 ⁇ 10 5 Pa ⁇ s at 380° C.
• melt viscosity 1 ⁇ 10 2 to 7 ⁇ 10 5 Pa ⁇ s at 380° C.
• melt viscosity is within the above range.
• aqueous dispersion By polymerization of the fluoromonomer, an aqueous dispersion containing a fluoropolymer is obtained.
• the content of the fluoropolymer in the aqueous dispersion after polymerization is usually 8 to 50% by mass based on the aqueous dispersion.
• aqueous dispersions prepared by polymerizing fluoromonomers contain polymerization radicals represented by the general formula (1). These polymerization radicals are highly reactive and react with other compounds to produce by-products or to promote unintended reactions.
• General formula (1) R-(CF 2 -CF 2 ) n ⁇ (wherein R is a monovalent group, n is an integer of 1 or more, and ⁇ represents an unpaired electron).
• the above-mentioned polymerization radicals tend to be generated easily, particularly when tetrafluoroethylene is polymerized as a fluoromonomer in the presence of a chain transfer agent and a water-soluble radical polymerization initiator.
• the oxygen saturation of the aqueous dispersion can be increased.
• the oxygen saturation of the aqueous dispersion is preferably 53.5% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.
• the oxygen saturation of the aqueous dispersion may be 99% or less.
• oxygen saturation is the ratio of the actual amount of dissolved oxygen to the saturated amount of dissolved oxygen in water at 1 atmosphere. Oxygen saturation can be measured with an optical dissolved oxygen meter.
• R is a monovalent group.
• R is preferably COOH, OH, SO 3 H, CF 3 , CH 3 , or R 11 -R 12 - (wherein R 11 represents COOH, OH, SO 3 H, CF 3 , or CH 3 , and R 12 represents a chain formed by polymerization of tetrafluoroethylene and a modifying monomer).
• a method for blowing an oxygen-containing gas into an aqueous dispersion for example, a method (bubbling method) can be used in which an oxygen-containing gas is blown into the aqueous dispersion to generate bubbles and bring the aqueous dispersion into contact with the oxygen-containing gas.
• the flow rate of the gas is, for example, 1 to 30 L/min.
• oxygen-containing gases examples include oxygen gas and air.
• the oxygen content of the oxygen-containing gas may be 20 to 100% by volume.
• the temperature at which the aqueous dispersion is brought into contact with the oxygen-containing gas is preferably 5 to 99°C, more preferably 15°C or higher, and more preferably less than 35°C.
• the pressure when the aqueous dispersion is brought into contact with the oxygen-containing gas may be normal pressure.
• the time for contacting the aqueous dispersion with the oxygen-containing gas is preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, particularly preferably 30 minutes or more, and is preferably 48 hours or less, more preferably 24 hours or less, even more preferably 12 hours or less.
• a method for contacting the aqueous dispersion with an oxidizing agent for example, a method can be used in which the aqueous dispersion is contacted with the oxidizing agent by adding the oxidizing agent to the aqueous dispersion.
• Oxidizing agents include gaseous oxidizing agents such as ozone gas, fluorine gas, chlorine gas, bromine gas, and iodine gas; inorganic acids and inorganic acid salts such as nitric acid, nitric acid, sulfurous acid, sulfuric acid, persulfuric acid, hydrochloric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hydrofluoric acid, bromic acid, iodic acid, phosphoric acid, boric acid, chromic acid, dichromate, and permanganic acid; and peroxides such as hydrogen peroxide. Of these, hydrogen peroxide is the most preferable oxidizing agent.
• the amount of oxidizing agent to be brought into contact with the aqueous dispersion is preferably 1 to 500 ppm by mass, more preferably 3 ppm by mass or more, and more preferably 200 ppm by mass or less, relative to the mass of the aqueous dispersion.
• the temperature at which the aqueous dispersion is brought into contact with the oxidizing agent is preferably 5 to 99°C, more preferably 15°C or higher, and more preferably less than 35°C.
• the pressure when contacting the aqueous dispersion with the oxidizing agent may be normal pressure.
• the time for contacting the aqueous dispersion with the oxidizing agent is preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, particularly preferably 30 minutes or more, and is preferably 48 hours or less, more preferably 24 hours or less, even more preferably 12 hours or less.
• a method for contacting an aqueous dispersion with an alcohol for example, a method of adding alcohol to the aqueous dispersion can be used.
• the alcohol is preferably an alcohol having 1 to 10 carbon atoms, more preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol, and even more preferably at least one selected from the group consisting of methanol and ethanol.
• the amount of alcohol brought into contact with the aqueous dispersion is preferably 1 to 500 ppm by mass, more preferably 3 ppm by mass or more, and more preferably 200 ppm by mass or less, relative to the mass of the aqueous dispersion.
• the temperature at which the aqueous dispersion is brought into contact with the alcohol is preferably 5 to 99°C, more preferably 15°C or higher, and more preferably less than 35°C.
• the pressure when contacting the aqueous dispersion with the alcohol may be normal pressure.
• the time for contacting the aqueous dispersion with the alcohol is preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, particularly preferably 30 minutes or more, and is preferably 48 hours or less, more preferably 24 hours or less, even more preferably 12 hours or less.
• the above manufacturing method makes it possible to produce an aqueous fluoropolymer dispersion with a reduced content of polymerization radicals.
• the present disclosure also relates to an aqueous fluoropolymer dispersion with reduced content of polymerization radicals.That is, the aqueous fluoropolymer dispersion of the present disclosure has an oxygen saturation of 53.5% or more.
• the oxygen saturation of the aqueous dispersion is preferably 53.5% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.
• the oxygen saturation of the aqueous dispersion may be 99% or less.
• the fluoropolymer aqueous dispersion of the present disclosure contains a fluoropolymer and an aqueous medium, and preferably has a content of the polymerization radical represented by general formula (1) of 0 g -1 or less and a content of the oxidation radical represented by general formula (2) of 0.1 g -1 or more.
• the content of the oxidation radical may be 4.1 g -1 or more and may be 9.0 g -1 or less. Theoretically, the content of the polymerization radical will not fall below 0 g -1 , but a measured value below 0 g -1 may be obtained.
• the fluoropolymer aqueous dispersion may further contain the aqueous medium described above.
• the fluoropolymer content in the aqueous fluoropolymer dispersion is preferably 8 to 50% by mass, more preferably 15% by mass or more, and more preferably 40% by mass or less.
• the aqueous fluoropolymer dispersion may be diluted or concentrated.
• Concentration methods include phase separation concentration, electrical concentration, electrophoresis, ion exchanger, and membrane concentration.
• the phase separation concentration, ion exchanger, and membrane concentration methods can be carried out under conventionally known processing conditions, and are not particularly limited, but can be carried out by the methods described in International Publication No. 2004/050719, JP-A-2002-532583, and JP-A-55-120630.
• the aqueous fluoropolymer dispersion may further contain the above-mentioned fluorine-containing surfactant.
• the content of the fluorine-containing surfactant in the aqueous fluoropolymer dispersion may be 200 ppb by mass or more, 300 ppb by mass or more, or 400 ppb by mass or more, or 10% by mass or less, 1% by mass or less, or 0.5% by mass or less, based on the mass of the fluoropolymer.
• the fluorine-containing surfactant in the aqueous fluoropolymer dispersion may be removed from the aqueous dispersion by a known method such as a phase separation concentration method, an ion exchange method, or a membrane concentration method.
• aqueous fluoropolymer dispersion is substantially free of a fluorine-containing surfactant.
• substantially free of fluorine-containing surfactant means that the content of fluorine-containing surfactant in the aqueous fluoropolymer dispersion is 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, still more preferably 1 ppb by mass or less, and particularly preferably the fluorine-containing surfactant is below the detection limit as measured by liquid chromatography-mass spectrometry (LC/MS).
• LC/MS liquid chromatography-mass spectrometry
• the content of the fluorine-containing surfactant in the aqueous fluoropolymer dispersion can be measured by liquid chromatography-mass spectrometry (LC/MS/MS).
• LC/MS/MS liquid chromatography-mass spectrometry
• methanol is added to the aqueous fluoropolymer dispersion to perform extraction, and the resulting extract is analyzed by LC/MS/MS.
• treatment such as Soxhlet extraction or ultrasonic treatment may be performed.
• Molecular weight information is extracted from the obtained LC/MS/MS spectrum, and its agreement with the structural formula of a candidate fluorine-containing surfactant is confirmed.
• aqueous solutions containing the confirmed fluorine-containing surfactant at five or more different contents are prepared, and the aqueous solutions containing each content are subjected to LC/MS/MS analysis.
• the relationship between the content and the area relative to the content is plotted to draw a calibration curve.
• the area of the LC/MS/MS chromatogram of the fluorosurfactant in the extract can be converted into the content of the fluorosurfactant.
• the aqueous fluoropolymer dispersion disclosed herein has a reduced content of highly active polymerization radicals and a low content of impurities (by-products), making it suitable for a variety of applications.
• the aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer is preferably stabilized and further concentrated by adding a nonionic surfactant, and used in various applications as a composition with organic or inorganic fillers added depending on the purpose.
• the aqueous dispersion described above can be coated on a substrate made of metal or ceramic to form a coating surface that is non-adhesive and has a low coefficient of friction, and is excellent in gloss, smoothness, abrasion resistance, weather resistance, and heat resistance, making it suitable for painting rolls and cookware, impregnation processing of glass cloth, etc.
• An organosol can also be prepared from an aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer.
• the organosol can contain PTFE and an organic solvent, and examples of the organic solvent include ether-based solvents, ketone-based solvents, alcohol-based solvents, amide-based solvents, ester-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, and halogenated hydrocarbon-based solvents. N-methyl-2-pyrrolidone, dimethylacetamide, and the like can be suitably used.
• the organosol can be prepared, for example, by the method described in International Publication No. 2012/002038.
• the aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer is also preferably used as a processing aid.
• the aqueous dispersion can be mixed with a host polymer or the like to improve the melt strength of the host polymer during melt processing, and the mechanical strength, electrical properties, flame retardancy, drip prevention during combustion, and sliding properties of the resulting polymer.
• Aqueous fluoropolymer dispersions containing PTFE as a fluoropolymer are also preferably used as binders for batteries and for dust prevention purposes.
• Aqueous fluoropolymer dispersions containing PTFE as the fluoropolymer are also preferably used as processing aids after compounding with resins other than PTFE.
• Aqueous fluoropolymer dispersions are suitable as raw materials for PTFE, for example, as described in JP-A-11-49912, U.S. Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980. Processing aids using aqueous fluoropolymer dispersions are in no way inferior to the processing aids described in the above publications.
• an aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer with an aqueous dispersion of a melt-processable fluororesin and coagulate it to produce a co-coagulated powder.
• the co-coagulated powder is suitable as a processing aid.
• melt-processable fluororesin examples include FEP, PFA, TFE/fluoroalkyl allyl ether copolymer, ETFE, ethylene/TFE/HFP copolymer [EFEP], etc., with PFA, TFE/fluoroalkyl allyl ether copolymer, and FEP being preferred.
• the aqueous dispersion preferably contains the melt-processable fluororesin.
• the melt-processable fluororesin include FEP, PFA, TFE/fluoroalkyl allyl ether copolymer, ETFE, and EFEP.
• the aqueous dispersion containing the melt-processable fluororesin can be used as a paint.
• the melt-processable fluororesin can sufficiently fuse PTFE particles together, improving film-forming properties and imparting gloss to the resulting coating.
• the fluorine-free resin to which the co-coagulated powder is added may be in the form of a powder, pellets, or emulsion.
• the addition is preferably carried out while applying shear force by a known method such as extrusion kneading or roll kneading.
• an aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer as a dust suppressant treatment.
• the dust suppressant treatment can be used in a method of suppressing dust from a dust-generating substance by mixing the dust suppressant treatment with a dust-generating substance and subjecting the mixture to a compression-shear action at a temperature of 20 to 200°C to fibrillate the PTFE, for example, in the method of Patent No. 2827152, Patent No. 2538783, etc.
• the aqueous fluoropolymer dispersion can be suitably used in the dust suppressant treatment composition described in, for example, WO 2007/004250, and can also be suitably used in the dust suppressant treatment method described in WO 2007/000812.
• the above dust suppression treatment agent is suitable for use in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill disposal of incineration ash and hazardous substances, explosion prevention, cosmetics, and dust suppression treatment for sand for pet excretion, such as cat litter.
• the aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer is also preferably used as a raw material for obtaining PTFE fibers by the dispersion spinning method.
• the dispersion spinning method is a method in which the aqueous dispersion of PTFE and the aqueous dispersion of a matrix polymer are mixed, the mixture is extruded to form an intermediate fiber structure, and the intermediate fiber structure is fired to decompose the matrix polymer and sinter the PTFE particles to obtain PTFE fibers.
• a primer composition can be obtained by adding a nonionic surfactant to an aqueous fluoropolymer dispersion containing TFE/FAVE copolymer [PFA] or TFE/fluoroalkyl allyl ether copolymer as the fluoropolymer, and dissolving or dispersing polyethersulfone, polyamideimide and/or polyimide, and metal powder in an organic solvent as required.
• This primer composition can also be used in a method for coating a metal surface with a fluororesin, which comprises applying the primer composition to a metal surface, applying a fluoropolymer composition onto the primer layer thus formed, and baking the fluoropolymer composition layer together with the primer layer.
• a method for producing an aqueous fluoropolymer dispersion comprising the steps of: A fluoromonomer is polymerized in the presence of a fluorine-containing surfactant, a polymerization initiator and an aqueous medium to prepare an aqueous dispersion containing a fluoropolymer; There is provided a production method for obtaining an aqueous fluoropolymer dispersion by blowing an oxygen-containing gas into the aqueous dispersion, or by contacting the aqueous dispersion with an oxidizing agent, or by contacting the aqueous dispersion with an alcohol.
• ⁇ 2> According to a second aspect of the present disclosure, there is provided a process according to the first aspect, wherein the alcohol is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol. ⁇ 3> According to a third aspect of the present disclosure, there is provided a process according to the first or second aspect, wherein the oxidizing agent is hydrogen peroxide. ⁇ 4> According to a fourth aspect of the present disclosure, There is provided a production method according to any one of the first to third aspects, wherein the polymerization initiator is a water-soluble radical polymerization initiator.
• the fluoropolymer is selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene/fluoroalkyl vinyl ether copolymer, tetrafluoroethylene/fluoroalkyl allyl ether copolymer, tetrafluoroethylene/hexafluoropropylene copolymer, ethylene/tetrafluoroethylene copolymer, ethylene/tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotrifluoroethylene, chlorotrifluoroethylene/tetrafluoroethylene copolymer, ethylene/chlorotrifluoroethylene copolymer, polyvinyl fluoride, polyvinylidene fluoride, vinylidene fluoride/tetrafluoroethylene copolymer, fluoromonomer/vinyl ester copolymer, and general formula (
• the perfluoroalkyl group may contain etheric oxygen and a -SO 2 F group.
• n represents an integer of 0 to 3.
• the n Y 151 may be the same or different.
• Y 152 represents a fluorine atom, a chlorine atom or a -SO 2 F group.
• m represents an integer of 1 to 5.
• the m Y 152 may be the same or different.
• a 151 represents -SO 2 X 151 , -COZ 151 or -POZ 152 Z 153.
• X 151 represents F, Cl, Br, I, -OR 151 or -NR 152 R 153.
• Z 151 , Z 152 and Z 153 are the same or different and each represents -NR 154 R and R 155 or -OR 156.
• R 151 , R 152 , R 153 , R 154 , R 155 and R 156 are the same or different and represent H, ammonium, an alkali metal, an alkyl group which may contain a fluorine atom, an aryl group, or a sulfonyl-containing group.
• a sixth aspect of the present disclosure polymerizing a fluoromonomer in the presence of a chain transfer agent in addition to the fluorine-containing surfactant, the polymerization initiator, and the aqueous medium;
• the fluoromonomer contains at least tetrafluoroethylene
• the polymerization initiator is a persulfate
• the chain transfer agent is at least one selected from the group consisting of an alkane having 1 to 5 carbon atoms and an alcohol having 1 to 3 carbon atoms
• the fluoropolymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene/fluoroalkyl vinyl ether copolymers;
• aqueous dispersion By contacting the aqueous dispersion with hydrogen peroxide in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5 to 99° C. for 1 minute or more, or The aqueous dispersion is contacted with an alcohol having 1 to 10 carbon atoms in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5 to 99° C. for 1 minute or more, There is provided a production method according to any one of the first to fifth aspects for obtaining an aqueous dispersion having an oxygen saturation of 80% or more.
• An aqueous fluoropolymer dispersion that contains a fluoropolymer and an aqueous medium, the aqueous dispersion having an oxygen saturation of 53.5% or greater.
• an aqueous dispersion having a content of the polymerizable radical represented by general formula (1) of 0 g ⁇ 1 or less and a content of the oxidizing radical represented by general formula (2) of 0.1 g ⁇ 1 or more.
• an aqueous dispersion in which the fluoropolymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene/fluoroalkyl vinyl ether copolymers, and has an oxygen saturation of 80% or more.
• ⁇ Amount of Radicals in Aqueous Dispersion The contents of polymerization radicals and oxidation radicals in the aqueous dispersion were determined by electron spin resonance (ESR) method.
• Polymerization radical HOOC-(CF 2 -CF 2 ) n ⁇ (wherein n is an integer of 1 or more, ⁇ represents an unpaired electron).
• Oxidizing radical HOOC-(CF 2 -CF 2 ) n O-O. (wherein n is an integer of 1 or more, and . represents an unpaired electron.)
• Comparative Example 1 A polymerization reaction of TFE was carried out according to a method similar to Example 7 of WO 2009/020187 to obtain an aqueous PTFE dispersion.
• Example 1 A PTFE aqueous dispersion was obtained in the same manner as in Comparative Example 1. Thereafter, the autoclave was opened, and 14 kg of the obtained PTFE aqueous dispersion was transferred to another container, and air was blown in at a flow rate of 2 L/min for 6 minutes for bubbling.
• Example 2 The same procedure was followed as in Example 1, except that the bubbling time was changed to 10 minutes.
• Example 3 The same procedure was followed as in Example 1, except that the bubbling time was changed to 15 minutes.
• Example 4 The same procedure as in Example 1 was carried out except that the bubbling time was changed to 30 minutes.
• Example 5 The same procedure was followed as in Example 1, except that the bubbling time was changed to 60 minutes.
• Comparative Example 2 The same procedure as in Example 1 was repeated except that the bubbling gas was changed from air to nitrogen, the flow rate was changed to 5 L/min, and the time was changed to 60 minutes.
• Example 6 The same procedure as in Example 1 was carried out except that the bubbling flow rate was changed to 5 L/min and the time was changed to 6 minutes.
• Example 7 The same procedure was followed as in Example 6, except that the bubbling time was changed to 30 minutes.
• Example 8 The same procedure was followed as in Example 6, except that the bubbling time was changed to 60 minutes.
• Example 9 The same procedure was followed as in Example 6, except that the bubbling time was changed to 120 minutes.
• Example 10 PFA aqueous dispersion 1 was polymerized in the same manner as in Comparative Example 3. Thereafter, the autoclave was opened, and 4 kg of the obtained PTFE aqueous dispersion 1 was transferred to another container, and air was bubbled at a flow rate of 5 L/min for 120 minutes.
• Example 11 The PFA aqueous dispersion 2 was polymerized in the same manner as in Reference Example 4. Then, the autoclave was opened, and 4 kg of the obtained PTFE aqueous dispersion 1 was transferred to another container, and air was bubbled at a flow rate of 5 L/min for 120 minutes.
• Example 12 PFA aqueous dispersion 3 was polymerized in the same manner as in Comparative Example 5. Thereafter, the autoclave was opened, and 4 kg of the obtained PTFE aqueous dispersion 1 was transferred to another container, and air was bubbled at a flow rate of 5 L/min for 120 minutes.
• Example 13 The PTFE aqueous dispersion was polymerized in the same manner as in Comparative Example 1. Thereafter, the autoclave was opened, and 4 kg of the obtained PTFE aqueous dispersion 1 was transferred to another container, and the temperature in the tank was raised under stirring, and when the temperature in the tank reached 80°C, an aqueous solution in which 3.5 g of hydrogen peroxide [H 2 O 2 ] was dissolved in 10 ml of deionized water as an oxidizing agent was added, and the mixture was stirred for 10 minutes in an air atmosphere.
• H 2 O 2 hydrogen peroxide
• Example 14 The same procedure as in Example 13 was followed except that the amount of H2O2 added was 35.4 g .
• Example 15 The same procedure as in Example 13 was repeated, except that the aqueous solution of hydrogen peroxide was changed to 1.7 g of methanol [MeOH].
• Example 16 The same procedure was followed as in Example 15, except that the amount of MeOH added was 16.8 g.
• Example 17 The same procedure was followed as in Example 15, except that the amount of MeOH added was 168 g.
• Example 18 The same procedure was followed as in Example 15, except that the amount of MeOH added was 1680 g.
• FIG. 1 shows the first differential spectra (horizontal axis: g value (-), vertical axis: Int. [PTFE]/Int. [Mn 2+ ]/sample weight (g -1 )) of the aqueous dispersions obtained in Examples 6, 8, 13, and 14, and Comparative Example 1. From the results shown in FIG. 1, no triplets are observed in the first differential spectra of the aqueous dispersions obtained by the production method of the present disclosure, and only singlets appear. This result indicates that no polymerization radicals are present in the aqueous dispersions, and only oxidation radicals are present.

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