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
  • C08F2/00—Processes of polymerisation
  • C08F2/12—Polymerisation in non-solvents
  • C08F2/16—Aqueous medium
  • C08F2/22—Emulsion polymerisation
• • 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
• • 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
  • C08F259/00—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00
  • C08F259/08—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00 on to polymers containing fluorine
• • 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
• • 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 an aqueous dispersion, a method for producing an aqueous dispersion, and a method for producing a polymer-containing substrate.
• Polytetrafluoroethylene is used in various industrial fields due to its excellent heat resistance, chemical resistance, flame retardancy, weather resistance, and the like. Polytetrafluoroethylene is sometimes used in the form of an aqueous dispersion in which polytetrafluoroethylene is dispersed in an aqueous medium, for reasons such as ease of handling.
• Patent Document 1 discloses a method in which tetrafluoroethylene is polymerized in the presence of a fluoropolymer having anionic groups in its side chains and an aqueous medium to obtain an aqueous dispersion containing polytetrafluoroethylene, and then a surfactant is added to the obtained aqueous dispersion in order to improve the dispersion stability of the polytetrafluoroethylene.
• R represents an alkyl group having 8 to 18 carbon atoms
• L represents a polyoxyalkylene chain composed of oxyethylene groups having an average number of added moles of 5 to 20 and oxypropylene groups having an average number of added moles of 0 to 2.
• R S2 represents an alkyl group having 4 to 12 carbon atoms
• L S2 represents a polyoxyethylene chain composed of oxyethylene groups having an average added mole number of 5 to 20.
• [8] A method for producing the aqueous dispersion according to [7], comprising a step of contacting the aqueous dispersion with an ion exchange resin.
• a method for producing a polymer-containing substrate comprising contacting the aqueous dispersion according to any one of [1] to [6] with a substrate made of glass fiber to obtain a polymer-containing substrate.
• the present invention it is possible to provide an aqueous dispersion capable of forming a coating film with suppressed coloration.
• the present invention also provides a method for producing an aqueous dispersion and a polymer-containing substrate.
• a numerical range expressed using "to” means a range that includes the numerical values written 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 a single substance corresponding to the component, or two or more substances may be used in combination.
• the content of that 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 the monomer that is formed directly by polymerizing 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 charged substantially coincides with the actual content of each unit.
• NMR nuclear magnetic resonance spectroscopy
• the aqueous dispersion of the present invention (hereinafter also referred to as “the present aqueous dispersion”) comprises a first fluorine-containing polymer having not more than 1,000 ionic functional groups per 10 main chain carbon atoms of the polymer and having a glass transition temperature (hereinafter also referred to as "Tg") of 10°C or less and containing fluorine atoms; a second fluorine-containing polymer which is polytetrafluoroethylene (hereinafter also referred to as "PTFE”); a surfactant containing a nonionic surfactant; and an aqueous medium, and is substantially free of a fluorine-containing polymer which is different from the first fluorine-containing polymer and has ionic functional groups.
• Tg glass transition temperature
• PTFE polytetrafluoroethylene
• the coating film formed using this aqueous dispersion exhibits reduced coloration. Although the details of the reason for this are not clear, it is presumed that the following reasons are the main cause.
• a fluoropolymer having an ionic functional group is used, the fluoropolymer having an ionic functional group remains in the aqueous dispersion.
• the aqueous dispersion containing the residue is applied to a substrate, dried, and baked, the residue decomposes upon heating and becomes discolored. It is presumed that this problem is solved by the fact that the present aqueous dispersion is substantially free of a fluorine-containing polymer having an ionic functional group, and therefore coloration of the coating film formed using this dispersion is suppressed.
• the first fluorine-containing polymer has not more than 1,000 ionic functional groups per 10 main chain carbon atoms of the polymer, and preferably has at least one ionic functional group per 10 main chain carbon atoms of the polymer. When the amount of ionic functional groups is within this range, production stability during production of the second fluorine-containing polymer is improved.
• the number of ionic functional groups per 10 6 carbon atoms in the main chain of the polymer can be determined by a known method such as Fourier transform infrared spectroscopy (FT-IR).
• the ionic functional group may be a cationic functional group or an anionic functional group.
• ionic functional group examples include anionic functional groups such as a carboxylic acid group (—COO ⁇ ), a sulfonic acid group (—SO 3 ⁇ ), a sulfate group (—SO 4 2 ⁇ ), a phosphonic acid group (—PO 3 2 ⁇ ), and a phosphate group (—PO 4 3 ⁇ ).
• anionic functional groups such as a carboxylic acid group (—COO ⁇ ), a sulfonic acid group (—SO 3 ⁇ ), a sulfate group (—SO 4 2 ⁇ ), a phosphonic acid group (—PO 3 2 ⁇ ), and a phosphate group (—PO 4 3 ⁇ ).
• the first fluoropolymer has a Tg of 10°C or lower.
• the Tg of the first fluoropolymer is preferably 5°C or lower, more preferably 3°C or lower, and even more preferably 0°C or lower, from the viewpoint of efficiently adsorbing a monomer containing tetrafluoroethylene to be used in the production of the second fluoropolymer.
• the Tg of the first fluorine-containing polymer is preferably ⁇ 50° C. or higher, more preferably ⁇ 45° C. or higher, and even more preferably ⁇ 40° C. or higher, from the viewpoint of thermal stability after molding.
• the Tg of the first fluoropolymer is measured by differential scanning calorimetry (DSC), and the detailed measurement conditions are as described in the Examples section below.
• DSC differential scanning calorimetry
• a method for adjusting the Tg of the first fluoropolymer within the above range for example, a method of adjusting the type and amount of the monomer used in producing the first fluoropolymer can be mentioned.
• the first fluorine-containing polymer preferably has units based on a monomer having a vinyl group that may be substituted with a fluorine atom, and more preferably has units based on a monomer having a vinyl group substituted with a fluorine atom.
• the unit based on a monomer having a vinyl group substituted with a fluorine atom is preferably a unit based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE") (hereinafter also referred to as "PAVE unit”).
• PAVE perfluoro(alkyl vinyl ether)
• the PAVE is preferably a monomer represented by formula (1) from the viewpoint of excellent polymerization reactivity in producing the first fluoropolymer and enabling more efficient production of the second fluoropolymer.
• CF 2 CF-O-R f1
• R f1 represents 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 more excellent 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 perfluoro(methyl vinyl ether)
• PEVE perfluoro(ethyl vinyl ether)
• PPVE perfluoro(propyl vinyl ether)
• PMVE and PPVE are preferred, with PMVE being more preferred, as they allow for more efficient production of the second fluorinated polymer.
• the content of units based on a monomer having a vinyl group which may be substituted with a fluorine atom is preferably 20 to 60 mol%, more preferably 25 to 60 mol%, and even more preferably 30 to 55 mol%, based on the total units of the first fluorine-containing polymer.
• the first fluorine-containing polymer preferably has units based on tetrafluoroethylene (hereinafter also referred to as "TFE”) (hereinafter also referred to as “TFE units”), in view of better effects of the present invention.
• TFE tetrafluoroethylene
• the content of TFE units is preferably from 30 to 90 mol %, more preferably from 40 to 80 mol %, and even more preferably from 45 to 70 mol %, based on all units of the first fluorine-containing polymer.
• the first fluoropolymer preferably contains TFE units and PAVE units, since Tg can be easily adjusted to fall within the above range and the effects of the present invention are more excellent.
• the amount of PAVE units in the first fluorine-containing polymer relative to the total amount of TFE units and PAVE units is preferably 20 to 60 mol %, more preferably 25 to 60 mol %, and even more preferably 30 to 55 mol %, from the viewpoints that Tg can be easily adjusted to the above range and that the second fluorine-containing polymer can be produced more efficiently.
• the PAVE units are PMVE units, PEVE units or PPVE units, or when a mixture of two or more of these is used, the suitable amount used is the same.
• the first fluorine-containing polymer may contain units based on monomers other than the above-mentioned monomers, but in producing a second fluorine-containing polymer using the first fluorine-containing polymer, it is preferable that the first fluorine-containing polymer is substantially free of units based on other monomers, since this enables the second fluorine-containing polymer to be produced more efficiently.
• “Substantially free of units derived from other monomers” means that the content of units derived from other monomers is 0.01 mol % or less, more preferably 0 mol %, based on the total units of the first fluorine-containing polymer.
• the other monomer is preferably hexafluoropropylene.
• the content of the first fluoropolymer is preferably 0.10 to 2.0% by mass, more preferably 0.15 to 1.5% by mass, and even more preferably 0.2 to 0.8% by mass, relative to the total mass of the aqueous dispersion, in order to achieve better dispersion stability of the second fluoropolymer in the aqueous dispersion.
• the second fluoropolymer, PTFE may be a homopolymer of TFE or a modified PTFE.
• the second fluoropolymer is a fluoropolymer different from the first fluoropolymer.
• the first fluorine-containing polymer and the second fluorine-containing polymer may be copolymerized.
• the concentration of the fluorine-containing emulsifier is 100 ppm by mass or less, based on the total mass of the first fluorine-containing polymer in the first aqueous dispersion, and from the viewpoint of better effects of the present invention, it is preferably 50 ppm by mass or less, more preferably 25 ppm by mass, and even more preferably 5 ppm by mass or less.
• the lower limit may be 0 ppm by mass.
• the specific monomer may contain a monomer other than the fluorine-containing monomer (hereinafter also referred to as "other monomer”), but it is preferable that the specific monomer does not contain any other monomer.
• “Substantially free of other monomers” means that the amount of other monomers used is less than 0.0001% by mass, more preferably 0% by mass, based on the amount of the specific monomer used.
• Examples of the other monomer include the monomers exemplified above as the modified monomers that do not contain a fluorine atom. Two or more of the other monomers may be used in combination.
• the amount of polymerization initiator used is preferably 1 to 1,000 ppm, more preferably 5 to 750 ppm, and even more preferably 10 to 500 ppm, per 100 parts by mass of the specific monomer used.
• the specific monomer is added to the reaction system (i.e., polymerization reaction vessel) by a conventional method.
• the specific monomer may be added to the reaction system continuously or intermittently so that the polymerization pressure reaches a predetermined pressure.
• the specific monomer may be dissolved in an aqueous medium, and the resulting solution may be added to the reaction system continuously or intermittently.
• the polymerization initiator may be added to the reaction system all at once or in portions.
• the content of the second fluorine-containing polymer is preferably 10 to 40 mass%, more preferably 12 to 35 mass%, and even more preferably 15 to 30 mass%, relative to the total mass of the second aqueous dispersion.
• the content of PAVE units relative to the total of all units of the first fluoropolymer and the second fluoropolymer is preferably 0.1 to 5.0 mol %, more preferably 0.2 to 3.0 mol %, and even more preferably 0.3 to 2.5 mol %.
• the suitable content is the same whether the PAVE units are PMVE units, PEVE units or PPVE units, or whether a mixture of two or more of these is used.
• the PAVE unit is preferably contained in the first fluorine-containing polymer.
• Step 2 is a step of adding a surfactant including a nonionic surfactant to the second aqueous dispersion to obtain a specific aqueous dispersion.
• the surfactant used in step 2 includes a nonionic surfactant.
• the surfactant may further include a surfactant other than the nonionic surfactant (hereinafter also referred to as "another surfactant").
• the amount of surfactant used is preferably 0.10 to 19.8% by mass, more preferably 0.15 to 16.5% by mass, even more preferably 0.20 to 15.4% by mass, and particularly preferably 0.20 to 12.0% by mass, relative to the total mass of the first fluoropolymer and the second fluoropolymer contained in the second aqueous dispersion to be subjected to step 2.
• the amount of the nonionic surfactant used is preferably 85 to 99.9% by mass, more preferably 90 to 99% by mass, and even more preferably 92 to 98% by mass, relative to the amount of the surfactant used in step 2.
• the amount of the nonionic surfactant used is 85% by mass or more, the dispersion stability of the specific aqueous dispersion is superior.
• the amount of the nonionic surfactant used is 99.9% by mass or less, aggregation during subsequent steps can be suppressed, resulting in superior production stability.
• step 2 other surfactants may be further added, which can improve the concentration rate in step 4 described below.
• the type of other surfactant is not particularly limited, but anionic surfactants are preferred.
• the anionic surfactant is similar to the anionic surfactant that can be contained in the present aqueous dispersion described above, including preferred embodiments, and therefore a description thereof will be omitted.
• the amount of other surfactants (particularly anionic surfactants) used is preferably 100 to 3000 ppm by mass, more preferably 150 to 2500 ppm by mass, and even more preferably 150 to 2000 ppm by mass, relative to the total mass of the first fluoropolymer and the second fluoropolymer contained in the second aqueous dispersion to be subjected to step 2. If the amount of other surfactants (particularly anionic surfactants) used is 100 ppm by mass or more, the concentration rate in step 4, which will be described later, can be improved. If the amount of other surfactants (particularly anionic surfactants) used is 3000 ppm by mass or less, the formation of aggregates during concentration in step 4, which will be described later, can be further suppressed.
• a specific aqueous dispersion which contains a surfactant including the nonionic surfactant, and the first fluorine-containing polymer, the second fluorine-containing polymer and the second aqueous medium contained in the second aqueous dispersion.
• the specific aqueous dispersion may contain other components that can be contained in the present aqueous dispersion described above.
• the present production method preferably includes Step 3 of contacting the specific aqueous dispersion with an ion exchange resin to obtain a purified specific aqueous dispersion, which makes it possible to remove impurities such as components derived from the polymerization initiator and fluorine-containing polymers having ionic functional groups, thereby further suppressing coloration of the coating film.
• the ion exchange resin used in step 3 may be either an anion exchange resin or a cation exchange resin, but anion exchange resin is preferred because it is more effective at removing components that cause discoloration of the coating film.
• the amount of anion exchange resin used is preferably 1 to 100 parts by mass, and more preferably 1 to 50 parts by mass, per 100 parts by mass of the specific aqueous dispersion used.
• Specific examples of methods for contacting the specific aqueous dispersion with the anion exchange resin include a method of mixing the specific aqueous dispersion with the anion exchange resin, and a method of passing the specific aqueous dispersion through a column packed with the anion exchange resin.
• the temperature of the specific aqueous dispersion is preferably from 10 to 50°C, more preferably from 15 to 40°C.
• the contact time between the anion exchange resin and the specific aqueous dispersion is preferably from 10 to 360 minutes, more preferably from 10 to 240 minutes.
• the pH of the specific aqueous dispersion is not limited and may be less than 7 or may be 7 or greater.
• Step 3 preferably includes a treatment in which, after contacting the specific aqueous dispersion with an ion exchange resin, at least one of the nonionic surfactant and the anionic surfactant is added to the purified specific aqueous dispersion.
• the amount of the nonionic surfactant used in step 3 is preferably from 0.1 to 7.0 mass %, more preferably from 0.2 to 6.5 mass %, relative to the total mass of the first fluoropolymer and the second fluoropolymer contained in the specific aqueous dispersion obtained in step 2.
• the amount of the anionic surfactant used in step 3 is preferably from 200 to 3,000 mass %, more preferably from 250 to 2,500 mass %, based on the total mass of the first fluoropolymer and the second fluoropolymer contained in the specific aqueous dispersion obtained in step 2.
• the purified specific aqueous dispersion obtained in step 3 can be concentrated using known concentration methods, such as centrifugal sedimentation, electrophoresis, and phase separation.
• the amount of viscosity modifier used is preferably from 0 to 3.0 mass %, more preferably from 0.01 to 2.5 mass %, relative to the total mass of the first fluoropolymer and the second fluoropolymer contained in the purified specific aqueous dispersion obtained in step 3.
• a portion of the obtained aqueous dispersion C1-2 was adjusted to 20°C and stirred to aggregate the PTFE particles, thereby obtaining a PTFE powder.
• this PTFE powder was dried at 200°C.
• the obtained PTFE powder had an SSG of 2.20 and a melting point of 340°C. Furthermore, no by-product fluorine oligomers were confirmed in the obtained PTFE powder.
• Aqueous dispersion C4-2 was obtained using aqueous dispersion C1-2 according to the same procedures as for aqueous dispersions C2-1 to C4-1 in Example 1, except that nonionic surfactant (d) (Tergitol TMN100X, manufactured by DOW Corporation, C 12 H 25 —(OC 2 H 4 ) 10 —OH) was used instead of nonionic surfactant (a).
• nonionic surfactant (d) Tegitol TMN100X, manufactured by DOW Corporation, C 12 H 25 —(OC 2 H 4 ) 10 —OH
• PTFE aqueous dispersion C5-2 had a PTFE particle concentration (content) of 60.5% by mass, a surfactant concentration (total content) of 5.0% by mass relative to the mass of the PTFE particles, and a pH of 10.0.
• TFE was injected until the pressure in the reactor reached 1.86 MPaG, and a solution obtained by dissolving 3.4 g of disuccinic acid peroxide (concentration 80% by mass, remainder water) in 1 L of warm water was injected into the reactor to initiate polymerization. As the polymerization started, the pressure in the reactor decreased, so TFE was added to maintain the pressure constant. When 13 kg of TFE had been injected, the reactor was cooled, the polymerization reaction was terminated, and aqueous dispersion C1-3 was obtained.
• Aqueous dispersion C1-3 was a dispersion in which PTFE particles (average primary particle size 200 nm) containing fluoropolymer A1 and fluoropolymer A4 were dispersed in an aqueous medium, and had a solids concentration of 16.7 mass %.
• a portion of the obtained aqueous dispersion C1-3 was adjusted to 20°C and stirred to aggregate the PTFE particles, thereby obtaining a PTFE powder.
• This PTFE powder was then dried at 200°C.
• the obtained PTFE powder had an SSG of 2.14 and a melting point of 343°C. Furthermore, no by-product fluorine oligomers were confirmed in the obtained PTFE powder.
• Aqueous Dispersion C4-3 was obtained in the same manner as for Aqueous Dispersions C2-1 to C4-1 in Example 1, except that Aqueous Dispersion C1-3 was used.
• the nonionic surfactant (a) was added to the aqueous dispersion C4-5 so that the content of the nonionic surfactant (a) relative to the mass of the PTFE particles in this aqueous dispersion C4-3 was 14.0% by mass, and water and aqueous ammonia were also added to obtain a PTFE aqueous dispersion C5-3 (corresponding to the present aqueous dispersion).
• the PTFE aqueous dispersion C5-3 had a PTFE particle concentration (content) of 57.6% by mass, a surfactant concentration (total content) of 14.1% by mass relative to the mass of the PTFE particles, and a pH of 10.2.
• the average primary particle size of the PTFE particles in the PTFE aqueous dispersion C5-3 was the same as the average primary particle size of the PTFE particles in the above aqueous dispersion C1-3.
• the above-mentioned measurements and evaluations were carried out using the obtained PTFE aqueous dispersion C5-3. The results are shown in Table 1.
• the aqueous PTFE dispersion C5-3 did not substantially contain a fluorine-containing polymer having an ionic functional group.
• Example 4 An aqueous dispersion C4-3 was obtained according to the procedure of Example 3.
• Nonionic surfactant (a) was added to the aqueous dispersion C4-3 so that the content of nonionic surfactant (a) relative to the mass of the PTFE particles in this aqueous dispersion C4-3 was 10.0 mass%, and water and aqueous ammonia were also added to obtain a PTFE aqueous dispersion C5-4 (corresponding to this aqueous dispersion).
• the PTFE aqueous dispersion C5-4 had a PTFE particle concentration (content) of 59.0 mass%, a surfactant concentration (total content) of 10.1 mass% relative to the mass of the PTFE particles, and a pH of 10.2.
• the average primary particle size of the PTFE particles in the PTFE aqueous dispersion C5-4 was the same as the average primary particle size of the PTFE particles in the above aqueous dispersion C1-3.
• the above-mentioned measurements and evaluations were carried out using the obtained PTFE aqueous dispersion C5-4. The results are shown in Table 1.
• the aqueous PTFE dispersion C5-4 did not substantially contain a fluorine-containing polymer having an ionic functional group.
• Example 5 The PTFE aqueous dispersion produced according to Example 1 of WO2021/085470 was designated PTFE aqueous dispersion C5-5.
• PTFE aqueous dispersion C5-5 is a dispersion in which PTFE particles are dispersed in an aqueous medium, and does not contain a fluoropolymer corresponding to the above-mentioned first fluoropolymer.
• the above-mentioned measurements and evaluations were carried out using the resulting PTFE aqueous dispersion C5-5. The results are shown in Table 1.
• Aqueous dispersion C1-6 was a dispersion in which PTFE particles (average primary particle diameter 200 nm) were dispersed in an aqueous medium, and had a solids concentration of 12.1% by mass. A portion of the obtained aqueous dispersion C1-6 was adjusted to 20°C and stirred to aggregate the PTFE particles, thereby obtaining a PTFE powder. This PTFE powder was then dried at 200°C. The obtained PTFE powder had an SSG of 2.18 and a melting point of 337°C.
• aqueous PTFE dispersion C5-6 was obtained according to the same procedures as for aqueous dispersions C2-1 to C4-1 and aqueous PTFE dispersion C5-1 in Example 1.
• Aqueous PTFE dispersion C5-6 had a PTFE particle concentration (content) of 60.8% by mass, a surfactant concentration (total content) of 5.0% by mass relative to the mass of the PTFE particles, and a pH of 10.0.
• the average primary particle size of the PTFE particles in the PTFE aqueous dispersion C5-6 was the same as that of the aqueous dispersion C1-6.
• the aqueous PTFE dispersion C5-6 does not contain a fluoropolymer corresponding to the above-mentioned first fluoropolymer.
• the above-mentioned measurements and evaluations were carried out using the obtained PTFE aqueous dispersion C5-6. The results are shown in Table 1.
• Example 7 Ultrapure water (6.6 L), raw material liquid B2 (52 L), and paraffin wax (1.5 kg) were charged into a 100 L stainless steel pressure reactor equipped with a stirring blade and a baffle to obtain aqueous dispersion B1-7 (corresponding to the first aqueous dispersion).
• the content of fluoropolymer A5 was 0.6 mass% relative to the total mass of aqueous dispersion B1-7.
• the concentration of the fluorine-containing emulsifier was 0 ppm by mass relative to the total mass of fluoropolymer A1 in aqueous dispersion B1-7.
• the obtained aqueous dispersion B1-7 was heated to 65 ° C. while stirring at 95 rpm.
• TFE was injected until the pressure in the reactor reached 1.40 MPaG, and a solution obtained by dissolving 7.0 g of disuccinic acid peroxide (concentration 80 mass%, remainder water) in 1 L of warm water was injected into the reactor, and polymerization was initiated. As the pressure in the reactor decreased with the start of polymerization, TFE was added to maintain the pressure constant. When 15.8 kg of TFE had been injected, the reactor was cooled, the polymerization reaction was terminated, and aqueous dispersion C1-7 was obtained.
• the nonionic surfactant (a) was added to the aqueous dispersion C1-7 so that the content of the nonionic surfactant (a) relative to the mass of the PTFE particles in the aqueous dispersion C1-7 was 2.7 mass % to obtain an aqueous dispersion C2-7 (corresponding to a specific aqueous dispersion).
• the pH of the aqueous dispersion C2-7 was 3.0.
• SA10AOH anion exchange resin, manufactured by Lewatit, 623 g
• aqueous dispersion C3-7 (corresponding to the purified specific aqueous dispersion).
• the pH of the aqueous dispersion C3-7 was 3.7.
• the components were added to aqueous dispersion C3-7 so that the content of nonionic surfactant (a) was 10 mass%, the content of ammonium laurate was 1680 mass ppm, and the content of triethanolamine lauryl sulfate was 630 mass ppm relative to the mass of PTFE particles in aqueous dispersion C3-7, and then the mixture was concentrated by electrophoresis.
• aqueous dispersion C4-7 The supernatant was removed to obtain aqueous dispersion C4-7.
• concentration (content) of PTFE particles was 66.0 mass%
• concentration of nonionic surfactant (a) was 3.47 mass% relative to the mass of PTFE particles.
• a nonionic surfactant (a) was added to this aqueous dispersion C4-7 so that the content relative to the mass of the PTFE particles in this aqueous dispersion C4-7 was 10.0 mass%, and water and aqueous ammonia were also added to obtain a PTFE aqueous dispersion C5-7 (corresponding to the present aqueous dispersion).
• the average primary particle size of the PTFE particles in the PTFE aqueous dispersion C5-8 was the same as the average primary particle size of the PTFE particles in the above aqueous dispersion C1-7.
• the above-mentioned measurements and evaluations were carried out using the obtained PTFE aqueous dispersion C5-8.
• the results are shown in Table 1.
• the aqueous PTFE dispersion C5-8 did not substantially contain a fluorine-containing polymer having an ionic functional group.
• Raw material solution B3 was obtained according to the procedure for raw material solution B2, except that raw material solution A7 was diluted by a factor of 5. The content of fluoropolymer A7 was 1.1 mass % relative to the total mass of raw material solution B3.
• Example 9 Ultrapure water (26.6 L), raw material liquid B3 (32.1 L), and paraffin wax (1.5 kg) were charged into a 100 L stainless steel pressure reactor equipped with a stirring blade and a baffle to obtain aqueous dispersion B1-9 (corresponding to the first aqueous dispersion).
• the content of fluoropolymer A7 was 0.6 mass% relative to the total mass of aqueous dispersion B1-9.
• the concentration of the fluorine-containing emulsifier was 0 ppm by mass relative to the total mass of fluoropolymer A7 in aqueous dispersion B1-9.
• the obtained aqueous dispersion B1-9 was heated to 65 ° C. while stirring at 95 rpm.

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