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
  • C08F2/18—Suspension 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
  • C08F2/00—Processes of polymerisation
  • C08F2/44—Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
• • 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
  • C08F291/00—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00
  • C08F291/04—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00 on to halogen-containing macromolecules
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• • 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
  • C08F6/24—Treatment of polymer suspensions

Definitions

• the present invention relates to a method for producing a fluorine-containing polymer and a solid composition.
• Fluorine-containing polymers such as tetrafluoroethylene copolymers are used in various industrial fields because of their excellent heat resistance, chemical resistance, flame retardancy, weather resistance, and the like.
• Patent Document 1 discloses a method for emulsion polymerization of a fluorine-containing monomer in an aqueous medium in the presence of a radical initiator and a polyfunctional dispersant.
• the polyfunctional dispersant has a repeating unit derived from an ethylenically unsaturated functional group monomer containing -SO 3 Xa (Xa is H, an ammonium group, or a monovalent metal), and that anions and cations are removed using an ion exchange resin during the production of the polyfunctional dispersant.
• An object of the present invention is to provide a method for producing a fluoropolymer, which can produce a high molecular weight fluoropolymer.
• Another object of the present invention is to provide a fluorine-containing polymer having a high molecular weight equivalent to or higher than that obtained by using a conventional emulsifier, without using substantially any emulsifier.
• a method for producing a fluorine-containing polymer comprising polymerizing a monomer containing a fluorine-containing monomer in an aqueous dispersion containing a first fluorine-containing polymer and an aqueous medium to produce a second fluorine-containing polymer different from the first fluorine-containing polymer, comprising the steps of: a total concentration of cations contained in the aqueous dispersion is 2 ppm by mass or less based on the total mass of the aqueous medium in the aqueous dispersion before starting polymerization of the monomer; a total concentration of anions, excluding fluoride ions, sulfate ions and chloride ions, contained in the aqueous dispersion before initiation of polymerization of the monomers is 9 ppm by mass or less, based on the total mass of the aqueous medium in the
• [6] The method for producing a fluorine-containing polymer according to any one of [1] to [5], wherein the first fluorine-containing polymer contains units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether).
• [7] The method for producing a fluorine-containing polymer according to [6], wherein in the first fluorine-containing polymer, the units based on perfluoro(alkyl vinyl ether) account for 20 to 60 mol % of the units based on perfluoro(alkyl vinyl ether) relative to the total of the units based on tetrafluoroethylene and the units based on perfluoro(alkyl vinyl ether).
• a numerical range expressed using “to” means a range including the numerical values described before and after “to” as the upper and lower limits.
• the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages.
• the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.
• each component may be used alone or in combination of two or more substances corresponding to each component. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.
• unit refers collectively to an atomic group derived from one molecule of a monomer that is formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a part of the atomic group.
• a "unit based on a monomer” will also be simply referred to as a "unit”.
• the content (mass % or mol %) of each unit relative to all units contained in the polymer is determined by analyzing the polymer by solid-state nuclear magnetic resonance spectroscopy (NMR), and usually, the content of each unit calculated from the charged amount of each monomer substantially coincides with the actual content of each unit.
• NMR nuclear magnetic resonance spectroscopy
• the process for producing a fluoropolymer of the present invention is a process for producing a fluoropolymer which comprises polymerizing a monomer containing a fluorine-containing monomer (hereinafter also referred to as "specific monomer”) in an aqueous dispersion containing a first fluoropolymer and an aqueous medium (hereinafter also referred to as "aqueous dispersion X”) to produce a second fluoropolymer different from the first fluoropolymer.
• aqueous dispersion X aqueous dispersion containing containing a first fluoropolymer and an aqueous medium
• a second fluorine-containing polymer having a high molecular weight can be obtained.
• the details of the reason for this have not yet been made clear, it is presumed to be due to the following reasons. If the total concentration of cations in the aqueous dispersion X is high, the dispersibility of the first fluorine-containing polymer in the aqueous dispersion X becomes unstable, and the polymerization of the specific monomer in the aqueous dispersion X may be inhibited. In addition, since the other anions may function as chain transfer agents depending on their types, if the total concentration of the other anions is high, the polymerization of the specific monomer may be inhibited.
• the aqueous dispersion X used in the present production method has a sufficiently low total concentration of cations and other anions, so that it is presumed that the polymerization of the specific monomer proceeds well in the aqueous dispersion X to obtain a high molecular weight second fluorine-containing polymer.
• aqueous dispersion X containing a first fluorine-containing polymer and an aqueous medium is used.
• the aqueous dispersion X may contain a first fluorine-containing polymer. It is presumed that the first fluorine-containing polymer solubilizes the specific monomer by adsorbing and incorporating the specific monomer at the hydrophobic portion during polymerization of the specific monomer, and that the specific monomer is polymerized within the particles of the first fluorine-containing polymer by adding a polymerization initiator thereto. It is also presumed that the first fluorine-containing polymer contributes to the dispersion stabilization of various components in the aqueous medium.
• the first fluorine-containing polymer is preferably a polymer different from the second fluorine-containing polymer.
• anionic functional group examples include anionic functional groups such as a carboxylic acid group ( -COO- ) , a sulfonic acid group ( -SO3- ), a sulfate group ( -SO42- ), a phosphonic acid group ( -PO32- ) and a phosphoric acid group ( -PO43- ).
• the hydrophilic group is preferably a monovalent group.
• the fluorine-containing polymer having a hydrophilic group may have one or more hydrophilic groups.
• the fluorine-containing polymer having a hydrophilic group may have a hydrophilic group in a side chain or at an end.
• the hydrophilic group is a group derived from a polymerization initiator, or a hydrophilic group contained in a unit based on a monomer having a hydrophilic group.
• PAVE perfluoro(methyl vinyl ether) (hereinafter also referred to as “PMVE”), perfluoro(ethyl vinyl ether) (hereinafter also referred to as “PEVE”), and perfluoro(propyl vinyl ether) (hereinafter also referred to as “PPVE”).
• PMVE or PPVE are preferred, with PMVE being more preferred, in that the second fluorine-containing polymer can be produced more efficiently.
• the total concentration of cations relative to the total mass of the aqueous medium in aqueous dispersion X is calculated from the total area of the peaks of cations detected when aqueous dispersion X or a raw material liquid (or a purified raw material liquid) described below used in the production of aqueous dispersion X is measured by ion chromatography, using a calibration curve showing the relationship between the peak area and the amount of ammonium ions. Details of the measurement method will be described in the Examples section below.
• the fluoride ions, sulfate ions and chloride ions are derived, for example, from the polymerization initiator used in producing the first fluoropolymer, and may be contained in the aqueous dispersion X containing the first fluoropolymer.
• the total concentration of the specific anion contained in the aqueous dispersion X is, from the viewpoint of better effects of the present invention, preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less, and even more preferably 1 ppm by mass or less, based on the total mass of the aqueous medium in the aqueous dispersion X.
• the lower limit is 0 ppm by mass.
• the metal element may be contained in the first fluoropolymer-containing aqueous dispersion X, for example, as originating from a polymerization initiator used in producing the first fluoropolymer.
• Specific examples of the metal element include manganese, iron, cobalt, nickel, copper, zinc, cerium, silver, and chromium.
• the total concentration of metal elements contained in the aqueous dispersion X is 2 ppm by mass or less relative to the total mass of the aqueous medium in the aqueous dispersion X, and from the viewpoint of obtaining a fluoropolymer of higher molecular weight, it is more preferably 1 ppm by mass or less.
• the lower limit may be 0 ppm by mass.
• a method for adjusting the total concentration of metal elements contained in the aqueous dispersion X to the above value there is a method in which a cation exchange resin is used during the production of the aqueous dispersion X.
• the total concentration of metal elements contained in the aqueous dispersion X is measured by ICP emission spectrometry of the aqueous dispersion X or the raw material liquid (or purified raw material liquid) described below used in the production of the aqueous dispersion X. Details of the measurement method will be described in detail in the Examples section described below.
• the aqueous dispersion X used in the present production method contains an aqueous medium.
• the aqueous medium contained in the aqueous dispersion X may be the polymerization solvent used in the production method of the aqueous dispersion X described below.
• Examples of the aqueous medium contained in the aqueous dispersion X include water and a mixed solvent of water and a water-soluble organic solvent. Specific examples of the water-soluble organic solvent include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.
• the content of the aqueous medium is preferably from 60 to 99.9 mass%, more preferably from 80 to 99.9 mass%, and even more preferably from 90 to 99.9 mass%, based on the total mass of the aqueous dispersion X.
• chain transfer agents include ethyl acetate, methanol, ethanol, t-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane.
• the fluorine-containing emulsifier means an emulsifier in which the hydrophobic moiety contains a fluorine atom among the hydrophilic moiety and the hydrophobic moiety of the emulsifier.
• Specific examples of the fluorine-containing emulsifier include fluorine-containing alkanoates and fluorine-containing ether carboxylic acid compounds.
• Specific examples of emulsifiers other than fluorine-based emulsifiers include sodium lauryl sulfate, Pelex SS-H manufactured by Kao Chemical Co., Ltd., and Newcol 1305-SN manufactured by Nippon Nyukazai Co., Ltd.
• the content of the chain transfer agent is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the aqueous medium.
• the amount of the chain transfer agent used is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the specific monomer described below.
• the aqueous dispersion X contains an emulsifier other than a fluorine-based emulsifier
• the content of the emulsifier other than a fluorine-based emulsifier is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the aqueous medium.
• the concentration of the fluorine-containing emulsifier is, from the viewpoint of better effects of the present invention, preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, still more preferably 25 ppm by mass or less, particularly preferably 5 ppm by mass or less, relative to the total mass of the first fluorine-containing polymer in the aqueous dispersion X.
• the lower limit 0 ppm by mass may be mentioned.
• An example of the method for adjusting the concentration of the fluorine-containing emulsifier within the above range is a method for producing the aqueous dispersion X without using a fluorine-containing emulsifier.
• the method includes a method for producing the first fluorine-containing polymer without using a fluorine-containing emulsifier during polymerization.
• One example of the method for producing the aqueous dispersion X used in the present production method is a method in which a monomer (preferably a monomer mixture containing TFE and PAVE) is polymerized in an aqueous medium in the presence of a polymerization initiator and in the absence of an emulsifier to obtain a raw material liquid containing the aqueous medium and the first fluorine-containing polymer.
• the first fluoropolymer contained in the raw material liquid is preferably dispersed in the form of particles in the aqueous medium.
• the raw material liquid thus obtained may be used as it is as the above-mentioned aqueous dispersion X, or may further include another aqueous medium and use the resulting mixture as the above-mentioned aqueous dispersion X.
• the first fluoropolymer may be dispersed in another aqueous medium by solvent substitution and used as the above-mentioned aqueous dispersion X.
• the above-mentioned other components may be added to the raw material liquid, and this may be used as the aqueous dispersion X.
• the polymerization initiator used for polymerization of the first fluorine-containing polymer is preferably a water-soluble polymerization initiator, more preferably a persulfate such as ammonium persulfate, sodium persulfate or potassium persulfate, or an organic polymerization initiator such as disuccinic acid peroxide or azobisisobutylamidine dihydrochloride, further preferably a persulfate, and particularly preferably ammonium persulfate.
• Water-soluble oxidation-reduction catalysts which will be described later, are also preferred.
• the aqueous medium used in the polymerization of the first fluorine-containing polymer includes water and a mixed solvent of water and a water-soluble organic solvent. Specific examples of the water-soluble organic solvent are as described above.
• the content of the first fluorinated polymer in the raw material liquid is preferably from 0.01 to 30 mass %, more preferably from 0.01 to 10 mass %, and even more preferably from 0.01 to 1 mass %, based on the total mass of the aqueous medium in the raw material liquid.
• the content of the aqueous medium in the liquid raw material is preferably 60 to 99.9% by mass, more preferably 80 to 99.9% by mass, and even more preferably 98 to 99.9% by mass, based on the total mass of the liquid raw material.
• the method for producing the aqueous dispersion X used in the present production method preferably includes a step of contacting the obtained raw material liquid with an anion exchange resin after obtaining the raw material liquid. By carrying out this step, the raw material liquid is purified to obtain a purified raw material liquid. By going through this step, it becomes easy to adjust the total concentration of fluoride ions, sulfate ions and chloride ions, and the total concentration of other anions in the aqueous dispersion X used in the present production method to fall within the above-mentioned ranges.
• the anion exchange resin is preferably an anion exchange resin having low decomposition property against peroxides (e.g., the polymerization initiator used in the production of the first fluoropolymer).
• an anion exchange resin having low decomposition property against peroxides it is considered that the incorporation of other anions originating from the anion exchange resin into the aqueous dispersion X can be further suppressed.
• the anion exchange resin commercially available products can be used.
• anion exchange resins that are less decomposable to peroxides include Amberlite (registered trademark) HPR4200 Cl (manufactured by DuPont) and Diaion (registered trademark) SA10AOH (manufactured by Mitsubishi Chemical Corporation).
• the ion exchange group of the anion exchange resin is preferably a trialkylammonium group, since this provides a better effect of the present invention.
• the amount of anion exchange resin used is preferably 0.1 to 20 parts by mass, and more preferably 0.2 to 10 parts by mass, per 100 parts by mass of the raw material liquid used.
• the method for contacting the raw material liquid with the anion exchange resin include a method of mixing the raw material liquid with the anion exchange resin, and a method of passing the raw material liquid through a column packed with the anion exchange resin.
• the temperature of the raw material liquid is preferably from 0 to 80°C, more preferably from 10 to 50°C.
• the contact time between the anion exchange resin and the raw material liquid is preferably from 10 to 120 minutes, more preferably from 30 to 90 minutes.
• the passing rate is preferably 10 to 60 BV/h, more preferably 15 to 40 BV/h.
• the method for producing the aqueous dispersion X used in this production method preferably includes a step of contacting the obtained raw material liquid with a cation exchange resin after obtaining the raw material liquid. This step makes it easy to adjust the total concentration of cations in the aqueous dispersion X used in this production method to the above-mentioned range.
• the ion exchange group of the cation exchange resin is preferably a sulfonic acid group, since this makes it easier to adjust the total cation concentration to the above-mentioned range.
• a commercially available product can be used, and an example thereof is Dowex Monosphere 650C manufactured by Dupont.
• the amount of cation exchange resin used is preferably 0.05 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the raw material liquid used.
• the method for contacting the raw material liquid with the cation exchange resin are similar to the above-mentioned method for contacting the raw material liquid with the anion exchange resin.
• the temperature of the raw material liquid is preferably from 0 to 80°C, more preferably from 10 to 50°C.
• the contact time between the cation exchange resin and the raw material liquid is preferably from 10 to 120 minutes, more preferably from 30 to 90 minutes.
• the passing rate is preferably 10 to 60 BV/h, more preferably 15 to 40 BV/h.
• the method for producing the aqueous dispersion X used in the present production method preferably includes a heating step of heating the obtained raw material liquid after obtaining the raw material liquid. This deactivates the polymerization initiator present in the raw material liquid, so that the polymerization of the second fluorine-containing polymer is less affected by the polymerization initiator used in the polymerization of the first fluorine-containing polymer. As a result, the second fluorine-containing polymer having a high molecular weight is easily obtained.
• the heating temperature in the heating step is preferably from 70 to 100° C., more preferably from 80 to 98° C., and even more preferably from 85 to 95° C., from the viewpoint of further promoting the deactivation of the polymerization initiator in the aqueous medium.
• the method for producing the aqueous dispersion X used in the present production method may include a step of diluting the raw material liquid or the purified raw material liquid with an aqueous medium (e.g., water). In this step, other components such as wax may be added together with the aqueous medium.
• an aqueous medium e.g., water
• the present production method uses a specific monomer.
• the specific monomer includes a fluorine-containing monomer.
• Specific examples of the fluorine-containing monomer include TFE, chlorotrifluoroethylene (hereinafter also referred to as "CTFE”), vinylidene fluoride (hereinafter also referred to as "VdF”), fluoroalkylethylene (hereinafter also referred to as "FAE”), PAVE, and hexafluoropropylene. Two or more kinds of the fluorine-containing monomers may be used in combination.
• the PAVE is the same as the PAVE in the above-mentioned first fluoropolymer, and the preferred embodiments are also the same.
• the fluorine-containing monomer preferably contains at least one selected from the group consisting of TFE, CTFE and VdF, more preferably contains TFE, and more preferably is TFE.
• the amount of the fluorine-containing monomer used is preferably from 97 to 100% by mass, more preferably from 98 to 100% by mass, and even more preferably from 99 to 100% by mass, based on the amount of the specific monomer used.
• the amount of the fluorine-containing monomer used may be 10.0 to 100.0 mol % based on the amount of the specific monomer used, and in this case, it is more preferably 30.0 to 70.0 mol %, and further preferably 40.0 to 60.0 mol %.
• the amount of the fluorine-containing monomer used may be 90.0 to 99.9 mol % based on the amount of the specific monomer used, and when importance is attached to melt moldability, it is preferably 95.0 to 99.0 mol %.
• the specific monomer may contain a monomer other than the above-mentioned monomers (hereinafter, also referred to as "other monomers").
• the other monomer include ethylene, propylene, vinyl chloride, and vinylidene chloride, with ethylene being preferred.
• Two or more of the other monomers may be used in combination.
• the amount of the other monomer used is preferably 10.0 to 70.0 mol %, more preferably 20.0 to 60.0 mol %, and even more preferably 30.0 to 50.0 mol %, based on the amount of the specific monomer used.
• the amount of the specific monomer used is preferably 1 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 1 to 30 parts by mass, relative to 100 parts by mass of the aqueous medium contained in the aqueous dispersion X.
• the specific monomer is preferably polymerized in the presence of a polymerization initiator.
• a polymerization initiator an oil-soluble radical initiator, a water-soluble radical initiator, or a water-soluble oxidation-reduction catalyst is preferable.
• oil-soluble radical initiators include oil-soluble organic peroxides such as tert-butyl peroxypivalate (hereinafter also referred to as "PBPV”) and diisopropyl peroxydicarbonate (hereinafter also referred to as "IPP").
• water-soluble radical initiator examples include persulfates such as ammonium persulfate and potassium persulfate, water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide (hereinafter also referred to as "TBHP").
• persulfates such as ammonium persulfate and potassium persulfate
• water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide (hereinafter also referred to as "TBHP").
• components other than those described above may be further used.
• a specific example of the other components is a reducing agent.
• the amount of the other components used is preferably 1 to 2000 ppm by mass based on 100 parts by mass of the specific monomer used.
• the second fluorine-containing polymer obtained by the present production method contains units based on a fluorine-containing monomer, preferably contains units based on TFE (hereinafter also referred to as "TFE units”), and is more preferably a homopolymer of TFE (polytetrafluoroethylene, hereinafter also referred to as "PTFE").
• TFE units units based on TFE
• PTFE polytetrafluoroethylene
• the content of units based on a fluorine-containing monomer is preferably 99.0 to 100.0 mass%, more preferably 99.5 to 100.0 mass%, and even more preferably 99.9 to 100.0 mass%, based on the total units of the second fluorine-containing polymer.
• each component may be added all at once or in portions, and the order in which each component is added is not particularly limited.
• the specific monomer can be 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 becomes a predetermined pressure.
• the specific monomer may be dissolved in an aqueous medium, and the obtained 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 polymerization temperature is preferably from 10 to 95°C, more preferably from 15 to 90°C.
• the polymerization pressure is preferably from 0.5 to 4.0 MPaG, more preferably from 0.6 to 3.5 MPaG.
• the polymerization time is preferably from 90 to 1,000 minutes, more preferably from 90 to 700 minutes.
• the second fluorine-containing polymer can be produced using an aqueous medium having a small environmental load and without requiring an emulsifier. Therefore, the polymerization of the specific monomer is preferably carried out under conditions substantially in the absence of an emulsifier.
• the emulsifier may be the above-mentioned fluorine-based emulsifier or an emulsifier other than the fluorine-based emulsifier.
• the condition substantially free of emulsifier means an environment in which the content of the emulsifier is 0.03 ppm by mass or less, preferably 0.02 ppm by mass or less, and more preferably 0 ppm by mass, relative to the total mass of the aqueous medium contained in the aqueous dispersion X.
• the specific monomer polymerizes within the particles of the first fluoropolymer during polymerization of the specific monomer, and therefore it is believed that in this production method, particles containing the first fluoropolymer and the second fluoropolymer are produced. That is, it is presumed that according to this production method, the second fluoropolymer is obtained in the form of particles containing the first fluoropolymer and the second fluoropolymer. In this case, the production method produces a second aqueous dispersion in which particles containing the first fluoropolymer and the second fluoropolymer are dispersed in the aqueous medium.
• the second aqueous dispersion contains an aqueous medium and the second fluoropolymer obtained by the present production process, and may further contain the first fluoropolymer separately from the second fluoropolymer.
• the aqueous medium is the same as the specific examples of the aqueous medium used in the production of the second fluorine-containing polymer described above.
• the content of the aqueous medium is preferably from 50 to 99 mass%, more preferably from 60 to 99 mass%, and even more preferably from 70 to 99 mass%, based on the total mass of the aqueous dispersion, from the viewpoint of dispersion stability of the particles containing the second fluorinated polymer.
• the present aqueous dispersion may contain a first fluorine-containing polymer.
• the first fluorine-containing polymer is the same as the first fluorine-containing polymer in the above-mentioned present production method, and preferred embodiments are also the same.
• the content of the first fluoropolymer is preferably from 0.01 to 10.0 mass%, more preferably from 0.01 to 5.0 mass%, and even more preferably from 0.01 to 1.0 mass%, based on the total mass of the present aqueous dispersion.
• the second fluorine-containing polymer is the same as the second fluorine-containing polymer in the above-mentioned present production method, and preferred embodiments are also the same.
• the content of the second fluorine-containing polymer is preferably from 5 to 50 mass %, more preferably from 8 to 40 mass %, and even more preferably from 10 to 35 mass %, based on the total mass of the aqueous dispersion.
• the total content of the first fluoropolymer and the second fluoropolymer is preferably 5 to 50 mass%, more preferably 8 to 40 mass%, and even more preferably 10 to 35 mass%, based on the total mass of the aqueous dispersion.
• the first fluoropolymer and the second fluoropolymer may be present separately in the aqueous dispersion, but it is preferable that they are present in the form of particles containing the first fluoropolymer and the second fluoropolymer.
• the average particle size of the particles is preferably 500 ⁇ m or less, more preferably 450 ⁇ m or less, and even more preferably 400 ⁇ m or less, from the viewpoint of dispersion stability.
• the average particle size of the particles is preferably 50 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more, from the viewpoint of agglomeration.
• the average particle size of the particles is determined by measuring the particle size distribution by a laser diffraction/scattering method, calculating a cumulative curve with the total volume of the particle group set as 100%, and determining the particle size at the point on the cumulative curve where the cumulative volume is 50%.
• the second aqueous dispersion preferably does not substantially contain an emulsifier.
• the emulsifier include the above-mentioned fluorine-based emulsifiers and emulsifiers other than fluorine-based emulsifiers.
• the term "substantially free of emulsifier" used in the present aqueous dispersion means that the content of emulsifier is 0.03 ppm by mass or less, preferably 0.02 ppm by mass or less, and more preferably 0 ppm by mass, based on the total mass of the present aqueous dispersion. 0 ppm by mass means that no emulsifier is used.
• the total concentration of cations contained in the second aqueous dispersion is 2 ppm by mass or less, and from the viewpoint of obtaining a fluoropolymer having a higher molecular weight, preferably 1 ppm by mass or less, more preferably 0.1 ppm by mass or less, based on the total mass of the aqueous medium in the aqueous dispersion.
• the lower limit is 0 ppm by mass.
• One example of a method for adjusting the total concentration of cations contained in the aqueous dispersion to the above value is to produce the dispersion using an aqueous dispersion X having a cation concentration in the preferred range.
• the total concentration of cations contained in the aqueous dispersion is calculated from the total area of the peaks of cations detected when the fluoropolymer in the aqueous dispersion is precipitated and the supernatant is measured by ion chromatography, using a calibration curve showing the relationship between the peak area and the amount of ammonium ions. Details of the measurement method will be described in the Examples section below.
• the present aqueous dispersion does not require an emulsifier, it is easy to make it into a dispersion in an organic solvent such as N-methylpyrrolidone or acetone by solvent substitution.
• the aqueous dispersion of the present invention can be mixed with an organic solvent and dehydrated using evaporation or anhydrous sodium sulfate or the like to give a dispersion in the organic solvent.
• the second aqueous dispersion stably disperses the fluoropolymer even without the need for an emulsifier. This makes it suitable for use in coating applications, as a binder, etc.
• powders of the first fluoropolymer and the second fluoropolymer can be obtained by agglomerating the first fluoropolymer and the second fluoropolymer (preferably particles containing the first fluoropolymer and the second fluoropolymer) from the second aqueous dispersion.
• Flocculation methods include, but are not limited to, mechanical flocculation, freeze flocculation, acid flocculation, base flocculation, and flocculation using a coagulant.
• mechanical coagulation is a method in which the first fluorine-containing polymer and the second fluorine-containing polymer are diluted with water so that the concentration of the first fluorine-containing polymer and the second fluorine-containing polymer in the aqueous dispersion is 8 to 20% by mass, and then a shear force is applied by vigorous stirring or the like to coagulate the primary particles of the first fluorine-containing polymer and the second fluorine-containing polymer.
• the pH of the second aqueous dispersion may be adjusted, and a coagulation aid such as an electrolyte or a water-soluble organic solvent may be added.
• pH adjusters include sodium carbonate and sodium bicarbonate.
• the coagulation may also be carried out in the presence of one or more compounds selected from the group consisting of ammonia, ammonium salts, and urea.
• electrolytes include inorganic salts such as potassium nitrate, sodium nitrate, sodium carbonate, and sodium bicarbonate.
• organic solvents include alcohols and acetone. In the case of freeze aggregation, the aggregation temperature is preferably ⁇ 20 to 0° C.
• the aggregation time is preferably 1 hour or more, more preferably 2 hours or more.
• acid coagulation a method of adding an acid-containing solution to the aqueous dispersion is preferred.
• the acid to be added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, hydrofluoric acid, etc., and hydrochloric acid is preferred.
• the concentration of the acid in the acid-containing solution is preferably 0.1 to 50 mass%, more preferably 1 to 30 mass%, and even more preferably 1 to 10 mass%.
• a preferred method for base coagulation is to add a solution containing a base to the aqueous dispersion.
• Examples of the base to be added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, and sodium hydroxide is preferred.
• the concentration of the base in the solution containing the base is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.
• a known coagulant can be used.
• Known coagulants include aluminum salts, calcium salts, and magnesium salts.
• Specific examples include aluminum sulfate, alum represented by the general formula M'Al( SO4 ) 2.12H2O (wherein M' is a monovalent cation other than lithium), calcium nitrate, and magnesium sulfate.
• Alum is preferred, and potassium alum, where M is potassium, is more preferred.
• As the flocculation method mechanical flocculation or base flocculation is preferred since flocculation is particularly likely to proceed.
• the solid composition of the present invention (hereinafter also referred to as “the present solid composition”) contains a second fluorine-containing polymer, and may further contain a first fluorine-containing polymer.
• a solid composition means a composition having a solid content of 99% by mass or more.
• the solid composition can be obtained from the second aqueous dispersion described above. Specifically, it is preferably obtained by an aggregation method using the present aqueous dispersion described above. Since the preferred embodiments of the present solid composition are the same as the preferred embodiments of the first fluorine-containing polymer and the second fluorine-containing polymer contained in the present aqueous dispersion described above, the description thereof will be omitted.
• the present solid composition contains a first fluoropolymer
• the first fluoropolymer and the second fluoropolymer may be present separately in the present solid composition, but it is preferable that they are present in the form of particles containing the first fluoropolymer and the above-mentioned second fluoropolymer.
• the content of the first fluorine-containing polymer is preferably from 0.01 to 50 mass%, more preferably from 0.1 to 30 mass%, and even more preferably from 0.3 to 25 mass%, relative to the total mass of the present solid composition.
• the content of the second fluorine-containing polymer is preferably from 50 to 100 mass %, more preferably from 70 to 100 mass %, and even more preferably from 75 to 100 mass %, based on the total mass of the present solid composition.
• the total content of the first fluorine-containing polymer and the second fluorine-containing polymer is preferably from 98 to 100 mass%, more preferably from 99 to 100 mass%, based on the total mass of the present solid composition.
• the cation content in the present solid composition is 2 ppm by mass or less based on the total mass of the solid composition, and is more preferably 1 ppm by mass or less in terms of obtaining a higher molecular weight fluoropolymer.
• the lower limit can be 0 ppm by mass.
• a method for making the total concentration of cations in the solid composition to the above value it can be produced using an aqueous dispersion X having a cation concentration in a suitable range.
• the total concentration of cations contained in the solid composition is calculated from the total area of the peaks of the detected cations when the extract of the solid composition is measured by ion chromatography, using a calibration curve showing the relationship between the peak area and the amount of ammonium ions.
• the extract is obtained by adding water to the solid composition, subjecting it to ultrasonic treatment, centrifuging it to precipitate the fluorine-containing polymer, and extracting the supernatant. The details of the measurement method will be described in detail in the Examples section below.
• the total content of the metal elements contained in the present solid composition is 2 ppm by mass or less based on the total mass of the solid composition, and is more preferably 1 ppm by mass or less in terms of obtaining a higher molecular weight fluoropolymer.
• the lower limit can be 0 ppm by mass.
• a method for making the total concentration of the metal elements contained in the solid composition the above value it can be produced using an aqueous dispersion X in which the total content of the metal elements is in a suitable range.
• the total content of metal elements contained in the solid composition can be obtained by ashing the solid composition, extracting it with an aqueous sulfuric acid solution, and measuring the extract by ICP-MS. The details of the measurement method will be described in the Examples section below.
• the present solid composition obtained by aggregating the present aqueous dispersion is heated to 380°C at 10°C/min in an air atmosphere using a differential scanning calorimeter in a state that has no history of being heated to a temperature of 300°C or higher, and when the length measured from the largest endothermic peak present at 340°C or higher on a differential thermal analysis curve toward the baseline is taken as endothermic peak height A (hereinafter also referred to as "A") and the length measured from a point on the baseline 10°C lower than the intersection point measured from the maximum point toward the baseline to the differential thermal analysis curve is taken as endothermic peak height B (hereinafter also referred to as "B"), the DSC endothermic peak height ratio B/A is preferably 0.740 or less, and more preferably 0.700 or less, and even more preferably 0.500 or less, since this results in a fluoropolymer with a higher molecular weight.
• the DSC endothermic peak ratio is an index corresponding to the molecular weight of the fluoropolymer, and the smaller the value, the higher the ratio of the polymer with high crystallinity having a high melting point, i.e., the larger the molecular weight of the fluoropolymer. Also, when there is no peak at 340° C. or higher, it can be said that the molecular weight of the fluoropolymer is small.
• Examples 1-1, 2-1, and 2-2 are working examples, while Examples 1-2, 2-3, and 2-4 are comparative examples. However, the present invention is not limited to these examples.
• Tg ⁇ Glass transition temperature (Tg)> Tg was measured using a NEXTA DSC600 manufactured by Hitachi High-Tech Corporation. Specifically, 5 mg of a sample for measurement was weighed out and placed in an aluminum sample pan, and the sample was heated to 100°C at a heating rate of 10°C/min under a nitrogen atmosphere. It was then cooled to -60°C at a rate of 10°C/min. When the predetermined temperature was reached, the temperature was raised again to 100°C at 10°C/min. Tg was estimated from the inflection point confirmed in this second heating operation.
• the concentration of anions relative to the total mass of the aqueous medium in the aqueous dispersion was measured as follows: The raw material liquid was freeze-flocculated and then filtered, and the resulting aqueous medium was analyzed by ion chromatography. The analysis by ion chromatography was performed using an ion chromatograph (Thermo Fisher Scientific, ICS-5000). AS-19 was used as the separation column, and an aqueous potassium hydroxide solution was used as the eluent. The concentration of the anion relative to the total mass of the aqueous medium in the aqueous dispersion was calculated from the concentration of the anion in the raw material liquid and the mass ratio of the raw material liquid to the aqueous dispersion.
• the concentrations of sulfate ions, chloride ions, and fluoride ions were determined by creating calibration curves for each substance and calculating the concentrations from the integral values of the peaks. The concentrations of each ion were summed up to calculate the total concentration of sulfate ions, chloride ions, and fluoride ions (specific anions) relative to the total mass of the aqueous medium in the aqueous dispersion.
• the total concentration of anions other than sulfate ions, chloride ions, and fluoride ions (other anions) was determined by creating a calibration curve for trifluoroacetate ions and converting the peak integral value into trifluoroacetate ions.
• Total concentration of cations The total concentration of cations relative to the total mass of the aqueous medium in the aqueous dispersion was measured as follows: The raw material liquid was freeze-flocculated, and then filtered, and the resulting aqueous medium was analyzed by ion chromatography. The total concentration of cations relative to the total mass of the aqueous medium in this aqueous dispersion was measured as follows: 6 mL of the raw material liquid was centrifuged (8,000 rpm, 10 minutes) to precipitate the fluoropolymer, and the supernatant was used as an extract and analyzed by ion chromatography.
• the total concentration of cations relative to the total mass in the solid composition was measured as follows: 5 mL of ultrapure water was added to 2.5 g of the solid composition, and the mixture was subjected to ultrasonic treatment at 50° C. for 2 hours and centrifuged (5000 rpm, 5 minutes) to precipitate the fluoropolymer, and the supernatant was used as an extract and analyzed by ion chromatography. The analysis by ion chromatography was performed using an ion chromatograph (Shimadzu Corporation, HIC-SP). A Shim-pack IC-C4 was used as the separation column, and an aqueous solution of oxalic acid was used as the eluent. The total concentration of cations relative to the total mass of the aqueous medium in the aqueous dispersion was calculated from the concentration of cations in the raw material liquid and the mass ratio of the raw material liquid to the aqueous dispersion.
• the total concentration of cations was determined by creating a calibration curve for ammonium ions and converting the peak integral value into ammonium ions.
• the metal elements in this solution were measured using an ICP-MS (Agilent Technologies, Agilent 7700x) and quantified using the absolute calibration curve method.
• the metal element types measured were 29 types of metal elements (Li, Be, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, and Bi).
• ⁇ Melting Point> Using a differential scanning calorimeter (DSC7200, manufactured by SII), the temperature was determined from the endothermic peak when the material was heated to 380° C. at 10° C./min in an air atmosphere. When there were multiple endothermic peaks, the peak temperature of the largest endothermic peak was used.
• ⁇ DSC endothermic peak ratio> Using a differential scanning calorimeter (DSC7200, manufactured by SII), the differential thermal analysis curve was heated to 380°C at 10°C/min in an air atmosphere, and the length from the largest endothermic peak present at 340°C or higher on the differential thermal analysis curve toward the baseline was defined as A. The length from a point on the baseline 10°C lower than the intersection point drawn from the maximum point toward the baseline to the differential thermal analysis curve was defined as B. The value of B/A was defined as the DSC endothermic peak ratio.
• the raw material liquid A was freeze-coagulated and then filtered to obtain a fluoropolymer 1A, which was analyzed by NMR to find that the TFE unit/PMVE unit ratio was 52/48 (molar ratio) and the Tg was -5°C.
• Raw material liquid B contained the fluoropolymer 1B. After freeze-coagulation of the raw material liquid B, it was filtered off, and the resulting fluoropolymer 1B was analyzed by NMR, and as a result, it was found that the TFE unit/PMVE unit ratio was 52/48 (molar ratio) and the Tg was -5°C.
• anion exchange resin 1 An aqueous sodium hydroxide solution (8% by mass, 100 g) was added to an anion exchange resin AmberLite HPR4200 Cl (manufactured by DuPont, 50 g) and stirred. After 60 minutes from the start of stirring, the mixture was filtered to obtain an anion exchange resin 1.
• Example 1-1 A cation exchange resin Dowex Monosphere 650C (manufactured by DuPont, 20 g) was added to the above raw material liquid A (490 g). 60 minutes after the start of stirring, the raw material liquid and the ion exchange resin were separated by filtration. Anion exchange resin 1 (20 g) was added to the separated raw material liquid. 60 minutes after the start of stirring, the raw material liquid and the ion exchange resin were separated by filtration to obtain raw material liquid A-1 (corresponding to the above-mentioned purified raw material liquid).
• raw material liquid A-1 particles of fluoropolymer 1A were dispersed in an aqueous medium, and the content of fluoropolymer 1A was 0.5% by mass with respect to the total mass of raw material liquid A-1.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid A-1 (475 g) were charged into a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion A-11 (corresponding to the above-mentioned aqueous dispersion X).
• the total concentration of specific anions, the total concentration of other anions, the total concentration of cations and the metal element content were determined using raw material liquid A-1. Based on the obtained values, the total concentration of specific anions, the total concentration of other anions, the total concentration of cations and the metal element content relative to the aqueous medium in aqueous dispersion A-11 were calculated. The results are shown in the table below.
• the content of the fluoropolymer 1A was 0.4% by mass based on the total mass of the aqueous dispersion A-11.
• the concentration of the fluorine-containing emulsifier was 0 ppm by mass based on the total mass of the fluorine-containing polymer 1A in the aqueous dispersion A-11.
• the aqueous dispersion A-11 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.17 mmol) was added to initiate polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. When 90 g of TFE was injected, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 194 minutes, and the polymerization rate calculated from the amount of TFE consumed was 47 g/L/h. After the gas remaining in the reactor was collected, the liquid was extracted.
• aqueous dispersion 1-1 This liquid was designated as aqueous dispersion 1-1 (corresponding to the above-mentioned second aqueous dispersion).
• the aqueous dispersion 1-1 was a dispersion in which particles (average particle diameter 237 nm) containing fluorine-containing polymer 1A and fluorine-containing polymer 2A were dispersed in an aqueous medium, and the solid content concentration was 13 mass%. According to the method described in " ⁇ Concentration of cations in aqueous dispersion>" above, the total concentration of cations was determined using the obtained aqueous dispersion 1-1. Based on the obtained value, the total concentration of cations relative to the aqueous medium in the aqueous dispersion 1-1 was calculated.
• Raw material solution A-2 was obtained in the same manner as in Example 1, except that the anion exchange resin was changed to A300OH manufactured by Purolite Corp.
• raw material solution A-2 particles of fluoropolymer 1A were dispersed in an aqueous medium, and the content of fluoropolymer 1A was 0.5% by mass based on the total mass of raw material solution A-2.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid A-2 (475 g) were charged into a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion A-12.
• the total concentration of the specific anion, the total concentration of other anions, and the total concentration of the cations relative to the aqueous medium in the aqueous dispersion A-12 were calculated in the same manner as in Example 1-1, except that the raw material solution A-2 was used. The results are shown in the table below.
• the aqueous dispersion A-12 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.17 mmol) was added to initiate polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. When 90 g of TFE was injected, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 227 minutes, and the polymerization rate calculated from the amount of TFE consumed was 40 g/L/h. The gas remaining in the reactor was collected, and the liquid was then withdrawn. This liquid was designated as Aqueous Dispersion 1-2.
• Aqueous Dispersion 1-2 was a dispersion in which particles (average particle size 227 nm) containing fluoropolymer 1A and fluoropolymer 2B were dispersed in an aqueous medium, and had a solids concentration of 11 mass%.
• the particles in the obtained aqueous dispersion 1-2 were aggregated and filtered to obtain a solid composition.
• the solid composition dried at 120° C. had a melting point of 338.0° C. and the DSC endothermic peak ratio B/A was unmeasurable.
• Raw material liquid B-1 (corresponding to the above-mentioned purified raw material liquid) was obtained in the same manner as in Example 1-1, except that raw material liquid A was changed to the above-mentioned raw material liquid B.
• Raw material liquid B-1 contained particles of fluoropolymer 1B dispersed in an aqueous medium, and the content of fluoropolymer 1B was 0.5% by mass based on the total mass of raw material liquid B-1.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid B-1 (475 g) were charged into a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion B-11 (corresponding to the above-mentioned aqueous dispersion X).
• the total concentration of the specific anion, the total concentration of other anions, and the total concentration of the cations relative to the aqueous medium in the aqueous dispersion B-11 were calculated in the same manner as in Example 1-1, except that the raw material solution B-1 was used. The results are shown in the table below.
• the content of the fluoropolymer 1B was 0.4% by mass based on the total mass of the aqueous dispersion B-11.
• the concentration of the fluorine-containing emulsifier was 0 ppm by mass based on the total mass of the fluorine-containing polymer 1B in the aqueous dispersion B-11.
• the aqueous dispersion B-11 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.10 mmol) was added to initiate polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. When 120 g of TFE was injected, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 429 minutes, and the polymerization rate calculated from the amount of TFE consumed was 28 g/L/h. After the gas remaining in the reactor was collected, the liquid was withdrawn.
• Aqueous Dispersion 2-1 was a dispersion in which particles (average particle size 292 nm) containing fluoropolymer 1B and fluoropolymer 2C were dispersed in an aqueous medium, and had a solid content concentration of 19 mass%.
• the amount of the aqueous medium in the aqueous dispersion B-11 used in the polymerization was taken as 100 parts by mass, the amount of the monomer (TFE) used in the polymerization was 19 parts by mass.
• the particles in the obtained aqueous dispersion 2-1 were aggregated and filtered to obtain a solid composition.
• the solid composition dried at 120° C. had a melting point of 343.9° C. and a DSC endothermic peak ratio B/A of 0.462.
• Example 2-2 Raw material solution B-2 (corresponding to the above-mentioned purified raw material solution) was obtained in the same manner as in Example 2-1, except that the anion exchange resin was changed to DIAION SA10AOH manufactured by Mitsubishi Chemical Corp.
• Raw material solution B-2 contained particles of fluoropolymer 1B dispersed in an aqueous medium, and the content of fluoropolymer 1B was 0.5% by mass based on the total mass of raw material solution B-2.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid B-2 (475 g) were charged into a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion B-12 (corresponding to the above-mentioned aqueous dispersion X).
• the total concentration of the specific anion, the total concentration of other anions, and the total concentration of the cations relative to the aqueous medium in the aqueous dispersion B-12 were calculated in the same manner as in Example 2-1, except that the raw material solution B-2 was used.
• the results are shown in the table below.
• the content of the fluoropolymer 1B was 0.4% by mass based on the total mass of the aqueous dispersion B-12.
• the concentration of the fluorine-containing emulsifier was 0 ppm by mass based on the total mass of the fluorine-containing polymer 1B in the aqueous dispersion B-12.
• the aqueous dispersion B-12 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.10 mmol) was added to initiate polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. When 120 g of TFE was injected, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 321 minutes, and the polymerization rate calculated from the amount of TFE consumed was 38 g/L/h. The gas remaining in the reactor was collected, and the liquid was then withdrawn. This liquid was designated as Aqueous Dispersion 2-2.
• Aqueous Dispersion 2-2 was a dispersion in which particles (average particle size: 294 nm) containing fluoropolymer 1B and fluoropolymer 2D were dispersed in an aqueous medium, and had a solids concentration of 18% by mass.
• the amount of the aqueous medium in the aqueous dispersion B-12 used in the polymerization was taken as 100 parts by mass, the amount of the monomer (TFE) used in the polymerization was 19 parts by mass.
• the particles in the obtained aqueous dispersion 2-2 were aggregated and filtered to obtain a solid composition.
• the solid composition dried at 120° C. had a melting point of 344.2° C. and a DSC endothermic peak ratio B/A of 0.383.
• Raw material liquid B-3 was obtained in the same manner as in Example 1-2, except that raw material liquid A was changed to raw material liquid B.
• Raw material liquid B-3 contained particles of fluoropolymer 1B dispersed in an aqueous medium, and the content of fluoropolymer 1B was 0.5% by mass based on the total mass of raw material liquid B-3.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid B-3 (475 g) were placed in a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion B-13.
• the total concentration of the specific anion, the total concentration of other anions, and the total concentration of the cations relative to the aqueous medium in the aqueous dispersion B-13 were calculated in the same manner as in Example 2-1, except that the raw material solution B-3 was used. The results are shown in the table below.
• the aqueous dispersion B-13 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.10 mmol) was added to initiate polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant.
• Aqueous Dispersion 2-3 was a dispersion in which particles (average particle size: 302 nm) containing fluoropolymer 1B and fluoropolymer 2E were dispersed in an aqueous medium, and had a solids concentration of 19% by mass. The particles in the obtained aqueous dispersion 2-3 were aggregated and filtered to obtain a solid composition.
• the solid composition dried at 120° C. had a melting point of 338.2° C., and the DSC endothermic peak ratio B/A was unmeasurable.
• raw material liquid B-4 (corresponding to the above-mentioned purified raw material liquid).
• raw material liquid B-4 particles of fluoropolymer 1B were dispersed in an aqueous medium, and the content of fluoropolymer 1B was 0.5% by mass based on the total mass of raw material liquid B-4.
• Paraffin wax (28 g), ultrapure water (121 g), and raw material liquid B-4 (475 g) were charged into a 1.0 L stainless steel pressure reactor to obtain aqueous dispersion B-14.
• the total concentration of specific anions, the total concentration of other anions, and the total concentration of cations in aqueous dispersion B-14 were calculated in the same manner as in Example 2-1, except that raw material liquid B-4 was used. The results are shown in the table below.
• the aqueous dispersion B-14 was heated to 70°C and stirred at 260 rpm. TFE was injected until the pressure in the reactor reached 1.4 MPaG, and disuccinic acid peroxide (0.10 mmol) was added to initiate polymerization.
• Aqueous Dispersion 2-4 was a dispersion in which particles (average particle diameter 309 nm) containing fluoropolymer 1B and fluoropolymer 2F were dispersed in an aqueous medium, and had a solids concentration of 11% by mass.
• the particles in the obtained aqueous dispersion 2-4 were aggregated and filtered to obtain a solid composition.
• the solid composition dried at 120° C. had a melting point of 344.2° C. and a DSC endothermic peak ratio B/A of 0.750.

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