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
  • 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
  • C08F216/00—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
  • C08F216/12—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an ether radical
• • 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
  • C08F216/00—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
  • C08F216/12—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an ether radical
  • C08F216/14—Monomers containing only one unsaturated aliphatic radical
• • 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
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/18—Introducing halogen atoms or halogen-containing groups
  • C08F8/20—Halogenation
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L29/00—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
  • C08L29/10—Homopolymers or copolymers of unsaturated ethers

Definitions

• the present invention relates to a method for producing a fluorinated polymer, an aqueous dispersion, and a 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.
• a method for producing a fluorine-containing polymer there is mentioned a method in which a fluorine-containing emulsifier is used to emulsion-polymerize a fluorine-containing monomer in an aqueous medium (see Patent Document 1).
• the method for producing a fluorine-containing polymer described in Patent Document 1 uses an aqueous medium, which places a small burden on the environment. However, if a large amount of the fluorine-containing emulsifier, which is an essential component, remains in the aqueous dispersion obtained by polymerization, it may be necessary to remove the fluorine-containing emulsifier depending on the application. Furthermore, in recent years, there has been a trend toward restricting the use of fluorine-containing emulsifiers.
• an object of one embodiment of the present invention is to provide a composition containing a fluorinated polymer having excellent heat resistance without requiring a fluorinated emulsifier as an essential component.
• the problem to be solved by one embodiment of the present invention is to provide a method for producing a fluoropolymer which is capable of producing a fluoropolymer having excellent heat resistance without requiring a fluorinated emulsifier as an essential component.
• a problem to be solved by one embodiment of the present invention is to provide an aqueous dispersion containing a fluoropolymer having excellent heat resistance.
• a problem to be solved by one embodiment of the present invention is to provide particles containing a fluoropolymer having excellent heat resistance.
• the present disclosure includes the following aspects.
• a first perfluoropolymer having a glass transition temperature of 10° C. or lower A second fluoropolymer that contains a structural unit based on tetrafluoroethylene and a compound represented by the following formula (1) and is different from the first perfluoropolymer, A composition, wherein the content of structural units based on perfluoro(alkyl vinyl ether) is 0.05 to 5.0 mol % relative to the total content of all structural units of the first perfluoropolymer and the second fluoropolymer.
• Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an ether oxygen atom between carbon atoms.
• Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an ether oxygen atom between carbon atoms.
• the constituent units based on perfluoro(alkyl vinyl ether) are 20 to 70 mol % relative to the total of the constituent units based on tetrafluoroethylene and the constituent units based on perfluoro(alkyl vinyl ether).
• aqueous dispersion A a monomer containing tetrafluoroethylene and a compound represented by the following formula (1) to produce a second fluoropolymer different from the first perfluoropolymer,
• the content of the first perfluoropolymer is 0.01 to 4.0% by mass based on the total mass of the aqueous dispersion A;
• a method for producing a fluorine-containing polymer wherein, before polymerization of a monomer is started, aqueous dispersion A does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier in the aqueous dispersion A is 100 ppm by mass or less based on the total mass of the aqueous dispersion A.
• the step of preparing an aqueous dispersion A is a step of preparing an aqueous dispersion A containing particles of a first perfluoropolymer and an aqueous medium
• the step of producing a second fluoropolymer is a step of polymerizing a monomer to produce a second fluoropolymer different from the first perfluoropolymer, and producing particles containing the first perfluoropolymer and the second fluoropolymer;
• the method for producing a fluoropolymer according to [5] or [6], wherein the ratio of the average particle size of the particles containing the first perfluoropolymer and the second fluoropolymer to the average particle size of the particles of the first perfluoropolymer is 2 or more.
• Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an ether oxygen atom between carbon atoms.
• a melt-formable particle comprising: The average particle size of the particles is 1 ⁇ m or less, the particles contain one or more fluorine-containing polymers,
• the fluorine-containing polymer contains a structural unit based on tetrafluoroethylene, a structural unit based on perfluoro(alkyl vinyl ether), and a structural unit based on a compound represented by the following formula (1): the content of constituent units based on perfluoro(alkyl vinyl ether) is 0.05 to 5.0 mol % based on all constituent units of the fluorine-containing polymer, does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is 100 ppm by mass or less based on the content of the fluorine-containing polymer; Particles, wherein the content of the compound represented by formula (S1) is 1 to 10,000 ppb by mass, and the content of the compound represented by formula (S2) is 100 ppb by mass or less, relative to
• CF 2 CF-CF 2 -O-Rf...(1)
• M each independently represents a hydrogen atom, Na, K, or NH4 ; n represents 7 to 11; and m represents 8 to 12.
• a composition containing a fluorine-containing polymer having excellent heat resistance without requiring a fluorine-containing emulsifier Furthermore, according to one embodiment of the present invention, there is provided a process for producing a fluoropolymer which makes it possible to produce a fluoropolymer having excellent heat resistance without requiring a fluorinated emulsifier as an essential component. Furthermore, according to one embodiment of the present invention, there is provided an aqueous dispersion containing a fluoropolymer having excellent heat resistance. Furthermore, according to one embodiment of the present invention, there is provided particles containing a fluoropolymer having excellent heat resistance.
• the numerical ranges indicated using “to” include the numerical values before and after “to” as the minimum and maximum values, respectively.
• the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range.
• the upper or lower limit of the numerical range may be replaced with a value shown in the examples.
• the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.
• combinations of two or more preferred aspects are more preferred aspects.
• the term "process” refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.
• composition contains a first perfluoropolymer having a glass transition temperature of 10° C. or lower, and a second fluoropolymer that includes a structural unit (hereinafter also referred to as "TFE unit”) based on tetrafluoroethylene (hereinafter also referred to as “TFE unit”) and a structural unit (hereinafter also referred to as “compound (1) unit”) based on a compound represented by the following formula (1) (hereinafter also referred to as “compound (1)”), and is different from the first perfluoropolymer, and the content of the structural unit (hereinafter also referred to as "PAVE unit”) based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE unit”) relative to the total content of all structural units of the first perfluoropolymer and the second fluoropolymer is 0.05 to 5.0 mol%.
• CF 2 CF-CF 2 -O-Rf...(1)
• composition of the present disclosure contains a first perfluoropolymer and a second fluoropolymer, and has excellent heat resistance because the content of PAVE units relative to the total content of all constituent units of the first perfluoropolymer and the second fluoropolymer is 0.05 to 5.0 mol %.
• Patent Document 1 does not include any description focusing on compositions containing two or more types of fluorine-containing copolymers.
• the first perfluoropolymer is a perfluoropolymer having a glass transition temperature of 10° C. or lower.
• perfluoropolymer refers to a polymer in which all hydrogen atoms bonded to carbon atoms in the structural units of the polymer are replaced with fluorine atoms.
• fluoropolymer refers to a polymer in which some or all of the hydrogen atoms bonded to carbon atoms in the structural units of the polymer are replaced with fluorine atoms.
• the glass transition temperature (hereinafter also referred to as "Tg") of the first perfluoropolymer is 10°C or lower.
• the Tg of the first perfluoropolymer 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 specific monomer described below.
• the Tg of the first perfluoropolymer is preferably ⁇ 50° C. or higher, more preferably ⁇ 45° C. or higher, and even more preferably ⁇ 40° C. or higher.
• the Tg of the first perfluoropolymer is measured by differential scanning calorimetry (DSC).
• DSC differential scanning calorimetry
• Tg is measured using a NEXTA DSC600 manufactured by Hitachi High-Tech Corporation. Specifically, 5 mg of a sample for measurement is weighed out and placed in an aluminum sample pan, and the sample is heated to 100°C at a heating rate of 10°C/min under a nitrogen atmosphere. It is then cooled to -60°C at a rate of 10°C/min. When the predetermined temperature is reached, the temperature is again raised to 100°C at 10°C/min. Tg is estimated from the inflection point confirmed in this second heating operation.
• One method for setting the Tg of the first perfluoropolymer within the above range is, for example, to adjust the type and amount of monomer used in producing the first perfluoropolymer.
• the first perfluoropolymer preferably contains TFE units and PAVE units, since this makes it easier to adjust the Tg to the above range and provides better heat resistance.
• the PAVE is preferably a monomer represented by formula (2) from the viewpoint of excellent polymerization reactivity in producing the first perfluoropolymer.
• CF 2 CF-O-R f1 ...(2)
• 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 superior polymerization reactivity.
• the perfluoroalkyl group may be linear or branched.
• PAVE perfluoro(methyl vinyl ether)
• PMVE perfluoro(methyl vinyl ether)
• PEVE perfluoro(ethyl vinyl ether)
• PPVE perfluoro(propyl vinyl ether)
• PMVE or PPVE is preferred as PAVE, and PMVE is more preferred.
• the content of PAVE units relative to the total content of TFE units and PAVE units in the first perfluoropolymer is preferably 20.0 to 70.0 mol%, more preferably 25.0 to 65.0 mol%, and even more preferably 30.0 to 60.0 mol%, from the viewpoint of ease of adjusting the Tg to the above range.
• the first perfluoropolymer may contain structural units based on other monomers other than TFE and PAVE.
• the structural units based on other monomers are preferably 20.0 mol% or less, more preferably 15.0 mol% or less based on the total structural units of the first perfluoropolymer.It is more preferable that the first perfluoropolymer does not substantially contain structural units based on other monomers.
• Substantially free of units based on other monomers means that the content of units based on other monomers is 0.01 mol % or less, more preferably 0.00 mol %, based on the total structural units of the first perfluoropolymer.
• the other monomer is preferably hexafluoropropylene.
• the second fluoropolymer is a different fluoropolymer than the first perfluoropolymer.
• the second fluoropolymer contains TFE units and compound (1) units.
• Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an ether oxygen atom between carbon atoms.
• Rf preferably has 2 to 8 carbon atoms, and more preferably has 3 to 8 carbon atoms.
• Rf may be a straight chain or a branched chain, or may contain a ring structure.
• Examples of Rf include --(CF 2 ) m CF 3 and --(CF 2 ) r1 --O--(CF 2 ) r2 CF 3 .
• m is an integer from 0 to 9.
• r1 is an integer from 1 to 9
• r2 is an integer from 0 to 8, and r1+r2 is an integer from 1 to 9.
• m is preferably an integer of 1 to 7, and more preferably an integer of 1 to 5.
• r1 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.
• r2 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.
• compound (1) is preferably CF 2 ⁇ CF—CF 2 —OCF 2 CF 2 CF3 .
• the content of compound (1) units relative to the total content of TFE units and compound (1) units is preferably 0.2 to 7.0 mol%, more preferably 0.5 to 6.0 mol%, and even more preferably 1.0 to 5.0 mol%, from the viewpoint of heat resistance.
• the second fluoropolymer may contain the structural unit based on other monomers other than TFE and compound (1), but from the viewpoint of heat resistance, the structural unit based on other monomers is preferably 10.0 mol% or less, more preferably 5.0 mol% or less based on the total structural unit of the second fluoropolymer.It is more preferable that the second fluoropolymer does not substantially contain the structural unit based on other monomers. "Substantially free of units derived from other monomers" means that the content of units derived from other monomers is 0.01 mol % or less based on the total constitutional units of the second fluoropolymer; 0.00 mol % is more preferred.
• examples of the other monomer include fluoroolefins such as hexafluoropropylene (HFP) and PAVE (excluding TFE and compound (1)); and acid anhydrides such as itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.
• fluoroolefins such as hexafluoropropylene (HFP) and PAVE (excluding TFE and compound (1)
• acid anhydrides such as itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.
• the content of PAVE units relative to the total content of all constituent units of the first perfluoropolymer and the second fluoropolymer is 0.05 to 5.0 mol%, preferably 0.1 to 4.0 mol%, and more preferably 0.1 to 3.0 mol%. Since the content of PAVE units is 0.05 to 5.0 mol%, the composition has excellent heat resistance.
• the content of the first perfluoropolymer in the solid content of the composition of the present disclosure is preferably 0.01 mass % or more, and more preferably 0.1 mass % or more.
• the content of the first perfluoropolymer in the composition of the present disclosure is preferably 10% by mass or less, more preferably 5% by mass or less.
• the content of the second fluoropolymer in the solid content of the composition of the present disclosure is preferably 90 mass % or more, and more preferably 95 mass % or more.
• the content of the second fluoropolymer in the composition of the present disclosure is preferably 99.99% by mass or less, more preferably 99.9% by mass or less.
• the ratio of the content of the first perfluoropolymer to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 0.2 mass% or more, and more preferably 0.5 mass% or more, from the viewpoint of polymerization stability.
• the ratio of the content of the first perfluoropolymer to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 10 mass% or less, and more preferably 5 mass% or less, from the viewpoint of heat resistance.
• neither the first perfluoropolymer nor the second fluoropolymer contains a functional group, or that the total number of functional groups per 106 main chain carbon atoms of the first perfluoropolymer and the second fluoropolymer is less than 100, more preferably 50 or less, and even more preferably 30 or less.
• Infrared spectroscopy can be used to identify the type of functional group and measure the number of functional groups.
• the functionality is measured by the following method.
• the first perfluoropolymer and the second fluoropolymer are press-molded at 340° C. to prepare a film having a thickness of 200 ⁇ m.
• the film is scanned 16 times by a Fourier transform infrared spectrometer and analyzed to obtain an infrared absorption spectrum.
• the first perfluoropolymer and the second fluoropolymer are subjected to a fluorination treatment in the fluorination step described later for a long period of time to obtain a first perfluoropolymer and a second fluoropolymer that are completely fluorinated.
• the first perfluoropolymer and the second fluoropolymer that are completely fluorinated are press-molded at 340° C. to prepare a completely fluorinated film with a thickness of 200 ⁇ m.
• the completely fluorinated film is scanned 16 times by a Fourier transform infrared spectrometer and analyzed to obtain a base spectrum. From the absorption peak of a specific functional group appearing in the difference spectrum between the obtained infrared absorption spectrum and the base spectrum, the number N of functional groups per 10 6 carbon atoms in the main chain is calculated according to the following formula (A).
• N I ⁇ K/t...(A)
• K correction coefficient
• t film thickness (mm)
• Table 1 shows the absorption frequency, molar absorption coefficient, and correction factor for a specific functional group such as --CF 2 H.
• the molar absorption coefficient of a specific functional group is determined from FT-IR measurement data of a low molecular weight model compound.
• the absorption frequencies of -CH 2 CF 2 H, -CH 2 COF, -CH 2 COOH, -CH 2 COOCH 3 and -CH 2 CONH 2 are several tens of Kaiser (cm -1 ) lower than the respective absorption frequencies of -CF 2 H, -COF, -COOH (free and bonded), -COOCH 3 and -CONH 2 shown in the table.
• the number of --COF is the sum of the number of functional groups determined from the absorption peak at 1883 cm.sup. -1 due to --CF.sub.2 COF and the number of functional groups determined from the absorption peak at 1840 cm.sup. -1 due to --CH.sub.2 COF.
• the functional groups in the first perfluoropolymer and the second fluoropolymer are functional groups present at the ends of the main chain or side chains of each polymer, and functional groups present in the main chain or side chain.
• the functional group is introduced, for example, by a chain transfer agent or a polymerization initiator used in producing the first perfluoropolymer and the second fluoropolymer.
• the functional group is introduced to the side chain end of the polymer by polymerizing a monomer having a functional group.
• the composition of the present disclosure is preferably a composition containing a polymer that has been subjected to a fluorination treatment.
• the composition of the present disclosure may be a particle, a powder composition containing a plurality of particles, or a liquid composition.
• the composition of the present disclosure may be a dispersion in which the particles are dispersed in water or an organic solvent.
• the particles are preferably particles containing a first perfluoropolymer and a second fluoropolymer, and having a PAVE unit content of 0.1 to 10.0 mol% relative to the total content of all structural units of the first perfluoropolymer and the second fluoropolymer (hereinafter also referred to as "the present particles").
• the composition of the present disclosure when it is a powder composition or a liquid composition, it preferably contains the present particles.
• the average particle size of the present particles is preferably 1 ⁇ m or less, more preferably 700 nm or less, and even more preferably 500 nm or less. From the viewpoint of aggregation, the lower limit of the average particle size of the present particles is preferably 30 nm.
• the composition of the present disclosure may be in the form of pellets or a molded article such as a film or a tube.
• the average particle size of the present particles means the arithmetic mean of particle sizes of five different particles obtained by photographing the present particles with a scanning electron microscope and determining the particle sizes from the resulting SEM image.
• the average particle diameter of the present particles is determined by measuring the particle size distribution by a laser diffraction/scattering method, determining a cumulative curve with the total volume of the particle group set to 100%, and determining the particle diameter (D50) at the point on the cumulative curve where the cumulative volume is 50%.
• the viscosity of the dispersion is preferably 0.8 to 2.0 mPa ⁇ s, and more preferably 1.0 to 1.5 mPa ⁇ s.
• the viscosity of the dispersion is a value measured using a Brookfield viscometer at room temperature (25° C.) and a rotation speed of 30 rpm. The measurement is repeated three times, and the average value of the three measured values is used.
• the composition of the present disclosure is preferably substantially free of a fluorine-containing emulsifier. Details of the fluorine-containing emulsifier are described below.
• the composition of the present disclosure does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is preferably 100 ppm by mass or less, more preferably 10 ppm by mass or less, even more preferably 5 ppm by mass or less, and particularly preferably 1 ppm by mass or less, relative to the total content of the first perfluoropolymer and the second fluoropolymer.
• the content of the fluorine-containing emulsifier relative to the total content of the first perfluoropolymer and the second fluoropolymer is determined by a method similar to the method for measuring the content of the fluorine-containing surfactant by liquid chromatography-mass spectrometry described in paragraphs [0364] to [0369] of WO 2021/045227.
• the content of the compound represented by the following formula (S1) relative to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 1 ppb by mass or more, and more preferably 10 ppb by mass or more, relative to the fluoropolymer, from the viewpoint of processability.
• the content of the compound represented by the following formula (S1) relative to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 10,000 ppb by mass or less, more preferably 1,000 ppb by mass or less, and even more preferably 300 ppb by mass or less, from the viewpoint of suppressing deterioration of the physical properties such as heat resistance of the composition of the present disclosure.
• the content of the compound represented by the following formula (S2) relative to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 0.1 ppb by mass or more, and more preferably 1 ppb by mass or more, relative to the fluoropolymer, from the viewpoint of processability.
• the content of the compound represented by the following formula (S2) relative to the total content of the first perfluoropolymer and the second fluoropolymer is preferably 50 ppb by mass or less, and more preferably 25 ppb by mass or less, from the viewpoint of suppressing deterioration of the physical properties such as heat resistance of the composition of the present disclosure.
• M each independently represents a hydrogen atom, Na, K, or NH4 ; n represents 7 to 11; and m represents 8 to 12.
• the content of the compound represented by formula (S1) relative to the total content of the first perfluoropolymer and the second fluoropolymer can be calculated by a method using an aqueous dispersion among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0710] to [0720] of WO 2018/181904.
• the content of the compound represented by formula (S2) relative to the total content of the first perfluoropolymer and the second fluoropolymer can be calculated by a method using an aqueous dispersion among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0721] to [0732] of WO 2018/181904.
• composition of the present disclosure may be subjected to a fluorination treatment to adjust the content of the compound represented by formula (S1).
• fluorination treatment method include the methods described below.
• the method for producing a fluorine-containing polymer of the present disclosure includes the steps of preparing an aqueous dispersion A containing a first perfluoropolymer having a Tg of 10° C. or less and an aqueous medium, and polymerizing a monomer (hereinafter also referred to as a "specific monomer") containing TFE and compound (1) in the aqueous dispersion A to produce a second fluoropolymer different from the first perfluoropolymer.
• a monomer hereinafter also referred to as a "specific monomer”
• the content of the first perfluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion A, and before starting polymerization of the specific monomer, the aqueous dispersion A does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is 100 ppm by mass or less relative to the total mass of the aqueous dispersion A.
• “before starting polymerization of the specific monomer” means immediately before the start of polymerization of the specific monomer.
• start of polymerization include the time when the specific monomer and the polymerization initiator are made to coexist in the reactor after the temperature inside the reactor is raised to the polymerization temperature or higher, and the time when the temperature inside the reactor is raised to the polymerization temperature or higher after the temperature inside the reactor is raised to the polymerization temperature or higher.
• a second fluoropolymer can be produced efficiently by polymerizing a monomer containing TFE and HFP in an aqueous dispersion A containing a first perfluoropolymer having a Tg of 10°C or less and an aqueous medium, even if the content of the fluoroemulsifier is 100 ppm by mass or less relative to the total mass of the aqueous dispersion A.
• the method for producing a fluoropolymer according to the present disclosure preferably includes, in this order, a step of preparing an aqueous dispersion A and a step of producing a second fluoropolymer different from the first perfluoropolymer.
• the method for producing a fluoropolymer of the present disclosure includes a step of preparing an aqueous dispersion A containing a first perfluoropolymer having a Tg of 10° C. or less, and an aqueous medium (hereinafter also referred to as the "aqueous dispersion A preparation step").
• the first perfluoropolymer is preferably dispersed in the aqueous medium in the form of particles.
• the average particle size of the first perfluoropolymer is preferably from 1 to 200 nm, more preferably from 10 to 150 nm, and even more preferably from 30 to 120 nm, from the viewpoint of more efficient production of the second fluoropolymer.
• the average particle diameter of the first perfluoropolymer is determined by measuring the particle size distribution using a laser diffraction/scattering method, calculating a cumulative curve with the total volume of the particle group set as 100%, and determining the particle diameter (D50) at the point on the cumulative curve where the cumulative volume is 50%.
• the first perfluoropolymer can be produced, for example, by polymerizing a monomer (preferably a mixture of monomers containing TFE and compound (1)) in a polymerization solvent in the presence of a polymerization initiator. This results in a dispersion of the first perfluoropolymer dispersed in particulate form in the polymerization solvent.
• a monomer preferably a mixture of monomers containing TFE and compound (1)
• the pH of the reaction system containing the monomer and the polymerization solvent before the start of polymerization is preferably 6.5 or more, more preferably 7.0 or more, from the viewpoint of efficiently proceeding with the polymerization.
• the pH of the reaction system is preferably 10.5 or less, more preferably 10 or less, from the viewpoint of improving the stability of the first perfluoropolymer.
• the pH of the reaction system can be adjusted using a pH adjuster. Examples of the pH adjuster include ammonia and the pH adjuster that may be contained in the aqueous dispersion A described below, with ammonia being preferred.
• the dispersion of the first perfluoropolymer thus obtained may be used as the aqueous dispersion A as is.
• Another aqueous medium may be added to the dispersion of the first perfluoropolymer, and this may be used as the aqueous dispersion.
• the first perfluoropolymer may be dispersed in another aqueous medium by solvent replacement, and this may be used as the aqueous dispersion A.
• the polymerization initiator used in the production of the first perfluoropolymer is preferably a water-soluble polymerization initiator, more preferably a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate; a peroxide such as disuccinic acid peroxide; or an azo compound such as azobisisobutylamidine dihydrochloride, further preferably a persulfate, and particularly preferably ammonium persulfate.
• a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate
• a peroxide such as disuccinic acid peroxide
• an azo compound such as azobisisobutylamidine dihydrochloride
• the polymerization solvent may be water or a mixture of water and a water-soluble organic solvent.
• water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.
• the method for producing the first perfluoropolymer may include a heating step of heating the dispersion liquid in which the first perfluoropolymer is dispersed after obtaining the dispersion liquid.
• the aqueous medium contained in the aqueous dispersion A prepared in the aqueous dispersion A preparation step may be the polymerization solvent used in producing the first perfluoropolymer.
• Specific examples of the aqueous medium contained in the aqueous dispersion A are the same as the specific examples of the polymerization solvent used in producing the first perfluoropolymer.
• the content of the aqueous medium is preferably 60.0 to 99.9 mass%, more preferably 96 to 99.9 mass%, and even more preferably 98.0 to 99.9 mass%, based on the total mass of the aqueous dispersion A.
• the aqueous dispersion A may contain other components in addition to the first perfluoropolymer and the aqueous medium.
• specific examples of other components that may be contained in the aqueous dispersion A include a chain transfer agent, an emulsifier other than the fluorine-containing emulsifier, a pH adjuster, and a wax.
• an emulsifier is a compound that has hydrophilic and hydrophobic portions.
• the emulsifier includes a hydrocarbon-containing surfactant, a fluorine-containing emulsifier, and a polymer emulsifier. Neither the first perfluoropolymer nor the second fluoropolymer corresponds to an emulsifier.
• the emulsifier may be either ionic or non-ionic.
• a hydrocarbon-containing surfactant is a surfactant that contains a hydrocarbon group. More specifically, the hydrocarbon-containing surfactant may contain substitutions with halogen atoms such as fluorine atoms and chlorine atoms, so long as it contains a hydrocarbon group. In a hydrocarbon-containing surfactant, it is preferable that 75% or more of the atoms or monovalent groups bonded to carbon atoms of the hydrocarbon group are hydrogen atoms, more preferably 85% or more, and even more preferably 95% or more.
• Hydrocarbon-containing surfactants include hydrocarbon surfactants and siloxane surfactants.
• Hydrocarbon surfactants refer to surfactants that do not contain silicon atoms and in which 100% of the atoms or monovalent groups bonded to carbon atoms in the hydrocarbon group are hydrogen atoms, and therefore do not contain halogen atoms such as chlorine atoms and fluorine atoms.
• Siloxane surfactants refer to hydrocarbon-containing surfactants that have a hydrophobic group that contains a siloxane skeleton containing a large number of siloxane units.
• Hydrocarbon surfactants include anionic hydrocarbon surfactants.
• An anionic hydrocarbon surfactant refers to a hydrocarbon surfactant having a negatively charged hydrophilic portion such as a carboxylic acid group, a sulfonic acid group, a sulfate group, a phosphonic acid group, or a phosphate group, and a hydrocarbon portion such as an alkyl group as a hydrophobic portion.
• An example of an anionic hydrocarbon surfactant is the highly branched C10 tertiary carboxylic acid supplied by Resolution Performance Products as Versatic® 10.
• Other examples of anionic hydrocarbon surfactants include the sodium linear alkyl polyether sulfonates supplied by BASF as the Avanel® S series.
• Anionic hydrocarbon surfactants include sodium dodecyl sulfate.
• anionic hydrocarbon surfactant is the sulfosuccinate surfactant Lankropol® K8300 available from Akzo Nobel Surface Chemistry LLC.
• Hydrocarbon surfactants also include non-ionic hydrocarbon surfactants.
• Nonionic hydrocarbon surfactants do not have charged groups, but have a hydrophobic portion that is often a long-chain hydrocarbon.
• the hydrophilic portion of nonionic hydrocarbon surfactants includes water-soluble functional groups such as polyethylene oxide chains obtained from the polymerization of ethylene oxide.
• Nonionic hydrocarbon surfactants include block copolymers with various types of polyalkylene oxide blocks, such as polyethylene oxide and polypropylene oxide.
• nonionic hydrocarbon surfactants examples include those described in paragraphs [0043] to [0052] of JP2016-537499A.
• Siloxane surfactants include those described in U.S. Pat. Nos. 6,841,616 (Wille et al.) and 7,977,438 (Brothers et al.).
• the fluorine-containing emulsifier may be an anionic fluorine-containing surfactant.
• anionic fluorine-containing surfactant include surfactants containing fluorine atoms in which the total number of carbon atoms excluding the anionic group is 20 or less, and surfactants containing fluorine in the anionic moiety having a molecular weight of 800 or less.
• anionic moiety means the portion of the fluorine-containing surfactant excluding the cation.
• polymeric emulsifiers include water-soluble polymers that have hydrophilic groups on their side chains.
• examples of such polymeric emulsifiers include polymers that contain structural units based on compounds that have sites that can react by polymerization and hydrophilic groups.
• Other examples include polymers that have been subjected to post-treatments such as hydrolysis on polymers that contain structural units based on compounds that have groups that can become hydrophilic groups.
• chain transfer agents include ethyl acetate, methanol, ethanol, t-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane. From the viewpoint of being able to control the molecular weight with a small amount, the chain transfer agent is preferably t-butyl methyl ether or methane, and more preferably t-butyl methyl ether.
• pH adjusters include inorganic salts.
• inorganic salts include phosphates such as disodium hydrogen phosphate and sodium dihydrogen phosphate; and carbonates such as sodium hydrogen carbonate and sodium carbonate. More preferred specific examples of phosphates include disodium hydrogen phosphate dihydrate and disodium hydrogen phosphate dodecahydrate.
• wax examples include Paraffin Wax-155 and Paraffin Wax-150 (both manufactured by Nippon Seiro Co., Ltd.).
• the content of the chain transfer agent is preferably 0.1 to 5.0 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 20.0 parts by mass, more preferably 0.1 to 15.0 parts by mass, and even more preferably 0.1 to 10.0 parts by mass, relative to 100 parts by mass of the specific monomer described below.
• the content of the emulsifier other than the fluorine-containing emulsifier is preferably 0.01 to 5.0 parts by mass based on 100 parts by mass of the aqueous medium.
• aqueous dispersion A contains a pH adjuster
• the content of the pH adjuster is preferably 0.01 to 3.0 parts by mass per 100 parts by mass of the aqueous medium.
• the pH of the aqueous dispersion A is preferably 1.0 or more, more preferably 2.0 or more, from the viewpoint of stable polymerization of the second fluoropolymer.
• the pH of the aqueous dispersion A is preferably 11 or less, more preferably 10.5 or less, from the viewpoint of stable polymerization of the second fluoropolymer.
• the content of the wax is preferably 1 to 10 parts by mass per 100 parts by mass of the aqueous medium.
• the viscosity of the aqueous dispersion A is preferably 2.0 mPa ⁇ s or less, more preferably 1.9 mPa ⁇ s or less, and even more preferably 1.7 mPa ⁇ s or less. From the viewpoint of stable polymerization of the second fluoropolymer, the viscosity of the aqueous dispersion A is preferably 0.85 mPa ⁇ s or more, and more preferably 0.9 mPa ⁇ s or more.
• the thixotropy ratio of the aqueous dispersion A is preferably 0.9 or more, more preferably 0.95 or more, from the viewpoint of stable polymerization of the second fluoropolymer.
• the thixotropy ratio of the aqueous dispersion A is preferably 1.2 or less, more preferably 1.1 or less, from the viewpoint of stable polymerization of the second fluoropolymer.
• the viscosity of the aqueous dispersion A is a value measured using a Brookfield viscometer at room temperature (25° C.) and a rotation speed of 30 rpm. The measurement is repeated three times, and the average value of the three measured values is used.
• the thixotropy ratio of aqueous dispersion A is determined by dividing the viscosity of aqueous dispersion A measured at a rotation speed of 30 rpm by the viscosity of aqueous dispersion A measured at a rotation speed of 60 rpm.
• the method for producing a fluoropolymer of the present disclosure includes a step of polymerizing a specific monomer in aqueous dispersion A to produce a second fluoropolymer different from the first perfluoropolymer (hereinafter also referred to as the "second fluoropolymer production step").
• the content of the first perfluoropolymer is 0.01 to 4.0% by mass, preferably 0.05 to 3.0% by mass, and more preferably 0.1 to 2.0% by mass, based on the total mass of the aqueous dispersion A.
• the content of the first perfluoropolymer is 0.01% by mass or more, the polymerization stability (productivity) is excellent, and when the content of the first perfluoropolymer is 4.0% by mass or less, the heat resistance of the polymer obtained by polymerization (i.e., the mixture of the first perfluoropolymer and the second fluoropolymer) is excellent.
• the aqueous dispersion A does not contain a fluorinated emulsifier, or the content of the fluorinated emulsifier is 100 ppm by mass or less, preferably 50 ppm by mass or less, more preferably 25 ppm by mass or less, and still more preferably 5 ppm by mass or less, based on the total mass of the aqueous dispersion A.
• the lower limit is 0 ppm by mass.
• the second fluoropolymer can be produced efficiently even when the content of the fluorinated emulsifier is 100 ppm by mass or less.
• the concentration of the fluoride ion is preferably 100 ppm by mass or less, and more preferably 50 ppm by mass or less, based on the total mass of the aqueous dispersion A, from the viewpoint of polymerization stability.
• the lower limit is 0 ppm by mass.
• One example of a method for adjusting the fluoride ion concentration to the above range is to remove sulfate ions using an anion exchange resin during the production of the first perfluoropolymer.
• the fluoride ions may be generated by the reaction between a polymerization initiator (e.g., ammonium persulfate) and a monomer used in the production of the first fluorine-containing polymer, and may be contained in the aqueous dispersion.
• a polymerization initiator e.g., ammonium persulfate
• the concentration of sulfate ions is preferably 10 ppm by mass or less, and more preferably 5 ppm by mass or less, relative to the total mass of the aqueous medium in the aqueous dispersion, in order to suppress discoloration of the second fluorine-containing polymer.
• the lower limit is 0 ppm by mass.
• One example of a method for adjusting the sulfate ion concentration to the above value is to remove sulfate ions using an anion exchange resin during the production of the first perfluoropolymer.
• the sulfate ions here originate, for example, from a polymerization initiator (particularly ammonium persulfate) used in the production of the first perfluoropolymer, and may be contained in the aqueous dispersion containing the first perfluoropolymer. It is presumed that by making the content of sulfate ions 10 ppm by mass or less (particularly 5 ppm by mass or less), it is possible to suppress the formation of terminal groups with low heat resistance in the second fluoropolymer, thereby suppressing discoloration of the second fluoropolymer.
• a polymerization initiator particularly ammonium persulfate
• the concentration of ammonium ions is preferably 20 ppm by mass or less, and more preferably 10 ppm by mass or less, relative to the total mass of the aqueous medium in the aqueous dispersion, in order to suppress aggregation of the second fluoropolymer.
• the lower limit is 0 ppm by mass.
• ammonium ion concentration is to remove ammonium ions using a cation exchange resin during the production of the first perfluoropolymer.
• the ammonium ion may be derived from, for example, an initiator (particularly ammonium persulfate) used in the production of the first perfluoropolymer, and may be contained in the aqueous dispersion containing the first perfluoropolymer. It is presumed that the content of ammonium ion is 20 mass ppm or less, the ionic strength in the aqueous medium is reduced, and the production efficiency of the second fluoropolymer is improved.
• the specific monomer includes TFE and the compound (1).
• the amount of compound (1) used relative to the total amount of TFE and compound (1) used is preferably 0.2 to 7.0 mol%, more preferably 0.5 to 6.0 mol%, and even more preferably 1.0 to 5.0 mol%, from the viewpoint of heat resistance.
• the specific monomer may contain other monomers other than TFE and compound (1).
• the amount of other monomers used is preferably 10.0 mol% or less, more preferably 5.0 mol% or less, based on the total amount of the specific monomers used.It is more preferable that the specific monomer does not substantially contain other monomers. "Substantially free of other monomers” means that the amount of other monomers used is 0.01 mol % or less, and may be 0.00 mol %, based on the total amount of the specific monomers used.
• Examples of the other monomers include fluoroolefins such as HFP and PAVE (excluding TFE and compound (1)); and acid anhydrides such as itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.
• 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, per 100 parts by mass of the aqueous medium contained in the aqueous dispersion A.
• Polymerization initiator In the second fluoropolymer production step, it is preferable to polymerize the specific monomer in the presence of a polymerization initiator.
• an oil-soluble radical initiator a water-soluble radical initiator, or a water-soluble redox catalyst is preferred.
• 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").
• PBPV tert-butyl peroxypivalate
• IPP diisopropyl peroxydicarbonate
• Water-soluble radical initiators include persulfates such as ammonium persulfate and potassium persulfate, and 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").
• water-soluble redox catalyst As the water-soluble redox catalyst, a combination of an oxidizing agent such as bromic acid or its salts, chloric acid or its salts, persulfuric acid or its salts, permanganic acid or its salts, or hydrogen peroxide, and a reducing agent such as sulfurous acid or its salts, hydrogen sulfite or its salts, thiosulfuric acid or its salts, organic acids, or inorganic salts is preferred.
• an oxidizing agent such as bromic acid or its salts, chloric acid or its salts, persulfuric acid or its salts, permanganic acid or its salts, or hydrogen peroxide
• a reducing agent such as sulfurous acid or its salts, hydrogen sulfite or its salts, thiosulfuric acid or its salts, organic acids, or inorganic salts is preferred.
• persulfates potassium persulfate and ammonium persulfate are preferred.
• inorganic salts combinations of sulfate anions, sulfite anions, and chloride anions with metal ions are preferred.
• metal ions transition metal ions are preferred, and examples thereof include manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver ions, with iron ions being preferred.
• iron (II) sulfate is preferred.
• the polymerization initiator is preferably an oil-soluble radical initiator or a water-soluble radical initiator, more preferably an oil-soluble radical initiator from the viewpoint of more efficient production of the fluorine-containing polymer, and further preferably an oil-soluble organic peroxide.
• the polymerization initiator may be used alone or in combination of two or more kinds.
• the amount of polymerization initiator used is preferably 1 to 1000 ppm by mass relative to the amount of specific monomer used, more preferably 5 to 750 ppm, and even more preferably 10 to 500 ppm.
• 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 based on 100 parts by mass of the specific monomer used.
• the second fluoropolymer obtained in the second fluoropolymer production step may be copolymerized with the first perfluoropolymer.
• the specific monomer is introduced into the reaction system (i.e., polymerization reaction vessel) by a conventional method.
• the specific monomer may be continuously or intermittently introduced into the reaction system 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 continuously or intermittently introduced into the reaction system.
• 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 method for producing a fluorine-containing polymer disclosed herein produces particles containing the first perfluoropolymer and the second fluoropolymer.
• the second fluoropolymer is obtained in the form of particles containing the first perfluoropolymer and the second fluoropolymer.
• an aqueous dispersion is obtained in which particles containing the first perfluoropolymer and the second fluoropolymer are dispersed in the aqueous medium.
• the method for producing a fluoropolymer of the present disclosure it is preferable to obtain particles containing a first perfluoropolymer and a second fluoropolymer. That is, the method for producing a fluoropolymer of the present disclosure is A step of preparing an aqueous dispersion A containing particles of a first perfluoropolymer having a glass transition temperature of 10° C.
• the aqueous dispersion A does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier in the aqueous dispersion A is preferably 100 ppm by mass or less based on the total mass of the aqueous dispersion A.
• the average particle size of the particles containing the first perfluoropolymer and the second fluoropolymer is preferably 1 ⁇ m or less, more preferably 700 nm or less, and more preferably 500 nm or less, from the viewpoint of polymerization stability.
• the lower limit of the average particle size of the particles containing the first perfluoropolymer and the second fluoropolymer is preferably 30 nm, from the viewpoint of aggregation.
• 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 ratio of the average particle size of the particles containing the first perfluoropolymer and the second fluoropolymer to the average particle size of the particles of the first perfluoropolymer is preferably 2 or more, more preferably 3 or more. From the viewpoint of polymerization stability, the ratio of the average particle sizes is preferably 10 or less, more preferably 8 or less. When the above ratio is 2 or more, particles with excellent heat resistance that reflect the physical properties of the second fluoropolymer can be obtained.
• the method for producing a fluoropolymer according to the present disclosure preferably further comprises a step of subjecting the first perfluoropolymer and the second fluoropolymer to a fluorination treatment (hereinafter also referred to as a "fluorination step").
• the method of the fluorination treatment is not particularly limited, and can be carried out by a conventionally known method.
• the fluorination can be carried out by contacting the first perfluoropolymer and the second fluoropolymer with fluorine gas.
• the fluorine gas may be diluted with an inert gas before use.
• the inert gas include rare gases such as helium gas, neon gas, and argon gas, and nitrogen gas, with nitrogen gas or helium gas being preferred, and nitrogen gas being more preferred from the viewpoint of economical advantage.
• the proportion of fluorine gas is preferably 10 to 60% by volume in the total of fluorine gas and inert gas (100% by volume).
• the temperature of the fluorination treatment is, for example, 100 to 250°C.
• the fluorination treatment time is, for example, 1 to 15 hours.
• the functional groups contained in the first perfluoropolymer and the second fluoropolymer are fluorinated, which improves the heat resistance.
• the total number of functional groups per 106 carbon atoms in the main chain of the first perfluoropolymer and the second fluoropolymer is preferably less than 100, more preferably 50 or less, and even more preferably 30 or less.
• the lower limit of the number of functional groups is 0.
• the aqueous dispersion of the present disclosure is an aqueous dispersion comprising an aqueous medium and melt-formable particles, the particles having an average particle size of 1 ⁇ m or less, the particles comprising one or more types of fluoropolymer, the fluoropolymer comprising TFE units, PAVE units and compound (1) units, the content of PAVE units being 0.05 to 5.0 mol % relative to all constitutional units of the fluoropolymer, the content of the particles being 1 to 50 mass % relative to the total mass of the aqueous dispersion, and either not comprising a fluorinated emulsifier or the content of the fluorinated emulsifier being 10 ppm by mass or less relative to the content of the fluorinated polymer.
• the aqueous dispersion of the present disclosure can be obtained, for example, by the production method of the fluoropolymer of the present disclosure.
• the above aqueous dispersion A is an aqueous dispersion obtained during the process for producing a fluoropolymer of the present disclosure, and is different from the aqueous dispersion of the present disclosure.
• the aqueous dispersions of the present disclosure include melt-formable particles.
• melt-formable means having a melt flow rate (MFR) of 0.1 to 1000 g/10 min.
• MFR of the particles is preferably from 0.1 to 100 g/10 min, and more preferably from 1 to 80 g/10 min.
• the MFR is measured in accordance with ASTM D3307 under conditions of a temperature of 372° C. and a load of 49 N, and is measured as the mass flowing out of an orifice having a diameter of 2 mm and a length of 8 mm in 10 minutes.
• the average particle size of the particles is 1 ⁇ m or less, and from the viewpoint of dispersibility, it is preferably 700 nm or less, and more preferably 500 nm or less. From the viewpoint of cohesion, the lower limit of the average particle size of the particles is preferably 30 nm.
• the average particle size of particles is the particle size at the point on the cumulative curve where the cumulative volume is 50% when the particle size distribution is measured by a laser diffraction/scattering method and the total volume of the particle group is set to 100% to obtain a cumulative curve.
• the particle content is 1 to 50 mass% relative to the total mass of the aqueous dispersion of the present disclosure, preferably 2 to 45 mass%, and more preferably 3 to 40 mass%.
• the particles contained in the aqueous dispersion of the present disclosure contain one or more types of fluorine-containing polymers.
• the particles When the particles contain two or more types of fluoropolymers, the particles need only contain a fluoropolymer containing TFE units, PAVE units, and compound (1) units, and may contain a fluoropolymer that does not fall under the category of a fluoropolymer containing TFE units, PAVE units, and compound (1) units.
• the particles contain two or more types of fluoropolymers, one fluoropolymer does not have to contain all of the TFE units, PAVE units, and compound (1) units.
• the particles may contain a fluoropolymer containing TFE units and PAVE units, and a fluoropolymer containing TFE units and compound (1) units.
• the content of compound (1) units relative to the total content of TFE units and compound (1) units is preferably 0.2 to 7.0 mol%, more preferably 0.5 to 6.0 mol%, and even more preferably 1.0 to 5.0 mol%.
• a particle contains two or more types of fluoropolymers, it is not necessary that any of the fluoropolymers contained in the particle is melt-formable, so long as the particle is melt-formable.
• the content of PAVE units is 0.05 to 5.0 mol%, preferably 0.1 to 4.0 mol%, and more preferably 0.1 to 3.0 mol%, based on the total constituent units of the fluoropolymer. Since the content of PAVE units is 0.05 to 5.0 mol%, the polymer has excellent heat resistance.
• all constituent units of the fluoropolymer means all constituent units in the two or more types of fluoropolymers.
• PAVE is preferably a monomer represented by the above formula (2).
• the content of the first perfluoropolymer in the particles is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more.
• the content of the first perfluoropolymer in the particles is preferably 10% by mass or less, more preferably 5% by mass or less.
• the content of the second fluoropolymer in the particles is preferably 90% by mass or more, more preferably 95% by mass or more.
• the content of the second fluoropolymer in the particles is preferably 99.99% by mass or less, more preferably 99.9% by mass or less.
• the ratio of the content of the first perfluoropolymer to the total content of the first perfluoropolymer and the second fluoropolymer in the particles is preferably 0.01 mass% or more, and more preferably 0.1 mass% or more, from the viewpoint of improving physical properties such as heat resistance.
• the ratio of the content of the first perfluoropolymer to the total content of the first perfluoropolymer and the second fluoropolymer in the particles is preferably 10 mass% or less, more preferably 5 mass% or less, from the viewpoint of improving physical properties such as heat resistance.
• PMVE is preferred over PAVE because of its superior heat resistance.
• the particles preferably contain the first perfluoropolymer and the second fluoropolymer. Details of the first perfluoropolymer and the second fluoropolymer are as described above.
• aqueous medium contained in the aqueous dispersion of the present disclosure are the same as the specific examples of the aqueous medium used in producing the first perfluoropolymer described above.
• the content of the aqueous medium is preferably 50 to 99% by mass, more preferably 60 to 99% by mass, and even more preferably 70 to 99% by mass, based on the total mass of the aqueous dispersion of the present disclosure.
• the aqueous dispersion of the present disclosure is preferably substantially free of a fluorine-containing emulsifier. Details of the fluorine-containing emulsifier are as described above.
• the aqueous dispersion of the present disclosure does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is 100 ppm by mass or less, preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, and even more preferably 1 ppm by mass or less, based on the content of the fluorine-containing polymer.
• the content of the fluorinated emulsifier relative to the content of the fluorinated polymer can be determined by a method similar to the measurement method for the content of the fluorinated surfactant by liquid chromatography-mass spectrometry described in paragraphs [0364] to [0369] of WO 2021/045227.
• the viscosity of the aqueous dispersion of the present disclosure is preferably from 0.8 to 2.0 mPa ⁇ s, and more preferably from 1.0 to 1.5 mPa ⁇ s, from the viewpoint of processability.
• the viscosity of the aqueous dispersion is a value measured using a Brookfield viscometer at room temperature (25° C.) and a rotation speed of 30 rpm. The measurement is repeated three times, and the average value of the three measured values is used.
• the content of the compound represented by the following formula (S1) in the aqueous dispersion of the present disclosure relative to the fluoropolymer is preferably 1 ppb by mass or more, and more preferably 10 ppb by mass or more, relative to the fluoropolymer, from the viewpoint of stabilizing the fluoropolymer in the aqueous dispersion.
• the content of the compound represented by the following formula (S1) relative to the fluoropolymer is preferably 10,000 ppb by mass or less, more preferably 1,000 ppb by mass or less, and even more preferably 300 ppb by mass or less, from the viewpoint of preventing deterioration of physical properties.
• the content of the compound represented by the following formula (S2) in the aqueous dispersion of the present disclosure relative to the fluoropolymer is preferably 0.1 ppb by mass or more, and more preferably 1 ppb by mass or more, relative to the fluoropolymer, from the viewpoint of stabilizing the fluoropolymer in the aqueous dispersion.
• the content of the compound represented by the following formula (S2) relative to the fluoropolymer is preferably 50 ppb by mass or less, and more preferably 25 ppb by mass or less, from the viewpoint of preventing deterioration of physical properties.
• M each independently represents a hydrogen atom, Na, K, or NH4 ; n represents 7 to 11; and m represents 8 to 12.
• the content of the compound represented by formula (S1) in the fluoropolymer can be calculated by a method using an aqueous dispersion among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0710] to [0720] of WO 2018/181904.
• the content of the compound represented by formula (S2) in the fluoropolymer can be calculated by a method using an aqueous dispersion among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0721] to [0732] of WO 2018/181904.
• the compound represented by formula (S1) and the compound represented by formula (S2) are components that may be generated when the above-mentioned specific monomer (particularly TFE) is polymerized in the presence of a polymerization initiator, a chain transfer agent, and a fluorinated emulsifier. Therefore, in the method for producing a fluorinated polymer of the present disclosure, when a fluorinated emulsifier is not used, the amount of the compound represented by formula (S1) and the compound represented by formula (S2) generated can be suppressed, and it is easy to keep the content of these compounds within the above range.
• the aqueous dispersion of the present disclosure does not necessarily require a fluorine-containing emulsifier, and therefore can easily be made into a dispersion in an organic solvent such as N-methylpyrrolidone or acetone by solvent substitution.
• the aqueous dispersion of the present disclosure can be mixed with an organic solvent and dehydrated using evaporation or anhydrous sodium sulfate or the like to form a dispersion in an organic solvent.
• the aqueous dispersion of the present disclosure stably disperses fluorine-containing polymers even without the inclusion of a fluorine-containing emulsifier. Therefore, it can be suitably used for coating applications, as a binder, etc.
• a powder can be obtained by agglomerating particles from the aqueous dispersion of the present disclosure.
• Flocculation methods include, but are not limited to, freeze flocculation, acid flocculation, base flocculation, and flocculation using a coagulant.
• the aggregation temperature is preferably ⁇ 20 to 0° C.
• the aggregation time is preferably 1 hour or more, more preferably 2 hours or more.
• acid coagulation a method of adding an acid-containing solution to the aqueous dispersion of the present disclosure 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 of the present disclosure.
• the base to be added include sodium hydroxide, potassium hydroxide, ammonium carbonate, etc., and sodium hydroxide is preferred.
• the concentration of the base in the solution containing the base is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.
• a known coagulant can be used for the aggregation using a coagulant.
• Known coagulants include aluminum salts, calcium salts, and magnesium salts.
• aluminum sulfate, alum represented by the general formula M'Al(SO 4 ) 2 ⁇ 12H 2 O (wherein M' is a monovalent cation other than lithium), calcium nitrate, and magnesium sulfate can be mentioned.
• Alum is preferred, and potassium alum, where M is potassium, is more preferred.
• base aggregation is preferred since aggregation is particularly likely to proceed.
• the particles of the present disclosure are melt-formable particles,
• the average particle size of the particles is 1 ⁇ m or less, the particles contain one or more fluorinated polymers,
• the fluorine-containing polymer contains TFE units, PAVE units, and compound (1) units, the content of PAVE units is 0.05 to 5.0 mol % based on all constitutional units of the fluorine-containing polymer, does not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is 100 ppm by mass or less based on the content of the fluorine-containing polymer;
• the content of (S1) is 1 to 10,000 ppb by mass, and the content of (S2) is 100 ppb by mass or less, based on the fluorine-containing polymer.
• M each independently represents a hydrogen atom, Na, K, or NH4 ; n represents 7 to 11; and m represents 8 to 12.
• the particles of the present disclosure can be obtained, for example, by the method for producing a fluoropolymer of the present disclosure. Alternatively, the particles of the present disclosure may be obtained by agglomerating particles from the aqueous dispersion of the present disclosure.
• melt-processible particles in the particles of the present disclosure is the same as that in the aqueous dispersions of the present disclosure, including preferred embodiments and scope thereof.
• the average particle size of the particles means a value obtained by photographing the particles with a scanning electron microscope, determining the particle sizes of five different particles from the obtained SEM image, and calculating the arithmetic average of the particle sizes.
• the particles of the present disclosure are preferably substantially free of a fluorine-containing emulsifier. Details of the fluorine-containing emulsifier are as described above.
• the particles of the present disclosure do not contain a fluorine-containing emulsifier, or the content of the fluorine-containing emulsifier is 100 ppm by mass or less, preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, and even more preferably 1 ppm by mass or less, based on the content of the fluorine-containing polymer.
• the content of the fluorinated emulsifier relative to the content of the fluorinated polymer can be determined by a method similar to the measurement method for the content of the fluorinated surfactant by liquid chromatography-mass spectrometry described in paragraphs [0364] to [0369] of WO 2021/045227.
• the particles of the present disclosure have a content of the compound represented by formula (S1) of 1 to 10,000 ppb by mass, and a content of the compound represented by formula (S2) of 100 ppb by mass or less, relative to the fluoropolymer.
• the compound represented by formula (S1) and the compound represented by formula (S2) are components that can be generated when the above-mentioned specific monomer (particularly TFE) is polymerized in the presence of a polymerization initiator, a chain transfer agent and an emulsifier.Therefore, in the method for producing a fluorine-containing polymer of the present disclosure, when no emulsifier is used, the amount of the compound represented by formula (S1) and the compound represented by formula (S2) generated can be suppressed, so that the content of these compounds can be easily set within the above-mentioned range.
• the content of the compound represented by formula (S1) relative to the fluoropolymer is preferably 10 ppb by mass or more relative to the fluoropolymer from the viewpoint of processability.
• the content of the compound represented by formula (S1) relative to the fluoropolymer is preferably 1,000 ppb by mass or less, and more preferably 300 ppb by mass or less, from the viewpoint of suppressing deterioration of physical properties such as heat resistance.
• the content of the compound represented by formula (S2) relative to the fluoropolymer is preferably 0.1 ppb by mass or more, and more preferably 1 ppb by mass or more, relative to the fluoropolymer from the viewpoint of processability.
• the content of the compound represented by formula (S2) relative to the fluoropolymer is preferably 50 ppb by mass or less, and more preferably 25 ppb by mass or less, from the viewpoint of suppressing deterioration of physical properties such as heat resistance.
• the content of the compound represented by formula (S1) in the fluoropolymer can be calculated by a method using a powder among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0710] to [0720] of WO 2018/181904.
• the content of the compound represented by formula (S2) in the fluoropolymer can be calculated by a method using a powder among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0721] to [0732] of WO 2018/181904.
• the particles of the present disclosure may be further subjected to a fluorination treatment to adjust the content of the compound represented by formula (S1).
• the fluorination treatment method may be the method described above. By fluorinating the particles of the present disclosure, the content of the compound represented by formula (S1) in the particles of the present disclosure can be reduced.
• the total number of functional groups per 106 carbon atoms in the main chain of the fluoropolymer of the particles of the present disclosure is preferably less than 100, more preferably 50 or less, and even more preferably 30 or less.
• the lower limit of the number of functional groups is 0.
• the functional group may be any of those mentioned above, and the method for measuring the number of functional groups is also as described above. ⁇ Applications> Since the particles of the present disclosure are substantially free of emulsifiers, they can easily be made into a dispersion in an organic solvent such as N-methylpyrrolidone or acetone.
• the particles of the present disclosure may be used in a powder composition.
• Example 1 is an embodiment, and Examples 2 and 3 are comparative examples. However, the present invention is not limited to these examples.
• the amounts of each component in the tables below are based on mass.
• 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.
• ⁇ Average particle size of particles in liquid> The raw material liquid was degassed for 5 minutes at room temperature (25°C), pressurized with nitrogen to 0.2 MPaG, and then purged to atmospheric pressure to obtain a sample for measurement.
• the particle size of the obtained sample was measured using a laser diffraction/scattering particle size distribution measuring device (Otsuka Electronics Co., Ltd., ELSZ) with the cumulative number set to 100, and measurement was started.
• D50 was calculated from the particle size measured in the range of 1 to 300 nm, and this was taken as the average particle size of the particles in the raw material liquid.
• the average particle size of the particles in the aqueous dispersion corresponding to the raw material liquid was measured in the same manner as in the raw material liquid, and was found to be the same as that of the particles in the raw material liquid.
• the aqueous dispersion corresponding to the raw material liquid means the aqueous dispersion A1 corresponding to the raw material liquid T2 in Example 1 described later.
• the average particle size (D50) of particles in each aqueous dispersion obtained using the aqueous dispersion corresponding to the raw material liquid was measured using a laser diffraction/scattering particle size distribution analyzer (Otsuka Electronics Co., Ltd., ELSZ).
• the range of particle sizes to be measured was not limited, unlike the method for measuring the average particle size of particles in the raw material liquid.
• the aqueous dispersion obtained using the aqueous dispersion corresponding to the raw material liquid in each example means aqueous dispersion 1 obtained using aqueous dispersion A1 in the case of Example 1 described later.
• ⁇ Average particle size of particles after drying> The aqueous dispersion containing the second fluoropolymer obtained in each example was coagulated, filtered, and then dried to obtain particles, which were then photographed using a scanning electron microscope (e.g., JSM-IT700HR InTouchScope, manufactured by JEOL Ltd.) The particle sizes of five different particles measured from the obtained SEM images were determined and then the arithmetic average was calculated.
• a scanning electron microscope e.g., JSM-IT700HR InTouchScope, manufactured by JEOL Ltd.
• ⁇ Content of compound represented by formula (S1)> The content of the compound represented by the above formula (S1) relative to the content of the fluoropolymer was calculated by a method using an aqueous dispersion or a powder composition, among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0710] to [0720] of WO 2018/181904.
• the apparatus used was an Agilent 1260 series HPLC/6460S, and the column used was an Imtakt cadenza CD-C18.
• ⁇ Content of compound represented by formula (S2)> The content of the compound represented by the above formula (S2) relative to the content of the fluoropolymer was calculated by a method using an aqueous dispersion or a powder composition among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs [0721] to [0732] of WO 2018/181904.
• the apparatus used was an Agilent 1260 series HPLC/6460S, and the column used was an Imtakt cadenza CD-C18.
• the raw material liquid T1 was freeze-coagulated and then filtered to obtain a fluoropolymer 1A, which was analyzed by NMR to find that the molar ratio of TFE units/PMVE units was 52/48 and the Tg was -5.9°C.
• raw material liquid T2 particles of fluoropolymer 1A (average particle size: 52 nm) were dispersed in an aqueous medium, and the content of fluoropolymer 1A was 0.4 mass % relative to the total mass of raw material liquid T2.
• aqueous dispersion A1 Ultrapure water (149 g), raw material liquid T2 (475 g), and t-BuOMe (0.5 g) were charged into a 1.0 L stainless steel pressure-resistant reactor to obtain aqueous dispersion A1.
• the aqueous dispersion A1 had a pH of 4.7, a viscosity of 1.1 mPa ⁇ s, and a thixotropic ratio of 1.0.
• CF 2 ⁇ CF-CF 2 -O-C 3 F 7 (M1, 2.3 g) was added to the aqueous dispersion A1, and the temperature was raised to 63° C. while stirring at 260 rpm.
• TFE was injected until the pressure in the reactor reached 1.3 MPaG, and an aqueous solution of ammonium persulfate (APS) (0.5 mass%, 5 mL) was added to start polymerization. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. 0.24 g of M1 was added every time 5 g of TFE was injected. When 170 g of TFE had been injected, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 470 minutes. After recovering the gas remaining in the reactor, the liquid was extracted. This liquid was designated as aqueous dispersion 1.
• APS ammonium persulfate
• the aqueous dispersion 1 was a dispersion in which particles (average particle diameter 267 nm) containing fluoropolymer 1A were dispersed in an aqueous medium, and had a solid content concentration of 21.0% by mass, a pH of 2.0, and a viscosity of 1.4 mPa ⁇ s.
• the obtained particles contained a first perfluoropolymer containing TFE units and PMVE units, and a second fluoropolymer containing TFE units and M1 units in the same particles.
• the ratio of the average particle diameter of the obtained particles to the average particle diameter of the particles of fluoropolymer 1A contained in the raw material liquid T2 was 5.1.
• the aqueous dispersion 1 had a content of fluorine-containing emulsifier relative to the total content of the first perfluoropolymer and the second fluoropolymer of less than 25 ppb by mass.
• the obtained particles were aggregated and dried to obtain Particle 1 (average particle size 252 nm).
• the MFR was 6.5 g/10 min.
• the particles contained a first perfluoropolymer containing TFE units and PMVE units and a second fluoropolymer containing TFE units and M1 units within the same particle, and the content of the first perfluoropolymer was 98.9% by mass, and the content of the second fluoropolymer was 1.1% by mass.
• the content of the fluorine-containing emulsifier in the particles 1 was less than 25 ppb by mass based on the total content of the first perfluoropolymer and the second fluoropolymer.
• particle 1 the content of the compound represented by the above formula (S1) was 190 ppb by mass, and the content of the compound represented by the above formula (S2) was less than 25 ppb by mass, relative to the total content of the first perfluoropolymer and the second fluoropolymer.
• Aqueous Dispersion 3 had a solids concentration of 22.0% by mass. The obtained particles were aggregated and dried to obtain Particles 3.
• the composition of Particles 3 was calculated by NMR, and the TFE unit/M1 unit ratio was 99/1 (molar ratio). The MFR was 1.5 g/10 min.
• Particle 3 had a fluorine-containing emulsifier content of 2000 ppb by mass relative to the content of the fluorine-containing polymer having TFE units and M1 units.
• the content of the compound represented by the above formula (S1) was 180 ppb by mass, and the content of the compound represented by the above formula (S2) was less than 25 ppb by mass, relative to the content of the fluoropolymer having TFE units and M1 units.
• the fluorinated particles 1 and 3 were press-molded at 340° C. to produce a film having a thickness of 200 ⁇ m. The film was scanned 16 times by a Fourier transform infrared spectrometer and analyzed to obtain an infrared absorption spectrum. The fluorinated particles 1 and 3 were placed in a vacuum oscillator and heated to 210° C. After evacuation, fluorine gas diluted to 20% by volume with nitrogen gas was introduced. After 10 hours, the inside of the reactor was sufficiently replaced with nitrogen gas to terminate the fluorination reaction and obtain completely fluorinated particles 1 and 3. The completely fluorinated particles 1 and 3 were press-molded at 340° C.
• Table 2 shows the absorption frequency, molar absorption coefficient and correction factor for a specific functional group such as --CF 2 H.
• the molar absorption coefficient of a specific functional group is determined from the FT-IR measurement data of a low molecular weight model compound.
• the absorption frequencies of -CH 2 CF 2 H, -CH 2 COF, -CH 2 COOH, -CH 2 COOCH 3 and -CH 2 CONH 2 are several tens of Kaiser (cm -1 ) lower than the respective absorption frequencies of -CF 2 H, -COF, -COOH (free and bonded), -COOCH 3 and -CONH 2 shown in the table.
• the number of --COF is the sum of the number of functional groups determined from the absorption peak at 1883 cm.sup. -1 due to --CF.sub.2 COF and the number of functional groups determined from the absorption peak at 1840 cm.sup. -1 due to --CH.sub.2 COF.
• the fluorinated particles 1 had less than 10 functional groups per 10 6 main chain carbon atoms of the first perfluoropolymer and the second fluoropolymer.
• the fluorinated particles 3 had less than 10 functional groups per 10 6 main chain carbon atoms of the fluorine-containing polymer having TFE units and M1 units. It was also found that all of the fluorinated particles did not foam when heated and had excellent heat resistance.
• Example 1 a fluorine-containing copolymer having excellent heat resistance equivalent to that of Example 3 was obtained without using a fluorine-containing emulsifier.
• Example 2 a fluorine-containing polymer could not be obtained without using a fluorine-containing emulsifier.
• composition disclosed herein can be obtained without using a fluorine-containing emulsifier, and is extremely useful in situations where the use of fluorine-containing emulsifiers is restricted.

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