Method for producing fluorine-containing polymer, aqueous dispersion, particles, and composition

Abstract

A composition which contains a first perfluoropolymer having a glass transition temperature of 10 DEG C or less and a second fluoropolymer that is different from the first perfluoropolymer and contains constituent units based on tetrafluoroethylene and a compound represented by formula (1), and wherein the content of the constituent units in the first perfluoropolymer and the content of the constituent units in the second fluoropolymer are less than the total content of the constituent units in the first perfluoropolymer and the total content of the constituent units in the second perfluoropolymer, and the content of the constituent units in the second perfluoropolymer is less than the total content of the constituent units in the second perfluoropolymer. The content of structural units based on perfluoro (alkyl vinyl ether) is 0.05-5.0 mol%. CF2 = CF-CF2-O-Rf... (1) In formula (1), Rf is a C1-10 perfluoroalkyl group, and an etheric oxygen atom may be present between carbon atoms of the perfluoroalkyl group.

Description

Technical Field

[0001] This invention relates to a method for manufacturing fluoropolymers, aqueous dispersions, and compositions. Background Technology

[0002] Because fluoropolymers such as tetrafluoroethylene copolymers have excellent heat resistance, chemical resistance, flame retardancy, and weather resistance, they are used in various industrial fields.

[0003] As a method for manufacturing fluoropolymers, an example is the method of emulsion polymerization of fluorinated monomers in an aqueous medium using a fluorinated emulsifier (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2007 / 046377 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] Because the method for manufacturing the fluoropolymer in Patent Document 1 uses an aqueous medium, it has a low environmental impact. However, since a large amount of fluorinated emulsifier, which is an essential component, remains in the aqueous dispersion obtained from polymerization, it is necessary to remove the fluorinated emulsifier depending on the application. Furthermore, in recent years, the use of fluorinated emulsifiers has tended to be restricted.

[0009] This disclosure is made against this background, and one of the technical problems to be solved by an embodiment of the present invention is to provide a composition containing a fluoropolymer with excellent heat resistance that does not require a fluorinated emulsifier.

[0010] Furthermore, one embodiment of the present invention aims to solve the technical problem of providing a method for manufacturing fluoropolymers that can produce fluoropolymers with excellent heat resistance without the need for fluorinated emulsifiers.

[0011] Furthermore, one embodiment of the present invention aims to solve the technical problem of providing an aqueous dispersion containing a fluoropolymer with excellent heat resistance.

[0012] Furthermore, one embodiment of the present invention aims to solve the technical problem of providing particles containing a fluoropolymer with excellent heat resistance.

[0013] Technical solutions adopted to solve technical problems

[0014] This disclosure includes the following forms.

[0015] [1]

[0016] A composition comprising

[0017] The first perfluoropolymer with a glass transition temperature below 10°C, and

[0018] A second fluoropolymer, distinct from the first perfluoropolymer, comprising structural units based on tetrafluoroethylene and compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether) structural units is 0.05–5.0 mol% relative to the total content of all structural units of the first and second perfluoropolymers. CF2=CF-CF2-O-Rf …(1) In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

[0019] [2]

[0020] The composition as described in [1], wherein both the first perfluoropolymer and the second fluoropolymer are free of functional groups, or the number of carbon atoms in the main chain of the first perfluoropolymer and the second fluoropolymer is equal to the number of carbon atoms in each of the 10... 6 The total number of functional groups is less than 100.

[0021] [3]

[0022] The composition as described in [1] or [2], wherein the first perfluoropolymer comprises a tetrafluoroethylene-based structural unit and a perfluoro(alkyl vinyl ether)-based structural unit.

[0023] [4]

[0024] The composition as described in [3], wherein, in the first perfluoropolymer, the number of perfluoro(alkyl vinyl ether) based structural units is 20 to 70 mol, relative to the total number of tetrafluoroethylene-based structural units and perfluoro(alkyl vinyl ether)-based structural units.

[0025] [5]

[0026] A method for manufacturing a fluoropolymer, comprising: The process of preparing an aqueous dispersion A comprising a first perfluoropolymer with a glass transition temperature below 10°C and an aqueous medium, and The process of polymerizing a monomer containing tetrafluoroethylene and a compound represented by formula (1) in an aqueous dispersion A to produce a second fluoropolymer that is different from the first perfluoropolymer. Before the monomer polymerization begins, the content of the first perfluoropolymer is 0.01–4.0% by mass relative to the total mass of aqueous dispersion A. Before the monomer begins polymerization, aqueous dispersion A contains no fluorinated emulsifier, or the content of fluorinated emulsifier is less than 100 ppm by mass relative to the total mass of aqueous dispersion A.

[0027] CF2=CF-CF2-O-Rf …(1)

[0028] In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

[0029] [6]

[0030] In the method for manufacturing fluoropolymers as described in [5], the amount of monomer used is 1 to 50 parts by mass relative to 100 parts by mass of aqueous medium.

[0031] [7]

[0032] The method for manufacturing fluoropolymers as described in [5] or [6], wherein, The process of preparing aqueous dispersion A is a process of preparing aqueous dispersion A containing particles of the first perfluoropolymer and an aqueous medium. The process of manufacturing the second fluoropolymer involves polymerizing monomers to produce a second fluoropolymer that is different from the first perfluoropolymer, and manufacturing particles comprising the first perfluoropolymer and the second fluoropolymer. The ratio of the average particle size of the particles containing the first perfluoropolymer and the second perfluoropolymer to the average particle size of the particles of the first perfluoropolymer is greater than 2.

[0033] [8]

[0034] The method for manufacturing fluoropolymers as described in [5] or [6], wherein the viscosity of the aqueous dispersion A is below 2.0 mPa·s.

[0035] [9]

[0036] The method for manufacturing a fluoropolymer as described in any one of [5] to [8], wherein the thixotropic ratio of the aqueous dispersion A is 0.9 to 1.2.

[0037]

[10]

[0038] A method for manufacturing a fluoropolymer as described in any one of [5] to [9], wherein the monomer is polymerized in the presence of a polymerization initiator.

[0039]

[11]

[0040] The method for manufacturing a fluoropolymer as described in any one of [5] to

[10] further includes a step of fluorinating the first perfluoropolymer and the second fluoropolymer.

[0041]

[12]

[0042] An aqueous dispersion, It is an aqueous dispersion containing an aqueous medium and melt-formable particles, wherein, The average particle size is less than 1 μm. The particles contain one or more fluoropolymers. Fluoropolymers comprise structural units based on tetrafluoroethylene, structural units based on perfluoro(alkyl vinyl ethers), and structural units based on compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether) structural unit relative to the total number of structural units of the fluoropolymer is 0.05–5.0 mol%. The particle content relative to the total mass of the aqueous dispersion is 1-50% by mass. The aqueous dispersion is free of fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of fluorinated polymers. CF2=CF-CF2-O-Rf …(1) In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

[0043]

[13]

[0044] The aqueous dispersion described in

[12] has a viscosity of 0.8 to 2.0 mPa·s.

[0045]

[14]

[0046] A type of particle, It consists of particles that can be melted and shaped, among which, The average particle size is less than 1 μm. The particles contain one or more fluoropolymers. Fluoropolymers comprise structural units based on tetrafluoroethylene, structural units based on perfluoro(alkyl vinyl ethers), and structural units based on compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether) structural unit relative to the total number of structural units of the fluoropolymer is 0.05–5.0 mol%. The particles do not contain fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of fluorinated polymers. Compared to fluoropolymers, the content of the compound represented by formula (S1) is 1 to 10,000 ppb by mass, while the content of the compound represented by formula (S2) is less than 100 ppb by mass. CF2=CF-CF2-O-Rf …(1) Formula (S1): H-(CF2) n -COOM Formula (S2): H-(CF2) m -SO3M In formulas (S1) and (S2), M independently represents a hydrogen atom, Na, K or NH4, n represents 7 to 11, and m represents 8 to 12.

[0047] Invention Effects

[0048] According to one embodiment of the present invention, a composition comprising a fluoropolymer with excellent heat resistance is provided without the need for a fluoroemulsifier.

[0049] Furthermore, according to one embodiment of the present invention, a method for manufacturing a fluoropolymer that can produce a fluoropolymer with excellent heat resistance without the need for a fluorinated emulsifier is provided.

[0050] Furthermore, according to one embodiment of the present invention, an aqueous dispersion comprising a fluoropolymer with excellent heat resistance is provided.

[0051] Furthermore, according to one embodiment of the present invention, particles comprising a fluoropolymer with excellent heat resistance are provided. Detailed Implementation

[0052] In this disclosure, the numerical range represented by “~” includes the values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0053] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced with the upper or lower limit of another numerical range described in different levels. Furthermore, the upper or lower limit of the numerical ranges described in this specification can also be replaced with the values ​​shown in the embodiments.

[0054] In this disclosure, when multiple substances equivalent to each component of the composition are present in the composition, unless otherwise expressly defined, the amount of each component in the composition refers to the total amount of the multiple substances.

[0055] In this disclosure, a combination of two or more preferred forms is a more preferred form.

[0056] In this disclosure, the term "process" refers not only to an independent process, but also to a process whose expected goal can be achieved when it cannot be clearly distinguished from other processes.

[0057] [Composition]

[0058] The composition disclosed herein contains a first perfluoropolymer with a glass transition temperature below 10°C, and a second fluoropolymer different from the first perfluoropolymer, comprising structural units based on tetrafluoroethylene (hereinafter also referred to as "TFE units") and structural units based on a compound represented by formula (1) (hereinafter also referred to as "compound (1) units"). The content of structural units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE units") is 0.05 to 5.0 mol% relative to the total content of all structural units of the first and second fluoropolymers.

[0059] CF2=CF-CF2-O-Rf …(1)

[0060] In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

[0061] The compositions disclosed herein contain a first perfluoropolymer and a second fluoropolymer, and the content of PAVE units is 0.05 to 5.0 mol% relative to the total content of all structural units of the first perfluoropolymer and the second fluoropolymer, thus exhibiting excellent heat resistance.

[0062] In this regard, Patent Document 1 does not focus on compositions containing two or more fluorinated copolymers.

[0063] (First perfluoropolymer)

[0064] The first type of perfluoropolymer is a perfluoropolymer with a glass transition temperature below 10°C.

[0065] In this disclosure, "perfluoropolymer" refers to a polymer in which all hydrogen atoms bonded to carbon atoms in the polymer's structural units are replaced by fluorine atoms. "Fluoropolymer" refers to a polymer in which some or all of the hydrogen atoms bonded to carbon atoms in the polymer's structural units are replaced by fluorine atoms.

[0066] The glass transition temperature (hereinafter also referred to as "Tg") of the first perfluoropolymer is below 10°C.

[0067] From the viewpoint of efficient adsorption of specific monomers, as described later, the Tg of the first perfluoropolymer is preferably below 5°C, more preferably below 3°C, and even more preferably below 0°C.

[0068] From the viewpoint of thermal stability after molding and processing, the Tg of the first perfluoropolymer is preferably above -50°C, more preferably above -45°C, and even more preferably above -40°C.

[0069] The Tg of the first perfluoropolymer was determined by differential scanning calorimetry (DSC).

[0070] For example, Tg was measured using a NEXTA DSC600 manufactured by High Technology Co., Ltd. Specifically, 5 mg of the sample was measured in an aluminum sample pan, and the sample was heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere. Then, it was cooled to -60°C at a rate of 10°C / min. After reaching the specified temperature, it was heated again to 100°C at a rate of 10°C / min. Tg was estimated from the inflection point confirmed by this second heating operation.

[0071] As a method to bring the Tg of the first perfluoropolymer within the above-mentioned range, for example, methods for adjusting the type and amount of monomers used in the manufacture of the first perfluoropolymer can be cited.

[0072] From the viewpoint that it is easy to adjust Tg to the above range and to have better heat resistance, the first perfluoropolymer preferably contains TFE unit and PAVE unit.

[0073] From the viewpoint of excellent polymerization reactivity when manufacturing the first perfluoropolymer, the monomer represented by formula (2) is preferred by PAVE.

[0074] CF2 = CF-OR f1 …(1)

[0075] In equation (2), R f1 This refers to perfluoroalkyl groups with 1 to 10 carbon atoms. From the viewpoint of superior polymerization reactivity, R... f1 The carbon number is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3.

[0076] Perfluoroalkyl groups can be linear or branched.

[0077] Specific examples of PAVE include 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").

[0078] From the viewpoint that the second fluoropolymer can be manufactured more efficiently, PAVE is preferably PMVE or PPVE, and more preferably PMVE.

[0079] When the first perfluoropolymer contains TFE units and PAVE units, from the viewpoint of easily adjusting Tg to the above range, the content of 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%, relative to the total content of TFE units and PAVE units.

[0080] The first perfluoropolymer may contain structural units based on monomers other than TFE and PAVE. From the viewpoint of more efficient manufacturing of the second fluoropolymer, the percentage of structural units based on other monomers relative to all structural units of the first perfluoropolymer is preferably 20.0 mol% or less, more preferably 15.0 mol% or less. The first perfluoropolymer is further preferably substantially free of structural units based on other monomers.

[0081] "Substantially free of units based on other monomers" means that the content of units based on other monomers is less than 0.01 mol% relative to all structural units of the first perfluoropolymer, more preferably 0.00 mol%.

[0082] In the case of structural units based on other monomers, hexafluoropropylene is preferred as the other monomer.

[0083] (Second fluoropolymer)

[0084] The second fluoropolymer is a fluoropolymer that is different from the first perfluoropolymer.

[0085] The second fluoropolymer contains TFE units and compound (1) units.

[0086] CF2=CF-CF2-O-Rf …(1)

[0087] In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

[0088] The number of carbons in Rf is preferably 2 to 8, more preferably 3 to 8.

[0089] Rf can be linear, branched, or contain ring structures.

[0090] As an Rf, for example, -(CF2) can be enumerated. m CF3 and -(CF2) r1 -O-(CF2) r2 CF3.

[0091] m is an integer from 0 to 9.

[0092] 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.

[0093] Wherein, m is preferably an integer from 1 to 7, and more preferably an integer from 1 to 5.

[0094] r1 is preferably an integer from 1 to 6, and more preferably an integer from 1 to 4.

[0095] r2 is preferably an integer from 1 to 6, and more preferably an integer from 1 to 4.

[0096] In particular, compound (1) is preferably CF2=CF-CF2-OCF2CF2CF3.

[0097] From the viewpoint of heat resistance, in the second fluoropolymer, the content of compound (1) unit 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%, relative to the total content of TFE unit and compound (1) unit.

[0098] Although the second fluoropolymer may contain structural units based on monomers other than TFE and compound (1), from the viewpoint of heat resistance, the structural units based on other monomers are preferably less than 10.0 mol%, more preferably less than 5.0 mol%, relative to all structural units of the second fluoropolymer. The second fluoropolymer is further preferably substantially free of structural units based on other monomers.

[0099] "Substantially free of units based on other monomers" means that the content of units based on other monomers is less than 0.01 mol% relative to all structural units of the second fluoropolymer, more preferably 0.00 mol%.

[0100] In the case of structural units based on other monomers, other monomers may be listed as, for example, fluoroolefins such as hexafluoropropylene (HFP), PAVE, etc. (except for TFE and compound (1)); acid anhydrides such as itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, etc.

[0101] In the compositions disclosed herein, 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%, relative to the total content of all structural units of the first perfluoropolymer and the second fluoropolymer. Since the content of PAVE units is 0.05 to 5.0 mol%, the heat resistance is excellent.

[0102] In the solid component content of the composition disclosed herein, the content of the first perfluoropolymer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more.

[0103] In the compositions disclosed herein, the content of the first perfluoropolymer is preferably 10% by mass or less, more preferably 5% by mass or less.

[0104] In the solid component content of the composition disclosed herein, the content of the second fluoropolymer is preferably 90% by mass or more, more preferably 95% by mass or more.

[0105] In the compositions disclosed herein, the content of the second fluoropolymer is preferably 99.99% by mass or less, more preferably 99.9% by mass or less.

[0106] From the viewpoint of polymerization stability, in the compositions disclosed herein, the content of the first perfluoropolymer is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, relative to the total content of the first perfluoropolymer and the second perfluoropolymer. From the viewpoint of heat resistance, the content of the first perfluoropolymer is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total content of the first perfluoropolymer and the second perfluoropolymer.

[0107] From the perspective of superior heat resistance, neither the first perfluoropolymer nor the second fluoropolymer contains functional groups, or the number of carbon atoms in the main chain of the first perfluoropolymer and the second fluoropolymer is greater than that of each other (per 10). 6 The total number of functional groups is preferably less than 100, more preferably less than 50, and even more preferably less than 30.

[0108] The types of functional groups and the number of functional groups can be characterized by infrared spectrophotometry.

[0109] The number of functional groups was determined by the following method.

[0110] A 200 μm thick film was prepared by pressing a first perfluoropolymer and a second fluoropolymer at 340 °C. The film was then scanned 16 times using a Fourier transform infrared spectrometer to obtain its infrared absorption spectrum.

[0111] In the fluorination process described later, the first perfluoropolymer and the second fluoropolymer undergo a prolonged fluorination treatment to obtain fully fluorinated first and second perfluoropolymers. The fully fluorinated first and second perfluoropolymers are then press-formed at 340°C to prepare a fully fluorinated film with a thickness of 200 μm. The fully fluorinated film is scanned 16 times using a Fourier transform infrared spectrometer to obtain the fundamental spectrum.

[0112] The number of carbons per 10 in the main chain is calculated from the absorption peaks of specific functional groups appearing in the difference spectrum between the obtained infrared absorption spectrum and the fundamental spectrum using the following formula (A). 6 The number of functional groups N.

[0113] N = I × K / t …(A)

[0114] I: Absorbance

[0115] K: Correction coefficient

[0116] t: Membrane thickness (mm)

[0117] Table 1 shows the absorption frequencies, molar absorptivity, and correction factors for specific functional groups such as -CF2H. The molar absorptivity for specific functional groups was determined by FT-IR measurements of low-molecular-weight model compounds.

[0118] [Table 1]

[0119] Among the copolymers, the absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of Kaiser (cm) lower than the absorption frequencies of -CF2H, -COF, -COOH (without -COOH and bonded -COOH), -COOCH3, and -CONH2 shown in the table. -1 ).

[0120] For example, the -COF number is derived from the absorption frequency of -CF2COF, which is 1883 cm⁻¹. -1 The number of functional groups obtained from the absorption peak and the absorption frequency of -CH2COF at 1840 cm⁻¹ -1 The total number of functional groups obtained from the absorption peaks.

[0121] The functional groups in the first perfluoropolymer and the second fluoropolymer are functional groups present at the ends of the main chain or side chain of each polymer and functional groups present in the main chain or side chain.

[0122] As functional groups, examples include -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2, and -CH2OH.

[0123] The number of functional groups can be the sum of -CF=CF2, -CF2H, -COF, -COOH, -COOCH3, -CONH2, and -CH2OH.

[0124] The aforementioned functional groups are introduced, for example, through chain transfer agents or polymerization initiators used in the manufacture of the first perfluoropolymer and the second fluoropolymer. Furthermore, the aforementioned functional groups are introduced into the side chain ends of the polymer by polymerizing monomers containing the functional groups.

[0125] By fluorinating polymers with functional groups, the number of carbon atoms in the main chain of the first perfluoropolymer and the second fluoropolymer can be increased by 10 per 1000 carbon atoms. 6 The total number of functional groups is less than 100. That is, the compositions disclosed herein are preferably compositions comprising a fluorinated polymer.

[0126] The compositions disclosed herein may be particles, powder compositions comprising multiple particles, or liquid compositions. Furthermore, when the compositions disclosed herein are liquid compositions, they may be dispersions of particles in water or organic solvents.

[0127] When the composition disclosed herein is in the form of particles, it is preferably a particle (hereinafter also referred to as "the particle") 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.

[0128] In the case of a powder composition or a liquid composition disclosed herein, it preferably contains the present particles.

[0129] The average particle size of this particle is preferably 1 μm or less, more preferably 700 nm or less, and even more preferably 500 nm or less. From the viewpoint of cohesion, the lower limit of the average particle size is preferably 30 nm.

[0130] Furthermore, the compositions disclosed herein can be granules or molded articles such as films or tubes.

[0131] In the case where the composition disclosed herein is a particle or powder composition, the average particle size refers to the arithmetic mean obtained by taking a picture of the particle with a scanning electron microscope and determining the particle size of five different particles from the obtained SEM image.

[0132] In the case where the composition disclosed herein is a liquid composition, the average particle size refers to the particle size (D50) at the point where the cumulative volume reaches 50% on the cumulative curve obtained by measuring the particle size distribution by laser diffraction and scattering with the total volume of the particle group as 100%.

[0133] When the composition disclosed herein is a dispersion, from the viewpoint of ease of operation, the viscosity of the dispersion is preferably 0.8 to 2.0 mPa·s, more preferably 1.0 to 1.5 mPa·s.

[0134] The viscosity of the dispersion is the value measured using a Type B viscometer at room temperature (25°C) and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0135] The compositions disclosed herein are preferably substantially free of fluorinated emulsifiers. Details of fluorinated emulsifiers are described below.

[0136] The compositions disclosed herein are free of fluorinated emulsifiers, or the content of fluorinated emulsifiers relative to the total content of the first perfluoropolymer and the second fluoropolymer 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.

[0137] The content of fluorinated emulsifier relative to the total content of the first perfluoropolymer and the second fluoropolymer can be determined by the same method as the method for determining the content of fluorinated surfactants by liquid chromatography-mass spectrometry as described in International Publication No. 2021 / 045227, paragraphs

[0364] to

[0369] .

[0138] From a processability point of view, in the compositions disclosed herein, 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, more preferably 10 ppb by mass or more, relative to the fluoropolymer.

[0139] From the viewpoint of suppressing the decline in the heat resistance and other physical properties of the compositions disclosed herein, the content of the compound represented by the following formula (S1) in the compositions disclosed herein 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.

[0140] From a processability point of view, in the compositions disclosed herein, 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, more preferably 1 ppb by mass or more, relative to the fluoropolymer.

[0141] From the viewpoint of suppressing the decline in the heat resistance and other physical properties of the compositions disclosed herein, the content of the compound represented by the following formula (S2) in the compositions disclosed herein is preferably 50 ppb by mass or less, more preferably 25 ppb by mass or less, relative to the total content of the first perfluoropolymer and the second fluoropolymer.

[0142] Formula (S1): H-(CF2) n -COOM

[0143] Formula (S2): H-(CF2) m -SO3M

[0144] In formulas (S1) and (S2), M independently represents a hydrogen atom, Na, K or NH4, n represents 7 to 11, and m represents 8 to 12.

[0145] 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 the method using an aqueous dispersion as described in paragraphs

[0710] to

[0720] of International Publication No. 2018 / 181904.

[0146] 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 the method using an aqueous dispersion as described in International Publication No. 2018 / 181904, paragraphs

[0721] to

[0732] .

[0147] The compositions disclosed herein can be fluorinated to adjust the content of the compound represented by formula (S1). Examples of fluorination methods are described below.

[0148] Fluorination of the composition disclosed herein can reduce the content of the compound represented by formula (S1) in the particles of this disclosure.

[0149] [Manufacturing method of fluoropolymers]

[0150] The method for manufacturing the fluoropolymer disclosed herein includes: a step of preparing an aqueous dispersion A comprising a first perfluoropolymer with a Tg below 10°C and an aqueous medium; and a step of polymerizing a monomer (hereinafter also referred to as a "specific monomer") comprising TFE and compound (1) in the aqueous dispersion A to manufacture a second fluoropolymer different from the first perfluoropolymer. Before the polymerization of the specific monomer begins, the content of the first perfluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion A. Before the polymerization of the specific monomer begins, the aqueous dispersion A does not contain a fluorinated emulsifier, or the content of the fluorinated emulsifier is less than 100 ppm by mass relative to the total mass of the aqueous dispersion A.

[0151] In this disclosure, "before the polymerization of a specific monomer begins" means just before the point at which the polymerization of the specific monomer begins. Here, "the point at which polymerization begins" can be categorized as the point at which the specific monomer and the polymerization initiator coexist in the reactor after the polymerization temperature has been reached, or the point at which the polymerization temperature has been reached in the reactor after the specific monomer and the polymerization initiator have coexisted in the reactor.

[0152] In the method for manufacturing fluoropolymers disclosed herein, monomers containing TFE and HFP are polymerized in an aqueous dispersion A containing a first perfluoropolymer with a Tg below 10°C and an aqueous medium. This allows for the efficient manufacture of a second fluoropolymer even when the content of the fluorinated emulsifier is below 100 ppm by mass relative to the total mass of the aqueous dispersion A.

[0153] The method for manufacturing the fluoropolymer disclosed herein preferably includes, in sequence, a step of preparing an aqueous dispersion A, and a step of manufacturing a second fluoropolymer that is different from the first perfluoropolymer.

[0154] <Preparation process of aqueous dispersion A>

[0155] The method for manufacturing the fluoropolymer disclosed herein includes a step of preparing an aqueous dispersion A comprising a first perfluoropolymer with a Tg below 10°C and an aqueous medium (hereinafter also referred to as the "aqueous dispersion A preparation step").

[0156] (First perfluoropolymer)

[0157] The details of the first perfluoropolymer with a Tg below 10°C contained in the aqueous dispersion A prepared in the aqueous dispersion A preparation process are as described above.

[0158] The first perfluoropolymer is preferably dispersed in an aqueous medium in the form of particles.

[0159] From the viewpoint that the second fluoropolymer can be manufactured more efficiently, the average particle size of the first perfluoropolymer is preferably 1 to 200 nm, more preferably 10 to 150 nm, and even more preferably 30 to 120 nm.

[0160] The average particle size of the first perfluoropolymer refers to the particle size (D50) at the point where the cumulative volume reaches 50% of the total volume of the particle cluster, obtained by measuring the particle size distribution using laser diffraction and scattering.

[0161] The first perfluoropolymer can be manufactured, for example, by polymerizing monomers (preferably a mixture of monomers comprising TFE and compound (1)) in a polymerization solvent in the presence of a polymerization initiator. This yields a dispersion of the first perfluoropolymer dispersed in particulate form in the polymerization solvent.

[0162] From the viewpoint of efficient polymerization, the pH of the reaction system containing the monomer and polymerization solvent before the start of polymerization is preferably 6.5 or higher, more preferably 7.0 or higher, when the monomer is polymerized to obtain the first perfluoropolymer. From the viewpoint of improving the stability of the first perfluoropolymer, the pH of the reaction system is preferably 10.5 or lower, more preferably 10 or lower.

[0163] The pH value of the reaction system can be adjusted using a pH adjuster. Examples of pH adjusters that can be included in the aqueous dispersion A (described later) include ammonia, with ammonia being preferred.

[0164] The dispersion of the first perfluoropolymer thus obtained can be used directly as the aqueous dispersion A described above. Alternatively, other aqueous media can be added to the dispersion of the first perfluoropolymer before it can be used as the aqueous dispersion A described above. Furthermore, the first perfluoropolymer can be dispersed in other aqueous media by displacing the solvent before it can be used as the aqueous dispersion A described above.

[0165] As the polymerization initiator used in the manufacture of the first perfluorinated polymer, a water-soluble polymerization initiator is preferred, and more preferably: persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate; peroxides such as bis(butanoic acid) peroxide; azo compounds such as azobisisobutyramidine dihydrochloride, and even more preferably persulfates, especially ammonium persulfate.

[0166] Examples of polymerization solvents include water or a mixture of water and a water-soluble organic solvent. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0167] In the method for manufacturing the first perfluoropolymer, a heating step can be performed after obtaining the dispersion of the first perfluoropolymer.

[0168] (Aqueous medium)

[0169] The aqueous medium contained in the aqueous dispersion A prepared in the aqueous dispersion A preparation process can be the polymerization solvent used in the manufacture of the first perfluoropolymer.

[0170] The specific example of the aqueous medium contained in the aqueous dispersion A is the same as the specific example of the polymerization solvent used in the manufacture of the first perfluoropolymer.

[0171] Before the polymerization of the monomers used for the polymerization of the second perfluoropolymer begins, the content of the aqueous medium relative to the total mass of the aqueous dispersion A is preferably 60.0 to 99.9% by mass, more preferably 96 to 99.9% by mass, and even more preferably 98.0 to 99.9% by mass.

[0172] (Other ingredients)

[0173] Aqueous dispersion A may also contain other components besides the first perfluoropolymer and the aqueous medium.

[0174] Other components that may be included in aqueous dispersion A include chain transfer agents, emulsifiers other than fluorinated emulsifiers, pH adjusters, and waxes.

[0175] In this disclosure, an emulsifier refers to a compound having both hydrophilic and hydrophobic sites.

[0176] Examples of emulsifiers include hydrocarbon-containing surfactants, fluorinated emulsifiers, and polymeric emulsifiers.

[0177] Neither the first perfluoropolymer nor the second fluoropolymer is an emulsifier.

[0178] The emulsifier can be either ionic or nonionic.

[0179] Hydrocarbon-containing surfactants are surfactants that contain a hydrocarbon group. More specifically, a hydrocarbon-containing surfactant only needs to contain a hydrocarbon group, which can be replaced by halogen atoms such as fluorine and chlorine atoms. In hydrocarbon-containing surfactants, preferably 75% or more of the atoms or monovalent groups bonded to the carbon atoms of the hydrocarbon group are hydrogen atoms, more preferably 85% or more, and even more preferably 95% or more.

[0180] Hydrocarbon surfactants and siloxane surfactants can be listed as examples. Hydrocarbon surfactants are surfactants that do not contain silicon atoms, whose atoms bonded to carbon atoms in hydrocarbon groups or whose monovalent groups are 100% hydrogen atoms, and therefore do not contain halogen atoms such as chlorine and fluorine atoms. Siloxane surfactants are hydrocarbon surfactants that have hydrophobic groups comprising a siloxane skeleton containing a large number of siloxane units.

[0181] Anionic hydrocarbon surfactants can be cited as examples of hydrocarbon surfactants.

[0182] Anionic hydrocarbon surfactants refer to hydrocarbon surfactants that have negatively charged hydrophilic parts such as carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphonic acid groups, and phosphate groups, and hydrocarbon parts such as alkyl groups that are hydrophobic.

[0183] As an example of anionic hydrocarbon surfactants, Resolution Performance Products offers highly branched C10 tertiary carboxylic acids as part of its Versatic (registered trademark) 10 line. Another example of anionic hydrocarbon surfactants is BASF's linear alkyl polyether sulfonate sodium salt, offered as part of its Avanel (registered trademark) S series.

[0184] Sodium dodecyl sulfate can also be cited as an anionic hydrocarbon surfactant.

[0185] Another example of anionic hydrocarbon surfactants is Lankropol (registered trademark) K8300, a sulfosuccinate surfactant available from Akzo Nobel SurfaceChemistry LLC.

[0186] Nonionic hydrocarbon surfactants can also be cited as examples of hydrocarbon surfactants.

[0187] Although nonionic hydrocarbon surfactants do not possess charged groups, they do have hydrophobic portions, which are mostly long-chain hydrocarbons. Examples of water-soluble functional groups in nonionic hydrocarbon surfactants include polyoxyethylene chains obtained from the polymerization of ethylene oxide. Examples of nonionic hydrocarbon surfactants include block copolymers containing various types of polyoxyalkylene blocks, such as polyoxyethylene and polyoxypropylene groups.

[0188] As nonionic hydrocarbon surfactants, the surfactants described in paragraphs

[0043] to

[0052] of Japanese Patent Publication No. 2016-537499 can be cited.

[0189] As siloxane surfactants, examples include those described in U.S. Patent No. 6,841,616 (Wille et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0190] Anionic fluorinated surfactants can be cited as examples of fluorinated emulsifiers.

[0191] Examples of anionic fluorinated surfactants include surfactants containing fluorine atoms in which the total carbon number of the portion excluding the anionic group is 20 or less, and fluorinated surfactants in which the molecular weight of the anionic portion is 800 or less. Furthermore, the term "anionic portion" refers to the portion of the fluorinated surfactant in which the cationic group has been removed.

[0192] Examples of polymeric emulsifiers include water-soluble polymers with hydrophilic side chains. Such polymeric emulsifiers may include polymers comprising structural units based on compounds having polymerically reactive sites and hydrophilic groups. Furthermore, examples may include polymers obtained by post-processing polymers comprising structural units based on compounds having groups that can become hydrophilic, such as through hydrolysis.

[0193] Specific examples of chain transfer agents include ethyl acetate, methanol, ethanol, tert-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane. From the viewpoint that the molecular weight can be controlled in small amounts, tert-butyl methyl ether or methane is preferred as a chain transfer agent, and tert-butyl methyl ether is more preferred.

[0194] Specific examples of pH adjusters include inorganic salts. Examples of inorganic salts include phosphates such as disodium hydrogen phosphate and sodium dihydrogen phosphate; and carbonates such as sodium bicarbonate and sodium carbonate. More preferred examples of phosphates include disodium hydrogen phosphate dihydrate and disodium hydrogen phosphate dodecahydrate.

[0195] Specific examples of waxes include Parafffin Wax-155 and Parafffin Wax-150 (both manufactured by Nippon Seiwa Co., Ltd.).

[0196] When the aqueous dispersion A contains a chain transfer agent, 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. Furthermore, the amount of chain transfer agent used is preferably 0.1 to 20.0 parts by mass relative to 100 parts by mass of the specific monomer described later, more preferably 0.1 to 15.0 parts by mass, and even more preferably 0.1 to 10.0 parts by mass.

[0197] When the aqueous dispersion A contains emulsifiers other than fluorinated emulsifiers, the content of emulsifiers other than fluorinated emulsifiers is preferably 0.01 to 5.0 parts by weight relative to 100 parts by weight of the aqueous medium.

[0198] When the aqueous dispersion A contains a pH adjuster, the content of the pH adjuster is preferably 0.01 to 3.0 parts by mass relative to 100 parts by mass of the aqueous medium.

[0199] From the viewpoint that the second fluoropolymer can be stably polymerized, the pH value of the aqueous dispersion A is preferably 1.0 or higher, more preferably 2.0 or higher. From the viewpoint that the second fluoropolymer can be stably polymerized, the pH value of the aqueous dispersion A is preferably 11 or lower, more preferably 10.5 or lower.

[0200] When the aqueous dispersion A contains wax, the wax content is preferably 1 to 10 parts by mass relative to 100 parts by mass of the aqueous medium.

[0201] From the viewpoint that the second fluoropolymer can be stably polymerized, 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 that the second fluoropolymer can be stably polymerized, the viscosity of the aqueous dispersion A is preferably 0.85 mPa·s or more, more preferably 0.9 mPa·s or more.

[0202] From the viewpoint that the second fluoropolymer can be stably polymerized, the thixotropic ratio of the aqueous dispersion A is preferably 0.9 or more, more preferably 0.95 or more. From the viewpoint that the second fluoropolymer can be stably polymerized, the thixotropic ratio of the aqueous dispersion A is preferably 1.2 or less, more preferably 1.1 or less.

[0203] The viscosity of aqueous dispersion A is the value measured using a type B viscometer at room temperature (25°C) and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0204] The thixotropic ratio of aqueous dispersion A is obtained by dividing the viscosity of aqueous dispersion A measured at 30 rpm by the viscosity of aqueous dispersion A measured at 60 rpm.

[0205] <Second Fluoropolymer Manufacturing Process>

[0206] The method for manufacturing the fluoropolymer disclosed herein includes a step of polymerizing a specific monomer in an aqueous dispersion A to manufacture a second fluoropolymer that is different from the first perfluoropolymer (hereinafter also referred to as the "second fluoropolymer manufacturing step").

[0207] Details of the second fluoropolymer are as described above.

[0208] Before the polymerization of a specific monomer begins, the content of the first perfluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion A, preferably 0.05 to 3.0% by mass, more preferably 0.1 to 2.0% by mass. If the content of the first perfluoropolymer is 0.01% by mass or more, the polymerization stability (productivity) is excellent; if the content of the first perfluoropolymer is 4.0% by mass or less, the polymer obtained by polymerization (i.e., the mixture of the first perfluoropolymer and the second fluoropolymer) has excellent heat resistance.

[0209] Before the polymerization of a specific monomer begins, the aqueous dispersion A is free of fluorinated emulsifiers, or the content of fluorinated emulsifiers relative to the total mass of the aqueous dispersion A is less than 100 ppm by mass, preferably less than 50 ppm by mass, more preferably less than 25 ppm by mass, and even more preferably less than 5 ppm by mass. As a lower limit, 0 ppm by mass can be cited as an example.

[0210] In the method for manufacturing fluoropolymers disclosed herein, a second fluoropolymer can be manufactured efficiently even when the content of the fluorinated emulsifier is below 100 ppm by mass.

[0211] From the viewpoint of polymerization stability, the concentration of fluoride ions relative to the total mass of aqueous dispersion A is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, before the polymerization of a particular monomer begins. As a lower limit, 0 ppm by mass can be cited as an example.

[0212] As an example of a method to achieve the above-mentioned concentration of fluoride ions, an example can be given of a method for removing sulfate ions using an anion exchange resin during the manufacture of the first perfluoropolymer.

[0213] Here, fluoride ions are generated by the reaction of a polymerization initiator (e.g., ammonium persulfate) with a monomer used in the manufacture of the first fluoropolymer, which is sometimes contained in an aqueous dispersion.

[0214] From the viewpoint of suppressing the coloration of the second fluoropolymer, the concentration of sulfate ions relative to the total mass of the aqueous medium in the aqueous dispersion is preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, before the polymerization of a particular monomer begins. As a lower limit, 0 ppm by mass can be cited as an example.

[0215] As an example of a method to achieve the above-mentioned concentration of sulfate ions, an example can be given of a method for removing sulfate ions using an anion exchange resin during the manufacture of the first perfluoropolymer.

[0216] Here, sulfate ions, for example, originate from the polymerization initiator (especially ammonium persulfate) used in the manufacture of the first perfluoropolymer, and may be contained in the aqueous dispersion containing the first perfluoropolymer. It is speculated that keeping the sulfate ion content below 10 ppm by mass (especially below 5 ppm by mass) can suppress the formation of heat-sensitive end groups on the second fluoropolymer, thereby suppressing the coloring of the second fluoropolymer.

[0217] From the viewpoint of suppressing the aggregation of the second fluoropolymer, the concentration of ammonium ions relative to the total mass of the aqueous medium in the aqueous dispersion is preferably 20 ppm by mass or less, more preferably 10 ppm by mass or less, before the polymerization of a particular monomer begins. As a lower limit, 0 ppm by mass can be cited as an example.

[0218] As an example of a method to achieve the above-mentioned concentration of ammonium ions, an example can be given of a method for removing ammonium ions using a cation exchange resin during the manufacture of the first perfluoropolymer.

[0219] Here, ammonium ions, for example, originate from the initiator (especially ammonium persulfate) used in the manufacture of the first perfluoropolymer, and may be contained in the aqueous dispersion containing the first perfluoropolymer. It is speculated that keeping the ammonium ion content below 20 ppm by mass reduces the ionic strength in the aqueous medium, resulting in improved manufacturing efficiency of the second fluoropolymer.

[0220] (Specific monomer)

[0221] The specific monomer contains TFE and compound (1).

[0222] The preferred form of compound (1) is as described above.

[0223] From the viewpoint of heat resistance, the amount of 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%, relative to the total amount of TFE and compound (1).

[0224] The specific monomer may contain monomers other than TFE and compound (1). From the viewpoint of heat resistance, the amount of other monomers used is preferably less than 10.0 mol% relative to the total amount of the specific monomer, more preferably less than 5.0 mol%. The specific monomer is further preferably substantially free of other monomers.

[0225] "Substantially free of other monomers" means that the amount of other monomers used relative to the total amount of a particular monomer used is less than 0.01 mol%, which can be 0.00 mol%.

[0226] Other monomers include, for example, fluorinated alkenes such as HFP and PAVE (except for TFE and compound (1)); acid anhydrides such as itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.

[0227] The amount of a specific monomer used is preferably 1 to 50 parts by mass relative to 100 parts by mass of the aqueous medium contained in the aqueous dispersion A, more preferably 1 to 40 parts by mass, and even more preferably 1 to 30 parts by mass.

[0228] (Polymerization initiator)

[0229] In the second fluoropolymer manufacturing process, it is preferable to polymerize specific monomers in the presence of a polymerization initiator.

[0230] As polymerization initiators, oil-soluble free radical initiators, water-soluble free radical initiators, or water-soluble redox catalysts are preferred.

[0231] Oil-soluble free radical initiators include tert-butyl peroxypentanoate (hereinafter also known as "PBPV") and diisopropyl peroxydicarbonate (hereinafter also known as "IPP"), among other oil-soluble organic peroxides.

[0232] Examples of water-soluble free radical initiators include: ammonium persulfate, potassium persulfate, and other persulfates; succinic acid peroxide, glutaric acid peroxide, tert-butyl hydroperoxide (hereinafter also known as "TBHP"), and other water-soluble organic peroxides.

[0233] As a water-soluble redox catalyst, a combination of oxidants such as hydrobromic acid or its salts, hydrochloric acid or its salts, persulfate or its salts, permanganate or its salts, and hydrogen peroxide with reducing agents such as sulfurous acid or its salts, bisulfite or its salts, thiosulfate or its salts, organic acids, and inorganic salts is preferred. Potassium persulfate and ammonium persulfate are preferred as persulfates. Sodium sulfite is preferred as a sulfite. Combinations of sulfate anions, sulfite anions, chloride anions, and metal ions can be included as inorganic salts. Transition metal ions are preferred, including ions of manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver, with iron ions being the most preferred. Ferrous sulfate is preferred as an inorganic salt.

[0234] The polymerization initiator is preferably an oil-soluble free radical initiator or a water-soluble free radical initiator. From the viewpoint of being able to manufacture fluoropolymers more efficiently, an oil-soluble free radical initiator is preferred, and an oil-soluble organic peroxide is even more preferred.

[0235] Polymerization initiators can be used alone or in combination of two or more.

[0236] The amount of polymerization initiator used relative to the amount of a specific monomer is preferably 1 to 1000 ppm by mass, more preferably 5 to 750 ppm, and even more preferably 10 to 500 ppm.

[0237] (Other ingredients)

[0238] During the polymerization of a particular monomer, components other than those mentioned above (hereinafter also referred to as "other components") may be used. A specific example of an other component is a reducing agent.

[0239] The preferred amount of other components is 1 to 2000 ppm relative to the amount of a specific monomer used per 100 parts by weight.

[0240] (Manufacturing method)

[0241] The second fluoropolymer obtained in the second fluoropolymer manufacturing process can be copolymerized with the first perfluoropolymer.

[0242] Specific monomers are added to the reaction system (i.e., the polymerization vessel) using conventional methods. For example, the specific monomers can be added to the reaction system continuously or intermittently to bring the polymerization pressure to a specified level. Alternatively, the specific monomers can be dissolved in an aqueous medium, and the resulting solution can be added to the reaction system continuously or intermittently.

[0243] When using a polymerization initiator, the initiator can be added to the reaction system all at once or in batches.

[0244] The polymerization temperature is preferably 10–95°C, and more preferably 15–90°C.

[0245] The polymerization pressure is preferably 0.5 to 4.0 MPaG, more preferably 0.6 to 3.5 MPaG.

[0246] The polymerization time is preferably 90 to 1000 minutes, more preferably 90 to 700 minutes, when batch processing is used.

[0247] Since it is assumed that the first perfluoropolymer is in particulate form, it is presumed that during the polymerization of a specific monomer, the specific monomer polymerizes within or near the particles of the first perfluoropolymer. Therefore, in the method for manufacturing the fluoropolymer disclosed herein, particles comprising the first perfluoropolymer and the second fluoropolymer are generated. That is, it is presumed that the second fluoropolymer is obtained in the form of particles comprising the first perfluoropolymer and the second fluoropolymer. In this case, an aqueous dispersion comprising particles comprising the first perfluoropolymer and the second fluoropolymer is obtained by dispersing them in the aforementioned aqueous medium.

[0248] In the method for manufacturing fluoropolymers disclosed herein, it is preferable to obtain particles comprising a first perfluoropolymer and a second fluoropolymer.

[0249] That is, the preferred method for manufacturing the fluoropolymer of this disclosure is a method for manufacturing the following fluoropolymer, comprising: The process of preparing an aqueous dispersion A containing particles of a first perfluoropolymer with a glass transition temperature below 10°C and an aqueous medium, and The process of polymerizing monomers containing tetrafluoroethylene and perfluoro(alkyl vinyl ether) in an aqueous dispersion A to produce particles containing a first perfluoropolymer and a second fluoropolymer different from the first perfluoropolymer. Before the monomer polymerization begins, the content of the first perfluoropolymer is 0.01–4.0% by mass relative to the total mass of aqueous dispersion A. Before the monomer begins polymerization, aqueous dispersion A contains no fluorinated emulsifier, or the content of fluorinated emulsifier is less than 100 ppm by mass relative to the total mass of aqueous dispersion A.

[0250] From the viewpoint of polymerization stability, the average particle size of the particles containing the first perfluoropolymer and the second fluoropolymer is preferably 1 μm or less, 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 containing the first perfluoropolymer and the second fluoropolymer is preferably 30 nm.

[0251] In the method for manufacturing fluoropolymers disclosed herein, the average particle size is determined by laser diffraction scattering, and the particle size distribution is calculated using the total volume of the particle group as 100%. The particle size at the point where the cumulative volume reaches 50% on the cumulative curve is obtained.

[0252] The first perfluoropolymer is in particulate form. When particles comprising the first and second perfluoropolymers are obtained in the method for manufacturing the fluoropolymer disclosed herein, the ratio of the average particle size of the particles comprising the first and second perfluoropolymers to the average particle size of the particles comprising the first perfluoropolymer is preferably 2 or more, more preferably 3 or more. From the viewpoint of polymerization stability, the average particle size ratio is preferably 10 or less, more preferably 8 or less. If the above ratio is 2 or more, particles with excellent heat resistance reflecting the physical properties of the second fluoropolymer can be obtained.

[0253] <Fluorination Process>

[0254] The method for manufacturing fluoropolymers disclosed herein preferably further includes a step of fluorinating the first perfluoropolymer and the second fluoropolymer (hereinafter also referred to as the "fluorination step").

[0255] There are no particular limitations on the fluorination method; it can be carried out using methods known in the art. For example, fluorination can be performed by contacting the first perfluoropolymer and the second fluoropolymer with fluorine gas.

[0256] Fluorine gas can be diluted with an inert gas before use.

[0257] Examples of inert gases include rare gases such as helium, neon, and argon, as well as nitrogen. Nitrogen or helium is preferred, and nitrogen is more preferred from an economic point of view. The proportion of fluorine is preferably 10 to 60% by volume in a total of 100% by volume of fluorine and inert gases.

[0258] The fluorination treatment temperature is, for example, 100–250°C.

[0259] The fluorination treatment time is, for example, 1 to 15 hours.

[0260] The functional groups contained in the first perfluoropolymer and the second fluoropolymer are fluorinated through a fluorination process. Fluorination improves heat resistance.

[0261] The first perfluoropolymer and the second fluoropolymer have a main chain carbon number of 10 6 The total number of functional groups is preferably less than 100, more preferably less than 50, and even more preferably less than 30. The lower limit for the number of functional groups is 0.

[0262] [Aqueous dispersion]

[0263] The aqueous dispersion disclosed herein is an aqueous dispersion containing an aqueous medium and melt-formable particles, wherein the average particle size is less than 1 μm, the particles contain one or more fluoropolymers, the fluoropolymers contain TFE units, PAVE units, and compound (1) units, the content of PAVE units is 0.05 to 5.0 mol% relative to all structural units of the fluoropolymer, the content of particles is 1 to 50% by mass relative to the total mass of the aqueous dispersion, the aqueous dispersion does not contain fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 10 ppm by mass relative to the content of the fluoropolymers.

[0264] The aqueous dispersion of this disclosure can be obtained, for example, by the method for manufacturing the fluoropolymer of this disclosure.

[0265] The aqueous dispersion A described above is an aqueous dispersion obtained during the manufacturing process of the fluoropolymer disclosed herein, and is different from the aqueous dispersion disclosed herein.

[0266] <Particles that can be melted and shaped>

[0267] The aqueous dispersion disclosed herein contains particles capable of being melt-formed.

[0268] In this disclosure, "capable of melt forming" means a melt flow rate (MFR) of 0.1 to 1000 g / 10 min.

[0269] The MFR of the particles is preferably 0.1 to 100 g / 10 min, more preferably 1 to 80 g / 10 min.

[0270] In this disclosure, the MFR is determined by measuring the mass of water flowing out of an orifice with a diameter of 2 mm and a length of 8 mm within 10 minutes under conditions of 372°C and a load of 49 N, in accordance with ASTM D3307.

[0271] The average particle size is less than 1 μm, preferably less than 700 nm from the viewpoint of dispersibility, and more preferably less than 500 nm. From the viewpoint of cohesion, the lower limit of the average particle size is preferably 30 nm.

[0272] In this disclosure, the average particle size is determined by laser diffraction and scattering, and the particle size distribution is calculated using the total volume of the particle group as 100%. The particle size at the point where the cumulative volume reaches 50% on the cumulative curve is obtained.

[0273] From the viewpoint of dispersion stability, the particle content is 1 to 50% by mass, preferably 2 to 45% by mass, and more preferably 3 to 40% by mass, relative to the total mass of the aqueous dispersion of this disclosure.

[0274] The particles contained in the aqueous dispersion of this disclosure comprise one or more fluoropolymers.

[0275] When the particles contain two or more fluoropolymers, the particles may contain any fluoropolymers that contain TFE units, PAVE units and compound (1) units, or may contain fluoropolymers that do not contain TFE units, PAVE units and compound (1) units.

[0276] When the particles contain two or more fluoropolymers, one of the fluoropolymers may not contain all of the TFE unit, PAVE unit, and compound (1) unit. For example, the particles may contain a fluoropolymer containing both TFE and PAVE units, and a fluoropolymer containing both TFE and compound (1) units.

[0277] From the viewpoint of heat resistance, the content of compound (1) unit 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%, relative to the total content of TFE unit and compound (1) unit.

[0278] Furthermore, when the particles contain two or more fluoropolymers, it is acceptable as long as the particles can be melt-formed, even if one of the fluoropolymers in the particles cannot be melt-formed.

[0279] The content of PAVE units relative to all structural units of the fluoropolymer is 0.05 to 5.0 mol%, preferably 0.1 to 4.0 mol%, more preferably 0.1 to 3.0 mol%. Because the content of PAVE units is 0.05 to 5.0 mol%, it exhibits excellent heat resistance.

[0280] When the particles contain two or more fluoropolymers, "all structural units of the fluoropolymers" refers to all structural units in the two or more fluoropolymers.

[0281] In the PAVE unit, the PAVE is preferably the monomer represented by the above formula (2).

[0282] The content of the first perfluoropolymer in the particles is preferably 0.01% by mass or more, more preferably 0.1% by mass or more.

[0283] The content of the first perfluoropolymer in the particles is preferably 10% by mass or less, more preferably 5% by mass or less.

[0284] The content of the second fluoropolymer in the particles is preferably 90% by mass or more, more preferably 95% by mass or more.

[0285] 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.

[0286] From the viewpoint of improving physical properties such as heat resistance, the proportion of the first perfluoropolymer in the particles is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, relative to the total content of the first perfluoropolymer and the second perfluoropolymer.

[0287] From the viewpoint of improving physical properties such as heat resistance, the proportion of the first perfluoropolymer in the particles is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total content of the first perfluoropolymer and the second perfluoropolymer.

[0288] From the perspective of superior heat resistance, PAVE is the preferred choice for PMVE.

[0289] The particles preferably comprise the first perfluoropolymer and the second fluoropolymer described above. Details of the first perfluoropolymer and the second fluoropolymer are as described above.

[0290] <Aqueous Media>

[0291] Specific examples of the aqueous medium contained in the aqueous dispersion of this disclosure are the same as specific examples of the aqueous medium used in the manufacture of the first perfluoropolymer described above.

[0292] The content of the aqueous medium relative to the total mass of the aqueous dispersion of the present disclosure is preferably 50-99% by mass, more preferably 60-99% by mass, and even more preferably 70-99% by mass.

[0293] <Other>

[0294] The aqueous dispersions disclosed herein are preferably substantially free of fluorinated emulsifiers. Details of fluorinated emulsifiers are described above.

[0295] The aqueous dispersion disclosed herein is free of fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of fluorinated polymers, preferably less than 10 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 1 ppm by mass.

[0296] The content of fluorinated emulsifier relative to the content of fluorinated polymer can be determined by the same method as the method for determining the content of fluorinated surfactant by liquid chromatography-mass spectrometry described in International Publication No. 2021 / 045227, paragraphs

[0364] to

[0369] .

[0297] From a processability point of view, the viscosity of the aqueous dispersion disclosed herein is preferably 0.8 to 2.0 mPa·s, more preferably 1.0 to 1.5 mPa·s.

[0298] The viscosity of an aqueous dispersion is measured using a Type B viscometer at room temperature (25°C) and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0299] From the viewpoint of stabilizing the fluoropolymer in the aqueous dispersion, the content of the compound represented by the following formula (S1) of the fluoropolymer in the aqueous dispersion of the present disclosure is preferably 1 ppb by mass or more, more preferably 10 ppb by mass or more, relative to the fluoropolymer.

[0300] From the viewpoint of reduced physical properties, the content of the compound represented by the following formula (S1) of the fluoropolymer in the aqueous dispersion of this disclosure 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.

[0301] From the viewpoint of stabilizing the fluoropolymer in the aqueous dispersion, the content of the compound represented by the following formula (S2) of the fluoropolymer in the aqueous dispersion of the present disclosure is preferably 0.1 ppb by mass or more, more preferably 1 ppb by mass or more, relative to the fluoropolymer.

[0302] From the viewpoint of reduced physical properties, the content of the compound represented by the following formula (S2) of the fluoropolymer in the aqueous dispersion of this disclosure is preferably 50 ppb by mass or less, more preferably 25 ppb by mass or less.

[0303] Formula (S1): H-(CF2) n -COOM

[0304] Formula (S2): H-(CF2) m -SO3M

[0305] In formulas (S1) and (S2), M independently represents a hydrogen atom, Na, K or NH4, n represents 7 to 11, and m represents 8 to 12.

[0306] The content of the compound represented by formula (S1) of the fluoropolymer can be calculated by the method of using an aqueous dispersion in the determination method using a liquid chromatography-mass spectrometry analyzer described in International Publication No. 2018 / 181904, paragraphs

[0710] to

[0720] .

[0307] The content of the compound represented by formula (S2) relative to the fluoropolymer can be calculated by the method using an aqueous dispersion as described in paragraphs

[0721] to

[0732] of International Publication No. 2018 / 181904.

[0308] The compounds represented by formula (S1) and formula (S2) are components that may be generated during the polymerization of the aforementioned specific monomers (especially TFE) in the presence of a polymerization initiator, a chain transfer agent, and a fluorinated emulsifier. Therefore, in the method for manufacturing the fluorinated polymer disclosed herein, since the amount of compounds represented by formula (S1) and formula (S2) can be suppressed without using a fluorinated emulsifier, the content of these compounds is easily kept within the aforementioned range.

[0309] <Uses>

[0310] As described above, the aqueous dispersion of this disclosure does not require a fluorinated emulsifier, and therefore can easily be obtained by solvent displacement using organic solvents such as N-methylpyrrolidone and acetone.

[0311] For example, by mixing the aqueous dispersion of this disclosure with an organic solvent and dehydrating it by evaporation or by using anhydrous sodium sulfate, a dispersion of the organic solvent can be obtained.

[0312] Although the aqueous dispersions disclosed herein do not contain fluorinated emulsifiers, the fluorinated polymers remain stably dispersed. Therefore, they are suitable for coating applications, adhesives, etc.

[0313] Furthermore, by agglomerating particles from the aqueous dispersion of this disclosure, a powder can be obtained.

[0314] Examples of coagulation methods include freeze coagulation, acid coagulation, alkali coagulation, and coagulation using coagulants, but these are not limited to.

[0315] In the case of freeze-coagulation, the coagulation temperature is preferably -20 to 0°C. The coagulation time is preferably 1 hour or more, more preferably 2 hours or more.

[0316] In the event of acid coagulation, it is preferable to add an acid-containing solution to the aqueous dispersion of this disclosure. Examples of acids added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, and hydrofluoric acid, with hydrochloric acid being preferred. The concentration of the acid in the acid-containing solution is preferably 0.1–50% by mass, more preferably 1–30% by mass, and even more preferably 1–10% by mass.

[0317] As a method for alkali coagulation, it is preferable to add an alkaline solution to the aqueous dispersion of this disclosure. Examples of alkaline substances added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, with sodium hydroxide being preferred. The concentration of the alkaline solution is preferably 0.1–50% by mass, more preferably 1–30% by mass, and even more preferably 1–10% by mass.

[0318] As a coagulation process using a coagulant, known coagulants can be used. Examples of known coagulants include ammonium salts, calcium salts, and magnesium salts. Specifically, examples include aluminum sulfate, alum represented by the general formula M'Al(SO4)2·12H2O (where 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.

[0319] As a coagulation method, alkaline coagulation is preferred from the perspective that coagulation is particularly easy to carry out.

[0320] [particle]

[0321] The particles disclosed herein are particles capable of being melted and shaped, wherein, The average particle size is less than 1 μm. The particles contain one or more fluoropolymers. Fluoropolymers contain TFE units, PAVE units, and compound (1) units. The content of PAVE units is 0.05–5.0 mol% relative to the total structural units of the fluoropolymer. The particles do not contain fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of fluorinated polymers. Compared to fluoropolymers, the content of (S1) is 1–10,000 ppb by mass, and the content of (S2) is less than 100 ppb by mass. Formula (S1): H-(CF2)n -COOM Formula (S2): H-(CF2) m -SO3M In formulas (S1) and (S2), M independently represents a hydrogen atom, Na, K or NH4, n represents 7 to 11, and m represents 8 to 12.

[0322] The particles of this disclosure can be obtained, for example, by the method for manufacturing the fluoropolymer of this disclosure. Alternatively, the particles of this disclosure can be obtained by agglomerating particles from an aqueous dispersion of this disclosure.

[0323] <Particles that can be melted and shaped>

[0324] The definition of particles capable of being melt-formed in this disclosure includes their preferred morphology and range, which are the same as those in the aqueous dispersions of this disclosure.

[0325] In this disclosure, the average particle size refers to the arithmetic mean obtained by taking a picture of the particle with a scanning electron microscope and calculating the particle size of five different particles from the obtained SEM image.

[0326] <Other>

[0327] The particles disclosed herein are preferably substantially free of fluorinated emulsifiers. Details of fluorinated emulsifiers are as described above.

[0328] The particles disclosed herein do not contain fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of fluorinated polymers, preferably less than 10 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 1 ppm by mass.

[0329] The content of fluorinated emulsifier relative to the content of fluorinated polymer can be determined by the same method as the method for determining the content of fluorinated surfactant by liquid chromatography-mass spectrometry described in International Publication No. 2021 / 045227, paragraphs

[0364] to

[0369] .

[0330] In the particles disclosed herein, the content of the compound represented by formula (S1) is 1 to 10,000 ppb by mass relative to the fluoropolymer, and the content of the compound represented by formula (S2) is less than 100 ppb by mass.

[0331] The compounds represented by formula (S1) and formula (S2) are components that may be generated when the aforementioned specific monomers (especially TFE) are polymerized in the presence of a polymerization initiator, a chain transfer agent, and an emulsifier. Therefore, in the method for manufacturing fluoropolymers disclosed herein, since the amount of compounds represented by formula (S1) and formula (S2) can be suppressed without the use of an emulsifier, the content of these compounds is easily kept within the aforementioned range.

[0332] From a processability point of view, in the particles of this disclosure, the content of the compound represented by formula (S1) of the fluoropolymer is preferably 10 ppb or more by mass relative to the fluoropolymer.

[0333] From the viewpoint of suppressing the decline in physical properties such as heat resistance, the content of the compound represented by formula (S1) of the fluoropolymer in the particles disclosed herein is preferably 1000 ppb by mass or less, more preferably 300 ppb by mass or less.

[0334] From a processability point of view, in the particles of this disclosure, the content of the compound represented by formula (S2) of the fluoropolymer is preferably 0.1 ppb by mass or more, more preferably 1 ppb by mass or more, relative to the fluoropolymer.

[0335] From the viewpoint of suppressing the decline in physical properties such as heat resistance, the content of the compound represented by formula (S2) of the fluoropolymer in the particles disclosed herein is preferably 50 ppb by mass or less, more preferably 25 ppb by mass or less.

[0336] The content of the compound represented by formula (S1) relative to the fluoropolymer can be calculated by the method of using powder in the determination method using a liquid chromatography-mass spectrometry analyzer described in International Publication No. 2018 / 181904, paragraphs

[0710] to

[0720] .

[0337] The content of the compound represented by formula (S2) relative to the fluoropolymer can be calculated by the method of using powder in the determination method using a liquid chromatography-mass spectrometry analyzer described in International Publication No. 2018 / 181904, paragraphs

[0721] to

[0732] .

[0338] The powder disclosed herein can be further subjected to fluorination treatment to adjust the content of the compound represented by formula (S1). Examples of fluorination treatment methods described above can be cited.

[0339] Fluorination of the particles of this disclosure can reduce the content of the compound represented by formula (S1) in the particles of this disclosure.

[0340] Furthermore, the fluoropolymers of the particles disclosed herein have a main chain carbon number of 10 6The total number of functional groups is preferably less than 100, more preferably less than 50, and even more preferably less than 30. The lower limit for the number of functional groups is 0.

[0341] As functional groups, the above-mentioned functional groups can be listed, and the method for determining the number of functional groups is also as described above.

[0342] <Uses>

[0343] The particles disclosed herein are substantially free of emulsifiers, and therefore dispersions in organic solvents such as N-methylpyrrolidone and acetone are readily obtained.

[0344] The particles disclosed herein can be used as powder compositions.

[0345] Example

[0346] The present invention will now be described in detail with examples. Example 1 is an embodiment, and Examples 2 and 3 are comparative examples. However, the present invention is not limited to these examples. Furthermore, the mixing amounts of each component in the table below are expressed on a mass basis.

[0347] [Measurement and Evaluation Methods]

[0348] The various measurement and evaluation methods are described below.

[0349] <Glass transition temperature (Tg)>

[0350] Tg was measured using a NEXTA DSC600 manufactured by Advanced Technology Co., Ltd. Specifically, 5 mg of the sample was measured in an aluminum sample pan, and the sample was heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere. Then, it was cooled to -60°C at a rate of 10°C / min. After reaching the specified temperature, it was heated again to 100°C at a rate of 10°C / min. Tg was estimated from the inflection point confirmed by this second heating operation.

[0351] <Average particle size in liquid>

[0352] The feed solution was degassed at room temperature (25°C) for 5 minutes, pressurized to 0.2 MPaG with nitrogen, and then purged to atmospheric pressure to obtain the sample for measurement. Using a laser diffraction-scattering particle size distribution measuring device (Otsuka Electronics Co., Ltd., ELSZ), with the integration count set to 100, the particle size of the obtained sample was measured. The D50 was calculated from the particle sizes measured in the range of 1–300 nm and used as the average particle size in the feed solution.

[0353] Furthermore, if the average particle size of the particles in the aqueous dispersion corresponding to the raw material liquid is determined using the same method as that used for the raw material liquid, then it will be the same as the average particle size of the particles in the raw material liquid. Here, in the case of Example 1 described later, the aqueous dispersion corresponding to the raw material liquid refers to the aqueous dispersion A1 corresponding to the raw material liquid T2.

[0354] Furthermore, the average particle size (D50) of the aqueous dispersions obtained using the aqueous dispersion corresponding to the raw material liquid was measured using a laser diffraction-scattering particle size distribution measuring apparatus (Otsuka Electronics Co., Ltd., ELSZ). The particle size range of the measured object differs from that measured using the method for the average particle size in the raw material liquid and is not limited thereto. Here, in the case of Example 1 described later, the aqueous dispersion obtained using the aqueous dispersion corresponding to the raw material liquid refers to aqueous dispersion 1 obtained using aqueous dispersion A1.

[0355] <Average particle size after drying>

[0356] The aqueous dispersions containing the second fluoropolymer obtained in each example were coagulated, filtered, and dried. The obtained particles were then imaged using a scanning electron microscope (e.g., JSM-IT700HR InTouchScope manufactured by Nippon Electron Ltd.). The particle sizes of the five different particles measured from the obtained SEM images were determined and the arithmetic mean was taken.

[0357] <Proportion of structural units in the polymer>

[0358] The proportions of each structural unit in the polymer are determined by... 19 The results were obtained from F-NMR analysis and infrared absorption spectroscopy analysis.

[0359] <Content of fluorinated emulsifiers>

[0360] The content of fluorinated emulsifier relative to the content of fluorinated polymer is determined by the same method as the method for determining the content of fluorinated surfactant by liquid chromatography-mass spectrometry described in International Publication No. 2021 / 045227, paragraphs

[0364] to

[0369] .

[0361] <The content of the compound represented by formula (S1)>

[0362] The content of the compound represented by the above formula (S1) relative to the content of the fluoropolymer was calculated using the method described in International Publication No. 2018 / 181904, paragraphs

[0710] to

[0720] , using a liquid chromatography-mass spectrometry analyzer and an aqueous dispersion or powder composition. Furthermore, an Agilent 1260 series HPLC / 6460S was used, and an Imtakt Cadenza CD-C18 column was employed.

[0363] <The content of the compound represented by formula (S2)>

[0364] The content of the compound represented by the above formula (S2) relative to the content of the fluoropolymer was calculated using the method described in International Publication No. 2018 / 181904, paragraphs

[0721] to

[0732] , using a liquid chromatography-mass spectrometry analyzer and an aqueous dispersion or powder composition. Furthermore, an Agilent 1260 series HPLC / 6460S was used, and an Imptakt Cadenza CD-C18 column was employed.

[0365] [Preparation of raw material liquid T1]

[0366] Ultrapure water (717g), PMVE (50g), and TFE (8g) were added to a 1.3L stainless steel pressure reactor, and the temperature was raised to 90°C while stirring at 500 rpm. Then, an ammonium persulfate aqueous solution (3.6% by mass, 5mL) was added to initiate polymerization. The pressure inside the reactor decreased as polymerization began, so TFE was added to maintain a constant pressure. After adding 1g of TFE, the reactor was cooled to terminate the polymerization reaction. Residual gas was recovered from the reactor, and the liquid was extracted. This liquid was designated as feed liquid T1.

[0367] After the raw material liquid T1 was frozen and coagulated, it was filtered. The obtained fluoropolymer 1A was analyzed by NMR. The results showed that the TFE unit / PMVE unit ratio was 52 / 48 (molar ratio) and the Tg was -5.9℃.

[0368] [Preparation of raw material liquid T2]

[0369] Add 20g of Dowex Monosphere 650C (cation exchange resin manufactured by DuPont) to the above feed solution T1 (490g). After stirring for 60 minutes, filter to separate the feed solution and ion exchange resin. Add 20g of Purolite A300 (anion exchange resin manufactured by Purolite) to the filtered feed solution. After stirring for 60 minutes, filter to separate the feed solution and ion exchange resin, obtaining feed solution T2.

[0370] In feed solution T2, fluoropolymer 1A particles (average particle size 52 nm) are dispersed in an aqueous medium, and the content of fluoropolymer 1A is 0.4% of the total mass of feed solution T2.

[0371] <Example 1>

[0372] Ultrapure water (149 g), feed solution T2 (475 g), and t-BuOMe (0.5 g) were added to a 1.0 L stainless steel pressure reactor to obtain an aqueous dispersion A1. Aqueous dispersion A1 had a pH of 4.7, a viscosity of 1.1 mPa·s, and a thixotropic ratio of 1.0. CF2=CF-CF2-O-C3F7 (M1, 2.3 g) was added to aqueous dispersion A1, and the mixture was heated to 63 °C while stirring at 260 rpm. TFE was added until the reactor pressure reached 1.3 MPaG, and then ammonium persulfate (APS) aqueous solution (0.5% by mass, 5 mL) was added to initiate polymerization. The pressure inside the reactor decreased as polymerization began, so TFE was added to maintain a constant pressure. 0.24 g of M1 was added for every 5 g of TFE added. After adding 170 g of TFE, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 470 minutes.

[0373] After recovering the residual gas in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 1. Aqueous dispersion 1 is a dispersion containing particles (average particle size 267 nm) of fluoropolymer 1A dispersed in an aqueous medium, with a solids concentration of 21% by mass, a pH of 2.0, and a viscosity of 1.4 mPa·s. The obtained particles contain a first perfluoropolymer containing TFE and PMVE units, and a second fluoropolymer containing TFE and M1 units within the same particle. The average particle size of the obtained particles is 5.1 times the average particle size of the fluoropolymer 1A particles contained in the feed liquid T2. In aqueous dispersion 1, the content of fluorinated emulsifier is less than 25 ppb by mass relative to the combined content of the first and second perfluoropolymers.

[0374] The obtained particles were agglomerated and dried to obtain particle 1 (average particle size 252 nm). The composition of particle 1 was calculated using NMR, and the result was TFE unit / M1 unit / PMVE unit = 98.5 / 1 / 0.5 (molar ratio). The MFR was 6.5 g / 10 min.

[0375] The particles contain a first perfluoropolymer containing TFE and PMVE units and a second fluoropolymer containing TFE and M1 units within the same particle, with the first perfluoropolymer comprising 98.9% by mass and the second fluoropolymer comprising 1.1% by mass.

[0376] In particle 1, the content of fluorinated emulsifier is less than 25 ppb by mass relative to the combined content of the first perfluoropolymer and the second fluoropolymer.

[0377] In particle 1, the content of the compound represented by formula (S1) is 190 ppb by mass relative to the total content of the first perfluoropolymer and the second fluoropolymer, and the content of the compound represented by formula (S2) is less than 25 ppb by mass.

[0378] <Example 2>

[0379] Ultrapure water (624 g), CF2=CF-CF2-O-C3F7 (M1, 2.3 g), and t-BuOMe (0.5 g) were added to a 1.0 L stainless steel pressure reactor to obtain an aqueous dispersion C. The aqueous dispersion C was heated to 63 °C while stirring at 260 rpm. TFE was added until the reactor pressure reached 1.3 MPaG, and then 0.5% (w / v) 5 mL of APS aqueous solution was added to initiate polymerization. The pressure inside the reactor decreased as polymerization began, so TFE was added to maintain a constant pressure. 0.24 g of M1 was added for every 5 g of TFE added. After adding 50 g of TFE, the reactor was cooled to terminate the polymerization reaction. The polymerization time was 300 minutes.

[0380] After recovering the residual gas in the reactor, the liquid was extracted, but it all condensed, making it impossible to obtain an aqueous dispersion of fluoropolymer particles in an aqueous medium.

[0381] <Example 3>

[0382] Ultrapure water (608 g), fluorinated emulsifier (ammonium salt of C2F5OCF2CF2OCF2COOH, 30% by mass, 16 g), CF2=CF-CF2-O-C3F7 (M1, 2.3 g), and t-BuOMe (0.5 g) were added to a 1.0 L stainless steel pressure reactor to obtain aqueous dispersion D. Aqueous dispersion D was heated to 63 °C while stirring at 260 rpm. TFE was added until the reactor pressure reached 1.3 MPaG, and APS aqueous solution (0.5% by mass, 5 mL) was added to start polymerization. The pressure inside the reactor decreased as polymerization began, so TFE was added to maintain a constant pressure. 0.24 g of M1 was added for every 5 g of TFE added. After adding 170 g of TFE, the reactor was cooled to stop the polymerization reaction. The polymerization time was 210 minutes.

[0383] After recovering the residual gas in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 3. The solid content of aqueous dispersion 3 is 22.0% by mass.

[0384] The obtained particles were condensed and dried to obtain particle 3. The composition of particle 3 was calculated using NMR, and the result was TFE unit / M1 unit = 99 / 1 (molar ratio). The MFR was 1.5 g / 10 min.

[0385] In particle 3, the content of fluorinated emulsifier is 2000 ppb by mass relative to the content of fluorinated polymers with TFE units and M1 units.

[0386] In particle 3, relative to the content of the fluoropolymer with TFE and M1 units, the content of the compound represented by formula (S1) is 180 ppb by mass, and the content of the compound represented by formula (S2) is less than 25 ppb by mass.

[0387] [evaluate]

[0388] (Fluorination treatment)

[0389] Particles 1 and 3 were added to a vacuum vibrating reactor and heated to 210°C. After evacuation, fluorine gas diluted to 20% by volume with nitrogen was introduced. After 2 hours, the reactor was completely replaced with nitrogen to end the fluorination reaction. The fluorinated particles were analyzed, and the number of terminal functional groups was calculated.

[0390] (10 carbons per main chain) 6 (Number of functional groups)

[0391] Fluorinated particles 1 and 3 were pressurized at 340℃ to form a 200 μm thick membrane. The membrane was scanned 16 times using a Fourier transform infrared spectrometer to obtain its infrared absorption spectrum. Fluorinated particles 1 and 3 were then added to a vacuum vibratory reactor and heated to 210℃. After evacuation, fluorine gas diluted to 20% by volume with nitrogen was introduced. After 10 hours, the reactor was completely replaced with nitrogen to terminate the fluorination reaction, yielding fully fluorinated particles 1 and 3. The fully fluorinated particles 1 and 3 were then pressurized at 340℃ to form a 200 μm thick fully fluorinated membrane. The fully fluorinated membrane was scanned 16 times using a Fourier transform infrared spectrometer to obtain its fundamental spectrum.

[0392] The number of carbon atoms in the main chain of fluorinated particles 1 and 3 per 1000 atoms is calculated from the absorption peaks of specific functional groups appearing in the difference spectrum between the obtained infrared absorption spectrum and the fundamental spectrum using the following formula (A). 6 The number of functional groups N.

[0393] N = I × K / t …(A)

[0394] I: Absorbance

[0395] K: Correction coefficient

[0396] t: Membrane thickness (mm)

[0397] Table 2 shows the absorption frequencies, molar absorptivity, and correction factors for specific functional groups such as -CF2H. The molar absorptivity of specific functional groups was determined by FT-IR measurements of low-molecular-weight model compounds.

[0398] [Table 2]

[0399] Among the copolymers, the absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are tens of Kaiser (cm) lower than the absorption frequencies of -CF2H, -COF, -COOH (without -COOH and bonded -COOH), -COOCH3, and -CONH2 shown in the table. -1 ).

[0400] For example, the -COF number is derived from the absorption frequency of -CF2COF, which is 1883 cm⁻¹. -1 The number of functional groups obtained from the absorption peak and the absorption frequency of -CH2COF at 1840 cm⁻¹ -1 The total number of functional groups obtained from the absorption peaks.

[0401] (Heat resistance)

[0402] Measure 2g of fluorinated particles 1 and 3 and heat them at 340℃ for 2 hours. Visually observe the degree of foaming of the heated samples.

[0403] In fluorinated particle 1, the number of carbon atoms in the main chain of the first perfluoropolymer and the second fluoropolymer is 10 per 10 ... 6 The number of functional groups is less than 10.

[0404] In fluorinated particles 3, the fluoropolymer with TFE and M1 units has a main chain carbon number of 10 6 The number of functional groups is less than 10.

[0405] Furthermore, it was found that the fluorinated particles did not foam upon heating, demonstrating excellent heat resistance.

[0406] As can be seen from the above, in Example 1, even without using a fluorinated emulsifier, a fluorinated copolymer with the same excellent heat resistance as in Example 3 can be obtained.

[0407] In Example 2, a fluoropolymer was not obtained without the use of a fluorinated emulsifier.

[0408] The compositions disclosed herein are obtained without the use of fluorinated emulsifiers, which is very useful when the use of fluorinated emulsifiers is restricted.

[0409] Furthermore, the full disclosures of Japanese Patent Application No. 2023-129557, filed on August 8, 2023, and Japanese Patent Application No. 2024-099100, filed on June 19, 2024, are incorporated herein by reference. In addition, all documents, patent applications, and technical standards described in this specification are incorporated by reference to the extent that the incorporated portions of each document, patent application, and technical standard are specifically and separately described therein.

Claims

1. A composition comprising The first perfluoropolymer with a glass transition temperature below 10°C, and A second fluoropolymer, different from the first perfluoropolymer, comprising structural units based on tetrafluoroethylene and compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether) structural unit is 0.05 to 5.0 mol% relative to the total content of all structural units of the first and second fluoropolymers. CF2=CF-CF2-O-Rf …(1) In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

2. The composition of claim 1, wherein, Both the first perfluoropolymer and the second fluoropolymer are free of functional groups, or the first perfluoropolymer and the second fluoropolymer have a main chain carbon number of 10... 6 The total number of functional groups is less than 100.

3. The composition according to claim 1 or 2, wherein, The first perfluoropolymer comprises tetrafluoroethylene-based structural units and perfluoro(alkyl vinyl ether)-based structural units.

4. The composition of claim 3, wherein, In the first perfluoropolymer, the number of the perfluoro(alkyl vinyl ether)-based structural units is 20 to 70 mol, relative to the total number of the tetrafluoroethylene-based structural units and the perfluoro(alkyl vinyl ether)-based structural units.

5. A method for manufacturing a fluoropolymer, comprising: The process of preparing an aqueous dispersion A comprising a first perfluoropolymer with a glass transition temperature below 10°C and an aqueous medium, and The process of polymerizing a monomer comprising tetrafluoroethylene and a compound represented by formula (1) in the aqueous dispersion A to produce a second fluoropolymer different from the first perfluoropolymer. Before the monomer begins polymerization, the content of the first perfluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion A. Prior to the polymerization of the monomer, the aqueous dispersion A is free of fluorinated emulsifiers, or the content of the fluorinated emulsifiers is less than 100 ppm by mass relative to the total mass of the aqueous dispersion A. CF2=CF-CF2-O-Rf …(1) In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

6. The method for manufacturing the fluoropolymer as described in claim 5, wherein, The amount of the monomer used is 1 to 50 parts by mass relative to 100 parts by mass of the aqueous medium used.

7. The method for manufacturing the fluoropolymer as described in claim 5 or 6, wherein, The process of preparing the aqueous dispersion A is a process of preparing aqueous dispersion A containing particles of the first perfluoropolymer and an aqueous medium. The process of manufacturing the second fluoropolymer includes polymerizing the monomer to produce a second fluoropolymer different from the first perfluoropolymer, and manufacturing particles comprising the first perfluoropolymer and the second fluoropolymer. The ratio of the average particle size of the particles comprising the first perfluoropolymer and the second perfluoropolymer to the average particle size of the particles of the first perfluoropolymer is greater than 2.

8. The method for manufacturing the fluoropolymer as described in claim 5 or 6, wherein, The viscosity of the aqueous dispersion A is below 2.0 mPa·s.

9. The method for manufacturing the fluoropolymer as described in claim 5 or 6, wherein, The thixotropic ratio of the aqueous dispersion A is 0.9 to 1.

2.

10. The method for manufacturing the fluoropolymer as described in claim 5 or 6, wherein, The monomer is polymerized in the presence of a polymerization initiator.

11. The method for manufacturing a fluoropolymer as claimed in claim 5 or 6, further comprising a step of fluorinating the first perfluoropolymer and the second fluoropolymer.

12. An aqueous dispersion, It is an aqueous dispersion containing an aqueous medium and melt-formable particles, wherein, The average particle size is less than 1 μm. The particles contain one or more fluorinated polymers. The fluoropolymer comprises structural units based on tetrafluoroethylene, structural units based on perfluoro(alkyl vinyl ether), and structural units based on compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether)-based structural unit is 0.05–5.0 mol% relative to the total number of structural units of the fluoropolymer. The content of the particles is 1-50% by mass relative to the total mass of the aqueous dispersion. The aqueous dispersion is free of fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of the fluorinated polymer. CF2=CF-CF2-O-Rf …(1) In formula (1), Rf is a perfluoroalkyl group with 1 to 10 carbon atoms, and the carbon atoms of the perfluoroalkyl group may have ether-like oxygen atoms.

13. The aqueous dispersion as described in claim 12, wherein the viscosity is 0.8 to 2.0 mPa·s.

14. A type of particle, It consists of particles that can be melted and shaped, among which, The average particle size is less than 1 μm. The particles contain one or more fluorinated polymers. The fluoropolymer comprises structural units based on tetrafluoroethylene, structural units based on perfluoro(alkyl vinyl ether), and structural units based on compounds represented by formula (1). The content of the perfluorinated (alkyl vinyl ether)-based structural unit is 0.05–5.0 mol% relative to the total number of structural units of the fluoropolymer. The particles do not contain fluorinated emulsifiers, or the content of fluorinated emulsifiers is less than 100 ppm by mass relative to the content of the fluorinated polymer. The content of the compound represented by formula (S1) is 1 to 10,000 ppb by mass relative to the fluoropolymer, and the content of the compound represented by formula (S2) is less than 100 ppb by mass. CF2=CF-CF2-O-Rf …(1) Formula (S1): H-(CF2) n -COOM Formula (S2): H-(CF2) m -SO3M In formulas (S1) and (S2), M independently represents a hydrogen atom, Na, K or NH4, n represents 7 to 11, and m represents 8 to 12.

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