Method for producing fluorine-containing polymer

Abstract

Provided is a method for producing a fluorine-containing polymer in which the generation of by-products having hydrophilic groups is suppressed. This method for producing a fluorine-containing polymer produces a fluorine-containing polymer by polymerizing a monomer containing a fluorine-containing monomer using a polymerization initiator X in an aqueous dispersion containing a hydrocarbon-containing surfactant and an aqueous medium, and the polymerization initiator X does not have a hydrophilic group and has a molecular weight of 200 or less.

Description

Technical Field

[0001] This invention relates to a method for manufacturing fluoropolymers. Background Technology

[0002] Fluoropolymers such as tetrafluoroethylene copolymers are used in various industrial fields due to their excellent heat resistance, chemical resistance, flame retardancy and weather resistance.

[0003] Fluorinated surfactants are sometimes used in the manufacture of fluoropolymers in the presence of aqueous media, but the use of hydrocarbon-containing surfactants has been studied in light of recent efforts to reduce environmental impact. Additionally, polymerization initiators with hydrophilic groups are used in the manufacture of fluoropolymers in the presence of aqueous media.

[0004] However, if hydrocarbon-containing surfactants and polymerization initiators with hydrophilic groups are used in the manufacture of fluoropolymers, large amounts of byproducts with hydrophilic groups may be generated, which become a new cause of environmental burden.

[0005] To address this problem, Patent Document 1 discloses a method for reducing byproducts with hydrophilic groups by using ion exchange resins and synthetic adsorbents.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 7236004 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In the method described in Patent Document 1, the generation of byproducts with hydrophilic groups can be reduced by using ion exchange resins and synthetic adsorbents. However, the method described in Patent Document 1 cannot suppress the generation of byproducts with hydrophilic groups itself. In particular, among the byproducts with hydrophilic groups, a large amount of the compound shown in formula (S1) tends to be generated.

[0011] The objective of this invention is to provide a method for manufacturing a fluoropolymer that suppresses the generation of byproducts having hydrophilic groups.

[0012] Solution for solving the problem

[0013] The inventors conducted in-depth research and found that the above-mentioned problems can be solved by the following configuration. [1]

[0015] A method for manufacturing a fluoropolymer involves polymerizing a monomer containing a fluorinated monomer in an aqueous dispersion comprising a hydrocarbon-containing surfactant and an aqueous medium using a polymerization initiator X.

[0016] The polymerization initiator X does not have hydrophilic groups and has a molecular weight of less than 200. [2]

[0018] According to the method for manufacturing fluoropolymers described in [1], wherein the polymerization initiator X is a compound represented by formula (X),

[0019] R 1 -CO-OOR 2 (X)

[0020] In equation (X), R 1 and R 2 Each is an alkyl group having 1 to 5 carbon atoms. [3]

[0022] According to the manufacturing method of the fluoropolymer described in [1] or [2], wherein the fluoropolymer contains tetrafluoroethylene. [4]

[0024] The method for manufacturing a fluoropolymer according to any one of [1] to [3], wherein the hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants. [5]

[0026] An aqueous dispersion comprising a fluoropolymer and an aqueous medium, wherein the fluoropolymer has groups of formula (Y) at the ends of its molecular chains, and the fluoropolymer is polytetrafluoroethylene.

[0027] R 1 -(O) n - (Y)

[0028] In formula (Y), R 1 It is an alkyl group with 1 to 4 carbon atoms, where n is 0 or 1. [6]

[0030] According to the aqueous dispersion described in [5], wherein, in the formula (Y), R 1 It is tert-butyl. [7]

[0032] The aqueous dispersion according to [5] or [6] further comprises a hydrocarbon-containing surfactant. [8]

[0034] According to the aqueous dispersion of [7], the hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants. [9]

[0036] A solid composition comprising a fluoropolymer having groups of formula (Y) at the ends of its molecular chains.

[0037] The fluoropolymer is polytetrafluoroethylene.

[0038] R 1 -(O) n - (Y)

[0039] In formula (Y), R 1 It is an alkyl group with 1 to 4 carbon atoms, where n is 0 or 1.

[10]

[0041] According to the solid composition described in [9], wherein, in the formula (Y), R 1 It is tert-butyl.

[11]

[0043] The solid composition according to [9] or

[10] further comprises a hydrocarbon-containing surfactant.

[12]

[0045] According to the solid composition of

[11] , wherein the hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants.

[0046] The effects of the invention

[0047] According to the present invention, a method for manufacturing fluoropolymers that suppresses the generation of byproducts having hydrophilic groups can be provided. Detailed Implementation

[0048] The meanings of the terms used in this specification are as follows.

[0049] In this specification, the numerical range indicated by "~" refers to the range of values ​​before and after "~" as the lower and upper limits. Within the numerical ranges described in stages in this specification, the upper or lower limit of a particular numerical range can be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, within the numerical ranges described in this specification, the upper or lower limit of a particular numerical range can be replaced with the values ​​shown in the embodiments.

[0050] In this specification, each component may be used alone as one substance belonging to that component, or in combination with two or more substances. Here, when two or more substances are used in combination for each component, unless otherwise specified, the content of that component refers to the total content of the substances used in combination.

[0051] In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, "unit" is a general term for atomic groups directly formed by monomer polymerization, derived from one molecule of the aforementioned monomer, and atomic groups obtained by chemically transforming a portion of the aforementioned atomic groups. "Monomer-based unit" is also referred to as "unit" below.

[0052] The content (mass % or mole %) of each unit relative to all units contained in a polymer can be determined by analyzing the polymer using solid-state nuclear magnetic resonance spectroscopy (NMR). However, the content of each unit calculated from the amount of each monomer fed is usually roughly consistent with the actual content of each unit.

[0053] [Manufacturing methods for fluoropolymers]

[0054] The method for manufacturing the fluoropolymer of the present invention (hereinafter also referred to as "this manufacturing method") is a method for manufacturing a fluoropolymer (hereinafter also referred to as "the second fluoropolymer") by polymerizing a monomer containing a fluorinated monomer (hereinafter also referred to as "specific monomer") in an aqueous dispersion containing a hydrocarbon surfactant and an aqueous medium using a polymerization initiator X, wherein the polymerization initiator X does not have a hydrophilic group and has a molecular weight of 200 or less.

[0055] According to this manufacturing method, the generation of byproducts with hydrophilic groups can be suppressed. The details of the reason are not yet clear, but it is speculated to be due to the following reasons.

[0056] It is believed that when the polymerization initiator with hydrophilic groups described in Patent Document 1 is used in the manufacture of fluoropolymers, the groups derived from the polymerization initiator with hydrophilic groups add to the end of the oligomer derived from the fluorinated monomer, thereby generating byproducts with hydrophilic groups.

[0057] In contrast, it is speculated that because polymerization initiator X does not possess hydrophilic groups, it inhibits the formation of byproducts with hydrophilic groups. Furthermore, it is believed that polymerization initiator X is tuned to a specific molecular weight, thus enabling the complete polymerization of fluorinated monomers in an aqueous dispersion.

[0058] <Aqueous Dispersion>

[0059] This manufacturing method uses an aqueous dispersion containing a hydrocarbon-containing surfactant and an aqueous medium.

[0060] (Hydrocarbon-containing surfactants)

[0061] Hydrocarbon-containing surfactants are surfactants that have hydrocarbon groups.

[0062] Specifically, the hydrocarbon-containing surfactant preferably has at least one hydrogen atom among the groups that substituted on the carbon atom constituting the hydrocarbon group, and the carbon atom can be replaced by a chlorine atom, a bromine atom, or an iodine atom. Additionally, the methylene group in the hydrocarbon group can be replaced by -O- or -CO-.

[0063] In the hydrocarbon surfactant, the percentage of hydrogen atoms substituted on the carbon atoms (100 × total number of hydrogen atoms / total number of groups substituted on all carbon atoms) is preferably 75% or more, more preferably 85% or more, and even more preferably 95% or more. The upper limit is preferably 99% or less.

[0064] From the perspective of the stability of fluoropolymers, the hydrocarbon-containing surfactant preferably comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants, and more preferably comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants.

[0065] Anionic hydrocarbon surfactants are surfactants that have anionic functional groups, a negatively charged hydrophilic portion, and a hydrophobic portion with hydrocarbon groups such as alkyl groups.

[0066] As a specific example of anionic functional groups, the carboxylic acid group (-COO) can be cited. - ), sulfonic acid group (-SO3) - ), sulfate group (-SO4) 2- ), phosphonic acid group (-PO3) 2- ) and phosphate group (-PO4) 3- ).

[0067] Specific examples of anionic hydrocarbon surfactants include branched tertiary carboxylic acids with 10 carbon atoms (Versatic 10, manufactured by Resolution Performance Products), linear alkyl polyether sulfonates (Avanel S series, manufactured by BASF), sodium lauryl sulfate, and sulfosuccinate surfactants (Lankropol K8300, manufactured by AkzoNobelSurfaceChemistry LLC.).

[0068] Nonionic hydrocarbon surfactants are hydrocarbon surfactants that do not possess ionic functional groups. Examples of ionic functional groups include the anionic functional groups mentioned above and cationic functional groups such as quaternary ammonium cations.

[0069] Nonionic hydrocarbon surfactants preferably contain a hydrophobic portion having a long-chain hydrocarbon group and a hydrophilic portion having a polyoxyalkylene chain.

[0070] Examples of nonionic hydrocarbon surfactants include block copolymers containing various polyoxyalkylene blocks, such as those containing polyethylene oxide and polypropylene oxide.

[0071] As nonionic hydrocarbon surfactants, examples include the surfactants described in paragraphs

[0043] to

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

[0072] Before starting the polymerization of the monomer (specific monomer) used in the polymerization of the second fluoropolymer, the content of the hydrocarbon-containing surfactant relative to the total mass of the aqueous dispersion is preferably 0.00001 to 10% by mass, more preferably 0.0001 to 1% by mass.

[0073] In this specification, "before the polymerization of the monomer used in the polymerization of the second fluoropolymer" means just before the moment when polymerization is about to begin. Here, "the moment when polymerization begins" can be exemplified as: the moment when the monomer and polymerization initiator coexist in the reactor after the polymerization temperature has been reached, and the moment when the polymerization temperature has been reached in the reactor after the monomer and polymerization initiator X have coexisted in the reactor.

[0074] (Aqueous medium)

[0075] Aqueous dispersions contain aqueous media.

[0076] In the case where the aqueous dispersion contains the first fluoropolymer described later, the aqueous medium contained in the aqueous dispersion may be the polymerization solvent used in the manufacture of the first fluoropolymer.

[0077] Examples of aqueous media contained in aqueous dispersions include water and mixtures of water and water-soluble organic solvents. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0078] Before the polymerization of the monomer used in the polymerization of the second fluoropolymer begins, the content of the aqueous medium relative to the total mass of the aqueous dispersion is preferably 60 to 99.9% by mass, more preferably 96 to 99.9% by mass, and even more preferably 98 to 99.9% by mass.

[0079] (First fluoropolymer)

[0080] The aqueous dispersion may contain a first fluoropolymer.

[0081] The first fluoropolymer is a polymer having hydrophilic groups and hydrophobic portions. The hydrophilic groups in the first polymer mainly originate from residues of the water-soluble initiator (described later) located at the ends of the polymer and / or from the side chain structure of the polymer. Furthermore, the hydrophobic portions in the first fluoropolymer originate from units formed by the polymerization of monomers having fluorine atoms (described later). It is presumed that when a specific monomer polymerizes in the presence of the first fluoropolymer, the first fluoropolymer adsorbs and incorporates the specific monomer into the aforementioned hydrophobic portions, thereby solubilizing the specific monomer. Furthermore, by adding a polymerization initiator X, the specific monomer polymerizes within the particles of the first fluoropolymer. Additionally, it is presumed that the first fluoropolymer contributes to the dispersion stabilization of various components in aqueous media.

[0082] The first fluoropolymer is preferably a polymer that is different from the second fluoropolymer.

[0083] The first fluoropolymer is a polymer containing fluorine atoms.

[0084] The first fluoropolymer preferably comprises a tetrafluoroethylene (hereinafter also referred to as "TFE")-based unit (hereinafter also referred to as "TFE unit"). The first fluoropolymer more preferably comprises a TFE unit and a perfluoro (alkyl vinyl ether)-based unit (hereinafter also referred to as "PAVE unit").

[0085] From the perspective of excellent polymerization reactivity when manufacturing the first fluoropolymer and the ability to manufacture the second fluoropolymer more efficiently, PAVE prefers the monomer shown in formula (1).

[0086] CF2 = CF - OR f1 ···(1)

[0087] In equation (1), R f1 It is a perfluoroalkyl group with 1 to 10 carbon atoms.

[0088] From the perspective of superior polymerization reactivity, R f1 The number of carbon atoms is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and especially preferably 1 to 3.

[0089] Perfluoroalkyl groups can be either linear or branched.

[0090] 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"). From the perspective of being able to manufacture the second fluoropolymer more efficiently, PMVE or PPVE is preferred, and PMVE is more preferred.

[0091] When the first fluoropolymer contains TFE units and PAVE units, the content of PAVE units in the first fluoropolymer is preferably 20 to 60 mol% relative to the total amount of TFE units and PAVE units, more preferably 25 to 60 mol%, and even more preferably 30 to 55 mol%.

[0092] When the first fluoropolymer contains TFE units and PAVE units, the total content of TFE units and PAVE units in the first fluoropolymer is preferably 90 to 100 mol%, more preferably 95 to 100 mol%, and even more preferably 99 to 100 mol% relative to all units of the first fluoropolymer.

[0093] The first fluoropolymer may contain units based on monomers other than TFE and PAVE.

[0094] Hexafluoropropylene is preferred as one of the other monomers mentioned above.

[0095] From the perspective of enabling more efficient production of the second fluoropolymer, the first fluoropolymer preferably does not contain units based on other monomers.

[0096] Essentially, "not containing units based on other monomers" means that the content of units based on other monomers is less than 0.01 mol% relative to all units of the first fluoropolymer, preferably 0 mol%.

[0097] The first fluoropolymer is preferably a polymer composed of TFE units and PAVE units. In this case, the ratio of TFE units to PAVE units in the first fluoropolymer, expressed as TFE units / PAVE units, is preferably 80.0~40.0 mol% / 20.0~60.0 mol%, more preferably 75.0~40.0 mol% / 25.0~60.0 mol%, and even more preferably 70.0~45.0 mol% / 30.0~55.0 mol%.

[0098] Before the polymerization of the monomer (specific monomer) used in the polymerization of the second fluoropolymer begins, the content of the first fluoropolymer is preferably 0.01 to 4.0% by mass relative to the total mass of the aqueous medium in the aqueous dispersion. From the viewpoint of being able to manufacture the second fluoropolymer more efficiently, it is preferably 0.01 to 0.6% by mass, and more preferably 0.01 to 0.5% by mass.

[0099] The first fluoropolymer is preferably dispersed in an aqueous medium in the form of particles.

[0100] From the perspective of enabling more efficient manufacturing of the second fluoropolymer, the average particle size of the first fluoropolymer is preferably 1 to 150 nm, more preferably 10 to 120 nm, and even more preferably 50 to 120 nm.

[0101] The average particle size of the first fluoropolymer was determined by laser diffraction and scattering method. The total volume of the particle group was set to 100% and a cumulative curve was obtained. The particle size (D50) at the point where the cumulative volume reached 50% on the cumulative curve was obtained.

[0102] A preferred method for manufacturing the first fluoropolymer is to polymerize monomers (preferably a mixture of monomers containing TFE and PAVE) in an aqueous medium in the presence of a polymerization initiator. This yields a first fluoropolymer dispersed in particulate form in an aqueous medium.

[0103] The aforementioned hydrocarbon-containing surfactant can be added to an aqueous medium in which the particles of the first fluoropolymer obtained through this operation are dispersed, to create the aforementioned aqueous dispersion. Alternatively, other aqueous media and the aforementioned hydrocarbon-containing surfactant can be further added to the aqueous medium in which the particles of the first fluoropolymer are dispersed, to create the aforementioned aqueous dispersion. Alternatively, the first fluoropolymer can be dispersed in another aqueous medium by solvent displacement, and the aforementioned hydrocarbon-containing surfactant can be added thereto to create the aforementioned aqueous dispersion.

[0104] As the polymerization initiator used in the manufacture of the first fluoropolymer, a water-soluble polymerization initiator is preferred. Here, a water-soluble polymerization initiator is defined as a polymerization initiator that can dissolve more than 1 g of 100 g of water at 20°C. As a water-soluble polymerization initiator, persulfate-based or organic polymerization initiators are more preferred, and persulfate-based initiators are even more preferred.

[0105] Specific examples of persulfates include ammonium persulfate, sodium persulfate, and potassium persulfate, with ammonium persulfate being preferred.

[0106] Specific examples of organic polymerization initiators include disuccinic acid peroxide and azobisisobutyramidine dihydrochloride.

[0107] The aqueous medium used in the manufacture of the first fluoropolymer is the same as the specific example of the aqueous medium used in the manufacture of the second fluoropolymer described above.

[0108] The preferred method for manufacturing the first fluoropolymer includes a heating step that involves heating an aqueous medium in which the first fluoropolymer is dispersed. This deactivates the polymerization initiator present in the system, thus reducing the influence of the polymerization initiator used in the manufacture of the first fluoropolymer during the polymerization of the second fluoropolymer. Consequently, a second fluoropolymer with a high molecular weight is readily obtained.

[0109] From the perspective of further promoting the deactivation of polymerization initiators in aqueous media, the heating temperature in the heating process is preferably 70~100℃, more preferably 80~98℃, and even more preferably 85~95℃.

[0110] (Other ingredients)

[0111] Aqueous dispersions may contain components other than those mentioned above (hereinafter also referred to as "other components").

[0112] Other specific examples of ingredients include chain transfer agents, pH adjusters, and waxes.

[0113] Specific examples of chain transfer agents include ethyl acetate, methanol, ethanol, tert-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane.

[0114] Inorganic salts can be cited as specific examples of pH adjusters.

[0115] Specific examples of inorganic salts include phosphates such as disodium hydrogen phosphate and sodium dihydrogen phosphate; and carbonates such as sodium bicarbonate and sodium carbonate. As phosphates, disodium hydrogen phosphate dihydrate or disodium hydrogen phosphate dodecahydrate are preferred.

[0116] As specific examples of waxes, Parafffin Wax-155 and Parafffin Wax-150 (both manufactured by NIPPON SEIRO CO., LTD.) can be cited.

[0117] When the aqueous dispersion contains a chain transfer agent, the content of the chain transfer agent is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the aqueous medium. Furthermore, the amount of chain transfer agent used is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the specific monomer described later, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass.

[0118] When the aqueous dispersion 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.

[0119] When the aqueous dispersion contains wax, the wax content is preferably 1 to 10 parts by mass relative to 100 parts by mass of the aqueous medium.

[0120] Before the polymerization of the monomers used in the polymerization of the second fluoropolymer begins, from the perspective of polymerization stability, the concentration of fluoride ions relative to the total mass of the aqueous dispersion is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less. As a lower limit, 0 ppm by mass can be cited as an example.

[0121] As an example of a method to achieve the concentration of fluoride ions to the aforementioned value, one can cite a method of removing fluoride ions by using an anion exchange resin during the manufacture of the first fluoropolymer.

[0122] 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, and are sometimes contained in an aqueous dispersion.

[0123] Before the polymerization of the monomers used in the polymerization of the second fluoropolymer begins, from the perspective of further suppressing the generation of byproducts with hydrophilic groups, 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. As a lower limit, 0 ppm by mass can be cited as an example.

[0124] As an example of a method to achieve the above-mentioned concentration of sulfate ions, one can cite a method of removing sulfate ions by using an anion exchange resin during the manufacture of the first fluoropolymer.

[0125] Here, sulfate ions, for example, originate from polymerization initiators (especially ammonium persulfate) used in the manufacture of the first fluoropolymer, and are sometimes contained in aqueous dispersions containing the first fluoropolymer. By keeping the sulfate ion content below 10 ppm by mass (especially below 5 ppm by mass), the generation of byproducts with hydrophilic groups can be further suppressed.

[0126] Before the polymerization of the monomers used in the polymerization of the second fluoropolymer begins, from the perspective 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. As a lower limit, 0 ppm by mass can be cited as an example.

[0127] As an example of a method to achieve the above-mentioned concentration of ammonium ions, one can cite a method of removing ammonium ions by using a cation exchange resin during the manufacture of the first fluoropolymer.

[0128] Here, ammonium ions, for example, originate from the initiator (especially ammonium persulfate) used in the manufacture of the first fluoropolymer, and are sometimes contained in the aqueous dispersion containing the first fluoropolymer. It is speculated that by keeping the ammonium ion content below 20 ppm by mass, the ionic strength in the aqueous medium is reduced, resulting in improved manufacturing efficiency of the second fluoropolymer.

[0129] Before the polymerization of the monomers used in the polymerization of the second fluoropolymer begins, from the perspective of the excellent heat resistance of the second fluoropolymer, the concentration of the water-soluble polymerization initiator 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. As a lower limit, 0 ppm by mass can be cited as an example.

[0130] As an example of a method to achieve the above-mentioned concentration of the water-soluble polymerization initiator, one can cite a method of using an anion exchange resin to remove the water-soluble polymerization initiator during the manufacture of the first fluoropolymer, and a method of deactivating the above-mentioned water-soluble polymerization initiator.

[0131] Here, water-soluble polymerization initiators, such as those used in the manufacture of the first fluoropolymer (especially ammonium persulfate), are sometimes included in the aqueous dispersion containing the first fluoropolymer. It is presumed that by keeping the content of the water-soluble polymerization initiator below 20 ppm by mass, the generation of byproducts with hydrophilic groups can be further suppressed.

[0132] <Specific Individual>

[0133] This manufacturing method uses specific monomers. These specific monomers include fluorinated monomers.

[0134] Specific examples of fluorinated monomers include TFE, hexafluoropropylene (hereinafter also referred to as "HFP"), vinylidene fluoride (hereinafter also referred to as "VdF"), fluoroalkyl vinylidene (hereinafter also referred to as "FAE"), and PAVE. Two or more fluorinated monomers can be used in combination.

[0135] Specific examples of FAEs include CH2=CH(CF2)2F, CH2=CH(CF2)3F, CH2=CH(CF2)4F (hereinafter also referred to as "C4OLF"), CH2=CF(CF2)3H, and CH2=CF(CF2)4H, with C4OLF being preferred.

[0136] As for PAVE, it is the same as the PAVE in the first fluoropolymer described above, and the preferred method is also the same.

[0137] The fluorinated monomer preferably contains TFE, and more preferably TFE.

[0138] The amount of fluorinated monomer used relative to the amount of a specific monomer is preferably 97-100% by mass, more preferably 98-100% by mass, and even more preferably 99-100% by mass. The preferred amount is also the same when only TFE is used as the fluorinated monomer.

[0139] The fluorinated monomer is preferably composed of TFE units and PPVE units. In this case, the ratio of TFE units to PPVE units is preferably 99.9~90.0 mol% / 0.1~10.0 mol%, more preferably 99.5~92.0 mol% / 0.5~8.0 mol%, and even more preferably 99.0~95.0 mol% / 1.0~5.0 mol%.

[0140] The fluorinated monomer is preferably composed of TFE units and HFP units. In this case, the ratio of TFE units to HFP units is preferably 99.9~85.0 mol% / 0.1~15.0 mol%, more preferably 99.5~88.0 mol% / 0.5~12.0 mol%, and even more preferably 99.0~90.0 mol% / 1.0~10.0 mol%.

[0141] In addition, the amount of fluorinated monomer used relative to the amount of a specific monomer can be 10.0 to 100.0 mol%, more preferably 30.0 to 70.0 mol%, and even more preferably 40.0 to 60.0 mol%.

[0142] In addition, the amount of fluorinated monomer used relative to the amount of a specific monomer can be 90.0 to 99.9 mol%, and preferably 95.0 to 99.0 mol% when melt formability is important.

[0143] A particular monomer may contain monomers other than those mentioned above (hereinafter also referred to as "other monomers").

[0144] Other monomers include ethylene (hereinafter also referred to as "E"), propylene, vinyl chloride and vinylidene chloride, with ethylene being preferred. Two or more other monomers may also be used in combination.

[0145] The amount of other monomers used relative to the amount of a specific monomer is preferably 10.0 to 70.0 mol%, more preferably 20.0 to 60.0 mol%, and even more preferably 30.0 to 50.0 mol%.

[0146] The specific monomer is preferably composed of TFE units and E units. In this case, the ratio of TFE units to E units, in terms of TFE units / E units, is preferably 90.0~30.0 mol% / 10.0~70.0 mol%, more preferably 80.0~40.0 mol% / 20.0~60.0 mol%, and even more preferably 70.0~50.0 mol% / 30.0~50.0 mol%.

[0147] On the other hand, a particular monomer is preferably free of other monomers.

[0148] The amount of the specific monomer used is preferably 1 to 50 parts by mass relative to 100 parts by mass of the aqueous medium contained in the above aqueous dispersion, more preferably 1 to 40 parts by mass, and even more preferably 1 to 30 parts by mass.

[0149] <Polymerization Initiator X>

[0150] This manufacturing method uses polymerization initiator X.

[0151] Polymerization initiator X is a polymerization initiator that does not have hydrophilic groups and has a molecular weight of less than 200.

[0152] Hydrophilic groups and ionic functional groups are examples of groups that polymerization initiator X does not possess.

[0153] It should be noted that specific examples of ionic functional groups are as described above.

[0154] The polymerization initiator X has a molecular weight of 200 or less, preferably 190 or less, and more preferably 180 or less. The lower limit is preferably 50 or more, more preferably 100 or more, and even more preferably 150 or more.

[0155] The preferred polymerization initiator X is a compound represented by formula (X).

[0156] R 1 -CO-OOR 2 ... (X)

[0157] In equation (X), R 1 and R 2 Each is an alkyl group having 1 to 5 carbon atoms.

[0158] R 1 and R 2 The alkyl group shown can be either straight-chain or branched, preferably branched.

[0159] R 1 and R 2 The alkyl group shown has 1 to 5 carbon atoms, preferably 2 to 5, more preferably 3 to 5, further preferably 4 or 5, and particularly preferably 4.

[0160] As R 1 and R 2 The alkyl group shown is preferably methyl, propyl, butyl or dimethylpropyl, more preferably methyl, isopropyl, tert-butyl or 1,1-dimethylpropyl.

[0161] Examples of polymerization initiators X include tert-butyl peroxypentanoate (hereinafter also referred to as "PBPV"), tert-butyl peroxyisobutyrate (Luperox 80, tert-butyl peroxyisobutyrate), and tert-butyl peracetate (Luperox 7, tert-butyl peracetate), with PBPV being preferred. Two or more polymerization initiators X may be used in combination.

[0162] The amount of polymerization initiator X used relative to 100 parts by mass of a specific monomer is preferably 0.005 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, and even more preferably 0.01 to 2 parts by mass.

[0163] <Other Ingredients>

[0164] In this manufacturing method, other components besides those mentioned above may be used during the polymerization of a specific monomer.

[0165] Reducing agents can be cited as a specific example of other components.

[0166] The amount of other components used is preferably 1 to 2000 ppm relative to 100 parts by weight of a specific monomer.

[0167] <Process>

[0168] This manufacturing method involves polymerizing the aforementioned specific monomer in the above-mentioned aqueous dispersion to produce a second fluoropolymer.

[0169] When the aqueous dispersion contains a first fluoropolymer, the first fluoropolymer and the second fluoropolymer can be copolymerized.

[0170] The second fluoropolymer comprises units based on fluorinated monomers, preferably TFE-based units (hereinafter also referred to as "TFE units"), and more preferably TFE homopolymers (polytetrafluoroethylene, hereinafter also referred to as "PTFE").

[0171] The content of the fluorinated monomer-based unit (especially the TFE unit) relative to all the units of the second fluorinated polymer is preferably 99.0 to 100.0% by mass, more preferably 99.5 to 100.0% by mass, and even more preferably 99.9 to 100.0% by mass.

[0172] In this manufacturing method, the components can be added all at once or in batches. Furthermore, there are no particular restrictions on the order in which the components are added. For example, an aqueous dispersion containing a hydrocarbon-containing surfactant and an aqueous medium can be prepared, and polymerization initiator X can be added to this aqueous dispersion. Alternatively, the hydrocarbon-containing surfactant can be added after mixing the aqueous medium with the polymerization initiator X. The preferred method is the order of addition shown in the examples.

[0173] Specific monomers can be added to the reaction system (polymerization reaction vessel) using conventional methods. The monomers can be added continuously or intermittently to the reaction system at a polymerization pressure equal to a specified pressure. Alternatively, the monomers can be dissolved in an aqueous medium, and the resulting solution can be added to the reaction system continuously or intermittently.

[0174] Polymerization initiator X can be added to the reaction system all at once or in batches.

[0175] The polymerization temperature is preferably 10~95℃, more preferably 15~90℃.

[0176] The polymerization pressure is preferably 0.5~4.0 MPaG, more preferably 0.6~3.5 MPaG.

[0177] In the case of batch processing, the polymerization time is preferably 90 to 1000 minutes, more preferably 90 to 700 minutes.

[0178] The polymerization of a particular monomer is preferably carried out in the absence of fluorinated emulsifiers (fluorinated surfactants).

[0179] The absence of fluorinated emulsifiers means that the content of fluorinated emulsifiers relative to the total mass of the aqueous medium contained in the above-mentioned aqueous dispersion is less than 0.03 ppm by mass, preferably less than 0.02 ppm by mass, and more preferably 0 ppm by mass.

[0180] Fluorinated emulsifiers are emulsifiers in which the hydrophobic portion contains a fluorine atom. Specific examples of fluorinated emulsifiers include fluorinated alkylates and fluorinated ether carboxylic acids.

[0181] When using the first fluoropolymer, as described above, it is presumed that, for example, during the polymerization of a specific monomer, the specific monomer polymerizes within the polymer particles, thus it is assumed that particles containing both the first and second fluoropolymers are generated. That is, it is presumed that when the first fluoropolymer is used in this manufacturing method, the second fluoropolymer is obtained in the form of particles containing both the first and second fluoropolymers. In this case, by this manufacturing method, an aqueous dispersion containing particles containing both the first and second fluoropolymers can be obtained in the aforementioned aqueous medium.

[0182] On the other hand, without using the first fluoropolymer, an aqueous dispersion containing particles of the second fluoropolymer can be obtained in the above-mentioned aqueous medium.

[0183] (Byproducts containing hydrophilic groups)

[0184] According to this manufacturing method, the generation of byproducts having hydrophilic groups can be suppressed. Examples of hydrophilic groups include hydroxyl groups and ionic functional groups, and specific examples of ionic functional groups are described above.

[0185] As a specific example of a byproduct having a hydrophilic group, the compound shown in formula (S1) can be cited. The compound shown in formula (S1) is a specific byproduct produced during the manufacture of fluoropolymers when a polymerization initiator with a hydrophilic group (e.g., ammonium persulfate, disuccinic acid peroxide) and a fluorinated monomer (particularly tetrafluoroethylene) are used. Therefore, the inventors have particularly focused on the compound shown in formula (S1) among byproducts having a hydrophilic group. If the generation of the compound shown in formula (S1) can be suppressed, it can be said that the amount of byproduct having a hydrophilic group generated is reduced.

[0186] Formula (S1): H-(CF2) n1 -COOM

[0187] In formula (S1), M represents hydrogen atom, Na, K or NH4, and n1 represents 3~15 or 17.

[0188] [Aqueous dispersion]

[0189] The aqueous dispersion of the present invention (hereinafter also referred to as "the aqueous dispersion") comprises an aqueous medium and a second fluoropolymer, and may further comprise a first fluoropolymer.

[0190] This aqueous dispersion can be obtained, for example, by the manufacturing method described above.

[0191] <Aqueous Media>

[0192] The aqueous medium is the same as the specific example of the aqueous medium used in the manufacture of the second fluoropolymer described above.

[0193] From the perspective of the dispersion stability of the particles containing the second fluoropolymer, the content of the aqueous medium relative to the total mass of the aqueous dispersion is preferably 50 to 99% by mass, more preferably 60 to 99% by mass, and even more preferably 70 to 99% by mass.

[0194] <First Fluoropolymer and Second Fluoropolymer>

[0195] This aqueous dispersion may contain a first fluoropolymer. The first fluoropolymer is the same as the first fluoropolymer in the above-described manufacturing method, and preferably in the same manner.

[0196] When the aqueous dispersion contains a first fluoropolymer, the content of the first fluoropolymer relative to the total mass of the aqueous dispersion is preferably 0.1 to 1.0% by mass, more preferably 0.15 to 0.80% by mass, and even more preferably 0.20 to 0.70% by mass.

[0197] The second fluoropolymer is the same as the second fluoropolymer in the above-described manufacturing method, and the preferred embodiment is also the same.

[0198] The content of the second fluoropolymer relative to the total mass of the aqueous dispersion is preferably 5 to 50% by mass, more preferably 8 to 40% by mass, and even more preferably 10 to 35% by mass.

[0199] When the aqueous dispersion contains a first fluoropolymer, the total content of the first fluoropolymer and the second fluoropolymer relative to the total mass of the aqueous dispersion is preferably 5 to 50% by mass, more preferably 8 to 40% by mass, and even more preferably 10 to 35% by mass.

[0200] When the aqueous dispersion contains a first fluoropolymer, the first fluoropolymer and the second fluoropolymer may exist separately in the aqueous dispersion, but preferably exist in the form of particles containing the first fluoropolymer and the second fluoropolymer.

[0201] From the perspective of dispersion stability, the average particle size is preferably 500 μm or less, more preferably 450 μm or less, and even more preferably 400 μm or less.

[0202] In addition, from the perspective of aggregation, the average particle size is preferably 50 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more.

[0203] The average particle size is determined by measuring the particle size distribution using laser diffraction and scattering. The total volume of the particle group is set to 100%, and a cumulative curve is obtained. The particle size at the point where the cumulative volume reaches 50% on the cumulative curve is measured.

[0204] <Other>

[0205] This aqueous dispersion may contain the aforementioned hydrocarbon-containing surfactants.

[0206] As a hydrocarbon-containing surfactant, at least one can be selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants, and specific examples and preferred embodiments are as described above.

[0207] When the aqueous dispersion contains a hydrocarbon-containing surfactant, the content of the hydrocarbon-containing surfactant relative to the total mass of the aqueous dispersion is preferably 0.00001 to 10% by mass, more preferably 0.0001 to 1% by mass.

[0208] This aqueous dispersion preferably does not contain substantially the compounds shown in the above formula (S1).

[0209] The fact that this aqueous dispersion is substantially free of the compound represented by formula (S1) means, for example, that the amount of the compound relative to the total mass of the fluoropolymer in this aqueous dispersion is less than 10,000 ppb, less than 1,000 ppb, less than 100 ppb, or less than 10 ppb. There is no particular limitation on the lower limit; it can be 0 ppb, 0.1 ppb, or 1 ppb.

[0210] Here, the total mass of the fluoropolymer in this aqueous dispersion refers to the combined mass of the first and second fluoropolymers when the aqueous dispersion contains both the first and second fluoropolymers; and refers to the mass of the second fluoropolymer alone when the aqueous dispersion contains only the second fluoropolymer.

[0211] The content of the compound represented by formula (S1) relative to the total mass of the fluoropolymer in this aqueous dispersion can be determined using the method described in the Examples section below.

[0212] <Preferred method for this aqueous dispersion>

[0213] As a preferred embodiment of the aqueous dispersion, an example is an aqueous dispersion of PTFE comprising an aqueous medium and a second fluoropolymer, wherein the second fluoropolymer is a group having a group represented by the following formula (Y) at the end of the molecular chain (hereinafter also referred to as "aqueous dispersion A").

[0214] R 1 -(O) n - (Y)

[0215] In formula (Y), R 1 It is an alkyl group with 1 to 4 carbon atoms, where n is 0 or 1.

[0216] The group represented by formula (Y) is derived from the polymerization initiator X described above. Since the polymerization initiator X is used in the above manufacturing method, it is easy to introduce the group represented by formula (Y) derived from the polymerization initiator X into the end of the molecular chain of the second fluoropolymer. Especially when only TFE is used as the specific monomer, it is easy to introduce the group represented by formula (Y) into the end of the molecular chain of the obtained PTFE.

[0217] In formula (Y), R 1 The alkyl group can be either straight-chain or branched, preferably branched.

[0218] R 1The alkyl group has 1 to 4 carbon atoms, preferably 2 to 4, more preferably 3 or 4, and even more preferably 4.

[0219] As R 1 The alkyl group in the form of methyl, propyl or butyl is preferred. For better polymerization reactivity during manufacturing, methyl, isopropyl or tert-butyl is preferred, and tert-butyl is even more preferred.

[0220] The content of the second fluoropolymer contained in aqueous dispersion A is the same as that contained in this aqueous dispersion.

[0221] The specific examples and content of the aqueous medium contained in aqueous dispersion A are the same as those contained in this aqueous dispersion.

[0222] Aqueous dispersion A may contain a hydrocarbon-containing surfactant. At least one hydrocarbon-containing surfactant may be selected from the group consisting of anionic and nonionic hydrocarbon surfactants.

[0223] The specific examples and contents of the hydrocarbon-containing surfactants are the same as those in this aqueous dispersion.

[0224] The aqueous dispersion A may further contain the aforementioned first fluoropolymer. Specific examples and amounts of the first fluoropolymer are the same as those in the aqueous dispersion.

[0225] <Applications>

[0226] This aqueous dispersion can also be easily prepared into dispersions of organic solvents such as N-methylpyrrolidone and acetone by solvent displacement.

[0227] For example, a dispersion of an organic solvent can be prepared by mixing this aqueous dispersion with an organic solvent, evaporating it, or dehydrating it using anhydrous sodium sulfate, etc.

[0228] In this aqueous dispersion, the fluoropolymer is stably dispersed. Therefore, it is suitable for coating applications and adhesives, etc.

[0229] When the aqueous dispersion contains a first fluoropolymer, powders of the first and second fluoropolymers (preferably particles containing the first and second fluoropolymers) can be obtained by aggregating the first and second fluoropolymers from the aqueous dispersion.

[0230] Furthermore, if the aqueous dispersion does not contain the first fluoropolymer, a powder of the second fluoropolymer can be obtained by aggregating the second fluoropolymer (preferably particles containing the second fluoropolymer) from the aqueous dispersion.

[0231] Specific examples of aggregation methods include mechanical aggregation, freezing aggregation, acid aggregation, alkali aggregation, and aggregation using coagulants.

[0232] As a specific example of mechanical aggregation, the following method can be used: The aqueous dispersion is diluted with water to a concentration of 8-20% by mass for both the first and second fluoropolymers. Then, shear force is applied through vigorous stirring to cause primary aggregation of the first and second fluoropolymer particles. The pH of the aqueous dispersion can be adjusted as needed, and aggregation aids such as electrolytes and water-soluble organic solvents can be added. Examples of pH adjusters include sodium carbonate and sodium bicarbonate. Alternatively, the aggregation can be carried out in the presence of one or more compounds selected from the group consisting of ammonia, ammonium salts, and urea. Examples of electrolytes include inorganic salts such as potassium nitrate, sodium nitrate, sodium carbonate, and sodium bicarbonate. Examples of organic solvents include alcohols and acetone.

[0233] In the case of freezing and gathering, the gathering temperature is preferably -20 to 0°C. The gathering time is preferably 1 hour or more, more preferably 2 hours or more.

[0234] In the event of acid aggregation, it is preferable to add a solution containing the acid to the aqueous dispersion. Examples of acids that can be added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, and hydrofluoric acid, with hydrochloric acid being preferred. The acid concentration in the solution containing the acid is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.

[0235] As a method for alkali aggregation, it is preferable to add a solution containing an alkali to the aqueous dispersion. Examples of alkalis added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, with sodium hydroxide being preferred. The alkali concentration in the solution containing the alkali is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.

[0236] As a coagulant, known coagulants can be used. Specific examples of coagulants include aluminum salts, calcium salts, and magnesium salts. Preferred coagulants include aluminum sulfate, alum with the general formula M'Al(SO4)2·12H2O [where M' is a monovalent cation other than lithium], calcium nitrate, or magnesium sulfate. More preferred coagulants are alum, and even more preferred are potassium alum where M is potassium.

[0237] As a method of aggregation, mechanical aggregation or alkaline aggregation is preferred from the perspective of making aggregation particularly easy to promote.

[0238] [Solid Composition]

[0239] The solid composition of the present invention (hereinafter also referred to as "the solid composition") comprises a second fluoropolymer and may also comprise a first fluoropolymer.

[0240] In this specification, a solid composition refers to a composition in which the solid component accounts for 99% or more by mass.

[0241] Here, the mass of the solid components is calculated based on the mass before and after heating using the following method.

[0242] After heating 2.0 g of the solid composition at 170 °C for 20 minutes, the mass of the residue was weighed, and the mass of the solid component was calculated using the following formula.

[0243] Mass of solid components (mass%) = 100 × (mass of residue) / (mass of solid composition)

[0244] This solid composition is preferably obtained by using the aggregation method of the aqueous dispersion described above. The preferred embodiments of this solid composition are the same as those of the second fluoropolymer contained in the aqueous dispersion described above and the first fluoropolymer that may be used as needed, therefore their description is omitted.

[0245] When the solid composition contains a first fluoropolymer, the first fluoropolymer and the second fluoropolymer may be present in the solid composition separately, but preferably in the form of particles containing the first fluoropolymer and the second fluoropolymer described above.

[0246] When the solid composition contains a first fluoropolymer, the content of the first fluoropolymer relative to the total mass of the solid composition is preferably 0.10 to 5% by mass, more preferably 0.2 to 4% by mass, and even more preferably 0.3 to 3% by mass.

[0247] The content of the second fluoropolymer relative to the total mass of the solid composition is preferably 95-100% by mass, more preferably 96-100% by mass, and even more preferably 97-100% by mass.

[0248] When the solid composition contains a first fluoropolymer, the total content of the first fluoropolymer and the second fluoropolymer relative to the total mass of the solid composition is preferably 98 to 100% by mass, more preferably 99 to 100% by mass.

[0249] This solid composition may contain the aforementioned hydrocarbon-containing surfactant.

[0250] As a hydrocarbon-containing surfactant, at least one can be selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants, and specific examples and preferred embodiments are as described above.

[0251] When the solid composition contains a hydrocarbon-containing surfactant, the content of the hydrocarbon-containing surfactant relative to the total mass of the solid composition is preferably 0.000001 to 5% by mass, more preferably 0.000001 to 1% by mass.

[0252] This solid composition preferably does not contain substantially the compounds represented by the above formula (S1).

[0253] The absence of compounds of formula (S1) in this solid composition means, for example, that the amount of such compounds is 10 ppb or less relative to the total mass of the fluoropolymer in the solid composition. This can be less than 10 ppb, 5 ppb or less, or 1 ppb or less. There is no particular limitation on the lower limit; it can be 0 ppb, 0.1 ppb or 1 ppb.

[0254] Here, the total mass of the fluoropolymer in this solid composition refers to the combined mass of the first and second fluoropolymers when the solid composition contains both the first and second fluoropolymers, and to the mass of the second fluoropolymer alone when the solid composition contains only the second fluoropolymer.

[0255] The content of the compound represented by formula (S1) relative to the total mass of the fluoropolymer in this solid composition can be determined using the method described in the Examples section below.

[0256] <Preferred mode of this solid composition>

[0257] As a preferred example of the solid composition, a solid composition comprising a second fluoropolymer, wherein the second fluoropolymer is PTFE having a group represented by the above formula (Y) at the end of the molecular chain (hereinafter also referred to as "solid composition A").

[0258] The content of the second fluoropolymer contained in solid composition A is the same as that contained in this solid composition.

[0259] Solid composition A may contain a hydrocarbon-containing surfactant. At least one hydrocarbon-containing surfactant selected from the group consisting of anionic and nonionic hydrocarbon surfactants can be cited as examples.

[0260] The specific examples and amounts of the hydrocarbon-containing surfactants are the same as those in the solid composition.

[0261] Solid composition A may further comprise the first fluoropolymer described above. Specific examples and amounts of the first fluoropolymer are the same as those in the solid composition.

[0262] Solid composition A is preferably obtained by using the above-described aggregation method of the aqueous dispersion (especially the above-described aqueous dispersion A).

[0263] Example

[0264] The present invention will now be illustrated by examples. Examples 1-3 are embodiments, and Examples 4-6 are comparative examples. However, the present invention is not limited to these examples.

[0265] [Measurement and Evaluation Methods]

[0266] The various measurement and evaluation methods are described below.

[0267] <Average particle size in liquid>

[0268] The average particle size (D50) of the particles in the aqueous dispersions of each example was determined using a laser diffraction-scattering particle size distribution measuring device (Otsuka Electronics Co., Ltd., ELSZ).

[0269] <Proportion of units in the polymer>

[0270] The proportions of the units in the polymer are determined by 19 Determined by F-NMR analysis and infrared absorption spectroscopy analysis.

[0271] Melting point and crystallization energy

[0272] Melting point and crystallization energy were determined using a DSC8500 manufactured by Perkin Elmer.

[0273] Specifically, 10 mg of the sample for testing is measured in an aluminum sample pan, heated to 200 °C at a rate of 10 °C / min in air, and held for 1 minute. Then, the sample is heated to 380 °C at a rate of 10 °C / min. It is held at 380 °C for 1 minute and then cooled to 200 °C at a rate of 10 °C / min.

[0274] The melting point is determined by the peak temperature of the thermal melting originating from the sample, confirmed through heating from 200°C to 380°C. The crystallization energy is calculated from the peak area, confirmed through cooling from 380°C to 200°C. It should be noted that the smaller the absolute value of the crystallization energy, the higher the molecular weight.

[0275] <Content M1 and Content M2>

[0276] The contents of the compound represented by the above formula (S1) relative to the total mass of the fluoropolymers obtained in the aqueous dispersions obtained in the following examples (hereinafter also referred to as "content M1") and the contents of the compound represented by the above formula (S1) relative to the total mass of the fluoropolymers obtained in the following examples (hereinafter also referred to as "content M2") were determined using a liquid chromatography-mass spectrometry instrument as follows.

[0277] (Sample preparation)

[0278] Add 1 mL of aqueous dispersion and 5 mL of methanol, stir, and centrifuge (8000 rpm, 10 minutes) to allow the fluoropolymer to settle. Use the supernatant as the extract. Dilute the extract with water or methanol as needed for determination. This yields extract M1 for the determination of content M1.

[0279] In addition, 5 mL of methanol was added to 2.5 g of the solid composition obtained in the examples described later, and the mixture was ultrasonically treated at 50°C for 2 hours. Centrifugation (5000 rpm, 5 minutes) was then performed to allow the fluoropolymer to settle, and the supernatant was collected as the extract. The extract was diluted with water or methanol as needed for determination. This process yielded extract M2 for the determination of content M2.

[0280] (Measurement Procedure)

[0281] Regarding the content of compounds of formula (S1) contained in extract M1 or extract M2, compounds with n=3~13, 15 and 17 are determined by conversion to perfluorocarboxylic acids with the same number of carbon atoms. Additionally, the content of compound n=14 is determined by conversion to perfluorooctanoic acid.

[0282] Specifically, firstly, methanol standard solutions of perfluorocarboxylic acids with known concentrations of 1–180 ng / g at five levels are prepared. Then, a is calculated using the following formula (A1) by approximating the sample concentration and peak integral value of each solution.

[0283] A = a × X (A1)

[0284] A: Peak area of ​​perfluorocarboxylic acids; X: Concentration of perfluorocarboxylic acids (ng / g)

[0285] -Determination Conditions-

[0286] The measuring equipment and conditions are shown in Table 1 below.

[0287] [Table 1]

[0288]

[0289] -MRM Measurement Parameters-

[0290] The MRM measurement parameters are shown in Table 2 below.

[0291] [Table 2]

[0292]

[0293] The compounds of formula (S1) contained in the extract were determined using a liquid chromatography-mass spectrometry (LC-MS) apparatus. For the extract, the peak areas of the compounds of formula (S1) with each number of carbon atoms were determined using the MRM method.

[0294] -MRM Measurement Parameters-

[0295] The MRM measurement parameters are shown in Table 3 below.

[0296] [Table 3]

[0297]

[0298] Next, the content of compounds with a carbon number (n1+1) in the extract (extract M1 or extract M2) is calculated using the following formula (A2). It should be noted that 'a' in formula (A2) refers to 'a' obtained from the above formula (A1).

[0299] XCm=ACm / a×ρ1 / ρ2 ·(A2)

[0300] XCm: Content (ng / g) of compounds with the number of carbon atoms (n1+1) in the extract.

[0301] ACm: Peak area of ​​compounds showing the number of carbon atoms (n1+1) in the extract.

[0302] ρ1: Density of methanol

[0303] ρ2: Density of the extract

[0304] The quantitation limit in this assay is 1 ng / g.

[0305] The content (YCm) of each compound relative to the content of fluoropolymers in the aqueous dispersion is determined by the following formula (A3) based on the XCm value of each compound obtained using extract M1.

[0306] YCm = XCm × Dilution ratio × W1a / (W1b × c) (A3)

[0307] YCm: The content of compounds with a carbon number of (n1+1) relative to the content of fluoropolymers in an aqueous dispersion (ng / g) (relative to fluoropolymers).

[0308] W1a: Mass of extract M1 (g)

[0309] W1b: Mass (g) of the aqueous dispersion used in sample preparation of extract M1.

[0310] c: The concentration of solids in the aqueous dispersion used in the sample preparation of extract M1.

[0311] The dilution ratio indicates the mass ratio by which the extract is diluted with water or methanol to make XCm below 180 ng / g.

[0312] The YCm values ​​of all compounds are summed and used as the content M1.

[0313] In addition, the content (ZCm) of each compound relative to the content of the fluoropolymer in the solid composition is determined by the following formula (A4) based on the XCm value of each compound obtained using extract M2.

[0314] ZCm = XCm × Dilution ratio × W2a / W2b (A4)

[0315] ZCm: The content of (n1+1) compounds in the powder (relative to fluoropolymers).

[0316] W2a: Mass of extract M2 (g)

[0317] W2b: Mass (g) of the dried powder used in sample preparation of extract M2.

[0318] The dilution ratio indicates the mass ratio by which the extract is diluted with water or methanol to make XCm below 180 ng / g.

[0319] The ZCm values ​​of each compound are summed and used as the content M2.

[0320] <Detection of end structures>

[0321] The terminal group structure of the fluoropolymer in the solid composition was determined by pyrolysis GC-TOF / MS. Specifically, a pyrolysis apparatus (EGA / Py-3030D, Fronteir Labs) was used to induce the pyrolysis reaction at a pyrolysis temperature of 600 °C and an interface temperature of 320 °C, followed by analysis using GC-TOF / MS. Detailed determination conditions are shown in Table 4 below.

[0322] [Table 4]

[0323]

[0324] [Preparation of Raw Material Solution A]

[0325] In a 60.5L stainless steel pressure reactor, 33kg of ultrapure water and 2.1kg of PMVE were added, and the temperature was raised to 90°C while stirring. Then, 210g of TFE and 150g of ammonium persulfate aqueous solution (5.6% by mass) were added to initiate polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. After adding 120g of TFE, the reactor was cooled to stop the polymerization reaction. The residual gas in the reactor was recovered, and the temperature was raised to 90°C, stirred at 20 rpm for 3 hours. The reactor was then cooled, and the liquid was discharged. This liquid was used as feedstock A.

[0326] [Preparation of Raw Material Solution B]

[0327] Add 20g of Dowex Monosphere 650C (Cation Exchange Resin, manufactured by DuPont) to the above-mentioned feed solution A (490g). After stirring for 60 minutes, separate the feed solution and ion exchange resin by filtration. Add 20g of Purolite A300 (Anion Exchange Resin, manufactured by Purolite) to the filtered feed solution. After stirring for 60 minutes, separate the feed solution and ion exchange resin by filtration to obtain feed solution B.

[0328] In feed solution B, fluoropolymer 1A particles are dispersed in an aqueous medium, and the content of fluoropolymer 1A is 0.5% of the total mass of feed solution B.

[0329] After freezing and agglomerating the raw material solution B, the mixture was filtered and separated. The resulting fluoropolymer 1A was washed with ultrapure water and then dried under vacuum at 100°C. NMR analysis of the obtained fluoropolymer 1A showed a PMVE unit / TFE unit ratio of 54 / 46 (molar ratio).

[0330] [Example 1]

[0331] Paraffin wax (36 g), ultrapure water (157 g), feedstock solution B (617 g), and PBPV solution (4% by mass, 2.6 g) were added to a 1.3 L stainless steel pressure reactor to obtain aqueous dispersion B. The temperature was raised to 65 °C, and the aqueous dispersion B was stirred. TFE was added until the pressure inside the reactor reached 1.4 MPaG to begin polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. At the addition of 8 g of TFE, sodium lauryl sulfate aqueous solution (0.02% by mass, 5 mL) was added, and this was repeated for subsequent additions of 19 g of TFE. After adding 162 g of TFE, the reactor was cooled to end the polymerization reaction.

[0332] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 1. Aqueous dispersion 1 is a dispersion in an aqueous medium containing particles (average particle size 210 nm) of fluoropolymer 1A and fluoropolymer 2A, with a solid content concentration of 18% by mass.

[0333] The particles in the obtained aqueous dispersion 1 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 338°C, and its crystallization energy is -22 J / g. The solid composition was analyzed according to the above-mentioned method for "Detection of End Structures," and the fragment peaks confirmed the presence of tert-butyl groups at the ends of the PTFE molecular chains.

[0334] [Example 2]

[0335] In a 1.3L stainless steel pressure reactor, paraffin wax (36g), ultrapure water (157g), feedstock solution B (617g), PBPV solution (4% by mass, 2.6g), and sodium lauryl sulfate aqueous solution (0.02% by mass, 40mL) were added to obtain aqueous dispersion C. The temperature was raised to 65℃, and the aqueous dispersion C was stirred. TFE was added until the pressure inside the reactor reached 1.4 MPaG to begin polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. After adding 162g of TFE, the reactor was cooled to end the polymerization reaction.

[0336] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 2. Aqueous dispersion 2 is a dispersion in an aqueous medium containing particles (average particle size 210 nm) of fluoropolymer 1A and fluoropolymer 2A, with a solid content concentration of 18% by mass.

[0337] The particles in the obtained aqueous dispersion 2 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 338°C, and its crystallization energy is -22 J / g. The solid composition was analyzed according to the above-mentioned method for "Detection of End Structures," and the fragment peaks confirmed the presence of tert-butyl groups at the ends of the PTFE molecular chains.

[0338] [Example 3]

[0339] In a 1.3L stainless steel pressure reactor, paraffin wax (36g), ultrapure water (764g), PBPV solution (4% by mass, 13g), and sodium lauryl sulfate aqueous solution (0.1% by mass, 5mL) were added to obtain aqueous dispersion D. At the addition of 8g of TFE, sodium lauryl sulfate aqueous solution (0.1% by mass, 5mL) was added, followed by a continuous addition of 0.1% by mass, 5mL of sodium lauryl sulfate aqueous solution relative to the subsequent addition of 19g of TFE. The temperature was raised to 65°C, and aqueous dispersion D was stirred. TFE was added until the pressure inside the reactor reached 1.4 MPaG to initiate polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. After adding 162g of TFE, the reactor was cooled to terminate the polymerization reaction.

[0340] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 3. Aqueous dispersion 3 is a dispersion containing particles of fluoropolymer 2A dispersed in an aqueous medium, with a solid content concentration of 18% by mass.

[0341] The particles in the obtained aqueous dispersion 3 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 334°C, and its crystallization energy is -26 J / g. The solid composition was analyzed according to the above-mentioned method for "Detection of End Structures," and the fragment peaks confirmed the presence of tert-butyl groups at the ends of the PTFE molecular chains.

[0342] [Example 4]

[0343] In a 1.3L stainless steel pressure reactor, paraffin wax (36g), ultrapure water (157g), feedstock solution B (617g), and ammonium persulfate aqueous solution (1% by mass, 1.5g) were added to obtain aqueous dispersion E. The temperature was raised to 65°C, and aqueous dispersion E was stirred. TFE was added until the pressure inside the reactor reached 1.4 MPaG to begin polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. At the addition of 8g of TFE, sodium lauryl sulfate aqueous solution (0.02% by mass, 5mL) was added, and this was repeated for subsequent additions of 19g of TFE. After adding 162g of TFE, the reactor was cooled to end the polymerization reaction.

[0344] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 4. Aqueous dispersion 4 is a dispersion containing particles (average particle size 213 nm) of fluoropolymer 1A and fluoropolymer 2A dispersed in an aqueous medium, with a solid content concentration of 18% by mass.

[0345] The particles in the obtained aqueous dispersion 4 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 338°C, and the crystallization energy is -20 J / g.

[0346] [Example 5]

[0347] In a 1.3L stainless steel pressure reactor, paraffin wax (36g), ultrapure water (157g), feed solution B (617g), ammonium persulfate aqueous solution (1.5g by mass), and sodium lauryl sulfate aqueous solution (0.02% by mass, 40mL) were added to obtain aqueous dispersion F. The temperature was raised to 65℃, and the aqueous dispersion F was stirred. TFE was added until the pressure inside the reactor reached 1.4 MPaG to start polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. After adding 162g of TFE, the reactor was cooled to end the polymerization reaction.

[0348] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 5. Aqueous dispersion 5 is a dispersion containing particles (average particle size 213 nm) of fluoropolymer 1A and fluoropolymer 2A dispersed in an aqueous medium, with a solid content concentration of 18% by mass.

[0349] The particles in the obtained aqueous dispersion 5 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 338°C, and the crystallization energy is -20 J / g.

[0350] [Example 6]

[0351] In a 1.3L stainless steel pressure reactor, paraffin wax (36g), ultrapure water (768g), ammonium persulfate aqueous solution (1% by mass, 7.5g), and sodium lauryl sulfate aqueous solution (0.1% by mass, 5mL) were added to obtain an aqueous dispersion G. At the addition of 8g of TFE, sodium lauryl sulfate aqueous solution (0.1% by mass, 5mL) was added, and this was repeated sequentially with the subsequent addition of 19g of TFE. The temperature was raised to 65°C, and the aqueous dispersion G was stirred. TFE was added until the pressure inside the reactor reached 1.4MPaG to initiate polymerization. Since the pressure inside the reactor decreased as polymerization began, TFE was added to maintain a constant pressure. After adding 162g of TFE, the reactor was cooled to terminate the polymerization reaction.

[0352] After recovering the residual gas in the reactor, the liquid is discharged. This liquid is designated as aqueous dispersion 6. Aqueous dispersion 6 is a dispersion containing particles of fluoropolymer 2A dispersed in an aqueous medium, with a solid content concentration of 18% by mass.

[0353] The particles in the obtained aqueous dispersion 6 were aggregated and separated by filtration to obtain a solid composition containing PTFE. The melting point of PTFE dried at 120°C is 334°C, and the crystallization energy is -26 J / g.

[0354] [Table 5]

[0355]

[0356] As shown in Table 5, it was confirmed that the production of byproducts with hydrophilic groups (compounds represented by formula (S1)) can be suppressed according to this manufacturing method (Examples 1-3).

[0357] It should be noted that the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2023-181599, filed on October 23, 2023, are incorporated herein as a disclosure of the specification of this invention.

Claims

1. A method for manufacturing a fluoropolymer, comprising polymerizing a monomer containing a fluorinated monomer in an aqueous dispersion comprising a hydrocarbon-containing surfactant and an aqueous medium using a polymerization initiator X to produce the fluoropolymer. in, The polymerization initiator X does not have hydrophilic groups and has a molecular weight of less than 200.

2. The method for manufacturing the fluoropolymer according to claim 1, wherein, The polymerization initiator X is a compound represented by formula (X). R 1 -CO-OOR 2 (X) In equation (X), R 1 and R 2 Each is an alkyl group having 1 to 5 carbon atoms.

3. The method for manufacturing the fluoropolymer according to claim 1 or 2, wherein, The fluorinated monomer contains tetrafluoroethylene.

4. The method for manufacturing the fluoropolymer according to claim 1 or 2, wherein, The hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants.

5. An aqueous dispersion comprising a fluoropolymer and an aqueous medium, wherein the fluoropolymer has groups of formula (Y) at the ends of its molecular chains, and the fluoropolymer is polytetrafluoroethylene. R 1 -(O) n - (Y) In formula (Y), R 1 It is an alkyl group with 1 to 4 carbon atoms, where n is 0 or 1.

6. The aqueous dispersion according to claim 5, wherein, In the formula (Y), R 1 It is tert-butyl.

7. The aqueous dispersion according to claim 5 or 6, further comprising a hydrocarbon-containing surfactant.

8. The aqueous dispersion according to claim 7, wherein, The hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants.

9. A solid composition comprising a fluoropolymer having groups of formula (Y) at the ends of its molecular chains. The fluoropolymer is polytetrafluoroethylene. R 1 -(O) n - (Y) In formula (Y), R 1 It is an alkyl group with 1 to 4 carbon atoms, where n is 0 or 1.

10. The solid composition according to claim 9, wherein, In the formula (Y), R 1 It is tert-butyl.

11. The solid composition according to claim 9 or 10, further comprising a hydrocarbon-containing surfactant.

12. The solid composition according to claim 11, wherein, The hydrocarbon-containing surfactant comprises at least one selected from the group consisting of anionic hydrocarbon surfactants and nonionic hydrocarbon surfactants.

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