Method for producing dispersion and method for producing aqueous dispersion

Abstract

This method for producing a dispersion comprises polymerizing a gaseous fluoroolefin in a reaction system that does not contain a fluorine-based emulsifier but contains: water; a polymerization initiator; and a monomer which contains an -SO3X group, -PO3X group, –P(OR)O2X group, or –COOX group (where X represents H, K, Na, or NH4, and R represents an alkyl group) but does not contain fluorine atoms, or a polymer of the monomer. Polymer particles have an average particle diameter of 1–150 nm and contain units derived from the fluoroolefin, the dispersion contains such particles in an amount of less than 10% by mass relative to the total mass.

Description

Method for producing dispersion and method for producing aqueous dispersion

[0001] The present disclosure relates to a method for producing a dispersion and a method for producing an aqueous dispersion.

[0002] Fluoropolymers containing units based on fluoroolefins are used in various industrial fields due to their excellent heat resistance, chemical resistance, flame retardancy, weather resistance, and the like.

[0003] As a method for producing a fluoropolymer, there is a method in which a fluoroolefin is emulsion-polymerized in water using a fluorine-based emulsifier (see Patent Document 1, etc.).

[0004] International Publication No. 2007 / 046377

[0005] The method of Patent Document 1 can obtain an aqueous dispersion containing fluoropolymer particles, which has a small environmental impact. However, depending on the content of the fluorine-based emulsifier, which is an essential component, or depending on the intended use or in some cases, it may be necessary to remove the fluorine-based emulsifier.

[0006] In recent years, further improvements in the dispersibility of fluoropolymer particles in such aqueous dispersions have also been required.

[0007] An object of the present disclosure is to provide a method for efficiently producing an aqueous dispersion containing fluoropolymer particles, which does not require a fluorine-based emulsifier, has a small environmental impact, and has excellent dispersibility in liquid.

[0008] [1] Water and -SO ３ X group, -PO ３ X group, -P(OR)O ２ X group or -COOX group (wherein X is H, K, Na, or NH ４ [2] A method for producing a dispersion, comprising polymerizing a gaseous fluoroolefin in a reaction system containing a monomer having a group consisting of —SO 2 , —SO 3 , —SO 4 , —SO 5 , —SO 6 , —SO 7 , —SO 8 , —SO 9 , —SO 10 , —SO 11 , —SO 12 , —SO 13 , —SO 14 , —SO 15 , —SO 16 , —SO 17 , —SO 18 , —SO 19 , —SO 20 , —SO 21 , —SO 22 , —SO 15 , —SO 16 , —SO 19 , —SO 23 , —SO 15 , —SO 16 , —SO 19 , —SO 24 , —SO 15 , —SO 16 , —SO 18 , —SO 19 , ３ X group, -PO ３X group, -P(OR)O ２ Vinyl monomers having an X group or a —COOX group, —SO ３ X group, -PO ３ X group, -P(OR)O ２ Allyl monomers having an X group or a -COOX group, (meth)acrylic acid, -SO ３ X group, -PO ３ X group, -P(OR)O ２ (Meth)acrylates having an X group or a —COOX group, or —SO ３ X group, -PO ３ X group, -P(OR)O ２The production method of [1], wherein the monomer or the polymer of the monomer is a (meth)acrylamide having an X group or a -COOX group. [3] The production method of [1] or [2], wherein the content of the monomer or the polymer of the monomer in the reaction system is 1.0 ppm by mass or more and 1,000 ppm by mass or less. [4] The production method of any of [1] to [3], wherein the gaseous fluoroolefin is vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, or hexafluoropropylene. [5] The production method of any of [1] to [4], wherein the polymerization is carried out by copolymerizing the gaseous fluoroolefin with ethylene, chlorotrifluoroethylene, propylene, a perfluoroalkyl vinyl ether, or a perfluoroalkyl allyl ether. [6] The production method of any of [1] to [5], wherein the polymerization is carried out by maintaining a temperature of more than 55°C and less than 100°C and a pressure of 0.8 MPaG or more and 2.0 MPaG or less. [7] The production method of any of [1] to [6], wherein the dispersion contains 80% by mass or more of water based on the total mass. [8] A method for producing an aqueous dispersion, comprising polymerizing a gaseous perfluoroolefin in the presence of a polymerization initiator in a reaction system containing no fluorine-based emulsifier, prepared from the dispersion obtained by the production method of [1], to obtain an aqueous dispersion containing fluoropolymer particles, wherein the ratio of the average particle size of the fluoropolymer particles to the average particle size of the polymer containing units based on the fluoroolefin is greater than 1, and the ratio of the particle content in the aqueous dispersion to the particle content in the reaction system is 2 or more. [9] The production method of [8], wherein the liquid viscosity of the reaction system is less than 2 mPa s.

[10] The production method of [8] or [9], wherein the gaseous perfluoroolefin is tetrafluoroethylene or hexafluoropropylene.

[11] The production method of any of [8] to

[10] , wherein the polymerization is carried out by copolymerizing the gaseous perfluoroolefin with a monomer other than the gaseous perfluoroolefin.

[12] The manufacturing method of

[11] , wherein the gaseous monomer other than perfluoroolefin is ethylene, vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, propylene, fluoroalkylethylene, perfluoroalkyl vinyl ether, perfluoroalkyl allyl ether, or a fluoromonomer having a fluorosulfonyl group, a carboxy group, or an alkoxycarbonyl group.

[13] The manufacturing method of any of [8] to

[12] , wherein the average particle size of the fluoropolymer particles is more than 50 nm and not more than 1,000 nm.

[14] The manufacturing method of any of [8] to

[13] , wherein the particle size distribution of the fluoropolymer particles is monomodal and the polydispersity index of the particle sizes of the fluoropolymer particles is 0.5 or less.

[15] The manufacturing method of any of [8] to

[14] , wherein the fluoropolymer particles comprise 5 to 50 mass% of the total mass.

[0009] According to the present disclosure, an aqueous dispersion in which fluoropolymer particles are stably dispersed can be efficiently produced without requiring a fluorine-based emulsifier.

[0010] In this disclosure, the terms have the following meanings:

[0011] A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In the numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.

[0012] In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.

[0013] In this specification, a combination of two or more preferred aspects is a more preferred aspect.

[0014] The term "unit" refers collectively to an atomic group derived from one molecule of the monomer that is formed directly by polymerizing the monomer, and an atomic group obtained by chemically converting a part of the atomic group. Hereinafter, a "unit based on a monomer" will also be referred to simply as a "unit," and a "unit based on monomer A" will also be referred to simply as a "monomer A unit."

[0015] In this specification, the content (mass % or mol %) of each unit relative to all units contained in the polymer is determined by analyzing the polymer by solid-state nuclear magnetic resonance spectroscopy (NMR), and usually, the content of each unit calculated from the amount of each monomer charged substantially coincides with the actual content of each unit.

[0016] In this specification, "gaseous compound" refers to a compound whose boiling point at atmospheric pressure (1013 hPa) is less than 25°C, and "liquid compound" refers to a compound whose boiling point at atmospheric pressure (1013 hPa) is 25°C or higher.

[0017] The manufacturing method of the present disclosure comprises: ３ X group, -PO ３ X group, -P(OR)O ２ X group or -COOX group (wherein X is H, K, Na, or NH ４ and R represents an alkyl group.), and a fluorine-free monomer (hereinafter also referred to as a "hydrophilic monomer") or a polymer of a hydrophilic monomer (hereinafter collectively referred to as a "hydrophilic compound"), and a polymerization initiator, but not a fluorine-based emulsifier. In this reaction system (hereinafter also referred to as reaction system 1), a gaseous fluoroolefin is polymerized to produce a dispersion (hereinafter also referred to as "aqueous dispersion 1") containing particles (hereinafter also referred to as "FO particles") of a polymer containing units based on fluoroolefin (hereinafter also referred to as an "FO polymer") and having an average particle size of 1 to 150 nm, in an amount of less than 10 mass% based on the total mass (hereinafter also referred to as "this method 1").

[0018] The manufacturing method of the present disclosure is a method for producing an aqueous dispersion containing particles (hereinafter also referred to as "F particles") of a fluoropolymer (hereinafter also referred to as "F polymer") prepared from aqueous dispersion 1 by polymerizing gaseous perfluoroolefin in the presence of a polymerization initiator in a reaction system containing no fluorine-based emulsifier, wherein the ratio of the average particle size of the F particles to the average particle size of the FO particles (hereinafter also referred to as "particle size ratio") is greater than 1, and the ratio of the content of F particles in aqueous dispersion 2 to the content of FO particles in the reaction system prepared from aqueous dispersion 1 (hereinafter also referred to as "content ratio") is 2 or more (hereinafter also referred to as "Method 2"). The content ratio is a value calculated from the respective contents (% by mass). Hereinafter, Method 1 and Method 2 may be collectively referred to as "Method".

[0019] According to this method, in the absence of a fluorine-based emulsifier, an aqueous dispersion (aqueous dispersion 1) having excellent dispersibility and containing a predetermined amount of ultrafine particles of a fluoropolymer having excellent dispersibility in liquid can be obtained.

[0020] In a reaction system containing no fluorine-based emulsifier and containing water, gaseous fluoroolefins with low affinity to water are generally difficult to polymerize densely, and polymer particles themselves are not formed, or even if formed, the polymer particles are non-uniform, and their dispersibility in liquid is likely to be extremely low.As a result of intensive research, the present inventors have found that when a reaction system contains a specific hydrophilic compound that does not have fluorine atoms, when gaseous fluoroolefins are polymerized therein, ultrafine polymer particles (FO particles) are generated, and when the content of these particles is within a specific range, an aqueous dispersion (aqueous dispersion 1) in which these particles are extremely well dispersed in liquid can be obtained.

[0021] The present inventors further discovered that when a reaction system is prepared from such an aqueous dispersion and a gaseous perfluoroolefin is polymerized therein, an aqueous dispersion (aqueous dispersion 2) containing particles (F particles) of a fluoropolymer (F polymer) having excellent dispersibility in liquid can be obtained even without the presence of a fluorine-based emulsifier.

[0022] The reason for this is not necessarily clear, but the following may be mentioned.

[0023] In the reaction system prepared from the aqueous dispersion 1 in which FO particles are highly dispersed in the liquid, the introduced gaseous perfluoroolefin has fluorine atoms and is easily adsorbed by the FO polymer with high affinity. In other words, it is thought that the FO particles function highly as a polymerization field. As a result, according to this method, it is thought that it is possible to directly produce an aqueous dispersion (aqueous dispersion 2) containing F particles with excellent dispersibility in the liquid while increasing both the particle size ratio and the content ratio without the presence of a fluorine-based emulsifier. Note that this mechanism of action is more likely to be manifested by the preferred embodiment of this method described below.

[0024] The hydrophilic compound in Method 1 is —SO ３ X group, -PO ３ X group, -P(OR)O ２ A monomer or polymer of the above monomer having an X group or a -COOX group and no fluorine atom, where X is H, K, Na, or NH ４ where R represents an alkyl group. ３ X group, -PO ３ X group, -P(OR)O ２ It means a polymer having units based on a monomer having an X group or a —COOX group and no fluorine atom.

[0025] -SO ３ In other words, the X group is a sulfonic acid group or a sodium ion (Na ＋ ), potassium ions (K ＋ ) or ammonium ion (NH ４ ＋ ) as a counter cation (-SO ３ － ) is a sulfonic acid group.

[0026] Also, -PO ３ In other words, the X group is a phosphonic acid group or a sodium ion (Na ＋ ), potassium ions (K ＋ ) or ammonium ion (NH４ ＋ ) as a counter cation (-PO ３ － ) is a phosphonic acid group.

[0027] Also, -P(OR)O ２ In other words, the X group is a phosphoric acid alkyl ester group. R is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group.

[0028] In other words, the -COOX group is a carboxyl group or a group having a counter cation of sodium ion (Na ＋ ), potassium ions (K ＋ ) or ammonium ion (NH ４ ＋ ) as a counter cation (-COO － ) is a carboxy group.

[0029] The monomer is —SO ３ X group, -PO ３ X group, -P(OR)O ２ Vinyl monomers having an X group or a —COOX group, —SO ３ X group, -PO ３ X group, -P(OR)O ２ Allyl monomers having an X group or a -COOX group, (meth)acrylic acid, -SO ３ X group, -PO ３ X group, -P(OR)O ２ (Meth)acrylates having an X group or a —COOX group, or —SO ３ X group, -PO ３ X group, -P(OR)O ２ (Meth)acrylamides having an X group or a —COOX group are preferred, and —SO ３ X group, -PO ３ X group, -P(OR)O ２ Vinyl monomers having an X group or a —COOX group, (meth)acrylic acid, —SO ３ (Meth)acrylates having an X group or a —COOX group, or —SO ３More preferably, it is a (meth)acrylamide having an X group or a —COOX group, and —SO ３ It is more preferable that the (meth)acrylamide has an X group or a —COOX group, in which case the above-mentioned mechanism of action is more easily exhibited.

[0030] It should be noted that (meth)acrylic acid is a general term for acrylic acid and methacrylic acid, (meth)acrylates are a general term for acrylates and methacrylates, and (meth)acrylamide is a general term for acrylic acid amides and methacrylic acid amides.

[0031] Specific examples of the monomer include vinyl sulfonic acid, vinyl phosphonic acid, acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, fumaric acid, vinyl acetic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-sulfoethyl methacrylic acid, 4-vinylbenzenesulfonic acid, N-tigloylglycine, 6-acrylamidohexanoic acid, 2-methacrylamido-2-methylpropylsulfonic acid, sodium salts thereof, and ammonium salts thereof.

[0032] In the reaction system of Method 1, the hydrophilic compound may be the above-mentioned monomer alone, may be a polymer of the above-mentioned monomer alone, or may be both the above-mentioned monomer and a polymer of the above-mentioned monomer.

[0033] The content of the hydrophilic compound in the reaction system of Method 1 is preferably 1.0 mass ppm or more, more preferably 3 mass ppm or more, and even more preferably 5 mass ppm or more, and is preferably 1000 mass ppm or less, more preferably 500 mass ppm or less, even more preferably 100 mass ppm or less, and particularly preferably 60 mass ppm or less.

[0034] The polymerization initiator in Method 1 is preferably a water-soluble polymerization initiator, more preferably a persulfate, an organic peroxide, or a redox catalyst, and even more preferably a persulfate, which makes it easier for the above-mentioned mechanism of action to be realized.

[0035] Examples of persulfates include ammonium persulfate (hereinafter also referred to as "APS") and potassium persulfate.

[0036] Examples of organic peroxides include disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide.

[0037] Examples of the oxidation-reduction catalyst include catalysts containing an oxidizing agent such as bromic acid or a salt thereof, chloric acid or a salt thereof, persulfuric acid or a salt thereof, permanganic acid or a salt thereof, or hydrogen peroxide, and a reducing agent such as sulfurous acid or a salt thereof, hydrogen sulfite or a salt thereof, thiosulfuric acid or a salt thereof, an organic acid, or an inorganic salt.

[0038] The oxidizing agent includes potassium persulfate, APS, and sodium sulfite.

[0039] Inorganic salts include salts containing sulfate, sulfite or chloride anions and metal ions such as manganese, iron, cobalt, nickel, copper, zinc, cerium and silver, particularly iron (II) sulfate.

[0040] The polymerization initiator may be used alone or in combination of two or more kinds.

[0041] The amount of the polymerization initiator in the polymerization of Method 1 is preferably 0.01 to 5 mass%, more preferably 0.01 to 3 mass%, and even more preferably 0.01 to 2 mass%, based on the total mass of all monomers to be polymerized, including the gaseous fluoroolefin.

[0042] The polymerization in Method 1 is preferably carried out by maintaining the temperature above the half-life temperature of the polymerization initiator or by maintaining the pressure at 0.8 MPaG or higher. It is more preferable to carry out the polymerization by maintaining the temperature above the half-life temperature of the polymerization initiator and the pressure at 0.8 MPaG or higher.

[0043] The half-life temperature of a polymerization initiator is usually a 10-hour half-life temperature, but when the polymerization initiator is a persulfate, it is set to 55°C. Typically, persulfates have a half-life at 55°C of 18 to 120 hours and are polymerization initiators with high activity at 55°C. The polymerization initiator may be made present in the reaction system by a conventional method, and may be added to the reaction system all at once, added in portions, or added continuously to the reaction system.

[0044] The polymerization temperature in Method 1 is preferably higher than 55° C., more preferably 60° C. or higher, and even more preferably 65° C. or higher. The polymerization temperature is preferably lower than 100° C. In this case, the above-described mechanism of action of Method 1 is more likely to be exhibited.

[0045] The polymerization pressure in Method 1 is preferably 0.9 MPaG or higher, more preferably 1.0 MPaG or higher. The polymerization pressure is preferably 4.0 MPa or lower, more preferably 3.5 MPaG or lower. In this case, the above-mentioned mechanism of action of Method 1 is more likely to be exhibited.

[0046] In this specification, "MPaG" refers to gauge pressure, which is the pressure obtained by subtracting atmospheric pressure (0.1013 MPa) from absolute pressure.

[0047] The pressure in the polymerization of Method 1 may be adjusted by introducing a gaseous fluoroolefin into the reaction system in a conventional manner. Specifically, the pressure in the polymerization may be adjusted by continuously or intermittently introducing the gaseous fluoroolefin into the reaction system so that the pressure becomes a predetermined pressure. The pressure may also be adjusted by using a gaseous monomer other than the gaseous fluoroolefin in combination.

[0048] The polymerization time in Method 1 is preferably 90 to 1,000 minutes, more preferably 90 to 700 minutes, in the case of batch processing.

[0049] The reaction system of Method 1 does not contain a fluorine-based emulsifier. In other words, the reaction system of Method 1 is preferably formed without using a fluorine-based emulsifier.

[0050] The fluorine-based emulsifier is an emulsifier having fluorine atoms, different from FO polymers, and specifically refers to a water-soluble fluorine-containing compound or salt thereof having a fluorine-containing organic group (such as a perfluoroalkyl group) and a hydrophilic functional group (such as a carboxy group, a sulfonic acid group, or a phosphonic acid group), more specifically, perfluoroalkylcarboxylic acid, perfluoroalkylsulfonic acid, or a salt thereof. Etheric oxygen atoms may be present between carbon atoms in the molecules of these compounds.

[0051] The reaction system in Method 1 is preferably formed without using a fluorine-containing emulsifier (an emulsifier having a fluorine atom) or an emulsifier not having a fluorine atom. Hereinafter, the emulsifier having a fluorine atom and the emulsifier not having a fluorine atom are collectively referred to as "emulsifier." The content of each emulsifier can be measured using a liquid chromatograph mass spectrometer.

[0052] Examples of emulsifiers include water-soluble emulsifiers. A water-soluble emulsifier means an emulsifier having a solubility of 100 mg or more in 1000 g of water at 25°C, and a water-insoluble emulsifier means an emulsifier other than the above-mentioned water-soluble emulsifiers. The water-soluble emulsifier may be either ionic or nonionic. Examples of emulsifiers include those that do not have a carbon-carbon double bond.

[0053] An emulsifier having no fluorine atoms is an emulsifier having no fluorine atoms and a hydrocarbon group such as an alkyl group as a hydrophobic moiety. It is also possible to replace the hydrogen atoms of the hydrocarbon group of an emulsifier having no fluorine atoms with halogen atoms other than fluorine atoms. Examples of emulsifiers having no fluorine atoms include ionic hydrocarbon emulsifiers and nonionic hydrocarbon emulsifiers.

[0054] Examples of ionic hydrocarbon emulsifiers include anionic hydrocarbon emulsifiers. Anionic hydrocarbon emulsifiers refer to emulsifiers having a negatively charged hydrophilic moiety, such as a carboxylic acid group, a sulfonic acid group, a sulfate group, a phosphonic acid group, or a phosphate group, and a hydrocarbon group, such as an alkyl group, as a hydrophobic moiety. Specific examples of anionic hydrocarbon emulsifiers include sodium dodecyl sulfate, highly branched C10 tertiary carboxylic acid supplied by Resolution Performance Products as Versatic® 10, linear alkyl polyethersulfonate sodium supplied by BASF as the Avanel® S series, and sulfosuccinate emulsifier Lankropol® K8300 available from AkzoNobelSurfaceChemistry LLC.

[0055] Nonionic hydrocarbon emulsifiers are emulsifiers that exhibit surface activity in water without dissociating into ions and have hydrocarbon groups such as alkyl groups as the hydrophobic moiety. The hydrophilic moiety of nonionic hydrocarbon emulsifiers includes water-soluble functional groups such as polyethylene oxide chains obtained by polymerization of ethylene oxide. Examples of nonionic hydrocarbon emulsifiers include polyalkylene oxide block copolymers, such as block copolymers having polyethylene oxide and polypropylene oxide.

[0056] Further, other nonionic hydrocarbon emulsifiers include those described in paragraphs

[0043] to

[0052] of JP-A No. 2016-537499.

[0057] The emulsifier with fluorine atom and the emulsifier without fluorine atom can contain silicon atom.The emulsifier with silicon atom can include siloxane emulsifier.Siloxane emulsifier is a hydrocarbon-containing emulsifier with siloxane skeleton.The siloxane emulsifier can include the emulsifier described in U.S. Patent No. 6,841,616 (Wille et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0058] The emulsifier having a fluorine atom and the emulsifier not having a fluorine atom may be a polymer emulsifier. Examples of the polymer emulsifier include a polymer having a hydrophilic group in its side chain. Examples of such polymer emulsifiers include polymers containing units based on a compound having a site capable of polymerization reaction and a hydrophilic group. Furthermore, even if the polymer does not originally have a hydrophilic group, a polymer obtained by subjecting a polymer containing units based on a compound having a group that can become a hydrophilic group to post-treatment such as hydrolysis may also be used. Specific examples of polymer emulsifiers include polymethyl methacrylate, which is an emulsifier not having a fluorine atom.

[0059] The water content in the reaction system of Method 1 is preferably 60% by mass or more, more preferably 90% by mass or more, and even more preferably 96% by mass or more, based on the total mass of the reaction system. The water content is preferably 100% by mass or less, more preferably 99.9% by mass or less. Even when the water content in the reaction system is within this range, in other words, even when the liquid component in the reaction system is essentially water, an aqueous dispersion of FO particles with excellent dispersibility in liquid can be directly obtained due to the above-described mechanism of action without using a fluorine-based emulsifier.

[0060] The gaseous fluoroolefin in Method 1 is preferably vinyl fluoride, vinylidene fluoride (hereinafter also referred to as "VdF"), tetrafluoroethylene (hereinafter also referred to as "TFE"), or hexafluoropropylene (hereinafter also referred to as "HFP"), and more preferably contains at least TFE.

[0061] The polymerization in Method 1 is preferably carried out by copolymerizing a gaseous fluoroolefin with a monomer other than the gaseous fluoroolefin.

[0062] Examples of the monomer other than the fluoroolefin include ethylene (hereinafter also referred to as "Et"), propylene (hereinafter also referred to as "Pp"), vinyl chloride, vinylidene chloride, chlorotrifluoroethylene (hereinafter also referred to as "CTFE"), perfluoroalkyl vinyl ether (hereinafter also referred to as "PAVE"), perfluoroalkyl allyl ether (hereinafter also referred to as "PAAE"), perfluoro-2-methylene-4-methyl-1,3-dioxolane, perfluoro-2,2-dimethyl-1,3-dioxole, perfluorobutenyl vinyl ether, and perfluoroallyl vinyl ether.

[0063] As for PAVE, CF ２ = CFOCF ３ (hereinafter also referred to as "PMVE"), CF ２ = CFOCF ２ CF ３ (hereinafter also referred to as "PEVE"), CF ２ = CFOCF ２ CF ２ CF ３ (hereinafter also referred to as "PPVE").

[0064] PAAEs include CF ２ =CFCF ２ OCF ３ (hereinafter also referred to as "PMAE"), CF ２ =CFCF ２ CF ２ OCF ３ (hereinafter also referred to as "PEAE").

[0065] The monomer is preferably Et, Pp, vinyl chloride, vinylidene chloride, CTFE, PAVE, or PAAE, more preferably PAVE or PAAE, and even more preferably PMVE, PEVE, or PAAE, which improves the conformational freedom of the FO polymer and makes it easier to exhibit the above-mentioned mechanism of action.

[0066] The FO polymer in Method 1 is a polymer containing units based on a fluoroolefin, and is preferably a polymer containing units based on a gaseous fluoroolefin.

[0067] The fluoroolefins include the fluoroolefins described above, and the preferred ranges are also the same.

[0068] The FO polymer may contain units based on a monomer other than a fluoroolefin. The monomer is preferably a gaseous monomer other than a fluoroolefin. The monomer may be one type or multiple types.

[0069] The monomer may be the fluoroolefin described above, and the preferred ranges are the same.

[0070] The glass transition temperature (hereinafter also referred to as "Tg") of the FO polymer is preferably from -50 to +10°C, more preferably from -45 to +5°C, even more preferably from -40 to +3°C, and particularly preferably from -35 to 0°C. In this case, the above-mentioned mechanism of action is more likely to be exhibited.

[0071] The FO polymer is preferably FEP, FKM, FEPM or FFKM, as described below, and more preferably FKM, FEPM or FFKM, as described below, in which case the above-described mechanism of action is more likely to be exhibited.

[0072] The FO polymer is preferably a polymer obtained by the method described below.

[0073] The FO particles in aqueous dispersion 1 are dispersed in the liquid.

[0074] The average particle size of the FO particles is 1 nm or more, more preferably 10 nm or more, more preferably 25 nm or more, and particularly preferably 30 nm or more. The average particle size of the FO particles is less than 150 nm, more preferably 120 nm or less. Due to the above-mentioned mechanism of action, Method 1 makes it easy to form a dispersion liquid with such particle size.

[0075] The average particle size of particles in this specification is a particle size calculated by analyzing an autocorrelation function obtained by dynamic light scattering using a monodisperse cumulant method.

[0076] The content of FO particles in aqueous dispersion 1 is less than 10% by mass relative to the total mass. The content is preferably 8.0% by mass or less, more preferably 6.0% by mass or less, and even more preferably 5.0% by mass or less. The content is preferably 0.01% by mass or more. Due to the above-mentioned mechanism of action, method 1 makes it easy to form a dispersion with such a content.

[0077] The water content in aqueous dispersion 1 is preferably 80% by mass or more, more preferably more than 90% by mass, based on the total mass. The water content is 99.99% by mass or less, more preferably 95.0% by mass or less. According to Method 1, the above-mentioned mechanism of action makes it easy to form such an aqueous dispersion in which water is essentially the aqueous medium.

[0078] Furthermore, the sum of the F particle content and the water content in the aqueous dispersion 1 is preferably 96% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more, based on the total mass. The upper limit of this sum is 100% by mass. Due to the above-mentioned mechanism of action, this method can obtain a dense aqueous dispersion of F particles with excellent dispersibility in liquid, in which water is essentially the liquid medium.

[0079] The liquid viscosity of the aqueous dispersion 1 is preferably less than 2 mPa·s, more preferably 1.8 mPa·s or less, and even more preferably 1.6 mPa·s or less. The liquid viscosity of the reaction system is preferably 0.8 mPa·s or more, and more preferably 1.0 mPa·s or more.

[0080] The liquid viscosity in this specification is a value determined by measuring the liquid viscosity of the reaction system using a Brookfield viscometer at 25° C. and a rotation speed of 30 rpm. The viscosity measurement is repeated three times, and the average value of the three measured values ​​is used.

[0081] The thixotropy ratio of the aqueous dispersion 1 is preferably 0.95 or more, more preferably 0.98 or more. The thixotropy ratio of the aqueous dispersion 1 is preferably 1.05 or less, more preferably 1.02 or less. The reaction system in this method preferably does not have thixotropy, in other words, the thixotropy ratio is preferably 1.

[0082] In this specification, the thixotropy ratio of a liquid is measured using a Brookfield viscometer, and is calculated from the viscosity of the target liquid measured at 25°C and a rotation speed of 30 rpm and the viscosity of the target liquid measured at a rotation speed of 60 rpm, and is the value obtained by dividing the former viscosity by the latter viscosity.

[0083] Due to the above-mentioned mechanism of action, the present method makes it easy to obtain an aqueous dispersion having such liquid properties.

[0084] A preferred embodiment of the aqueous dispersion 1 is an aqueous dispersion containing no fluorine-based emulsifier, which contains particles of at least one fluoroolefin polymer selected from the group consisting of a polymer containing VdF units and TFE units or HFP units, a polymer containing TFE units and Pp units, a polymer containing TFE units and PAVE units or PAAE units, a polymer consisting of TFE units, a polymer containing TFE units and HFP units, and a polymer containing TFE units and Et units, and water, wherein the content of the particles relative to the total mass is less than 10 mass% and the content of the water is 80 mass% or more, and the particles are dispersed in the liquid with an average particle size of 1 to 150 nm.

[0085] The polymer containing TFE units or HFP units and VdF units is preferably FKM, which is a fluoroelastomer containing 20 to 60 mol % of VdF units and 40 to 80 mol % of TFE units or HFP units. FKM may further contain other units such as PAVE units and Pp units.

[0086] The polymer containing TFE units and Pp units is preferably FEPM, which is a fluoroelastomer containing 30 to 70 mol % of TFE units and 30 to 70 mol % of Pp units. FEPM may further contain other units such as VdF units.

[0087] The polymer containing TFE units and PAVE units or PAAE units is preferably FFKM, a fluoroelastomer containing 40 to 85 mol% of TFE units and 15 to 60 mol% of PAVE units, or PFA, a fluororesin containing 90 to 99.5 mol% of TFE units and 0.5 to 10 mol% of PAVE units. The PAVE units or PAAE units in FFKM are preferably PMVE units, PEVE units, or PAAE units, and more preferably PMVE units. The PAVE units in PFA are preferably PEVE units or PPVE units, and more preferably PPVE units. Furthermore, PFA may further contain other units such as HFP units and fluoroalkylethylene (hereinafter also referred to as "FAE") units.

[0088] The polymer consisting of TFE units is preferably PTFE, which is a fluororesin consisting only of TFE units, or modified PTFE, which is a fluororesin consisting of TFE units and trace amounts of other monomer units. The content of other monomer units in the modified PTFE is preferably less than 0.1 mol%. Examples of other monomer units contained in the modified PTFE include PAVE units, HFP units, FAE units, and CTFE units.

[0089] The polymer containing TFE units and HFP units is preferably FEP, which is a fluororesin containing 55 to 97 mol% of TFE units and 3 to 45 mol% of HFP units. FEP may further contain other units such as PAVE units and FAE units.

[0090] The polymer containing TFE units and Et units is preferably ETFE, which is a fluororesin containing 35 to 65 mol% of TFE units and 35 to 65 mol% of Et units. ETFE may further contain other units such as PAVE units, HFP units, and FAE units.

[0091] In the preferred embodiment, the Tg of the fluoroolefin polymer is preferably in the same range as the Tg of the FO polymer in the aqueous dispersion 1 described above, including the preferred range.

[0092] In the preferred embodiment, the fluoroolefin polymer is preferably FKM, FEPM or FFKM.

[0093] In addition, in the preferred embodiment, the average particle size of the fluoroolefin polymer particles, the content of the particles, the content of water, the range of the sum of the content of the particles and the content of the water relative to the total mass, the liquid viscosity of the aqueous dispersion, and the thixotropy ratio of the aqueous dispersion are the same as those in the above-mentioned aqueous dispersion 1, including the preferred embodiment.

[0094] Due to the above-mentioned mechanism of action, this method can obtain such a preferred embodiment of aqueous dispersion 1. Such a preferred embodiment of aqueous dispersion 1 is preferably used as a polymerization medium for gaseous perfluoroolefins, and more preferably used for preparing a reaction system in this method 2.

[0095] In Method 2, a gaseous perfluoroolefin is polymerized in the presence of a polymerization initiator in a reaction system prepared from Aqueous Dispersion 1 and not containing a fluorine-based emulsifier, to obtain Aqueous Dispersion 2 containing particles of an F polymer (F particles).

[0096] When preparing the reaction system, the dispersion obtained by Method 1 (aqueous dispersion 1) may be used as the reaction system as is, or the component types and contents of aqueous dispersion 1 may be adjusted before use as the reaction system.

[0097] Specific examples of the latter adjustment include adding water to aqueous dispersion 1 to adjust the content of FO particles before using it as a reaction system, adding other components described below to aqueous dispersion 1 to adjust the liquid properties of the reaction system before using it as a reaction system, and treating aqueous dispersion 1 with an ion exchange resin to remove salts derived from the polymerization initiator, etc. before using it as a reaction system.

[0098] The reaction system of Method 2 may or may not contain a hydrophilic compound. In the former case, the content of the hydrophilic compound in the aqueous dispersion 1 of Method 2 is preferably 30 ppm by mass or less, more preferably 10 ppm by mass or less. The content of the hydrophilic compound may be adjusted according to the above-mentioned embodiment.

[0099] The reaction system in Method 2 preferably contains 10 ppm by mass or less of persulfate ions or sulfate ions, and more preferably 5 ppm by mass or less. The lower limit of the content is preferably 0 ppm. When the content is within this range, coloration of the F polymer is suppressed, and the physical properties of aqueous dispersion 2 tend to improve. A specific example of a reaction system containing these ions is when the polymerization initiator in Method 1 is a persulfate. In this case, it is preferable to treat aqueous dispersion 1 with an ion exchange resin to remove these ions.

[0100] In the reaction system of Method 2, the fluoride ion concentration in aqueous dispersion 1 is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less. The lower limit of the fluoride ion content is preferably 0 ppm by mass. A specific example of a reaction system containing fluoride ions is a case where aqueous dispersion 1 contains a by-product containing fluoride ions produced by the reaction of a polymerization initiator (e.g., APS) with a fluoroolefin.

[0101] The polymerization of Method 2 (hereinafter also referred to as "main polymerization") is carried out by polymerizing a gaseous perfluoroolefin. The gaseous perfluoroolefin may be one type or multiple types.

[0102] The gaseous perfluoroolefin is preferably TFE or HFP, and more preferably contains at least TFE.

[0103] The main polymerization may be carried out in the presence of a monomer other than the gaseous perfluoroolefin, and it is preferable to copolymerize the gaseous perfluoroolefin with the monomer.

[0104] The monomer may be a gaseous monomer or a liquid monomer. The monomer may be one type or a plurality of types.

[0105] Examples of the monomer include Et, Pp, vinyl chloride, vinylidene chloride, VdF, CTFE, FAE, PAVE, PAAE, fluoromonomers having a fluorosulfonyl group, a carboxy group, or an alkoxycarbonyl group, perfluoro-2-methylene-4-methyl-1,3-dioxolane, perfluoro-2,2-dimethyl-1,3-dioxole, perfluorobutenyl vinyl ether, and perfluoroallyl vinyl ether.

[0106] As a FAE, CH ２ =CH(CF ２ ) ２ F, CH ２ =CH(CF ２ ) ３ F, CH ２ =CH(CF ２ ) ４ F, CH ２ =CF(CF ２ ) ３ H and CH ２ =CF(CF ２ ) ４ Examples include H.

[0107] Examples of fluoromonomers having a fluorosulfonyl group, a carboxy group, or an alkoxycarbonyl group include CF ２ =CFSO ２ F, CF ２ =CFO(CFCF(CF ３ ))OCF ２ CF ２ SO ２ F, CF ２ = CFO (CF ２ ) ３ COOCH ３ Examples include:

[0108] In this polymerization, the amount of gaseous perfluoroolefin used is preferably 10 mol% or more, more preferably 30 mol% or more, and more preferably 40 mol% or more, based on the total amount of monomers used in the polymerization. The amount of gaseous perfluoroolefin used is preferably 100 mol% or less.

[0109] Furthermore, when a monomer other than gaseous perfluoroolefin is used in the main polymerization, the amount of gaseous perfluoroolefin used is preferably 90 mol% or less, more preferably 70 mol% or less, and preferably 60 mol% or less, based on the total amount of monomers used in the polymerization. In this case, the amount of gaseous perfluoroolefin used is preferably more than 0 mol%.

[0110] In this polymerization, the amount of gaseous perfluoroolefin used is preferably 1 to 60% by mass, more preferably 1 to 50% by mass, and even more preferably 1 to 40% by mass, relative to the content of the liquid components in the reaction system. When a monomer other than gaseous perfluoroolefin is used, the total amount of gaseous perfluoroolefin and the monomer used is preferably within this range.

[0111] The polymerization is preferably carried out in the presence of a polymerization initiator, in other words, the reaction system in the present method preferably contains a polymerization initiator.

[0112] Examples of the polymerization initiator include an oil-soluble radical initiator, a water-soluble polymerization initiator, and a water-soluble oxidation-reduction catalyst.

[0113] Examples of the water-soluble polymerization initiator and the water-soluble redox catalyst include the agents described above.

[0114] Examples of the oil-soluble radical initiator include tert-butyl peroxypivalate and diisopropyl peroxydicarbonate. One type of polymerization initiator may be used, or multiple types may be used.

[0115] The polymerization initiator is preferably an oil-soluble polymerization initiator or a water-soluble radical initiator, and can be selected depending on the type of the target F polymer.

[0116] The amount of the polymerization initiator used is preferably 0.01 to 5% by mass, more preferably 0.01 to 3% by mass, and even more preferably 0.01 to 2% by mass, based on the total mass of the monomers to be polymerized.

[0117] In this polymerization, the gaseous perfluoroolefin may be introduced into the reaction system by a conventional method. Specifically, the gaseous perfluoroolefin may be continuously or intermittently introduced into the reaction system so that the polymerization pressure reaches a predetermined pressure. The polymerization initiator may also be present in the reaction system by a conventional method, and may be added to the reaction system all at once, may be added in portions to the reaction system, or may be added continuously to the reaction system.

[0118] The temperature in the main polymerization is preferably 20° C. or higher. The temperature is preferably lower than 100° C., more preferably 90° C. or lower. The temperature in the main polymerization is preferably lower than the polymerization temperature in Method 1. In this case, an F polymer having better fluoropolymer physical properties is likely to be formed.

[0119] The pressure in the main polymerization is preferably 0.8 MPaG or more, more preferably 0.9 MPaG or more, and is preferably 4.0 MPaG or less, more preferably 0.6 to 3.5 MPaG.

[0120] In the main polymerization, the polymerization time is preferably from 90 to 1,000 minutes, more preferably from 90 to 700 minutes, in the case of batch processing.

[0121] In the reaction of Method 2, the FO particles are dispersed in the liquid in the reaction system.

[0122] The average particle size of the FO particles is preferably 1 nm or more, more preferably 10 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. The average particle size of the FO particles is preferably less than 150 nm, more preferably 120 nm or less. In this case, the above-mentioned mechanism of action is more likely to be exhibited.

[0123] The average particle size of the FO particles in this specification is a particle size calculated by analyzing the autocorrelation function obtained by dynamic light scattering using the monodisperse cumulant method.

[0124] The content of FO particles in the reaction system of Method 2 is preferably 0.01% by mass or more relative to the total mass. The content is preferably 4.0% by mass or less, more preferably 2.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.8% by mass or less. In this case, the above-mentioned mechanism of action is more easily manifested, and the content ratio of the resulting aqueous dispersion is particularly easily increased.

[0125] The water content in the reaction system of Method 2 is preferably 60% by mass or more, more preferably 90% by mass or more, and even more preferably 96% by mass or more, based on the total mass of the reaction system. The water content is preferably 100% by mass or less, and more preferably 99.9% by mass or less. Even when the water content in the reaction system is within this range, in other words, even when the liquid component in the reaction system is essentially water, an aqueous dispersion of F particles with excellent sub-liquid dispersibility can be directly obtained due to the above-described mechanism of action without using a fluorine-based emulsifier.

[0126] The reaction system of Method 2 does not contain a fluorine-containing emulsifier. In other words, the reaction system of Method 2 is preferably formed without using a fluorine-containing emulsifier. The definition of the fluorine-containing emulsifier, including specific examples thereof, is the same as that of Method 1.

[0127] The reaction system in Method 2 is preferably formed without using a fluorine-containing emulsifier (an emulsifier having a fluorine atom) or an emulsifier not having a fluorine atom.

[0128] The liquid viscosity of the reaction system in Method 2 is preferably less than 2 mPa s, more preferably 1.8 mPa s or less, and even more preferably 1.6 mPa s or less. The liquid viscosity of the reaction system is preferably 0.8 mPa s or more, and more preferably 1.0 mPa s or more. In this case, the above-described mechanism of action is more likely to occur.

[0129] In the reaction system of Method 2, the ratio of the liquid viscosity of Aqueous Dispersion 2 to the liquid viscosity of Aqueous Dispersion 1 is preferably greater than 1. Furthermore, the viscosity ratio is preferably less than 5. In this case, the above-described mechanism of action is more likely to occur.

[0130] The thixotropy ratio of the liquid in the reaction system of Method 2 is preferably 0.95 or more, more preferably 0.98 or more. The thixotropy ratio of the liquid is preferably 1.05 or less, more preferably 1.02 or less. The reaction system in Method 2 preferably does not have thixotropy, in other words, the thixotropy ratio is preferably 1. In this case, the above-mentioned mechanism of action is more likely to occur.

[0131] The liquid properties of the reaction system in Method 2 can be controlled by adjusting the aqueous dispersion 1.

[0132] The aqueous dispersion obtained by Method 2 (aqueous dispersion 2) contains particles of the F polymer (F particles) dispersed in the liquid.

[0133] The F polymer as a whole is preferably PTFE, modified PTFE, ETFE, PFA, FEP, FKM, FEPM, or FFKM. The fluoroelastomers FKM, FEPM, and FFKM may further contain a monomer unit having a functional group that forms a crosslinking site, such as an iodine atom, a bromine atom, or a nitrile group (e.g., a fluorovinyl ether monomer unit having the functional group).

[0134] The F polymer and the FO polymer may be polymers composed of the same monomer units and having the same content of the monomer units, and may be the same polymer as a whole. Alternatively, the F polymer and the FO polymer may be polymers composed of the same monomer units but having different content of the monomer units, or may be polymers composed of different monomer units.

[0135] The thixotropy ratio of the aqueous dispersion 2 is preferably 0.95 or more, more preferably 0.98 or more. The thixotropy ratio of the liquid is preferably 1.05 or less, more preferably 1.02 or less. The reaction system in this method preferably does not have thixotropy, in other words, the thixotropy ratio is preferably 1.

[0136] According to this method, due to the above-mentioned mechanism of action, it is easy to directly obtain such an aqueous dispersion having excellent liquid physical properties.

[0137] The average particle size of the F particles in the aqueous dispersion 2 is preferably more than 50 nm, more preferably 70 nm or more, and even more preferably 100 nm or more. The average particle size of the F particles is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 400 nm or less.

[0138] The particle size distribution of the F particles in the aqueous dispersion 2 is preferably unimodal. The polydispersity index of the particle sizes of the F particles is preferably 0.5 or less, and more preferably 0.25 or less. According to this method, a dispersion having such excellent particle properties can be easily obtained due to the above-described mechanism of action.

[0139] The polydispersity index is the width of the particle size distribution determined by analyzing the autocorrelation function obtained by dynamic light scattering using the cumulant method, and the smaller the value, the narrower the particle size distribution of the F particles.

[0140] The content of F particles in aqueous dispersion 2 is preferably more than 4.0% by mass, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the total mass of aqueous dispersion 2. The content of F particles is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0141] The water content in the aqueous dispersion 2 is preferably less than 96.0% by mass, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total mass of the aqueous dispersion 2. The water content is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more.

[0142] Furthermore, the sum of the F particle content and the water content in aqueous dispersion 2 is preferably 90% by mass or more, more preferably 96% by mass or more, based on the total mass. The upper limit of this sum is 100% by mass. Due to the above-mentioned mechanism of action, this method can efficiently obtain an aqueous dispersion containing a high content of dense F particles with excellent dispersibility in liquid, essentially using water as the liquid medium.

[0143] The particle size ratio in Method 2 is the value obtained by dividing the average particle size of F particles in Aqueous Dispersion 2 by the average particle size of FO particles in the reaction system, and may be greater than 1, may be 1.1 or greater, may be 1.2 or greater, may be 1.5 or greater, or may be greater than 2. The particle size ratio may be 10 or less, may be 5 or less, or may be 2 or less.

[0144] The content ratio in Method 2 is the value obtained by dividing the content of F particles in aqueous dispersion 2 by the content of FO particles in the reaction system of Method 2, and is 2 or more, or may be 5 or more, 7 or more, or 10 or more. The content ratio may be 500 or less, 250 or less, 100 or less, 50 or less, or 25 or less. The content ratio is a value calculated from the respective contents (% by mass).

[0145] Due to the above-mentioned mechanism of action, an aqueous dispersion can be produced by selecting the desired particle size ratio and content ratio according to Method 2. The respective values ​​of the particle size ratio and content ratio in Method 2 may be appropriately determined depending on the physical properties of the target F polymer, the physical properties of the target aqueous dispersion, and the intended use.

[0146] For example, when a fluoroelastomer is used as the FO polymer to produce the present dispersion containing particles of an F polymer having excellent fluoroelastomer properties, it is preferable that the particle size ratio and content ratio are 1.2 to 5 and 2 to 100, respectively, and that the average particle sizes of the FO particles and F particles are 25 to 150 nm and 30 to 400 nm, respectively.

[0147] For example, when a fluoroelastomer is used as the FO polymer to produce the present dispersion containing particles of an F polymer with excellent fluororesin properties, it is preferable that the particle size ratio and content ratio are 1.2 to 5 and 2 to 50, respectively, and that the average particle sizes of the FO particles and F particles are 25 to 150 nm and 30 to 300 nm, respectively.

[0148] For example, when a fluororesin is used as the FO polymer and the present dispersion containing particles of an F polymer having excellent fluororesin properties is produced, it is preferable that the particle size ratio and content ratio are 1.5 to 10 and 2 to 100, respectively, and the average particle size of the FO particles and the average particle size of the F particles are 50 to 200 nm and 100 to 400 nm, respectively.

[0149] Examples of fluororesins include PTFE, modified PTFE, ETFE, PFA, and FEP.

[0150] Fluoroelastomers include FKM, FEPM, and FFKM.

[0151] According to Method 2, the polymerization of gaseous perfluoroolefin proceeds precisely due to the above-mentioned mechanism of action, so that the by-production of low molecular weight substances derived from the gaseous perfluoroolefin contained in the dispersion can be suppressed, and particularly when the gaseous perfluoroolefin contains tetrafluoroethylene, the generation amounts of the compound represented by the following formula (S1) and the compound represented by the formula (S2) can be suppressed.

[0152] Formula (S1): H-(CF ２ ) ｎ -COO － M ＋ Formula (S2): H-(CF ２ ) ｎ -SO ３ － M ＋

[0153] In the formula, each M is independently H, Na, K, or NH ４ In the compound represented by formula (S1), n ​​represents an integer of 7 to 11, and in the compound represented by formula (S2), n represents an integer of 8 to 12.

[0154] In the aqueous dispersion 2 in Method 2, the content of the compound represented by formula (S1) and the content of the compound represented by formula (S2) are each preferably 100 mass ppb or less, more preferably 50 mass ppb or less, and even more preferably 25 mass ppb or less, relative to the total mass of the F particles. The lower limit of the content is preferably 0 mass ppb. In other words, the aqueous dispersion in Method 2 preferably does not contain these compounds.

[0155] Aqueous dispersion 2 is an aqueous dispersion in which F particles with high dispersion stability are dispersed, and can be suitably used as a coating agent, binder agent, etc.

[0156] Alternatively, the water contained in the aqueous dispersion 2 may be replaced with an organic solvent such as N-methylpyrrolidone or acetone to prepare a dispersion containing F particles using such an organic solvent as a liquid dispersion medium.

[0157] Alternatively, a powder of F particles may be obtained by aggregating the F particles from the aqueous dispersion 2. The powder of F particles obtained by aggregating may be directly processed into a molded product by melt molding or the like. Furthermore, the powder of F particles obtained by aggregating may be homogenized by melt kneading or the like and processed into a molding base material in the form of pellets, granules, or the like.

[0158] Examples of the flocculation method include mechanical flocculation, freeze flocculation, acid flocculation, base flocculation, and flocculation using a flocculant, and mechanical flocculation, acid flocculation, and flocculation using a flocculant are preferred.

[0159] The aggregation temperature in the freeze aggregation is preferably −20 to 0° C. The aggregation time is preferably 1 hour or more, more preferably 2 hours or more.

[0160] In the case of acid coagulation, a method of adding an acid-containing solution to the dispersion is preferred. Examples of acids include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, and hydrofluoric acid. The acid concentration of the acid-containing solution is preferably 1 to 10% by mass.

[0161] In the case of base coagulation, a method in which a solution containing a base is added to the dispersion is preferred. Examples of the base include sodium hydroxide, potassium hydroxide, and ammonium carbonate. The base concentration in the solution containing the base is preferably 1 to 10% by mass.

[0162] In the case of using a coagulant, it is preferable to add the coagulant to the dispersion, and examples of the coagulant include aluminum sulfate, alum, calcium nitrate, magnesium sulfate, and ammonium carbonate.

[0163] The present disclosure will be described in detail below using examples, but the present disclosure is not limited thereto. The abbreviations in the examples have the following meanings.

[0164] NaAAMPS: sodium 2-acrylamido-2-methyl-1-propanesulfonate TFE: tetrafluoroethylene PMVE: perfluoromethylvinyl ether

[0165] The average particle size of the particles in the dispersion was measured using a laser diffraction / scattering particle size distribution analyzer (ELSZ, manufactured by Otsuka Electronics Co., Ltd.).

[0166] The content of the compound represented by (S1) and the content of the compound represented by (S2) in the dispersion were each calculated by a method using an aqueous dispersion, among the measurement methods using a liquid chromatograph mass spectrometer described in paragraphs

[0710] to

[0732] of WO 2018 / 181904. The apparatus used was an Agilent 1260 series HPLC / 6460S, and the column used was an Imtakt Cadenza CD-C18.

[0167] The sulfate ion concentration in the dispersion was determined by freeze-flocculating the aqueous dispersion, filtering the collected liquid, and analyzing it by ion chromatography. The ion chromatography analysis was performed using an ion chromatograph ICS-5000 (manufactured by Thermo Fisher Scientific). A Dionex IonPac AS-19 separation column and a Dionex IonPac AG-19 guard column were used, and KOH was used as the eluent.

[0168] All reactors used were made of stainless steel.

[0169] [Example 1] Example of production of aqueous dispersion Ultrapure water (713 g), PMVE (55 g), and an aqueous solution containing 0.5 mass% NaAAMPS (3.6 g) were charged into a pressure-resistant reactor (internal volume: 1.3 L), and the temperature was raised to 80 ° C. with stirring. An aqueous ammonium persulfate solution (3.6 mass%, 5 mL) and TFE (9 g) were added to form a reaction system and initiate polymerization. TFE was injected to compensate for the pressure drop associated with polymerization, and the pressure was maintained constant at 0.8 MPaG or higher. When 24 g of TFE was injected, the reactor was cooled to terminate the polymerization. After recovering the gas remaining in the reactor, the contents were extracted, and the resulting solution was a dispersion containing 5.1 mass% of FO polymer particles (average particle size: 102 nm) containing 40 mol% PMVE units and 60 mol% TFE units. The resulting liquid was treated with a cation exchange resin (Diaion SK1BH, manufactured by Mitsubishi Chemical Corporation) and then with an anion exchange resin (Diaion SA10AOH, manufactured by Mitsubishi Chemical Corporation) to obtain a dispersion containing 5.1% by mass of the particles.

[0170] The dispersion (617 g), ultrapure water (157 g), and paraffin wax (36 g) were added to a pressure-resistant reactor (internal volume: 1.3 L), forming a reaction system containing 4.0% by mass of the particles, and the temperature was raised to 70 ° C. and stirred at 260 rpm. TFE was injected until the pressure reached 1.4 MPaG, and disuccinic acid peroxide (0.11 mmol) was added to initiate polymerization. TFE was injected to compensate for the pressure drop associated with the polymerization, and the pressure was maintained at 1.4 MPa. When 90 g of TFE was injected, the reactor was cooled to terminate the polymerization. The polymerization time was 222 minutes, and the polymerization rate calculated from the TFE consumption was 31 g / L / h.

[0171] After the gas remaining in the reactor was collected, the liquid content was extracted to obtain an aqueous dispersion.

[0172] The aqueous dispersion contained 23.8 mass% of fluoropolymer particles (average particle size: 298 nm) containing 99.3 mol% TFE units and 0.7 mol% PMVE units. The aqueous dispersion had excellent liquid properties, such as dispersion stability, and handleability, and the fluoropolymer had excellent physical properties compared to PTFE, a fluororesin. Specifically, the melting point of the fluoropolymer was 338°C. The particle size distribution was monomodal, and the polydispersity index was 0.5 or less.

[0173] The contents of the compounds represented by the formula (S1) and the formula (S2) contained in the aqueous dispersion relative to the total mass of the particles in the aqueous dispersion were both 100 ppb by mass or less.

[0174] The disclosure of Japanese Patent Application No. 2024-099106, filed on June 19, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. Water and -SO ３ X group, -PO ３ X group, -P(OR)O ２ X group or -COOX group (wherein X is H, K, Na, or NH ４ and R represents an alkyl group), and a fluorine-free monomer or a polymer of the monomer, and a polymerization initiator, and no fluorine-based emulsifier are contained in the reaction system, and a dispersion liquid containing polymer particles having an average particle size of 1 to 150 nm and containing units based on the fluoroolefin in an amount of less than 10 mass % relative to the total mass of the dispersion liquid is obtained.

2. The monomer is —SO ３ X group, -PO ３ X group, -P(OR)O ２ Vinyl monomers having an X group or a —COOX group, —SO ３ X group, -PO ３ X group, -P(OR)O ２ Allyl monomers having an X group or a -COOX group, (meth)acrylic acid, -SO ３ X group, -PO ３ X group, -P(OR)O ２ (Meth)acrylates having an X group or a —COOX group, or —SO ３ X group, -PO ３ X group, -P(OR)O ２ 2. The method for producing a dispersion according to claim 1, wherein the (meth)acrylamide is a (meth)acrylamide having an X group or a —COOX group.

3. The method for producing a dispersion liquid according to claim 1, wherein the content of the monomer or the polymer of the monomer in the reaction system is 1.0 mass ppm or more and 1000 mass ppm or less.

4. The method for producing a dispersion according to claim 1, wherein the gaseous fluoroolefin is vinyl fluoride, vinylidene fluoride, tetrafluoroethylene or hexafluoropropylene.

5. The method for producing a dispersion according to claim 1, wherein the polymerization is carried out by copolymerizing the gaseous fluoroolefin with ethylene, chlorotrifluoroethylene, propylene, a perfluoroalkyl vinyl ether, or a perfluoroalkyl allyl ether.

6. The method for producing a dispersion according to claim 1, wherein the polymerization is carried out at a temperature higher than 55°C and lower than 100°C and a pressure maintained at 0.8 MPaG or higher and 2.0 MPaG or lower.

7. The method for producing a dispersion according to claim 1, wherein the dispersion contains water in an amount of 80% by mass or more based on the total mass of the dispersion.

8. A method for producing an aqueous dispersion, which is prepared from the dispersion obtained by the production method described in claim 1, by polymerizing gaseous perfluoroolefin in the presence of a polymerization initiator in a reaction system not containing a fluorine-based emulsifier to obtain an aqueous dispersion containing fluoropolymer particles, wherein the ratio of the average particle size of the fluoropolymer particles to the average particle size of the polymer particles containing units based on the fluoroolefin is greater than 1, and the ratio of the particle content in the aqueous dispersion to the particle content in the reaction system is 2 or more.

9. The method for producing an aqueous dispersion according to claim 8, wherein the liquid viscosity of the reaction system is less than 2 mPa·s.

10. The method for producing an aqueous dispersion according to claim 8, wherein the gaseous perfluoroolefin is tetrafluoroethylene or hexafluoropropylene.

11. The method for producing an aqueous dispersion according to claim 8, wherein the polymerization is carried out by copolymerizing the gaseous perfluoroolefin with a monomer other than the gaseous perfluoroolefin.

12. The method for producing an aqueous dispersion according to claim 11, wherein the gaseous monomer other than perfluoroolefin is ethylene, vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, propylene, fluoroalkylethylene, perfluoroalkyl vinyl ether, perfluoroalkyl allyl ether, or a fluoromonomer having a fluorosulfonyl group, a carboxy group, or an alkoxycarbonyl group.

13. The method for producing an aqueous dispersion according to claim 8, wherein the average particle size of the fluoropolymer particles is more than 50 nm and not more than 1000 nm.

14. The method for producing an aqueous dispersion according to claim 8, wherein the particle size distribution of the fluoropolymer particles is monomodal and the polydispersity index of the particle sizes of the fluoropolymer particles is 0.5 or less.

15. The method for producing an aqueous dispersion according to claim 8, wherein the fluoropolymer particles are contained in an amount of 5 to 50% by weight based on the total weight.