Method for producing particles containing fluorine-containing polymer

Abstract

Provided is a method for producing particles containing a fluorine-containing polymer, said method enabling the production of particles containing a fluorine-containing polymer having a small impurity content.　A method for producing particles containing a fluorine-containing polymer according to the present invention is a method for producing particles containing a fluorine-containing polymer having a group that can be converted into an ion exchange group, the method comprising preparing a liquid composition containing a fluorine-containing polymer and a first solvent, then mixing the liquid composition with a second solvent that is an olefin having a fluorine atom and a chlorine atom, aggregating the fluorine-containing polymer, and forming particles containing the fluorine-containing polymer.

Description

Method for producing particles containing fluorine-containing polymer

[0001] The present invention relates to a method for producing particles containing a fluoropolymer.

[0002] The ion exchange membrane (electrolyte membrane) of a polymer electrolyte fuel cell or a water electrolysis device is obtained by forming a membrane from a fluoropolymer having ion exchange groups such as sulfonic acid groups. Here, the fluoropolymer having ion exchange groups such as sulfonic acid groups is produced by hydrolyzing and converting the fluorosulfonyl groups of a fluoropolymer having groups that can be converted into ion exchange groups such as fluorosulfonyl groups into an acid form. Example 1 of Patent Document 1 describes a method for producing such a fluoropolymer having groups that can be converted into ion exchange groups, in which the fluoropolymer is dissolved in an organic solvent (CF ３ CF ２ CF ２ CF ２ CF ２ CF ２ H), tetrafluoroethylene and CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ SO ２ A polymer solution obtained by copolymerizing a monomer represented by F was added to an organic solvent (HCF ２ CF ２ OCH ２ CF ３ ) to agglomerate the fluoropolymer to obtain particles containing the fluoropolymer.

[0003] Patent No. 6642452

[0004] Particles containing a fluoropolymer having a group that can be converted into an ion-exchange group may contain impurities such as unreacted monomers. If the particles containing a fluoropolymer contain a large amount of impurities, the performance of an ion exchange membrane produced using the particles may be reduced. The present inventors produced particles containing a fluoropolymer having a group that can be converted into an ion-exchange group with reference to the method described in Example 1 of Patent Document 1, and found that there is room for improvement in the content of impurities in the particles.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing particles containing a fluoropolymer, which can produce particles containing a fluoropolymer with a low content of impurities.

[0006] As a result of intensive investigations into the above-mentioned problems, the present inventors have found that when a liquid composition containing a fluoropolymer and a first solvent is prepared, and then the liquid composition is mixed with a second solvent which is an olefin having fluorine atoms and chlorine atoms to aggregate the fluoropolymer, the content of impurities in the resulting particles containing the fluoropolymer is reduced, and have arrived at the present invention.

[0007] That is, the inventors have found that the above problems can be solved by the following configurations. [1] A method for producing particles containing a fluoropolymer having a group convertible to an ion-exchange group, comprising preparing a liquid composition containing the fluoropolymer and a first solvent, and then mixing the liquid composition with a second solvent which is an olefin having fluorine atoms and chlorine atoms to aggregate the fluoropolymer and form particles containing the fluoropolymer. [2] A method for producing particles containing a fluoropolymer according to [1], wherein the olefin has 3 carbon atoms. [3] A method for producing particles containing a fluoropolymer according to [1] or [2], wherein the olefin has a normal boiling point of 14 to 89°C. [4] A method for producing particles containing a fluoropolymer according to any of [1] to [3], wherein the fluoropolymer contains units based on tetrafluoroethylene and units based on a compound represented by formula (1): Formula (1) CF ２ =CF-L-(A) ｎIn formula (1), L is an (n+1)-valent perfluorohydrocarbon group which may contain an etheric oxygen atom, A is a group which can be converted to a sulfonic acid functional group, and n is 1 or 2. [5] A method for producing particles comprising a fluoropolymer according to [4], wherein the first solvent comprises at least one selected from the group consisting of a compound represented by formula (1) and an organic solvent. [6] A method for producing particles comprising a fluoropolymer according to any of [1] to [5], wherein the mass ratio of the content of the fluoropolymer to the content of the first solvent in the liquid composition is 0.050 to 0.43. [7] A method for producing particles comprising a fluoropolymer according to any of [1] to [6], wherein, when the liquid composition and the second solvent are mixed, the mass ratio of the mass of the second solvent to the mass of the first solvent in the liquid composition is 1.0 to 8.0. [8] The method for producing particles comprising a fluoropolymer according to any one of [1] to [7], wherein the content of the first solvent is 70% by mass or more and 95% by mass or less based on the total mass of the liquid composition. [9] The method for producing particles comprising a fluoropolymer according to any one of [1] to [8], wherein the average particle size of the particles is 38 μm or more and 10,000 μm or less.

[10] The method for producing particles comprising a fluoropolymer according to any one of [1] to [9], wherein the mixing is carried out using the liquid composition having a temperature of 20°C or more and 60°C or less and the second solvent having a temperature of -15°C or more and 30°C or less.

[0008] According to the present invention, there can be provided a method for producing particles containing a fluoropolymer, which can produce particles containing a fluoropolymer with a low content of impurities.

[0009] The definitions of the following terms apply throughout the present specification and claims unless otherwise specified. An "ion exchange group" is a group that can exchange at least a portion of the ions contained in this group with other ions, and examples thereof include the sulfonic acid functional group and carboxylic acid functional group shown below. A "sulfonic acid functional group" is a sulfonic acid group (-SO ３ Here, the form of the sulfonate group is, for example, (—SO ３－ ) Ma ＋ , (-SO ３ － ) ２ Mb ２＋ , and (-SO ３ － ) ３ Mc ３＋ (However, Ma ＋ is an alkali metal ion or a quaternary ammonium cation, and Mb ２＋ is a divalent metal ion, Mc ３＋ is a trivalent metal ion.) When there are two ligands, the number of ion exchange groups is counted as two, and when there are three ligands, the number of ion exchange groups is counted as three. "Carboxylic acid type functional group" means a carboxylic acid group (-COOH) or a carboxylic acid salt group. Here, the form of the carboxylic acid salt group can be, for example, (-COO － ) Ma ＋ , (-COO － ) ２ Mb ２＋ , and (-COO － ) ３ Mc ３＋ (However, Ma ＋ is an alkali metal ion or a quaternary ammonium cation, and Mb ２＋ is a divalent metal ion, Mc ３＋ is a trivalent metal ion.) When there are two ligands, the number of ion exchange groups is counted as two, and when there are three ligands, the number of ion exchange groups is counted as three. "Groups that can be converted into ion exchange groups" means groups that can be converted into ion exchange groups by treatment such as hydrolysis treatment or acidification treatment. "Groups that can be converted into sulfonic acid functional groups" means groups that can be converted into sulfonic acid functional groups by treatment such as hydrolysis treatment or acidification treatment. "Groups that can be converted into carboxylic acid functional groups" means groups that can be converted into carboxylic acid functional groups by known treatment such as hydrolysis treatment or acidification treatment.

[0010] A "unit" in a polymer refers to an atomic group derived from one molecule of a monomer formed by polymerization of the monomer. The unit may be an atomic group formed directly by the polymerization reaction, or may be an atomic group in which part of the atomic group is converted into a different structure by treating the polymer obtained by the polymerization reaction. In the following, units derived from individual monomers may be referred to by the name of the monomer followed by "unit" in some cases.

[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] [Method for producing particles containing fluoropolymer] The method for producing a fluoropolymer of the present invention is a method for producing particles containing a fluoropolymer (hereinafter also referred to as "polymer F") having a group convertible to an ion exchange group, and comprises preparing a liquid composition containing the polymer F and a first solvent, and then mixing the liquid composition with a second solvent which is an olefin having fluorine atoms and chlorine atoms to aggregate the polymer F and form particles containing the polymer F. According to this production method, particles containing a fluoropolymer with a low impurity content can be produced. The details of the reason for this have not yet been clarified, but it is thought that by using the second solvent to aggregate the polymer F, components other than the polymer F (for example, the monomer used in the production of polymer F, oligomers produced in the production of polymer F, various solvents, etc.) are prevented from being incorporated into the particles. Furthermore, it is thought that by using the second solvent to aggregate the polymer F, when the aggregated polymer F is subjected to treatment such as washing or drying, components other than the polymer F in the particles are easily removed.

[0013] [Liquid Composition] The liquid composition contains polymer F and a first solvent. The liquid composition may be a solution in which polymer F is dissolved in the first solvent, or a dispersion in which polymer F is dispersed in the first solvent. The turbidity of the liquid composition is preferably 500 NTU or less. A liquid composition with such turbidity can be said to be a solution in which polymer F is dissolved in the first solvent, or a dispersion in which polymer F is dispersed in the first solvent. Here, the turbidity of the liquid composition can be measured using a turbidimeter employing a scattered light measurement method using the liquid composition immediately after being obtained in step 1 described below. Specifically, the turbidity is determined by measuring 90° scattered light at room temperature (measurement wavelength: 850 nm) using a portable turbidimeter TN-100 manufactured by EUTECH INSTRUMENTS. 10 mL of the sample to be measured is placed in a borosilicate glass vial (diameter 25 mm, height 51 mm). Additionally, a calibration curve can be generated using calibration solutions containing EPA-compliant polymer-based standards (0.02 NTU, 20.0 NTU, 100 NTU, 800 NTU).

[0014] <Polymer F> Polymer F is not particularly limited as long as it is a polymer having a fluorine atom and a group that can be converted into an ion exchange group. However, in terms of obtaining better effects of the present invention, polymer F-1 or polymer F-2 shown below is preferred.

[0015] (Polymer F-1) Polymer F-1 is a copolymer containing units based on a fluorine-containing olefin and units based on a fluorine-containing monomer having a group that can be converted into an ion-exchange group, and is more preferably a copolymer containing units based on a fluorine-containing olefin (preferably tetrafluoroethylene) and units based on a fluorine-containing monomer having a group that can be converted into a sulfonic acid functional group (preferably a compound represented by formula (1) described below). Polymer F-1 preferably does not have a cyclic ether structure.

[0016] Examples of fluorine-containing olefins include fluoroolefins having 2 to 3 carbon atoms and one or more fluorine atoms in the molecule. Specific examples of fluoroolefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among these, TFE is preferred in terms of the production cost of the monomer, reactivity with other monomers, and excellent properties of the resulting polymer F-1. One type of fluorine-containing olefin may be used alone, or two or more types may be used in combination.

[0017] The content of units based on fluorine-containing olefin is preferably 11% by mass or more, more preferably 38% by mass or more, and preferably 59% by mass or less, more preferably 55% by mass or less, based on all units in polymer F-1.

[0018] Examples of the fluorine-containing monomer having a group that can be converted into an ion-exchange group include compounds that have one or more fluorine atoms in the molecule, an ethylenic double bond, and a group that can be converted into a sulfonic acid functional group. As the fluorine-containing monomer having a group that can be converted into an ion-exchange group, a compound represented by formula (1) is preferred in terms of the production cost of the monomer, reactivity with other monomers, and excellent properties of the resulting polymer F-1. Formula (1) CF ２ =CF-L-(A) ｎ

[0019] L is an (n+1)-valent perfluorohydrocarbon group which may contain an etheric oxygen atom. The etheric oxygen atom may be located at the terminal of the perfluorohydrocarbon group or between carbon atoms. The number of carbon atoms in the (n+1)-valent perfluorohydrocarbon group is preferably 1 or more, more preferably 2 or more, and preferably 20 or less, more preferably 10 or less. L is preferably an (n+1)-valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, and more preferably a divalent perfluoroalkylene group which may contain an etheric oxygen atom in the embodiment where n = 1, or a trivalent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom in the embodiment where n = 2. The divalent perfluoroalkylene group may be either linear or branched.

[0020] A is a group that can be converted into a sulfonic acid functional group. The group that can be converted into a sulfonic acid functional group is preferably a functional group that can be converted into a sulfonic acid functional group by hydrolysis. Specific examples of groups that can be converted into a sulfonic acid functional group include -SO ２ F, -SO ２ Cl, —SO ２ Br is an example.

[0021] n is 1 or 2.

[0022] The compound represented by formula (1) is preferably a compound represented by formula (1-1), a compound represented by formula (1-2), a compound represented by formula (1-3), or a compound represented by formula (1-4). ２ =CF-O-R ｆ１ -A Formula (1-2) CF ２ =CF-R ｆ１ -A

[0023]

[0024]

[0025] R ｆ１is a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 10 or less.

[0026] R ｆ２ is a single bond or a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 10 or less.

[0027] R ｆ３ is a single bond or a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 10 or less.

[0028] r is 0 or 1. m is 0 or 1.

[0029] The definition of A in the formula is as described above.

[0030] As the compound represented by formula (1-1) and the compound represented by formula (1-2), a compound represented by formula (1-5) is preferred. ２ =CF-(CF ２ ) ｘ -(OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ３ F x is 0 or 1, y is an integer from 0 to 2, z is an integer from 1 to 4, and Y is F or CF ３ is.

[0031] Specific examples of the compound represented by formula (1-1) include the following compounds. In the formula, w is an integer of 1 to 8, and x is an integer of 1 to 5. CF ２ =CF-O-(CF ２ ) ｗ -SO ２ FCF ２ =CF-O-CF ２ CF (CF３ )-O-(CF ２ ) ｗ -SO ２ FCF ２ =CF-[O-CF ２ CF (CF ３ )] ｘ -SO ２ F

[0032] Specific examples of the compound represented by formula (1-2) include the following compounds: In the formula, w is an integer of 1 to 8. CF ２ =CF-(CF ２ ) ｗ -SO ２ FCF ２ =CF-CF ２ -O-(CF ２ ) ｗ -SO ２ F

[0033] The compound represented by formula (1-3) is preferably a compound represented by formula (1-3-1).

[0034]

[0035] R ｆ４ is a linear perfluoroalkylene group having 1 to 6 carbon atoms, and R ｆ５ represents a single bond or a linear perfluoroalkylene group having 1 to 6 carbon atoms which may contain an oxygen atom between the carbon atoms. The definitions of r and A are as described above.

[0036] Specific examples of the compound represented by formula (1-3-1) include the following.

[0037]

[0038] The compound represented by formula (1-4) is preferably a compound represented by formula (1-4-1).

[0039]

[0040] R in the formula ｆ１ , R ｆ２ and A are defined as above.

[0041] Specific examples of the compound represented by formula (1-4-1) include the following.

[0042]

[0043] The fluorine-containing monomer having a group that can be converted into an ion-exchange group may be used alone or in combination of two or more kinds.

[0044] The content of units based on a fluorine-containing monomer having a group convertible to an ion-exchange group is preferably 41% by mass or more, more preferably 45% by mass or more, and is preferably 89% by mass or less, more preferably 62% by mass or less, based on all units of polymer F-1.

[0045] Polymer F-1 may be produced using monomers other than the above monomers (hereinafter also referred to as "other monomers"). Specific examples of other monomers include CF ２ = CFR ｆ６ (However, R ｆ６ is a perfluoroalkyl group having 2 to 10 carbon atoms, CF ２ =CF-OR ｆ７ (However, R ｆ７ is a perfluoroalkyl group having 1 to 10 carbon atoms, CF ２ = CFO (CF ２ ) ｖ CF = CF ２ (wherein v is an integer of 1 to 3.) The content of units based on other monomers is preferably 30% by mass or less based on the total units of polymer F-1, in order to maintain ion exchange performance.

[0046] (Polymer F-2) Polymer F-2 is a fluorine-containing polymer having units derived from a monomer having a cyclic ether structure and having an ion-exchange group, and is preferably a copolymer having units derived from a monomer having a cyclic ether structure and units derived from a fluorine-containing monomer having a group convertible to an ion-exchange group. Specific examples of the monomer having a cyclic ether structure include monomer m11, monomer m12, monomer m21, and monomer m22.

[0047] Monomer m11 is a monomer represented by formula (m11), and preferred embodiments of monomer m11 include formulae (m11-1) to (m11-4).

[0048]

[0049] R １１ is a divalent perfluoroalkylene group which may have an ether-bonded oxygen atom. When the perfluoroalkylene group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. The oxygen atom may be located between the carbon-carbon bonds of the perfluoroalkylene group, or at the carbon atom bond terminal. The perfluoroalkylene group may be linear or branched, but is preferably linear. R １２ , R １３ , R １５ and R １６ R each independently represents a monovalent perfluoroalkyl group which may have an ether-bonded oxygen atom or a fluorine atom. １５ and R １６ In view of high polymerization reactivity, it is preferable that at least one of R is a fluorine atom, and it is more preferable that both of R are fluorine atoms. １４ represents a monovalent perfluoroalkyl group which may have an ether-bonded oxygen atom, a fluorine atom, or —R １１ SO ２ It is a group represented by F. When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. In addition, the oxygen atom may be located between the carbon-carbon bonds of the perfluoroalkyl group, or may be located at the carbon atom bond terminal. The perfluoroalkyl group may be linear or branched, but is preferably linear. In formula (m11), two R １１ If it contains two R １１ may be the same or different from each other.

[0050] Monomer m12 is a monomer represented by formula (m12), and preferred embodiments of monomer m12 include formulae (m12-1) to (m12-2).

[0051]

[0052] R ２１ is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms and having an ether-bonding oxygen atom between the carbon-carbon bond. When the perfluoroalkylene group has an ether-bonding oxygen atom, the number of oxygen atoms may be one or more. The perfluoroalkylene group may be linear or branched, but is preferably linear. R ２２ represents a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms and an ether-bonded oxygen atom between the carbon-carbon bonds, or -R ２１ SO ２ It is a group represented by F. When the perfluoroalkyl group has an ether bond oxygen atom, the number of oxygen atoms may be one or two or more. The perfluoroalkyl group may be linear or branched, but is preferably linear. In formula (m12), two R ２１ If it contains two R ２１ may be the same or different from each other.

[0053] Monomer m21 is a monomer represented by formula (m21), and preferred embodiments of monomer m21 include formulae (m21-1) to (m21-2).

[0054]

[0055] R ４１ , R ４２ , R ４３ , R ４４ , R ４５ and R ４６are each independently a monovalent perfluoroalkyl group which may have an ether-bonded oxygen atom or a fluorine atom. When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. The oxygen atom may be located between the carbon-carbon bonds of the perfluoroalkyl group, or at the carbon atom bond terminal. The perfluoroalkyl group may be linear or branched, but is preferably linear. R ４５ and R ４６ In view of high polymerization reactivity, it is preferable that at least one of the groups is a fluorine atom, and it is more preferable that both of the groups are fluorine atoms.

[0056] Monomer m22 is a monomer represented by formula (m22), and preferred embodiments of monomer m22 include formulae (m22-1) to (m22-11).

[0057]

[0058] s is 0 or 1, and is preferably 0. ５１ and R ５２ are each independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by linking together (when s is 0). ５３ and R ５４ are each independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms. ５５ is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. ５５ A fluorine atom is preferred in terms of high polymerization reactivity. The perfluoroalkyl group and perfluoroalkoxy group may be linear or branched, but are preferably linear.

[0059] The content of units based on a monomer having a cyclic ether structure is preferably 30% by mass or more, more preferably 48% by mass or more, and is preferably 70% by mass or less, more preferably 63% by mass or less, based on the total units of polymer F-2.

[0060] Specific examples of the fluorine-containing monomer having a group convertible to an ion-exchange group are the same as those of the fluorine-containing monomer having a group convertible to an ion-exchange group in Polymer F-1. The content of units based on the fluorine-containing monomer having a group convertible to an ion-exchange group is preferably 20% by mass or more, more preferably 28% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, based on the total units of Polymer F-2.

[0061] Polymer F-2 may have units based on a fluorine-containing olefin. Specific examples of the fluorine-containing olefin are the same as those for Polymer F-1. The content of units based on a fluorine-containing olefin (particularly TFE) is preferably 0% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, based on all units of Polymer F-2.

[0062] (Content of Polymer F) The content of Polymer F is preferably 5% by mass or more, and more preferably 14% by mass or more, relative to the total mass of the liquid composition, from the viewpoint of enabling better aggregation of Polymer F, and is preferably 30% by mass or less, and more preferably 20% by mass or less, from the viewpoint of better solubility or dispersibility in the first solvent.

[0063] (Physical Properties of Polymer F) The TQ value of Polymer F is preferably 150° C. or higher, more preferably 170° C. or higher, and even more preferably 200° C. or higher, and is preferably 350° C. or lower, more preferably 340° C. or lower, and even more preferably 300° C. or lower. The TQ value is a value related to the molecular weight of the polymer, and is ３ The TQ value of Polymer F is expressed as a temperature at which the melting point is increased / second, and is determined by the following method. The TQ value of Polymer F is determined by the method described in the Examples section below.

[0064] When the groups of polymer F that can be converted into ion exchange groups are converted into ion exchange groups by known treatments such as hydrolysis treatment and acidification treatment, a fluoropolymer having ion exchange groups (hereinafter also referred to as "polymer H") is obtained. The ion exchange capacity of polymer H is preferably 0.8 meq / g dry resin or more, more preferably 0.9 meq / g dry resin or more, and even more preferably 1.0 meq / g dry resin or more, and preferably 2.5 meq / g dry resin or less, more preferably 2.2 meq / g dry resin or less, and even more preferably 2.0 meq / g dry resin or less. The ion exchange capacity of polymer H can be determined by the method described in the Examples section below.

[0065] (Method for Producing Polymer F) One example of the method for producing Polymer F is a method of copolymerizing the above-mentioned monomers in a reactor in the presence of a polymerization initiator. Specific examples of the copolymerization method include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization.

[0066] In the case of a solution polymerization method, specific examples of the polymerization solvent include solvents such as chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers, etc. Here, when polymer F is produced by a solution polymerization method, the polymerization solvent may be a first solvent (described later) contained in the liquid composition.

[0067] Specific examples of the polymerization initiator include diacyl peroxides (disuccinic acid peroxide, benzoyl peroxide, perfluorobenzoyl peroxide, lauroyl peroxide, bis(pentafluoropropionyl) peroxide, etc.), azo compounds (2,2'-azobis(2-amidinopropane) hydrochlorides, 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobisisobutyrate, azobisisobutyronitrile, etc.), and peroxyesters. peroxydicarbonates (e.g., t-butyl peroxyisobutyrate, t-butyl peroxypivalate), peroxydicarbonates (e.g., diisopropyl peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate), hydroperoxides (e.g., diisopropylbenzene hydroperoxide, t-butyl hydroperoxide), dialkyl peroxides (e.g., di-t-butyl peroxide, perfluoro-di-t-butyl peroxide), and the like.

[0068] The polymerization initiator may be used in the form of a solution dissolved in a solvent (hereinafter also referred to as an "initiator solution"). The solvent contained in the initiator solution may be the first solvent (described below) contained in the liquid composition.

[0069] The amount of the polymerization initiator added is preferably 0.0001 part by mass or more, more preferably 0.001 part by mass or more, and is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, per 100 parts by mass of the monomer component.

[0070] The monomers and the polymerization initiator may be added to the reactor continuously or sequentially. The amounts of the monomers added may be appropriately determined so that the content of each monomer unit in the polymer F falls within the above-mentioned ranges.

[0071] The copolymerization temperature is preferably 20° C. or higher, more preferably 30° C. or higher, and preferably 150° C. or lower, more preferably 130° C. or lower. The polymerization pressure (gauge pressure) is preferably 0.05 MPa [gauge] or higher, more preferably 0.5 MPa [gauge] or higher, and preferably 2 MPa [gauge] or lower, more preferably 1.5 MPa [gauge] or lower.

[0072] <First Solvent> The first solvent is a solvent (good solvent) that dissolves or disperses polymer F. Specific examples of the first solvent include organic solvents, unreacted monomers used in the production of polymer F, and oligomers generated during the production of polymer F. One type of first solvent may be used alone, or two or more types may be used in combination. Among these, organic solvents and unreacted monomers used in the production of polymer F are preferred in terms of availability, cost, boiling point, separation and recovery, etc.

[0073] The organic solvent is preferably a fluorine-based solvent or a hydrocarbon-based solvent from the viewpoint of excellent solubility or dispersibility of polymer F. The number of carbon atoms in the fluorine-based solvent is preferably 1 to 8, more preferably 2 to 7, and even more preferably 3 to 6, because if the number of carbon atoms is too small, the boiling point is low and the solvent recyclability and handling at room temperature are insufficient, while if the number of carbon atoms is too large, the boiling point is high and recycling of the solvent and drying of the polymer after coagulation and separation becomes difficult. The normal boiling point of the fluorine-based solvent is preferably 20 to 200°C, more preferably 34 to 140°C, and even more preferably 48 to 83°C, because if the normal boiling point is too low, the solvent recyclability and handling at room temperature are insufficient, while if the normal boiling point is too high, recycling of the solvent and drying of the polymer after coagulation and separation becomes difficult. Specific examples of the fluorine-based solvent include CF ３ (CF ２ ) ４ CF ２ H, C.F. ３ (CF ２ ) ６ CF ２ H, HCF ２ (CF ２ ) ２ CF ２ H, C.F. ３ CF ２ CHFCHFCF ３ , C.F. ３ CF (CF ３ ) CHFCHFCF ３ , C.F. ３ CH ２ CF ２ CH ３ , 1,1,2,2,3,3,4-heptafluorocyclopentane, and other hydrofluorocarbons; ClCF ２ CF ２CHFCl (1,3-dichloro-1,1,2,2,3-pentafluoropropane), CF ３ CF ２ CHCl ２ , C.H. ３ CCl ２ Hydrochlorofluorocarbons such as F; HCF ２ CF ２ OCH ２ CF ３ , n-C ３ F ７ OCH ３ , n-C ３ F ７ OCHFCF ３ , n-C ３ F ７ OCH ２ CF ３ , n-C ４ F ９ OCH ３ , iso-C ４ F ９ OCH ３ , n-C ４ F ９ OCH ２ CH ３ , n-C ４ F ９ OCH ２ CF ３ , C.F. ３ OCF (CF ３ )CF ２ OCH ３ , n-C ３ F ７ OCF (CF ３ )CF ２ OCHFCF ３ Hydrofluoroethers such as CCl ３ F, CCl ２ F ２ , CClF ２ CClF ２ , Cl ２ FCCClF ２ Chlorofluorocarbons such as (CF ３ ) ２ CFC(O)CF(CF ３ ) ２ , C.F. ３ CF ２ CF ２C(O)CF(CF ３ ) ２ Perfluoroketones such as CF ３ CCl=CH ２ , C.F. ３ Z-isomer of CF = CHCl, CF ３ E-isomer of CH═CHCl, CF ３ Z-isomer of CH═CHCl, CF ３ CCl=CHCl, CHF ２ E-isomer of CF=CHCl, CHF ２ Z-isomer of CF=CHCl, CHF ２ CF ２ CF ２ Hydrochlorofluoroolefins such as Z-isomer of CF═CHCl; CF ３ CF=CCl ２ , C.F. ３ CCl = CCl ２ Chlorofluoroolefins such as:

[0074] Specific examples of hydrocarbon solvents include pentane, hexane, heptane, octane, hexadecane, isohexane, isooctane, isononane, isododecane, cycloheptane, cyclohexane, bicyclohexyl, benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, o-diethylbenzene, m-diethylbenzene, p-diethylbenzene, n-butylbenzene, sec-butylbenzene, and tert-butylbenzene, methanol, ethanol, and tert-butanol.

[0075] A specific example of the unreacted monomer used in the production of polymer F is the compound represented by formula (1) above. A specific example of the oligomer formed during the production of polymer F is an oligomer formed by polymerizing the fluorine-containing olefin and the compound represented by formula (1) above, and the molecular weight thereof is usually several tens of thousands or less.

[0076] The swelling degree of the first solvent relative to polymer F is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 7% by mass or more, from the viewpoints of providing excellent dispersibility and solubility in the liquid composition and enabling better aggregation of polymer F in step 2 described below. The swelling degree of polymer F in the first solvent is determined by the following procedure. Polymer F particles are hot-pressed to obtain a film with a thickness of 100 μm. A 20 mm x 20 mm sample is cut from the film, and the dry mass (W1) of the sample is measured. The sample is immersed in 50 g of the first solvent at 25°C in a sealed environment for 16 hours. The sample is removed from the solvent, the solvent is quickly wiped off, and the swollen mass (W2) of the sample is measured. The swelling degree is calculated based on the measured dry mass (W1) and swollen mass (W2) using the following formula: Swelling degree (%) = (W2 - W1) / W1 x 100

[0077] The first solvent preferably contains at least one selected from the unreacted monomer (preferably a compound represented by formula (1)) used in the production of polymer F and an organic solvent (preferably a fluorine-based solvent), in order to provide better dispersibility or solubility of polymer F.

[0078] The content of the first solvent is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, relative to the total mass of the liquid composition, from the viewpoint of better solubility or dispersibility of polymer F, and also from the viewpoint of suppressing excessive fine particle formation of the polymer in step 2, improving filterability in step 3, and saving the amount of solvent used during aggregation, it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. The mass ratio of the content of polymer F to the content of the first solvent (content of polymer F / content of first solvent) is preferably 0.050 or more, more preferably 0.054 or more, and even more preferably 0.060 or more, from the viewpoint of suppressing excessive fine particle formation of the polymer in step 2, improving filterability in step 3, and saving the amount of solvent used during aggregation, it is preferably 0.43 or less, more preferably 0.24 or less, and even more preferably 0.10 or less.

[0079] [Second Solvent] The second solvent is an olefin having a fluorine atom and a chlorine atom, and is a solvent (poor solvent) used to form particles of polymer F by agglomerating polymer F in a liquid medium.

[0080] Specific examples of the second solvent include CF ３ CCl=CH ２ (14°C), CF ３ CF=CHCl Z form (15°C), CF ３ E-isomer of CH═CHCl (18°C), CF ３ Z-isomer of CH═CHCl (39°C), CF ３ CCl=CHCl (54°C), CHF ２ E-isomer of CF=CHCl (47-48°C), CHF ２ Z-isomer of CF=CHCl (54°C), CHF ２ CF ２ CF ２ Hydrochlorofluorocarbons such as CF═CHCl Z form (89° C.); CF ３ CF=CCl ２ (46°C), CF ３ CCl = CCl ２ (88°C). The numbers in parentheses in the above specific examples represent standard boiling points (boiling points under 1 atmosphere). ２ The boiling point of a mixture of E- and Z-isomers of CF═CHCl (the content of E-isomer is 10% by mass or less) is 54° C. One type of second solvent may be used alone, or two or more types may be used in combination.

[0081] The number of carbon atoms in the olefin that is the second solvent is preferably 2 to 8, more preferably 2 to 5, and even more preferably 3, in terms of achieving better effects of the present invention and better aggregation of the polymer F.

[0082] The standard boiling point of the olefin as the second solvent is preferably 14°C or higher, more preferably 15°C or higher, and even more preferably 39°C or higher, in order to ensure sufficient handleability at room temperature, and is preferably 89°C or lower, more preferably 88°C or lower, and even more preferably 54°C or lower, in order to facilitate separation of the polymer F from the polymerization medium.

[0083] [Steps] In this specification, the step of preparing a liquid composition containing polymer F and a first solvent is also referred to as "step 1." Furthermore, the step of mixing the liquid composition with a second solvent to aggregate the polymer F and form particles containing polymer F is also referred to as "step 2." Each step will be described in detail below.

[0084] <Step 1> The method for preparing the liquid composition is not particularly limited, but examples thereof include the following method.

[0085] An example of a method for preparing a liquid composition is to obtain a dispersion or solution in which polymer F is dispersed or dissolved in unreacted monomers or an organic solvent used in the production of polymer F by bulk polymerization, and use the resulting dispersion or solution as the liquid composition. In this case, the unreacted monomers and the organic solvent correspond to the first solvent. The dispersion or solution obtained by bulk polymerization may further contain, in addition to polymer F and unreacted monomers, a component corresponding to the first solvent, such as the above-mentioned oligomer.

[0086] Another example of a method for preparing a liquid composition is to obtain a dispersion or solution in which polymer F is dispersed or dissolved in a polymerization solvent by solution polymerization, and use the obtained dispersion or solution as the liquid composition. In this case, the polymerization solvent corresponds to the first solvent. The dispersion or solution obtained by solution polymerization may further contain, in addition to polymer F and the polymerization solvent, components corresponding to the first solvent, such as the above-mentioned unreacted monomers and oligomers.

[0087] <Step 2> In step 2, the liquid composition obtained in step 1 is mixed with the second solvent described above to aggregate the polymer F.

[0088] The temperature of the liquid composition just before mixing with the second solvent is preferably 20 ° C. or higher, more preferably 23 ° C. or higher, and even more preferably 25 ° C. or higher, from the viewpoint that the dispersibility and solubility of the liquid composition are excellent, polymer clumping is suppressed in step 2, and particles containing polymer F of a moderate particle size can be produced. Also, from the viewpoint that the energy required to heat the liquid composition in step 1 can be saved, it is preferably 70 ° C. or lower, more preferably 60 ° C. or lower, and even more preferably 50 ° C. or lower. The temperature of the second solvent just before mixing with the liquid composition is preferably -15 ° C. or higher, more preferably -10 ° C. or higher, and even more preferably -5 ° C. or higher, from the viewpoint that the energy required to cool the second solvent can be saved in step 2. Also, polymer F is prone to aggregation, and excessive pulverization of the polymer in step 2 is suppressed. From this viewpoint, it is preferably 30 ° C. or lower, more preferably 28 ° C. or lower, and even more preferably 25 ° C. or lower.

[0089] It is preferable that the liquid composition and the second solvent are mixed together with stirring. Known stirring conditions can be used. For example, the optimum stirring rotation speed varies depending on the shape of the stirring blades, the scale of the treatment tank, etc., but is preferably 1 to 500 rpm. The stirring treatment may be carried out at normal pressure or under pressure in a pressure vessel. The stirring time is preferably 15 minutes to 16 hours, more preferably 30 minutes to 8 hours. The higher the temperature of the second solvent, the shorter the stirring time. There are no particular limitations on the stirring means, and known stirring devices can be used.

[0090] When the liquid composition and the second solvent are mixed in step 2, the mass ratio of the mass of the second solvent to the mass of the first solvent in the liquid composition (mass of the second solvent / mass of the first solvent in the liquid composition) is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more, from the viewpoint of better agglomeration of polymer F. The mass ratio (mass of the second solvent / mass of the first solvent in the liquid composition) is preferably 8.0 or less, more preferably 6.0 or less, and even more preferably 3.5 or less, from the viewpoint of facilitating adjustment of the particle size of the particles of polymer F to an appropriate range.

[0091] When the liquid composition and the second solvent are mixed in step 2, the second solvent may be added to the liquid composition all at once, or the second solvent may be added in multiple portions. When the second solvent is added in multiple portions, the second solvent added initially may be used to dilute the liquid composition. When the second solvent is added in multiple portions, the type of the second solvent in each addition may be the same or different.

[0092] <Other Steps> The process for producing a fluoropolymer of the present invention may have steps other than those described above (hereinafter also referred to as "other steps"). A specific example of the other steps is step 3, in which particles containing polymer F are separated and recovered from a liquid containing particles containing polymer F after step 2. Examples of the separation method in step 3 include known filtration methods such as pressure filtration, reduced pressure filtration, atmospheric pressure filtration and centrifugal filtration.

[0093] Step 3 may include a washing treatment in which the recovered particles containing polymer F are washed with a washing solvent (preferably the above-mentioned second solvent). The washing treatment may be carried out only once or multiple times.

[0094] Step 3 may include a drying treatment for drying the recovered particles containing polymer F. When a washing treatment is performed in step 3, the drying treatment is preferably performed after the washing treatment. Examples of the drying method include known drying methods such as hot air drying, vacuum drying, suction drying, infrared drying, and air (nitrogen) blow drying. The drying temperature in the drying treatment is preferably −15° C. or higher, more preferably −10° C. or higher, and preferably 80° C. or lower, more preferably 70° C. or lower. The drying time in the drying treatment is preferably 30 minutes or longer, more preferably 60 minutes or longer, and preferably 24 hours or shorter, more preferably 21 hours or shorter.

[0095] [Particles containing polymer F] In the particles containing polymer F obtained by the present production method, the content of polymer F is preferably 5% by mass or more, more preferably 15% by mass or more, and even more preferably 24% by mass or more, relative to the total mass of the particles containing polymer F, and is preferably 52% by mass or less, more preferably 46% by mass or less, and even more preferably 40% by mass or less.

[0096] The average particle size of the particles containing polymer F obtained by this production method is preferably 38 μm or more, more preferably 500 μm or more, and even more preferably 1000 μm or more, from the viewpoint of suppressing excessive micronization of the polymer particles in step 2 and improving filterability in step 3, and is preferably 10,000 μm or less, more preferably 5,000 μm or less, and even more preferably 2,000 μm or less, from the viewpoint of facilitating removal of components other than polymer F from the particles. The average particle size of the particles containing polymer F is a value calculated from the particle size distribution measured by mechanical sieving using a stainless steel testing sieve (JIS-Z8801).

[0097] The present invention will be described in detail below with reference to examples. Examples 1 to 4 are working examples, and Examples 5 and 6 are comparative examples. However, the present invention is not limited to these examples.

[0098] [Measurement of Mass Loss Rate] The particles containing polymer F obtained immediately after the washing treatment in each example were weighed to measure the mass W1. Next, the particles containing polymer F obtained immediately after the washing treatment in each example were air-dried at 50°C for 2 hours in a forced hot air circulation / ventilation oven (Espec Corp., small high-temperature chamber STH-120). After air-drying under heating, the mass W2(0.5) of the particles containing polymer F after 0.5 hours, the mass W2(1) of the particles containing polymer F after 1 hour, and the mass W2(2) of the particles containing polymer F after 2 hours were each weighed. Based on the measured masses W1 and W2, the mass loss rate of the particles containing polymer F for each elapsed time of air-drying under heating was calculated using the following formula (W). The results were expressed as an index where the mass loss rate of formula (W) calculated based on the mass of W2(0.5) in Example 5 was set to "100". The smaller the index value, the fewer impurities there were in the particles containing polymer F. The results are shown in Table 2 below. Formula (W) Mass reduction rate (%) = 100 × (W1 - W2) / W1 In the formula, W2 means W2(0.5), W2(1), or W2(2).

[0099] [Ion Exchange Capacity] The particles containing polymer F after air drying in each example were vacuum dried at 240° C. for 16 hours. The dried polymer F was weighed and placed in a polycarbonate container. The dried polymer F was then dissolved in a 0.7 N NaOH solution (solvent: H ２ O / CH ３ The polymer F was immersed in a solution of 100% ammonium hydroxide (OH) and 10% ammonium hydroxide (OH) at 60°C for 72 hours or more. ２ The F groups were completely converted to the Na salt form. The NaOH solution in which the dried polymer F had been immersed was back-titrated with 0.1 mol / L HCl using phenolphthalein as an indicator to determine the amount of NaOH in the solution, thereby calculating the ion exchange capacity (milliequivalents / g dry resin). The results are shown in Table 2 below. In the table, "meq / g" means "milliequivalents / g dry resin", which is the unit of ion exchange capacity. When three or more types of monomers are used, １９ The composition was determined by F-NMR, and the ion exchange capacity was calculated.

[0100] [TQ Value] The particles containing the polymer after air drying in each example were vacuum dried at 240°C for 16 hours. Using a flow tester (Shimadzu Corporation, CFT-500D) equipped with a nozzle having a length of 1 mm and an inner diameter of 1 mm, the particles containing the polymer after vacuum drying were melt-extruded while changing the temperature under the condition of an extrusion pressure of 2.94 MPa (gauge pressure). The extrusion amount of the polymer was 100 mm ３ The TQ value, which is the temperature at which the temperature becomes 0.05 / sec, was calculated. The results are shown in Table 2 below.

[0101] [Monomers] TFE: tetrafluoroethylene Monomer m1: CF ２ = CFOCF ２ CF (CF ３ ) O(CF ２ ) ２ SO ２ F. Monomer m2 Monomer m3: Perfluoro(2,2-dimethyl-1,3-dioxole)

[0102] [Radical polymerization initiator] V-601: Dimethyl 2,2'-azobis(2-methylpropionate) AIBN: 2,2'-azobis(isobutylnitrile) PFB: CF ３ CF ２ CF ２ C(=O)OOC(=O)CF ２ CF ２ CF ３

[0103] [Solvent] HCFO-1233yd(E) / (Z):CHF ２ A mixture of E and Z isomers of CF═CHCl (AMOLEA® AS-300 (manufactured by AGC), normal boiling point 54° C.) HFE-347pc-f: HCF ２ CF ２ OCH ２ CF ３ , Asahiklin AE-3000 (manufactured by AGC), normal boiling point 56°C, HFC-52-13p:CF ３ (CF ２ ) ４ CF ２ H, Asahiklin AC-2000 (AGC), normal boiling point 71.8°C

[0104] [Example 1] <Step 1> A 230 mL stainless steel reactor was charged with 186 g of monomer m1, and freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, heated to 55 ° C, nitrogen gas was introduced to 0.17 MPa, TFE was introduced, and the total pressure was set to 0.85 MPaG (gauge pressure, the same applies hereinafter). 3.82 g of an initiator solution in which V-601, a radical polymerization initiator, was dissolved in monomer m1 at a concentration of 1.43 mass% was pressure-charged into the reactor to initiate polymerization. TFE was continuously added while maintaining the initiation pressure. When the amount of TFE continuously introduced reached 15.4 g, the reactor was cooled to 10 ° C, and unreacted TFE was released into the air, resulting in a liquid composition 1, which was a solution in which polymer F1 was dissolved in unreacted monomer m1.

[0105] <Step 2> 100 g of liquid composition 1 was diluted with 61.0 g of HCFO-1233yd(E) / (Z). The diluted liquid composition was kept at 50°C, and this was added to 193 g of HCFO-1233yd(E) / (Z) at 25°C and stirred to aggregate polymer F1, forming particles containing polymer F1. After stirring, the liquid containing particles containing polymer F1 was filtered using filter paper. 202 g of HCFO-1233yd(E) / (Z) at 25°C was added to the separated and recovered particles containing polymer F1, and the mixture was stirred and then washed by filtration. This washing was repeated three times in total, yielding 42.6 g of particles containing polymer F1. The recovered particles containing polymer F1 were air-dried at 50°C for 2 hours in a hot air circulating oven, yielding 25.5 g of particles containing polymer F1. After air drying, the particles containing polymer F1 were used to measure the ion exchange capacity and TQ value according to the above-mentioned methods.

[0106] [Example 2] <Step 1> A 230 mL stainless steel reactor was charged with 162 g of monomer m1, and freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, heated to 60°C, and TFE was charged at that temperature until the pressure reached 1.30 MPaG. 0.86 g of an initiator solution prepared by dissolving the radical polymerization initiator AIBN in HCFO-1233yd(E) / (Z) at a concentration of 4.74 mass% was pressure-charged into the reactor to initiate polymerization. TFE was continuously added while maintaining the initiation pressure. When the amount of TFE continuously introduced reached 8.1 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, resulting in a liquid composition 2 in which polymer F2 was dissolved in unreacted monomer m1 and HCFO-1233yd(E) / (Z).

[0107] <Step 2> 167 g of Liquid Composition 2 was kept at 25°C, and this was added to 451 g of HCFO-1233yd(E) / (Z) at 25°C and stirred to aggregate the polymer F2, forming particles containing polymer F2. After stirring, the liquid containing particles containing polymer F2 was filtered using filter paper. 150 g of HCFO-1233yd(E) / (Z) at 25°C was added to the separated and recovered particles containing polymer F2, and the mixture was stirred and then washed by filtration. This washing was repeated three times in total, yielding 26.6 g of particles containing polymer F2. The recovered particles containing polymer F2 were air-dried in a hot air circulation oven at 50°C for 2 hours, yielding 17.4 g of particles containing polymer F2. The ion exchange capacity and TQ value of the air-dried particles containing polymer F2 were measured according to the methods described above.

[0108] [Example 3] <Step 1> A 230 mL stainless steel reactor was charged with 162 g of monomer m1, and freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, the temperature was raised to 50°C, and TFE was charged at that temperature until the pressure reached 1.25 MPaG. 1.25 g of an initiator solution prepared by dissolving the radical polymerization initiator V-601 in HCFO-1233yd(E) / (Z) at a concentration of 3.34 mass% was pressure-charged into the reactor to initiate polymerization. TFE was continuously added while maintaining the initiation pressure. When the amount of TFE continuously introduced reached 7.1 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, resulting in a liquid composition 3, which was a solution of polymer F3 dissolved in unreacted monomer m1 and HCFO-1233yd(E) / (Z).

[0109] <Step 2> 163 g of Liquid Composition 3 was kept at 25°C, and this was added to 525 g of HCFO-1233yd(E) / (Z) at 25°C and stirred to aggregate Polymer F3, forming particles containing Polymer F3. After stirring, the liquid containing particles containing Polymer F3 was filtered using filter paper. 150 g of HCFO-1233yd(E) / (Z) at 25°C was added to the separated and recovered particles containing Polymer F3, and the mixture was stirred and then washed by filtration. This washing was repeated three times in total, yielding 18.8 g of particles containing Polymer F3. The recovered particles containing Polymer F3 were air-dried at 50°C for 2 hours in a hot air circulation oven, yielding 13.8 g of particles containing Polymer F3. The ion exchange capacity and TQ value of the air-dried particles containing Polymer F3 were measured according to the methods described above.

[0110] [Example 4] <Step 1> A 230 mL stainless steel reactor was charged with 108 g of monomer m2, 29.0 g of monomer m3, and 1.22 g of AC-2000, and 1.05 g of a solution of AC-2000 dissolved so that the concentration of PFB, a radical polymerization initiator, was 3.0% by mass was added, and after charging, freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, 4.15 g of TFE was charged, stirred at 100 rpm, and heated to 24 ° C. to initiate polymerization. The internal temperature was maintained at 24 ° C., and the reaction was continued for 8 hours, after which it was cooled and unreacted TFE was released into the air. Thereafter, the remaining monomer m3 was distilled off at 24 ° C. under reduced pressure for 3 hours, and a liquid composition 4 was obtained, which was a solution in which polymer F4 was dissolved in unreacted monomer m2 and AC-2000.

[0111] <Step 2> 53.5 g of liquid composition 4 was diluted with 93.6 g of HCFO-1233yd(E) / (Z). The diluted liquid composition was kept at 25°C, and this was added to 208 g of HCFO-1233yd(E) / (Z) at -6.3°C and stirred to aggregate polymer F4, forming particles containing polymer F4. After stirring, the liquid containing particles containing polymer F4 was filtered using filter paper. 165 g of HCFO-1233yd(E) / (Z) at 25°C was added to the separated and recovered particles containing polymer F4, and the mixture was stirred and then washed by filtration. This washing was repeated three times in total, yielding 26.3 g of particles containing polymer F4. The recovered particles containing polymer F4 were air-dried at 50°C for 2 hours in a hot air circulating oven, yielding 13.3 g of particles containing polymer F4. After air drying, the particles containing polymer F4 were used to measure the ion exchange capacity and TQ value according to the above-mentioned methods.

[0112] [Example 5] <Step 1> A 230 mL stainless steel reactor was charged with 189 g of monomer m1, and freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, the temperature was raised to 55 ° C, nitrogen gas was introduced at 0.17 MPa, TFE was introduced, and the total pressure was set to 0.85 MPaG. 3.82 g of an initiator solution in which V-601, a radical polymerization initiator, was dissolved in HFC-52-13p at a concentration of 1.43 mass% was pressure-charged into the reactor to initiate polymerization. TFE was continuously added while maintaining the initiation pressure. When the amount of TFE continuously introduced reached 15.4 g, the reactor was cooled to 10 ° C, and unreacted TFE was released into the air, resulting in a liquid composition 5 in which polymer F5 was dissolved in unreacted monomer m1 and HFC-52-13p.

[0113] <Step 2> 100 g of Liquid Composition 5 was diluted with 60.4 g of HFC-52-13p. The diluted liquid composition was kept at 25°C and added to 466 g of HFE-347pc-f at -30°C and stirred to aggregate Polymer F5, forming particles containing Polymer F5. After stirring, the liquid containing particles containing Polymer F5 was filtered using filter paper. 201 g of HFE-347pc-f at 25°C was added to the separated and recovered polymer particles, followed by stirring and filtration for washing. This washing was repeated three times in total, yielding 63.9 g of particles containing Polymer F5. The recovered particles containing Polymer F5 were air-dried in a hot air circulating oven at 50°C for 2 hours, yielding 26.1 g of particles containing Polymer F5. The ion exchange capacity and TQ of the air-dried particles containing Polymer F5 were measured according to the methods described above.

[0114] [Example 6] <Step 1> A 230 mL stainless steel reactor was charged with 189 g of monomer m1, and freeze-degassing was thoroughly carried out using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, heated to 55 ° C, nitrogen gas was introduced to 0.14 MPa, TFE was introduced, and the total pressure was set to 0.82 MPaG. 3.87 g of an initiator solution in which V-601, a radical polymerization initiator, was dissolved in HFE-347pc-f at a concentration of 1.41 mass% was pressure-charged into the reactor to initiate polymerization. TFE was continuously added while maintaining the initiation pressure. When the amount of TFE continuously introduced reached 15.4 g, the reactor was cooled to 10 ° C, and unreacted TFE was released into the air, resulting in a liquid composition 6 in which polymer F6 was dissolved in unreacted monomer m1 and HFE-347pc-f.

[0115] <Step 2> 101 g of Liquid Composition 6 was diluted with 62.5 g of HFE-347pc-f. The diluted liquid composition was kept at 50°C and added to 194 g of HFE-347pc-f at 25°C, followed by stirring to aggregate Polymer F6 and form particles containing Polymer F6. After stirring, the liquid containing particles containing Polymer F6 was filtered using filter paper. 199 g of HFE-347pc-f at 25°C was added to the separated and recovered polymer particles, followed by stirring and filtration for washing. This washing was repeated three times in total, yielding 56.0 g of particles containing Polymer F6. The recovered particles containing Polymer F6 were air-dried in a hot air circulating oven at 50°C for 2 hours, yielding 26.1 g of particles containing Polymer F6. The ion exchange capacity and TQ of the air-dried particles containing Polymer F6 were measured according to the methods described above.

[0116] Table 1 below summarizes the conditions in step 1 for each example, and Table 2 below summarizes the conditions, physical properties, and evaluation results in step 2 for each example.

[0117]

[0118]

[0119] As shown in Table 2, it was confirmed that the method for producing particles containing a fluoropolymer of the present invention makes it possible to produce particles containing a fluoropolymer with a low content of impurities (Examples 1 to 4).

[0120] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-143764, filed on September 5, 2023, are incorporated herein by reference as part of the disclosure of the present invention.

Claims

1. A method for producing particles containing a fluoropolymer having a group that can be converted into an ion exchange group, comprising: preparing a liquid composition containing the fluoropolymer and a first solvent; and then mixing the liquid composition with a second solvent which is an olefin having fluorine atoms and chlorine atoms to aggregate the fluoropolymer and form particles containing the fluoropolymer.

2. The method for producing particles containing a fluoropolymer according to claim 1, wherein the olefin has 3 carbon atoms.

3. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the normal boiling point of the olefin is from 14 to 89°C.

4. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the fluoropolymer contains a unit based on tetrafluoroethylene and a unit based on a compound represented by formula (1). ２ = CF-L-(A) ｎ In formula (1), L is an (n+1) valent perfluorohydrocarbon group which may contain an etheric oxygen atom, A is a group which can be converted into a sulfonic acid type functional group, and n is 1 or 2.

5. The method for producing particles containing a fluoropolymer according to claim 4, wherein the first solvent contains at least one selected from the group consisting of a compound represented by formula (1) and an organic solvent.

6. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the mass ratio of the content of the fluoropolymer to the content of the first solvent in the liquid composition is 0.050 to 0.

43.

7. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein when the liquid composition and the second solvent are mixed, the mass ratio of the mass of the second solvent to the mass of the first solvent in the liquid composition is 1.0 to 8.

0.

8. A method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the content of the first solvent is 70% by mass or more and 95% by mass or less based on the total mass of the liquid composition.

9. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the average particle size of the particles is 38 μm or more and 10,000 μm or less.

10. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the mixing is carried out using the liquid composition having a temperature of 20°C or more and 60°C or less, and the second solvent having a temperature of -15°C or more and 30°C or less.

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