Method for producing particles containing fluorine-containing polymer

Abstract

The present invention provides a method for producing particles containing a fluorine-containing polymer, with which it is possible to produce particles containing a fluorine-containing polymer and having a low impurity content.　In a method for producing particles containing a fluorine-containing polymer according to the present invention, a monomer containing tetrafluoroethylene and a compound having a group that can be converted to a sulfonic acid-type functional group is polymerized in the presence of a first hydrofluoroether to obtain a liquid composition that contains a fluorine-containing polymer and the first hydrofluoroether, and subsequently, the liquid composition and a second hydrofluoroether are mixed so as to aggregate the fluorine-containing polymer, thereby 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 a sulfonic acid functional 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 impurity content.

[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 is obtained by polymerizing a monomer containing tetrafluoroethylene and a compound having a group that can be converted into a sulfonic acid type functional group in the presence of a first hydrofluoroether, and then the liquid composition is mixed with a second hydrofluoroether to coagulate the fluoropolymer, the content of impurities in the resulting particles containing the fluoropolymer is reduced, leading to the present invention.

[0007] That is, the inventors have found that the above problems can be solved by the following configuration. [1] A method for producing particles containing a fluoropolymer, comprising polymerizing a monomer containing tetrafluoroethylene and a compound having a group that can be converted into a sulfonic acid functional group in the presence of a first hydrofluoroether to obtain a liquid composition containing a fluoropolymer and the first hydrofluoroether, and then mixing the liquid composition with a second hydrofluoroether to aggregate the fluoropolymer and form particles containing the fluoropolymer. [2] A method for producing particles containing a fluoropolymer according to [1], wherein the first hydrofluoroether and the second hydrofluoroether both have 5 or less carbon atoms. [3] A method for producing particles containing a fluoropolymer according to [1] or [2], wherein the first hydrofluoroether and the second hydrofluoroether are both compounds represented by the following formula (S1): Formula (S1) R １ -O-R ２ In formula (S1), R １ and R ２ are each independently a fluoroalkyl group having 2 or less carbon atoms. １ and R ２wherein when one group has no hydrogen atom, the other group has a hydrogen atom. [4] A method for producing particles comprising a fluoropolymer according to any of [1] to [3], wherein the first hydrofluoroether and the second hydrofluoroether are the same type of compound. [5] A method for producing particles comprising a fluoropolymer according to any of [1] to [4], wherein a washing treatment is carried out to wash the fluoropolymer particles with a third hydrofluoroether. [6] A method for producing particles comprising a fluoropolymer according to [5], wherein the third hydrofluoroether is the same type of compound as at least one of the first hydrofluoroether and the second hydrofluoroether. [7] A method for producing particles comprising a fluoropolymer according to any of [1] to [7], wherein the compound having a group that can be converted into a sulfonic acid type functional group is 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 into a sulfonic acid functional group, and n is 1 or 2. [8] A method for producing particles containing a fluoropolymer according to any of [1] to [7], wherein the mass ratio of the content of the fluoropolymer to the content of the first hydrofluoroether in the liquid composition is 0.10 or more. [9] A method for producing particles containing a fluoropolymer according to any of [1] to [8], wherein, when mixing the liquid composition with the second hydrofluoroether, the mass ratio of the mass of the fluoropolymer in the liquid composition to the total mass of the first hydrofluoroether and the second hydrofluoroether in the liquid composition is 0.20 or less.

[10] A method for producing particles comprising a fluoropolymer according to any one of [1] to [9], wherein the fluoropolymer is a copolymer containing units based on tetrafluoroethylene and units based on a compound represented by the following formula (1), or a copolymer containing units based on tetrafluoroethylene, units based on a monomer having a cyclic ether structure, and units based on a fluoromonomer having a group that can be converted into a sulfonic acid functional group: Formula (1): CF ２ =CF-L-(A) ｎ

[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 involves polymerizing a monomer containing tetrafluoroethylene (hereinafter also referred to as "TFE") and a compound having a group that can be converted into a sulfonic acid functional group in the presence of a first hydrofluoroether (hereinafter also referred to as "HFE-1") to obtain a liquid composition containing a fluoropolymer (hereinafter also referred to as "polymer F"), and then mixing the liquid composition with a second hydrofluoroether (hereinafter also referred to as "HFE-2") 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 made clear, but it is thought that the use of HFE-2 to aggregate polymer F prevents components other than polymer F (e.g., monomers used in the production of polymer F, oligomers produced in the production of polymer F, various solvents, etc.) from being incorporated into the particles. Furthermore, it is believed that by using HFE-2 to aggregate polymer F, components other than polymer F in the particles are more easily removed when the aggregated polymer F is subjected to treatments such as washing and drying. Furthermore, by using HFE-1 to produce polymer F, hydrofluoroether is consistently used as the solvent used in the production of polymer F. HFE-1 is incorporated into part of HFE-2 during aggregation, and for the same reason as when HFE-2 is used for aggregation, it is believed that as a result, components other than polymer F in the particles are more easily removed. It is believed that this has made it possible to obtain a fluorine-containing polymer with a low impurity content.

[0013] [Liquid Composition] The liquid composition contains polymer F and HFE-1, and may further contain a solvent other than HFE-1 (hereinafter also referred to as "other solvent 1"). In this specification, HFE-1 contained in the liquid composition and other solvent 1 that may be contained in the liquid composition may be collectively referred to as "first solvent". The first solvent contains HFE-1 and may further contain other solvent 1. Note that when the liquid composition does not contain other solvent 1, the first solvent refers to HFE-1.

[0014] The liquid composition may be a solution in which polymer F is dissolved in a 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 a first solvent, or a dispersion in which polymer F is dispersed in a 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 as the value measured using 90° scattered light at room temperature (measurement wavelength: 850 nm) using a portable turbidimeter TN-100 manufactured by EUTECH INSTRUMENTS. The sample to be measured is 10 mL of sample 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).

[0015] <Polymer F> Polymer F is produced by the method described in the below-described step 1. Polymer F is not particularly limited as long as it is a polymer containing units based on TFE and units based on a compound having a group that can be converted into a sulfonic acid functional group, but polymer F-1 or polymer F-2 shown below are preferred in terms of achieving better effects of the present invention.

[0016] (Polymer F-1) Polymer F-1 is a copolymer containing units based on TFE and units based on a fluorine-containing monomer having a group that can be converted into a sulfonic acid functional group, and is preferably a copolymer containing units based on TFE and units based on a compound represented by formula (1) described below. Polymer F-1 preferably does not have a cyclic ether structure.

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

[0018] Examples of the fluorine-containing monomer having a group that can be converted into a sulfonic acid functional group include compounds that have one or more fluorine atoms in the molecule, have an ethylenic double bond, and have 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 a sulfonic acid functional 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. When there are a plurality of As, each As may be the same or different.

[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 ｆ１ is 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 (CF ３ )-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 a sulfonic acid functional group may be used alone or in combination of two or more.

[0044] The content of units based on a fluorine-containing monomer having a group convertible to a sulfonic acid functional 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 copolymer having units based on TFE, units based on a monomer having a cyclic ether structure, and units based on a fluorine-containing monomer having a group that can be converted into a sulfonic acid functional 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 ２It 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 two or more. The perfluoroalkylene group may be linear or branched, but is preferably linear. R ２２ is 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-bonded 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 ４６ are 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 is preferably a fluorine atom from the viewpoint 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 that can be converted into a sulfonic acid functional group are the same as those of the fluorine-containing monomer having a group that can be converted into a sulfonic acid functional group in Polymer F-1. The content of units based on the fluorine-containing monomer having a group that can be converted into a sulfonic acid functional 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] The content of units based on TFE is preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, based on the total 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 sulfonic acid functional groups are converted into sulfonic acid functional groups by known treatments such as hydrolysis treatment and acidification treatment, a fluoropolymer having sulfonic acid functional 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 is determined by the method described in the Examples section below.

[0065] <First Solvent> The first solvent is a solvent (good solvent) that dissolves or disperses the polymer F, and contains HFE-1 and may further contain another solvent 1.

[0066] 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 0.10 or more, more preferably 0.15 or more, and even more preferably 0.18 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 0.33 or less, and even more preferably 0.25 or less.

[0067] 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

[0068] (First Hydrofluoroether (HFE-1)) HFE-1 is a solvent used as a polymerization solvent in Step 1 described below, and also functions as a solvent (good solvent) that dissolves or disperses Polymer F.

[0069] The number of carbon atoms in HFE-1 is preferably 8 or less, more preferably 5 or less, and even more preferably 4 or less, from the viewpoints of easy solvent recovery and excellent solvent recycling, and of good performance of drying of the polymer after coagulation and separation. The number of carbon atoms in HFE-1 is preferably 1 or more, and more preferably 2 or more, from the viewpoints of easy solvent recovery and excellent solvent recycling, and of excellent handleability at room temperature.

[0070] Specific examples of HFE-1 include 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 One type of HFE-1 may be used alone, or two or more types may be used in combination.

[0071] In terms of achieving better effects of the present invention, HFE-1 is preferably a compound represented by formula (S1): １ -O-R ２ In formula (S1), R １ and R ２ are each independently a fluoroalkyl group having 2 or less carbon atoms. １ and R ２ When one of the groups does not have a hydrogen atom (i.e., when one of the groups is a perfluoroalkyl group), the other group has a hydrogen atom. １ and R ２ The number of carbon atoms in the fluoroalkyl group in R is 2 or less, preferably 1 to 2, and more preferably 2. １ and R ２ Each of the fluoroalkyl groups preferably contains a hydrogen atom.

[0072] The content of HFE-1 is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more, relative to the total mass of the liquid composition, from the viewpoint of achieving better solubility or dispersibility of polymer F; and is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, from the viewpoint of suppressing excessive particle size reduction of the polymer in step 2, improving filterability in step 3, and saving the amount of solvent used during aggregation. The mass ratio of the content of polymer F to the content of HFE-1 in the liquid composition (content of polymer F / content of HFE-1) is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.40 or more, from the viewpoints of suppressing excessive pulverization of the polymer in step 2, improving filterability in step 3, and saving the amount of solvent used during aggregation, and is preferably 20 or less, more preferably 15 or less, and even more preferably 0.70 or less, from the viewpoint of more excellent solubility or dispersibility of polymer F. The content of HFE-1 in the liquid composition is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, based on the total mass of the first solvent.

[0073] (Other Solvent 1) Specific examples of the other solvent 1 include organic solvents (excluding hydrofluoroethers), unreacted monomers used in the production of polymer F, and oligomers produced during the production of polymer F. The other solvent 1 may be used alone or in combination of two or more. Among these, the unreacted monomers used in the production of polymer F are preferred in terms of availability, cost, boiling point, separation and recovery, etc.

[0074] The organic solvent is preferably a fluorine-based solvent (excluding hydrofluoroethers) or a hydrocarbon-based solvent, because they have excellent solubility or dispersibility for the polymer F. 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 (CF２ ) 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 ２ CHFCl (1,3-dichloro-1,1,2,2,3-pentafluoropropane), CF ３ CF ２ CHCl ２ , C.H. ３ CCl ２ Hydrochlorofluorocarbons such as F; 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 ２ C(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; CF３ CF=CCl ２ , C.F. ３ CCl = CCl ２ Chlorofluoroolefins such as:

[0075] 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.

[0076] 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 produced during the production of polymer F is an oligomer produced by polymerizing TFE and the compound represented by formula (1) above, and the molecular weight thereof is usually several tens of thousands or less.

[0077] The first solvent contains HFE-1, and preferably further contains an unreacted monomer (preferably a compound represented by formula (1)) used in the production of polymer F, in order to obtain better dispersibility or solubility of polymer F.

[0078] When the liquid composition contains another solvent 1, the content of the other solvent 1 is preferably 50% by mass or more, more preferably 60% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, relative to the total mass of the first solvent.

[0079] [Second Solvent] HFE-2 used in step 2 is a solvent (poor solvent) used to aggregate polymer F in a liquid medium to form particles of polymer F. Here, in step 2, a solvent other than HFE-2 (hereinafter also referred to as "another solvent 2") may be used together with HFE-2. In this specification, HFE-2 used in step 2 and other solvent 2 that can be used in step 2 may be collectively referred to as the "second solvent". The second solvent includes HFE-2 and may further include other solvent 2. Note that when no other solvent is used in step 2, the second solvent refers to HFE-2.

[0080] <Second Hydrofluoroether (HFE-2)> The number of carbon atoms in HFE-2 is preferably 8 or less, more preferably 5 or less, and even more preferably 4 or less, from the viewpoints of easy solvent recovery and excellent solvent recycling, and of satisfactory drying of the polymer after coagulation and separation. The number of carbon atoms in HFE-2 is preferably 1 or more, and preferably 2 or more, from the viewpoints of easy solvent recovery and excellent solvent recycling, and of excellent handleability at room temperature.

[0081] Specific examples of HFE-2 include 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 (CF３ )CF ２ OCH ３ , n-C ３ F ７ OCF (CF ３ )CF ２ OCHFCF ３ One type of HFE-2 may be used alone, or two or more types may be used in combination.

[0082] HFE-2 is preferably a compound represented by the above formula (S1) in terms of achieving better effects of the present invention.

[0083] It is preferable that HFE-1 and HFE-2 are the same type of compound, since this will provide better effects of the present invention.

[0084] The content of HFE-2 is preferably 80% by mass or more, more preferably 85% by mass or more, and is preferably 100% by mass or less, based on the total mass of the second solvent.

[0085] <Other Solvent 2> Specific examples of the other solvent 2 include organic solvents (excluding hydrofluoroethers). Examples of organic solvents include fluorine-based solvents (excluding hydrofluoroethers) and hydrocarbon-based solvents. Specific examples of the fluorine-based solvents and hydrocarbon-based solvents in the other solvent 2 are the same as the specific examples of the fluorine-based solvents and hydrocarbon-based solvents in the other solvent 1 described above. Of these, the other solvent 2 is preferably a hydrocarbon-based solvent, and more preferably methanol.

[0086] When the second solvent contains another solvent 2, the content of the other solvent 2 is preferably more than 0 mass % relative to the total mass of the second solvent, and is preferably 20 mass % or less, and more preferably 15 mass % or less.

[0087] [Steps] In this specification, the step of polymerizing a monomer containing TFE and a compound having a group that can be converted into a sulfonic acid functional group in the presence of HFE-1 to obtain a liquid composition containing polymer F and the HFE-1 is also referred to as "step 1." Furthermore, the step of mixing the liquid composition with HFE-2 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.

[0088] <Step 1> Step 1 is a step of polymerizing a monomer containing TFE and a compound having a group that can be converted into a sulfonic acid functional group in the presence of HFE-1 to obtain a liquid composition containing Polymer F and the above-mentioned HFE-1.

[0089] An example of a method for producing Polymer F is a method in which the above-mentioned monomers are copolymerized in a reactor in the presence of HFE-1 and a polymerization initiator.

[0090] 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.

[0091] 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 HFE-1 (or the first solvent) contained in the liquid composition.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] In step 1, a dispersion or solution in which polymer F is dispersed or dissolved in HFE-1 is obtained. The dispersion or solution thus obtained is preferably used as the liquid composition to be subjected to step 2. Here, the dispersion or solution obtained in step 1 may further contain, in addition to polymer F and HFE-1, components corresponding to the first solvent, such as the above-mentioned unreacted monomers and oligomers.

[0096] <Step 2> In step 2, the liquid composition obtained in step 1 is mixed with the above-mentioned HFE-2 to aggregate the polymer F. In step 2, the above-mentioned second solvent containing HFE-2 may be used.

[0097] The temperature of the liquid composition immediately before mixing with HFE-2 (or 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, agglomeration of the polymer is suppressed in step 2, and particles containing polymer F of an appropriate particle size can be produced. Also, from the viewpoint that the energy required for heating 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 HFE-2 (or the second solvent) immediately 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 for cooling HFE-2 (or the second solvent) can be saved in step 2. Also, from the viewpoint that polymer F is prone to aggregation and excessive pulverization of the polymer in step 2 is suppressed, it is preferably 30 ° C. or lower, more preferably 28 ° C. or lower, and even more preferably 25 ° C. or lower.

[0098] It is preferable that mixing of the liquid composition with HFE-2 (or the second solvent) be accompanied by stirring. Known conditions can be used as stirring conditions. 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 stirring time becomes shorter when the temperature of the second solvent is high. There are no particular limitations on the stirring means, and known stirring devices can be used.

[0099] When the liquid composition and HFE-2 are mixed in step 2, the mass ratio of the mass of polymer F in the liquid composition to the total mass of HFE-1 and HFE-2 in the liquid composition [mass of polymer F in the liquid composition / (mass of HFE-1 in the liquid composition + mass of HFE-2 used in step 2)] is preferably 0.034 or more, more preferably 0.037 or more, and even more preferably 0.09 or more, from the viewpoint that it becomes easy to adjust the particle size of the particles of polymer F to an appropriate range and the amount of solvent used during aggregation can be saved. The mass ratio [mass of fluoropolymer in the liquid composition / (mass of HFE-1 in the liquid composition + mass of HFE-2 used in step 2)] is preferably 0.20 or less, more preferably 0.18 or less, and even more preferably 0.15 or less, from the viewpoint that polymer F can be aggregated more satisfactorily.

[0100] When the liquid composition and HFE-2 are mixed in step 2, the mass ratio of the mass of HFE-2 to the mass of HFE-1 in the liquid composition (mass of HFE-2 used in step 2 / mass of HFE-1 in the liquid composition) is preferably 1.0 or more, more preferably 2.0 or more, and even more preferably 3.0 or more, from the viewpoint of enabling better aggregation of polymer F. The mass ratio (mass of HFE-2 used in step 2 / mass of HFE-1 in the liquid composition) is preferably 500 or less, more preferably 400 or less, and even more preferably 380 or less, from the viewpoint of facilitating adjustment of the particle size of the particles of polymer F to an appropriate range.

[0101] In step 2, when a liquid composition containing the first solvent is mixed with a second solvent, 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 used in step 2 / mass of the first solvent in the liquid composition) is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.2 or more, from the viewpoint of better agglomeration of polymer F. The mass ratio (mass of the second solvent used in step 2 / mass of the first solvent in the liquid composition) is preferably 15 or less, more preferably 10 or less, and even more preferably 9.7 or less, from the viewpoint of facilitating adjustment of the particle size of the particles of polymer F to an appropriate range.

[0102] When the liquid composition and HFE-2 (or the second solvent) are mixed in step 2, HFE-2 (or the second solvent) may be added to the liquid composition all at once, or HFE-2 (or the second solvent) may be added in multiple portions. When HFE-2 (or the second solvent) is added in multiple portions, the HFE-2 (or the second solvent) added initially may be used to dilute the liquid composition. When HFE-2 (or the second solvent) is added in multiple portions, the type of HFE-2 (or the second solvent) in each addition may be the same or different.

[0103] <Other Steps> The method 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. In step 3, before separating the particles containing polymer F, a solvent may be added to the liquid containing particles containing polymer F obtained in step 2. Specific examples of the solvent to be added include the various solvents shown above for the second solvent.

[0104] Step 3 may include a washing treatment in which the recovered particles containing polymer F are washed with a washing solvent (preferably a tertiary hydrofluoroether). The washing treatment may be carried out only once or multiple times.

[0105] Specific examples and preferred embodiments of the tertiary hydrofluoroether (hereinafter also referred to as "HFE-3") are the same as those for HFE-1 described above. In view of the superior effects of the present invention, HFE-3 is preferably the same type of compound as at least one of HFE-1 and HFE-2. In particular, in view of the superior effects of the present invention, it is preferred that HFE-1, HFE-2, and HFE-3 are all the same type of compound.

[0106] 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, and two or more of these drying methods may be combined. The drying temperature in the drying treatment is preferably −15° C. or higher, more preferably −10° C. or higher, and preferably 220° C. or lower, more preferably 80° C. or lower, and even 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.

[0107] [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.

[0108] 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 1,000 μm or more, from the viewpoints 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).

[0109] 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.

[0110] [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 and ventilation oven (Espec Corp., small high-temperature chamber STH-120) (drying under heat). After air-drying under heat, the mass W2 (2) of the particles containing polymer F was weighed. Next, the particles containing polymer F obtained after air-drying in Examples 1 to 3 and 5 were vacuum-dried at 80 ° C. for 16 hours, and the particles containing polymer F obtained after air-drying in Examples 4 and 6 were vacuum-dried at 210 ° C. for 16 hours in a rectangular vacuum constant temperature dryer (Yamato Scientific Co., Ltd., DP33) (drying under reduced pressure). After drying under reduced pressure, the mass W2 (16) of the particles containing polymer F was weighed. Based on the measured masses W1 and W2, the mass loss rate of the particles containing polymer F upon air drying under heating and upon heat drying under reduced pressure were 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(2) 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 loss rate (%) = 100 × (W1 - W2) / W1 In the formula, W2 means W2(2) or W2(16).

[0111] [Ion Exchange Capacity] After the vacuum drying, the particles containing polymer F were weighed and placed in a polycarbonate container. The particles containing polymer F after the vacuum drying were dissolved in a 0.7 N NaOH solution (solvent: H ２ O / CH ３ The polymer F was immersed in a 1000-kJ / 2000kJ aqueous solution of 1000kJ / 2000kcal (weight ratio) at 60°C for 72 hours or more. ２The F groups were completely converted to the Na salt form. The NaOH solution in which the particles containing polymer F after vacuum drying 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 (milli-equivalents / g dry resin). The results are shown in Table 2 below. In the table, "meq / g" means "milli-equivalents / 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.

[0112] [TQ value] 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, particles containing polymer F after vacuum drying were melt-extruded while changing the temperature under the condition of an extrusion pressure of 2.94 MPa (gauge pressure). 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.

[0113] [Monomers] TFE: tetrafluoroethylene Monomer m1: CF ２ = CFOCF ２ CF (CF ３ ) O(CF ２ ) ２ SO ２ F Monomer m2: Compound represented by the following formula (m2) Monomer m3: Perfluoro(2,2-dimethyl-1,3-dioxole)

[0114]

[0115] [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

[0116] [Solvent] ・HFE-347pc-f: HCF ２ CF２ 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

[0117] [Example 1] <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 55°C, and nitrogen gas was introduced at 0.15 MPa. TFE was then introduced, and the total pressure was adjusted to 0.82 MPaG (gauge pressure, the same applies hereinafter). 2.93 g of an initiator solution prepared by dissolving the radical polymerization initiator V-601 in HFE-347pc-f (AE-3000) at a concentration of 1.59 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 13.2 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, thereby obtaining a liquid composition 1, which was a solution in which polymer F1 was dissolved in unreacted monomer m1 and HFE-347pc-f (AE-3000).

[0118] <Step 2> 100 g of Liquid Composition 1 was diluted with 114 g of HFE-347pc-f (AE-3000). The diluted liquid composition was kept at 50°C and added to 180 g of HFE-347pc-f (AE-3000) at 25°C, followed by stirring to aggregate Polymer F1 and form particles containing Polymer F1.

[0119] <Step 3> After stirring, the liquid containing particles containing polymer F1 was filtered using filter paper. 200 g of HFE-347pc-f (AE-3000) 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 a total of three times to obtain particles containing polymer F1. 33.1 g of the recovered particles containing polymer F1 were air-dried in a hot air circulation oven at 50°C for 2 hours to obtain 20.0 g of particles containing polymer F1. The particles containing polymer F after air-drying were vacuum-dried at 80°C for 16 hours to obtain 19.7 g of particles containing polymer F7. The ion exchange capacity and TQ value of the particles containing polymer F1 after vacuum-drying were measured according to the methods described above.

[0120] [Example 2] <Step 1> A 230 mL stainless steel reactor was charged with 121 g of monomer m1 and 30.7 g of HFE-347pc-f (AE-3000), and freeze-degassing was thoroughly performed using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, heated to 70°C, and TFE was introduced to adjust the total pressure to 1.16 MPaG. 3.03 g of an initiator solution prepared by dissolving the radical polymerization initiator AIBN in HFE-347pc-f (AE-3000) at a concentration of 1.03 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 12.0 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, thereby obtaining a liquid composition 2 which was a solution in which polymer F2 was dissolved in unreacted monomer m1 and HFE-347pc-f (AE-3000).

[0121] <Step 2> 150 g of Liquid Composition 2 was kept at 25° C., and this was added to 202 g of HFE-347pc-f (AE-3000) at 25° C. and stirred to aggregate Polymer F2 and form particles containing Polymer F2.

[0122] <Step 3> After stirring, the liquid containing particles containing polymer F2 was filtered using filter paper. 200 g of HFE-347pc-f (AE-3000) 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 a total of three times to obtain particles containing polymer F2. 27.4 g of the recovered particles containing polymer F2 were air-dried in a hot air circulation oven at 50°C for 2 hours to obtain 19.8 g of particles containing polymer F2. The particles containing polymer F after air drying were vacuum-dried at 80°C for 16 hours to obtain 19.7 g of particles containing polymer F7. The ion exchange capacity and TQ value of the particles containing polymer F2 after vacuum drying were measured according to the methods described above.

[0123] [Example 3] <Step 1> A 230 mL stainless steel reactor was charged with 100 g of monomer m1 and 53.4 g of HFE-347pc-f (AE-3000), and freeze-degassing was thoroughly performed using liquid nitrogen. Thereafter, the mixture was stirred at 300 rpm, heated to 70°C, and TFE was introduced to adjust the total pressure to 1.12 MPaG. 3.06 g of an initiator solution prepared by dissolving the radical polymerization initiator AIBN in HFE-347pc-f (AE-3000) at a concentration of 2.05% by 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 11.0 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, thereby obtaining a liquid composition 3 which was a solution in which polymer F3 was dissolved in unreacted monomer m1 and HFE-347pc-f (AE-3000).

[0124] <Step 2> 103 g of Liquid Composition 3 was kept at 50° C., and this was added to 109 g of HFE-347pc-f (AE-3000) at −30° C. and stirred to aggregate Polymer F3 and form particles containing Polymer F3.

[0125] <Step 3> After stirring, the liquid containing particles containing polymer F3 was filtered using filter paper. 200 g of HFE-347pc-f (AE-3000) 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 a total of three times to obtain particles containing polymer F3. 24.6 g of the recovered particles containing polymer F3 were air-dried in a hot air circulation oven at 50°C for 2 hours to obtain 20.1 g of particles containing polymer F3. The particles containing polymer F after air drying were vacuum-dried at 80°C for 16 hours to obtain 19.8 g of particles containing polymer F3. The ion exchange capacity and TQ value of the particles containing polymer F3 after vacuum drying were measured according to the methods described above.

[0126] [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 HFE-347pc-f (AE-3000), and 1.05 g of a solution of HFE-347pc-f (AE-3000) dissolved so that the concentration of PFB, a radical polymerization initiator, was 3.00 mass% was added, and after charging, freezing and degassing were 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 the mixture 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 to obtain a liquid composition 4 in which polymer F4 was dissolved in unreacted monomer m2 and HFE-347pc-f (AE-3000).

[0127] <Step 2> 56.0 g of Liquid Composition 4 was diluted with 127 g of HFE-347pc-f (AE-3000). The diluted liquid composition was kept at 25°C, and this was mixed with 233 g of HFE-347pc-f (AE-3000) at 25°C and CH ３ The polymer F4 was added to 40.3 g of the mixed solvent of OH and stirred to aggregate the polymer F4, thereby forming particles containing the polymer F4.

[0128] <Step 3> After stirring, 204 g of the supernatant was removed, and then 106 g of HFE-347pc-f (AE-3000) at 25°C and CH ３After adding 45.6 g of a mixed solvent of OH and further stirring, the liquid containing particles containing polymer F4 was filtered using filter paper. The separated and recovered particles containing polymer F4 were mixed with 140 g of HFE-347pc-f (AE-3000) at 25°C and CH ３ 60.0 g of a mixed solvent of OH was added, stirred, and then filtered to wash. Washing was repeated a total of three times to obtain 25.9 g of particles containing polymer F4. The recovered particles containing polymer F4 were air-dried in a hot air circulation oven at 50 ° C for 2 hours to obtain 13.9 g of particles containing polymer F4. The particles containing polymer F after air drying were vacuum-dried at 210 ° C for 16 hours to obtain 13.7 g of particles containing polymer F4. The ion exchange capacity and TQ value of the particles containing polymer F4 after vacuum drying were measured according to the methods described above.

[0129] [Example 5] <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 55°C, nitrogen gas was introduced to 0.14 MPa, TFE was introduced, and the total pressure was set to 0.82 MPaG. 3.33 g of an initiator solution prepared by dissolving the radical polymerization initiator V-601 in HFC-52-13p (AC-2000) at a concentration of 1.40 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 13.2 g, the reactor was cooled to 10°C, and unreacted TFE was released into the air, resulting in a liquid composition 5, which was a solution in which polymer F5 was dissolved in unreacted monomer m1 and HFC-52-13p (AC-2000).

[0130] <Step 2> 100 g of Liquid Composition 5 was diluted with 105 g of HFC-52-13p (AC-2000). The diluted liquid composition was kept at 25°C and added to 611 g of HFE-347pc-f (AE-3000) at -30°C, followed by stirring to aggregate Polymer F5 and form particles containing Polymer F5.

[0131] <Step 3> After stirring, the liquid containing particles containing polymer F5 was filtered using filter paper. A mixed solvent of 179 g of HFE-347pc-f (AE-3000) and 23.1 g of HFC-52-13p (AC-2000) at 25°C was added to the separated and recovered particles containing polymer F5, followed by stirring and filtration for washing. This washing was repeated a total of three times to obtain particles containing polymer F5. 40.1 g of the recovered particles containing polymer F5 were air-dried in a hot air circulation oven at 50°C for 2 hours to obtain particles containing polymer F5. 20.2 g of the particles containing polymer F after air-drying were vacuum-dried at 80°C for 16 hours to obtain 20.1 g of particles containing polymer F5. The ion exchange capacity and TQ value of the particles containing polymer F5 after vacuum-drying were measured according to the methods described above.

[0132] [Example 6] <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 HFC-52-13p (AC-2000), and 1.05 g of a solution of HFC-52-13p (AC-2000) dissolved so that the concentration of PFB, a radical polymerization initiator, was 3.00 mass% was added, and after charging, freezing and degassing were 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 to obtain a liquid composition 6 in which polymer F6 was dissolved in unreacted monomer m2 and HFC-52-13p (AC-2000).

[0133] <Step 2> 59.9 g of Liquid Composition 6 was diluted with 73.6 g of HFC-52-13p (AC-2000). The diluted liquid composition was kept at 25°C, and this was mixed with 288 g of HFC-52-13p (AC-2000) at 25°C and CH ３ The polymer F6 was added to 73.4 g of the mixed solvent of OH and stirred to aggregate the polymer F6, thereby forming particles containing the polymer F6.

[0134] <Step 3> After stirring, 175 g of the supernatant liquid was extracted and then heated in a CH ３After adding 145 g of HCl and stirring further, the liquid containing particles containing polymer F6 was filtered using filter paper. The separated and recovered particles containing polymer F6 were mixed with 140 g of HFC-52-13p (AC-2000) at 25°C and CH ３ 60.0 g of a mixed solvent of OH was added, stirred, and then filtered to wash. Washing was repeated a total of three times to obtain 29.2 g of particles containing polymer F6. The recovered particles containing polymer F6 were air-dried in a hot air circulation oven at 50 ° C for 2 hours to obtain 14.8 g of particles containing polymer F6. The particles containing polymer F after air drying were vacuum-dried at 210 ° C for 16 hours to obtain 13.6 g of particles containing polymer F6. The ion exchange capacity and TQ value of the particles containing polymer F6 after vacuum drying were measured according to the methods described above.

[0135] 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 and subsequent steps for each example. In Table 1, "mass of polymer F / mass of first solvent" means the mass ratio of the content of polymer F to the content of the first solvent. Also, in Table 1, "mass of polymer F / mass of HFE-1" means the mass ratio of the content of polymer F to the content of HFE-1 in the liquid composition. In Table 2, "mass of second solvent / mass of first solvent in liquid composition" means the mass ratio of the mass of the second solvent used in step 2 to the mass of the first solvent in the liquid composition. Also, in Table 2, "mass of polymer F / (mass of HFE-1+mass of HFE-2)" means the mass ratio of the mass of polymer F in the liquid composition to the total mass of HFE-1 in the liquid composition and HFE-2 used in step 2. In addition, in Table 2, "mass of HFE-2 / mass of HFE-1" means the mass ratio of the mass of HFE-2 used in step 2 to the mass of HFE-1 in the liquid composition.

[0136]

[0137]

[0138] 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 impurity content (Examples 1 to 4).

[0139] The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2024-153383, filed on September 5, 2024, are incorporated herein by reference as part of the disclosure of the present invention.

Claims

1. A method for producing particles containing a fluoropolymer, comprising polymerizing a monomer containing tetrafluoroethylene and a compound having a group that can be converted into a sulfonic acid type functional group in the presence of a first hydrofluoroether to obtain a liquid composition containing a fluoropolymer and the first hydrofluoroether, and then mixing the liquid composition with a second hydrofluoroether to agglomerate the fluoropolymer and form particles containing the fluoropolymer.

2. The method for producing particles containing a fluoropolymer according to claim 1, wherein the first hydrofluoroether and the second hydrofluoroether each have 5 or less carbon atoms.

3. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the first hydrofluoroether and the second hydrofluoroether are both compounds represented by the following formula (S1): Formula (S1) R １ -O-R ２ In formula (S1), R １ and R ２ are each independently a fluoroalkyl group having 2 or less carbon atoms. １ and R ２ When one of the groups does not have a hydrogen atom, the other group has a hydrogen atom.

4. The method for producing particles containing a fluorine-containing polymer according to claim 1 or 2, wherein the first hydrofluoroether and the second hydrofluoroether are the same type of compound.

5. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein a washing treatment is carried out to wash the fluoropolymer particles with a tertiary hydrofluoroether.

6. The method for producing particles containing a fluorine-containing polymer according to claim 5, wherein the third hydrofluoroether is the same compound as at least one of the first hydrofluoroether and the second hydrofluoroether.

7. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the compound having a group that can be converted into a sulfonic acid functional group is a compound represented by the following formula (1): Formula (1) CF 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 functional group, and n is 1 or 2. When there are multiple As, each As may be the same or different.

8. A 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 hydrofluoroether in the liquid composition is 0.10 or more.

9. A method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein when the liquid composition and the second hydrofluoroether are mixed, the mass ratio of the mass of the fluoropolymer in the liquid composition to the total mass of the first hydrofluoroether and the second hydrofluoroether in the liquid composition is 0.20 or less.

10. The method for producing particles containing a fluoropolymer according to claim 1 or 2, wherein the fluoropolymer is a copolymer containing units based on tetrafluoroethylene and units based on a compound represented by the following formula (1), or a copolymer containing units based on tetrafluoroethylene, units based on a monomer having a cyclic ether structure, and units based on a fluoromonomer having a group that can be converted into a sulfonic acid functional group: Formula (1): CF 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 functional group, and n is 1 or 2. When there are multiple As, each As may be the same or different.

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