Method for producing fluoropolymer powder

Abstract

To provide a method for producing a fluoropolymer powder having a reduced content of a specific fluorine-containing compound by a simple method.SOLUTION: A method for producing a fluoropolymer powder including the step (A1) for adding an acid to a fluoropolymer aqueous dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, to adjust the pH to 4.0 or less and cause coagulation, thereby obtaining a wet fluoropolymer powder containing a fluorine-containing compound represented by the general formula (1A), and the step (B1) for heat-treating the wet fluoropolymer powder at a temperature higher than 150°C and lower than 240°C. The general formula (1A): H-(CF2)m-COOH, where m is 3 to 19.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a fluoropolymer powder. [Background technology]

[0002] When producing fluoropolymers by emulsion polymerization, fluorine-containing anionic surfactants have been used. Recently, the use of hydrocarbon surfactants instead of fluorine-containing anionic surfactants has been proposed, and various investigations are being conducted.

[0003] Patent Document 1 describes a method for producing a modified polytetrafluoroethylene powder, which is characterized by including a step of removing or reducing a compound represented by the following general formula (1) or (2) from a polytetrafluoroethylene powder obtained using a hydrocarbon surfactant: General formula (1):(H-(CF2) m -COO) p M 1 (wherein m is 3 to 19, M 1 is H, metal atom, NR 5 4(R 5 may be the same or different and are H or an organic group having 1 to 10 carbon atoms), imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent. p is 1 or 2. General formula (2):(H-(CF2) n -SO3) q M 2 (wherein n is 4 to 20. M 2 is H, metal atom, NR 5 4(R 5 may be the same or different and are H or an organic group having 1 to 10 carbon atoms), imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent. q is 1 or 2.

[0004] Patent Document 2 describes a method for reducing thermally induced discoloration of a fluoropolymer resin, the fluoropolymer resin being produced by the steps of polymerizing a fluoromonomer in an aqueous dispersion medium to form an aqueous fluoropolymer dispersion, isolating the fluoropolymer from the aqueous medium by separating the fluoropolymer resin in wet form from the aqueous medium, and drying to produce a fluoropolymer resin in dry form, and the method includes the step of exposing the fluoropolymer resin in wet or dry form to an oxidizing agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 031617 [Patent Document 2] Special Publication No. 2015-516029 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a method for producing a fluoropolymer powder having a reduced content of a specific fluorine-containing compound in a simple manner. [Means for solving the problem]

[0007] The present disclosure provides a method for producing a fluoropolymer powder (hereinafter also referred to as the "first production method of the present disclosure"), which comprises the steps of: adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using a carboxylic acid-type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the resulting mixture to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A); and heat-treating the wet fluoropolymer powder at a temperature higher than 150°C and lower than 240°C. General formula (1A): H-(CF2) m -COOH (wherein m is 3 to 19)

[0008] The wet fluoropolymer powder preferably contains two or more types of fluorine-containing compounds represented by general formula (1A). It is also preferable that the wet fluoropolymer powder does not substantially contain a salt of the fluorine-containing compound represented by general formula (1A).

[0009] Preferably, the fluoropolymer is polytetrafluoroethylene.

[0010] The present disclosure also provides a method for producing a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A): (A2) adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using an aliphatic carboxylic acid-type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the fluoropolymer powder; and A step (B2) of heat treating the wet fluoropolymer powder at a temperature above 100°C. The present invention provides a method for producing a fluoropolymer powder (hereinafter also referred to as the "second production method of the present disclosure") characterized by: General formula (1A): H-(CF2) m -COOH (wherein m is 3 to 19)

[0011] The temperature of the heat treatment is preferably more than 150°C and less than 240°C.

[0012] The wet fluoropolymer powder preferably contains two or more types of fluorine-containing compounds represented by general formula (1A).

[0013] The wet fluoropolymer powder preferably does not substantially contain a salt of the fluorine-containing compound represented by general formula (1A).

[0014] Preferably, the fluoropolymer is polytetrafluoroethylene. Hereinafter, when simply referring to the "manufacturing method of the present disclosure," it means a concept that includes both the first manufacturing method and the second manufacturing method of the present disclosure. [Effects of the Invention]

[0015] The production method of the present disclosure can produce a fluoropolymer powder having a reduced content of a specific fluorine-containing compound in a simple manner. DETAILED DESCRIPTION OF THE INVENTION

[0016] Before specifically describing the present disclosure, some terms used herein will be defined or explained.

[0017] In this specification, unless otherwise specified, the term "organic group" means a group containing one or more carbon atoms or a group formed by removing one hydrogen atom from an organic compound. Examples of the "organic group" are: an alkyl group optionally having one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents; a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group optionally having one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, a heteroaryl group optionally having one or more substituents; cyano group, formyl group, RaO-, RaCO-, RaSO2-, RaCOO-, RaNRaCO-, RaCONRa-, RaOCO-, and RaOSO2- (In these formulas, Ra independently represents: an alkyl group optionally having one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents; a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group optionally having one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, or a heteroaryl group optionally having one or more substituents Includes. The organic group is preferably an alkyl group which may have one or more substituents. In this specification, unless otherwise specified, the term "substituent" refers to a substitutable group. Examples of the "substituent" include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an acyloxy group, an acylamino group, an aliphatic oxy group, an aromatic oxy group, a heterocyclic oxy group, an aliphatic oxycarbonyl group, an aromatic oxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group, an aliphatic sulfonyl group, an aromatic sulfonyl group, a heterocyclic sulfonyl group, an aliphatic sulfonyloxy group, an aromatic sulfonyloxy group, a heterocyclic sulfonyloxy group, a sulfamoyl group, an aliphatic sulfonamido group, an aromatic sulfonamido group, a heterocyclic sulfonamido group, an amino group, an aliphatic amino group, an and hydroxy groups, cyano groups, sulfo groups, carboxy groups, aliphatic oxyamino groups, aromatic oxyamino groups, carbamoylamino groups, sulfamoylamino groups, halogen atoms, sulfamoylcarbamoyl groups, carbamoylsulfamoyl groups, dialiphatic oxyphosphinyl groups, and diaromatic oxyphosphinyl groups.

[0018] The aliphatic group may be saturated or unsaturated and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic group include alkyl groups having a total of 1 to 8, preferably 1 to 4, carbon atoms, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, and a carbamoylmethyl group.

[0019] The aromatic group may have, for example, a nitro group, a halogen atom, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic group include aryl groups having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms in total, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0020] The heterocyclic group may have a halogen atom, a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the heterocyclic group include a 5- or 6-membered heterocycle having a total of 2 to 12, preferably 2 to 10, carbon atoms, such as a 2-tetrahydrofuryl group and a 2-pyrimidyl group.

[0021] The acyl group may have an aliphatic carbonyl group, an arylcarbonyl group, a heterocyclic carbonyl group, a hydroxy group, a halogen atom, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the acyl group include acyl groups having a total of 2 to 8, preferably 2 to 4, carbon atoms, such as an acetyl group, a propanoyl group, a benzoyl group, and a 3-pyridinecarbonyl group.

[0022] The acylamino group may have an aliphatic group, an aromatic group, a heterocyclic group, etc., such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include acylamino groups having a total of 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and alkylcarbonylamino groups having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0023] The aliphatic oxycarbonyl group may be saturated or unsaturated and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic oxycarbonyl group include alkoxycarbonyl groups having a total of 2 to 8, preferably 2 to 4, carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a (t)-butoxycarbonyl group.

[0024] The carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the carbamoyl group include an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 9 carbon atoms, preferably an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 5 carbon atoms, such as an N-methylcarbamoyl group, an N,N-dimethylcarbamoyl group, and an N-phenylcarbamoyl group.

[0025] The aliphatic sulfonyl group may be saturated or unsaturated and may have a hydroxy group, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic sulfonyl group include alkylsulfonyl groups having a total of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as a methanesulfonyl group.

[0026] The aromatic sulfonyl group may have a hydroxy group, an aliphatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic sulfonyl group include arylsulfonyl groups having a total of 6 to 10 carbon atoms, such as a benzenesulfonyl group.

[0027] The amino group may have an aliphatic group, an aromatic group, a heterocyclic group, or the like.

[0028] The acylamino group may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include an acylamino group having a total of 2 to 12 carbon atoms, preferably a total of 2 to 8 carbon atoms, and more preferably an alkylcarbonylamino group having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0029] The aliphatic sulfonamide group, aromatic sulfonamide group, and heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, or a 2-pyridinesulfonamide group.

[0030] The sulfamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the sulfamoyl group include a sulfamoyl group, an alkylsulfamoyl group having 1 to 9 carbon atoms in total, a dialkylsulfamoyl group having 2 to 10 carbon atoms in total, an arylsulfamoyl group having 7 to 13 carbon atoms in total, and a heterocyclic sulfamoyl group having 2 to 12 carbon atoms in total, more preferably a sulfamoyl group, an alkylsulfamoyl group having 1 to 7 carbon atoms in total, a dialkylsulfamoyl group having 3 to 6 carbon atoms in total, an arylsulfamoyl group having 6 to 11 carbon atoms in total, and a heterocyclic sulfamoyl group having 2 to 10 carbon atoms in total, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group, and a 4-pyridine sulfamoyl group.

[0031] The aliphatic oxy group may be saturated or unsaturated and may have a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc. Examples of the aliphatic oxy group include alkoxy groups having a total of 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, and a methoxyethoxy group.

[0032] The aromatic amino group and heterocyclic amino group may have an aliphatic group, an aliphatic oxy group, a halogen atom, a carbamoyl group, a heterocyclic group fused with the aryl group, an aliphatic oxycarbonyl group, preferably an aliphatic group having 1 to 4 carbon atoms in total, an aliphatic oxy group having 1 to 4 carbon atoms in total, a halogen atom, a carbamoyl group having 1 to 4 carbon atoms in total, a nitro group, or an aliphatic oxycarbonyl group having 2 to 4 carbon atoms in total.

[0033] The aliphatic thio group may be saturated or unsaturated and is an alkylthio group having a total of 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, such as a methylthio group, an ethylthio group, a carbamoylmethylthio group, or a t-butylthio group.

[0034] The carbamoylamino group may have an aliphatic group, an aryl group, a heterocyclic group, etc. Examples of the carbamoylamino group include a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 9 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 10 carbon atoms, an arylcarbamoylamino group having a total of 7 to 13 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 12 carbon atoms, preferably a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 7 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 6 carbon atoms, an arylcarbamoylamino group having a total of 7 to 11 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 10 carbon atoms, such as a carbamoylamino group, a methylcarbamoylamino group, an N,N-dimethylcarbamoylamino group, a phenylcarbamoylamino group, and a 4-pyridinecarbamoylamino group. The manufacturing method of the present disclosure will be described in detail below.

[0035] When a fluoropolymer powder is obtained by polymerization using a hydrocarbon surfactant, the fluoropolymer powder may contain specific fluorine-containing compounds represented by the following general formulas (1) and (2). General formula (1):(H-(CF2) m -COO) p M 1 (wherein m is 3 to 19, M 1 is H, metal atom, NR 5 4(R 5 may be the same or different and are H or an organic group having 1 to 10 carbon atoms), imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent. p is 1 or 2. General formula (2):(H-(CF2) n -SO3) q M 2 (wherein n is 4 to 20. M 2 is H, metal atom, NR 5 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. q is 1 or 2. It is desirable to remove the specific fluorine-containing compounds represented by the above general formulas (1) and (2) from the fluoropolymer powder, but in order to remove the specific fluorine-containing compounds, an additional step such as a fluorination treatment has been required. The manufacturing method of the present disclosure is to obtain a wet fluoropolymer powder from an aqueous fluoropolymer dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, and to obtain a wet fluoropolymer powder from the aqueous fluoropolymer dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, a fluorine-containing compound represented by general formula (1) contained in the wet fluoropolymer powder is added. 1 The present inventors have found that by carrying out a specific heat treatment in a state where the fluorine-containing compound is -COOH, a fluoropolymer powder having a reduced amount of the above-mentioned fluorine-containing compound can be obtained without carrying out any complicated steps.

[0036] The first production method of the present disclosure includes a step (A1) of adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the mixture to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A), and a step (B1) of heat-treating the wet fluoropolymer powder at more than 150°C and less than 240°C. The first production method of the present disclosure, by virtue of having the above-described configuration, is capable of obtaining a fluoropolymer powder in which the specific fluorine-containing compounds represented by the above general formulas (1) and (2) are reduced, despite being a simple method. Furthermore, since the specific fluorine-containing compounds represented by the general formulas (1) and (2) can be reduced at a relatively low temperature, not only is the fluorine-containing compounds represented by the general formulas (1) and (2) reduced, but fusion of the resulting fluoropolymer powder can also be suppressed.

[0037] The above step (A1) is a step of adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the dispersion to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A): A wet fluoropolymer powder containing the fluorine-containing compound represented by the general formula (1A) can be obtained by adding an acid to the aqueous fluoropolymer dispersion and adjusting the pH to 4.0 or less to carry out coagulation. By adjusting the pH of the aqueous dispersion to 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, still more preferably 2.5 or less, and particularly preferably 2.0 or less, the fluorine-containing compound represented by general formula (1) contained in the aqueous fluoropolymer dispersion can be converted to the fluorine-containing compound represented by general formula (1A). This gives a wet fluoropolymer powder containing the fluorine-containing compound represented by general formula (1A), and the contents of the fluorine-containing compounds represented by general formulas (1) and (2) can be reduced by the heat treatment carried out in step (B1).

[0038] The acid may be an organic acid or an inorganic acid, but inorganic acids are preferred because they are less likely to remain after heat treatment. In particular, at least one acid selected from the group consisting of nitric acid, sulfuric acid, fuming sulfuric acid, perchloric acid, and hydrochloric acid is preferred, and at least one acid selected from the group consisting of nitric acid, sulfuric acid, and hydrochloric acid is more preferred. As the organic acid, succinic acid, oxalic acid, citric acid, trifluoroacetic acid, etc. may be used. The amount of the acid to be added is not limited and may be appropriately set depending on the pH of the aqueous fluoropolymer dispersion, etc.

[0039] The method of coagulating by adding the acid includes, for example, stirring the aqueous dispersion while adding the acid. More specifically, the fluoropolymer can be coagulated by stirring in a vessel equipped with a stirrer to obtain a wet fluoropolymer powder containing the fluorine-containing compound represented by general formula (1A). The coagulation can also be carried out continuously using an in-line mixer or the like.

[0040] In the step (A1), the temperature for the coagulation is not limited, but can be, for example, 3 to 80° C. From the viewpoint of dispersion stability, the temperature is preferably 5° C. or higher, more preferably 10° C. or higher. Moreover, from the viewpoint of suppressing granulation of secondary particles, the temperature is preferably 60° C. or lower.

[0041] The step (B1) is a step of heat-treating a wet fluoropolymer powder containing a fluorine-containing compound represented by the general formula (1A) at more than 150° C. and less than 240° C. By converting the fluorine-containing compound represented by the general formula (1) into a fluorine-containing compound represented by the general formula (1A) and then heat-treating it, the amount of the fluorine-containing compound represented by the general formula (1) contained in the fluoropolymer powder can be efficiently reduced while suppressing fusion of the resulting fluoropolymer powder.

[0042] In the step (B1), the heat treatment temperature is more than 150° C. and less than 240° C. In order to more efficiently reduce the specific fluorine-containing compounds, the heat treatment temperature is preferably 155° C. or higher, more preferably 160° C. or higher, even more preferably 165° C. or higher, still more preferably 170° C. or higher, particularly preferably 175° C. or higher, and particularly preferably 180° C. or higher. From the viewpoint of suppressing fusion of the fluoropolymer powder, 235°C or less is more preferable, 230°C or less is even more preferable, 225°C or less is even more preferable, 220°C or less is particularly preferable, 215°C or less is particularly preferable, and 210°C or less is most preferable.

[0043] The heat treatment is preferably for drying the wet fluoropolymer powder. The term "drying" refers to a heat treatment that reduces the moisture content of the wet fluoropolymer powder to 0.01% by mass or less. The drying temperature is more than 150° C. and less than 240° C. In order to more efficiently reduce the specific fluorine-containing compound, the drying temperature is preferably 155° C. or higher, more preferably 160° C. or higher, even more preferably 165° C. or higher, still more preferably 170° C. or higher, particularly preferably 175° C. or higher, and particularly preferably 180° C. or higher. From the viewpoint of suppressing fusion of the fluoropolymer powder, 235°C or less is more preferable, 230°C or less is even more preferable, 225°C or less is even more preferable, 220°C or less is particularly preferable, 215°C or less is particularly preferable, and 210°C or less is most preferable.

[0044] The first production method of the present disclosure can efficiently reduce the specific fluorine-containing compound even when the temperature of the heat treatment or drying is relatively low, and therefore can suppress fusion. In this specification, fusion refers to a significant change in the average particle size before and after drying, particularly an increase in the average particle size after drying. The degree of fusion can be evaluated, for example, by the increase in the particle size when sieved through a 10-mesh sieve. Up rate = (amount remaining on 10 mesh (g)) / (total amount of sieved fluoropolymer (g)) x 100 According to the first production method of the present disclosure, fusion can be suppressed, the increase rate is preferably 5% or less, and more preferably 3% or less, and productivity can be improved. The method for measuring the average particle size may be appropriately selected depending on the type of fluoropolymer. For example, in the case of low-molecular-weight PTFE, the average particle size is the particle size corresponding to 50% of the integrated particle size distribution obtained by measuring the particle size distribution using a laser diffraction particle size distribution analyzer (manufactured by Nippon Laser Corporation) without using a cascade, at a pressure of 0.1 MPa, for a measurement time of 3 seconds. In the case of high molecular weight PTFE, the average particle size is a value measured in accordance with JIS K6891.

[0045] From the viewpoint of efficiently removing or reducing the fluorine-containing compound represented by general formula (1A), the heat treatment or drying time is preferably 120 minutes or more, more preferably 180 minutes or more, even more preferably 240 minutes or more, and even more preferably 300 minutes or more. The upper limit of the heat treatment or drying time is not particularly limited, but may be, for example, 1500 minutes or less, or 1200 minutes or less.

[0046] In the heat treatment or drying, it is preferable to control the temperature to less than 240°C or not exceed 240°C. However, the temperature may be equal to or greater than 240°C as long as the effects of the present disclosure are not impaired. In the heat treatment or drying, the time during which the temperature is equal to or greater than 240°C is preferably 120 minutes or less from the viewpoint of suppressing fusion of the powder. More preferably, it is 90 minutes or less, even more preferably, it is 60 minutes or less, and even more preferably, it is 30 minutes or less. Furthermore, in the heat treatment or drying, the time during which the temperature is equal to or greater than 240°C is preferably 40% or less of the total drying time from the viewpoint of suppressing fusion of the powder as long as the effects of the present disclosure are not impaired. More preferably, it is 30% or less, even more preferably, it is 20% or less, even more preferably, it is 10% or less, especially preferably, it is 5% or less, and especially preferably, it is 3% or less.

[0047] The second production method of the present disclosure includes a step (A2) of adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using an aliphatic carboxylic acid-type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the dispersion to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A), and a step (B2) of heat-treating the wet fluoropolymer powder at a temperature exceeding 100°C. General formula (1A): H-(CF2) m -COOH (wherein m is 3 to 19) The second production method of the present disclosure has the above-mentioned configuration, and therefore, is a simple method, yet can produce a fluoropolymer powder in which the content of the specific fluorine-containing compounds represented by the general formulas (1) and (2) is reduced.

[0048] The above step (A2) is a step of adding an acid to an aqueous fluoropolymer dispersion obtained by polymerization using an aliphatic carboxylic acid type hydrocarbon surfactant, adjusting the pH to 4.0 or less, and coagulating the dispersion to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A):

[0049] By adjusting the pH of the aqueous dispersion to 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, still more preferably 2.5 or less, and particularly preferably 2.0 or less, the fluorine-containing compound represented by general formula (1) contained in the aqueous fluoropolymer dispersion can be converted to the fluorine-containing compound represented by general formula (1A). This gives a wet fluoropolymer powder containing the fluorine-containing compound represented by general formula (1A), and the contents of the fluorine-containing compounds represented by general formulas (1) and (2) can be reduced by the heat treatment carried out in step (B2).

[0050] The acid may be an organic acid or an inorganic acid, but inorganic acids are preferred because they are less likely to remain after heat treatment. In particular, at least one acid selected from the group consisting of nitric acid, sulfuric acid, fuming sulfuric acid, perchloric acid, and hydrochloric acid is preferred, and at least one acid selected from the group consisting of nitric acid, sulfuric acid, and hydrochloric acid is more preferred. As the organic acid, succinic acid, oxalic acid, citric acid, trifluoroacetic acid, etc. may be used. The amount of the acid to be added is not limited and may be appropriately set depending on the pH of the aqueous fluoropolymer dispersion, etc.

[0051] The method of coagulating by adding an acid includes, for example, stirring the aqueous dispersion while adding an acid. The fluoropolymer is coagulated by stirring in a vessel equipped with a stirrer, to obtain a wet fluoropolymer powder containing the fluorine-containing compound represented by general formula (1A). The coagulation may also be carried out continuously using an in-line mixer or the like.

[0052] In the step (A2), the coagulation temperature is not limited, but can be, for example, 3 to 80° C. From the viewpoint of dispersion stability, the temperature is preferably 5° C. or higher, more preferably 10° C. or higher. Moreover, from the viewpoint of suppressing granulation of secondary particles, the temperature is preferably 60° C. or lower.

[0053] In the step (B2), the heat treatment temperature is higher than 100° C. The heat treatment temperature is preferably 110° C. or higher, more preferably 120° C. or higher, even more preferably 130° C. or higher, and particularly preferably 140° C. or higher, since this allows the specific fluorine-containing compound to be reduced more efficiently. Furthermore, since the specific fluorine-containing compound can be reduced even more efficiently, the temperature is preferably higher than 150°C, more preferably 155°C or higher, even more preferably 160°C or higher, even more preferably 165°C or higher, particularly preferably 170°C or higher, particularly preferably 175°C or higher, and most preferably 180°C or higher. From the viewpoint of suppressing fusion of the fluoropolymer powder, the temperature is preferably 240°C or less, more preferably less than 240°C, more preferably 235°C or less, even more preferably 230°C or less, even more preferably 225°C or less, particularly preferably 220°C or less, particularly preferably 215°C or less, and most preferably 210°C or less.

[0054] In the step (B2), the heat treatment is preferably for drying the wet fluoropolymer powder. The term "drying" as used herein means heat treatment to reduce the moisture content of the wet fluoropolymer powder to 0.010% by mass or less. The drying temperature is above 100° C. The drying temperature is preferably 110° C. or higher, more preferably 120° C. or higher, even more preferably 130° C. or higher, and particularly preferably 140° C. or higher, since this allows for more efficient reduction of the specific fluorine-containing compound. Furthermore, since the above-mentioned specific fluorine-containing compound can be reduced even more efficiently, the drying temperature is preferably above 150°C, more preferably 155°C or higher, even more preferably 160°C or higher, even more preferably 165°C or higher, particularly preferably 170°C or higher, particularly preferably 175°C or higher, and most preferably 180°C or higher. From the viewpoint of suppressing fusion of the fluoropolymer powder, the temperature is preferably 240°C or less, more preferably less than 240°C, more preferably 235°C or less, even more preferably 230°C or less, even more preferably 225°C or less, particularly preferably 220°C or less, particularly preferably 215°C or less, and most preferably 210°C or less.

[0055] The second production method of the present disclosure can efficiently reduce the specific fluorine-containing compound even when the temperature for the heat treatment or drying is relatively low, and therefore can also suppress fusion. In this specification, fusion refers to a significant change in the average particle size before and after drying, particularly an increase in the average particle size after drying. The degree of fusion can be evaluated, for example, by the increase in the particle size when sieved through a 10-mesh sieve. Up rate = (amount remaining on 10 mesh (g)) / (total amount of sieved fluoropolymer (g)) x 100 According to the manufacturing method of the present disclosure, fusion can be suppressed, the increase rate is preferably 5% or less, and more preferably 3% or less, and productivity can be improved. The method for measuring the average particle size may be appropriately selected depending on the type of fluoropolymer. For example, in the case of low-molecular-weight PTFE, the average particle size is the particle size corresponding to 50% of the integrated particle size distribution obtained by measuring the particle size distribution using a laser diffraction particle size distribution analyzer (manufactured by Nippon Laser Corporation) without using a cascade, at a pressure of 0.1 MPa, for a measurement time of 3 seconds. In the case of high molecular weight PTFE, the average particle size is a value measured in accordance with JIS K6891.

[0056] From the viewpoint of efficiently removing or reducing the fluorine-containing compound represented by general formula (1A), the heat treatment or drying time is preferably 120 minutes or more, more preferably 180 minutes or more, even more preferably 240 minutes or more, and even more preferably 300 minutes or more. The upper limit of the heat treatment or drying time is not particularly limited, but may be, for example, 1500 minutes or less, or 1200 minutes or less.

[0057] In the heat treatment or drying, it is preferable to control the temperature to less than 240°C or not exceed 240°C. However, the temperature may be equal to or greater than 240°C as long as the effects of the present disclosure are not impaired. In the heat treatment or drying, the time during which the temperature is equal to or greater than 240°C is preferably 120 minutes or less from the viewpoint of suppressing fusion of the powder. More preferably, it is 90 minutes or less, even more preferably, it is 60 minutes or less, and even more preferably, it is 30 minutes or less. Furthermore, in the heat treatment or drying, the time during which the temperature is equal to or greater than 240°C is preferably 40% or less of the total drying time from the viewpoint of suppressing fusion of the powder as long as the effects of the present disclosure are not impaired. More preferably, it is 30% or less, even more preferably, it is 20% or less, even more preferably, it is 10% or less, especially preferably, it is 5% or less, and especially preferably, it is 3% or less.

[0058] In the manufacturing method of the present disclosure, the wet powder obtained by coagulating the fluoropolymer is usually dried using means such as vacuum, high frequency, or hot air while keeping the wet powder in a state where it is not very fluid, preferably in a state where it is left stationary. For example, when the fluoropolymer is PTFE, friction between powders, especially at high temperatures, generally has an adverse effect on fine powder PTFE, since particles of this type of PTFE tend to easily fibrillate even with a small shear force, losing their original stable particle structure. In this specification, the presence or absence of fibrillating properties can be determined by "paste extrusion," a typical method for molding "high molecular weight PTFE powder," which is a powder (fine powder) made from an emulsion polymer of TFE. Paste extrusion is usually possible because high molecular weight PTFE powder has fibrillating properties. If the unsintered molded product obtained by paste extrusion has no substantial strength or elongation, for example, if it breaks when pulled at 0% elongation, it can be considered to have no fibrillating properties.

[0059] In the production method of the present disclosure, the solids concentration of the aqueous fluoropolymer dispersion is not limited, but may be, for example, 1.0 to 70.0 mass%. The solids concentration is preferably 8.0 mass% or more, more preferably 10.0 mass% or more, and is preferably 60.0 mass% or less, more preferably 50.0 mass% or less. From the viewpoint of reducing uncoagulated components, the solids concentration is also preferably 10.0 to 25.0 mass%, preferably 10.0 to 22.0 mass%, more preferably 10.0 to 20.0 mass%. The production method of the present disclosure may include a step of diluting the aqueous fluoropolymer dispersion by adding water. For example, the dilution can be performed so that the solid content concentration becomes 10.0 to 25.0 mass %. In the above-mentioned aqueous fluoropolymer dispersion, the content of the fluorine-containing compound represented by general formula (1) is not particularly limited.For example, it is preferable that the content of the fluorine-containing compound represented by general formula (1) contained in the wet fluoropolymer powder obtained after coagulation is within the range described below.

[0060] To increase the bulk density of the fluoropolymer powder, it is preferable that the fluoropolymer solids concentration in the aqueous fluoropolymer dispersion is high. When the fluoropolymer solids concentration in the aqueous fluoropolymer dispersion for coagulation is high, the degree of association of the fluoropolymer primary particles increases, and the fluoropolymer primary particles densely associate and aggregate to form granules. When the fluoropolymer solids concentration in the aqueous fluoropolymer dispersion is less than 8% by mass, the aggregate density of the fluoropolymer primary particles tends to become sparse, making it difficult to obtain a fluoropolymer powder with a high bulk density. On the other hand, when the fluoropolymer solids concentration in the aqueous fluoropolymer dispersion is too high, the amount of unagglomerated fluoropolymer increases, and the concentration of unagglomerated fluoropolymer solids in the coagulation wastewater increases. A high concentration of unagglomerated fluoropolymer solids in the coagulation wastewater can lead to pipe blockage and increased costs and effort for wastewater treatment. Furthermore, the yield of the fluoropolymer powder decreases. The concentration of unaggregated fluoropolymer solids in the coagulation wastewater is preferably low from the viewpoint of productivity of the fluoropolymer powder, more preferably less than 0.4 mass%, further preferably less than 0.3 mass%, particularly preferably less than 0.2 mass%. If the fluoropolymer solids concentration of the aqueous fluoropolymer dispersion exceeds 25 mass%, it is difficult to reduce the concentration of unaggregated fluoropolymer solids in the coagulation wastewater to less than 0.4 mass%. The fluoropolymer solids concentration in the aqueous fluoropolymer dispersion obtained in the polymerization step described below is approximately 8 to 45 mass %, so if the fluoropolymer solids concentration is high, it may be adjusted to 8 to 25 mass % by adding a dilution solvent such as water. Also, if the fluoropolymer solids concentration in the aqueous fluoropolymer dispersion after emulsion polymerization is 8 to 25 mass %, the aqueous fluoropolymer dispersion can be used as is as the aqueous fluoropolymer dispersion.

[0061] In the production method of the present disclosure, the content of the fluorine-containing compound represented by general formula (1) contained in the fluoropolymer aqueous dispersion is not limited, but is, for example, about 1 ppb to 10,000 ppm, preferably 100 ppb or more, more preferably 1 ppm or more, even more preferably 10 ppm or more, and particularly preferably 100 ppm or more, relative to the fluoropolymer. The aqueous dispersion to be subjected to the heat treatment may contain one or more fluorine-containing compounds represented by general formula (1), but the production method of the present disclosure is particularly effective when two or more fluorine-containing compounds are contained. For example, an embodiment may include a fluorine-containing compound in which m is 7 in general formula (1) and a fluorine-containing compound in which m is 13. In addition, as long as two or more types are included, three or more types, or four or more types may be included, and all of the fluorine-containing compounds encompassed by the above general formula (1) may be included. The aqueous dispersion to be subjected to heat treatment may contain, as the fluorine-containing compounds, a fluorine-containing compound in which m is 7 or less and a fluorine-containing compound in which m is 8 or more in general formula (1A), or may contain a fluorine-containing compound in which m is 8 or less and a fluorine-containing compound in which m is 9 or more in general formula (1A).

[0062] The aqueous fluoropolymer dispersion may be an embodiment in which, among fluorine-containing compounds encompassed by general formula (1), it contains fluorine-containing compounds in which m is 3, 5, 7, 9, 11, 13, 15, 17, and 19, and does not contain fluorine-containing compounds in which m is 4, 6, 8, 10, 12, 14, 16, and 18; it may be an embodiment in which it contains fluorine-containing compounds in which m is 4, 6, 8, 10, 12, 14, 16, 18, and 20, and does not contain fluorine-containing compounds in which m is 3, 5, 7, 9, 11, 13, 15, 17, and 19; or it may be an embodiment in which it contains all fluorine-containing compounds in which m is 3 to 19.

[0063] In the production method of the present disclosure, the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is not particularly limited, and an aqueous fluoropolymer dispersion of any concentration can be coagulated. The aqueous fluoropolymer dispersion subjected to coagulation may have a total amount of the fluorine-containing compound represented by the general formula (1) of 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, 10 ppm or more, or 100 ppm or more, based on the fluoropolymer. The total amount may also be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more, based on the total amount of water. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is at least as high as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the fluoropolymer aqueous dispersion to be treated may contain 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less of the fluorine-containing compound represented by the general formula (1) relative to the fluoropolymer. By ensuring that the total amount of the fluorine-containing compounds in water is within the above range, the removal efficiency can be further improved. In this specification, ppm and ppb refer to values ​​calculated on a mass basis unless otherwise specified.

[0064] The amount of at least one of the fluorine-containing compounds in which m in the general formula (1) is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, 10 ppm or more, or 100 ppm or more, based on the total amount of water. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of at least one of the fluorine-containing compounds in which m in the general formula (1) is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the total amount of water. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0065] The amount of the fluorine-containing compound in which m is 3 in the above general formula (1) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 3 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0066] The amount of the fluorine-containing compound in which m is 4 in the above general formula (1) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 4 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0067] The amount of the fluorine-containing compound in which m is 5 in the above general formula (1) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 5 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0068] The amount of the fluorine-containing compound in which m is 6 in the above general formula (1) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 6 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0069] The amount of the fluorine-containing compound in which m in the general formula (1) is 7 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 7 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0070] The amount of the fluorine-containing compound in which m is 8 in the above general formula (1) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 8 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0071] The amount of the fluorine-containing compound in which m in the general formula (1) is 9 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 9 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0072] The amount of the fluorine-containing compound in which m in the general formula (1) is 10 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 10 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0073] The amount of the fluorine-containing compound in which m in the general formula (1) is 11 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 11 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0074] The amount of the fluorine-containing compound in which m in the general formula (1) is 12 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 12 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0075] The amount of the fluorine-containing compound in which m in the general formula (1) is 13 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 13 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0076] The amount of the fluorine-containing compound in which m in the general formula (1) is 14 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 14 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0077] The amount of the fluorine-containing compound in which m in the general formula (1) is 15 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 15 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0078] The amount of the fluorine-containing compound in which m in the general formula (1) is 16 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 16 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0079] The amount of the fluorine-containing compound in which m in the general formula (1) is 17 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 17 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0080] The amount of the fluorine-containing compound in which m in the general formula (1) is 18 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 18 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0081] The amount of the fluorine-containing compound in which m in the general formula (1) is 19 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1) in the aqueous fluoropolymer dispersion is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1) is 19 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. When the amount of the fluorine-containing compound in the aqueous fluoropolymer dispersion is within the above range, the removal efficiency can be further improved.

[0082] The fluorine-containing compound represented by the general formula (1) contained in the aqueous fluoropolymer dispersion is a fluorine-containing compound represented by the general formula (1), in which M 1 is a metal atom, NR 5 4(R 5may be the same or different, and are preferably H or an organic group having 1 to 10 carbon atoms), imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent. By adding an acid to the aqueous fluoropolymer dispersion to adjust the pH to 4.0 or less, such a fluorine-containing compound can be converted into a fluorine-containing compound represented by general formula (1A). Therefore, according to the production method of the present disclosure, a fluorine-containing compound represented by general formula (1), wherein M 1 H, metal atoms, NR 5 4(R 5 may be the same or different, and may be H or an organic group having 1 to 10 carbon atoms), imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent, and a fluoropolymer powder which does not contain or contains almost no fluorine-containing compound.

[0083] The aqueous fluoropolymer dispersion after the addition of the acid contains a salt of a fluorine-containing compound represented by general formula (1A) (preferably a fluorine-containing compound represented by general formula (1), in which M 1 is a metal atom, NR 5 4(R 5 may be the same or different, and are H or an organic group having 1 to 10 carbon atoms), an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent). In the aqueous dispersion, being substantially free of a salt of a fluorine-containing compound represented by general formula (1A) means that the content of the salt of a fluorine-containing compound represented by general formula (1A) is 500 ppb or less for each m. For example, the salt of a fluorine-containing compound represented by general formula (1A) where m is 3 may be 400 ppb, and the salt of a fluorine-containing compound where m is 9 may be 400 ppb or less, and the total amount of the salt of a fluorine-containing compound where m is 3 to 19 may be 500 ppb or less. The content of the salt of the fluorine-containing compound represented by general formula (1A) may be 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, or 10 ppb or less for all m. By adding an acid to adjust the pH to 4.0 or less, it is possible to obtain an aqueous fluoropolymer dispersion that is substantially free of the salt of the fluorine-containing compound represented by general formula (1A) as described above.

[0084] The content of the salt of the fluorine-containing compound represented by general formula (1A) in the aqueous fluoropolymer dispersion can be measured, for example, by ion chromatography.

[0085] The wet fluoropolymer powder in the above steps (A1) and (A2) may be any powder obtained by coagulating an aqueous fluoropolymer dispersion obtained by polymerization, and may contain, for example, water, a fluoropolymer powder, and a fluorine-containing compound represented by general formula (1A). The water content in the wet fluoropolymer powder is not limited, but is, for example, about 0.01 to 1000% by mass relative to the wet fluoropolymer powder. The water content in the wet fluoropolymer powder is a value calculated by the following formula. (Water content in wet fluoropolymer powder)=((mass of wet fluoropolymer powder)−(mass of fluoropolymer powder obtained by freeze-drying)) / (mass of wet fluoropolymer powder)×100

[0086] The wet fluoropolymer powder used in steps (A1) and (A2) contains a fluorine-containing compound represented by the general formula (1A). The content of the fluorine-containing compound represented by the general formula (1A) is not limited. For example, it may be 1 ppb or more, 10 ppb or more, 100 ppb or more, 1 ppm or more, 10 ppm or more, or 100 ppm or more relative to the fluoropolymer. It may also be 10,000 ppm or less, or 1,000 ppm or less relative to the fluoropolymer.

[0087] In the above steps (A1) and (A2), an acid is added to adjust the pH to 4.0 or less and coagulate, thereby obtaining a wet fluoropolymer powder containing a fluorine-containing compound represented by general formula (1A). The wet fluoropolymer powder in the above steps (B1) and (B2) may contain one or more fluorine-containing compounds represented by general formula (1A). When two or more types are contained, the production method of the present disclosure is particularly effective. For example, an embodiment may include a fluorine-containing compound in which m in general formula (1A) is 7 and a fluorine-containing compound in which m is 13. In addition, as long as two or more types are included, three or more types, or four or more types may be included, and all fluorine-containing compounds encompassed by the above general formula (1A) may be included. The wet fluoropolymer powder in steps (B1) and (B2) may contain, as the fluorine-containing compound, a fluorine-containing compound in which m in general formula (1A) is 7 or less and a fluorine-containing compound in which m in general formula (1A) is 8 or more, or may contain a fluorine-containing compound in which m in general formula (1A) is 8 or less and a fluorine-containing compound in which m in general formula (1A) is 9 or more.

[0088] The wet fluoropolymer powder in steps (B1) and (B2) may be an embodiment in which, among fluorine-containing compounds encompassed by general formula (1A), it contains fluorine-containing compounds in which m is 3, 5, 7, 9, 11, 13, 15, 17, and 19, and does not contain fluorine-containing compounds in which m is 4, 6, 8, 10, 12, 14, 16, and 18; it may be an embodiment in which it contains fluorine-containing compounds in which m is 4, 6, 8, 10, 12, 14, 16, 18, and 20, and does not contain fluorine-containing compounds in which m is 3, 5, 7, 9, 11, 13, 15, 17, and 19; or it may be an embodiment in which it contains all fluorine-containing compounds in which m is 3 to 19.

[0089] In the manufacturing method of the present disclosure, the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder to be subjected to heat treatment is not particularly limited, and wet fluoropolymer powder of any concentration can be treated. The wet fluoropolymer powder may have a total amount of the compound represented by the general formula (1A) of 0.01 ppm or more, 0.1 ppm or more, or 0.5 ppm or more relative to the fluoropolymer. The total amount may be 1 ppm or more, 5 ppm or more, 10 ppm or more, or 100 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is at least a certain level as described above, the manufacturing method of the present disclosure exhibits higher removal efficiency. The wet fluoropolymer powder may contain, relative to the fluoropolymer, 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less of the fluorine-containing compound represented by general formula (1A). By ensuring that the total amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved. In this specification, ppm and ppb refer to values ​​calculated on a mass basis unless otherwise specified.

[0090] The amount of at least one of the fluorine-containing compounds in which m in the general formula (1A) is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more, based on the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of at least one of the fluorine-containing compounds in which m in the general formula (1A) is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0091] The amount of the fluorine-containing compound in which m is 3 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 3 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0092] The amount of the fluorine-containing compound in which m is 4 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more, relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the production method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 4 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0093] The amount of the fluorine-containing compound in which m is 5 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 5 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0094] The amount of the fluorine-containing compound in which m is 6 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 6 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0095] The amount of the fluorine-containing compound in which m in the general formula (1A) is 7 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 7 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0096] The amount of the fluorine-containing compound in which m is 8 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 8 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0097] The amount of the fluorine-containing compound in which m is 9 in the above general formula (1A) may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 9 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0098] The amount of the fluorine-containing compound in which m in the general formula (1A) is 10 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 10 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0099] The amount of the fluorine-containing compound in which m in the general formula (1A) is 11 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 11 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0100] The amount of the fluorine-containing compound in which m in the general formula (1A) is 12 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 12 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0101] The amount of the fluorine-containing compound in which m in the general formula (1A) is 13 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 13 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0102] The amount of the fluorine-containing compound in which m in the general formula (1A) is 14 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 14 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0103] The amount of the fluorine-containing compound in which m in the general formula (1A) is 15 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 15 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0104] The amount of the fluorine-containing compound in which m in the general formula (1A) is 16 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 16 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0105] The amount of the fluorine-containing compound in which m in the general formula (1A) is 17 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 17 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0106] The amount of the fluorine-containing compound in which m in the general formula (1A) is 18 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 18 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0107] The amount of the fluorine-containing compound in which m in the general formula (1A) is 19 may be 0.01 ppm or more, 0.1 ppm or more, 0.5 ppm or more, 1 ppm or more, 5 ppm or more, or 10 ppm or more relative to the fluoropolymer. When the concentration of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder is equal to or higher than a certain level as described above, the removal method of the present disclosure exhibits higher removal efficiency. Furthermore, the amount of the fluorine-containing compound in which m in the general formula (1A) is 19 may be 10,000 ppm or less, 5,000 ppm or less, 2,000 ppm or less, 1,000 ppm or less, 500 ppm or less, or 200 ppm or less, relative to the fluoropolymer. By ensuring that the amount of the fluorine-containing compound in the wet fluoropolymer powder is within the above range, the removal efficiency can be further improved.

[0108] The wet fluoropolymer powder is a salt of a fluorine-containing compound represented by general formula (1A) (preferably a fluorine-containing compound represented by general formula (1), in which M 1 is a metal atom, NR 5 4(R 5 may be the same or different, and are H or an organic group having 1 to 10 carbon atoms), optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium), and is preferably substantially free of such a fluorine-containing compound. In the wet fluoropolymer powder, "substantially free of salts of fluorine-containing compounds represented by general formula (1A)" means that the content of salts of fluorine-containing compounds represented by general formula (1A) is 500 ppb or less for each m. For example, the content of salts of fluorine-containing compounds represented by general formula (1A) where m is 3 may be 400 ppb, and the content of salts of fluorine-containing compounds where m is 9 may be 400 ppb or less, and the total content of salts of fluorine-containing compounds where m is 3 to 19 may be 500 ppb or less. The content of the salt of the fluorine-containing compound represented by general formula (1A) may be 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 10 ppb or less, or less than 10 ppb for all m.

[0109] The content of the salt of the fluorine-containing compound represented by general formula (1A) in the wet fluoropolymer powder can be measured, for example, by ion chromatography.

[0110] By adding pigments for coloring or various fillers for improving mechanical properties before or during the coagulation, it is also possible to obtain a pigmented or filled fluoropolymer powder in which the pigments and fillers are uniformly mixed.

[0111] The first production method of the present disclosure may also include a step of recovering the coagulated wet fluoropolymer powder after step (A1) and before step (B1). The second production method of the present disclosure may also include a step of recovering the coagulated wet fluoropolymer powder after step (A2) and before step (B2).

[0112] The aqueous fluoropolymer dispersion in step (A1) is obtained by polymerizing a fluoromonomer using a carboxylic acid-type hydrocarbon surfactant. The first production method of the present disclosure also preferably includes a polymerization step of obtaining the aqueous fluoropolymer dispersion by polymerizing a fluoromonomer in an aqueous medium in the presence of a carboxylic acid-type hydrocarbon surfactant.

[0113] The aqueous fluoropolymer dispersion in step (A2) is obtained by polymerizing a fluoromonomer using an aliphatic carboxylic acid-type hydrocarbon surfactant. The second production method of the present disclosure also preferably includes a polymerization step of obtaining an aqueous fluoropolymer dispersion by polymerizing a fluoromonomer in an aqueous medium in the presence of an aliphatic carboxylic acid-type hydrocarbon surfactant.

[0114] In the production method of the present disclosure, an aqueous fluoropolymer dispersion containing a fluorine-containing compound represented by general formula (1) but substantially free of a compound represented by general formula (2) can be obtained by a polymerization step described below using a carboxylic acid-type hydrocarbon surfactant or an aliphatic carboxylic acid-type hydrocarbon surfactant. In the following description, where the term "carboxylic acid type hydrocarbon surfactant" is used, the term "aliphatic carboxylic acid type hydrocarbon surfactant" is used in the second production method of the present disclosure.

[0115] The fluoromonomer preferably has at least one double bond. Examples of the fluoromonomers include tetrafluoroethylene [TFE], hexafluoropropylene [HFP], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VDF], trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, and fluoroalkyl ethers represented by the general formula (100): CHX 101 =CX 102 Rf 101 (In the formula, X 101 and X 102 is H on one side and F on the other side, and Rf 101 is preferably at least one selected from the group consisting of a fluoromonomer represented by (a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), a fluorinated vinyl heterocyclic compound, and a monomer that provides a crosslinking site.

[0116] Examples of the fluoroalkyl vinyl ether include: General formula (110): CF2=CF-ORf 111 (In the formula, Rf 111 represents a perfluoroorganic group; General formula (120): CF2=CF-OCH2-Rf 121 (In the formula, Rf 121 is a perfluoroalkyl group having 1 to 5 carbon atoms), General formula (130): CF2=CFOCF2ORf 131 (In the formula, Rf 131 is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms, General formula (140): CF2=CFO(CF2CF(Y 141 )O) m (CF2) n F (In the formula, Y 141 represents a fluorine atom or a trifluoromethyl group, m is an integer of 1 to 4, and n is an integer of 1 to 4. General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151 (In the formula, Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group, or a perfluoroalkyl group. The perfluoroalkyl group may contain an etheric oxygen and a -SO2F group. n represents an integer of 0 to 3. n Y 151 may be the same or different. 152 represents a fluorine atom, a chlorine atom, or a -SO2F group. m represents an integer of 1 to 5. m Y 152 may be the same or different. 151 -SO2X 151 , -COZ 151 or -POZ 152 Z 153 represents X 151 are F, Cl, Br, I, -OR 151 or -NR 152 R 153 represents Z. 151 , Z 152 and Z 153 are the same or different and are -NR 154 R 155 -OR 156 Represents R 151 , R 152 , R 153 , R 154 , R 155 and R 156 are the same or different and represent H, ammonium, an alkali metal, an alkyl group which may contain a fluorine atom, an aryl group, or a sulfonyl-containing group. It is preferable that the material is at least one selected from the group consisting of:

[0117] In this specification, the term "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0118] The fluoromonomer represented by the general formula (110) is Rf 111 is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0119] Examples of the perfluoroorganic group in the general formula (110) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. The fluoromonomer represented by the general formula (110) further includes a fluoromonomer represented by the general formula (110) in which Rf 111 is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf 111 is the following formula:

[0120] [ka]

[0121] (wherein m represents 0 or an integer of 1 to 4), Rf 111 is the following formula:

[0122] [ka]

[0123] (wherein n represents an integer of 1 to 4).

[0124] Among the fluoromonomers represented by the general formula (110), General formula (160): CF2=CF-ORf 161 (In the formula, Rf161 Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. Fluoromonomers represented by 161 is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0125] The fluoroalkyl vinyl ether is preferably at least one selected from the group consisting of fluoromonomers represented by the general formulas (160), (130) and (140).

[0126] The fluoromonomer represented by general formula (160) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).

[0127] The fluoromonomer represented by the general formula (130) is preferably at least one selected from the group consisting of CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, and CF2=CFOCF2OCF2CF2OCF3.

[0128] The fluoromonomer represented by general formula (140) is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)O(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)3F, and CF2=CFO(CF2CF(CF3)O)2(CF2)2F.

[0129] The fluoromonomer represented by general formula (150) is preferably at least one selected from the group consisting of CF2=CFOCF2CF2SO2F, CF2=CFOCF2CF(CF3)OCF2CF2SO2F, CF2=CFOCF2CF(CF2CF2SO2F)OCF2CF2SO2F and CF2=CFOCF2CF(SO2F)2.

[0130] The fluoromonomer represented by the general formula (100) is Rf 101 is a linear fluoroalkyl group, and Rf 101 More preferred is a fluoromonomer in which Rf is a linear perfluoroalkyl group. 101 The number of carbon atoms in the formula (100) is preferably 1 to 6. Examples of the fluoromonomer represented by the formula (100) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2H, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (E-form), CHF=CHCF3 (Z-form), and the like, and among these, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0131] Fluoroalkylethylenes include: General formula (170): CH2=CH-(CF2) n -X 171 (In the formula, X 171 is H or F, and n is an integer of 3 to 10. Fluoroalkylethylenes represented by the formula: CH2=CH-C4F9 and CH2=CH-C6F 13 It is more preferable that the material is at least one selected from the group consisting of:

[0132] Examples of the fluoroalkyl allyl ether include: General formula (240): CF2=CF-CF2-ORf 111 (In the formula, Rf 111 represents a perfluoroorganic group.

[0133] Rf of general formula (240) 111 is Rf in general formula (110) 111 is the same as Rf 111is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The fluoroalkyl allyl ether represented by general formula (240) is preferably at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, more preferably at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, and even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0134] The fluorinated vinyl heterocycle includes a compound represented by the general formula (230): [ka] (In the formula, X 231 and X 232 are independently F, Cl, a methoxy group, or a fluorinated methoxy group; Y 231 is the formula Y 232 or formula Y 233 is.

[0135] [ka] (In the formula, Z 231 and Z 232 are independently F or a fluorinated alkyl group having 1 to 3 carbon atoms.

[0136] Examples of monomers that provide crosslinking sites include: General formula (180):CX 181 2=CX 182 -R f 181 CHR 181 X 183 (In the formula, X 181 and X 182 are independently a hydrogen atom, a fluorine atom, or CH3, R f 181represents a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 181 is a hydrogen atom or CH3, X 183 is an iodine atom or a bromine atom. General formula (190):CX 191 2=CX 192 -R f 191 X 193 (In the formula, X 191 and X 192 are independently a hydrogen atom, a fluorine atom, or CH3, R f 191 represents a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group, X 193 is an iodine atom or a bromine atom. General formula (200): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 201 (In the formula, m is an integer of 0 to 5, n is an integer of 1 to 3, X 201 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2I; and General formula (210): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 211 (In the formula, m is an integer of 0 to 5, n is an integer of 1 to 3, X 211 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CHOH; General formula (220):CR 221 R 222 =CR 223 -Z 221 -CR 224 =CR 225 R 226 (In the formula, R221 , R 222 , R 223 , R 224 , R 225 and R 226 are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 221 represents a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbon atoms, an at least partially fluorinated alkylene group or oxyalkylene group having 1 to 10 carbon atoms, which may have an oxygen atom, or -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p - (wherein Q is an alkylene group or an oxyalkylene group, p is 0 or 1, and m / n is 0.2 to 5), and is a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10,000. It is preferable that the material is at least one selected from the group consisting of:

[0137] X 183 and X 193 is preferably an iodine atom. f 181 and R f 191 is preferably a perfluoroalkylene group having 1 to 5 carbon atoms. 181 is preferably a hydrogen atom. 201 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH2I. 211 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH 2 OH.

[0138] Monomers that provide crosslinking sites include CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF( It is preferably at least one selected from the group consisting of CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)6CH=CH2, and CF2=CFO(CF2)5CN, and more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0139] In the above step, the fluoromonomer and a fluorine-free monomer may be polymerized. Examples of the fluorine-free monomer include hydrocarbon-based monomers reactive with the fluoromonomer. Examples of the hydrocarbon-based monomer include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, vinyl para-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, and vinyl adipate. vinyl esters such as vinyl allyl ether, vinyl acrylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; and alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester.

[0140] The fluorine-free monomer may also be a functional group-containing hydrocarbon monomer (excluding the monomer that provides a crosslinking site). Examples of the functional group-containing hydrocarbon monomer include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; fluorine-free monomers having a carboxyl group such as itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; fluorine-free monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; fluorine-free monomers having an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; and fluorine-free monomers having an amide group such as (meth)acrylamide and methylolacrylamide.

[0141] In the polymerization step, one or more of the above fluoromonomers are polymerized to obtain particles of the desired fluoropolymer.

[0142] The polymerization temperature and polymerization pressure in the above polymerization step are appropriately determined depending on the type of monomer used, the molecular weight of the desired fluoropolymer, and the reaction rate. For example, the polymerization temperature is preferably 10 to 150° C. The polymerization temperature is more preferably 30° C. or higher, and even more preferably 50° C. or higher. The polymerization temperature is more preferably 120° C. or lower, and even more preferably 100° C. or lower. The polymerization pressure is preferably 0.05 to 10 MPaG. The polymerization pressure is more preferably 0.3 MPaG or more, and even more preferably 0.5 MPaG or more. Also, it is more preferably 5.0 MPaG or less, and even more preferably 3.0 MPaG or less. In particular, from the viewpoint of improving the yield of the fluoropolymer, it is preferably 1.0 MPaG or more, more preferably 1.2 MPaG or more, even more preferably 1.5 MPaG or more, particularly preferably 1.8 MPaG or more, and particularly preferably 2.0 MPaG or more.

[0143] In the above polymerization step, the amount of carboxylic acid type hydrocarbon surfactant at the start of polymerization is preferably more than 50 ppm relative to the aqueous medium. The amount of hydrocarbon surfactant at the start of polymerization is preferably 60 ppm or more, more preferably 70 ppm or more, even more preferably 80 ppm or more, even more preferably 100 ppm or more, especially more preferably 150 ppm or more, particularly preferably 200 ppm or more, and most preferably 300 ppm or more. There is no particular upper limit, but for example, 10,000 ppm is preferable, and 5,000 ppm is more preferable. By keeping the amount of carboxylic acid type hydrocarbon surfactant at the start of polymerization within the above range, an aqueous dispersion with a smaller average primary particle size and better stability can be obtained.

[0144] Polymerization can be said to have begun when the gaseous fluoromonomer in the reactor becomes a fluoropolymer and a pressure drop occurs in the reactor. U.S. Patent No. 3,391,099 (Punderson) discloses dispersion polymerization of tetrafluoroethylene in an aqueous medium, which consists of two distinct stages of the polymerization process: first, the formation of polymer nuclei as nucleation sites, and then, the growth stage, which involves the polymerization of the established particles. Note that polymerization usually begins when both the monomer to be polymerized and the polymerization initiator are charged into the reactor. In this disclosure, the additive involved in the formation of nucleation sites is referred to as a nucleating agent.

[0145] The polymerization step is a step of polymerizing a fluoromonomer such as tetrafluoroethylene in an aqueous medium in the presence of a carboxylic acid type hydrocarbon surfactant, and it is also preferable that the step includes a step of continuously adding the carboxylic acid type hydrocarbon surfactant. Continuous addition of the carboxylic acid type hydrocarbon surfactant means, for example, adding the carboxylic acid type hydrocarbon surfactant not all at once but over time, either continuously or in portions. In the polymerization step, the step of continuously adding the carboxylic acid hydrocarbon surfactant preferably starts adding the carboxylic acid hydrocarbon surfactant to the aqueous medium when the concentration of the fluoropolymer formed in the aqueous medium is less than 0.60% by mass. The addition of the carboxylic acid hydrocarbon surfactant is more preferably started when the concentration is 0.50% by mass or less, even more preferably when it is 0.36% by mass or less, even more preferably when it is 0.30% by mass or less, even more preferably when it is 0.20% by mass or less, and even more preferably when it is 0.10% by mass or less, and most preferably when the polymerization starts. The above concentrations are relative to the total concentration of the aqueous medium and the fluoropolymer. By including the above step, an aqueous dispersion having a smaller average primary particle size and superior stability can be obtained.

[0146] In the step of continuously adding the carboxylic acid type hydrocarbon surfactant, the amount of the carboxylic acid type hydrocarbon surfactant added is preferably 0.01 to 10% by mass relative to 100% by mass of the aqueous medium, more preferably 0.05% by mass at the lower limit, even more preferably 0.1% by mass at the lower limit, more preferably 5% by mass at the upper limit, and even more preferably 1% by mass at the upper limit.

[0147] In the step of carrying out emulsion polymerization of a fluoromonomer in an aqueous medium in the presence of the carboxylic acid type hydrocarbon surfactant, the amount of the carboxylic acid type hydrocarbon surfactant is preferably large, and is preferably 0.01 to 10 mass% relative to 100 mass% of the aqueous medium. A more preferred lower limit is 0.1 mass% and a more preferred upper limit is 1 mass%.

[0148] The carboxylic acid type hydrocarbon surfactant is usually an anionic surfactant having a hydrophilic portion of a carboxylate salt and a hydrophobic portion which is a long-chain hydrocarbon portion such as an alkyl group. The carboxylic acid type hydrocarbon surfactant may be an aliphatic carboxylic acid type hydrocarbon surfactant, or may be a non-aliphatic carboxylic acid type hydrocarbon surfactant. In this specification, "aliphatic carboxylic acid hydrocarbon surfactant" refers to a carboxylic acid hydrocarbon surfactant that does not contain a carbonyl group (excluding the carbonyl groups in carboxyl groups and ester groups). The ester group refers to a group represented by -COO- or -OCO-.

[0149] Examples of the carboxylic acid type hydrocarbon surfactant include those represented by the following formula: R 10 -COOM (In the formula, R 10 is a monovalent organic group containing one or more carbon atoms. M is H, a metal atom, NR 11 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 11 R is H or an organic group, and may be the same or different. 11 as H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferred. From the viewpoint of surfactant activity, R 10 The number of carbon atoms in R is preferably 2 or more, and more preferably 3 or more. 10 The number of carbon atoms is preferably 29 or less, and more preferably 23 or less. The metal atom of M includes alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferred. M is H, a metal atom, or NR 11 4 is preferred, H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 11 4 is more preferred, H, Na, K, Li or NH4 is even more preferred, Na, K or NH4 is even more preferred, Na or NH4 is particularly preferred, and NH4 is most preferred.

[0150] The carboxylic acid type hydrocarbon surfactants include R 12 -COOM(in the formula, R 12 is a linear or branched alkyl group, alkenyl group, alkylene group or alkenylene group having 1 or more carbon atoms which may have a substituent, or a cyclic alkyl group, alkenyl group, alkylene group or alkenylene group having 3 or more carbon atoms which may have a substituent, and these may contain an ether bond. When the number of carbon atoms is 3 or more, it may contain a monovalent or divalent heterocycle or may form a ring. M is the same as above.) Specifically, CH3-(CH2) n -COOM (wherein n is an integer of 2 to 28, and M is the same as above).

[0151] From the viewpoint of emulsion stability, the carboxylic acid type hydrocarbon surfactant preferably does not contain a carbonyl group (excluding the carbonyl group in the carboxyl group). The surfactant used in the polymerization is preferably a carboxylic acid type hydrocarbon surfactant that does not contain a carbonyl group. Examples of the carboxylic acid type hydrocarbon surfactant not containing a carbonyl group include those represented by the following formula (α): R-COO-M (α) (In the formula, R is an alkyl group, an alkenyl group, an alkylene group, or an alkenylene group, which may contain an ether bond. M is H, a metal atom, NR 11 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 11 are the same or different and are H or an organic group having 1 to 10 carbon atoms. In the above formula (α), R is preferably an alkyl group or an alkenyl group (which may contain an ether group). The alkyl group or alkenyl group in R may be linear or branched. The number of carbon atoms in R is not limited, but is, for example, 2 to 29. The alkyl group or alkenyl group in R preferably does not contain a carbonyl group (excluding the carbonyl group in an ester group).

[0152] When the alkyl group is linear, the carbon number of R is preferably 3 to 29, and more preferably 5 to 23. When the alkyl group is branched, the carbon number of R is preferably 5 to 35, and more preferably 11 to 23. When the alkenyl group is linear, the number of carbon atoms in R is preferably 2 to 29, more preferably 9 to 23. When the alkenyl group is branched, the number of carbon atoms in R is preferably 2 to 29, more preferably 3 to 29, and even more preferably 9 to 23.

[0153] Examples of the alkyl group and alkenyl group include a methyl group, an ethyl group, an isobutyl group, a t-butyl group, and a vinyl group.

[0154] Examples of the carboxylic acid type hydrocarbon surfactants include butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, (9,12,15)-linolenic acid, (6,9,12)linolenic acid, eleostearic acid, arachidic acid, 8,11-eicosadienoic acid, mead acid, arachidonic acid, behenic acid, lignoceric acid, nervonic acid, cerotic acid, montanic acid, melissic acid, crotonic acid, milian acid, malianthic ... Examples of the fatty acids include stearic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonic acid, linoleic acid, eicosadienoic acid, docosadienoic acid, linolenic acid, pinolenic acid, α-eleostearic acid, β-eleostearic acid, mead acid, dihomo-γ-linolenic acid, eicosatrienoic acid, stearidonic acid, arachidonic acid, eicosatetraenoic acid, adrenic acid, bosseopentaenoic acid, eicosapentaenoic acid, osbondo acid, sardine acid, tetracosapentaenoic acid, docosahexaenoic acid, herring acid, and salts thereof. In particular, at least one selected from the group consisting of lauric acid, capric acid, myristic acid, pentadecylic acid, palmitic acid, and salts thereof is preferred, lauric acid and salts thereof are more preferred, salts of lauric acid are particularly preferred, and sodium laurate or ammonium laurate is most preferred. The salts include those in which the hydrogen of the carboxyl group is replaced by a metal atom of the formula M, NR 11 4. Examples include, but are not limited to, imidazolium which may have a substituent, pyridinium which may have a substituent, or phosphonium which may have a substituent.

[0155] Examples of the carboxylic acid type hydrocarbon surfactant include those represented by the following formula (a): [ka] (In the formula, R 1aR is a linear or branched alkyl group having 1 or more carbon atoms or a cyclic alkyl group having 3 or more carbon atoms, in which a hydrogen atom bonded to a carbon atom may be substituted with a monovalent organic group containing a hydroxy group or an ester bond, and when it has 2 or more carbon atoms, it may contain a carbonyl group, and when it has 3 or more carbon atoms, it may contain a monovalent or divalent heterocycle or form a ring. 2a and R 3a R is independently a single bond or a divalent linking group. 1a , R 2a and R 3a A has a total of 5 or more carbon atoms. a -COOX a (X a is H, metal atom, NR 4a 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 4a are H or organic groups, and may be the same or different. 1a , R 2a and R 3a Any two of the groups may be bonded to each other to form a ring.) and a surfactant (a) represented by the following formula (b): [ka] (In the formula, R 1b R is a linear or branched alkyl group having 1 or more carbon atoms which may have a substituent, or a cyclic alkyl group having 3 or more carbon atoms which may have a substituent, and when the alkyl group has 3 or more carbon atoms, it may contain a monovalent or divalent heterocycle or form a ring. 2b and R 4b are independently H or a substituent. 3b is an alkylene group having 1 to 10 carbon atoms which may have a substituent. n is an integer of 1 or more. p and q are independently integers of 0 or more. A b -COOX b (X b is H, metal atom, NR 5b4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 5b are H or organic groups, and may be the same or different. 1b , R 2b , R 3b and R 4b Any two of may be bonded to each other to form a ring. L is a single bond, -CO2-B-*, -OCO-B-*, -CONR 6b -B-*, -NR 6b CO-B-* or -CO- (However, -CO2-B-, -OCO-B-, -CONR 6b -B-, -NR 6b The carbonyl group contained in CO-B- is excluded.) B is a single bond or an alkylene group having 1 to 10 carbon atoms which may have a substituent, and R 6b is H or an alkyl group having 1 to 4 carbon atoms which may have a substituent. * represents A in the formula. b The surfactant (b) may be at least one selected from the group consisting of surfactants (b) represented by the formula:

[0156] The surfactant (a) will now be described.

[0157] In formula (a), R 1a is a linear or branched alkyl group having 1 or more carbon atoms or a cyclic alkyl group having 3 or more carbon atoms. When the alkyl group has three or more carbon atoms, it may contain a carbonyl group (-C(=O)-) between two carbon atoms. When the alkyl group has two or more carbon atoms, it may also contain the carbonyl group at the terminal of the alkyl group. In other words, acyl groups such as an acetyl group represented by CH3-C(=O)- are also included in the alkyl group. Furthermore, when the alkyl group has 3 or more carbon atoms, it may contain a monovalent or divalent heterocyclic ring, or may be a ring. The heterocyclic ring is preferably an unsaturated heterocyclic ring, more preferably an oxygen-containing unsaturated heterocyclic ring, such as a furan ring. R 1aIn the above, a divalent heterocycle may be inserted between two carbon atoms, a divalent heterocycle may be located at a terminal and bonded to -C(=O)-, or a monovalent heterocycle may be located at the terminal of the alkyl group.

[0158] In this specification, the "number of carbon atoms" of the alkyl group includes the number of carbon atoms constituting the carbonyl group and the number of carbon atoms constituting the heterocycle. For example, a group represented by CH3-C(=O)-CH2- has 3 carbon atoms, a group represented by CH3-C(=O)-C2H4-C(=O)-C2H4- has 7 carbon atoms, and a group represented by CH3-C(=O)- has 2 carbon atoms.

[0159] In the alkyl group, a hydrogen atom bonded to a carbon atom may be substituted with a functional group, for example, with a hydroxy group (—OH) or a monovalent organic group containing an ester bond, but it is preferable that the alkyl group is not substituted with any functional group. The monovalent organic group containing an ester bond is a group represented by the formula: -OC(=O)-R 101a (In the formula, R 101a is an alkyl group). The alkyl group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0160] In formula (a), R 2a and R 3a are independently a single bond or a divalent linking group. R 2a and R 3a are preferably independently a single bond, a linear or branched alkylene group having 1 or more carbon atoms, or a cyclic alkylene group having 3 or more carbon atoms. R 2a and R 3a The alkylene group constituting the formula (I) preferably does not contain a carbonyl group.

[0161] In the alkylene group, a hydrogen atom bonded to a carbon atom may be substituted with a functional group, for example, with a hydroxy group (—OH) or a monovalent organic group containing an ester bond, but it is preferable that the alkylene group is not substituted with any functional group. The monovalent organic group containing an ester bond is a group represented by the formula: -OC(=O)-R 102a (In the formula, R 102a is an alkyl group). The alkylene group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkylene group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0162] R 1a , R 2a and R 3a has a total carbon number of 5 or more. The total carbon number is preferably 7 or more, more preferably 9 or more, and is preferably 20 or less, more preferably 18 or less, and even more preferably 15 or less. R 1a , R 2a and R 3a Any two of these may be bonded to each other to form a ring.

[0163] In formula (a), in formula, A a -COOX a (X a is H, metal atom, NR 4a 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 4a are H or organic groups, and may be the same or different. 4ais preferably H or an organic group having 1 to 10 carbon atoms, more preferably H or an organic group having 1 to 4 carbon atoms. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K, or Li. X a H, alkali metals (group 1), alkaline earth metals (group 2) or NR 4a X is preferred, H, Na, K, Li or NH is more preferred because they are easily soluble in water, Na, K or NH is even more preferred because they are even more easily soluble in water, Na or NH is particularly preferred, and NH is most preferred because it is easily removed. a When is NH4, the surfactant has excellent solubility in an aqueous medium, and metal components are less likely to remain in the fluoropolymer or the final product.

[0164] R 1a As the alkyl group, a linear or branched alkyl group having 1 to 8 carbon atoms and not containing a carbonyl group, a cyclic alkyl group having 3 to 8 carbon atoms and not containing a carbonyl group, a linear or branched alkyl group having 2 to 45 carbon atoms and containing 1 to 10 carbonyl groups, a cyclic alkyl group having 3 to 45 carbon atoms and containing a carbonyl group, or an alkyl group containing a monovalent or divalent heterocycle having 3 to 45 carbon atoms is preferred.

[0165] Also, R 1a As the formula: [ka] (In the formula, n 11a is an integer between 0 and 10, and R 11a is a linear or branched alkyl group having 1 to 5 carbon atoms or a cyclic alkyl group having 3 to 5 carbon atoms, and R 12a is an alkylene group having 0 to 3 carbon atoms. 11a is an integer between 2 and 10, R 12a may be the same or different. ) is more preferred.

[0166] n 11ais preferably an integer of 0 to 5, more preferably an integer of 0 to 3, and even more preferably an integer of 1 to 3.

[0167] R 11a The alkyl group as above preferably does not contain a carbonyl group. R 11a In the alkyl group as above, a hydrogen atom bonded to a carbon atom may be substituted with a functional group, for example, a hydroxy group (—OH) or a monovalent organic group containing an ester bond, but it is preferable that the alkyl group is not substituted with any functional group. The monovalent organic group containing an ester bond is a group represented by the formula: -OC(=O)-R 103a (In the formula, R 103a is an alkyl group). R 11a The alkyl group as above may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0168] R 12a is an alkylene group having 0 to 3 carbon atoms. The number of carbon atoms is preferably 1 to 3. R 12a The alkylene group as may be linear or branched. R 12a The alkylene group as R preferably does not contain a carbonyl group. 12a As the alkyl group, an ethylene group (-C2H4-) or a propylene group (-C3H6-) is more preferred. R 12a In the alkylene group as above, a hydrogen atom bonded to a carbon atom may be substituted with a functional group, for example, a hydroxy group (—OH) or a monovalent organic group containing an ester bond, but it is preferable that the alkylene group is not substituted with any functional group. The monovalent organic group containing an ester bond is a group represented by the formula: -OC(=O)-R 104a (In the formula, R 104a is an alkyl group). R 12a The alkylene group as above may have 75% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, 50% or less of the hydrogen atoms substituted with halogen atoms, or 25% or less of the hydrogen atoms substituted with halogen atoms, but is preferably a non-halogenated alkylene group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0169] R 2a and R 3a are each independently preferably an alkylene group having 1 or more carbon atoms and not containing a carbonyl group, more preferably an alkylene group having 1 to 3 carbon atoms and not containing a carbonyl group, and further preferably an ethylene group (-C2H4-) or a propylene group (-C3H6-).

[0170] Next, the surfactant (b) will be described.

[0171] In formula (b), R 1b is a linear or branched alkyl group having 1 or more carbon atoms which may have a substituent, or a cyclic alkyl group having 3 or more carbon atoms which may have a substituent. When the alkyl group has 3 or more carbon atoms, it may contain a monovalent or divalent heterocyclic ring, or may be a ring. The heterocyclic ring is preferably an unsaturated heterocyclic ring, more preferably an oxygen-containing unsaturated heterocyclic ring, such as a furan ring. R 1b In the above, a divalent heterocycle may be inserted between two carbon atoms, a divalent heterocycle may be located at a terminal and bonded to -C(=O)-, or a monovalent heterocycle may be located at the terminal of the alkyl group.

[0172] In this specification, the "number of carbon atoms" of the alkyl group includes the number of carbon atoms constituting the heterocycle.

[0173] R 1bThe substituent that the alkyl group may have is preferably a halogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group having 3 to 10 carbon atoms, or a hydroxy group, and particularly preferably a methyl group or an ethyl group.

[0174] R 1b The alkyl group as above preferably does not contain a carbonyl group. The alkyl group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms. The alkyl group preferably does not have any substituents.

[0175] R 1b As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent or a cyclic alkyl group having 3 to 10 carbon atoms which may have a substituent is preferred, a linear or branched alkyl group having 1 to 10 carbon atoms which does not contain a carbonyl group or a cyclic alkyl group having 3 to 10 carbon atoms which does not contain a carbonyl group is more preferred, a linear or branched alkyl group having 1 to 10 carbon atoms which does not contain a substituent is even more preferred, a linear or branched alkyl group having 1 to 3 carbon atoms which does not contain a substituent is even more preferred, a methyl group (-CH3) or an ethyl group (-C2H5) is particularly preferred, and a methyl group (-CH3) is most preferred.

[0176] In formula (b), R 2b and R 4b are independently H or a substituent. 2b and R 4b may be the same or different.

[0177] R 2b and R 4bThe substituent as is preferably a halogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group having 3 to 10 carbon atoms, or a hydroxy group, and particularly preferably a methyl group or an ethyl group.

[0178] R 2b and R 4b The alkyl group as the alkyl group preferably does not contain a carbonyl group. The alkyl group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms. The alkyl group preferably does not have any substituents.

[0179] R 2b and R 4b The alkyl group as the alkyl group is preferably a linear or branched alkyl group having 1 to 10 carbon atoms and not containing a carbonyl group, or a cyclic alkyl group having 3 to 10 carbon atoms and not containing a carbonyl group, more preferably a linear or branched alkyl group having 1 to 10 carbon atoms and not containing a carbonyl group, even more preferably a linear or branched alkyl group having 1 to 3 carbon atoms and not containing a substituent, and particularly preferably a methyl group (-CH3) or an ethyl group (-C2H5).

[0180] R 2b and R 4b are each independently preferably H or a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms and not containing a carbonyl group, more preferably H or a straight-chain or branched-chain alkyl group having 1 to 3 carbon atoms and not containing a substituent, even more preferably H, a methyl group (-CH3), or an ethyl group (-C2H5), and particularly preferably H.

[0181] In formula (b), R 3b R is an alkylene group having 1 to 10 carbon atoms which may have a substituent. 3b When there are a plurality of, they may be the same or different.

[0182] The alkylene group preferably does not contain a carbonyl group. The alkylene group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms. The alkylene group preferably does not have any substituents.

[0183] The alkylene group is preferably a linear or branched alkylene group having 1 to 10 carbon atoms which may have a substituent, or a cyclic alkylene group having 3 to 10 carbon atoms which may have a substituent, more preferably a linear or branched alkylene group having 1 to 10 carbon atoms which does not contain a carbonyl group, or a cyclic alkylene group having 3 to 10 carbon atoms which does not contain a carbonyl group, more preferably a linear or branched alkylene group having 1 to 10 carbon atoms which does not have a substituent, and still more preferably a methylene group (-CH2-), an ethylene group (-C2H4-), an isopropylene group (-CH(CH3)CH2-) or a propylene group (-C3H6-).

[0184] R 1b , R 2b , R 3b and R 4b Any two of these may be bonded to each other to form a ring.

[0185] In formula (b), n is an integer of 1 or greater. n is preferably an integer of 1 to 40, more preferably an integer of 1 to 30, and even more preferably an integer of 5 to 25.

[0186] In formula (b), p and q are independently an integer of 0 or greater. p is preferably an integer of 0 to 10, more preferably 0 or 1. q is preferably an integer of 0 to 10, more preferably an integer of 0 to 5.

[0187] The sum of n, p, and q is preferably an integer of 6 or greater. The sum of n, p, and q is more preferably an integer of 8 or greater. The sum of n, p, and q is also preferably an integer of 60 or less, more preferably an integer of 50 or less, and even more preferably an integer of 40 or less.

[0188] In formula (b), A b -COOX b (X b is H, metal atom, NR 5b 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 5b are H or organic groups, and may be the same or different. 5b is preferably H or an organic group having 1 to 10 carbon atoms, more preferably H or an organic group having 1 to 4 carbon atoms. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K, or Li. X b is a metal atom or NR 5b 4(R 5b is as above). X b H, alkali metals (group 1), alkaline earth metals (group 2) or NR 5b X is preferred, H, Na, K, Li or NH is more preferred because they are easily soluble in water, Na, K or NH is even more preferred because they are even more easily soluble in water, Na or NH is particularly preferred, and NH is most preferred because it is easily removed. b When is NH4, the surfactant has excellent solubility in an aqueous medium, and metal components are less likely to remain in the fluoropolymer or the final product.

[0189] In formula (b), L is a single bond, -CO2-B-*, -OCO-B-*, or -CONR 6b -B-*, -NR 6b CO-B-* or -CO- (However, -CO2-B-, -OCO-B-, -CONR 6b -B-, -NR 6bThe carbonyl group contained in CO-B- is excluded.) B is a single bond or an alkylene group having 1 to 10 carbon atoms which may have a substituent, and R 6b is H or an alkyl group having 1 to 4 carbon atoms which may have a substituent. The alkylene group more preferably has 1 to 5 carbon atoms. 6b is more preferably H or a methyl group. b This refers to the side that binds to the

[0190] L is preferably a single bond.

[0191] The surfactant is 1 In the 1 H-NMR spectrum, the integral value of all peak intensities observed in the chemical shift region of 2.0 to 5.0 ppm is preferably 10% or more.

[0192] The surfactant is 1 In the H-NMR spectrum, the integrated value of all peak intensities observed in the chemical shift region of 2.0 to 5.0 ppm is preferably within the above range. In this case, the surfactant preferably has a ketone structure in the molecule.

[0193] In the surfactant, the integral value is more preferably 15 or more, and is preferably 95 or less, more preferably 80 or less, and even more preferably 70 or less.

[0194] The above integral value is measured at room temperature in a heavy water solvent. Heavy water is 4.79 ppm.

[0195] Furthermore, as the carboxylic acid type hydrocarbon surfactant in the present disclosure, a compound represented by general formula (1-0) (hereinafter also referred to as "surfactant (1-0)") can also be used. General formula (1-0): [ka] (In the formula, R 1 ~R 5 represents H or a monovalent substituent, provided that R1 and R 3 At least one of the groups has the general formula: -YR 6 a group represented by R 2 and R 5 At least one of the groups represented by the general formula: -XA or -YR 6 represents a group represented by the following formula: Furthermore, X, in each occurrence, is the same or different and represents a divalent linking group or a bond; A is the same or different in each occurrence and is -COOM (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 is H or an organic group); Y may be the same or different in each occurrence and may be -S(=O)2-, -O-, -COO-, -OCO-, -CONR 8 - and -NR 8 a divalent linking group selected from the group consisting of CO—, or a bond, R 8 is H or an organic group; R 6 represents, the same or different in each occurrence, an alkyl group having one or more carbon atoms which may contain at least one group selected from the group consisting of a carbonyl group, an ester group, an amide group and a sulfonyl group between carbon atoms; R 1 ~R 5 Any two of these may be bonded to each other to form a ring. However, R 6 does not contain any of a carbonyl group, an ester group, an amide group, and a sulfonyl group, X is a divalent linking group containing at least one group selected from the group consisting of a carbonyl group, an ester group, an amide group, and a sulfonyl group.

[0196] In the formula, R 1 ~R 5 represents H or a monovalent substituent, provided that R 1 and R 3 At least one of the groups has the general formula: -YR 6 a group represented by R 2and R 5 At least one of the groups represented by the general formula: -XA or -YR 6 R represents a group represented by 1 ~R 5 Any two of these may be bonded to each other to form a ring.

[0197] R 1 The substituent that the alkyl group may have is preferably a halogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group having 3 to 10 carbon atoms, or a hydroxy group, and particularly preferably a methyl group or an ethyl group.

[0198] R 1 The alkyl group as above preferably does not contain a carbonyl group. The alkyl group may have 75% or less, 50% or less, or 25% or less of the hydrogen atoms bonded to carbon atoms substituted with halogen atoms, but is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms. The alkyl group preferably does not have any substituents.

[0199] R 1 As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent or a cyclic alkyl group having 3 to 10 carbon atoms which may have a substituent is preferred, a linear or branched alkyl group having 1 to 10 carbon atoms which does not contain a carbonyl group or a cyclic alkyl group having 3 to 10 carbon atoms which does not contain a carbonyl group is more preferred, a linear or branched alkyl group having 1 to 10 carbon atoms which does not contain a substituent is even more preferred, a linear or branched alkyl group having 1 to 3 carbon atoms which does not contain a substituent is even more preferred, a methyl group (-CH3) or an ethyl group (-C2H5) is particularly preferred, and a methyl group (-CH3) is most preferred.

[0200] The monovalent substituent includes a group represented by the general formula: -YR 6a group represented by the general formula: -XA; -H; optionally substituted C 1-20 Alkyl groups, -NH2, -NHR 9 (R 9 is an organic group), -OH, -COOR 9 (R 9 is an organic group) or -OR 9 (R 9 is an organic group), the alkyl group preferably has 1 to 10 carbon atoms.

[0201] R 9 As for C 1-10 or C 1-10 The alkylcarbonyl group of C is preferred. 1-4 or C 1-4 An alkylcarbonyl group of the formula is more preferred.

[0202] In the formula, X may be the same or different in each occurrence and represents a divalent linking group or bond. R 6 When X does not contain any of a carbonyl group, an ester group, an amide group, and a sulfonyl group, X is preferably a divalent linking group containing at least one group selected from the group consisting of a carbonyl group, an ester group, an amide group, and a sulfonyl group.

[0203] X may be -CO-, -S(=O)2-, -O-, -COO-, -OCO-, -S(=O)2-O-, -OS(=O)2-, or -CONR 8 - and -NR 8 a divalent linking group containing at least one bond selected from the group consisting of CO—, C 1-10 An alkylene group or a bond represented by the formula R 8 represents H or an organic group.

[0204] R 8 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferred, and H is even more preferred.

[0205] In the formula, A is the same or different in each occurrence and is —COOM (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 is H or an organic group. 7 may be the same or different.

[0206] R 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferred. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li.

[0207] M is H, a metal atom, or NR 7 4 is preferred, H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 7 4 is more preferred, H, Na, K, Li or NH4 is even more preferred, Na, K or NH4 is even more preferred, Na or NH4 is particularly preferred, and NH4 is most preferred.

[0208] In the formula, Y may be the same or different in each occurrence and may be -S(=O)2-, -O-, -COO-, -OCO-, -CONR 8 - and -NR 8 a divalent linking group selected from the group consisting of CO—, or a bond, R 8 represents H or an organic group.

[0209] Y is a bond, -O-, -COO-, -OCO-, -CONR 8 - and -NR 8 A divalent linking group selected from the group consisting of -CO- is preferred, and a divalent linking group selected from the group consisting of a bond, -COO-, and -OCO- is more preferred.

[0210] R 8 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4The organic group is more preferred, and H is even more preferred.

[0211] In the formula, R 6 In each occurrence, R may be the same or different and represent an alkyl group having one or more carbon atoms which may contain at least one group selected from the group consisting of a carbonyl group, an ester group, an amide group and a sulfonyl group between carbon atoms. 6 The organic group preferably has 2 or more carbon atoms and 20 or less carbon atoms, more preferably 2 to 20 carbon atoms, and even more preferably 2 to 10 carbon atoms.

[0212] R 6 When the alkyl group of R has two or more carbon atoms, it may contain one or more groups selected from the group consisting of a carbonyl group, an ester group, an amide group, and a sulfonyl group between carbon atoms, but does not contain these groups at both ends of the alkyl group. 6 In the alkyl group, 75% or less of the hydrogen atoms bonded to carbon atoms may be substituted with halogen atoms, 50% or less may be substituted with halogen atoms, or 25% or less may be substituted with halogen atoms, but it is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0213] R 6 As for General formula:-R 10 -CO-R 11 a group represented by General formula:-R 10 -COO-R 11 a group represented by General formula:-R 11 a group represented by General formula:-R 10 -NR 8 CO-R 11 or a group represented by General formula:-R 10 -CONR 8 -R 11 a group represented by (In the formula, R 8 represents H or an organic group. 10 is an alkylene group, R11 is preferably an alkyl group which may have a substituent. R 6 As the general formula: -R 10 -CO-R 11 A group represented by the following formula is more preferred.

[0214] R 8 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferred, and H is even more preferred.

[0215] R 10 The number of carbon atoms in the alkylene group of R is preferably 1 or more, more preferably 3 or more, and is preferably 20 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 8 or less. 10 The alkylene group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 3 to 10 carbon atoms.

[0216] R 11 The number of carbon atoms in the alkyl group may be 1 to 20, preferably 1 to 15, more preferably 1 to 12, even more preferably 1 to 10, even more preferably 1 to 8, particularly preferably 1 to 6, even more preferably 1 to 3, particularly preferably 1 or 2, and most preferably 1. 11 The alkyl group of R is preferably composed of only primary, secondary, and tertiary carbon atoms, and particularly preferably composed of only primary and secondary carbon atoms. 11 As the alkyl group, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group is preferred, and a methyl group is most preferred.

[0217] The surfactant (1) is preferably a compound represented by general formula (1-1), a compound represented by general formula (1-2), or a compound represented by general formula (1-3), and more preferably a compound represented by general formula (1-1) or a compound represented by general formula (1-2).

[0218] General formula (1-1): [ka] (In the formula, R 3 ~R 6 , X, A and Y are as above.)

[0219] General formula (1-2): [ka] (In the formula, R 4 ~R 6 , X, A and Y are as above.)

[0220] General formula (1-3): [ka] (In the formula, R 2 , R 4 ~R 6 , X, A and Y are as above.)

[0221] Examples of the group represented by the general formula -XA include: -COOM, -R 12 COOM, -OCO-R 12 -COOM, -COO-R 12 -COOM, -CONR 8 -R 12 -COOM, -NR 8 CO-R 12 -COOM, -OS(=O)2-R 12 -COOM, (In the formula, R 8 and M are as above. 12 is C 1-10 An alkylene group represented by the formula: is preferred. Above R 12In the alkylene group, 75% or less of the hydrogen atoms bonded to carbon atoms may be substituted with halogen atoms, 50% or less may be substituted with halogen atoms, or 25% or less may be substituted with halogen atoms, but it is preferably a non-halogenated alkylene group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0222] General formula:-YR 6 Examples of the group represented by the formula: General formula:-R 10 -CO-R 11 a group represented by General formula:-OCO-R 10 -CO-R 11 a group represented by General formula:-COO-R 10 -CO-R 11 a group represented by General formula:-OCO-R 10 -COO-R 11 a group represented by General formula:-COO-R 11 a group represented by General formula:-NR 8 CO-R 10 -CO-R 11 or a group represented by General formula:-CONR 8 -R 10 -NR 8 CO-R 11 A group represented by (In the formula, R 8 , R 10 and R 11 is as described above.) is preferred.

[0223] In the formula, R 4 and R 5 are independently H or C 1-4 The alkyl groups are preferably: Above R 4 and R 5In the alkyl group, 75% or less of the hydrogen atoms bonded to carbon atoms may be substituted with halogen atoms, 50% or less may be substituted with halogen atoms, or 25% or less may be substituted with halogen atoms, but it is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0224] R in general formula (1-1) 3 is H or optionally substituted C 1-20 The alkyl group is preferably H or unsubstituted C 1-20 An alkyl group represented by the formula (I) is more preferred, and H is even more preferred. Above R 3 In the alkyl group, 75% or less of the hydrogen atoms bonded to carbon atoms may be substituted with halogen atoms, 50% or less may be substituted with halogen atoms, or 25% or less may be substituted with halogen atoms, but it is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0225] R in general formula (1-3) 2 is H, OH or optionally substituted C 1-20 The alkyl group having no H, OH or substituent is preferably C 1-20 An alkyl group such as the above is more preferred, and H or OH is even more preferred. Above R 2 In the alkyl group, 75% or less of the hydrogen atoms bonded to carbon atoms may be substituted with halogen atoms, 50% or less may be substituted with halogen atoms, or 25% or less may be substituted with halogen atoms, but it is preferably a non-halogenated alkyl group that does not contain halogen atoms such as fluorine atoms or chlorine atoms.

[0226] Among the above-mentioned carboxylic acid type hydrocarbon surfactants, the aliphatic carboxylic acid type hydrocarbon surfactants include surfactants represented by the above-mentioned formula (α), surfactants represented by the following formula (1-0A): [ka] (In the formula, R 1A ~R 5A represents H, a monovalent hydrocarbon group which may contain an ester group between carbon atoms, or a group represented by the general formula: -X A -A, where R 2A and R 5A At least one of the groups has the general formula: -X A - represents a group represented by A. X A is, in each occurrence, the same or different, a divalent hydrocarbon radical or a bond; A is the same or different in each occurrence and is -COOM (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 is H or an organic group); R 1A ~R 5A Any two of these may be bonded to each other to form a ring.

[0227] In general formula (1-0A), R 1A ~R 5A In R, the monovalent hydrocarbon group which may contain an ester group between carbon atoms preferably has 1 to 50 carbon atoms, and more preferably has 5 to 20 carbon atoms. 1A ~R 5A The hydrocarbon group in R does not include a carbonyl group (excluding the carbonyl group in a carboxyl group or an ester group). 1A ~R 5A Any two of these may be bonded to each other to form a ring. The monovalent hydrocarbon group which may contain an ester group between carbon atoms is preferably an alkyl group. In the formula, X A In the formula, the divalent hydrocarbon group preferably has 1 to 50 carbon atoms, and more preferably 5 to 20 carbon atoms. A The hydrocarbon group does not include a carbonyl group. Examples of the divalent hydrocarbon group include an alkylene group and an alkanediyl group, with an alkylene group being preferred.

[0228] In general formula (1-0A), R 2A and R 5A any one of the above general formula: -X A -A is preferred, and R 2A is represented by the above general formula: -X A A group represented by -A is more preferred.

[0229] In the general formula (1-0A), a preferred embodiment is R 2A is represented by the general formula: -X A -A, and R 1A , R 3A , R 4A and R 5A is H. In this case, X A is preferably a bond or an alkylene group having 1 to 5 carbon atoms.

[0230] In the general formula (1-0A), a preferred embodiment is also R 2A is represented by the general formula: -X A -A, and R 1A and R 3A Ga-Y A -R 6 and Y A are the same or different in each occurrence and are -COO-, -OCO-, or a bond; R 6 In this embodiment, R is the same or different in each occurrence and is an alkyl group having 1 or more carbon atoms. 4A and R 5A is preferably H.

[0231] Examples of the aliphatic carboxylic acid hydrocarbon surfactant represented by general formula (1-0A) include glutaric acid or a salt thereof, adipic acid or a salt thereof, pimelic acid or a salt thereof, suberic acid or a salt thereof, azelaic acid or a salt thereof, and sebacic acid or a salt thereof. Furthermore, the aliphatic carboxylic acid hydrocarbon surfactant represented by general formula (1-0A) may be a two-chain two-hydrophilic group synthetic surfactant, and examples of such Gemini surfactants include Geminisurf (Chukyo Yushi Co., Ltd.), Gemsurf α142 (12 carbon atoms, lauryl group), Gemsurf α102 (10 carbon atoms), and Gemsurf α182 (14 carbon atoms).

[0232] The production method of the present disclosure may include a step of performing radical treatment or oxidation treatment on the carboxylic acid type hydrocarbon surfactant (in the second production method, an aliphatic carboxylic acid type hydrocarbon surfactant) before the above polymerization step. The radical treatment may be any treatment that generates radicals in the carboxylic acid hydrocarbon surfactant. For example, deionized water and a carboxylic acid hydrocarbon surfactant are added to a reactor, the reactor is sealed, the system is purged with nitrogen, the reactor is heated and pressurized, a polymerization initiator is added, the mixture is stirred for a certain period of time, the reactor is depressurized to atmospheric pressure, and then cooled. The oxidation treatment is a treatment in which an oxidizing agent is added to the carboxylic acid hydrocarbon surfactant. Examples of oxidizing agents include oxygen, ozone, hydrogen peroxide, manganese (IV) oxide, potassium permanganate, potassium dichromate, nitric acid, and sulfur dioxide. To promote the radical treatment or oxidation treatment, the radical treatment or oxidation treatment may be carried out in an aqueous solution with an adjusted pH. The pH of the aqueous solution used for the radical treatment or oxidation treatment is preferably less than 7. The pH of the aqueous solution can be adjusted using, for example, sulfuric acid, nitric acid, or hydrochloric acid.

[0233] In the production method of the present disclosure, the polymerization step may further include a step of adjusting the pH of the aqueous medium containing the carboxylic acid hydrocarbon surfactant (in the second production method, an aliphatic carboxylic acid hydrocarbon surfactant) to a basic pH. The basic pH is preferably 7.1 or higher, more preferably 7.5 or higher, even more preferably 8.0 or higher, particularly preferably 8.5 or higher, and even more preferably 9.0 or higher. By adjusting the pH to a basic pH, the surfactant ability can be enhanced. The pH adjustment step may be performed before or after the step of performing radical treatment or oxidation treatment on the carboxylic acid hydrocarbon surfactant, but is preferably performed after the step. The method for adjusting the pH is not particularly limited, and examples include a method of adding a pH adjuster to the aqueous medium. Examples of the pH adjuster that can be used include ammonia, NaOH, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium phosphate, potassium phosphate, sodium citrate, potassium citrate, ammonium citrate, sodium gluconate, potassium gluconate, and ammonium gluconate. The pH can be measured using a pH meter manufactured by Orion.

[0234] In the production method of the present disclosure, the polymerization may be carried out using at least one carboxylic acid type hydrocarbon surfactant. In addition, in the production method of the present disclosure, two or more of the carboxylic acid type hydrocarbon surfactants may be used simultaneously as the surfactant, or a surfactant other than the carboxylic acid type hydrocarbon surfactant may be used simultaneously as long as it is volatile or may remain in a molded product made of a fluoropolymer.

[0235] Examples of the other surfactants include nonionic surfactants and silicone surfactants.

[0236] Examples of the nonionic surfactant include: General formula (240): Rf 241 -(X 241) n -Y 241 (In the formula, Rf 241 is a partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, n is 0 or 1, and X 241 is -O-, -COO- or -OCO-, and Y 241 Ha-(CH2) p H, -(CH2) p OH or -(OR 241 ) q (OR 242 ) r OH, p is an integer from 1 to 12, q is an integer from 1 to 12, r is an integer from 0 to 12, and R 241 and R 242 is an alkylene group having 2 to 4 carbon atoms, provided that R 241 and R 242 are different from each other.) General formula (250):H(OR 251 ) u (OR 252 ) v OH (In the formula, R 251 and R 252 is an alkylene group having 1 to 4 carbon atoms, and u and v are integers from 1 to 5. 251 and R 252 are different from each other.) Block polymers represented by A nonionic polymer having, in its molecule, a hydrophobic group consisting of a hydrocarbon group having 8 to 20 carbon atoms and a hydrophilic group consisting of a polyalkylene oxide, and General formula (260):R 261 m -Si-(OR 262 ) 4-m (In the formula, R 261 is an alkyl group having 1 to 12 carbon atoms, R 262 is an alkyl group having 1 to 4 carbon atoms, and m is an integer of 1 to 3, At least one selected from the group consisting of:

[0237] Specific examples of block polymers represented by general formula (250) include block polymers composed of at least two segments selected from the group consisting of polyoxyethylene, polyoxypropylene, and polyoxybutylene. Among these, polyoxyethylene-polyoxypropylene block polymers and polyoxyethylene-polyoxybutylene block polymers are exemplified, with not only AB-type but also ABA-type block polymers being preferred. More preferably, polyoxyethylene-polyoxypropylene block polymers and polyoxypropylene-polyoxyethylene-polyoxypropylene block polymers can be used to prepare highly concentrated, stable fluoropolymer dispersions. Furthermore, a polyoxyethylene segment content of 10 to 50% is preferred because it reduces the occurrence of aggregates, likely due to re-agglomeration. A content of 20 to 40% is even more preferred because it allows the preparation of low-viscosity fluoropolymer dispersions. The molecular weight is not particularly limited, but should be 1000 to 7000 g / mol. A molecular weight of 2500 to 6500 g / mol is particularly preferred because it allows the preparation of dispersions with low viscosity and excellent dispersibility.

[0238] Silicone surfactants include those described in Silicone Surfactants, R.M. Hill, Marcel Dekker, Inc., ISBN: 0-8247-00104. The structure of silicone surfactants comprises a distinct hydrophobic portion and a hydrophilic portion. The hydrophobic portion comprises one or more dihydrocarbylsiloxane units, where the substituents on the silicone atom are entirely hydrocarbon. These siloxane surfactants can also be considered hydrocarbon surfactants in the sense that the carbon atoms of the hydrocarbyl groups are fully substituted by hydrogen atoms, which may be substituted by halogens such as fluorine, i.e., the monovalent substituents on the carbon atoms of the hydrocarbyl groups are hydrogen.

[0239] The hydrophilic portion of the silicone surfactant may comprise one or more polar moieties containing ionic groups such as phosphonates, phosphate esters, carboxylates, carbonates, taurates (as free acids, salts or esters), phosphine oxides, betaines, betaine copolyols, quaternary ammonium salts, etc. The ionic hydrophobic portion may also comprise ionically functionalized siloxane grafts. Examples of such silicone surfactants include polydimethylsiloxane-graft-(meth)acrylate salts, polydimethylsiloxane-graft-polyacrylate salts, and polydimethylsiloxane-grafted quaternary amines. The polar portion of the hydrophilic portion of the silicone surfactant may include nonionic groups formed by polyethers such as polyethylene oxide (PEO) and mixed polyethylene oxide / propylene oxide polyethers (PEO / PPO); monosaccharides and disaccharides; and water-soluble heterocycles such as pyrrolidinone. The ratio of ethylene oxide to propylene oxide (EO / PO) may be varied in mixed polyethylene oxide / propylene oxide polyethers.

[0240] The hydrophilic portion of the silicone surfactant may also contain a combination of ionic and nonionic portions. Such portions include, for example, ionically end-functionalized or randomly functionalized polyethers or polyols. Preferred for the implementation of the present disclosure are silicones with nonionic portions, i.e., nonionic silicone surfactants.

[0241] The arrangement of hydrophobic and hydrophilic moieties in the structure of the silicone surfactant may take the form of a diblock polymer (AB), a triblock polymer (ABA) (where "B" represents the siloxane portion of the molecule), or a multiblock polymer. Alternatively, the silicone surfactant may comprise a graft polymer.

[0242] Silicone surfactants are also disclosed in US Pat. No. 6,841,616.

[0243] Silicone-based anionic hydrocarbon surfactants include SilSense, available from Noveon® Consumer Specialties of Lubrizol Advanced Materials, Inc. TM PE-100 Silicone, SilSense TM CA-1 silicone and the like.

[0244] Anionic hydrocarbon surfactants also include the sulfosuccinate surfactant Lankropol® K8300 from Akzo Nobel Surface Chemistry LLC. Examples of sulfosuccinate hydrocarbon surfactants include sodium diisodecyl sulfosuccinate (Emulsogen® SB10 from Clariant) and sodium diisotridecyl sulfosuccinate (Polirol® TR / LNA from Cesapinia Chemicals).

[0245] The hydrocarbon surfactants include PolyFox® surfactants from Omnova Solutions, Inc. TM PF-156A, PolyFox TM PF-136A, etc.)

[0246] When the carboxylic acid hydrocarbon surfactant (in the second production method, an aliphatic carboxylic acid hydrocarbon surfactant) is used in combination with other surfactants, the content of the carboxylic acid hydrocarbon surfactant relative to the total amount of surfactants is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and particularly preferably 90% by mass or more. In the polymerization step, it is preferable that the carboxylic acid hydrocarbon surfactant is not substantially used in combination with other surfactants, and the content of the other surfactants is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, of the total amount of surfactants.

[0247] The carboxylic acid type hydrocarbon surfactant is preferably at least one selected from the group consisting of surfactants represented by formula (α), surfactants (1-0) represented by general formula (1-0) above, surfactants (a) represented by formula (a) above, surfactants (b) represented by formula (b) above, and surfactants obtained by subjecting these surfactants to radical treatment or oxidation treatment.

[0248] The aliphatic carboxylic acid-type hydrocarbon surfactant is preferably at least one selected from the group consisting of surfactants represented by formula (α), surfactants represented by the above general formula (1-0A), and surfactants obtained by subjecting these surfactants to radical treatment or oxidation treatment, and particularly preferably at least one selected from the group consisting of surfactants represented by formula (α), and surfactants obtained by subjecting surfactants represented by formula (α) to radical treatment or oxidation treatment.

[0249] The polymerization step is preferably one in which the fluoromonomer is polymerized substantially in the absence of a fluorine-containing surfactant. Conventionally, fluoropolymers have been polymerized using fluorosurfactants, but the production method of the present disclosure makes it possible to obtain fluoropolymer powders with a reduced content of the above-mentioned specific fluorine-containing compounds without using fluorosurfactants. As used herein, the phrase "substantially in the absence of a fluorine-containing surfactant" means that the fluorine-containing surfactant is present at 10 ppm or less, preferably 1 ppm or less, more preferably 100 ppb or less, even more preferably 10 ppb or less, and still more preferably 1 ppb or less, relative to the aqueous medium.

[0250] Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants. The anionic fluorine-containing surfactant may be, for example, a surfactant containing fluorine atoms and having a total carbon number of 20 or less excluding the anionic group.

[0251] The fluorine-containing surfactant may also be a surfactant containing fluorine in which the molecular weight of the anionic moiety is 1,000 or less, more preferably 800 or less, and even more preferably 600 or less. The "anionic portion" refers to the portion of the fluorine-containing surfactant excluding the cation. For example, F(CF2) represented by the formula (I) below n1 In the case of COOM, "F(CF2) n1 The "COO" part.

[0252] The above-mentioned fluorine-containing surfactant also includes a fluorine-containing surfactant having a LogPOW of not more than 3.5. The LogPOW is a partition coefficient between 1-octanol and water, and is expressed as LogP (where P represents the ratio of the fluorine-containing surfactant concentration in octanol to the fluorine-containing surfactant concentration in water when a 1:1 octanol / water mixture containing the fluorine-containing surfactant undergoes phase separation). The LogPOW is calculated from the HPLC elution time of the sample solution using standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) with known octanol / water partition coefficients under the following conditions: column: TOSOH ODS-120T column (φ4.6 mm×250 mm, manufactured by Tosoh Corporation), eluent: acetonitrile / 0.6% by mass HClO₄ / water=1 / 1 (vol / vol%), flow rate: 1.0 mL / min, sample amount: 300 μL, column temperature: 40°C, detection light: UV 210 nm. A calibration curve between each elution time and the known octanol / water partition coefficient is then prepared, and the LogPOW is calculated from the HPLC elution time of the sample solution based on this calibration curve.

[0253] Specific examples of the fluorine-containing surfactants include those described in U.S. Patent Application Publication Nos. 2007 / 0015864, 2007 / 0015865, 2007 / 0015866, 2007 / 0276103, 2007 / 0117914, 2007 / 142541, 2008 / 0015319, and U.S. Pat. No. 3,250,808. , U.S. Pat. No. 3,271,341, JP 2003-119204 A, WO 2005 / 042593, WO 2008 / 060461, WO 2007 / 046377, WO 2007 / 119526, WO 2007 / 046482, WO 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, WO 2013 / 189824, and WO 2013 / 189826.

[0254] The anionic fluorine-containing surfactant may be a compound represented by the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl or F. n0is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H's are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H's may be substituted with Cl. Y 0 is an anionic group. Y 0 The anionic group may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M. M is H, metal atom, NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, or Li. R 7 As for H or C 1-10 may be an organic group of H or C 1-4 may be an organic group of H or C 1-4 The alkyl group may be: M is H, a metal atom, or NR 7 4, and may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR 7 4, which may be H, Na, K, Li, or NH4. Above Rf n0 may be one in which 50% or more of H is substituted with fluorine.

[0255] The general formula (N 0 ) as a compound represented by The following general formula (N 1 ): X n0 -(CF2) m1 -Y 0 (N 1 ) (In the formula, X n0 is H, Cl, or F, m1 is an integer of 3 to 15, and Y 0is as defined above, a compound represented by the following general formula (N 2 ): Rf n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 ) (In the formula, Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X n1 is F or CF3, and Y 0 is as defined above, a compound represented by the following general formula (N 3 ): Rf n2 (CH2) m3 -(Rf n3 ) q -Y 0 (N 3 ) (In the formula, Rf n2 is a partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, m3 is an integer of 1 to 3, and Rf n3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, q is 0 or 1, and Y 0 is as defined above, a compound represented by the following general formula (N 4 ): Rf n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 ) (In the formula, Rf n4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y n1 and Y n2 are the same or different and are H or F, p is 0 or 1, and Y 0 is as defined above, and a compound represented by the following general formula (N 5 ): [ka] (In the formula, X n2 , X n3 and X n4 Rf may be the same or different and are H, F, or a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond. n5 is a linear or branched partially or fully fluorinated alkylene group having 1 to 3 carbon atoms, which may contain an ether bond; L is a linking group; Y 0 is as defined above, where X n2 , X n3 , X n4 and Rf n5 The total number of carbon atoms is 18 or less.

[0256] The general formula (N 0 ) More specifically, the compounds represented by the formula (I) include perfluorocarboxylic acids (I) represented by the following general formula (I), ω-H perfluorocarboxylic acids (II) represented by the following general formula (II), perfluoropolyether carboxylic acids (III) represented by the following general formula (III), perfluoroalkyl alkylene carboxylic acids (IV) represented by the following general formula (IV), perfluoroalkoxy fluorocarboxylic acids (V) represented by the following general formula (V), perfluoroalkyl sulfonic acids (VI) represented by the following general formula (VII), ω-H perfluoro sulfonic acids (VII) represented by the following general formula (VII), perfluoroalkyl alkylene sulfonic acids (VIII) represented by the following general formula (VIII), alkyl alkylene carboxylic acids (IX) represented by the following general formula (IX), fluorocarboxylic acids (X) represented by the following general formula (X), alkoxy fluoro sulfonic acids (XI) represented by the following general formula (XI), compounds (XII) represented by the following general formula (XII), and compounds (XIII) represented by the following general formula (XIII).

[0257] The perfluorocarboxylic acid (I) is represented by the following general formula (I): F(CF2) n1 COOM (I) (wherein n1 is an integer of 3 to 14, and M is H, a metal atom, or NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group.

[0258] The ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF2) n2 COOM (II) (wherein n2 is an integer of 4 to 15, and M is as defined above).

[0259] The perfluoropolyether carboxylic acid (III) is represented by the following general formula (III): Rf 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM (III) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above.

[0260] The perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): Rf 2 (CH2) n4 Rf 3 COOM (IV) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, and Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.

[0261] The alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): Rf 4 -O-CY 1 Y 2 CF2-COOM (V) (In the formula, Rf 4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0262] The perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F(CF2) n5 SO3M (VI) (wherein n5 is an integer of 3 to 14, and M is as defined above).

[0263] The ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF2) n6 SO3M (VII) (wherein n6 is an integer of 4 to 14, and M is as defined above).

[0264] The perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII): Rf 5 (CH2) n7 SO3M (VIII) (In the formula, Rf 5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is as defined above.

[0265] The alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): Rf 6 (CH2) n8 COOM (IX) (In the formula, Rf 6 is a linear or branched partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer of 1 to 3, and M is as defined above.

[0266] The fluorocarboxylic acid (X) is represented by the following general formula (X): Rf 7 -O-Rf 8 -O-CF2-COOM (X) (In the formula, Rf 7 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond; Rf 8 is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above.

[0267] The alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf 9 -O-CY 1 Y 2 CF2-SO3M (XI) (In the formula, Rf 9 is a linear or branched alkyl group having 1 to 12 carbon atoms, which may contain an ether bond, and which may contain chlorine, and which is partially or completely fluorinated; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0268] The compound (XII) is represented by the following general formula (XII): [ka] In the formula, X 1 , X 2 and X 3 may be the same or different and are H, F and linear or branched partially or fully fluorinated alkyl groups having 1 to 6 carbon atoms which may contain ether bonds; Rf 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y 0 is an anionic group. Y 0may be -COOM, -SO2M, or -SO3M, and may be -SO3M or COOM (wherein M is as defined above). Examples of L include a single bond and a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.

[0269] The compound (XIII) is represented by the following general formula (XIII): Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII) (In the formula, Rf 11 is a fluoroalkyl group containing chlorine and having 1 to 5 carbon atoms, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. Compound (XIII) is represented by the formula: CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture having an average molecular weight of 750, wherein n9 and n10 are defined above).

[0270] Examples of the anionic fluorine-containing surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0271] The polymerization step may further comprise polymerizing the fluoromonomer in the presence of a nucleating agent.

[0272] The nucleating agent is preferably at least one selected from the group consisting of, for example, fluoropolyethers, nonionic surfactants, and chain transfer agents. In this case, the polymerization step is preferably a step of obtaining a fluoropolymer by polymerizing a fluoromonomer in an aqueous medium in the presence of a carboxylic acid type hydrocarbon surfactant and the nucleating agent.

[0273] The fluoropolyether is preferably a perfluoropolyether.

[0274] The above fluoropolyether preferably has repeating units represented by formulas (1a) to (1d). (-CFCF3-CF2-O-) n (1a) (-CF2-CF2-CF2-O-) n (1b) (-CF2-CF2-O-) n -(-CF2-O-) m (1c) (-CF2-CFCF3-O-) n -(-CF2-O-) m (1d) (In formulas (1a) to (1d), m and n are integers of 1 or more.)

[0275] The fluoropolyether is preferably a fluoropolyether acid or its salt, and the fluoropolyether acid is preferably a carboxylic acid, a sulfonic acid, a sulfonamide, or a phosphonic acid, and more preferably a carboxylic acid. Among the fluoropolyether acids or their salts, the salt of a fluoropolyether acid is preferred, the ammonium salt of a fluoropolyether acid is more preferred, and the ammonium salt of a fluoropolyether carboxylic acid is even more preferred.

[0276] The fluoropolyether acids or salts thereof can have any chain structure in which oxygen atoms in the main chain of the molecule are separated by saturated fluorocarbon groups having 1 to 3 carbon atoms. Two or more types of fluorocarbon groups can be present in the molecule.

[0277] The fluoropolyether acid or salt thereof is selected from the group consisting of fluoropolyether acids and fluoropolyether salts having the following formula: CF3-CF2-CF2-O(-CFCF3-CF2-O-) n CFCF3-COOH, CF3-CF2-CF2-O(-CF2-CF2-CF2-O-) n -CF2-CF2COOH, or HOOC-CF2-O(-CF2-CF2-O-) n-(-CF2-O-) m CF2COOH (wherein m and n are the same as above.) or a salt thereof.

[0278] These structures are discussed by Kasai in J. Appl. Polymer Sci., 57, 797 (1995). As disclosed therein, such fluoropolyethers can have carboxylic acid groups or salts thereof at one or both ends. Similarly, such fluoropolyethers can have sulfonic or phosphonic acid groups or salts thereof at one or both ends. In addition, fluoropolyethers with acid functional groups at both ends can have different groups at each end. For monofunctional fluoropolyethers, the other end of the molecule is usually perfluorinated, but may contain hydrogen or chlorine atoms.

[0279] Fluoropolyethers having acid groups at one or both ends have at least two ether oxygens, preferably at least four ether oxygens, and even more preferably at least six ether oxygens. Preferably, at least one of the fluorocarbon groups separating the ether oxygens, more preferably at least two of such fluorocarbon groups, has 2 or 3 carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups separating the ether oxygens have 2 or 3 carbon atoms. Also, preferably, the fluoropolyether has a total of at least 15 carbon atoms, and for example, the preferred minimum value of n or n + m in the above repeating unit structure is at least 5. Two or more fluoropolyethers having acid groups at one or both ends can be used in the method according to the present disclosure. Typically, unless special care is taken in the preparation of a single specific fluoropolyether compound, the fluoropolyether may contain multiple compounds in various proportions within the molecular weight range relative to the average molecular weight.

[0280] The fluoropolyether preferably has a number average molecular weight of 800 g / mol or more. Because the fluoropolyether acid or its salt may be difficult to disperse in an aqueous medium, the number average molecular weight is preferably less than 6000 g / mol. The fluoropolyether acid or its salt more preferably has a number average molecular weight of 800 to 3500 g / mol, and even more preferably 1000 to 2500 g / mol.

[0281] The amount of the fluoropolyether is preferably 5 to 3000 ppm, more preferably 5 to 2000 ppm, with a more preferred lower limit of 10 ppm and a more preferred upper limit of 100 ppm relative to the aqueous medium.

[0282] The nonionic surfactant as the nucleating agent may be any of the nonionic surfactants described above, and is preferably a nonionic surfactant that does not contain fluorine. For example, a nonionic surfactant represented by the following general formula (i) R 3 -OA 1 -H(i) (In the formula, R 3 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain. 3 The number of carbon atoms in R is preferably 10 to 16, and more preferably 12 to 16. 3 When the carbon number of R is 18 or less, good dispersion stability of the aqueous dispersion is easily obtained. 3 If the carbon number exceeds 18, the flow temperature is high and it is difficult to handle. 3 If the number of carbon atoms is less than 8, the surface tension of the aqueous dispersion increases, and the permeability and wettability tend to decrease.

[0283] The polyoxyalkylene chain may be composed of oxyethylene and oxypropylene. The polyoxyalkylene chain has an average repeat number of 5 to 20 oxyethylene groups and an average repeat number of 0 to 2 oxypropylene groups, and is a hydrophilic group. The number of oxyethylene units may include either a broad or narrow unimodal distribution, which is typically provided, or a broader or bimodal distribution obtained by blending. When the average repeat number of oxypropylene groups is greater than 0, the oxyethylene and oxypropylene groups in the polyoxyalkylene chain may be arranged in a block or random configuration. From the viewpoint of viscosity and stability of the aqueous dispersion, a polyoxyalkylene chain having an average repeat number of 7 to 12 oxyethylene groups and an average repeat number of 0 to 2 oxypropylene groups is preferred. 1 If the oxypropylene group has an average of 0.5 to 1.5, low foaming properties are favorable and it is preferable.

[0284] More preferably, R 3 is (R')(R")HC-, where R' and R" are the same or different straight, branched, or cyclic alkyl groups having a total of at least 5, preferably 7 to 17, carbon atoms. Preferably, at least one of R' or R" is a branched or cyclic hydrocarbon group.

[0285] Specific examples of the nonionic surfactant include C 13 H 27 -O-(C2H4O) 10 -H, C 12 H 25 -O-(C2H4O) 10 -H, C 10 H 21 CH(CH3)CH2-O-(C2H4O)9-H, C 13 H 27 -O-(C2H4O)9-(CH(CH3)CH2O)-H, C 16 H 33 -O-(C2H4O) 10 -H, HC(CH 11 )(C7H 15)-O-(C2H4O)9-H, etc. Commercially available examples of the nonionic surfactant include Genapol X080 (product name, manufactured by Clariant), the Noigen TDS series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) such as Noigen TDS-80 (trade name), the Leocol TD series (manufactured by Lion Chemical Industries, Ltd.) such as Leocol TD-90 (trade name), the Lionol (registered trademark) TD series (manufactured by Lion Chemical Industries, Ltd.), the T-Det A series (manufactured by Harcros Chemicals) such as T-Det A138 (trade name), and the Tergitol (registered trademark) 15S series (manufactured by The Dow Chemical Company).

[0286] The nonionic surfactant is preferably an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 4 to about 18 ethylene oxide units, an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 6 to about 12 ethylene oxide units, or a mixture thereof. Nonionic surfactants of this type are also commercially available, for example, as TERGITOL TMN-6, TERGITOL TMN-10, and TERGITOL TMN-100X (all product names, manufactured by The Dow Chemical Company).

[0287] The hydrophobic group of the nonionic surfactant may be any of an alkylphenol group, a linear alkyl group, and a branched alkyl group. For example, the nonionic surfactant may be a surfactant represented by the following general formula (ii): R 4 -C6H4-OA 2 -H (ii) (In the formula, R 4 is a linear or branched primary or secondary alkyl group having 4 to 12 carbon atoms, and A 2 is a polyoxyalkylene chain.) Specific examples of the polyoxyethylene alkylphenyl ether nonionic compounds include Triton (registered trademark) X-100 (trade name, manufactured by Dow Chemical Company).

[0288] Examples of such nonionic surfactants include difunctional block copolymers supplied by BASF as the Pluronic® R series and tridecyl alcohol alkoxylates supplied by BASF as the Iconol® TDA series.

[0289] The amount of the nonionic surfactant is preferably 0.1 to 0.0000001% by mass, and more preferably 0.01 to 0.000001% by mass, relative to the aqueous medium.

[0290] Examples of the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, isobutane, methanol, ethanol, isopropanol, acetone, various mercaptans, various halogenated hydrocarbons such as carbon tetrachloride, and cyclohexane.

[0291] Bromine compounds or iodine compounds may be used as chain transfer agents. Polymerization methods using bromine compounds or iodine compounds include, for example, a method of polymerizing fluoromonomers in an aqueous medium in the presence of a bromine compound or an iodine compound in a substantially oxygen-free state (iodine transfer polymerization method). Representative examples of the bromine compounds or iodine compounds used include, for example, compounds represented by the general formula: R a I x Br y (wherein x and y are each an integer of 0 to 2 and satisfy 1≦x+y≦2; R a is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom). By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0292] Examples of iodine compounds include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, and BrCF2CFCl. Br, CFBrClCFClBr, BrCFCFCFBr, BrCFCFBrOCF, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, diiodomonobromo-substituted benzene, and (2-iodoethyl) and (2-bromoethyl) substituted benzenes. These compounds may be used alone or in combination with each other.

[0293] Among these, at least one selected from the group consisting of alkanes and alcohols is preferred from the viewpoints of polymerization reactivity, crosslinking reactivity, availability, etc. The number of carbon atoms in the alkanes is preferably 1 to 6, more preferably 1 to 5. The number of carbon atoms in the alcohols is preferably 1 to 5, more preferably 1 to 4. The chain transfer agent is particularly preferably at least one selected from the group consisting of methane, ethane, propane, isobutane, methanol, ethanol, and isopropanol.

[0294] The amount of the chain transfer agent is preferably 0.001 to 10,000 ppm relative to the aqueous medium. The amount of the chain transfer agent is more preferably 0.01 ppm or more, even more preferably 0.05 ppm or more, and particularly preferably 0.1 ppm or more relative to the aqueous medium. The amount is more preferably 1,000 ppm or less, even more preferably 500 ppm or less, and particularly preferably 100 ppm or less relative to the aqueous medium.

[0295] The chain transfer agent may be added all at once to the reaction vessel before the initiation of polymerization, may be added all at once after the initiation of polymerization, may be added in multiple divided portions during the polymerization, or may be added continuously during the polymerization.

[0296] In the production method of the present disclosure, in addition to the hydrocarbon surfactant and other surface-active compounds used as desired, additives can be used to stabilize each compound, such as buffers, pH adjusters, stabilizing aids, and dispersion stabilizers.

[0297] The stabilizing aid is preferably paraffin wax, fluorine-based oil, fluorine-based solvent, silicone oil, etc. The stabilizing aid may be used alone or in combination of two or more. The stabilizing aid is more preferably paraffin wax. The paraffin wax may be liquid, semi-solid, or solid at room temperature, but is preferably a saturated hydrocarbon having 12 or more carbon atoms. The melting point of the paraffin wax is usually preferably 40 to 65°C, more preferably 50 to 65°C.

[0298] The amount of the stabilizing aid used is preferably 0.1 to 12 mass %, more preferably 0.1 to 8 mass %, based on the mass of the aqueous medium used. It is desirable that the stabilizing aid is sufficiently hydrophobic so that it is completely separated from the aqueous fluoropolymer emulsion after emulsion polymerization of the fluoromonomer, and does not become a contaminating component.

[0299] The polymerization in the above production method can be carried out by charging an aqueous medium, the hydrocarbon surfactant, monomers, and other additives as necessary into a polymerization reactor, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the polymerization reaction has started, additional monomers, polymerization initiators, chain transfer agents, the surfactants, etc. may be added depending on the purpose. The hydrocarbon surfactant may also be added after the polymerization reaction has started.

[0300] The polymerization initiator is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, polymerization can also be initiated as a redox reaction in combination with a reducing agent, etc. The concentration of the polymerization initiator is determined appropriately depending on the type of monomer, the molecular weight of the desired fluoropolymer, and the reaction rate.

[0301] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0302] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and the like. Also, di(ω-hydro-dodecafluorohexanoyl) peroxide, di(ω-hydro-tetradecafluoroheptanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro Representative examples include di[perfluoro(or fluorochloro)acyl]peroxides such as di(ω-chlorohexafluorobutanoyl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, di(ω-chloro-tetradecafluorooctanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl)peroxide, di(trichlorooctafluorohexanoyl)peroxide, di(tetrachloroundecafluorooctanoyl)peroxide, di(pentachlorotetradecafluorodecanoyl)peroxide, and di(undecachlorodotriacontafluorodocosanoyl)peroxide.

[0303] For example, when polymerization is carried out at low temperatures below 30°C, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and cerium ammonium nitrate. Examples of reducing agents include bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. To increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the redox initiator combination. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate. Examples of the redox initiator include potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, manganese triacetate / oxalic acid, manganese triacetate / ammonium oxalate, cerium ammonium nitrate / oxalic acid, and cerium ammonium nitrate / ammonium oxalate, with potassium permanganate / oxalic acid being preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into a polymerization vessel in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, it is preferred to charge oxalic acid into a polymerization vessel and then continuously add potassium permanganate thereto.

[0304] The amount of polymerization initiator to be added is not particularly limited, but may be added all at once, stepwise, or continuously at the beginning of polymerization in an amount (for example, several ppm relative to the water concentration) that does not significantly decrease the polymerization rate. The upper limit is a range in which the reaction temperature can be increased while removing heat from the equipment using the heat of polymerization reaction, and a more preferred upper limit is a range in which the heat of polymerization reaction can be removed from the equipment.

[0305] A radical polymerization initiator can also be used as the polymerization initiator. A peroxide is preferred as the radical polymerization initiator. Examples of radical polymerization initiators include the oil-soluble radical polymerization initiators and water-soluble radical polymerization initiators described above, with the water-soluble radical polymerization initiators being preferred. A more preferred water-soluble radical polymerization initiator is a peroxide, and even more preferred are persulfates, organic peroxides, or mixtures thereof. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of organic peroxides include disuccinic acid peroxide and diglutaric acid peroxide. Even more preferred are ammonium persulfate and disuccinic acid peroxide. The polymerization step preferably involves adding 5 ppm or more of ammonium persulfate to the aqueous medium, more preferably 10 ppm or more, even more preferably 20 ppm or more, even more preferably 30 ppm or more, particularly preferably 40 ppm or more, even more preferably 50 ppm or more, especially more preferably 80 ppm or more, and especially especially preferably 100 ppm or more. In the polymerization step, after the polymerization is initiated, a radical polymerization initiator may be added continuously or intermittently.

[0306] The aqueous medium is a reaction medium for polymerization and refers to a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, ether, or ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower.

[0307] In the aqueous dispersion obtained by the polymerization, the average primary particle size of the fluoropolymer is, for example, 50 to 500 nm. The lower limit of the average primary particle size is preferably 100 nm, more preferably 150 nm. The upper limit of the average primary particle size is preferably 400 nm, more preferably 350 nm. The average primary particle size can be measured by dynamic light scattering. An aqueous fluoropolymer dispersion adjusted to a fluoropolymer solids concentration of approximately 1.0% by mass is prepared, and the average primary particle size can be measured by dynamic light scattering at 25°C, with a solvent (water) refractive index of 1.3328 and a solvent (water) viscosity of 0.8878 mPa·s, and 70 cumulative measurements. For example, an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for the dynamic light scattering method.

[0308] The above carboxylic acid type hydrocarbon surfactant can also be suitably used as a dispersant for dispersing the fluoropolymer obtained by polymerization in an aqueous medium.

[0309] The polymerization usually produces an aqueous dispersion containing particles of the fluoropolymer, the surfactant, and the aqueous medium, in which the fluoropolymer particles are dispersed in the aqueous medium in the presence of the surfactant.

[0310] The lower limit of the content of the carboxylic acid type hydrocarbon surfactant in the aqueous dispersion is preferably 10 ppb, more preferably 100 ppb, even more preferably 1 ppm, even more preferably 10 ppm, and particularly preferably 50 ppm, relative to the fluoropolymer. The upper limit is preferably 100,000 ppm, more preferably 50,000 ppm, even more preferably 10,000 ppm, and even more preferably 5,000 ppm, relative to the fluoropolymer.

[0311] The aqueous dispersion may be any of an aqueous dispersion obtained by carrying out the above-mentioned polymerization, a dispersion obtained by concentrating this aqueous dispersion or by subjecting it to a dispersion stabilization treatment, and a dispersion obtained by dispersing a powder of a fluoropolymer in an aqueous medium in the presence of the above-mentioned surfactant.

[0312] The aqueous dispersion can also be produced by (I) contacting the aqueous dispersion obtained by the polymerization with an anion exchange resin or a mixed bed containing an anion exchange resin and a cation exchange resin in the presence of a nonionic surfactant, and / or (II) concentrating the aqueous dispersion to a solids concentration of 30 to 70 mass% relative to 100 mass% of the aqueous dispersion. The nonionic surfactant is not particularly limited, but the ones described below can be used. The anion exchange resin is not particularly limited, but known ones can be used. In addition, known methods can be used for contacting with the anion exchange resin. The aqueous dispersion can be produced by subjecting the aqueous dispersion obtained by the polymerization to step (I) and then subjecting the aqueous dispersion obtained in step (I) to step (II) to produce a purified aqueous dispersion. Alternatively, a purified aqueous dispersion can be produced by performing step (II) without performing step (I). Steps (I) and (II) can also be performed repeatedly or in combination.

[0313] The anion exchange resin may, for example, have a functional group of -N + X - A strongly basic anion exchange resin having (CH3)3 groups (X represents Cl or OH), -N + X - Examples of suitable resins include well-known strong basic anion exchange resins having a (CH)(CHOH) group (X is the same as above). Specific examples include those described in WO 99 / 62858, WO 03 / 020836, WO 2004 / 078836, WO 2013 / 027850, and WO 2014 / 084399.

[0314] The cation exchange resin is not particularly limited, and may be, for example, a resin having a functional group of -SO3 - Strongly acidic cation exchange resin with -COO functional group -Examples of suitable ion exchange resins include weakly acidic cation exchange resins having a hydroxyl group, and other well-known ion exchange resins. Among these, from the viewpoint of removal efficiency, strongly acidic cation exchange resins are preferred. + Strongly acidic cation exchange resins of the type are more preferred.

[0315] The above-mentioned "mixed bed consisting of a cation exchange resin and an anion exchange resin" is not particularly limited, and includes cases where both are packed in the same column, where both are packed in different columns, where both are dispersed in an aqueous dispersion, etc.

[0316] Known methods can be used for the concentration. Specific examples include those described in International Publication Nos. 2007 / 046482 and 2014 / 084399. Examples include phase separation, centrifugal sedimentation, cloud point concentration, electroconcentration, electrophoresis, filtration using ultrafiltration, filtration using a reverse osmosis membrane (RO membrane), and nanofiltration. The concentration can be adjusted to a fluoropolymer concentration of 30 to 70% by mass depending on the application. Concentration may impair the stability of the dispersion, and in this case, a dispersion stabilizer may be further added. As the dispersion stabilizer, the above-mentioned nonionic surfactants and various other surfactants may be added. The nonionic surfactant may be the same as the nonionic surfactant exemplified as the nucleating agent described above, and the nonionic surfactants described above may be appropriately used. The nonionic surfactant preferably does not contain an aromatic moiety. The cloud point of a nonionic surfactant is a measure of the solubility of the surfactant in water. The surfactant used in the aqueous dispersion of the present disclosure has a cloud point of about 30°C to about 90°C, preferably about 35°C to about 85°C.

[0317] The total amount of the dispersion stabilizer is a concentration of 0.5 to 20% by mass relative to the solid content of the dispersion. If it is less than 0.5% by mass, the dispersion stability may be poor, and if it exceeds 20% by mass, the dispersion effect will not be commensurate with the amount present, making it impractical. A more preferred lower limit of the dispersion stabilizer is 2% by mass, and a more preferred upper limit is 12% by mass.

[0318] The method for producing a fluoropolymer powder of the present disclosure may include a step of recovering the aqueous fluoropolymer dispersion obtained in the polymerization step. The method of making the fluoropolymer powder of the present disclosure may also include a step of recovering the coagulated wet fluoropolymer powder.

[0319] Examples of the fluoropolymer include a TFE polymer in which the monomer with the highest molar fraction in the polymer (hereinafter referred to as the "most abundant monomer") is TFE, a VDF polymer in which the most abundant monomer is VDF, and a CTFE polymer in which the most abundant monomer is CTFE. More preferred embodiments for each fluoropolymer are described below.

[0320] The TFE polymer may suitably be a TFE homopolymer or a copolymer comprising (1) TFE, (2) one or more fluorine-containing monomers other than TFE having 2 to 8 carbon atoms, particularly VDF, HFP, or CTFE, and (3) other monomers. Examples of the (3) other monomers include fluoro(alkyl vinyl ethers) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; fluorodioxole; perfluoroalkylethylene; ω-hydroperfluoroolefin; and perfluoroallyl ether.

[0321] The TFE polymer may also be a copolymer of TFE and one or more fluorine-free monomers. Examples of the fluorine-free monomers include alkenes such as ethylene and propylene; vinyl esters; and vinyl ethers. The TFE polymer may also be a copolymer of TFE and one or more fluorine-containing monomers having 2 to 8 carbon atoms and one or more fluorine-free monomers.

[0322] The VDF polymer may suitably be a copolymer of (1) VDF, (2) one or more fluoroolefins other than VDF having 2 to 8 carbon atoms, particularly TFE, HFP, or CTFE, and (3) a perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.

[0323] The CTFE polymer may suitably be a CTFE homopolymer or a copolymer consisting of (1) CTFE, (2) one or more fluoroolefins other than CTFE having 2 to 8 carbon atoms, particularly TFE or HFP, and (3) a perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.

[0324] The CTFE polymer may also be a copolymer of CTFE and one or more non-fluorine-containing monomers, and the non-fluorine-containing monomers include alkenes such as ethylene and propylene; vinyl esters; and vinyl ethers.

[0325] The fluoropolymers produced by the manufacturing methods of the present disclosure can be glassy, ​​plastic, or elastomeric. They can be amorphous or partially crystalline and can be subjected to compression-sintering, melt-processing, or non-melt-processing.

[0326] In the production method of the present disclosure, for example, (I) tetrafluoroethylene polymer [TFE polymer (PTFE)] can be suitably produced as a non-melt-processable fluororesin, and (II) ethylene / TFE copolymer [ETFE], TFE / HFP copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], TFE / perfluoroallyl ether copolymer, electrolyte polymer precursor, etc. can be suitably produced as a melt-processable fluororesin.

[0327] The fluoropolymer is preferably a fluororesin, and particularly, a fluororesin having a fluorine substitution rate of 50% or more as calculated by the following formula is more preferred, a fluororesin having a fluorine substitution rate of more than 50% is even more preferred, a fluororesin having a fluorine substitution rate of 55% or more is even more preferred, a fluororesin having a fluorine substitution rate of 60% or more is even more preferred, a fluororesin having a fluorine substitution rate of 75% or more is even more preferred, a fluororesin having a fluorine substitution rate of 80% or more is particularly preferred, and a fluororesin having a fluorine substitution rate of 90 to 100%, i.e., a perfluororesin, is most preferred. (formula) Fluorine substitution rate (%) = (number of fluorine atoms bonded to carbon atoms constituting the fluoropolymer) / ((number of hydrogen atoms bonded to carbon atoms constituting the fluoropolymer) + (number of fluorine atoms and chlorine atoms bonded to carbon atoms constituting the fluoropolymer)) × 100

[0328] As the perfluororesin, a fluororesin having a fluorine substitution rate of 95 to 100% is more preferred, PTFE, FEP, and PFA are even more preferred, PTFE is particularly preferred, and high-molecular-weight PTFE is particularly preferred.

[0329] The fluoropolymer may have a core-shell structure. For example, a fluoropolymer having a core-shell structure may be a modified PTFE, which contains a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE in a particle. For example, such a modified PTFE may be the PTFE described in JP-A-2005-527652.

[0330] The core-shell structure may have the following structure: Core: TFE homopolymer Shell: TFE homopolymer Core: Modified PTFE Shell: TFE homopolymer Core: Modified PTFE Shell: Modified PTFE Core: TFE homopolymer Shell: Modified PTFE Core: Low molecular weight PTFE Shell: High molecular weight PTFE Core: High molecular weight PTFE Shell: Low molecular weight PTFE

[0331] In the fluoropolymer having the core-shell structure, the lower limit of the core ratio is preferably 0.5 mass%, more preferably 1.0 mass%, even more preferably 3.0 mass%, particularly preferably 5.0 mass%, and most preferably 10.0 mass%. The upper limit of the core ratio is preferably 99.5 mass%, more preferably 99.0 mass%, even more preferably 98.0 mass%, even more preferably 97.0 mass%, particularly preferably 95.0 mass%, and most preferably 90.0 mass%.

[0332] In the fluoropolymer having the core-shell structure, the lower limit of the shell ratio is preferably 0.5% by mass, more preferably 1.0% by mass, even more preferably 3.0% by mass, particularly preferably 5.0% by mass, and most preferably 10.0% by mass. The upper limit of the shell ratio is preferably 99.5% by mass, more preferably 99.0% by mass, even more preferably 98.0% by mass, even more preferably 97.0% by mass, particularly preferably 95.0% by mass, and most preferably 90.0% by mass.

[0333] In the fluoropolymer having a core-shell structure, the core or the shell may be configured to have two or more layers. For example, the fluoropolymer may have a three-layer structure having a core center of modified PTFE, a core outer layer of TFE homopolymer, and a shell of modified PTFE. An example of a fluoropolymer having such a three-layer structure is the PTFE described in WO 2006 / 054612.

[0334] The above-mentioned (I) non-melt-processible fluororesin and (II) melt-processible fluororesin, which are suitably produced by the production method of the present disclosure, are preferably produced in the following manner.

[0335] (I) Non-melt-processable fluororesin In the production method of the present disclosure, TFE polymerization is usually carried out at a polymerization temperature of 10 to 150°C and a polymerization pressure of 0.05 to 5 MPaG. For example, the polymerization temperature is more preferably 30°C or higher, and even more preferably 50°C or higher. It is more preferably 120°C or lower, and even more preferably 100°C or lower. The polymerization pressure is more preferably 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher, and more preferably 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower. In particular, from the viewpoint of improving the yield of the fluoropolymer, it is preferably 1.0 MPaG or higher, more preferably 1.2 MPaG or higher, more preferably 1.5 MPaG or higher, and even more preferably 2.0 MPaG or higher.

[0336] In one embodiment, the polymerization is carried out by charging pure water into a pressure-resistant reaction vessel equipped with a stirrer, deoxidizing, then charging TFE, adjusting the temperature to a predetermined level, and adding a polymerization initiator to initiate the reaction. If the pressure decreases as the reaction proceeds, additional TFE is continuously or intermittently supplied to maintain the initial pressure. Once a predetermined amount of TFE has been supplied, the supply is stopped, the TFE in the reaction vessel is purged, and the temperature is returned to room temperature to terminate the reaction. Additional TFE may be continuously or intermittently supplied to prevent a decrease in pressure.

[0337] In the production of the TFE polymer (PTFE), various known modified monomers can also be used in combination. In this specification, the term "PTFE" refers not only to a TFE homopolymer but also to a copolymer of TFE and a modified monomer that is non-melt-processable (hereinafter referred to as "modified PTFE").

[0338] The PTFE may be a homopolymer of TFE, or may be a modified PTFE containing 99.0% by mass or more of polymerized units based on TFE and 1.0% by mass or less of polymerized units based on a modifying monomer.

[0339] The content of polymerized units based on a modifying monomer (hereinafter also referred to as "modified monomer units") in the modified PTFE is preferably in the range of 0.00001 to 1.0% by mass relative to the total polymerized units of the modified PTFE. The lower limit of the modified monomer units is more preferably 0.0001% by mass, even more preferably 0.001% by mass, and even more preferably 0.005% by mass. The upper limit of the modified monomer units is 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, or 0.05% by mass. In this specification, the modified monomer unit means a part of the molecular structure of PTFE that is derived from the modified monomer.

[0340] In this specification, the content of each monomer unit constituting PTFE can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer. In addition, the content of each monomer unit constituting PTFE can also be calculated from the amount of modified monomer added used in polymerization.

[0341] The modifying monomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include fluoromonomers and non-fluoromonomers.

[0342] The non-fluoromonomer is not particularly limited and may be selected from the group consisting of monomers having the general formula: CH2=CR Q1 -LR Q2 (In the formula, R Q1 represents a hydrogen atom or an alkyl group. L represents a single bond, -CO-O-*, -O-CO-* or -O-. * represents R Q2 R represents the bond position with Q2 represents a hydrogen atom, an alkyl group or a nitrile group.

[0343] Examples of non-fluoromonomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, vinyl methacrylate, vinyl acetate, acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, ethyl vinyl ether, cyclohexyl vinyl ether, etc. Of these, butyl methacrylate, vinyl acetate, and acrylic acid are preferred as non-fluoromonomers.

[0344] The fluoromonomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene (HFP), hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF), perhaloolefins such as chlorotrifluoroethylene, fluorovinyl ethers, (perfluoroalkyl)ethylenes, perfluoroallyl ethers, etc. The modified monomer used may be one type or multiple types.

[0345] The fluorovinyl ether is not particularly limited, and examples thereof include fluorovinyl ethers represented by the following general formula (A): CF2=CF-ORf (A) (wherein Rf represents a perfluoroorganic group). In this specification, the "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0346] An example of the fluorovinyl ether is perfluoro(alkyl vinyl ether) [PAVE], where Rf in the above general formula (A) is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the above perfluoroalkyl group is preferably 1 to 5.

[0347] Examples of the perfluoroalkyl group in the PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0348] The perfluorovinyl ether further includes those in which Rf in the general formula (A) is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and those in which Rf ...

[0349] [ka]

[0350] (wherein m represents 0 or an integer of 1 to 4), and Rf is a group represented by the following formula:

[0351] [ka]

[0352] (wherein n represents an integer of 1 to 4).

[0353] Examples of hydrogen-containing fluoroolefins include CH2=CF2, CFH=CH2, CFH=CF2, CF2=CFCF3, CH2=CFCF3, CH2=CHCF3, CHF=CHCF3 (E-isomer), and CHF=CHCF3 (Z-isomer).

[0354] The perfluorovinyl ether is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE), and more preferably PMVE.

[0355] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0356] Examples of perfluoroallyl ethers include: General formula: CF2=CF-CF2-ORf (wherein Rf represents a perfluoro organic group).

[0357] Rf in the above general formula is the same as Rf in general formula (A). Rf is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The perfluoroallyl ether is preferably at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, more preferably at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, and even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0358] A preferred example of the modifying monomer is a comonomer (3) having a monomer reactivity ratio of 0.1 to 8. The presence of the comonomer (3) makes it possible to obtain PTFE particles having a small particle size and an aqueous dispersion with high dispersion stability.

[0359] Here, the monomer reactivity ratio in copolymerization with TFE is the value obtained by dividing the rate constant when the propagating radical reacts with TFE when the propagating radical is less than a repeating unit based on TFE by the rate constant when the propagating radical reacts with a comonomer. The lower this value, the higher the reactivity of the comonomer with TFE. The monomer reactivity ratio can be calculated by copolymerizing TFE and a comonomer, determining the composition in the resulting polymer immediately after the start of copolymerization, and using the Feynman-Ross equation.

[0360] The copolymerization was carried out in a 6.0 L stainless steel autoclave using 3600 g of deionized, degassed water, 1000 ppm ammonium perfluorooctanoate relative to the water, and 100 g of paraffin wax at a pressure of 0.78 MPaG and a temperature of 70°C. 0.05 g, 0.1 g, 0.2 g, 0.5 g, and 1.0 g of comonomer were added to the reactor, respectively, and 0.072 g of ammonium persulfate (20 ppm relative to the water) was added. TFE was continuously fed to maintain the polymerization pressure at 0.78 MPaG. When the TFE charge reached 1000 g, stirring was stopped and the reactor was depressurized to atmospheric pressure. After cooling, the paraffin wax was separated to obtain an aqueous dispersion containing the product polymer. The aqueous dispersion was stirred to coagulate the product polymer, which was then dried at 150°C. The composition of the resulting polymer is calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0361] The comonomer (3) having a monomer reactivity ratio of 0.1 to 8 is preferably at least one selected from the group consisting of comonomers represented by formulas (3a) to (3d): CH2=CH-Rf 1 (3a) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 10 carbon atoms. CF2=CF-O-Rf 2 (3b) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 2 carbon atoms. CF2=CF-O-(CF2) n CF=CF2(3c) (wherein n is 1 or 2).

[0362] [ka] (In the formula, X 3 and X 4 is F, Cl or a methoxy group, and Y is of formula Y1 or Y2.

[0363] [ka] (In formula Y2, Z and Z′ are F or a fluorinated alkyl group having 1 to 3 carbon atoms.)

[0364] The content of the comonomer (3) units is preferably in the range of 0.00001 to 1.0% by mass relative to the total polymerized units of PTFE. The lower limit is more preferably 0.0001% by mass, even more preferably 0.001% by mass, and even more preferably 0.005% by mass. The upper limit is, in order of preference, 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0365] As the above-mentioned modified monomer, since it can obtain an aqueous dispersion of modified polytetrafluoroethylene particles with a small average primary particle size, a small aspect ratio of primary particles, and excellent stability, it is preferable to select at least one from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, fluoro(alkyl vinyl ether), (perfluoroalkyl)ethylene, ethylene, and modified monomers having a functional group capable of reacting by radical polymerization and a hydrophilic group.By using the above-mentioned modified monomer, it is possible to obtain an aqueous dispersion of PTFE with a smaller average primary particle size, a small aspect ratio of primary particles, and excellent dispersion stability.In addition, it is possible to obtain an aqueous dispersion with less uncoagulated polymer.

[0366] From the viewpoint of reactivity with TFE, the modifying monomer preferably contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether), and (perfluoroalkyl)ethylene. More preferably, it contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), (perfluorobutyl)ethylene, (perfluorohexyl)ethylene, and (perfluorooctyl)ethylene. The total amount of the hexafluoropropylene units, perfluoro(alkyl vinyl ether) units, and (perfluoroalkyl)ethylene units is preferably in the range of 0.00001 to 1% by mass relative to all polymerized units of PTFE. The lower limit of the total amount is more preferably 0.0001% by mass, even more preferably 0.001% by mass, and even more preferably 0.005% by mass. The upper limits, in descending order of preference, are 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0367] The above-mentioned modified monomer preferably includes a modified monomer having a functional group capable of reacting by radical polymerization and a hydrophilic group (hereinafter referred to as "modified monomer (A)").

[0368] The presence of the above-mentioned modifying monomer (A) can produce PTFE particles with a small primary particle size, and can produce an aqueous dispersion with high dispersion stability. In addition, the amount of uncoagulated polymer can be reduced. Furthermore, the aspect ratio of the primary particles can be reduced.

[0369] The amount of the modified monomer (A) used is preferably more than the amount corresponding to 0.1 ppm of the aqueous medium, more preferably more than 0.5 ppm, even more preferably more than 1.0 ppm, even more preferably 5 ppm or more, and particularly preferably 10 ppm or more. If the amount of the modified monomer (A) used is too small, the average primary particle size of the obtained PTFE may not be reduced. The amount of the modified monomer (A) used may be within the above range, but the upper limit can be, for example, 5000 ppm. In the above production method, the modified monomer (A) may be added to the system during the reaction to improve the stability of the aqueous dispersion during or after the reaction.

[0370] The above-mentioned modified monomer (A) is highly water-soluble, so even if unreacted modified monomer (A) remains in the aqueous dispersion, it can be easily removed in the concentration step or the coagulation and washing step.

[0371] The above-mentioned modifying monomer (A) is incorporated into the produced polymer during the polymerization process, but since the concentration of the modifying monomer (A) itself in the polymerization system is low and the amount incorporated into the polymer is small, there are no problems such as a decrease in the heat resistance of PTFE or coloration after baking.

[0372] Examples of the hydrophilic group in the modified monomer (A) include -NH, -PO, -PO(OM), -OPO, -OPO(OM), -SO, -OSO, and -COOM (wherein M represents H, a metal atom, or NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. ) are examples of the hydrophilic group. Of these, -SO3M or -COOM is preferred. R 7 The organic group in R is preferably an alkyl group. 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom may be a monovalent or divalent metal atom, such as an alkali metal (Group 1) or an alkaline earth metal (Group 2), with Na, K, or Li being preferred.

[0373] Examples of the "functional group capable of reacting by radical polymerization" in the modifying monomer (A) include groups having an ethylenically unsaturated bond, such as a vinyl group and an allyl group. The group having an ethylenically unsaturated bond is a group represented by the following formula: CX e X g =CX f R- (In the formula, X e , X f and X g are each independently F, Cl, H, CF3, CF2H, CFH2, or CH3; and R is a linking group. The linking group for R can be represented by the formula: a Preferred linking groups include -CH=CH2 and -CF=CH 2、 -CH=CF 2、 Examples include groups having an unsaturated bond such as -CF=CF2, -CH2-CH=CH2, -CF2-CF=CH2, -CF2-CF=CF2, -(C=O)-CH=CH2, -(C=O)-CF=CH2, -(C=O)-CH=CF2, -(C=O)-CF=CF2, -(C=O)-C(CH3)=CH2, -(C=O)-C(CF3)=CH2, -(C=O)-C(CH3)=CF2, -(C=O)-C(CF3)=CF2, -O-CH2-CH=CH2, -O-CF2-CF=CH2, -O-CH2-CH=CF2, and -O-CF2-CF=CF2.

[0374] The modified monomer (A) has a functional group capable of reacting in radical polymerization, and therefore, when used in the polymerization, it is presumed that it reacts with TFE in the early stage of the polymerization reaction, forming highly stable particles having hydrophilic groups derived from the modified monomer (A). Therefore, it is considered that the number of particles increases when polymerization is carried out in the presence of the modified monomer (A).

[0375] The polymerization may be carried out in the presence of one type of the modifying monomer (A), or in the presence of two or more types thereof.

[0376] In the above polymerization, a compound having an unsaturated bond can be used as the modifying monomer (A).

[0377] The modifying monomer (A) is represented by the general formula (4): CX i X k =CX j R a -(CZ 1 Z 2 ) k -Y 3 (4) (In the formula, X i , X j and X k are each independently F, Cl, H, or CF; Y 3 is a hydrophilic group; R a is a linking group; Z 1 and Z 2 are each independently H, F or CF3, and k is 0 or 1). Examples of the hydrophilic group include -NH, -PO, -PO(OM), -OPO, -OPO(OM), -SO, -OSO, and -COOM (in each formula, M represents H, a metal atom, or NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. ) are examples of the hydrophilic group. Of these, -SO3M or -COOM is preferred. R 7 The organic group in R is preferably an alkyl group. 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom may be a monovalent or divalent metal atom, such as an alkali metal (Group 1) or an alkaline earth metal (Group 2), with Na, K, or Li being preferred. By using the modifying monomer (A), an aqueous dispersion having a smaller average primary particle size and better stability can be obtained, and the aspect ratio of the primary particles can also be made smaller.

[0378] Above R a is a linking group. In this specification, the term "linking group" refers to a divalent linking group. The linking group may be a single bond and preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. There is no upper limit, but it may be, for example, 100 or less, or 50 or less. The linking group may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and may optionally contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, urethane, urea, and carbamate. The linking group may not contain carbon atoms but may be a catenary heteroatom such as oxygen, sulfur, or nitrogen.

[0379] Above R a is preferably a catenary heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group. R a When R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced with a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. a may be either linear or branched, and may be either cyclic or acyclic. a may contain functional groups (e.g., esters, ethers, ketones, amines, halides, etc.). R a may also be a non-fluorinated divalent organic group, or a partially fluorinated or perfluorinated divalent organic group. R aExamples of the hydrocarbon group include a hydrocarbon group in which no fluorine atoms are bonded to a carbon atom, a hydrocarbon group in which some of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, a hydrocarbon group in which all of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, -(C=O)-, -(C=O)-O-, or a hydrocarbon group containing -(C=O)-, which may contain an oxygen atom, a double bond, or a functional group.

[0380] R a is preferably —(C═O)—, —(C═O)—O—, or a hydrocarbon group having 1 to 100 carbon atoms which may contain an ether bond and may contain a carbonyl group, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atoms may be substituted with fluorine. R a Preferably, -(CH2) a -, -(CF2) a -, -O-(CF2) a -, -(CF2) a -O-(CF2) b -, -O(CF2) a -O-(CF2) b -, -(CF2) a -[O-(CF2) b ] c -, -O(CF2) a -[O-(CF2) b ] c -, -[(CF2) a -O] b -[(CF2) c -O] d -, -O[(CF2) a -O] b -[(CF2) c -O] d -, -O-[CF2CF(CF3)O] a -(CF2) b -, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2) a -, -(C=O)-(CF2) a -, -(C=O)-O-(CH2) a -, -(C=O)-O-(CF2) a-, -(C=O)-[(CH2) a -O] b -, -(C=O)-[(CF2) a -O] b -, -(C=O)-O[(CH2) a -O] b -, -(C=O)-O[(CF2) a -O] b -, -(C=O)-O[(CH2) a -O] b -(CH2) c -, -(C=O)-O[(CF2) a -O] b -(CF2) c -, -(C=O)-(CH2) a -O-(CH2) b -, -(C=O)-(CF2) a -O-(CF2) b -, -(C=O)-O-(CH2) a -O-(CH2) b -, -(C=O)-O-(CF2) a -O-(CF2) b At least one selected from -, -(C=O)-O-C6H4-, and combinations thereof. In the formula, a, b, c, and d are independently at least 1. a, b, c, and d may independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. The upper limit of a, b, c, and d is, for example, 100.

[0381] R aSpecific examples suitable as -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3) CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CH2-, -(C=O)-, -(C=O)-O-, -(C=O)- (CH2)-, -(C=O)-(CF2)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CF2)-, -(C=O)-[(CH2)2-O] n -, -(C=O)-[(CF2)2-O] n -, -(C=O)-O[(CH2)2-O] n -, -(C=O)-O[(CF2)2-O] n -, -(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-O[(CF2)2-O] n -(CF2)-, -(C=O)-(CH2)2-O-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-, -(C=O)-O-(CF2)2-O-(CF2)-, -(C=O)-O-C6H4-, etc. a Specifically, -CF2-O-, -CF2-O-CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2 -O-CF(CF3)CF2-O-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2)-, -(C=O)-O-(CH2)-, -(C=O)-O[(CH2)2-O] n -, -(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-(CH2)2-O-(CH2)-, or -(C=O)-O-C6H4- is preferred. In the above formula, n is an integer of 1 to 10.

[0382] -R in the above general formula (4) a -(CZ 1 Z2 ) k -としては、-CF2-O-CF2-、-CF2-O-CF(CF3)-、-CF2-OC(CF3)2-、-CF2-O-CF2-CF2-、-CF2-O-CF2-CF(CF3)-、-CF2-O-CF2-C(CF3)2-、-CF2-O-CF2CF2-CF2-、-CF2-O-CF2CF2-CF (CF3)-、-CF2-O-CF2CF2-C(CF3)2-、-CF2-O-CF(CF3)-CF2-、-CF2-O-CF(CF3)-CF(CF 3)-、-CF2-O-CF(CF3)-C(CF3)2-、-CF2-O-CF(CF3)-CF2-、-CF2-O-CF(CF3)-CF(CF3) -、-CF2-O-CF(CF3)-C(CF3)2-、-CF2-O-CF(CF3)CF2-CF2-、-CF2-O-CF(CF3)CF2-CF( CF3)-、-CF2-O-CF(CF3)CF2-C(CF3)2-、-CF2-O-CF(CF3)CF2-O-CF2-、-CF2-O-CF(CF 3)CF2-O-CF(CF3)-、-CF2-O-CF(CF3)CF2-OC(CF3)2-、-(C=O)-、-(C=O)-O-、-(C=O)- (CH2)-、-(C=O)-(CF2)-、-(C=O)-O-(CH2)-、-(C=O)-O-(CF2)-、-(C=O)-[(CH2)2-O] n -(CH2)-、-(C=O)-[(CF2)2-O] n -(CF2)-、-(C=O)-[(CH2)2-O] n -(CH2)-(CH2)-、-(C=O)-[(CF2)2-O] n -(CF2)-(CF2)-、-(C=O)-O[(CH2)2-O] n -(CF2)-、-(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-、-(C=O)-O[(CF2)2-O] n -(CF2)-、-(C=O)-O[(CF2)2-O] n-(CF2)-(CF2)-, -(C=O)-(CH2)2-O-(CH2)-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-(CH2)-, -(C=O )-O-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, -(C=O)-O-(CF2)2-O-(CF2)-C(CF3)2-, or -(C=O)-O-C6H4- C(CF3)2- is preferred, -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(C F3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, -(C=O)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CH2)-(CH2)-, -(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, or -(C=O)-O-C6H4-C(CF3)2- is more preferred. In the above formula, n is an integer of 1 to 10.

[0383] Specific examples of the compound represented by general formula (4) include: [ka] (In the formula, X j and Y 3 is the same as above. n is an integer of 1 to 10.

[0384] R a The following general formula (r1): -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g - (r1) (In the formula, X 6are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1), and a divalent group represented by the following general formula (r2): -(C=O) h -(O) i -CF2-O-(CX 7 2) e -(O) g - (r2) (where X 7 are each independently H, F or CF3, e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1. Divalent groups represented by the following formula are also preferred.

[0385] -R in the above general formula (4) a -(CZ 1 Z 2 ) k - can also be represented by the following formula (t1): -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 - (t1) (In the formula, X 6 are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, i is 0 or 1, and Z 1 and Z 2 are each independently F or CF3), and in formula (t1), Z 1 and Z 2 More preferably, one is F and the other is CF3. In addition, in the above general formula (4), -R a -(CZ 1 Z 2 ) k - is the following formula (t2): -(C=O) h -(O) i -CF2-O-(CX7 2) e -(O) g -CZ 1 Z 2 - (t2) (In the formula, X 7 are each independently H, F, or CF3, e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, i is 0 or 1, and Z 1 and Z 2 are each independently F or CF3), and in formula (t2), Z 1 and Z 2 More preferably, one is F and the other is CF3.

[0386] The compound represented by the general formula (4) is a hydrophilic group (Y 3 ), it is also preferable that the compound has a C—F bond and does not have a C—H bond. i , X j , and X k All of the are F and R a is preferably a perfluoroalkylene group having one or more carbon atoms, and the perfluoroalkylene group may be either linear or branched, may be cyclic or acyclic, and may contain at least one catenary heteroatom. The number of carbon atoms in the perfluoroalkylene group may be 2 to 20, or may be 4 to 18.

[0387] The compound represented by the general formula (4) may be partially fluorinated. That is, the compound represented by the general formula (4) may have a hydrophilic group (Y 3 ), it is also preferred that the alkyl group has at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom.

[0388] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4a). CF2=CF-O-Rf 0 -Y 3 (4a) (In the formula, Y 3is a hydrophilic group, and Rf 0 is a perfluorinated divalent linking group which may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and which optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen.

[0389] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4b). CH2=CH-O-Rf 0 -Y 3 (4b) (In the formula, Y 3 is a hydrophilic group, and Rf 0 is a perfluorinated divalent linking group defined by formula (4a).

[0390] In general formula (4), Y 3 One of the preferred embodiments is -OSO3M. 3 is -OSO3M, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(O(CF2)4CH2OSO3M), CF2=CF(OCF2CF(CF3)CH2OSO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(OCF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), CF2=CF(OCF2CF2CF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), and the like. In the above formulas, M is the same as above.

[0391] In general formula (4), Y 3 Another preferred form is -SO3M. 3is -SO3M, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2SO3M), CF2=CF(O(CF2)4SO3M), CF2=CF(OCF2CF(CF3)SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2SO3M), CH2=CH(CF2CF2SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO3M), CH2=CH((CF2)4SO3M), CH2=CH(CF2CF2SO3M), CH2=CH((CF2)3SO3M), etc. In the above formulas, M is the same as above.

[0392] In general formula (4), Y 3 -COOM is also a preferred form. 3 is -COOM, the compounds represented by general formula (4) include CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2CF2COOM), CF2=CF(O(CF2)5COOM), CF2=CF(OCF2CF(CF3)COOM), CF2=CF(OCF2CF(CF3)O(CF2) n COOM) (n is greater than 1), CH2=CH(CF2CF2COOM), CH2=CH((CF2)4COOM), CH2=CH(CF2CF2COOM), CH2=CH((CF2)3COOM), CF2=CF(OCF2CF2SO2NR'CH2COOM), CF2=CF(O(CF2)4SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)SO2NR'CH2COOM), CF2=CF(OCF2 CF(CF3)OCF2CF2SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)4SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)3SO2NR'CH2COOM), etc. In the above formula, R' is H or C 1-4 is an alkyl group, and M is the same as above.

[0393] In general formula (4), Y 3 In another preferred embodiment, Y is -OPO3M or -OP(O)(OM)2. 3 is -OPO3M or -OP(O)(OM)2, the compounds represented by general formula (4) include CF2=CF(OCF2CF2CH2OP(O)(OM)2), CF2=CF(O(CF2)4CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OP(O)(OM)2), CF2=CF(OCF2CF2SO2N(CH3) CH2CH2OP(O)(OM)2), CF2=CF(OCF2CF2CF2CF2SO2N(CH3)CH2CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2, CH2=CH((CF2)4CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2), CH2=CH((CF2)3CH2OP(O)(OM)2)- and the like. In the above formula, M is the same as above.

[0394] In general formula (4), Y 3 In another preferred embodiment, Y is -PO3M or -P(O)(OM)2. 3 is -PO3M or -P(O)(OM)2, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2P(O)(OM)2), CF2=CF(O(CF2)4P(O)(OM)2), CF2=CF(OCF2CF(CF3)P(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)4P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)3P(O)(OM)2), where M is the same as above.

[0395] The compound represented by the above general formula (4) includes compounds represented by the following general formula (5): CX2=CY(-CZ2-O-Rf-Y 3 ) (5) (In the formula, X's may be the same or different and each represent -H or -F; Y's may be -H, -F, an alkyl group or a fluorine-containing alkyl group; and Z's may be the same or different and each represent -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf's may be a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above.), a monomer represented by the following general formula (6): CX2=CY(-O-Rf-Y 3 ) (6) (In the formula, X may be the same or different and is -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above.) and a monomer represented by the following general formula (7): CX2=CY(-Rf-Y 3 ) (7) (In the formula, X may be the same or different and is -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above. Preferably, the monomer is at least one selected from the group consisting of: The fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond is an alkylene group that does not contain a structure in which an oxygen atom is at the terminal and that contains an ether bond between carbon atoms.

[0396] In the above general formula (5), X is -H or -F. Both Xs may be -F, or at least one X may be -H. For example, one X may be -F and the other may be -H, or both Xs may be -H.

[0397] In the above general formula (5), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0398] In the above general formula (5), Z may be the same or different and is —H, —F, an alkyl group or a fluoroalkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Z is preferably -H, -F or -CF3, and more preferably -F.

[0399] In the general formula (5), it is preferable that at least one of X, Y, and Z contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0400] In the general formula (5), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. The number of carbon atoms in the fluorine-containing alkylene group is preferably 2 or more. Also, it is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0401] The carbon number of the fluorine-containing alkylene group having an ether bond is preferably 3 or more. The carbon number of the fluorine-containing alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, and even more preferably 12 or less. Examples of the fluorine-containing alkylene group having an ether bond include a group represented by the following formula: [ka] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is also preferably a divalent group represented by the formula: H, F, or CF3; p1+q1+r1 is an integer of 1 to 10; s1 is 0 or 1; and t1 is an integer of 0 to 5). Specific examples of the fluorine-containing alkylene group having an ether bond include -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)- (wherein n is an integer of 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n Examples include -CF(CF3)CH2- (wherein n is an integer of 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2-, etc. The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0402] In the above general formula (5), Y 3 is -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7 are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. R 7 The organic group in R is preferably an alkyl group. 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. Above Y 3 As the alkyl group, -COOM or -SO3M is preferred, and -COOM is more preferred.

[0403] The monomer represented by the general formula (5) is preferably a monomer (5a) represented by the following general formula (5a). CH2=CF(-CF2-O-Rf-Y 3 ) (5a) (Wherein Rf and Y 3 is the same as above.)

[0404] Specific examples of the monomer represented by the general formula (5a) include those represented by the following formula:

[0405] [ka]

[0406] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is H, F, or CF3; p1+q1+r1 are integers between 0 and 10; s1 is 0 or 1; t1 is an integer between 0 and 5; Y 3 is the same as above, except for Z 3 and Z 4 are both H, then p1+q1+r1+s1 is not 0). More specifically,

[0407] [ka]

[0408] Among them,

[0409] [ka]

[0410] It is preferable that:

[0411] The monomer represented by the general formula (5a) includes, for example, Y 3 is preferably -COOM, and particularly preferably at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is as defined above), and more preferably CH2=CFCF2OCF(CF3)COOM.

[0412] The monomer represented by the general formula (5) is preferably a monomer (5b) represented by the following general formula (5b). CX 2 2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-Y 3 (5b) (In the formula, each 2 are the same and represent F or H. n5 represents 0 or an integer of 1 to 10, and Y 3 is the same as the definition above.)

[0413] In the formula (5b), n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and even more preferably 0 or 1, from the viewpoint of the stability of the resulting aqueous dispersion. 3 is preferably -COOM in that it provides adequate water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0414] Examples of the monomer represented by the above formula (5b) include CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is as defined above).

[0415] Further, examples of the monomer represented by the general formula (5) include a monomer represented by the following general formula (5c).

[0416] CF2=CFCF2-O-Rf-Y 3 (5c) (Wherein Rf and Y 3 is the same as above)

[0417] More specifically, [ka] etc.

[0418] In the above general formula (6), X is -H or -F. Both Xs may be -F, or at least one X may be -H. For example, one X may be -F and the other may be -H, or both Xs may be -H.

[0419] In the above general formula (6), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0420] In the general formula (6), it is preferable that at least one of X and Y contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0421] In the general formula (6), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. The number of carbon atoms in the fluorine-containing alkylene group is preferably 2 or more. The number of carbon atoms in the fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0422] In the above general formula (6), Y 3 is -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. R 7 The organic group in R is preferably an alkyl group. 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. Above Y 3 As the alkyl group, -COOM or -SO3M is preferred, and -COOM is more preferred.

[0423] The monomer represented by the general formula (6) is preferably at least one selected from the group consisting of monomers represented by the following general formulae (6a), (6b), (6c), (6d) and (6e): CF2=CF-O-(CF2) n1 -Y 3 (6a) (wherein n1 represents an integer of 1 to 10, as defined above). CF2=CF-O-(CF2C(CF3)F) n2 -Y 3 (6b) (wherein n2 represents an integer of 1 to 5, and Y 3 is the same as the definition above.) CF2=CF-O-(CFX 1 ) n3 -Y 3 (6c) (In the formula, X 1represents F or CF3, n3 represents an integer of 1 to 10, and Y 3 is the same as the definition above.) CF2=CF-O-(CF2CFX 1 O) n4 -(CF2) n6 -Y 3 (6d) (wherein n4 represents an integer of 1 to 10, n6 represents an integer of 1 to 3, and Y 3 and X 1 is the same as the definition above.) CF2=CF-O-(CF2CF2CFX 1 O) n5 -CF2CF2CF2-Y 3 (6e) (wherein n5 represents an integer of 0 to 10, and Y 3 and X 1 is the same as the definition above.)

[0424] In the formula (6a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0425] Examples of the monomer represented by the above formula (6a) include CF2=CF-O-CF2COOM, CF2=CF(OCF2CF2COOM), and CF2=CF(OCF2CF2CF2COOM) (wherein M is as defined above).

[0426] In the formula (6b), n2 is preferably an integer of 3 or less in terms of the stability of the resulting aqueous dispersion, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0427] In the formula (6c), n3 is preferably an integer of 5 or less in terms of water solubility, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4 in that it provides good dispersion stability.

[0428] In the above formula (6d), the above X 1 is preferably —CF3 from the viewpoint of stability of the aqueous dispersion, n4 is preferably an integer of 5 or less from the viewpoint of water solubility, and Y 3 is preferably -COOM in that it provides adequate water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4.

[0429] Examples of the monomer represented by the above formula (6d) include CF2=CFOCF2CF(CF3)OCF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2COOM, and CF2=CFOCF2CF(CF3)OCF2CF2CF2OOM (wherein M represents H, NH4, or an alkali metal).

[0430] In the general formula (6e), n5 is preferably an integer of 5 or less in terms of water solubility, and Y 3 is preferably -COOM in that it provides suitable water solubility and excellent sedimentation stability of the composition, and M is preferably H or NH4.

[0431] Examples of the monomer represented by general formula (6e) include CF2=CFOCF2CF2CF2COOM (wherein M represents H, NH4 or an alkali metal).

[0432] In the above general formula (7), Rf is preferably a fluorine-containing alkylene group having a carbon number of 1 to 40. In general formula (7), at least one of X and Y preferably contains a fluorine atom.

[0433] The monomer represented by the above general formula (7) is represented by the following general formula (7a): CF2=CF-(CF2) n1 -Y 3 (7a) (wherein n1 represents an integer of 1 to 10, and Y 3 is as defined above.) and a monomer represented by the following general formula (7b): CF2=CF-(CF2C(CF3)F) n2 -Y 3 (7b) (wherein n2 represents an integer of 1 to 5, and Y 3 is as defined above. At least one selected from the group consisting of monomers represented by Above Y 3 is preferably -SO3M or -COOM, and M is H, a metal atom, NR 7 4. It is preferably an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7 represents H or an organic group.

[0434] In the formula (7a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved. An example of the perfluorovinyl alkyl compound represented by the above formula (7a) is CF2=CFCF2COOM (wherein M is as defined above).

[0435] In the formula (7b), n2 is preferably an integer of 3 or less in terms of the stability of the resulting aqueous dispersion, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0436] The above-mentioned modifying monomer preferably contains a modifying monomer (A), and preferably contains at least one selected from the group consisting of compounds represented by general formula (5a), general formula (5b), general formula (6a), general formula (6b), general formula (6c), and general formula (6d), and more preferably contains a compound represented by general formula (5a) or general formula (5b).

[0437] When the modifying monomer contains the modifying monomer (A), the content of polymerized units based on the modifying monomer (A) is preferably in the range of 0.00001 to 1.0% by mass relative to PTFE. The lower limit is more preferably 0.0001% by mass, even more preferably 0.001% by mass, and even more preferably 0.005% by mass. The upper limits are, in order of preference, 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0438] The PTFE may have a core-shell structure, which is a conventionally known structure and is the structure of primary particles in an aqueous dispersion that can be produced by the method described in U.S. Pat. No. 6,841,594 or the like. Examples of polytetrafluoroethylene having a core-shell structure include a core-shell structure comprising a core portion of a TFE homopolymer and a shell portion of a modified PTFE, a core-shell structure comprising a core portion of a modified PTFE and a shell portion of a TFE homopolymer, and a core-shell structure comprising a core portion of a modified PTFE and a shell portion of a modified PTFE having a different monomer composition from the modified PTFE that constitutes the core portion. The PTFE having the core-shell structure can be obtained, for example, by first polymerizing TFE and, if necessary, a modified monomer to produce a core portion (TFE homopolymer or modified PTFE), and then polymerizing TFE and, if necessary, a modified monomer to produce a shell portion (TFE homopolymer or modified PTFE). The shell portion means a portion that constitutes a predetermined thickness from the surface of the PTFE primary particle to the interior of the particle, and the core portion means a portion that constitutes the interior of the shell portion.

[0439] In this specification, the core-shell structure includes all of the following: (1) a structure in which the core and shell portions have different monomer compositions; (2) a structure in which the core and shell portions have the same monomer composition but different number-average molecular weights; and (3) a structure in which the core and shell portions have different monomer compositions but different number-average molecular weights.

[0440] When the shell portion is modified PTFE, the content of the modifying monomer in the shell portion is preferably 0.00001 to 1.0% by mass, more preferably 0.0001% by mass or more, even more preferably 0.001% by mass or more, and even more preferably 0.01% by mass or more. Also, it is more preferably 0.50% by mass or less, and even more preferably 0.30% by mass or less.

[0441] When the core part is modified PTFE, the content of the modifying monomer in the core part is preferably 0.00001 to 1.0% by mass, more preferably 0.0001% by mass or more, and even more preferably 0.001% by mass or more, and more preferably 0.50% by mass or less, and even more preferably 0.30% by mass or less.

[0442] The PTFE preferably has an average primary particle diameter of 500 nm or less, more preferably 400 nm or less, and even more preferably 350 nm or less. PTFE with a small average primary particle diameter can be obtained by the manufacturing method of the present disclosure. The lower limit of the average primary particle diameter is not particularly limited, but may be, for example, 50 nm or 100 nm. From the viewpoint of molecular weight, for example, in the case of high molecular weight PTFE, it is preferably 100 nm or more, and more preferably 150 nm or more. The average primary particle size can be measured by dynamic light scattering. A PTFE aqueous dispersion adjusted to a solids concentration of approximately 1.0% by mass is prepared, and the average primary particle size is measured by dynamic light scattering at 25°C, with a solvent (water) refractive index of 1.3328 and a solvent (water) viscosity of 0.8878 mPa·s, and 70 cumulative measurements. For example, an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for the dynamic light scattering method.

[0443] The PTFE preferably has a primary particle aspect ratio of 1.45 or less, more preferably 1.40 or less, even more preferably 1.35 or less, even more preferably 1.30 or less, especially preferably 1.25 or less, particularly preferably 1.20 or less, and especially especially preferably 1.15 or less. When measuring in an aqueous dispersion, the aspect ratio is determined by observing an aqueous PTFE dispersion diluted to a solids concentration of approximately 1% by mass with a scanning electron microscope (SEM), processing images of at least 400 randomly selected particles, and averaging the ratio of their major axis to their minor axis. When measuring in powder form, the aspect ratio can be determined by irradiating modified PTFE powder with an electron beam, adding it to an aqueous fluorosurfactant solution, and redispersing it with ultrasound to obtain a modified PTFE aqueous dispersion. The aspect ratio is then determined from this modified PTFE aqueous dispersion using the same method as for measuring the aqueous dispersion.

[0444] In the above PTFE, the standard specific gravity (SSG) and melt viscosity (MV) used as indicators of molecular weight are not particularly limited.

[0445] The PTFE powder obtained by the manufacturing method of the present disclosure preferably has an average particle size (average secondary particle size) of 100 to 2000 μm. The lower limit of the average secondary particle size is more preferably 200 μm or more, and even more preferably 300 μm or more. The upper limit of the average secondary particle size is preferably 1000 μm or less, more preferably 800 μm or less, and particularly preferably 700 μm or less. The above average particle size is a value measured in accordance with JIS K 6891.

[0446] The standard specific gravity (SSG) of the PTFE is preferably 2.280 or less, more preferably 2.200, even more preferably 2.190, and even more preferably 2.180 or less. Preferably, it is 2.130 or more. The SSG is measured by the water displacement method according to ASTM D 792 using a sample molded according to ASTM D 4895-89.

[0447] The PTFE preferably has a peak temperature of 348° C. or less, more preferably 346° C. or less, even more preferably 344° C. or less, even more preferably 342° C. or less, and particularly preferably 340° C. or less. The peak temperature is a value measured by the following method. Approximately 10 mg of powder that has not been heated to temperatures above 300°C is precisely weighed, placed in a special aluminum pan, and measured using a TG / DTA (thermogravimetric differential thermal analyzer). The peak temperature is determined as the temperature corresponding to the maximum value of the differential thermal (DTA) curve when the aluminum pan is heated in an air atmosphere from 25°C to 600°C at a rate of 10°C / min.

[0448] The PTFE is preferably extruded at a pressure of 50.0 MPaG or less, more preferably 40.0 MPaG or less, and preferably at least 5.0 MPaG, more preferably at least 10.0 MPaG, and even more preferably at least 15.0 MPaG. The extrusion pressure is a value determined by the following method. 21.7 g of lubricant (trade name: Isopar H®, Exxon) was added to 100 g of PTFE powder and mixed for 3 minutes in a glass bottle at room temperature. The glass bottle was then left at room temperature (25°C) for at least 1 hour before extrusion to obtain a lubricated resin. The lubricated resin was paste-extruded through an orifice (diameter 2.5 mm, land length 11 mm, entrance angle 30°) at a reduction ratio of 100:1 at room temperature to obtain a uniform bead (extrusion molded product). The extrusion speed, i.e., ram speed, was 20 in / min (51 cm / min). The extrusion pressure was determined by measuring the load when the extrusion load reached equilibrium during paste extrusion and dividing it by the cross-sectional area of ​​the cylinder used for paste extrusion.

[0449] The PTFE generally has extensibility, fibrillation properties, and non-melt fabricability. The term "non-melt-processable" means that the melt flow rate cannot be measured at a temperature higher than the crystallization melting point in accordance with ASTM D 1238 and D 2116, that is, the polymer does not flow easily even in the melting temperature range.

[0450] In the production of the PTFE, the carboxylic acid hydrocarbon surfactant can be used within the range of use in the production method of the present disclosure. The concentration of the surfactant is not particularly limited as long as it is within the above range, but it is usually added at the start of polymerization at a concentration below the critical micelle concentration (CMC). If the amount added is too large, acicular particles with a large aspect ratio are generated, causing the aqueous dispersion to gel and losing stability. The lower limit of the amount of the carboxylic acid type hydrocarbon surfactant used is preferably 0.0001% by mass, more preferably 0.001% by mass, even more preferably 0.01% by mass, and particularly preferably 0.1% by mass, relative to the aqueous medium. The upper limit of the amount of the surfactant used is preferably 10% by mass, more preferably 5% by mass, even more preferably 3% by mass, and particularly preferably 2% by mass, relative to the aqueous medium.

[0451] The carboxylic acid type hydrocarbon surfactant may be added all at once to the reaction vessel before the start of polymerization, may be added all at once after the start of polymerization, may be added in multiple divided doses during polymerization, or may be added continuously during polymerization.

[0452] In the production of the PTFE, persulfates, organic peroxides, or mixtures thereof can be used as the radical polymerization initiator. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of organic peroxides include disuccinic acid peroxide and diglutaric acid peroxide.

[0453] As the redox polymerization initiator, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and cerium ammonium nitrate. Examples of reducing agents include bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. To increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the combination of redox initiators. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate.

[0454] Examples of the redox initiator include potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, manganese triacetate / oxalic acid, manganese triacetate / ammonium oxalate, cerium ammonium nitrate / oxalic acid, and cerium ammonium nitrate / ammonium oxalate, with potassium permanganate / oxalic acid being preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into a polymerization vessel in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, it is preferred to charge oxalic acid into a polymerization vessel and then continuously add potassium permanganate thereto.

[0455] In the production of the TFE polymer, known chain transfer agents can be used, including, for example, saturated hydrocarbons such as methane, ethane, propane, and butane; halogenated hydrocarbons such as chloromethane, dichloromethane, and difluoroethane; alcohols such as methanol and ethanol; and hydrogen. However, those that are in a gaseous state at room temperature and normal pressure are preferred.

[0456] The amount of the chain transfer agent used is usually 1 to 10,000 ppm, and preferably 1 to 5,000 ppm, based on the total amount of TFE supplied. The amount may be 1 to 1,000 ppm, or 1 to 500 ppm.

[0457] In the above-mentioned production of PTFE, a saturated hydrocarbon having 12 or more carbon atoms that is substantially inert to the reaction and becomes liquid under the above-mentioned reaction conditions can also be used as a dispersion stabilizer for the reaction system in an amount of 2 to 10 parts by mass per 100 parts by mass of the aqueous medium. Furthermore, ammonium carbonate, ammonium phosphate, or the like can be added as a buffer to adjust the pH during the reaction.

[0458] Upon completion of the PTFE polymerization, an aqueous dispersion having a solids concentration of 1.0 to 70% by mass and an average primary particle size of 50 to 500 nm can be obtained. The aqueous dispersion contains the surfactant and a fluoropolymer. Furthermore, by using the surfactant, an aqueous dispersion containing particles made of TFE polymer with a fine particle size of 0.5 μm or less can be obtained.

[0459] The polymerization step in the production of PTFE is also preferably a step including step (I) of obtaining particles containing polymerization units based on TFE, and step (II) of polymerizing TFE in an aqueous medium containing the particles obtained in step (I) to obtain PTFE. As described above, the particles are obtained in the step (I) and then TFE is polymerized in an aqueous medium containing the particles obtained in the step (I), thereby increasing the number of PTFE particles and increasing the yield.

[0460] When the polymerization step includes the step (II), the step (II) may be carried out using the aqueous dispersion containing the particles obtained in the step (I) as it is. Alternatively, the aqueous dispersion containing particles obtained in step (I) may be diluted or concentrated before step (II). The dilution or concentration may be carried out directly in the reactor, or the aqueous dispersion containing particles obtained in step (I) may be recovered from the reactor. Therefore, the polymerization step may further include a step of recovering the aqueous dispersion containing particles obtained in step (I) after step (I) and before step (II). Furthermore, after step (I) and before step (II), a step of lowering the aqueous dispersion containing the particles obtained in step (I) to a temperature of less than 50°C, less than 30°C, or less than 10°C may be included. When steps (I) and (II) are carried out consecutively, stirring can be stopped once after step (I), and then stirring can be resumed to carry out step (II) successively. Furthermore, when steps (I) and (II) are carried out continuously, after step (I), stirring may be stopped in some cases, the pressure in the reactor may be changed, stirring may be resumed, and step (II) may be subsequently carried out. In order to change the monomer composition ratio in the reactor, after step (I), the pressure in the reactor may be reduced to atmospheric pressure, and each monomer may be charged into the reactor, followed by step (II). After step (I), step (II) may be carried out successively by changing the polymerization temperature.

[0461] When the polymerization step includes the step (II), it is particularly preferable to use a redox initiator in the step (I). The use of a redox initiator can increase the particle number of the particles. When steps (I) and (II) are carried out continuously, continuous production can be achieved by stopping the supply of the redox initiator in step (I) and then supplying the polymerization initiator in step (II). Examples of the redox initiator include those mentioned above.

[0462] When the polymerization step includes the step (II), a radical polymerization initiator may be used in the step (I). The use of the radical polymerization initiator can increase the particle number of the particles. When steps (I) and (II) are carried out continuously, continuous production can be achieved by stopping the addition of the radical polymerization initiator in step (I) and then adding the polymerization initiator in step (II). Examples of radical polymerization initiators include those described below, but ammonium persulfate is preferred in step (I). Disuccinic acid peroxide is preferred in step (II). Furthermore, it is preferred to add the radical polymerization initiator continuously or intermittently in step (II).

[0463] When the polymerization step includes the step (II), the step (I) is preferably a step of obtaining an aqueous dispersion having a particle concentration of 20.0% by mass or less. The solid content concentration is more preferably 15.0% by mass or less, even more preferably 10.0% by mass or less, even more preferably 8.0% by mass or less, and particularly preferably 5.0% by mass or less. The solid content concentration is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.8% by mass or more, particularly preferably 1.0% by mass or more, and particularly preferably 1.5% by mass or more.

[0464] The particles may be a TFE homopolymer consisting only of polymerization units based on TFE, or may be a modified PTFE in which polymerization units based on TFE are 99.0% by mass or more and polymerization units based on a modifying monomer are 1.0% by mass or less. The modified PTFE preferably contains polymerized units based on a modified monomer (hereinafter also referred to as "modified monomer units") in the range of 0.00001 to 1.0% by mass. The lower limit of the modified monomer units is more preferably 0.0001% by mass, even more preferably 0.001% by mass, even more preferably 0.005% by mass, and particularly preferably 0.009% by mass. The upper limit of the modified monomer units is preferably 0.90% by mass, more preferably 0.50% by mass, even more preferably 0.40% by mass, even more preferably 0.30% by mass, even more preferably 0.10% by mass, and particularly preferably 0.05% by mass.

[0465] The particles obtained in step (I) preferably have an average primary particle size of 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less, and preferably 0.1 nm or more, more preferably 1.0 nm or more, and even more preferably 3.0 nm or more. The average primary particle size can be measured by dynamic light scattering. A PTFE aqueous dispersion adjusted to a solids concentration of approximately 1.0% by mass is prepared, and the average primary particle size is measured by dynamic light scattering at 25°C, with a solvent (water) refractive index of 1.3328 and a solvent (water) viscosity of 0.8878 mPa·s, and 70 cumulative measurements. For example, an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for the dynamic light scattering method.

[0466] The aqueous medium is a reaction medium for polymerization and refers to a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, ether, or ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower. The aqueous medium in step (II) preferably includes the aqueous medium contained in the particle-containing aqueous dispersion obtained in step (I). In addition to the aqueous medium contained in the particle-containing aqueous dispersion, other aqueous media may be added.

[0467] The polymerization temperature and polymerization pressure in the above step (II) are appropriately determined depending on the type of monomer used, the desired molecular weight of PTFE, and the reaction rate. For example, the polymerization temperature is preferably 10 to 150° C. The polymerization temperature is more preferably 30° C. or higher, and even more preferably 50° C. or higher. The polymerization temperature is more preferably 120° C. or lower, and even more preferably 100° C. or lower. The polymerization pressure is preferably 0.05 to 10 MPaG, more preferably 0.3 MPaG or more, even more preferably 0.5 MPaG or more, and more preferably 5.0 MPaG or less, even more preferably 3.0 MPaG or less. In particular, from the viewpoint of improving the yield, the pressure is preferably 1.0 MPaG or higher, and more preferably 2.0 MPaG or higher.

[0468] The above step (II) may be carried out in the presence of a carboxylic acid type hydrocarbon surfactant, or in the absence of a carboxylic acid type hydrocarbon surfactant. The step (II) is preferably a step of polymerizing TFE in an aqueous medium containing the particles in the presence of a carboxylic acid type hydrocarbon surfactant.

[0469] In the above step (II), the amount of the carboxylic acid type hydrocarbon surfactant is preferably 0.0001 to 15% by mass relative to the aqueous medium. A more preferred lower limit is 0.001% by mass, and a more preferred upper limit is 1% by mass. If the amount is less than 0.0001% by mass, the dispersing power may be insufficient, and if it exceeds 15% by mass, the effect commensurate with the amount added will not be obtained. The amount of the carboxylic acid type hydrocarbon surfactant added is determined appropriately depending on the type of monomer used, the molecular weight of the target PTFE, etc. The carboxylic acid type hydrocarbon surfactant may be added all at once to the reaction vessel before the start of polymerization, may be added all at once after the start of polymerization, may be added in multiple divided doses during polymerization, or may be added continuously during polymerization.

[0470] The step (II) preferably includes a step of continuously adding the carboxylic acid type hydrocarbon surfactant. Continuously adding the carboxylic acid type hydrocarbon surfactant means, for example, adding the carboxylic acid type hydrocarbon surfactant over time, without interruption or in portions, rather than all at once. By including the step of continuously adding the carboxylic acid type hydrocarbon surfactant, an aqueous dispersion having a smaller average primary particle size and excellent stability can be obtained.

[0471] In the above step (II), the amount of the carboxylic acid type hydrocarbon surfactant at the start of polymerization is preferably 1 ppb or more relative to the aqueous medium. The amount of the carboxylic acid type hydrocarbon surfactant at the start of polymerization is preferably 10 ppb or more, more preferably 50 ppb or more, even more preferably 100 ppb or more, and even more preferably 200 ppb or more. There is no particular upper limit, but for example, it is preferably 100,000 ppm, and more preferably 50,000 ppm. By keeping the amount of the carboxylic acid type hydrocarbon surfactant at the start of polymerization within the above range, an aqueous dispersion with a smaller average primary particle size and better stability can be obtained. It is also possible to further reduce the aspect ratio of the primary particles.

[0472] In the step (II), the step of continuously adding the carboxylic acid hydrocarbon surfactant is preferably one in which the addition of the carboxylic acid hydrocarbon surfactant to the aqueous medium is started when the concentration of PTFE formed in the aqueous medium is 10% by mass or less. The addition of the carboxylic acid hydrocarbon surfactant is more preferably started when the concentration is 8.0% by mass or less, even more preferably when it is 5.0% by mass or less, even more preferably when it is 4.0% by mass or less, especially preferably when it is 3.0% by mass or less, particularly preferably when it is 2.0% by mass or less, especially more preferably when it is 1.5% by mass or less, and especially especially preferably when it is 1.0% by mass or less. Furthermore, it is preferable to start adding when the concentration is less than 0.60% by mass, more preferably when it is 0.50% by mass or less, even more preferably when it is 0.36% by mass or less, even more preferably when it is 0.30% by mass or less, even more preferably when it is 0.20% by mass or less, and particularly preferably when it is 0.10% by mass or less. It is also preferable to start adding when the polymerization in step (II) begins. The above concentration is the concentration relative to the total of the aqueous medium and PTFE. By including the above step, an aqueous dispersion having a smaller average primary particle size and superior stability can be obtained.

[0473] In the step of continuously adding the carboxylic acid type hydrocarbon surfactant, the amount of the carboxylic acid type hydrocarbon surfactant added is preferably 0.01 to 10% by mass relative to 100% by mass of the aqueous medium, more preferably 0.05% by mass at the lower limit, even more preferably 0.1% by mass at the lower limit, more preferably 5% by mass at the upper limit, and even more preferably 1% by mass at the upper limit.

[0474] The carboxylic acid type hydrocarbon surfactant is preferably at least one selected from the group consisting of surfactant (1-0) represented by the above general formula (1-0), surfactant (a) represented by the above formula (a), surfactant (b) represented by the above formula (b), surfactant represented by formula (α), and surfactants obtained by subjecting any of these to radical treatment or oxidation treatment. When the carboxylic acid type hydrocarbon surfactant is an aliphatic carboxylic acid type hydrocarbon surfactant, the aliphatic carboxylic acid type hydrocarbon surfactant is preferably at least one selected from the group consisting of surfactants represented by formula (α), surfactants represented by the above general formula (1-0A), and surfactants obtained by subjecting these surfactants to radical treatment or oxidation treatment. When the polymerization step includes the step (II), the polymerization step preferably includes a step of subjecting the carboxylic acid type hydrocarbon surfactant to the radical treatment or oxidation treatment.

[0475] The above step (II) can be carried out, for example, by charging a polymerization reactor with an aqueous dispersion containing the particles, TFE, and optionally an aqueous medium, a modified monomer, a hydrocarbon surfactant, and other additives, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the polymerization reaction has started, additional monomers, polymerization initiators, chain transfer agents, the hydrocarbon surfactant, and the like may be added depending on the purpose. The hydrocarbon surfactant may also be added after the polymerization reaction has started. The polymerization initiator is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, it can also be combined with a reducing agent or the like to initiate polymerization as a redox. The concentration of the polymerization initiator is determined appropriately depending on the type of monomer, the molecular weight of the target PTFE, and the reaction rate. As the polymerization initiator, it is preferable to use an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator. It is preferable that the step (II) is carried out in the presence of an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator. In particular, it is preferable to use an oil-soluble peroxide or a water-soluble peroxide as the polymerization initiator, which will be described later.

[0476] The above step (II) preferably involves polymerizing TFE and, if necessary, a modified monomer, substantially in the absence of a fluorine-containing surfactant. "Substantially in the absence of a fluorine-containing surfactant" means that the fluorine-containing surfactant is present in an amount of 1 ppm or less, preferably 100 ppb or less, more preferably 10 ppb or less, and even more preferably 1 ppb or less, relative to the PTFE obtained by polymerization.

[0477] The PTFE powder (for example, PTFE fine powder) obtained by the production method of the present disclosure may be used as a powder, or may be used as an aqueous dispersion by adding the powder to water.

[0478] The resulting PTFE fine powder is suitable for molding, and suitable applications include tubes for hydraulic and fuel systems in aircraft and automobiles, flexible hoses for chemical solutions, steam, etc., and for electrical wire coating.

[0479] The obtained aqueous PTFE dispersion can also be stabilized and further concentrated by adding a nonionic surfactant, and used as a composition with an organic or inorganic filler added thereto depending on the purpose. By coating the composition on a substrate made of metal or ceramic, it is possible to obtain a coating surface that is non-sticky and has a low coefficient of friction, and that is excellent in gloss, smoothness, abrasion resistance, weather resistance, and heat resistance, and is suitable for painting rolls, cooking utensils, etc., and for impregnating glass cloth.

[0480] A PTFE organosol can also be prepared from the aqueous PTFE dispersion. The organosol can contain the PTFE and an organic solvent, such as an ether solvent, a ketone solvent, an alcohol solvent, an amide solvent, an ester solvent, an aliphatic hydrocarbon solvent, an aromatic hydrocarbon solvent, or a halogenated hydrocarbon solvent. N-methyl-2-pyrrolidone, dimethylacetamide, or the like is preferably used. The organosol can be prepared, for example, by the method described in International Publication No. 2012 / 002038.

[0481] The aqueous PTFE dispersion or the PTFE fine powder is also preferably used as a processing aid. When used as a processing aid, the aqueous dispersion or the fine powder is mixed with a host polymer or the like to improve the melt strength during melt processing of the host polymer, and the mechanical strength, electrical properties, flame retardancy, anti-dripping properties during combustion, and sliding properties of the resulting polymer.

[0482] The above-mentioned aqueous dispersion of PTFE or the above-mentioned PTFE fine powder is also preferably used as a binder for batteries and for dust prevention purposes.

[0483] The above-mentioned aqueous dispersion of PTFE or the above-mentioned PTFE fine powder is also preferably used as a processing aid after being compounded with a resin other than PTFE. The above-mentioned aqueous dispersion or the above-mentioned fine powder is suitable as a raw material for PTFE, for example, as described in JP-A-11-49912, U.S. Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980. Processing aids using the above-mentioned aqueous dispersion or the above-mentioned fine powder are in no way inferior to the processing aids described in the above-mentioned publications.

[0484] Also preferably, the aqueous dispersion of above-mentioned PTFE is mixed with the aqueous dispersion of melt-processable fluororesin to be coagulated, and form coprecipitated powder.Above-mentioned coprecipitated powder is suitable as processing aid.

[0485] Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, ethylene / TFE / HFP copolymer [EFEP], etc., with FEP being preferred.

[0486] The aqueous dispersion preferably contains the melt-processable fluororesin. Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, and EFEP. The aqueous dispersion containing the melt-processable fluororesin can be used as a coating material. The melt-processable fluororesin can sufficiently fuse the TFE polymer particles together, improving film-forming properties and imparting gloss to the resulting coating.

[0487] The fluorine-free resin that adds above-mentioned coprecipitated powder can be powder, can be pellet, can be emulsion.In order to thoroughly mix each resin, it is preferable to add above-mentioned by known method such as extrusion kneading, roll kneading, etc., while applying shearing force.

[0488] The use of the aqueous dispersion is not particularly limited, and examples of applications of the aqueous dispersion as it is include coating, which involves applying the dispersion to a substrate, drying, and optionally firing; impregnation, which involves impregnating a porous support such as a nonwoven fabric or a resin molded product, drying, and preferably firing; and cast film formation, which involves applying the dispersion to a substrate such as glass, drying, and optionally immersing the substrate in water, and peeling the substrate off to obtain a thin film. Examples of these applications include aqueous dispersion-type paints, tent films, conveyor belts, printed circuit boards (CCL), electrode binders, and electrode water repellents.

[0489] The aqueous dispersion can be used as an aqueous coating material by blending known compounding agents such as pigments, thickeners, dispersants, antifoaming agents, antifreezing agents, and film-forming aids, or by further combining it with other polymer compounds. As an additive, it can be used as a binder to prevent the active material of an electrode from falling off, as a compound such as an anti-drip agent, or as a dust suppression treatment to prevent the scattering of soil, sand, dust, etc.

[0490] An anionic surfactant may be preferably contained in order to adjust the viscosity of the aqueous dispersion or to improve the miscibility of pigments, fillers, etc. The anionic surfactant may be added as appropriate within an economically and environmentally acceptable range.

[0491] The anionic surfactant may be a non-fluorinated anionic surfactant or a fluorine-containing anionic surfactant, but a non-fluorinated anionic surfactant that does not contain fluorine, that is, a hydrocarbon anionic surfactant, is preferred.

[0492] For the purpose of adjusting viscosity, any known anionic surfactant may be used without particular limitation. For example, anionic surfactants described in International Publication Nos. 2013 / 146950 and 2013 / 146947 may be used. Examples include anionic surfactants having a saturated or unsaturated aliphatic chain containing 6 to 40 carbon atoms, preferably 8 to 20 carbon atoms, and more preferably 9 to 13 carbon atoms. The saturated or unsaturated aliphatic chain may be either a linear or branched chain, or may have a cyclic structure. The hydrocarbon may be aromatic or may have an aromatic group. The hydrocarbon may have a heteroatom such as oxygen, nitrogen, or sulfur. Examples of anionic surfactants include alkyl sulfonates, alkyl sulfates, alkylaryl sulfates, and salts thereof; aliphatic (carboxylic) acids and salts thereof; alkyl phosphates, alkylaryl phosphates, and salts thereof; and among these, alkyl sulfonates, alkyl sulfates, aliphatic carboxylic acids, and salts thereof are preferred. The alkyl sulfate or its salt is preferably ammonium lauryl sulfate or sodium lauryl sulfate. The aliphatic carboxylic acid or a salt thereof is preferably succinic acid, decanoic acid, undecanoic acid, undecenoic acid, lauric acid, hydrododecanoic acid, or a salt thereof.

[0493] The amount of anionic surfactant added varies depending on the type of anionic surfactant and other compounding ingredients, but is preferably 10 ppm to 5000 ppm based on the solid mass of the fluoropolymer. The lower limit of the amount of anionic surfactant added is more preferably 50 ppm or more, and even more preferably 100 ppm or more. If the amount added is too small, the viscosity adjusting effect is poor. The upper limit of the amount of anionic surfactant added is more preferably 3000 ppm or less, and even more preferably 2000 ppm or less. If the amount added is too large, the mechanical stability and storage stability of the aqueous dispersion may be impaired.

[0494] For the purpose of adjusting the viscosity of the aqueous dispersion, in addition to the anionic surfactant, for example, methyl cellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer, etc. may be blended. For the purpose of adjusting the pH of the aqueous dispersion, a pH adjuster such as aqueous ammonia may be added.

[0495] The aqueous dispersion may contain other water-soluble polymer compounds as needed, provided that the characteristics of the aqueous dispersion are not impaired. The other water-soluble polymer compounds are not particularly limited and include, for example, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinylpyrrolidone (dispersion stabilizer), phenol resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, polyurethane resin, etc. Furthermore, preservatives such as isothiazolones, azoles, pronopol, chlorothalonil, methylsulfonyltetrachloropyrrolidone, carbentazim, fluorophorbet, sodium diacetate, and diiodomethyl-paratolyl sulfone may be contained.

[0496] The aqueous dispersion of PTFE is also preferably used as a dust-suppressing treatment agent. The dust-suppressing treatment agent can be used in a method of suppressing dust from a dust-generating substance by mixing it with a dust-generating substance and subjecting the mixture to a compression-shear action at a temperature of 20 to 200°C to fibrillate the TFE polymer, for example, in the methods described in Japanese Patent No. 2827152 and Japanese Patent No. 2538783. The above-mentioned aqueous dispersion of PTFE can be suitably used, for example, in the dust suppression treatment composition described in WO 2007 / 004250, and can also be suitably used in the dust suppression treatment method described in WO 2007 / 000812.

[0497] The dust suppression treatment agent is suitable for use in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill disposal of incineration ash and hazardous substances, explosion prevention, cosmetics, and dust suppression treatment of sand for pet excretion, such as cat litter.

[0498] The aqueous PTFE dispersion is also preferably used as a raw material for obtaining TFE polymer fibers by the dispersion spinning method, which involves mixing the aqueous TFE polymer dispersion with an aqueous matrix polymer dispersion, extruding the mixture to form an intermediate fiber structure, and firing the intermediate fiber structure to decompose the matrix polymer and sinter the TFE polymer particles, thereby obtaining TFE polymer fibers.

[0499] The production method of the present disclosure can also produce high-molecular-weight PTFE. The production method of the present disclosure can produce PTFE having a molecular weight equivalent to that of a production method that uses a conventional fluorine-containing surfactant, even without using a conventional fluorine-containing surfactant. When producing high molecular weight PTFE, the polymerization temperature is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher. The polymerization temperature is preferably 100° C. or lower, and more preferably 95° C. or lower. The polymerization pressure is preferably 0.5 MPaG or higher, preferably 0.7 MPaG or higher, and preferably 1.0 MPaG or higher, and is preferably 5.0 MPaG or lower, more preferably 4.0 MPaG or lower, and even more preferably 3.0 MPaG or lower.

[0500] The high-molecular-weight PTFE powder obtained by polymerization has extensibility and non-melt processability, and is also useful as a raw material for extruded bodies (porous bodies). When this extruded body is a membrane (extruded PTFE membrane or porous PTFE membrane), it can be extruded by a known PTFE extrusion method. By extrusion, the high-molecular-weight PTFE is easily fibrillated, forming a PTFE porous body (membrane) consisting of nodes and fibers. Preferably, a sheet-like or rod-like paste extrudate is roll-stretched in the extrusion direction to obtain a uniaxially stretched film. Furthermore, a biaxially stretched film can also be obtained by stretching the film in the width direction using a tenter or the like. It is also preferable to carry out a semi-baking treatment before stretching.

[0501] This expanded PTFE body is a porous body with a high porosity, The membrane can be suitably used as a filter medium for various precision filters such as air filters and chemical filters, and as a support material for polymer electrolyte membranes. It is also useful as a material for products used in the fields of textiles, medicine, electrochemicals, sealing materials, air filtration, ventilation / internal pressure adjustment, liquid filtration, and general consumer goods. Specific examples of applications are given below.

[0502] Electrochemical field Dielectric material prepreg, EMI shielding material, heat transfer material, etc. More specifically, printed wiring boards, electromagnetic shielding materials, insulating heat transfer materials, insulating materials, etc. Sealing materials field Gaskets, packing, pump diaphragms, pump tubes, aircraft sealing materials, etc.

[0503] Air Filtration ULPA filters (for semiconductor manufacturing), HEPA filters (for hospitals and semiconductor manufacturing), cylindrical cartridge filters (for industrial use), bag filters (for industrial use), heat-resistant bag filters (for exhaust gas treatment), heat-resistant pleated filters (for exhaust gas treatment), SINBRAN filters (for industrial use), catalytic filters (for exhaust gas treatment), adsorbent filters (for HDD integration), adsorbent vent filters (for HDD integration), vent filters (for HDD integration and others), vacuum cleaner filters (for vacuum cleaners), general-purpose multi-layer felt material, GT cartridge filters (for GT compatible products), cooling filters (for electronic equipment housings), etc.

[0504] Ventilation / internal pressure regulation field Freeze-drying materials such as freeze-drying containers, automotive ventilation materials for electronic circuits and lamps, container applications such as container caps, protective ventilation applications for electronic devices including small terminals such as tablet devices and mobile phones, medical ventilation applications, etc.

[0505] Liquid Filtration Semiconductor liquid filtration filters (for semiconductor manufacturing), hydrophilic PTFE filters (for semiconductor manufacturing), chemical filters (for chemical liquid treatment), filters for pure water production lines (for pure water production), backwash type liquid filtration filters (for industrial wastewater treatment), etc.

[0506] General consumer goods Clothing, cable guides (movable wires for motorcycles), motorcycle clothing, cast liners (medical supporters), vacuum cleaner filters, bagpipes (musical instruments), cables (guitar signal cables, etc.), strings (for stringed instruments), etc.

[0507] Textile field PTFE fiber (textile material), sewing thread (textile), weaving thr...

Claims

1. A step of changing the fluorine-containing compound represented by general formula (1A) in the aqueous fluoropolymer dispersion, which is obtained by polymerization using a carboxylic acid-type hydrocarbon surfactant and contains a fluorine-containing compound represented by the following general formula (1), by adding an acid to adjust the pH to 4.0 or less. A step (A1) to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A) by coagulation, and The process includes a step (B1) of heat-treating the wet fluoropolymer powder at a temperature of 170°C to 230°C. A method for producing fluoropolymer powder characterized by the following: General formula (1): (H-(CF 2 ) m -COO) p M 1 General formula (1A): H-(CF) ２ ) ｍ -COOH (In the formula, m is 3 to 19, M1 is H, a metal atom, NR54 (R5 may be the same or different, and is either H or an organic group having 1 to 10 carbon atoms), optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. p is 1 or 2.)

2. The method for producing the wet fluoropolymer powder according to claim 1, comprising two or more fluorine-containing compounds represented by general formula (1A).

3. The method for producing the wet fluoropolymer powder according to claim 1 or 2, wherein the wet fluoropolymer powder substantially does not contain a salt of a fluorine-containing compound represented by general formula (1A).

4. The manufacturing method according to any one of claims 1 to 3, wherein the fluoropolymer is polytetrafluoroethylene.

5. A step of converting the fluorine-containing compound represented by general formula (1A) in the aqueous fluoropolymer dispersion, which is obtained by polymerization using an aliphatic carboxylic acid-type hydrocarbon surfactant and contains a fluorine-containing compound represented by the following general formula (1), by adding an acid to adjust the pH to 4.0 or less, A step (A2) to obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A) by coagulation, The process includes a step (B2) of heat-treating the wet fluoropolymer powder at a temperature of 170°C to 230°C. A method for producing fluoropolymer powder characterized by the following: General formula (1): (H-(CF 2 ) m -COO) p M 1 General formula (1A): H-(CF) ２ ) ｍ -COOH (In the formula, m is 3 to 19, M1 is H, a metal atom, NR54 (R5 may be the same or different, and is either H or an organic group having 1 to 10 carbon atoms), optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. p is 1 or 2.)

6. The method for producing the wet fluoropolymer powder according to claim 5, comprising two or more fluorine-containing compounds represented by general formula (1A).

7. The method for producing the wet fluoropolymer powder according to claim 5 or 6, wherein the wet fluoropolymer powder substantially does not contain a salt of a fluorine-containing compound represented by general formula (1A).

8. The manufacturing method according to any one of claims 5 to 7, wherein the fluoropolymer is polytetrafluoroethylene.