Method for manufacturing fluoropolymer molded articles

Abstract

General formula: [C5F 11 COO - M + (wherein, M + represents a cation.) To provide a production method capable of producing a fluoropolymer molded body with a reduced content of a fluorine-containing compound represented by the formula. 【Solution means】 A molded body containing a fluoropolymer and a fluorine-containing compound having a hydrophilic group is heat-treated at a temperature lower than the melting point of the fluoropolymer to produce a molded body with a reduced content of the fluorine-containing compound having a hydrophilic group. A method for producing a fluoropolymer molded body, wherein the molded body contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, and the fluorine-containing compound having a hydrophilic group has the general formula: [C5F 11 COO - M + (wherein, M + represents a cation.) To provide a method for producing a fluoropolymer molded body which is a fluorine-containing compound represented by the formula.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing a fluoropolymer molded article. [Background technology]

[0002] Patent Document 1 describes a method for producing recycled fluororesin, which includes a step of heat-treating a melt-molded used fluororesin molded product at a temperature of 200°C or higher but below its melting point. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2002-36237 [Overview of the project] [Problems that the invention aims to solve]

[0004] In this disclosure, the general formula is:[C5F 11 COO - ]M + (In the formula, M + The objective is to provide a manufacturing method that can produce a fluoropolymer molded article in which the content of fluorine-containing compounds represented by ( ) is reduced. [Means for solving the problem]

[0005] According to this disclosure, a method for producing a fluoropolymer molded article in which the content of the hydrophilic fluorine-containing compound is reduced is produced by heat-treating a molded article containing a fluoropolymer and a hydrophilic fluorine-containing compound at a temperature below the melting point of the fluoropolymer, wherein the molded article contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, and the hydrophilic fluorine-containing compound is of the general formula:[C5F 11 COO - ]M+ (where M + represents a cation.) A method for producing a fluoropolymer molded body, which is a fluorine-containing compound represented by the formula, is provided. [Advantages of the Invention]

[0006] According to the present disclosure, the general formula: [C5F 11 COO - M + (where M + represents a cation.) A production method capable of producing a fluoropolymer molded body with a reduced content of the fluorine-containing compound represented by the formula can be provided. [Embodiments for Carrying Out the Invention]

[0007] Hereinafter, specific embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0008] Patent Document 1 describes that by using a used fluororesin molded product that has been melt-molded as a raw material and using the above-described production method, a recycled fluororesin in which impurities such as chemical solutions and chemicals have been removed to the same extent as the fluororesin before use can be produced.

[0009] However, depending on the molding conditions, the fluoropolymer molded body may contain a fluorine-containing compound represented by the general formula: [C5F 11 COO - M + (where M + represents a cation.)

[0010] In other words, the present disclosure is a method for producing a fluoropolymer molded article in which the content of the hydrophilic fluorine-containing compound is reduced by heat-treating a molded article containing a fluoropolymer and a hydrophilic fluorine-containing compound at a temperature below the melting point of the fluoropolymer, wherein the molded article contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, and the hydrophilic fluorine-containing compound is of the general formula:[C5F 11 COO - ]M + (In the formula, M + The '(')' represents a cation. This is a method for producing a fluoropolymer molded article which is a fluorine-containing compound represented by '(').

[0011] Next, the manufacturing method of this disclosure will be described in more detail.

[0012] (A molded article containing a fluorine-containing compound having a hydrophilic group) The molded article subjected to heat treatment in the manufacturing method of this disclosure contains a fluorine-containing compound having a hydrophilic group.

[0013] The hydrophilic group of the fluorine-containing compound is preferably anionic group such as an acidic group, for example, -NH2, -PO3M, -OPO3M, -SO3M, -OSO3M, and -COOM (where M represents a cation in each formula). Among the above hydrophilic groups, -SO3M or -COOM is preferred, and -COOM is more preferred. As for the cation, H + Examples include ammonium ions, alkali metal ions, and alkaline earth metal ions.

[0014] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula. General formula: [C5F 11 COO - ]M + (In the formula, M +(This represents a cation.)

[0015] General formula in molded articles subjected to heat treatment: [C5F 11 COO - ]M + The content of the compound represented by may be 5 ppb by mass or more, 15 ppb by mass or more, 25 ppb by mass or more, 30 ppb by mass or more, 35 ppb by mass or more, 40 ppb by mass or more, 45 ppb by mass or more, or 50 ppb by mass or more, and may be 1000 ppb by mass or less, or 500 ppb by mass or less.

[0016] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula. General formula: [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 8 and 14, M + (This represents a cation.)

[0017] General formula in a molded body subjected to heat treatment: [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 8 and 14, M + represents a cation. The content of the compound represented by ) may be 1 ppb by mass or more, 2 ppb by mass or more, 3 ppb by mass or more, 4 ppb by mass or more, or 5 ppb by mass or more, and may be 1000 ppb by mass or less, or 500 ppb by mass or less. n may be an integer from 9 to 14.

[0018] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula. General formula: [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 11 and 14, M + (This represents a cation.)

[0019] The molded body subjected to heat treatment contains the general formula: [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 11 and 14, M + ' represents a cation.' The content of the compound represented by ') may be 1 ppb by mass or more, 2 ppb by mass or more, 3 ppb by mass or more, 4 ppb by mass or more, or 5 ppb by mass or more, and may be 1000 ppb by mass or less, or 500 ppb by mass or less.

[0020] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula (H1). General formula (H1):[X-Rf-A - ] i M i+ (wherein X is H, Cl, Br, F or I, Rf is a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain, or a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain interrupted by at least one oxygen atom, A - is an acid group, M i+ (where i is a cation with a valency of i, and i is an integer between 1 and 3)

[0021] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, represented by the following general formula (H2). General formula (H2):[C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 4 and 14, M + (This represents a cation.)

[0022] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, represented by the following general formula (H3). General formula (H3):[R 1 -OL-CO2 - ]M + (In the formula, R 1 L is a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain, or a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain interrupted by at least one oxygen atom, L is a non-fluorinated, partially fluorinated or fully fluorinated alkylene group of a linear or branched chain, M + (This represents a cation.)

[0023] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the general formula (H4). General formula (H4):H-Rf n0 -Y 0 (In the formula, Rf n0 This is an alkylene group having 3 to 20 carbon atoms, being linear, branched, or cyclic, in which some or all of the hydrogen atoms are substituted with fluorine, and the alkylene group may contain one or more ether bonds, and some of the hydrogen atoms may be substituted with chlorine. 0 (This is an anionic group.)

[0024] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula (H5). General formula (H5):[A - -Rf h0 -A - ] i M k+ M l+ (In the formula, Rf h0 A is a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain, or a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain interrupted by at least one oxygen atom, A - is an acid group, M k+ M is a cation having a valency k. l+ (where i is a cation with a valency of l, i is an integer between 1 and 3, and k and l are integers between 0 and 3, never both being 0, and representing integers such that k + l = i.)

[0025] In one embodiment, the molded article subjected to heat treatment contains a fluorine-containing compound having a hydrophilic group, which is represented by the following general formula (H6). General formula (H6):[ - OCOC n-1 F 2n-2 COO - ]M1 + M2 + (In the formula, n is an integer between 4 and 14, M1 + M2 + (This represents a cation.)

[0026] The content of hydrophilic fluorine-containing compounds in the molded article subjected to heat treatment may be 5 ppb by mass or more, 15 ppb by mass or more, 25 ppb by mass or more, 30 ppb by mass or more, 35 ppb by mass or more, 40 ppb by mass or more, 45 ppb by mass or more, or 50 ppb by mass or more, and may be 1000 ppb by mass or less, or 500 ppb by mass or less.

[0027] The content of hydrophilic fluorine-containing compounds in molded articles can be quantified by known methods. For example, it can be quantified by LC / MS analysis. First, the molded body is freeze-dried to prepare a powder. Methanol is added to the obtained powder, and extraction is performed. The resulting extract is then analyzed by LC / MS. To further improve the extraction efficiency, treatments such as Soxhlet extraction and sonication may be performed. The obtained extract is concentrated by nitrogen purging as appropriate, and fluorine-containing compounds in the concentrated extract are measured by LC / MS. From the obtained LC / MS spectrum, molecular weight information is extracted and its agreement with the structural formula of a candidate fluorine-containing compound having a hydrophilic group is confirmed. Subsequently, aqueous solutions containing five or more levels of the identified hydrophilic fluorine-containing compound were prepared. LC / MS analysis was performed on each aqueous solution with its respective content, and the relationship between the content and the area of ​​the solution was plotted to create a calibration curve. Furthermore, using a calibration curve, the area of ​​the LC / MS chromatogram of the hydrophilic fluorine-containing compound in the extract can be converted to the content of the hydrophilic fluorine-containing compound. Furthermore, since the obtained extract can be concentrated by purging with nitrogen, the lower limit of quantification in the measurement method can be lowered.

[0028] In the manufacturing method of this disclosure, the shape of the molded article subjected to heat treatment is not particularly limited. In one embodiment, the molded article subjected to heat treatment has a shape suitable for the application in which the fluoropolymer molded article is used. In one embodiment, the molded article subjected to heat treatment may be, for example, a nut, bolt, fitting, film, bottle, gasket, wire insulation, tube, hose, pipe, valve, seat, seal, packing, tank, roller, container, cock, connector, filter housing, filter cage, flow meter, pump, wafer carrier, wafer box, etc. The molded article subjected to heat treatment may be a molded article (except pellets). The maximum length of the molded article subjected to heat treatment may be, for example, 0.1 mm to 100 cm, or 1 mm to 50 cm. A molded article that is too large can be crushed before being subjected to heat treatment.

[0029] The molded articles subjected to heat treatment may be unused or used. An unused molded article is one that has never been used since being manufactured by molding of fluoropolymer, maintains its shape after molding, has no change in the physical properties of the fluoropolymer forming the article, and has no surface contamination. On the other hand, a used molded article is one that has been used in a high-temperature environment, has come into contact with water or chemicals, or has been used outdoors, resulting in deformation from its shape after molding, deterioration of the fluoropolymer forming the article, or surface contamination. If a used molded article is dirty, it may be cleaned with a cleaning solution before being subjected to heat treatment.

[0030] Molded articles subjected to heat treatment are typically molten articles obtained by melt-molding fluoropolymers. It has now been found that molten articles containing fluoropolymers containing fluorine-containing ether monomer units contain fluorine-containing compounds having hydrophilic groups. This is presumed to be because, during molding, heat and shear forces are applied to the fluoropolymer, making it easier for the CO bonds in the fluorine-containing ether monomer units to break. Therefore, it is presumed that fluoropolymers containing fluorine-containing ether monomer units are more likely to generate fluorine-containing compounds having hydrophilic groups with the heat and shear forces required for melt-molding in the production of molded articles compared to fluoropolymers that do not contain fluorine-containing ether monomer units, such as copolymers of tetrafluoroethylene and ethylene. By using the manufacturing method of this disclosure, even if the molded article contains a fluoropolymer containing fluorine-containing ether monomer units and is obtained by melt-molding, it is possible to produce a molded article with a reduced content of fluorine-containing compounds having hydrophilic groups.

[0031] Molding methods for producing molten articles include extrusion molding, injection molding, compression molding, blow molding, transfer molding, roto molding, and roto lining molding. In extrusion molding, injection molding, blow molding, and transfer molding, not only heat but also shear force is applied to the fluoropolymer, so it is presumed that the resulting molded articles tend to contain a small amount of fluorine-containing compounds with hydrophilic groups. In particular, injection molding requires the fluoropolymer to be passed through a narrow gate and to fill every corner of the mold before the resin cools and solidifies, which tends to apply a large shear force to the fluoropolymer. According to the manufacturing method of this disclosure, even when using an extruded article obtained by extruding a fluoropolymer, an injection-molded article obtained by injection molding a fluoropolymer, a blow-molded article obtained by blow molding a fluoropolymer, or a transfer-molded article obtained by transfer molding a fluoropolymer as the molded article to be subjected to heat treatment, it is possible to produce a molded article with a reduced content of fluorine-containing compounds with hydrophilic groups. These molten articles may be crushed, and the crushed articles may be subjected to heat treatment.

[0032] In one embodiment, the molded article subjected to heat treatment contains components other than fluoropolymers and fluorine-containing compounds having hydrophilic groups (hereinafter sometimes referred to as "other components"). In one embodiment, the molded article subjected to heat treatment substantially does not contain other components. In one embodiment, the molded article subjected to heat treatment contains no other components at all, or contains only trace amounts of other components (for example, less than 0.1% by mass or less than 0.01% by mass) relative to the mass of the molded article.

[0033] Other components include fillers, plasticizers, processing aids, mold release agents, pigments, flame retardants, lubricants, light stabilizers, weather stabilizers, conductive agents, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, fragrances, oils, softeners, and hydrofluoricating agents.

[0034] In the manufacturing method of this disclosure, the molded article containing the fluoropolymer may be subjected to heat treatment without being pulverized, or the molded article containing the fluoropolymer may be pulverized and the pulverized molded article may be subjected to heat treatment.

[0035] Crushing refers to the process of dividing raw materials using energy to reduce their size (volume). Examples of energy sources include compression, impact, collision, shear, and abrasion. Examples of crushing by compression include jaw crushers, gyrant rerry crushers, cone crushers, and roll crushers. Examples of crushing by collision include hammer mills, pin mills, and mill grinders. Examples of crushing by collision include jet mills and ball mills. Examples of crushing by shear include single-screw pusher crushers, granulators, plastic runner crushers, cutter mills, shredders, and guillotine cutters. Examples of crushing by abrasion include disc mills and millstones. Some of these processes involve not just one type of energy but a combination of multiple energies. Fluoropolymers are soft and tend to stretch thinly when subjected to friction under stress, so shear-type crushing is preferable as it minimizes this stretching. Among shear-type crushing machines, single-screw pusher crushers, granulators, and plastic runner crushers are preferred because they minimize friction while applying stress.

[0036] The crushing process may be performed once or repeatedly until a molded body of the desired shape can be produced. The crushed molded body may also be classified by known methods such as airflow classification.

[0037] The shape of the crushed molded body is not particularly limited and may be particulate, granular, or other shapes. The maximum length of a single piece of the crushed molded body may be, for example, 0.1 to 50 mm or 1 to 15 mm.

[0038] (Heat treatment) In the manufacturing method of the present disclosure, a molded article containing a fluoropolymer and a fluorine-containing compound having hydrophilic groups is heat-treated at a temperature below the melting point of the fluoropolymer to produce a molded article in which the content of the fluorine-containing compound having hydrophilic groups is reduced.

[0039] The heat treatment temperature is below the melting point of the fluoropolymer. By performing heat treatment at a temperature below the melting point of the fluoropolymer, the content of fluorine-containing compounds with hydrophilic groups can be reduced while maintaining the shape of the molded product.

[0040] The heat treatment temperature is preferably below the melting point of the fluoropolymer -10°C, more preferably below the melting point of the fluoropolymer -50°C, even more preferably below the melting point of the fluoropolymer -100°C, preferably above 50°C, more preferably above 100°C, even more preferably above 150°C, and still more preferably above 180°C. In one embodiment, the heat treatment temperature may be 300°C or less, 260°C or less, or less than 230°C.

[0041] The heat treatment time varies depending on the size of the molded body, but is preferably 1 second or more, more preferably 3 seconds or more, even more preferably 10 seconds or more, even more preferably 30 seconds or more, and particularly preferably 1 minute or more. There is no particular upper limit, but is preferably 24 hours or less. The heat treatment time may also be 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 40 minutes or more, or 50 minutes or more.

[0042] The heat treatment can be carried out in air or an inert gas. In one embodiment, the molded body can be heat-treated by bringing it into contact with hot air. In one embodiment, the molded body can be heat-treated by leaving it stationary in a heat treatment apparatus. In one embodiment, the molded body can be heat-treated while circulating hot air within the heat treatment apparatus. As the heat treatment apparatus, an electric furnace, a constant temperature bath, a dryer, a heat treatment furnace, etc., can be used. In one embodiment, the molded body can be continuously supplied to and discharged from the heat treatment apparatus while the heat treatment is carried out.

[0043] (Fluoropolymer) In the manufacturing method of the present disclosure, the molded article subjected to heat treatment contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units.

[0044] The fluoropolymers described above are melt-processable and are typically melt-processable fluororesins. Melt-processability means that the polymer can be melted and processed using conventional processing equipment such as extruders and injection molding machines.

[0045] The perfluorovinyl ether unit is a monomer unit based on perfluorovinyl ether. Examples of perfluorovinyl ether include: General formula (1): CF2=CF-ORf 1 (In the formula, Rf 1 ) represents a perfluoroorganic group. Examples include fluoromonomers represented by ).

[0046] As the perfluoro organic group, a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms is preferable, a perfluoroalkyl group having 1 to 6 carbon atoms is preferable, and a perfluoroalkyl group having 1 to 3 carbon atoms is preferable. Examples of the perfluoro organic group include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, and the like.

[0047] As the perfluorovinyl ether, at least one selected from the group consisting of perfluoro(methyl vinyl ether) (CF2=CF-O-CF3), perfluoro(ethyl vinyl ether) (CF2=CF-O-C2F5), and perfluoro(propyl vinyl ether) (CF2=CF-O-C3F7) is preferable, and at least one selected from the group consisting of perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) is more preferable.

[0048] The perfluoroallyl ether unit is a monomer unit based on perfluoroallyl ether. Examples of the perfluoroallyl ether include General formula (2): CF2=CF-CF2-ORf 2 (In the formula, Rf 2 represents a perfluoro organic group.) Fluoromonomers represented by the formula are included.

[0049] Rf in general formula (2) 2 is the same as Rf in general formula (1) 1 . As the perfluoroallyl ether, 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 is preferable, 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 is more preferable, and CF2=CF-CF2-O-CF2CF2CF3 is even more preferable.

[0050] As the fluoropolymer containing fluorine-containing ether monomer units, at least one selected from the group consisting of tetrafluoroethylene / fluorine-containing ether monomer copolymers and tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymers is preferred.

[0051] The content of fluorine-containing ether monomer units in the fluoropolymer is preferably 0.1 to 12.0% by mass, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, still more preferably 1.5% by mass or more, particularly preferably 2.0% by mass or more, more preferably 10.0% by mass or less, and still more preferably 8.0% by mass or less, relative to the total monomer units of the fluoropolymer.

[0052] The content of fluorine-containing ether monomer units in the tetrafluoroethylene / fluorine-containing ether monomer copolymer is preferably 1.0 to 12.0% by mass, more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, still more preferably 2.5% by mass or more, more preferably 10.0% by mass or less, and still more preferably 8.0% by mass or less, relative to the total monomer units of the polymer.

[0053] The content of tetrafluoroethylene units in the tetrafluoroethylene / fluorine-containing ether monomer copolymer is preferably 88.0 to 99.0% by mass or more, more preferably 90.0% by mass or more, even more preferably 92.0% by mass or more, preferably 98.5% by mass or less, more preferably 98.0% by mass or less, and even more preferably 97.5% by mass or less, relative to the total monomer units of the polymer.

[0054] In one embodiment, the tetrafluoroethylene / fluorine-containing ether monomer copolymer does not contain hexafluoropropylene units, or contains less than 0.1% by mass of hexafluoropropylene units relative to the total monomer units of the polymer. In another embodiment, the tetrafluoroethylene / fluorine-containing ether monomer copolymer contains only tetrafluoroethylene units and fluorine-containing ether monomer units.

[0055] The content of fluorine-containing ether monomer units in the tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer is preferably 0.1 to 20.0% by mass, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 10.0% by mass or less, and even more preferably 3.0% by mass or less, relative to the total monomer units of the polymer.

[0056] The content of tetrafluoroethylene units in the tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer is preferably 70.0 to 99.8% by mass, more preferably 75.0% by mass or more, even more preferably 80.0% by mass or more, more preferably 98.0% by mass or less, and even more preferably 97.0% by mass or less, relative to the total monomer units of the polymer.

[0057] The content of hexafluoropropylene units in the tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer is preferably 0.1 to 25.0% by mass, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 20.0% by mass or less, and even more preferably 15.0% by mass or less, relative to the total monomer units of the polymer.

[0058] Fluoropolymers may contain monomers other than fluorine-containing ether monomer units, tetrafluoroethylene units, and hexafluoropropylene units. Other monomers include vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, and CZ.1 Z 2 = CZ 3 (CF2) n Z 4 (wherein, Z 1 , Z 2 and Z 3 are the same or different and represent H or F, and Z 4 represents H, F or Cl, and n represents an integer from 2 to 10. However, Z 1 to Z 4 will not simultaneously be F.) vinyl monomer represented by, CF2 = CF - OCH2 - Rf 3 (wherein, Rf 3 represents a perfluoroalkyl group having 1 to 5 carbon atoms.) alkyl perfluorovinyl ether derivatives represented by, ethylene, propylene and the like. The content of other monomers is preferably 0 to 0.5% by mass, more preferably 0.05 to 0.3% by mass, still more preferably 0.1 to 0.2% by mass with respect to all monomer units of the polymer.

[0059] In the present disclosure, the content of each monomer unit in the fluoropolymer is 19 measured by the F - NMR method.

[0060] The melt flow rate (MFR) of the fluoropolymer is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, still more preferably 1.0 g / 10 min or more, preferably 100 g / 10 min or less, more preferably 90 g / 10 min or less, still more preferably 80 g / 10 min or less.

[0061] In the present disclosure, MFR is a value obtained as the mass (g / 10 min) of the polymer flowing out per 10 minutes from a nozzle having an inner diameter of 2.1 mm and a length of 8 mm under a load of 5 kg at 372°C using a melt indexer in accordance with ASTM D1238.

[0062] The melting point of the fluoropolymer is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, preferably 320°C or lower, and more preferably 315°C or lower.

[0063] The melting point of the tetrafluoroethylene / fluorine-containing ether monomer copolymer is preferably 280°C or higher, more preferably 285°C or higher, even more preferably 290°C or higher, preferably 320°C or lower, and more preferably 315°C or lower.

[0064] The melting point of the tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, preferably 300°C or lower, more preferably 285°C or lower, and even more preferably 270°C or lower.

[0065] In this disclosure, the melting point can be measured using a differential scanning calorimetry (DSC).

[0066] (A molded article in which the content of fluorine-containing compounds having hydrophilic groups has been reduced.) According to the manufacturing method of this disclosure, a molded article can be produced in which the content of the fluorine-containing compound having a hydrophilic group is reduced. The fluorine-containing compound having a hydrophilic group is as described above.

[0067] In one embodiment, the general formula in the molded body is: [C5F 11 COO - ]M + (In the formula, M + represents a cation. The content of the compound represented by ) is less than 5 ppb by mass, less than 4 ppb by mass, less than 3 ppb by mass, less than 2 ppb by mass, or less than 1 ppb by mass.

[0068] In one embodiment, the general formula in the molded body is: [C n-1 F 2n-1 COO - ]M +(In the formula, n is an integer between 8 and 14, M + represents a cation. The content of the compound represented by ) is less than 5 ppb by mass, less than 4 ppb by mass, less than 3 ppb by mass, less than 2 ppb by mass, or less than 1 ppb by mass.

[0069] In one embodiment, the general formula in the molded body is: [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 11 and 14, M + represents a cation. The content of the compound represented by ) is less than 5 ppb by mass, less than 4 ppb by mass, less than 3 ppb by mass, less than 2 ppb by mass, or less than 1 ppb by mass.

[0070] In one embodiment, the general formula in the molded body is: [ - OCOC n-1 F 2n-2 COO - ]M1 + M2 + (In the formula, n is an integer between 8 and 14, M1 + M2 + represents a cation. The content of the compound represented by ) is less than 5 ppb by mass, less than 4 ppb by mass, less than 3 ppb by mass, less than 2 ppb by mass, or less than 1 ppb by mass.

[0071] In the manufacturing method of this disclosure, since the heat treatment is performed under the conditions described above, the heat treatment can be performed without significantly changing the shape of the molded article. Therefore, the shape of the molded article produced by the manufacturing method of this disclosure is the same as or substantially the same as the shape of the molded article subjected to heat treatment.

[0072] In the manufacturing method of the present disclosure, the molded body subjected to heat treatment and the molded body produced may be, for example, a nut, bolt, fitting, film, bottle, gasket, wire insulation, tube, hose, pipe, valve, seat, seal, packing, tank, roller, container, cock, connector, filter housing, filter cage, flow meter, pump, wafer carrier, wafer box, etc.

[0073] The molded articles obtained by the manufacturing method of this disclosure can be used for the following purposes, for example: Food packaging films, lining materials for fluid transfer lines used in food manufacturing processes, packings, sealing materials, sheets, and other fluid transfer components for food manufacturing equipment; Chemical stoppers, packaging films, lining materials, packings, sealing materials, sheets, and other chemical liquid transfer components used in pharmaceutical manufacturing processes; Internal lining material for chemical tanks and piping in chemical plants and semiconductor factories; O-rings, tubes, gaskets, valve cores, hoses, seals, etc. used in the fuel systems and peripheral equipment of automobiles; fuel transfer components such as hoses and seals used in the automatic transmission systems of automobiles; Carburetor flange gaskets, shaft seals, valve stem seals, sealing materials, hoses, etc. used in automobile engines and peripheral equipment; other automotive components such as automobile brake hoses, air conditioning hoses, radiator hoses, and wire insulation materials; Chemical transfer components for semiconductor equipment, such as O-rings, tubes, packings, valve cores, hoses, sealing materials, rolls, gaskets, diaphragms, and fittings for semiconductor manufacturing equipment; Painting and ink-related components for painting equipment, such as paint rolls, hoses, tubes, and ink containers; Tubes or hoses for food and beverages, belts, gaskets, fittings and other components for transporting food and beverages, food packaging materials, glass cooking equipment; Tubes, hoses, and other components for transporting waste liquids; Components for transporting high-temperature liquids, such as tubes and hoses; Steam piping components such as tubes and hoses for steam piping; Corrosion-preventive tapes for pipes, such as tapes used to wrap around pipes on ship decks; Various coating materials such as wire coatings, optical fiber coatings, transparent surface coatings and backing materials for the light incident side surface of photovoltaic elements in solar cells; Sliding components of diaphragm pumps, such as diaphragms and various packings; Agricultural films, weather-resistant covers for various roofing materials and side walls; Interior materials used in the construction field, and coatings for glass such as non-combustible fire-resistant safety glass; Lining materials such as laminated steel sheets used in the home appliance sector; Sealing materials such as gaskets and packings used in batteries;

[0074] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0075] <1> According to the first aspect of this disclosure, A method for producing a fluoropolymer molded article, comprising heat-treating a molded article containing a fluoropolymer and a fluorine-containing compound having hydrophilic groups at a temperature below the melting point of the fluoropolymer, thereby producing a molded article in which the content of the fluorine-containing compound having hydrophilic groups is reduced, The molded article contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, The fluorine-containing compound having the hydrophilic group has the general formula:[C5F 11 COO - ]M + (In the formula, M + ) represents a cation. A method for producing a fluoropolymer molded article is provided. <2> According to the second aspect of this disclosure, A manufacturing method is provided in which the molded article is an unused molded article. <3> According to the third aspect of this disclosure, A manufacturing method is provided that involves heat-treating the molded body without crushing the molded body, according to a first or second viewpoint. <4> According to the fourth aspect of this disclosure, A manufacturing method is provided, comprising crushing the molded body and heat-treating the crushed molded body, according to any one of the first to third aspects. <5> According to the fifth aspect of this disclosure, A method for manufacturing the aforementioned molded article, according to any of the first to fourth aspects, is provided, wherein the molded article is a molten molded article. <6> According to the sixth aspect of this disclosure, A manufacturing method is provided according to any one of the first to fifth aspects, wherein the molded article is at least one selected from the group consisting of an extruded article, an injection-molded article, a blow-molded article, and a transfer-molded article. <7> According to the seventh aspect of this disclosure, The provided invention relates to a manufacturing method according to any one of the first to sixth aspects, wherein the molded body is a molten molded body, and the molten molded body is crushed and the crushed molded body is heat-treated. <8> According to the eighth aspect of this disclosure, A manufacturing method is provided according to any of the first to seventh viewpoints, wherein the temperature of the heat treatment is 150°C or higher. <9> According to the ninth aspect of this disclosure, A manufacturing method is provided according to any of the first to eight views, wherein the heat treatment time is 1 second or more. <10> According to the tenth aspect of this disclosure, A manufacturing method is provided according to any of the first to ninth aspects, wherein the content of the fluorine-containing ether monomer units is 1.0 to 12.0% by mass. <11> According to the eleventh aspect of this disclosure, A method for producing the fluoropolymer according to any one of the first to ten views is provided, wherein the fluoropolymer is a tetrafluoroethylene / fluorine-containing ether monomer copolymer and a tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer. <12> According to the 12th aspect of this disclosure, A manufacturing method is provided according to any one of the first to eleven aspects, wherein the content of the fluorine-containing compound having the hydrophilic group in the molded article subjected to the heat treatment is 5 ppb by mass or more. <13> According to the 13th aspect of this disclosure, A manufacturing method is provided according to any of the first to twelfth aspects, wherein the content of the fluorine-containing compound having the hydrophilic group in the molded article after the heat treatment is less than 5 ppb by mass. [Examples]

[0076] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0077] Each value in the examples was measured by the following method.

[0078] <Measurement of the content of perfluorocarboxylic acids and their derivatives with 6 to 14 carbon atoms> After freeze-milling the sample (molded body, pulverized product, etc.) in a ball mill, 0.3 g of the collected powder was mixed with 10 mL (12.6 mL) of methanol and subjected to sonication at 60°C for 2 hours. After standing at room temperature, the solid components were removed to obtain the extract.

[0079] 1. Calibration curve for linear perfluorocarboxylic acids Five levels of methanol standard solutions were prepared for perfluorohexanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, and perfluorotetradecanoic acid, each at known concentrations. Measurements were performed using a liquid chromatograph-mass spectrometer (Agilent Ultivo triple quadrupole LC-MS). Calibration curves were created for each concentration range using a linear approximation based on the methanol standard solution concentration and the integrated peak value.

[0080] [Table 1]

[0081] [Table 2]

[0082] 2. Content of the compound represented by general formula (I) contained in the powder General formula (I):[C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer from 6 to 14, M + (This represents a cation.)

[0083] Using a liquid chromatograph-mass spectrometer, the content of the compound represented by the general formula (I) for the number of carbon atoms (n) in the extract was measured from the calibration curve. The content of the compound represented by the general formula (I) for the number of carbon atoms (n) in the powder was determined using the following relation (2). Yn = Xn × 12.6 (2) Yn: Content of the compound represented by the general formula (I) with the number of carbon atoms (n) in the powder (mass ppb / powder) Xn: Content (ng / mL) of the compound represented by the general formula (I) with the number of carbon atoms (n) in the extract. The limit of quantification for the content of a compound represented by the general formula (I) with a carbon number (n) in a powder is 1 mass ppb / powder.

[0084] [Table 3]

[0085] <Composition of fluoropolymer> The content of each monomer unit was measured using an NMR analyzer (for example, a Bruker BioSpin AVANCE300 high-temperature probe).

[0086] <Meltflow Rate> In accordance with ASTM D1238, the mass (g / 10 min) of polymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes was determined using a melt indexer G-01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 372°C under a 5 kg load.

[0087] <Melting point> Using a differential scanning calorimeter (product name: X-DSC7000, manufactured by Hitachi High-Tech Science Corporation), the temperature was increased from 200°C to 350°C at a heating rate of 10°C / min, followed by cooling from 350°C to 200°C at a cooling rate of 10°C / min. A second heating was then performed from 200°C to 350°C at a heating rate of 10°C / min, and the melting point was determined from the melting curve peak generated during the second heating process.

[0088] Examples 1-6 and Comparative Examples 1-3 used the following materials. PFA: Tetrafluoroethylene / perfluoro(propyl vinyl ether) copolymer Perfluoropropyl vinyl ether content: 5.5% by mass Melting point: 302℃ Melt flow rate: 30.0g / 10 minutes

[0089] Comparative Example 1 PFA was injection molded using a Sumitomo Heavy Industries SE50EV-A injection molding machine with a cylinder temperature of 410°C, a mold temperature of 200°C, and an injection speed of 30 mm / s (residence time in the injection molding machine of approximately 2 minutes) to obtain a molded body (flat plate 100 mm x 100 mm, thickness 3 mmt).

[0090] Example 1 The molded body obtained in Comparative Example 1 was heat-treated at 200°C for 12 hours using a hot air circulating electric furnace, ESPEC Corporation's STPH-202M high-temperature constant temperature oven.

[0091] Comparative Example 2 PFA was injection molded using a Sumitomo Heavy Industries SE50EV-A injection molding machine with a cylinder temperature of 390°C, a mold temperature of 200°C, and an injection speed of 30 mm / s (residence time in the injection molding machine approximately 2 minutes) to obtain a molded body (flat plate 100 mm x 100 mm, thickness 3 mmt). The obtained injection molded body was crushed using a HARMO GRANCUTTER SPCII-C200 to obtain a crushed product.

[0092] Example 2 The pulverized product obtained in Comparative Example 2 was heat-treated at 200°C for 12 hours using a hot air circulating electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0093] Example 3 The pulverized product obtained in Comparative Example 2 was heat-treated at 200°C for 1 hour using a hot air circulating electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0094] Example 4 The pulverized product obtained in Comparative Example 2 was heat-treated at 180°C for 12 hours using a hot air circulating electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0095] Example 5 The pulverized product obtained in Comparative Example 2 was heat-treated at 220°C for 12 hours using a hot air circulation electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0096] Comparative Example 3 PFA was injection molded using a Sumitomo Heavy Industries SE50EV-A injection molding machine with a cylinder temperature of 390°C, a mold temperature of 200°C, and an injection speed of 30 mm / s (residence time in the injection molding machine of approximately 2 minutes) to obtain a molded body (flat plate 100 mm x 100 mm, thickness 3 mmt). The obtained injection molded body was crushed using a Retsch SM300 cutting mill (rotation speed 700 rpm) to obtain a crushed product.

[0097] Example 6 The pulverized product obtained in Comparative Example 3 was heat-treated at 200°C for 12 hours using a hot air circulating electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0098] The following materials were used in Example 7 and Comparative Example 4. PFA: Tetrafluoroethylene / perfluoro(propyl vinyl ether) copolymer Perfluoropropyl vinyl ether content: 4.0% by mass Melting point: 305℃ Melt flow rate: 14.0g / 10 minutes

[0099] Comparative Example 4 PFA was injection molded using a Sumitomo Heavy Industries SE50EV-A injection molding machine with a cylinder temperature of 390°C, a mold temperature of 200°C, and an injection speed of 30 mm / s (residence time in the injection molding machine approximately 2 minutes) to obtain a molded body (flat plate 100 mm x 100 mm, thickness 3 mmt). The obtained injection molded body was crushed using a HARMO GRANCUTTER SPCII-C200 to obtain a crushed product.

[0100] Example 7 The pulverized product obtained in Comparative Example 4 was heat-treated at 200°C for 12 hours using a hot air circulating electric furnace, specifically an ESPEC STPH-202M high-temperature constant temperature oven.

[0101] The results are shown in Table 4. [Table 4]

[0102] In Table 4, n=9 to 14 are the general formula in the molded product (crushed product): [C n-1 F 2n-1 COO - ]M + (In the formula, n is an integer between 9 and 14, M + represents a cation. The total content (mass ppb) of the compounds represented by ) is shown. Additionally, the lower section of Table 4 shows the content of each compound corresponding to n=9 to n=14 (n=9, n=10, n=11-14).

Claims

1. A method for producing a fluoropolymer molded article, comprising heat-treating a molded article containing a fluoropolymer and a fluorine-containing compound having hydrophilic groups at a temperature below the melting point of the fluoropolymer, thereby producing a molded article in which the content of the fluorine-containing compound having hydrophilic groups is reduced, The molded article contains a fluoropolymer containing at least one fluorine-containing ether monomer unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units, The fluorine-containing compound having the hydrophilic group has the general formula: [C ５ F １１ COO － ] M ＋ (In the formula, M ＋ ) represents a cation. A method for producing a fluoropolymer molded article.

2. The manufacturing method according to claim 1, wherein the molded body is an unused molded body.

3. The manufacturing method according to claim 1 or 2, wherein the molded body is heat-treated without crushing the molded body.

4. The manufacturing method according to claim 1 or 2, wherein the molded body is crushed and the crushed molded body is heat-treated.

5. The manufacturing method according to claim 1 or 2, wherein the molded body is a molten molded body.

6. The manufacturing method according to claim 1 or 2, wherein the molded article is at least one selected from the group consisting of an extruded article, an injection-molded article, a blow-molded article, and a transfer-molded article.

7. The manufacturing method according to claim 1 or 2, wherein the molded body is a molten molded body, the molten molded body is crushed, and the crushed molded body is heat-treated.

8. The manufacturing method according to claim 1 or 2, wherein the temperature of the heat treatment is 150°C or higher.

9. The manufacturing method according to claim 1 or 2, wherein the heat treatment time is 1 second or more.

10. The manufacturing method according to claim 1 or 2, wherein the content of the fluorine-containing ether monomer units is 1.0 to 12.0% by mass.

11. The method for producing a fluoropolymer according to claim 1 or 2, wherein the fluoropolymer is a tetrafluoroethylene / fluorine-containing ether monomer copolymer and a tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer.

12. The manufacturing method according to claim 1 or 2, wherein the content of the fluorine-containing compound having the hydrophilic group in the molded article subjected to the heat treatment is 5 ppb by mass or more.

13. The manufacturing method according to claim 1 or 2, wherein the content of the hydrophilic group-containing fluorine compound in the molded article after the heat treatment is less than 5 ppb by mass.

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