Method for producing fluoropolymer molded body

Abstract

This method for producing a fluoropolymer molded body includes heat-treating a molded body that contains a fluoropolymer and a fluorine-containing compound having a hydrophilic group at a temperature lower than the melting point of the fluoropolymer, thereby producing a molded body with the reduced content of the fluorine-containing compound having a hydrophilic group. 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. The fluorine-containing compound having a hydrophilic group is a fluorine-containing compound represented by general formula: [C5F11COO-]M+ (where M+ represents a cation).

Description

Method for producing a fluoropolymer molded article

[0001] The present disclosure relates to a method for producing a fluoropolymer molded article.

[0002] Patent Document 1 describes a method for producing a recycled fluororesin including a step of heat-treating a used fluororesin molded article that has been melt-molded under conditions of 200°C or higher and lower than the melting point.

[0003] Japanese Patent Application Laid-Open No. 2002-36237

[0004] In the present disclosure, an object is to provide a production method capable of producing a fluoropolymer molded article with a reduced content of a fluorine-containing compound represented by the general formula: [C F １１ COO － M ＋ (where M ＋ represents a cation). <00002​​​​​​​​​​​​​​​​​​​​​​​​​​

[0007] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0008] Patent Document 1 describes that by using melt-molded used fluororesin molded products as raw materials and employing the above-described manufacturing method, it is possible to produce recycled fluororesin in which impurities such as chemical solutions and chemicals have been removed to a degree equivalent to that of fluororesin before use.

[0009] However, depending on the molding conditions, fluoropolymer molded articles may have the general formula: [C ５ F １１ COO － ] M ＋ (In the formula, M ＋ The symbol represents a cation. It may contain fluorine-containing compounds represented by ( ).

[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: [C ５ F 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] (Molded article containing a fluorine-containing compound having a hydrophilic group) The molded article subjected to heat treatment in the manufacturing method of the present 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, -NH ２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO ３ Examples include M and -COOM (where M represents a cation in each formula). Among the hydrophilic groups mentioned above, -SO is particularly noteworthy. ３ M 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, represented by the following general formula: General formula: [C ５ F １１ COO － ] M ＋ (In the formula, M ＋ (This represents a cation.)

[0015] General formula in a molded body subjected to heat treatment: [C ５ F 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, represented by the following general formula: General formula: [C ｎ－１ F ２ｎ－１ COO － ] M ＋ (In the formula, n is an integer from 8 to 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 from 8 to 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, represented by the following general formula: General formula: [C ｎ－１ F ２ｎ－１ COO － ] M ＋ (In the formula, n is an integer from 11 to 14, M ＋ (This represents a cation.)

[0019] The molded article subjected to heat treatment contains the general formula: [C ｎ－１ F ２ｎ－１ COO － ] M ＋ (In the formula, n is an integer from 11 to 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, 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 i, and i is an integer from 1 to 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 from 4 to 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 -O-L-CO ２ － ] 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, represented by the general formula (H4). General formula (H4): H-Rf ｎ０ -Y ０ (wherein, 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. 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, represented by the following general formula (H5): General formula (H5): [A － -Rf ｈ０ -A － ] ｉ M ｋ＋ M ｌ＋ (wherein, Rfｈ０ is a linear or branched partially fluorinated or fully fluorinated aliphatic group, or a linear or branched partially fluorinated or fully fluorinated aliphatic group interrupted by at least one oxygen atom, A － is an acid group, M ｋ＋ is a cation having a valence of k, M ｌ＋ is a cation having a valence of l, i represents an integer from 1 to 3, k and l are integers from 0 to 3 and do not become 0 at the same time, and represent an integer such that k + l = i.)

[0025] In one embodiment, the molded body to be heat-treated contains, as a fluorine-containing compound having a hydrophilic group, a compound represented by the following general formula (H6). General formula (H6): － OCOC ｎ－１ F ２ｎ－２ COO － M １ ＋ M ２ ＋ (where n is an integer from 4 to 14, M １ ＋ , M ２ ＋ represents a cation.)

[0026] The content of the fluorine-containing compound having a hydrophilic group in the molded body to be heat-treated may be 5 mass ppb or more, 15 mass ppb or more, 25 mass ppb or more, 30 mass ppb or more, 35 mass ppb or more, 40 mass ppb or more, 45 mass ppb or more or 50 mass ppb or more, and may be 1000 mass ppb or less, and may be 500 mass ppb 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 article is freeze-dried to prepare a powder. Methanol is added to the obtained powder, and extraction is performed. The obtained extract is then analyzed by LC / MS. To further improve the extraction efficiency, treatment by Soxhlet extraction, sonication, etc., may be performed. The obtained extract is concentrated by nitrogen purging as appropriate, and the fluorine-containing compounds in the concentrated extract are measured by LC / MS. Molecular weight information is extracted from the obtained LC / MS spectrum, and its agreement with the structural formula of candidate hydrophilic fluorine-containing compounds is confirmed. Subsequently, aqueous solutions with five or more levels of content of the confirmed hydrophilic fluorine-containing compounds are prepared, and LC / MS analysis is performed on each aqueous solution. The relationship between the content and the area area corresponding to that content is plotted, and a calibration curve is drawn. Then, using the calibration curve, the area area of ​​the LC / MS chromatogram of the hydrophilic fluorine-containing compounds in the extract can be converted to the content of the hydrophilic fluorine-containing compounds. 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 C-O 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-type 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 it may be repeated 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 as a lower limit, 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. Perfluorovinyl ether is represented by the general formula (1): CF ２ =CF - ORf １ (wherein, Rf １ ) represents a perfluoroorganic group. Examples include fluoromonomers represented by ).

[0046] The perfluoroorganic group is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, preferably a perfluoroalkyl group having 1 to 6 carbon atoms, and preferably a perfluoroalkyl group having 1 to 3 carbon atoms. Examples of perfluoroorganic groups include perfluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, and perfluorohexyl group.

[0047] Perfluorovinyl ethers include perfluoro(methyl vinyl ether) (CF ２ = CF - O - CF ３ ), perfluoro(ethyl vinyl ether) (CF ２ =CF-O-C ２ F ５ ) and perfluoro(propyl vinyl ether) (CF ２ =CF-O-C ３ F ７ At least one selected from the group consisting of ) is preferred, and at least one selected from the group consisting of perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) is more preferred.

[0048] The perfluoroallyl ether unit is a monomer unit based on perfluoroallyl ether. The general formula for perfluoroallyl ether is: CF ２ = CF - CF２ -ORf ２ (wherein, Rf ２ ) represents a perfluoroorganic group. Examples include fluoromonomers represented by ).

[0049] Rf of general formula (2) ２ Rf in general formula (1) １ It is the same as CF. ２ = CF - CF ２ -O-CF ３ CF ２ = CF - CF ２ -O-C ２ F ５ CF ２ = CF - CF ２ -O-C ３ F ７ and CF ２ = CF - CF ２ -O-C ４ F ９ Preferably, at least one selected from the group consisting of CF ２ = CF - CF ２ -O-C ２ F ５ CF ２ = CF - CF ２ -O-C ３ F ７ and CF ２ = CF - CF ２ -O-C ４ F ９ More preferably, at least one selected from the group consisting of CF ２ = CF - CF ２ -O-CF ２ CF ２ CF ３ That 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, even 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 (CF ２ ) ｎ Z ４ (In the formula, Z １ Z ２ and Z ３ These represent H or F, and Z, either identical or different. ４ represents H, F, or Cl, and n represents an integer from 2 to 10. However, Z １ ~Z ４It is not possible for both to be F at the same time.) Vinyl monomer, CF ２ = CF - OCH ２ -Rf ３ (wherein, Rf ３ ∫ represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples include alkyl perfluorovinyl ether derivatives represented by ∫, ethylene, and propylene. The content of other monomers is preferably 0 to 0.5% by mass, more preferably 0.05 to 0.3% by mass, and even more preferably 0.1 to 0.2% by mass, relative to the total monomer units of the polymer.

[0059] In this disclosure, the content of each monomer unit in the fluoropolymer is: １９ Measurement is performed using 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, even more preferably 1.0 g / 10 min or more, preferably 100 g / 10 min or less, more preferably 90 g / 10 min or less, and even more preferably 80 g / 10 min or less.

[0061] In this disclosure, MFR is a value obtained in accordance with ASTM D1238 as 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 using a melt indexer at 372°C and a load of 5 kg.

[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] (Molded article with reduced content of hydrophilic fluorine-containing compound) According to the manufacturing method of the present disclosure, a molded article can be produced with a reduced content of hydrophilic fluorine-containing compound. The hydrophilic fluorine-containing compound is as described above.

[0067] In one embodiment, the general formula in the molded body is: [C ５ F 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 from 8 to 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 from 11 to 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 － ] M １ ＋ M ２ ＋ (In the formula, n is an integer from 8 to 14, M １ ＋ M ２ ＋ 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 applications, for example: Food packaging films, lining materials for fluid transfer lines used in food manufacturing processes, packings, seals, sheets, and other fluid transfer components for food manufacturing equipment; chemical stoppers, packaging films, lining materials for fluid transfer lines used in pharmaceutical manufacturing processes, packings, seals, sheets, and other chemical transfer components; internal lining components for chemical tanks and piping in chemical plants and semiconductor factories; fuel transfer components such as O-rings, tubes, packings, valve cores, hoses, seals, etc. used in automobile fuel systems and peripheral equipment, and hoses, seals, etc. used in automobile automatic transmission systems; other automobile components such as carburetor flange gaskets, shaft seals, valve stem seals, seals, hoses, etc. used in automobile engines and peripheral equipment, and 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, seals, rolls, gaskets, diaphragms, and fittings for semiconductor manufacturing equipment. Painting and ink components such as paint rolls, hoses, tubes, and ink containers for painting equipment; Food and beverage transport components such as tubes or hoses, belts, gaskets, and fittings, food packaging materials, and glass cooking equipment; Waste liquid transport components such as tubes and hoses for waste liquid transport; High-temperature liquid transport components such as tubes and hoses for high-temperature liquid transport; Steam piping components such as tubes and hoses for steam piping; Corrosion-preventive tapes for piping such as tapes wrapped around piping on ship decks, etc.; Various coating materials such as wire coatings, optical fiber coatings, transparent surface coatings and backings for the light incident side surface of photovoltaic elements in solar cells; Sliding components such as diaphragms and various gaskets for diaphragm pumps; Weather-resistant covers for agricultural films, various roofing materials, and side walls; Interior materials used in the construction field, coatings for glass such as non-combustible fire-resistant safety glass; Lining materials such as laminated steel plates used in the home appliance field, etc.; 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 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 has a general formula: [C ５ F １１ COO － ] M ＋ (In the formula, M ＋A method for producing a fluoropolymer molded article which is a fluorine-containing compound represented by ) is provided. <2> According to a second aspect of the present disclosure, a method for producing the molded article according to a first aspect is provided, wherein the molded article is an unused molded article. <3> According to a third aspect of the present disclosure, a method for producing the molded article according to a first or second aspect is provided, wherein the molded article is heat-treated without pulverizing the molded article. <4> According to a fourth aspect of the present disclosure, a method for producing the molded article according to any one of the first to third aspects is provided, wherein the molded article is pulverized and the pulverized molded article is heat-treated. <5> According to a fifth aspect of the present disclosure, a method for producing the molded article according to any one of the first to fourth aspects is provided, wherein the molded article is a molten molded article. <6> According to a sixth aspect of the present disclosure, a method for producing the molded article according to any one of the first to fifth aspects is provided, 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, a manufacturing method is provided according to any of the first to sixth aspects, wherein the molded article is a molten molded article, the molten molded article is crushed, and the crushed molded article 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 aspects, 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 eighth aspects, wherein the time of the heat treatment 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 manufacturing method is provided according to any of the first to tenth aspects, wherein the fluoropolymer is a tetrafluoroethylene / fluorine-containing ether monomer copolymer and a tetrafluoroethylene / hexafluoropropylene / fluorine-containing ether monomer copolymer. <12> According to the twelfth aspect of the present disclosure, a manufacturing method according to any of the first to eleventh aspects is provided, 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 thirteenth aspect of this disclosure, a manufacturing method according to any of the first to twelfth aspects is provided, wherein the content of the hydrophilic fluorine-containing compound in the molded article after heat treatment is less than 5 ppb by mass.

[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 with 6 to 14 carbon atoms and their derivatives> After freeze-grinding 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, all of which have known concentrations. Measurements were performed using a liquid chromatograph-mass spectrometer (Agilent, Ultivo triple quadrupole LC-MS). For each concentration range, a calibration curve was created using a first-order approximation based on the methanol standard solution concentration and the integrated peak value.

[0080]

[0081]

[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 relationship (2): Yn = Xn × 12.6 (2) Yn: Content of the compound represented by the general formula (I) for the number of carbon atoms (n) in the powder (mass ppb / powder) Xn: Content of the compound represented by the general formula (I) for the number of carbon atoms (n) in the extract (ng / mL) The limit of quantification for the content of the compound represented by the general formula (I) for the number of carbon atoms (n) in the powder is 1 mass ppb / powder.

[0084]

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

[0086] <Melt Flow Rate> In accordance with ASTM D1238, the mass of polymer flowing out per 10 minutes (g / 10 min) from a nozzle with an inner diameter of 2.1 mm and a length of 8 mm was determined using a melt indexer G-01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 372°C and 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 for the first time, then cooled from 350°C to 200°C at a cooling rate of 10°C / min, and then heated again from 200°C to 350°C at a heating rate of 10°C / min for the second time. The melting point was determined from the peak of the melting curve that occurred 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°C Melt flow rate: 30.0 g / 10 min

[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 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 pulverized using a HARMO GRANCUTTER SPCII-C200 to obtain a pulverized 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, ESPEC Corporation's 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, ESPEC Corporation's 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, ESPEC Corporation's 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 circulating electric furnace, ESPEC Corporation's 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 pulverized using a Retsch SM300 cutting mill (rotation speed 700 rpm) to obtain a pulverized 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, ESPEC Corporation's STPH-202M high-temperature constant temperature oven.

[0098] In Example 7 and Comparative Example 4, the following materials were used: PFA: Tetrafluoroethylene / perfluoro(propyl vinyl ether) copolymer Perfluoropropyl vinyl ether content: 4.0% by mass Melting point: 305°C Melt flow rate: 14.0 g / 10 min

[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 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 pulverized using a HARMO GRANCUTTER SPCII-C200 to obtain a pulverized 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, ESPEC Corporation's STPH-202M high-temperature constant temperature oven.

[0101] The results are shown in Table 4.

[0102] In Table 4, n=9 to 14 represent the general formula in the molded body (crushed product): [C ｎ－１ F ２ｎ－１ COO － ] M ＋ (In the formula, n is an integer from 9 to 14, M ＋represents a cation. ) represents the total content (mass ppb) of the compound represented. 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 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 has a general formula: [C ５ F １１ COO － ] M ＋ (In the formula, M ＋ A method for producing a fluoropolymer molded article which is a fluorine-containing compound represented by ).

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 being crushed.

4. The manufacturing method according to any one of claims 1 to 3, wherein the molded body is crushed and the crushed molded body is heat-treated.

5. The manufacturing method according to any one of claims 1 to 4, wherein the molded body is a molten molded body.

6. The manufacturing method according to any one of claims 1 to 5, 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 any one of claims 1 to 6, 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 any one of claims 1 to 7, wherein the temperature of the heat treatment is 150°C or higher.

9. The manufacturing method according to any one of claims 1 to 8, wherein the time of the heat treatment is 1 second or more.

10. The manufacturing method according to any one of claims 1 to 9, wherein the content of the fluorine-containing ether monomer units is 1.0 to 12.0% by mass.

11. The manufacturing method according to any one of claims 1 to 10, 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 any one of claims 1 to 11, 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 any one of claims 1 to 12, wherein the content of the fluorine-containing compound having the hydrophilic group in the molded article after heat treatment is less than 5 ppb by mass.

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