Copolymer, injection molded article, compressed member and coated electric wire

Abstract

To provide a copolymer that has a high glass transition temperature, has appropriate hardness even at high temperatures, and can be used to obtain injection-molded articles with excellent surface smoothness with high productivity, and can easily form a thin coating layer with excellent capacitance stability on a small-diameter core wire, and can be used to obtain molded articles with excellent crack resistance and abrasion resistance at high temperatures, extremely low water vapor permeability, and resistance to water vapor penetration, and with extremely excellent sealing properties at high temperatures. [Solution] A copolymer is provided which contains tetrafluoroethylene units and perfluoro(propyl vinyl ether) units, in which the content of perfluoro(propyl vinyl ether) units is 2.0 to 2.8 mass% based on the total monomer units, and which has a melt flow rate of 23 to 30 g / 10 min.

Description

[Technical Field]

[0001] The present disclosure relates to a copolymer, an injection-molded article, a compressed member, and a coated electric wire. [Background technology]

[0002] Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) is known as a fluororesin that has excellent mechanical, chemical, and electrical properties and is also melt-processable.

[0003] For example, Patent Document 1 describes a sealing material made of a fluorine-containing polymer having polymerization units based on tetrafluoroethylene and polymerization units based on one or more types of perfluoro(alkyl vinyl ether), wherein the fluorine-containing polymer contains polymerization units based on perfluoro(alkyl vinyl ether) in an amount of 4.0 mass% or less based on the total polymerization units, and has a melt flow rate of 0.1 to 100 g / 10 min. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-177574 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide a copolymer that has a high glass transition temperature, has appropriate hardness even at high temperatures, and can be used to produce injection-molded articles with excellent surface smoothness with high productivity, and can easily form a thin coating layer with excellent capacitance stability on a small-diameter core wire, and can be used to produce molded articles that have excellent crack resistance and abrasion resistance at high temperatures, are extremely low in water vapor permeability, are difficult to allow water vapor to penetrate, and have extremely excellent sealing properties at high temperatures. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a copolymer containing tetrafluoroethylene units and perfluoro(propyl vinyl ether) units, in which the content of perfluoro(propyl vinyl ether) units is 2.0 to 2.8 mass% based on the total monomer units, and the melt flow rate is 23 to 30 g / 10 min.

[0007] The copolymer of the present disclosure has a main chain carbon number of 10 and a functional group number of 10. 6 It is preferable that the number of particles per particle is 50 or less.

[0008] According to the present disclosure, there is provided an injection-molded article containing the above copolymer.

[0009] According to the present disclosure, there is provided a compressed member containing the above copolymer.

[0010] According to the present disclosure, there is provided a covered electric wire having a covering layer containing the above-described copolymer. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a copolymer that has a high glass transition temperature, has appropriate hardness even at high temperatures, and can be used to obtain injection-molded articles with excellent surface smoothness with high productivity, and can easily form a thin coating layer with excellent capacitance stability on a small-diameter core wire, and can be used to obtain molded articles that have excellent crack resistance and abrasion resistance at high temperatures, are extremely low in water vapor permeability, are difficult to allow water vapor to penetrate, and have extremely excellent sealing properties at high temperatures. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a test jig used in a water vapor leakage test. DETAILED DESCRIPTION OF THE INVENTION

[0013] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0014] The copolymers of the present disclosure contain tetrafluoroethylene (TFE) units and perfluoro(propyl vinyl ether) (PPVE) units.

[0015] Patent Document 1 describes that in-vehicle secondary batteries are sometimes exposed to high temperatures of 85°C or higher in their usage environment, and that in order to maintain airtightness and liquid tightness inside the battery, it is important that the sealing material retains sufficient compression recovery even under such harsh usage conditions and can maintain high adhesion between the battery can and the sealing body.

[0016] However, there is a need for copolymers that can maintain their sealing properties even in higher temperature environments, and in particular, there is a need for copolymers that can exhibit excellent sealing properties even at temperatures above the glass transition temperature of the copolymer.

[0017] It has been discovered that by appropriately adjusting the PPVE unit content and melt flow rate (MFR) of a copolymer containing TFE units and PPVE units, the glass transition temperature of the copolymer can be sufficiently increased, exhibiting excellent heat resistance and maintaining appropriate hardness even at high temperatures, and that molded articles containing such copolymers exhibit excellent sealing properties at high temperatures. Because of the appropriate hardness even at high temperatures, molded articles exhibit excellent crack resistance and abrasion resistance at high temperatures, and even thin-walled molded articles can be obtained that exhibit sufficient rebound resilience. Furthermore, it has been discovered that the use of such copolymers allows for the production of injection-molded articles with excellent surface smoothness with high productivity, allows for the easy formation of a thin coating layer with excellent capacitance stability on a small-diameter core wire, and provides molded articles with extremely low water vapor permeability, making them difficult for water vapor to penetrate, and exhibits excellent sealing properties at high temperatures.

[0018] The copolymers of the present disclosure are melt-processable fluoroplastics, meaning that the polymers can be melted and processed using conventional processing equipment such as extruders and injection molding machines.

[0019] The PPVE unit content of the copolymer is 2.0 to 2.8% by mass, based on the total monomer units, preferably 2.1% by mass or more, more preferably 2.2% by mass or more, even more preferably 2.3% by mass or more, particularly preferably 2.4% by mass or more, most preferably 2.6% by mass or more, and preferably 2.7% by mass or less. By having the PPVE unit content of the copolymer within the above range, it is possible to obtain a copolymer with a higher glass transition temperature and appropriate hardness even at high temperatures. Furthermore, it is possible to obtain molded articles that have excellent crack resistance and abrasion resistance at high temperatures, extremely low water vapor permeability, furthermore, are more resistant to water vapor penetration, and have excellent sealing properties at high temperatures. Furthermore, using such copolymers, it is possible to obtain injection-molded articles with excellent surface smoothness with high productivity, and it is possible to more easily form thin coating layers with excellent capacitance stability on small-diameter core wires.

[0020] The content of TFE units in the copolymer is preferably 97.2 to 98.0% by mass, more preferably 97.9% by mass or less, even more preferably 97.8% by mass or less, still more preferably 97.7% by mass or less, particularly preferably 97.6% by mass or less, most preferably 97.4% by mass or less, and more preferably 97.3% by mass or more, based on the total monomer units. By having the TFE unit content in the copolymer within the above range, it is possible to obtain a copolymer with a higher glass transition temperature and appropriate hardness even at high temperatures. Furthermore, it is possible to obtain a molded article that has excellent crack resistance and abrasion resistance at high temperatures, extremely low water vapor permeability, furthermore resists water vapor penetration, and has excellent sealing properties at high temperatures. Furthermore, using such a copolymer, it is possible to obtain an injection-molded article with excellent surface smoothness with high productivity, and it is possible to more easily form a thin coating layer with excellent capacitance stability on a small-diameter core wire.

[0021] In the present disclosure, the content of each monomer unit in the copolymer is: 19 Measured by F-NMR.

[0022] The copolymer may also contain monomer units derived from a monomer copolymerizable with TFE and PPVE. In this case, the content of the monomer units copolymerizable with TFE and PPVE is preferably 0 to 4.0 mass%, more preferably 0.05 to 0.80 mass%, and even more preferably 0.1 to 0.5 mass%, based on the total monomer units of the copolymer.

[0023] Monomers that can be copolymerized with TFE and PPVE include hexafluoropropylene (HFP), CZ 1 Z 2 =CZ 3 (CF2) n Z 4 (In the formula, 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 of 2 to 10.) and a vinyl monomer represented by CF2=CF-OCH2-Rf 1 (In the formula, Rf 1 represents a perfluoroalkyl group having 1 to 5 carbon atoms. Among these, HFP is preferred.

[0024] The copolymer is preferably at least one selected from the group consisting of copolymers consisting only of TFE units and PPVE units, and TFE / HFP / PPVE copolymers, and more preferably a copolymer consisting only of TFE units and PPVE units.

[0025] The melt flow rate (MFR) of the copolymer is 23 to 30 g / 10 min, preferably 24 g / 10 min or more, more preferably 25 g / 10 min or more, even more preferably 26 g / 10 min or more, and preferably 27 g / 10 min or less.

[0026] By using a copolymer having an MFR within the above range, it is possible to obtain injection-molded articles with superior surface smoothness with higher productivity, and it is possible to more easily form a thin coating layer with excellent capacitance stability on a small-diameter core wire. Furthermore, it is possible to obtain molded articles with extremely low water vapor permeability, resistance to water vapor penetration, excellent crack resistance and abrasion resistance at high temperatures, and excellent sealing properties at high temperatures.

[0027] By setting the MFR of the copolymer within the above range, the flowability of the copolymer during molding is improved, making it possible to use a relatively low molding temperature. As a result, when the number of functional groups in the copolymer is low, setting the MFR within the above range produces a synergistic effect by reducing the number of functional groups in the copolymer, thereby suppressing mold corrosion. Furthermore, by using the copolymer of the present disclosure, it is possible to simultaneously produce a large number of small injection-molded articles having thin-walled portions.

[0028] In the present disclosure, MFR is a value obtained in accordance with ASTM D1238 using a melt indexer, as 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 under a load of 5 kg at 372°C.

[0029] The MFR can be adjusted by adjusting the type and amount of a polymerization initiator used when polymerizing the monomers, the type and amount of a chain transfer agent, and the like.

[0030] In the present disclosure, the copolymer has a main chain carbon number of 10 6The number of functional groups per copolymer is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, even more preferably 20 or less, especially preferably 15 or less, particularly preferably 10 or less, and most preferably less than 6. By having the number of functional groups in the copolymer within the above range, corrosion of the mold used for molding can be suppressed, and electrical properties can be further improved. Furthermore, a molded product that is less likely to release fluorine ions into the electrolyte can be obtained.

[0031] Furthermore, adjusting the number of functional groups of the copolymer within the above range is preferable because it can prevent the decomposition of the copolymer's functional groups, which generates gas and leads to molding defects such as foaming. This can prevent mold corrosion, whether using a multi-cavity mold to mold multiple thin-walled injection-molded articles or a single-cavity mold to mold large, thin-walled injection-molded articles. Too many functional groups in the copolymer increases the likelihood of molding defects and mold corrosion. Lowering the molding temperature can reduce these risks, but lowering the molding temperature reduces the copolymer's moldability, necessitating an increase in the copolymer's MFR, which can result in molded articles that are not sufficiently resistant to water vapor penetration or that do not have excellent sealing properties at high temperatures. When the number of functional groups in the copolymer is within the above range, the copolymer can be molded without lowering the molding temperature, even if the copolymer's MFR is within the above range, allowing molded articles with excellent physical properties to be obtained with high productivity.

[0032] Infrared spectroscopy can be used to identify the type of functional group and measure the number of functional groups.

[0033] The number of functional groups is specifically measured by the following method. First, the copolymer is molded by cold pressing to prepare a film having a thickness of 0.25 to 0.30 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain an infrared absorption spectrum of the copolymer, and a difference spectrum is obtained from the base spectrum, which is completely fluorinated and has no functional groups. From the absorption peaks of specific functional groups that appear in this difference spectrum, the number of carbon atoms in the copolymer (1 × 10) is calculated according to the following formula (A): 6 Calculate the number of functional groups per molecule, N.

[0034] N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm)

[0035] For reference, the absorption frequencies, molar absorption coefficients, and correction factors for several functional groups are shown in Table 1. The molar absorption coefficients were determined from FT-IR measurement data of low-molecular-weight model compounds. [Table 1]

[0036] The absorption frequencies of -CH2CF2H, -CH2COF, -CH2COOH, -CH2COOCH3, and -CH2CONH2 are shown in the table, and are several tens of Kaiser (cm) from the absorption frequencies of -CF2H, -COF, -COOH free and -COOH bonded, -COOCH3, and -CONH2, respectively. -1 ) becomes lower.

[0037] For example, the number of functional groups of -COF is the absorption frequency of 1883 cm due to -CF2COF. -1 The number of functional groups determined from the absorption peak of -CH2COF and the absorption frequency of 1840 cm -1 The number of functional groups is the sum of the number of functional groups determined from the absorption peaks of the compounds.

[0038] The functional groups are those present at the ends of the main chain or side chains of the copolymer, and those present in the main chain or side chains. The number of functional groups may be the total number of -CF=CF, -CFH, -COF, -COOH, -COOCH, -CONH, and -CHOH.

[0039] The functional group is introduced into the copolymer by, for example, a chain transfer agent or a polymerization initiator used in producing the copolymer. For example, when an alcohol is used as a chain transfer agent or a peroxide having a -CHOH structure is used as a polymerization initiator, -CHOH is introduced into the main chain terminal of the copolymer. Alternatively, the functional group can be introduced into the side chain terminal of the copolymer by polymerizing a monomer having a functional group.

[0040] By subjecting a copolymer having such functional groups to a fluorination treatment, a copolymer having a number of functional groups within the above range can be obtained. That is, the copolymer of the present disclosure is preferably a fluorination-treated copolymer. The copolymer of the present disclosure also preferably has a -CF3 terminal group.

[0041] The melting point of the copolymer is preferably 305 to 315° C., more preferably 305 to 313° C. When the melting point is within the above range, it is possible to obtain a copolymer that gives a molded article having even more excellent sealability, particularly at high temperatures.

[0042] In this disclosure, melting points can be measured using a differential scanning calorimeter (DSC).

[0043] The glass transition temperature (Tg) of the copolymer is preferably 95° C. or higher, more preferably 99° C. or higher, and preferably 110° C. or lower, more preferably 105° C. or lower, and even more preferably 100° C. or lower. Because the copolymer of the present disclosure can have such a high glass transition temperature, it is possible to obtain a copolymer that exhibits excellent heat resistance and gives a molded article with even more excellent sealability, particularly at high temperatures.

[0044] In the present disclosure, the glass transition temperature can be measured by dynamic viscoelasticity measurement.

[0045] The water vapor permeability of the copolymer is preferably 7.0 g cm / m 2 Less than 6.8 g cm / m 2 Less than 6.6 g cm / m, more preferably 2 The copolymer of the present disclosure has an extremely low water vapor permeability because the PPVE unit content and melt flow rate (MFR) of the copolymer containing TFE units and PPVE units are appropriately adjusted. Therefore, by using a molded article containing the copolymer of the present disclosure as, for example, a compressed member of a secondary battery, it is possible to effectively prevent moisture penetration even under high-temperature and high-humidity conditions.

[0046] In the present disclosure, the water vapor permeability can be measured for 30 days at a temperature of 95° C. The water vapor permeability can be specifically measured by the method described in the examples.

[0047] The copolymer of the present disclosure preferably has an amount of eluted fluorine ions detected in an electrolyte immersion test of 1.0 ppm or less, more preferably 0.8 ppm or less, and even more preferably 0.7 ppm or less, by mass. When the amount of eluted fluorine ions is within the above range, the generation of gases such as HF in a nonaqueous electrolyte battery can be further suppressed, and the deterioration of battery performance and shortened life of the nonaqueous electrolyte battery can be further suppressed.

[0048] In the present disclosure, the electrolyte immersion test can be performed by preparing a test piece using the copolymer, the test piece having a weight equivalent to 10 molded bodies (15 mm × 15 mm × 0.2 mm), and placing the test piece and 2 g of dimethyl carbonate (DMC) in a glass sample bottle in a thermostatic bath at 80°C and leaving it for 144 hours.

[0049] The copolymer of the present disclosure can provide a molded article with excellent sealability at high temperatures. The sealability at high temperatures can be evaluated by measuring the storage modulus (E') at 150°C, the recovery at 150°C, and the contact pressure at 150°C. A copolymer with a high storage modulus (E') at 150°C and a large recovery at 150°C can continue to exhibit sufficient rebound resilience even at high temperatures for a long period of time. Furthermore, a copolymer with high contact pressure at 150°C can provide a molded article with excellent sealability at high temperatures. The copolymer of the present disclosure can provide a molded article that exhibits excellent sealability even at high temperatures exceeding the glass transition temperature of the copolymer.

[0050] The storage modulus (E') of the copolymer at 150°C is preferably 145 MPa or more, more preferably 150 MPa or more, even more preferably 155 MPa or more, and preferably 1000 MPa or less, more preferably 500 MPa or less, and even more preferably 300 MPa or less. When the storage modulus (E') of the copolymer at 150°C is within the above range, it is possible to obtain a copolymer that has appropriate hardness even at high temperatures, can continue to exhibit sufficient impact resilience even at high temperatures for a long period of time, and gives a molded article with even better sealability at high temperatures.

[0051] The storage modulus (E') can be measured by dynamic viscoelasticity measurement in the range of 30 to 250°C under conditions of a temperature rise rate of 2°C / min and a frequency of 10 Hz. The storage modulus (E') at 150°C can be increased by adjusting the PPVE unit content and melt flow rate (MFR) of the copolymer.

[0052] The surface pressure of the copolymer at 150°C is preferably 1.30 MPa or more, more preferably 1.40 MPa or more, and even more preferably 1.50 MPa or more, and although there is no particular upper limit, it may be 2.00 MPa or less. The surface pressure at 150°C can be increased by adjusting the PPVE unit content and melt flow rate (MFR) of the copolymer.

[0053] A test piece obtained from the copolymer is deformed at a compression deformation rate of 50%, left at 150°C for 18 hours, released from the compressed state, left at room temperature for 30 minutes, and then the height of the test piece (the height of the test piece after compression deformation) is measured, and the surface pressure can be calculated from the height of the test piece after compression deformation and the storage modulus (MPa) at 150°C using the following formula. 150℃ surface pressure (MPa) = (t2-t1) / t1×E' t1: Original height of the test piece before compressive deformation (mm) x 50% t2: Height of the test piece after compressive deformation (mm) E': Storage modulus at 150°C (MPa)

[0054] The recovery of the copolymer at 150°C can be measured using the same method as for measuring surface pressure. The recovery of the molded product at 150°C is the difference (t2 - t1) between the height of the test piece after compression deformation (t2) and the original height of the test piece before compression deformation (t1) when the test piece is deformed at a compression deformation rate of 50%. The recovery of the molded product at 150°C can be increased by adjusting the PPVE unit content and melt flow rate (MFR) of the copolymer.

[0055] The copolymer of the present disclosure preferably has a dielectric loss tangent at 6 GHz of 6.0×10 -4 or less, and more preferably 5.0 × 10 -4 or less, and more preferably 4.0 × 10 -4 The dielectric loss tangent of the copolymer can be adjusted to fall within the above range by adjusting the number of functional groups in the copolymer. In recent years, with the increase in the amount of information transmitted, there has been a trend toward increasingly high-frequency radio waves. For example, microwaves in the range of 3 to 30 GHz are used for high-frequency wireless LANs, satellite communications, mobile phone base stations, and the like. Materials having a low dielectric loss tangent (tan δ) are required as components for use in communication devices that use such high frequencies. When the dielectric loss tangent of the copolymer of the present disclosure is within the above range, the attenuation rate of high-frequency signals is significantly reduced, which is preferable.

[0056] In the present disclosure, the dielectric loss tangent is a value obtained by measuring the change in resonant frequency and electric field strength in a temperature range of 20 to 25°C using a network analyzer and a cavity resonator manufactured by Agilent Technologies.

[0057] The copolymer of the present disclosure can be produced by a polymerization method such as suspension polymerization, solution polymerization, emulsion polymerization, or bulk polymerization. Emulsion polymerization or suspension polymerization is preferred as the polymerization method. In these polymerizations, various conditions such as temperature and pressure, as well as the polymerization initiator and other additives, can be appropriately set depending on the composition and amount of the copolymer.

[0058] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0059] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example: dialkyl peroxycarbonates such as di-normal propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, and di-2-ethoxyethyl peroxydicarbonate; Peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate; Dialkyl peroxides such as di-t-butyl peroxide; Di[fluoro(or fluorochloro)acyl]peroxides; are some of the most representative examples.

[0060] Di[fluoro(or fluorochloro)acyl]peroxides include diacyl peroxides represented by [(RfCOO)-]2 (Rf is a perfluoroalkyl group, an ω-hydroperfluoroalkyl group, or a fluorochloroalkyl group).

[0061] Examples of di[fluoro(or fluorochloro)acyl]peroxides include di(ω-hydro-dodecafluorohexanoyl)peroxide, di(ω-hydro-tetradecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, di(perfluoropropionyl)peroxide, di(perfluorobutyryl)peroxide, di(perfluoroparenyl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, and di(ω-chloro-decafluorohexa di(ω-chloro-tetradecafluorooctanoyl) peroxide, di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, di(undecachlorotriacontafluorodocosanoyl) peroxide, and the like.

[0062] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, for example, ammonium salts, potassium salts, sodium salts of persulfuric acid, perborate, perchloric acid, perphosphoric acid, percarbonate, etc.; organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide; t-butyl permalate; t-butyl hydroperoxide, etc. A reducing agent such as a sulfite may be used in combination with the peroxide, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0063] In the polymerization, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known surfactants, chain transfer agents, and solvents can be used.

[0064] As the surfactant, known surfactants can be used, such as nonionic surfactants, anionic surfactants, and cationic surfactants. Among them, fluorine-containing anionic surfactants are preferred, and linear or branched fluorine-containing anionic surfactants having 4 to 20 carbon atoms that may contain ether-bonded oxygen (i.e., oxygen atoms may be inserted between carbon atoms) are more preferred. The amount of surfactant added (relative to the polymerization water) is preferably 50 to 5,000 ppm.

[0065] Examples of chain transfer agents include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetate esters such as ethyl acetate and butyl acetate; alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride. The amount of chain transfer agent added varies depending on the magnitude of the chain transfer constant of the compound used, but is usually used in the range of 0.01 to 20% by mass based on the polymerization solvent.

[0066] Examples of the solvent include water and a mixed solvent of water and alcohol.

[0067] In the suspension polymerization, a fluorine-based solvent may be used in addition to water. Examples of the fluorine-based solvent include hydrochlorofluoroalkanes such as CH3CClF2, CH3CCl2F, CF3CF2CCl2H, and CF2ClCF2CFHCl; chlorofluoroalkanes such as CF2ClCFClCF2CF3 and CF3CFClCFClCF3; hydrofluoroalkanes such as CF3CFHCFHCF2CF2CF3, CF2HCF2CF2CF2CF2H, and CF3CF2CF2CF2CF2CF2CF2H; CH3OC2F5, CH3OC3F5 Examples of suitable fluorine-containing solvents include hydrofluoroethers such as CF3CF2CH2OCHF2, CF3CHFCF2OCH3, CHF2CF2OCH2F, (CF3)2CHCF2OCH3, CF3CF2CH2OCH2CHF2, and CF3CHFCF2OCH2CF3; and perfluoroalkanes such as perfluorocyclobutane, CF3CF2CF2CF3, CF3CF2CF2CF2CF3, and CF3CF2CF2CF2CF2CF3, with perfluoroalkanes being preferred. From the standpoints of suspension property and economy, the amount of the fluorine-containing solvent used is preferably 10 to 100% by mass relative to the aqueous medium.

[0068] The polymerization temperature is not particularly limited and may be 0 to 100° C. The polymerization pressure is determined appropriately depending on the type, amount, and vapor pressure of the solvent used, as well as other polymerization conditions such as the polymerization temperature, but may usually be 0 to 9.8 MPaG.

[0069] When an aqueous dispersion containing a copolymer is obtained by the polymerization reaction, the copolymer can be recovered by coagulating the copolymer contained in the aqueous dispersion, washing, and drying. When the copolymer is obtained as a slurry by the polymerization reaction, the copolymer can be recovered by removing the slurry from the reaction vessel, washing, and drying. By drying, the copolymer can be recovered in powder form.

[0070] The copolymer obtained by polymerization may be formed into pellets. The method for forming the pellets is not particularly limited, and conventionally known methods can be used. For example, the copolymer may be melt-extruded using a single-screw extruder, twin-screw extruder, or tandem extruder, cut to a predetermined length, and then formed into pellets. The extrusion temperature during melt extrusion must be varied depending on the melt viscosity of the copolymer and the production method, and is preferably the melting point of the copolymer + 20°C to the melting point of the copolymer + 140°C. The method for cutting the copolymer is not particularly limited, and conventionally known methods such as strand cutting, hot cutting, underwater cutting, and sheet cutting can be used. The obtained pellets may be heated to remove volatile components therein (degassing treatment). The obtained pellets may be treated by contacting them with hot water at 30 to 200°C, steam at 100 to 200°C, or hot air at 40 to 200°C.

[0071] The copolymer obtained by polymerization may be subjected to a fluorination treatment. Fluorination treatment can be carried out by contacting an unfluorinated copolymer with a fluorine-containing compound. The fluorination treatment converts thermally unstable functional groups of the copolymer, such as -COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, and -CONH2, and relatively thermally stable functional groups such as -CF2H, into the thermally extremely stable -CF3. As a result, the total number (number of functional groups) of -COOH, -COOCH3, -CH2OH, -COF, -CF=CF2, -CONH2, and -CF2H in the copolymer can be easily adjusted to fall within the above-mentioned range.

[0072] The fluorine-containing compound is not particularly limited, but may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions, such as F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, or halogen fluorides (e.g., IF5, ClF3).

[0073] A fluorine radical source such as F2 gas may be 100% concentrated, but from a safety standpoint, it is preferably mixed with an inert gas and diluted to 5 to 50 mass %, more preferably 15 to 30 mass % for use. Examples of the inert gas include nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from an economical standpoint.

[0074] The conditions for the fluorination treatment are not particularly limited, and the copolymer in a molten state may be contacted with a fluorine-containing compound, but the treatment is usually carried out at a temperature below the melting point of the copolymer, preferably 20 to 240°C, more preferably 100 to 220°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is preferably carried out by contacting an unfluorinated copolymer with fluorine gas (F2 gas).

[0075] A composition may be obtained by mixing the copolymer of the present disclosure with other components as needed, such as fillers, plasticizers, processing aids, release agents, pigments, flame retardants, lubricants, light stabilizers, weather stabilizers, conductive agents, antistatic agents, UV absorbers, antioxidants, foaming agents, fragrances, oils, softeners, and dehydrofluorination agents.

[0076] Examples of fillers include silica, kaolin, clay, organoclay, talc, mica, alumina, calcium carbonate, calcium terephthalate, titanium oxide, calcium phosphate, calcium fluoride, lithium fluoride, cross-linked polystyrene, potassium titanate, carbon, boron nitride, carbon nanotubes, and glass fibers. Examples of conductive agents include carbon black. Examples of plasticizers include dioctyl phthalate and pentaerythritol. Examples of processing aids include carnauba wax, sulfone compounds, low-molecular-weight polyethylene, and fluorine-based aids. Examples of dehydrofluorination agents include organic oniums and amidines.

[0077] As the other component, a polymer other than the above-mentioned copolymer may be used, such as a fluororesin, a fluororubber, or a non-fluorinated polymer other than the above-mentioned copolymer.

[0078] Examples of methods for producing the composition include a method of dry mixing the copolymer and other components, and a method of previously mixing the copolymer and other components in a mixer and then melt-kneading them in a kneader, melt extruder, or the like.

[0079] The copolymers of the present disclosure or the above-described compositions can be used as processing aids, molding materials, etc., but are preferably used as molding materials. Aqueous dispersions, solutions, suspensions, and copolymer / solvent systems of the copolymers of the present disclosure are also available, and these can be used for coating applications, encapsulation, impregnation, and film casting. However, because the copolymers of the present disclosure have the above-described properties, they are preferably used as molding materials.

[0080] The copolymer of the present disclosure or the above-described composition may be molded to obtain a molded article.

[0081] The method for molding the copolymer or the composition is not particularly limited, and examples thereof include injection molding, extrusion molding, compression molding, blow molding, transfer molding, roto-molding, and roto-lining molding.Among the molding methods, compression molding, injection molding, extrusion molding, and transfer molding are preferred, and injection molding and extrusion molding are more preferred because they can produce molded articles with high productivity, and injection molding is even more preferred.That is, the molded article is preferably a compression molded article, an injection molded article, an extrusion molded article, or a transfer molded article, and is more preferably an injection molded article or an extrusion molded article because they can be produced with high productivity, and is even more preferably an injection molded article.

[0082] The shape of the molded article is not particularly limited, and may be, for example, a hose, a pipe, a tube, a wire coating, a sheet, a seal, a gasket, a packing, a film, a tank, a roller, a bottle, a container, or the like.

[0083] The copolymer of the present disclosure, the above-described composition, or the above-described molded article can be used, for example, in the following applications. 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 for fluid transfer lines used in pharmaceutical manufacturing processes, packings, sealing materials, sheets and other chemical liquid transfer components; Inner lining materials for chemical tanks and pipes in chemical plants and semiconductor factories; O-rings, tubes, packings, valve core materials, hoses, seals, etc. used in automobile fuel systems and peripheral devices, as well as fuel transfer components such as hoses and seals used in automobile automatic transmission systems; Carburetor flange gaskets, shaft seals, valve stem seals, sealing materials, hoses, etc. used in automobile engines and peripheral devices, automobile brake hoses, air conditioner hoses, radiator hoses, electrical wire coating materials, and other automobile parts; Semiconductor manufacturing equipment O-rings, tubes, packing, valve core materials, hoses, seal materials, rolls, gaskets, diaphragms, joints and other chemical liquid transfer components for semiconductor devices; Paint rolls for painting equipment, hoses, tubes, ink containers and other paint and ink components; Food and beverage transport components such as tubes and hoses for food and beverages, hoses, belts, packings, and joints, food packaging materials, and glass cooking equipment; Waste liquid transport components such as tubes and hoses for transporting waste liquid; High-temperature liquid transport components such as tubes and hoses for transporting high-temperature liquids; Steam piping components such as steam piping tubes and hoses; Anticorrosion tapes for piping, such as tapes wrapped around piping on ship decks, etc.; Various coating materials such as electrical wire coating materials, optical fiber coating materials, transparent surface coating materials and backing materials to be applied to the light incident surface of photovoltaic elements in solar cells; Sliding parts such as diaphragms for diaphragm pumps and various packings; Agricultural films, weather-resistant covers for various roofing materials and side walls; Interior materials used in the construction industry, and glass covering materials such as non-flammable fire-resistant safety glass; Lining materials such as laminated steel sheets used in the home appliance sector;

[0084] Further examples of the fuel transfer members used in the fuel systems of the above-mentioned automobiles include fuel hoses, filler hoses, evaporation hoses, etc. The above-mentioned fuel transfer members can also be used as fuel transfer members for sour gasoline, alcohol-resistant fuels, and fuels containing gasoline additives such as methyl tertiary butyl ether-resistant and amine-resistant.

[0085] The chemical stoppers and packaging films for chemicals have excellent chemical resistance to acids, etc. Another example of the chemical liquid transfer member is anticorrosion tape that is wrapped around pipes in chemical plants.

[0086] Examples of the molded article include automobile radiator tanks, chemical tanks, bellows, spacers, rollers, gasoline tanks, containers for transporting waste liquids, containers for transporting high-temperature liquids, and tanks for fishing and fish farming.

[0087] Further examples of the molded article include components used for automobile bumpers, door trims, instrument panels, food processing equipment, cooking appliances, water- and oil-repellent glass, lighting-related equipment, display panels and housings for office automation equipment, illuminated signs, displays, liquid crystal displays, mobile phones, printed circuit boards, electric and electronic components, miscellaneous goods, trash cans, bathtubs, modular baths, ventilation fans, lighting frames, etc.

[0088] The molded article containing the copolymer of the present disclosure has excellent heat resistance and moderate hardness even at high temperatures, so that even when it is made into a thin-walled molded article, it exhibits sufficient impact resilience.In addition, the molded article containing the copolymer of the present disclosure has excellent crack resistance and abrasion resistance at high temperatures, is extremely low in water vapor permeability, is difficult for water vapor to penetrate, and has excellent sealing properties at high temperatures, so it can be suitably used as a compressed member containing the copolymer.

[0089] The compressed member of the present disclosure exhibits high surface pressure even when deformed at a high compression deformation rate. The compressed member of the present disclosure can be used in a state compressed and deformed at a compression deformation rate of 10% or more, and can be used in a state compressed and deformed at a compression deformation rate of 20% or more or 25% or more. By using the compressed member of the present disclosure after being deformed at such a high compression deformation rate, a certain level of resilience can be maintained for a long period of time, and sealing and insulating properties can be maintained for a long period of time.

[0090] The compressed member of the present disclosure exhibits a high storage modulus, a high recovery amount, and a high surface pressure even when deformed at a high compression deformation rate at high temperatures. The compressed member of the present disclosure can be used in a state compressed and deformed at 150°C or higher and a compression deformation rate of 10% or more, or in a state compressed and deformed at 150°C or higher and a compression deformation rate of 20% or more or 25% or more. By using the compressed member of the present disclosure after deforming it at such high temperatures and a high compression deformation rate, a certain level of rebound resilience can be maintained for a long period of time even at high temperatures, and sealing and insulating properties at high temperatures can be maintained for a long period of time.

[0091] The above-mentioned compressive deformation ratio is the compressive deformation ratio of the portion with the largest compressive deformation ratio when the compressed member is used in a compressed state. For example, when a flat compressed member is used in a state compressed in its thickness direction, it is the compressive deformation ratio in the thickness direction. Furthermore, for example, when the compressed member is used in a state where only a portion is compressed, it is the compressive deformation ratio of the portion with the largest compressive deformation ratio among the compressed portions.

[0092] The size and shape of the compressible member of the present disclosure may be appropriately set depending on the application and are not particularly limited. The shape of the compressible member of the present disclosure may be, for example, annular. Furthermore, the compressible member of the present disclosure may have a shape such as a circle, an oval, or a rectangle with rounded corners in a plan view, and may have a through hole in the center.

[0093] The compressible member of the present disclosure is preferably used as a member for constituting a nonaqueous electrolyte battery. The compressible member of the present disclosure has extremely low water vapor permeability, excellent crack resistance and abrasion resistance at high temperatures, is resistant to water vapor penetration, and has excellent sealing properties at high temperatures, making it particularly suitable as a member used in contact with the nonaqueous electrolyte in a nonaqueous electrolyte battery. In other words, the compressible member of the present disclosure may have a surface that comes into contact with the nonaqueous electrolyte in a nonaqueous electrolyte battery.

[0094] The compressible member of the present disclosure is less permeable to water vapor. Therefore, by using the compressible member of the present disclosure, it is possible to suppress the permeation of water vapor from the outside into the secondary battery. As a result, by using the compressible member of the present disclosure, it is possible to suppress the deterioration of battery performance and the shortening of the lifespan of the nonaqueous electrolyte battery.

[0095] The water vapor permeability of the compressible member of the present disclosure is preferably 7.0 g cm / m because this can further suppress deterioration of the battery performance and shortened life of the nonaqueous electrolyte battery. 2 Less than 6.8 g cm / m 2 Less than 6.6 g cm / m, more preferably 2 The water vapor permeability can be measured at 95°C for 30 days.

[0096] The compressible member of the present disclosure is resistant to water vapor penetration. Therefore, by using the compressible member of the present disclosure, it is possible to suppress the penetration of water vapor into a secondary battery from the outside. As a result, by using the compressible member of the present disclosure, it is possible to suppress the deterioration of battery performance and shortening of the lifespan of a non-aqueous electrolyte battery. The degree of water vapor penetration into the compressible member can be confirmed by the water vapor leakage rate described below.

[0097] The water vapor leakage rate of the compressible member of the present disclosure is preferably less than 0.0030 g / 1000 hrs, more preferably 0.0027 g / 1000 hrs or less, and even more preferably 0.0026 g / 1000 hrs or less, because this can further suppress deterioration of battery performance and shortened life of the nonaqueous electrolyte battery. When the water vapor leakage rate is within the above range, penetration of water vapor into the compressible member can be effectively suppressed. The water vapor leakage rate of the compressible member can be measured by the method described in the Examples.

[0098] When the copolymer has a specific range of functional groups, the compressible member of the present disclosure is less likely to release fluorine ions into the non-aqueous electrolyte. Therefore, by using the compressible member of the present disclosure, an increase in the fluorine ion concentration in the non-aqueous electrolyte can be suppressed. As a result, by using the compressible member of the present disclosure, the generation of gases such as HF in the non-aqueous electrolyte battery can be suppressed, and the deterioration of battery performance and shortened life of the non-aqueous electrolyte battery can be suppressed.

[0099] The compressible member of the present disclosure can further suppress the generation of gases such as HF in nonaqueous electrolyte batteries and can further suppress the deterioration of battery performance and shortened lifespan of nonaqueous electrolyte batteries. Therefore, the amount of eluted fluorine ions detected in an electrolyte immersion test is preferably 1 ppm or less, more preferably 0.8 ppm or less, and more preferably 0.7 ppm or less, by mass. The amount of eluted fluorine ions can be adjusted by the number of functional groups in the copolymer contained in the compressible member. The electrolyte immersion test can be performed by using the compressible member to prepare a test piece having a weight equivalent to 10 molded bodies (15 mm × 15 mm × 0.2 mm), placing the test piece and 2 g of dimethyl carbonate (DMC) in a glass sample bottle, and leaving it in a constant temperature bath at 80°C for 144 hours.

[0100] The nonaqueous electrolyte battery is not particularly limited as long as it is a battery containing a nonaqueous electrolyte, and examples thereof include a lithium ion secondary battery, a lithium ion capacitor, etc. Furthermore, examples of components constituting the nonaqueous electrolyte battery include a sealing member, an insulating member, etc.

[0101] The nonaqueous electrolyte may be one or more of known solvents, such as, but not limited to, propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyl lactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The nonaqueous electrolyte battery may further include an electrolyte. The electrolyte may be, but is not limited to, LiClO4, LiAsF6, LiPF6, LiBF4, LiCl, LiBr, CH3SO3Li, CF3SO3Li, cesium carbonate, or the like.

[0102] The compressible member of the present disclosure can be suitably used, for example, as a sealing member such as a sealing gasket or sealing packing, or an insulating member such as an insulating gasket or insulating packing. A sealing member is a member used to prevent leakage of liquid or gas or intrusion of liquid or gas from the outside. An insulating member is a member used for electrical insulation. The compressible member of the present disclosure may be a member used for both sealing and insulating purposes.

[0103] The compressed member of the present disclosure has excellent heat resistance and crack resistance at high temperatures, moderate hardness even at high temperatures, and excellent sealing properties at high temperatures, making it suitable for use in high-temperature environments. Furthermore, the copolymer of the present disclosure also has excellent thin-wall moldability, making it suitable for use as a thin-walled compressed member, such as a thin-walled gasket. As described above, the compressed member of the present disclosure has moderate hardness at high temperatures, so it exhibits sufficient impact resilience even when formed into a thin-walled molded body. The compressible member of the present disclosure is preferably used in an environment where the maximum temperature is 40° C. or higher. For example, the compressible member of the present disclosure is preferably used in an environment where the maximum temperature is 150° C. or higher. Examples of situations in which the compressible member of the present disclosure may reach such high temperatures include when the compressed member is attached to a battery in a compressed state and then other battery components are attached to the battery by welding, or when the nonaqueous electrolyte battery generates heat.

[0104] The compressible member of the present disclosure has excellent crack resistance and abrasion resistance at high temperatures, extremely low water vapor permeability, making it difficult for water vapor to penetrate, and moderate hardness even at high temperatures, providing excellent sealing properties at high temperatures. Therefore, it can be suitably used as a sealing member for a nonaqueous electrolyte battery or an insulating member for a nonaqueous electrolyte battery. For example, when a battery such as a nonaqueous electrolyte secondary battery is charged, the battery temperature may temporarily reach 40°C or higher, particularly 150°C or higher. The compressible member of the present disclosure does not lose its high resilience even when used in a battery such as a nonaqueous electrolyte secondary battery, where it is deformed at a high compressive deformation rate at high temperatures, and even when it comes into contact with a nonaqueous electrolyte at high temperatures. Therefore, when used as a sealing member, the compressible member of the present disclosure has excellent sealing properties and maintains these sealing properties for a long period of time.

[0105] When the copolymer has functional groups within a specific range, it has a low dielectric loss tangent at 6 GHz and can therefore be suitably used as a material for high-frequency signal transmission products.

[0106] The high-frequency signal transmission product is not particularly limited as long as it is a product used for transmitting high-frequency signals, and examples include (1) molded plates such as insulating plates for high-frequency circuits, insulators for connecting parts, and printed wiring boards, (2) molded articles such as bases for high-frequency vacuum tubes and antenna covers, and (3) coated electric wires such as coaxial cables and LAN cables. The high-frequency signal transmission product can be suitably used in devices that use microwaves, particularly microwaves of 3 to 30 GHz, such as satellite communication devices and mobile phone base stations.

[0107] In the above-mentioned high-frequency signal transmission product, when the copolymer has a number of functional groups within a specific range, it can be suitably used as an insulator because of its low dielectric loss tangent.

[0108] The (1) molded plate is preferably a printed wiring board because it can provide good electrical properties. Examples of the printed wiring board include, but are not limited to, printed wiring boards for electronic circuits in mobile phones, various computers, communication devices, etc. The (2) molded article is preferably an antenna cover because it has low dielectric loss.

[0109] The above-mentioned (3) coated electric wire is preferably a coated electric wire having a coating layer containing a copolymer having a number of functional groups within a specific range. That is, a molded article containing a copolymer having a number of functional groups within a specific range can be suitably used as the coating layer. The copolymer of the present disclosure has a very high storage modulus (E'), and therefore has appropriate hardness, so that even when made into a twisted electric wire, the coating layer is resistant to crushing and can withstand long-term use. Furthermore, when the copolymer has a number of functional groups within a specific range, a coated electric wire having a coating layer containing the copolymer has excellent electrical properties and the coating layer also has excellent insulating properties. Furthermore, the coating layer is resistant to softening even at high temperatures and has an appropriate hardness, so that the excellent electrical properties can be maintained even at high temperatures.

[0110] Commercially available tetrafluoroethylene / fluoro(alkyl vinyl ether) copolymers are known to have a continuous use temperature of 260° C. Continuous use temperature refers to the maximum operating temperature that the polymer can withstand continuously. In recent years, there has been a need for copolymers that can be used in more severe working environments, i.e., have continuous use temperatures exceeding 260° C. In many real-world industrial applications in oil and gas fields, there is an emerging need to have melt-processable polymeric materials with continuous use temperatures exceeding 260° C. to withstand the extremely high operating temperatures encountered in construction work, for example. For example, during deep drilling, data communication cables may be exposed to temperatures of 280° C. or higher in downhole wells. A molded article containing the copolymer of the present disclosure can have a continuous use temperature of 280°C. A molded article containing the copolymer of the present disclosure does not melt even at the extremely high temperature of 280°C, and the coating layer made of the molded article maintains its coating without forming ruptures or cracks due to thermal load, allowing for continuous use. Therefore, a molded article containing the copolymer of the present disclosure is suitable for use as a coating layer of a coated electric wire used in an environment with a maximum temperature of 280°C or higher.

[0111] The coated electric wire includes a core wire and a coating layer surrounding the core wire and containing the copolymer of the present disclosure. The coated electric wire has excellent heat resistance, and when the copolymer has a specific range of functional groups, has a low dielectric loss tangent, making it suitable for high-frequency transmission cables, flat cables, heat-resistant cables, and the like, and is particularly suitable for high-frequency transmission cables.

[0112] When the copolymer of the present disclosure has a specific range of functional groups, a coating layer having a uniform thickness and no film defects can be obtained, thereby obtaining a thin coating layer with better capacitance stability.

[0113] The core wire may be made of a metal conductor material such as copper or aluminum. The core wire preferably has a diameter of 0.02 to 3 mm. The core wire diameter is more preferably 0.04 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.1 mm or more. The core wire diameter is more preferably 2 mm or less.

[0114] Specific examples of the core wire include AWG (American Wire Gauge)-46 (solid copper wire with a diameter of 40 micrometers), AWG-26 (solid copper wire with a diameter of 404 micrometers), AWG-24 (solid copper wire with a diameter of 510 micrometers), and AWG-22 (solid copper wire with a diameter of 635 micrometers).

[0115] The thickness of the coating layer is preferably 0.1 to 3.0 mm, and more preferably 2.0 mm or less.

[0116] An example of a high-frequency transmission cable is a coaxial cable. A coaxial cable generally has a structure in which an inner conductor, an insulating coating layer, an outer conductor layer, and a protective coating layer are layered in this order from the core to the outer periphery. A molded article containing the copolymer of the present disclosure can be suitably used as an insulating coating layer containing a copolymer. The thickness of each layer in the above structure is not particularly limited, but typically the inner conductor has a diameter of about 0.1 to 3 mm, the insulating coating layer has a thickness of about 0.3 to 3 mm, the outer conductor layer has a thickness of about 0.5 to 10 mm, and the protective coating layer has a thickness of about 0.5 to 2 mm.

[0117] The coating layer may contain bubbles, and it is preferable that the bubbles are uniformly distributed in the coating layer.

[0118] The average bubble diameter of the bubbles is not limited, but is preferably 60 μm or less, more preferably 45 μm or less, even more preferably 35 μm or less, even more preferably 30 μm or less, particularly preferably 25 μm or less, and especially preferably 23 μm or less. The average bubble diameter is preferably 0.1 μm or more, more preferably 1 μm or more. The average bubble diameter can be determined by taking an electron microscope image of the cross section of the wire, calculating the diameter of each bubble through image processing, and averaging the results.

[0119] The coating layer may have an expansion rate of 20% or more, more preferably 30% or more, even more preferably 33% or more, and even more preferably 35% or more. There is no particular upper limit, but it is, for example, 80%. The upper limit of the expansion rate may be 60%. The expansion rate is a value calculated by ((specific gravity of wire coating material - specific gravity of coating layer) / specific gravity of wire coating material) × 100. The expansion rate can be adjusted appropriately depending on the application, for example, by adjusting the amount of gas introduced into the extruder described below, or by selecting the type of gas to be dissolved.

[0120] The covered electric wire may have another layer between the core wire and the covering layer, or may have another layer (outer layer) around the covering layer. When the covering layer contains bubbles, the electric wire of the present disclosure may have a two-layer structure (skin-foam) in which a non-foamed layer is inserted between the core wire and the covering layer, a two-layer structure (foam-skin) in which a non-foamed layer is covered on the outer layer, or even a three-layer structure (skin-foam-skin) in which a non-foamed layer is covered on a skin-foam outer layer. The non-foamed layer is not particularly limited and may be a resin layer made of a resin such as a TFE / HFP copolymer, a TFE / PAVE copolymer, a TFE / ethylene copolymer, a vinylidene fluoride polymer, a polyolefin resin such as polyethylene (PE), or polyvinyl chloride (PVC).

[0121] The coated electric wire can be produced, for example, by using an extruder to heat the copolymer and extrude the molten copolymer onto a core wire to form a coating layer.

[0122] When forming the coating layer, the copolymer may be heated and a gas may be introduced into the molten copolymer to form the coating layer containing bubbles. Examples of the gas that can be used include chlorodifluoromethane, nitrogen, carbon dioxide, and the like, or a mixture of the above gases. The gas may be introduced into the heated copolymer as a pressurized gas, or may be generated by mixing a chemical foaming agent into the copolymer. The gas dissolves in the molten copolymer.

[0123] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Example]

[0124] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0125] The values ​​in the examples and comparative examples were measured by the following methods.

[0126] (Monomer unit content) The content of each monomer unit was measured using an NMR analyzer (for example, AVANCE300 high temperature probe manufactured by Bruker Biospin).

[0127] (Melt flow rate (MFR)) According to ASTM D1238, the mass of polymer flowing out per 10 minutes (g / 10 minutes) from a nozzle with an inner diameter of 2.1 mm and a length of 8 mm under a load of 5 kg at 372°C was determined using a Melt Indexer G-01 (manufactured by Toyo Seiki Seisakusho, Ltd.).

[0128] (Number of functional groups) The copolymer pellets were molded by cold pressing to produce a film with a thickness of 0.25 to 0.30 mm. This film was scanned 40 times using a Fourier transform infrared spectrometer (FT-IR (Spectrum One, manufactured by PerkinElmer)) to obtain an infrared absorption spectrum. A difference spectrum was obtained from the base spectrum, which was completely fluorinated and had no functional groups. From the absorption peaks of specific functional groups that appeared in this difference spectrum, the carbon atom ratio of 1×10 in the sample was calculated according to the following formula (A): 6 The number of functional groups per molecule, N, was calculated. N=I×K / t (A) I: Absorbance K: Correction coefficient t: film thickness (mm) For reference, the absorption frequencies, molar extinction coefficients, and correction factors for the functional groups in this disclosure are shown in Table 2. The molar extinction coefficients were determined from FT-IR measurement data of low molecular weight model compounds.

[0129] [Table 2]

[0130] (Melting Point) Using a differential scanning calorimeter (product name: X-DSC7000, manufactured by Hitachi High-Tech Science Corporation), the sample was heated a first time from 200°C to 350°C at a heating rate of 10°C / min, then cooled from 350°C to 200°C at a cooling rate of 10°C / min, and then heated a second time from 200°C to 350°C at a heating rate of 10°C / min. The melting point was determined from the peak of the melting curve that appeared during the second heating process.

[0131] (glass transition temperature (Tg)) Dynamic viscoelasticity was measured using a dynamic viscoelasticity analyzer DVA-220 (manufactured by IT Measurement & Control Co., Ltd.) at a temperature rise rate of 2°C / min and a frequency of 10 Hz, and the temperature at the peak of the tan δ value was determined as the glass transition temperature.

[0132] Example 1 A 174 L autoclave was charged with 53.8 L of purified water and thoroughly purged with nitrogen. Then, 41.7 kg of perfluorocyclobutane, 0.57 kg of perfluoro(propyl vinyl ether) (PPVE), and 1.45 kg of methanol were added. The system temperature was maintained at 35°C and the stirring speed at 200 rpm. Tetrafluoroethylene (TFE) was then introduced under pressure to 0.5 MPa, and 0.224 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was added to initiate polymerization. As the polymerization progressed, the system pressure decreased, so TFE was continuously fed to maintain a constant pressure. PPVE was added at 0.029 kg for every 1 kg of TFE added, and the polymerization was continued for 7 hours. After releasing the TFE and returning the autoclave to atmospheric pressure, the resulting reaction product was washed with water and dried to obtain 30 kg of powder.

[0133] The resulting powder was melt-extruded at 360°C using a screw extruder (product name: PCM46, manufactured by Ikegai Corporation) to obtain pellets of a TFE / PPVE copolymer. The PPVE content of the resulting pellets was measured using the method described above. The results are shown in Table 3.

[0134] The resulting pellets were placed in a vacuum vibration reactor VVD-30 (manufactured by Okawara Manufacturing Co., Ltd.) and heated to 210°C. After evacuation, F2 gas diluted to 20% by volume with N2 gas was introduced until atmospheric pressure was reached. 0.5 hours after the introduction of F2 gas, the reactor was evacuated once and F2 gas was introduced again. 0.5 hours later, the reactor was evacuated again and F2 gas was introduced again. Thereafter, the above F2 gas introduction and evacuation operations were repeated once per hour, and the reaction was carried out at a temperature of 210°C for 10 hours. After the reaction was completed, the atmosphere inside the reactor was thoroughly replaced with N2 gas to terminate the fluorination reaction. Various physical properties of the fluorinated pellets were measured using the methods described above. The results are shown in Table 3.

[0135] Example 2 Non-fluorinated pellets were obtained in the same manner as in Example 1, except that 0.55 kg of PPVE, 1.65 kg of methanol, 0.028 kg of PPVE was added for every 1 kg of TFE fed, and the polymerization time was changed to 8 hours. The results are shown in Table 3.

[0136] Example 3 Fluorinated pellets were obtained in the same manner as in Example 1, except that the amounts of PPVE and methanol were changed to 0.49 kg and 1.69 kg, respectively, and 0.025 kg of PPVE was added for every 1 kg of TFE supplied. The results are shown in Table 3.

[0137] Example 4 Fluorinated pellets were obtained in the same manner as in Example 1, except that 0.55 kg of PPVE, 1.62 kg of methanol, 0.028 kg of PPVE was added for every 1 kg of TFE fed, and the polymerization time was changed to 8 hours. The results are shown in Table 3.

[0138] Example 5 Fluorinated pellets were obtained in the same manner as in Example 1, except that 0.55 kg of PPVE, 1.69 kg of methanol, 0.028 kg of PPVE was added for every 1 kg of TFE fed, and the polymerization time was changed to 8 hours. The results are shown in Table 3.

[0139] Comparative Example 1 Fluorinated pellets were obtained in the same manner as in Example 1, except that 0.53 kg of PPVE, 1.83 kg of methanol, 0.027 kg of PPVE was added for every 1 kg of TFE fed, and the polymerization time was changed to 8 hours. The results are shown in Table 3.

[0140] Comparative Example 2 A 4.11 L autoclave was charged with 1.224 L of purified water and thoroughly purged with nitrogen. Then, 967 g of perfluorocyclobutane, 6.7 g of perfluoro(propyl vinyl ether) (PPVE), and 142 g of methanol were added. The system temperature was maintained at 35°C and the stirring speed at 483 rpm. Tetrafluoroethylene (TFE) was then introduced under pressure to 0.64 MPa, and 2.4 g of a 50% methanol solution of di-n-propyl peroxydicarbonate was then added to initiate polymerization. As the polymerization progressed, the system pressure decreased, so TFE was continuously added to maintain a constant pressure. PPVE was added at a rate of 0.016 g for every 1 g of TFE added. The polymerization was terminated when the amount of TFE added reached 580 g. The unreacted TFE was released, and the autoclave was returned to atmospheric pressure. The resulting reaction product was then washed with water and dried to yield 584 g of powder.

[0141] The obtained powder was melt-extruded at 360°C using a 14φ screw extruder (manufactured by Imoto Machinery Co., Ltd.) to obtain copolymer pellets. The PPVE content of the obtained pellets was measured using the method described above. The results are shown in Table 3.

[0142] Comparative Example 3 Non-fluorinated pellets were obtained in the same manner as in Example 1, except that the amounts of PPVE and methanol were changed to 0.42 kg and 1.23 kg, respectively, and 0.021 kg of PPVE was added for every 1 kg of TFE supplied. The results are shown in Table 3.

[0143] Comparative Example 4 Fluorinated pellets were obtained in the same manner as in Example 1, except that the amounts of pure water, perfluorocyclobutane, PPVE, and methanol were changed to 26.6 L, 30.4 kg, 0.77 kg, and 4.80 kg, TFE was pressurized to 0.58 MPa, 0.011 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was added, and 0.031 kg of PPVE was added for every 1 kg of TFE fed, and the polymerization time was changed to 10.5 hours, resulting in 15 kg of powder. The results are shown in Table 3.

[0144] [Table 3]

[0145] In Table 3, the notation "<6" means that the number of functional groups is less than 6.

[0146] The pellets thus obtained were then evaluated for the following properties, the results of which are shown in Table 4.

[0147] (Water vapor permeability) Using the pellets and a heat press molding machine, a sheet-like test piece with a thickness of approximately 0.2 mm was prepared. The test cup (permeation area 12.56 cm) 2 18g of water was placed in a container, covered with a sheet test piece, and a PTFE gasket was placed between the test pieces and tightened to seal. The sheet test piece was left in contact with the water at a temperature of 95°C for 30 days, then removed and left at room temperature for 2 hours before measuring the mass loss. The water vapor permeability (g·cm / m) was calculated using the following formula: 2 ) was measured. Water vapor permeability (g·cm / m 2 ) = mass loss (g) × thickness of sheet specimen (cm) / permeation area (m 2 ) In Table 4, the term "crack" means that the test piece had poor crack resistance against compressive stress and cracks occurred in the test piece during the test.

[0148] (Water vapor leakage test) Using an injection molding machine (SE50EV-A manufactured by Sumitomo Heavy Industries, Ltd.), the copolymer was injection molded at a cylinder temperature of 350 to 385°C and a mold temperature of 150 to 200°C to obtain a gasket with an outer diameter of Φ17.7 mm, an inner diameter of Φ14.3 mm, and a thickness of 1.6 mm. As shown in Figure 1, 2 g of water was placed in an aluminum alloy cup 1. A gasket 7 was placed between the cup 1 and a gasket compression jig 3, and a lid 4 was fastened with bolts 5 to compress the gasket 7. A spacer 6 was placed between the lid 4 and the cup 1, and the compression deformation rate of the gasket 7 was adjusted to 50%. The mass of the test jig 10 thus obtained was measured. The test jig 10 was placed in a thermostatic chamber heated to 95°C and left for 1000 hours, then removed and left at room temperature for 2 hours, after which the mass was measured. The water vapor leakage rate was calculated using the following formula. This procedure was repeated five times, and the average water vapor leakage rate was calculated. The average values ​​are shown in Table 4. Water vapor leakage (g / 1000h) = (mass of test jig before heating) - (mass of test jig after heating)

[0149] (Restored amount) Approximately 2 g of the pellets were placed in a mold (inner diameter 13 mm, height 38 mm) and melted at 370°C for 30 minutes using a hot plate press, then water-cooled while applying a pressure of 0.2 MPa (resin pressure) to produce a molded body approximately 8 mm in height. Test pieces with an outer diameter of 13 mm and a height of 6 mm were then cut from the molded body.

[0150] The prepared test specimen was compressed at room temperature using a compression device to a compression deformation rate of 50% (i.e., a 6 mm high test specimen was compressed to a height of 3 mm). The compressed test specimen was fixed to the compression device and placed in an electric furnace at 150°C for 18 hours. The compression device was removed from the electric furnace, cooled to room temperature, and the test specimen was removed. The recovered test specimen was left at room temperature for 30 minutes, after which the height of the recovered test specimen was measured and the recovery amount was calculated using the following formula. Recovery amount (mm) = t2 - t1 t1: Spacer height (mm) t2: Height of the test piece removed from the compression device (mm) In the above test, t1=3 mm.

[0151] (Storage modulus (E')) Dynamic viscoelasticity was measured using a DVA-220 (manufactured by IT Measurement & Control Co., Ltd.) A heat-press molded sheet measuring 25 mm in length, 5 mm in width, and 0.2 mm in thickness was used as a sample test piece. Measurements were performed in the range of 30°C to 250°C at a heating rate of 2°C / min and a frequency of 10 Hz, and the storage modulus (MPa) at 150°C was read.

[0152] (Surface pressure at 150℃) From the results of the compression test at 150°C and the results of the storage modulus measurement at 150°C, the 150°C surface pressure was calculated using the following formula. 150℃ surface pressure (MPa) = (t2-t1) / t1×E' t1: Spacer height (mm) t2: Height of the test piece removed from the compression device (mm) E': Storage modulus at 150°C (MPa)

[0153] (Barflow test) Using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., product name SG50), the pellets were injected into a spiral bar flow mold (mold size: 152.5 mm × 152.5 mm, cavity thickness: 1 mm, cavity width: 23 mm) under conditions of a cylinder temperature of 370°C, a mold temperature of 150°C, and an injection speed of 10 mm / s or 15 mm / s, to obtain an injection-molded article. The length (bar flow length) of the obtained injection-molded article was measured.

[0154] (Surface smoothness) The copolymer was injection molded using an injection molding machine (SE50EV-A, manufactured by Sumitomo Heavy Industries, Ltd.) with a cylinder temperature of 390°C, a mold temperature of 170°C, and an injection speed of 50 mm / s. The mold used was a Cr-plated HPM38 mold (100 mm x 100 mm x 2.5 mm, side gate). The surfaces of the injection-molded articles were visually observed, and the surface smoothness was evaluated according to the following criteria. ◎: No roughness is observed on the surface and it is smooth. ○: Roughness is observed only on the surface of the part located near the gate of the mold. ×: Roughness is observed on most of the surface

[0155] (Wire coating characteristics) The pellets obtained in each of the Examples and Comparative Examples were used to obtain coated electric wires using an extruder. The conditions for the wire coating extrusion molding are as follows. a) Core conductor: soft steel wire AWG24 (American Wire Gauge) core diameter 20.1 mil b) Coating thickness: 7.2 mil c) Insulated wire diameter: 34.5mil d) Wire withdrawal speed: 1850 feet / minute e) Melt molding (extrusion) conditions: Single-screw extruder with a cylinder diameter of 2 inches and an L / D ratio of 30 Die (inner diameter) / chip (outer diameter) = 8.71mm / 4.75mm · Extruder temperature settings: Barrel section Z1 (338°C), barrel section Z2 (360°C), barrel section Z3 (371°C), barrel section Z4 (382°C), barrel section Z5 (399°C), clamp section (404°C), adapter section (404°C), crosshead section (404°C), die section (404°C), core wire preheating was set to 140°C.

[0156] The capacitance stability and continuous formability of the coated electric wire obtained were evaluated. (1) Continuous molding The wire coating was continuously formed, and if the coating broke at least once per hour, it was judged as impossible to form continuously (×), and if no coating breakage occurred, it was judged as possible to form continuously (◯). (2) Capacitance stability The capacitance was measured for 1 hour using a capacitance measuring device, Capac HS (Type: MR20.50HS, manufactured by Zumbach), and the result was calculated as the process capability index (Cp). The Cp was sequentially stored in a USYS 2000 (manufactured by Zumbach), and analyzed by setting the upper limit (USL) to +1.0 (pf / inch) and the lower limit (LSL) to -1.0 (pf / inch). The average capacitance variation per 30,000 m is shown. The symbol "x" in the table means that cone breakage occurred and the capacitance fluctuation width could not be determined.

[0157] (Mold corrosion test) 20 g of pellets were placed in a glass container (50 ml screw tube), and a metal pillar (5 mm square, 30 mm long) made of HPM38 (Cr-plated) or HPM38 (Ni-plated) was hung from the glass container so as not to touch the pellets. The glass container was then covered with aluminum foil. The glass container was placed in an oven in this state and heated at 380°C for 3 hours. The heated glass container was then removed from the oven and cooled to room temperature, and the degree of corrosion on the surface of the metal pillar was visually observed. The degree of corrosion was evaluated according to the following criteria. ○: No corrosion observed △: Slight corrosion observed ×: Corrosion is observed

[0158] (Electrolyte immersion test) Approximately 5 g of the pellets were placed in a mold (inner diameter 120 mm, height 38 mm) and melted at 370°C for 20 minutes using a hot plate press. After that, the molded product was water-cooled while being pressed at a pressure of 1 MPa (resin pressure) to produce a molded product with a thickness of approximately 0.2 mm. Test pieces measuring 15 mm square were then prepared using the molded product.

[0159] Ten of the obtained test pieces and 2 g of electrolyte (dimethyl carbonate (DMC)) were placed in a 20 mL glass sample bottle, and the lid of the sample bottle was closed. The sample bottle was placed in a thermostatic chamber at 80 °C and left for 144 hours to immerse the test pieces in the electrolyte. The sample bottle was then removed from the thermostatic chamber and cooled to room temperature, after which the test pieces were removed from the sample bottle. The remaining electrolyte after removing the test pieces was air-dried in a room controlled at 25 °C for 24 hours, and 2 g of ultrapure water was added. The obtained aqueous solution was transferred to the measurement cell of an ion chromatography system, and the amount of fluoride ions in this aqueous solution was measured using an ion chromatography system (Dionex ICS-2100, manufactured by Thermo Fisher Scientific).

[0160] (dielectric tangent) The pellets were melt-molded to prepare cylindrical test pieces with a diameter of 2 mm. The test pieces were placed in a 6 GHz cavity resonator manufactured by Kanto Electronics Application Development Co., Ltd., and measured using a network analyzer manufactured by Agilent Technologies. The measurement results were analyzed using the analysis software "CPMA" manufactured by Kanto Electronics Application Development Co., Ltd. on a PC connected to the network analyzer, and the dielectric loss tangent (tanδ) at 20°C and 6 GHz was determined.

[0161] (wear test) Using pellets and a heat press, sheet-like test specimens approximately 0.2 mm thick were prepared and cut into 10 cm x 10 cm test specimens. The prepared test specimens were fixed to the test table of a Taber abrasion tester (No. 101 Special Taber Abrasion Tester, manufactured by Yasuda Seiki Seisakusho Co., Ltd.), and an abrasion test was performed using the Taber abrasion tester under the following conditions: a load of 500 g, an abrasion wheel CS-10 (ground 20 times with abrasive paper #240), and a rotation speed of 60 rpm. The weight of the test specimen was measured after 1,000 rotations, and then again after another 10,000 rotations using the same test specimen. The abrasion loss was calculated using the following formula: Wear amount (mg)=M1-M2 M1: Test piece weight (mg) after 1000 rotations M2: Test piece weight (mg) after 10,000 rotations

[0162] (Crack test) Using the pellets and a heat press molding machine, a 1.8 mm thick sheet-like test piece (5 mm wide) was prepared. The obtained sheet-like test piece was folded at 90° and left at 150°C for 2 hours. The surface of the cooled sheet-like test piece was visually observed and evaluated according to the following criteria. 〇: No cracks ×: Cracks present

[0163] [Table 4] [Explanation of symbols]

[0164] 10 Test fixture 1 cup 2 water 3 Gasket compression jig 4 Lid 5 volts 6 spacers 7 Gasket

Claims

1. Contains tetrafluoroethylene units and perfluoro(propyl vinyl ether) units, the content of perfluoro(propyl vinyl ether) units is 2.0 to 2.8 mass% based on the total monomer units; The content of tetrafluoroethylene units is 97.2 to 98.0 mass% based on the total monomer units, The melt flow rate, measured in accordance with ASTM D1238 using a melt indexer and expressed as the mass of polymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes under a load of 5 kg at 372°C, is 23 to 30 g / 10 min. Copolymer.

2. -CF = CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of functional groups, which is the total number of OH groups, is 10 main chain carbon atoms. ６ The copolymer according to claim 1, wherein the number of the hydroxyl groups per unit area is 50 or less.

3. 3. The copolymer according to claim 1, having a melting point of 305 to 315°C.

4. An injection-molded article comprising the copolymer according to any one of claims 1 to 3.

5. A compressed member comprising the copolymer according to any one of claims 1 to 3.

6. A coated electric wire having a coating layer containing the copolymer according to any one of claims 1 to 3.

7. An aqueous dispersion containing the copolymer according to any one of claims 1 to 3.

8. A paint containing the copolymer according to any one of claims 1 to 3.

9. An extrusion molded article comprising the copolymer according to any one of claims 1 to 3.

10. A pellet containing the copolymer according to any one of claims 1 to 3.

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