Copolymers, compositions, molded articles, and coated wires

Abstract

Provided are: a copolymer that makes it possible to form a coated wire having excellent resistance to engine oil; a composition; a molded body; and a coated wire.　The copolymer includes a unit based on ethylene, a unit based on tetrafluoroethylene, and a unit based on a compound A represented by CH2=CX(CF2)nY (in the formula, X and Y each independently represent a hydrogen atom or a fluorine atom, and n is an integer of 2-6) or a compound B represented by CF2=CF-O-C3F7. The copolymer has a crystal lamella thickness of 4.0 nm or less as determined by small angle X-ray scattering, and the melting point is at least 245ºC.

Description

Technical Field

[0001] The present invention relates to a copolymer, a composition, a molded article, and a coated electric wire.

Background Art

[0002] Ethylene / tetrafluoroethylene copolymer (hereinafter also referred to as "ETFE") is excellent in heat resistance, weather resistance, electrical insulation, non-stickiness, water / oil repellency, etc., and has characteristics of high moldability and mechanical strength among fluororesins. Therefore, various molded articles such as wire coatings, tubes, sheets, films, filaments, pump casings, joints, packings, linings, coatings, etc. are manufactured by melt molding methods such as extrusion molding, blow molding, injection molding, rotational molding, etc. For example, Patent Document 1 discloses a composition having a copolymer having units based on ethylene, units based on tetrafluoroethylene, and units based on other monomers, and copper oxide.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An automotive coated electric wire has a conductor and a coating layer disposed on the surface of the conductor, and tetrafluoroethylene / hexafluoropropylene copolymer (hereinafter also referred to as "FEP") is widely used to form the coating layer. Among these, in recent years, from the viewpoint of weight reduction of automobiles, etc., using ETFE instead of FEP has been considered. When the present inventors evaluated a coated electric wire having a coating layer formed using ETFE as described in Patent Document 1, they found that there is room for improvement in engine oil resistance.

[0005] Therefore, the object of the present invention is to provide a copolymer, composition, molded article, and coated wire that can form coated wires with excellent engine oil resistance. [Means for solving the problem]

[0006] As a result of diligent research into the above-mentioned problems, the present inventors have discovered that a coated electric wire with excellent engine oil resistance can be obtained by using a copolymer that includes units based on ethylene, units based on tetrafluoroethylene, and units based on formula (A) or formula (B) described below, having a crystal lamellar thickness of 4.0 nm or less and a melting point of 245°C or higher. This led to the present invention.

[0007] In other words, the inventors found that the above problem could be solved by the following configuration. [1] A copolymer comprising a unit based on ethylene, a unit based on tetrafluoroethylene, and a unit based on a compound represented by formula (A) or a compound represented by formula (B), A copolymer characterized by having a crystal lamellar thickness of 4.0 nm or less, as determined by small-angle X-ray scattering, and a melting point of 245°C or higher. CH2=CX(CF2) n Y-type (A) CF2 = CF - O - C3F7 Equation (B) In equation (A), X and Y are independently either a hydrogen atom or a fluorine atom, and n is an integer between 2 and 6.

[0008] [2] The copolymer according to claim 1, wherein the M value of the copolymer, which can be calculated by the following method, is 0.20 or less. Calculation method: The M value is calculated using the molten copolymer at 400 MHz. 19 This value is calculated using the following formula (1) based on the chart obtained by F-NMR measurement. M value = C1 / B1 Equation (1) B1: Integral value of peaks observed in the chemical shift range of -100 to -115 ppm C1: Integral value of the peak observed in the chemical shift range of -118.5 to -122 ppm The chemical shifts in B1 and C1 are observed when the chemical shift of the CF2 peak at the position where two consecutive tetrafluoroethylene-based units of the copolymer directly bond with one tetrafluoroethylene-based unit and the other tetrafluoroethylene-based unit is set to -120 ppm. However, B1 does not include the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm originating from the compound represented by formula (A) and the compound represented by formula (B). Also, C1 does not include the integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm originating from the compound represented by formula (A) and the compound represented by formula (B).

[0009] [3] The copolymer according to [1] or [2], wherein the content of the tetrafluoroethylene-based units is 40 to 65 mol% of the total units contained in the copolymer. [4] The copolymer according to any one of [1] to [3], wherein the content of the ethylene-based units is 35 to 60 mol% of the total units contained in the copolymer. [5] The copolymer according to any one of [1] to [4], wherein the copolymer comprises a unit based on ethylene, a unit based on tetrafluoroethylene, and a unit based on a compound represented by formula (A). [6] The copolymer according to any one of [1] to [5], wherein the copolymer contains units based on the compound represented by formula (A), and the content of the units based on the compound represented by formula (A) is 1 to 5 mol% of the total units contained in the copolymer. [7] The copolymer according to any one of [1] to [4], wherein the copolymer contains units based on the compound represented by formula (B), and the content of the units based on the compound represented by formula (B) is 1 to 5 mol% of the total units contained in the copolymer. [8] The copolymer according to any one of [1] to [7], wherein the melt flow rate of the copolymer, as measured under conditions of a temperature of 297°C and a load of 49N in accordance with ASTM D3159, is 15 to 60 g / 10 min.

[0010] A composition characterized by comprising a copolymer and an additive as described in any of [9] [1] to [8].

[10] The composition according to [9], comprising a heat stabilizer as the additive.

[11] The composition according to

[10] , wherein the heat stabilizer is a copper compound.

[12] The composition according to any one of [9] to

[11] , comprising an antioxidant as the additive. A molded article characterized by being obtained by molding a copolymer according to any one of [1] to [8], or a composition according to any one of [9] to

[12] .

[14] A covered electric wire, characterized by comprising a conductor and a covering layer disposed on the surface of the conductor, which is formed from a copolymer according to any one of [1] to [8] or a composition according to any one of [9] to

[12] . [Effects of the Invention]

[0011] According to the present invention, copolymers, compositions, molded articles, and coated wires can be provided that can form coated wires with excellent engine oil resistance. [Brief explanation of the drawing]

[0012] [Figure 1] This chart was obtained when a copolymer according to one embodiment of the present invention was subjected to 19F-NMR measurement. [Figure 2] This chart was obtained when a copolymer according to one embodiment of the present invention was subjected to 19F-NMR measurement. [Figure 3] This chart was obtained when a copolymer according to one embodiment of the present invention was subjected to 19F-NMR measurement. [Figure 4] This chart was obtained when a copolymer according to one embodiment of the present invention was subjected to 19F-NMR measurement. [Figure 5] This chart was obtained when a copolymer according to one embodiment of the present invention was subjected to 19F-NMR measurement. [Modes for carrying out the invention]

[0013] The meanings of the terms used in this invention are as follows: In a polymer, a "unit" refers to an atomic group derived from one monomer molecule, directly formed by the polymerization of monomers, and also refers to an atomic group obtained by chemically transforming a portion of the above atomic group after polymerization. In the following, units derived from individual monomers will be referred to by adding "unit" to the monomer name, as appropriate. "TFE units" refer to units based on tetrafluoroethylene in polymers, and "E units" refer to units based on ethylene in polymers.

[0014] A "TFE2 chain structure" refers to a structure in a copolymer where two TFE units are consecutive between E units, in the arrangement of TFE and E units. TFE-TFE This refers to the underlined part of the structure represented by "-E-". In chemical formula, it is written as "-CH2-CH2-". CF 2 -CF 2 -CF 2 -CF This refers to the underlined portion of the structure represented as "2-CH2-CH2-".

[0015] "CF2 on the CF2 side in the TFE2 chain structure" refers to the CF2 in the structure represented as "-CH2-CH2-CF2-CF2-CF2-CF2-CH2-CH2-" that has the following (b) appended to it. "-CH2-CH2-CF2-CF2 (b) -CF2 (b) -CF2-CH2-CH2-"

[0016] "CH2-side CF2 in TFE2 chain structure" refers to the CF2 in the structure represented as "-CH2-CH2-CF2-CF2-CF2-CF2-CH2-CH2-" that has the following (c) appended to it. "-CH2-CH2-CF2(c) -CF2-CF2-CF2 (c) -CH2-CH2-"

[0017] A "TFE-E alternating structure" refers to a structure in a copolymer where TFE units and E units are arranged alternately in a continuous sequence, and is represented as "-TFE-E-". In chemical formula, it is represented as "-CF2-CF2-CH2-CH2-".

[0018] "CF2 in the TFE-E alternating structure" refers to the CF2 within "-CF2-CF2-CH2-CH2-" that has the following (a) appended to it. "-CF2 (a) -CF2 (a) -CH2-CH2-"

[0019] [Copolymer] The copolymer of the present invention (hereinafter also referred to as "this copolymer") contains E units, TFE units, and units based on formula (A) or formula (B) described below. Furthermore, this copolymer has a crystal lamellar thickness of 4.0 nm or less as determined by small-angle X-ray scattering and a melting point of 245°C or higher.

[0020] This copolymer can form coated wires with excellent engine oil resistance. While the exact reasons for this are still unclear, it is presumed to be due to the following: In this invention, engine oil resistance is evaluated by whether or not cracks occur in the coating layer after immersing a coated wire having a coating layer obtained using a copolymer in engine oil and leaving the coated wire standing for a long period of time at a high temperature. One reason why this copolymer can form coated wires with excellent engine oil resistance is thought to be that it uses a copolymer with a crystal lamellar thickness of 4.0 nm or less and a melting point of 245°C or higher. In other words, it is thought that if the crystalline lamellar thickness of the copolymer is small, the rigidity of the coating layer of the coated wire formed using the copolymer will decrease. This is presumed to have suppressed the occurrence of cracks in the coating layer. In addition, due to the high melting point of the copolymer, it is considered that the thermal damage to the coating layer is reduced during the evaluation of engine oil resistance performed at high temperatures. Thereby, it is presumed that the generation of cracks in the coating layer was suppressed. Thus, by specifying the crystal lamella thickness and melting point of the copolymer, it is presumed that the effects of each physical property act synergistically to obtain a coated electric wire excellent in engine oil resistance.

[0021] This copolymer is a copolymer containing an E unit, a TFE unit, a unit based on a compound represented by formula (A) (hereinafter also referred to as "compound A") (hereinafter also referred to as "A unit"), or a unit based on a compound represented by formula (B) (hereinafter also referred to as "compound B") (hereinafter also referred to as "B unit").

[0022] CH2=CX(CF2) n Y Formula (A) CF2=CF-O-C3F7 Formula (B)

[0023] In formula (A), X and Y are each independently a hydrogen atom or a fluorine atom. From the viewpoint of polymerizability, X is preferably a hydrogen atom. From the viewpoint of heat resistance, Y is preferably a fluorine atom. n is an integer of 2 to 6. As the compound A, CH2=CH(CF2)2F, CH2=CH(CF2)4F, CH2=CH(CF2)6F, CH2=CF(CF2)4F, and CH2=CF(CF2)3H are preferable, and CH2=CH(CF2)4F (hereinafter also referred to as "PFBE") is particularly preferable, from the viewpoint of more excellent engine oil resistance.

[0024] This copolymer preferably has an E unit, a TFE unit, and an A unit, from the viewpoint of being excellent in abrasion resistance and stress crack resistance.

[0025] The E unit content is preferably 35 to 60 mol%, more preferably 40 to 55 mol%, even more preferably 44 to 52 mol%, and particularly preferably 45 to 50 mol%, relative to the total units contained in the copolymer. If the content is 35 mol% or more, the mechanical properties and engine oil resistance are better, and if it is 60 mol% or less, the heat resistance is better.

[0026] The TFE unit content is preferably 40 to 65 mol%, more preferably 45 to 60 mol%, even more preferably 48 to 56 mol%, and particularly preferably 50 to 54 mol%, relative to the total units contained in the copolymer. If the content is 40 mol% or more, the heat resistance is better, and if it is 65 mol% or less, the mechanical properties and engine oil resistance are better.

[0027] If the copolymer contains A units, the A unit content is preferably 1 to 5 mol%, more preferably 2 to 4 mol%, and particularly preferably 2.5 to 3.5 mol%, relative to the total units contained in the copolymer. If the A unit content is 1 mol% or more, the crystalline lamellar thickness of the copolymer can be reduced, and if it is 5 mol% or less, the melting point of the copolymer can be increased.

[0028] If the copolymer contains B units, the B unit content is preferably 1 to 5 mol%, more preferably 2 to 4 mol%, and particularly preferably 2.5 to 3.5 mol%, relative to the total units contained in the copolymer. If the B unit content is 1 mol% or more, the crystalline lamellar thickness of the copolymer can be reduced, and if it is 5 mol% or less, the melting point of the copolymer can be increased.

[0029] The copolymer preferably contains 40-64 mol% TFE units, 35-59 mol% E units, and 1-5 mol% A units; more preferably 45-58 mol% TFE units, 40-53 mol% E units, and 2-4 mol% A units; and even more preferably 48-53.5 mol% TFE units, 44-49.5 mol% E units, and 2.5-3.5 mol% A units.

[0030] <Crystal lamellar thickness> The crystalline lamellar thickness of this copolymer is 4.0 nm or less, preferably 3.95 nm or less, more preferably 3.9 nm or less, and particularly preferably 3.85 nm or less, as it offers superior engine oil resistance. Furthermore, the crystalline lamellar thickness of this copolymer is preferably 2.0 nm or more, more preferably 2.5 nm or more, and particularly preferably 3.0 nm or more, in order to maintain the copolymer's excellent mechanical strength and melting point. A specific example of a method for adjusting the crystalline lamellar thickness of this copolymer within the above range is a method of adjusting the content of A units and B units in this copolymer. The crystalline lamellar thickness of this copolymer is measured by small-angle X-ray scattering (SAXS), specifically determined by the measurement conditions described in the Examples section below.

[0031] <Melting point> The melting point of this copolymer is 245°C or higher, preferably 246°C or higher, more preferably 248°C or higher, and particularly preferably 249°C or higher, as it offers superior resistance to engine oil. Furthermore, the melting point of this copolymer is preferably 290°C or lower, more preferably 280°C or lower, and particularly preferably 270°C or lower, from the standpoint of excellent moldability of the copolymer. Specific examples of methods for setting the melting point of this copolymer within the above range include lowering the polymerization temperature during the production of the copolymer and adjusting the content of A units and B units in the copolymer. The melting point of this copolymer is the temperature corresponding to the endothermic peak when the copolymer is heated at a rate of 10°C / min in an air atmosphere using a scanning differential thermal analyzer.

[0032] <Meltflow Rate> The melt flow rate (hereinafter also referred to as "MFR") of this copolymer is preferably 15 to 60 g / 10 min, more preferably 25 to 55 g / 10 min, and particularly preferably 30 to 50 g / 10 min. If the MFR of this copolymer is 15 g / 10 min or higher, the copolymer exhibits excellent melt moldability. If the MFR of this copolymer is 60 g / 10 min or lower, the molded article obtained using this copolymer has excellent mechanical strength at high temperatures. On the other hand, in terms of the excellent abrasion resistance of the molded body obtained using the present copolymer, the MFR of the present copolymer is more preferably 25 g / 10 min or less, and even more preferably 20 g / 10 min or less. Therefore, from the viewpoint of achieving both the melt moldability of the present copolymer and the abrasion resistance of the molded body obtained using the present copolymer, the MFR of the present copolymer is preferably 15 to 25 g / min, and more preferably 15 to 20 g / min. As a specific example of the method for making the MFR of the present copolymer fall within the above range, a method for adjusting the molecular weight of the present copolymer can be mentioned. The larger the molecular weight of the present copolymer, the smaller the MFR. The MFR of the present copolymer means the mass of the present copolymer that flows out from an orifice with a diameter of 2 mm and a length of 8 mm in 10 minutes under the conditions of a temperature of 297 °C and a load of 49 N, measured in accordance with ASTM D3159.

[0033] <M value> The M value of the present copolymer is preferably 0.20 or less, more preferably 0.19 or less, and particularly preferably 0.18 or less, from the viewpoints of a higher melting point of the present copolymer and more excellent engine oil resistance. [[ID=ll]] Also, the M value of the present copolymer is preferably 0.10 or more, more preferably 0.11 or more, and particularly preferably 0.12 or more, from the viewpoints of more excellent stress crack resistance and heat resistance. Here, the M value of the present copolymer is a value indicating the degree to which TFE units and E units are alternately arranged in the present copolymer, and is determined by the following calculation method. It can be said that the smaller the M value, the higher the ratio of the alternate bonding of TFE units and E units in the present copolymer. As a specific example of the method for making the M value of the present copolymer fall within the above range, a method for lowering the polymerization temperature during the production of the present copolymer can be mentioned.

[0034] The M value is calculated by the following formula (1) based on the chart obtained by 400 MHz 19 F-NMR measurement using the melt of the present copolymer. M value = C1 / B1 Formula (1) B1: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C1: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm.

[0035] The chemical shifts at B1 and C1 are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0036] B1 represents the sum of the integral values ​​of the CF2 peaks in the TFE-E alternating structure and the integral value of the CH2-side CF2 peaks in the TFE2 chain structure. In other words, B1 is a value that mainly represents the alternating bonding of TFE units and E units, and a large B1 means that the proportion of the copolymer in which TFE units and E units are alternately bonded is high. Here, B1 does not include the integral values ​​of the peaks observed in the chemical shift range of -100 to -115 ppm, which originate from compounds A and B. The reason for this is as follows: In other words, peaks originating from compound A and compound B may be observed in the chemical shift range of -100 to -115 ppm. The units based on compound A (i.e., A units) and the units based on compound B (i.e., B units) are units that do not constitute a portion where TFE units and E units are alternately bonded. Therefore, it is necessary to subtract the integral values ​​of the peaks observed in the chemical shift range of -100 to -115 ppm originating from compound A and compound B from the sum of the integral values ​​of each peak observed in the chemical shift range of -100 to -115 ppm (hereinafter also referred to as "B"). In other words, B1 is the value obtained by subtracting the integral values ​​of the peaks observed in the chemical shift range of -100 to -115 ppm originating from compound A and compound B from B.

[0037] C1 represents the integral value of the peak of the CF2 on the CF2 side in the TFE2 chain structure. In other words, C1 is a value that mainly represents the continuous bonding of TFE units to TFE units, and a large C1 means that the proportion of the copolymer in which TFE units are continuously bonded to TFE units is high. Here, C1 does not include the integral values ​​of the peaks observed in the chemical shift range of -118.5 to -122 ppm, which originate from compounds A and B. The reason for this is as follows: In other words, peaks originating from compound A and compound B may be observed in the chemical shift range of -118.5 to -122 ppm. The units based on compound A (i.e., A units) and the units based on compound B (i.e., B units) are units that do not constitute a portion where TFE units are continuously bonded together. Therefore, it is necessary to subtract the integral values ​​of the peaks observed in the chemical shift range of -118.5 to -122 ppm originating from compound A and compound B from the sum of the integral values ​​of each peak observed in the chemical shift range of -118.5 to -122 ppm (hereinafter also referred to as "C"). In other words, C1 is the value obtained by subtracting the integral values ​​of the peaks observed in the chemical shift range of -118.5 to -122 ppm originating from compound A and compound B from C.

[0038] The integral value of each peak can be obtained by integrating over the valleys within that range. More specifically, it can be obtained by using a chemical shift of -100 to -130 ppm as the baseline and vertically dividing the range of chemical shifts within a predetermined range. Specifically, B1 is obtained by vertically dividing the range of chemical shifts from -100 ppm to -115 ppm toward the baseline. Similarly, C1 is obtained by vertically dividing the range of chemical shifts from -118.5 ppm to -122 ppm toward the baseline.

[0039] The following sections will explain how to calculate the M value for each representative example of compound A and compound B.

[0040] (Method for calculating the M value: When compound A is CH2=CH(CF2)4F) If this copolymer contains units based on CH2=CH(CF2)4F, which is one embodiment of compound A, the M value of this copolymer is obtained by using the molten copolymer at 400 MHz. 19 Based on the chart obtained by F-NMR measurement, it is calculated using the following formula (2-1). M value = {C - (A / 3) × 2} / {B - (A / 3) × 2} Equation (2-1) A: Sum of the integral values ​​of peaks observed in the chemical shift range of -75 to -85 ppm. B: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm

[0041] The chemical shifts in A, B, and C are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0042] Equation (2-1) will be explained in detail with reference to Figure 1. Figure 1 shows a molten copolymer containing E units, TFE units, and units based on CH2=CH(CF2)4F, at 400 MHz. 19 This chart was obtained by F-NMR measurement. Figure 1A area B area and C area These regions are shown to facilitate understanding of the locations of peaks observed in the chemical shift range of -75 to -85 ppm, the chemical shift range of -100 to -115 ppm, and the chemical shift range of -118.5 to -122 ppm, respectively.

[0043] Figure 1A areaIn this, a peak corresponding to CF3 in the unit represented by -CH2-CH(CF2-CF2-CF2-CF3)- is observed. Therefore, A in equation (2-1) represents the integral value of the peak corresponding to CF3.

[0044] Figure 1B area In this, peak a, corresponding to CF2 in the TFE-E alternating structure, and peak c, corresponding to CH2-side CF2 in the TFE2 chain structure, are observed. Furthermore, B area Then, a peak corresponding to one CF2 is detected in the unit based on CH2=CH(CF2)4F, that is, the unit expressed as -CH2-CH(CF2-CF2-CF2-CF3)-. Therefore, B in equation (2-1) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CH2-CH(CF2-CF2-CF2-CF3)- is a unit that does not constitute a part in which TFE units and E units are alternately bonded. Therefore, from B in equation (2-1), B area It is necessary to remove the integral value of the peak corresponding to one of the CF2 units in the unit represented by -CH2-CH(CF2-CF2-CF2-CF3)- detected, but the integral value of that peak cannot be calculated directly. Therefore, A area It is calculated by multiplying the integral value of the peak corresponding to CF3 in the unit -CH2-CH(CF2-CF2-CF2-CF3)- observed by 2 / 3. The reason for multiplying by 2 / 3 is that CF3 has 3 fluorine atoms, while CF2 has 2 fluorine atoms, so the value obtained by multiplying the integral value of the peak corresponding to CF3 by 2 / 3 corresponds to the integral value of the peak corresponding to CF2. Since the integral value of the peak corresponding to CF3 is A, in equation (2-1) we subtract (A / 3) × 2 from B.

[0045] Figure 1 C area In this, peak b corresponding to the CF2 side CF2 in the TFE2 chain structure is observed. Furthermore, C areaThen, one peak of CF2 is detected in the unit based on CH2=CH(CF2)4F, that is, the unit represented as -CH2-CH(CF2-CF2-CF2-CF3)-. Therefore, C in equation (2-1) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CH2-CH(CF2-CF2-CF2-CF3)- is a unit that does not constitute a part in which TFE units are continuously bonded together. Therefore, from C in equation (2-1), C area It is necessary to remove the integral value of the peak corresponding to one of the CF2 units in the unit represented by -CH2-CH(CF2-CF2-CF2-CF3)- detected, but the integral value of that peak cannot be calculated directly. Therefore, A area It is calculated by multiplying the integral value of the peak corresponding to CF3 in the unit -CH2-CH(CF2-CF2-CF2-CF3)- observed by 2 / 3. The reason for multiplying by 2 / 3 is that CF3 has 3 fluorine atoms, while CF2 has 2 fluorine atoms, so the value obtained by multiplying the integral value of the peak corresponding to CF3 by 2 / 3 corresponds to the integral value of the peak corresponding to CF2. Since the integral value of the peak corresponding to CF3 is A, in equation (2-1) we subtract (A / 3) × 2 from C.

[0046] (Method for calculating the M value: When compound A is CH2=CH(CF2)6F) If this copolymer contains units based on CH2=CH(CF2)6F, which is one embodiment of compound A, the M value of this copolymer is obtained by using the molten copolymer at 400 MHz. 19 Based on the chart obtained by F-NMR measurement, it is calculated using the following formula (2-2). M value = {C - (A / 3) × 4} / {B - (A / 3) × 2} Equation (2-2) A: Sum of the integral values ​​of peaks observed in the chemical shift range of -75 to -85 ppm. B: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm

[0047] The chemical shifts in A, B, and C are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0048] Equation (2-2) will be explained in detail with reference to Figure 2. Figure 2 shows a molten copolymer containing E units, TFE units, and units based on CH2=CH(CF2)6F (i.e., units represented as -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)-) at 400 MHz. 19 This chart was obtained by F-NMR measurement.

[0049] Figure 2A area B area and C area The meanings of each are shown in Figure 1, A. area B area and C area It has the same meaning as [the other meaning]. Furthermore, the meaning of the letters attached to the peaks in each region of Figure 2 is the same as the meaning of the letters attached to the peaks in each region of Figure 1.

[0050] Figure 2A area In this system, a peak corresponding to CF3 is observed in the unit represented by -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)-. Therefore, A in equation (2-2) represents the integral value of the peak corresponding to CF3.

[0051] Figure 2B area In this, peak a, corresponding to CF2 in the TFE-E alternating structure, and peak c, corresponding to CH2-side CF2 in the TFE2 chain structure, are observed. Furthermore, B areaThen, a peak corresponding to one CF2 is detected in the unit based on CH2=CH(CF2)6F, that is, the unit represented as -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)-. Therefore, B in equation (2-2) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- is a unit that does not constitute a part in which TFE units and E units are alternately bonded. Therefore, from B in equation (2-2), B area It is necessary to remove the integral value of the peak corresponding to one of the CF2 units in the unit represented by -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- detected, but the integral value of that peak cannot be calculated directly. Therefore, A area It is calculated by multiplying the integral value of the peak corresponding to CF3 in the unit -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- observed by 2 / 3. The reason for multiplying by 2 / 3 is that CF3 has 3 fluorine atoms, while CF2 has 2 fluorine atoms, so the value obtained by multiplying the integral value of the peak corresponding to CF3 by 2 / 3 corresponds to the integral value of CF2. Since the integral value of the peak corresponding to CF3 is A, in equation (2-2) we subtract (A / 3) × 2 from C.

[0052] Figure 2 C area In this, peak b corresponding to the CF2 side CF2 in the TFE2 chain structure is observed. Furthermore, C area Then, two peaks corresponding to CF2 are detected in the unit based on CH2=CH(CF2)6F, that is, the unit expressed as -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)-. Therefore, C in equation (2-2) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- is a unit that does not constitute a part in which TFE units are continuously bonded together. Therefore, from C in equation (2-2), C areaIt is necessary to remove the integral values ​​corresponding to the two CF2 peaks of the unit represented by -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- detected, but the integral values ​​of these peaks cannot be calculated directly. Therefore, A area It is calculated by multiplying the integral value of the peak corresponding to CF3 in the unit -CH2-CH(CF2-CF2-CF2-CF2-CF2-CF3)- observed by 4 / 3. The reason for multiplying by 4 / 3 here is that while CF3 has 3 fluorine atoms, CF2 has 2 fluorine atoms, and there are two such peaks. Therefore, multiplying the integral value of the peak corresponding to CF3 by 4 / 3 corresponds to the integral value of the two peaks corresponding to CF2. Since the integral value of the peak corresponding to CF3 is A, in equation (2-2), (A / 3) × 4 is subtracted from C.

[0053] (Method for calculating the M value: When compound A is CH2=CH(CF2)2F) If this copolymer contains units based on CH2=CH(CF2)2F, which is one embodiment of compound A, the M value of this copolymer is obtained by using the molten copolymer at 400 MHz. 19 Based on the chart obtained by F-NMR measurement, it is calculated using the following formula (2-3). M value = C / {B - (A / 3) × 2} Equation (2-3) A: Sum of the integral values ​​of peaks observed in the chemical shift range of -75 to -85 ppm. B: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm

[0054] The chemical shifts in A, B, and C are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0055] Equation (2-3) will be explained in detail with reference to Figure 3. Figure 3 shows a molten copolymer containing E units, TFE units, and units based on CH2=CH(CF2)2F (i.e., units represented as -CH2-CH(CF2-CF3)-) at 400 MHz. 19 This chart was obtained by F-NMR measurement.

[0056] Figure 3A area B area and C area The meanings of each are shown in Figure 1, A. area B area and C area It has the same meaning as [the other meaning]. Furthermore, the meaning of the letters attached to the peaks in each region of Figure 3 is the same as the meaning of the letters attached to the peaks in each region of Figure 1.

[0057] Figure 3A area In this system, a peak corresponding to CF3 is observed in the unit represented by -CH2-CH(CF2-CF3)-. Therefore, A in equation (2-3) represents the integral value of the peak corresponding to CF3.

[0058] Figure 3B area In this, peak a, corresponding to CF2 in the TFE-E alternating structure, and peak c, corresponding to CH2-side CF2 in the TFE2 chain structure, are observed. Furthermore, B area Then, a peak corresponding to one CF2 is detected in the unit based on CH2=CH(CF2)2F, that is, the unit expressed as -CH2-CH(CF2-CF3)-. Therefore, B in equation (2-3) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CH2-CH(CF2-CF3)- is a unit that does not constitute a part in which TFE units and E units are alternately bonded. Therefore, from B in equation (2-3), B area It is necessary to remove the integral value of the peak corresponding to one of the CF2 units in the unit represented by -CH2-CH(CF2-CF3)- detected, but the integral value of this peak cannot be calculated directly. Therefore, A areaIt is calculated by multiplying the integral value of the peak corresponding to CF3 in the unit -CH2-CH(CF2-CF3)- observed by 2 / 3. The reason for multiplying by 2 / 3 is that CF3 has 3 fluorine atoms while CF2 has 2 fluorine atoms, so the integral value of CF3 multiplied by 2 / 3 corresponds to the integral value of the peak corresponding to CF2. Since the integral value of the peak corresponding to CF3 is A, in equation (2-3) we subtract (A / 3) × 2 from B.

[0059] Figure 3 C area In this equation, peak b is observed, corresponding to the CF2 side CF2 in the TFE2 chain structure. Therefore, C in equation (2-3) represents the integral value of peak b.

[0060] (Method for calculating the M value: When compound A is CH2=CF(CF2)3H) If this copolymer contains units based on CH2=CF(CF2)3H, which is one embodiment of compound A, the M value of this copolymer is obtained by using the molten copolymer at 400 MHz. 19 Based on the chart obtained by F-NMR measurement, it is calculated using the following formula (3-1). M value = C / B Equation (3-1) B: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm

[0061] The chemical shifts at B and C are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0062] Equation (3-1) will be explained in detail with reference to Figure 4. Figure 4 shows a molten copolymer containing E units, TFE units, and units based on CH2=CF(CF2)3H (i.e., units represented as -CH2-CF(CF2-CF2-CF2H)-) at 400 MHz. 19 This chart was obtained by F-NMR measurement.

[0063] Figure 4B area and C area The meanings of each are shown in Figure 1, B. area and C area It has the same meaning as [the other meaning]. Furthermore, the meaning of the letters attached to the peaks in each region of Figure 4 is the same as the meaning of the letters attached to the peaks in each region of Figure 1.

[0064] Figure 4B area In this, peak a, corresponding to CF2 in the TFE-E alternating structure, and peak c, corresponding to CH2-side CF2 in the TFE2 chain structure, are observed. Therefore, B in equation (3-1) represents the sum of the integral values ​​of peak a and peak c.

[0065] Figure 4C area In this equation, peak b is observed, corresponding to the CF2 side CF2 in the TFE2 chain structure. Therefore, C in equation (3-1) represents the integral value of peak b.

[0066] (Method for calculating the M value: In the case of compound B) If this copolymer contains units based on compound B (i.e., CF2=CF-O-C3F7), the M value of this copolymer is obtained by using the molten copolymer at 400 MHz. 19 Based on the chart obtained by F-NMR measurement, it is calculated using the following formula (4-1). M value = C / {B - (A / 5) × 2} Equation (4-1) A: Sum of the integral values ​​of peaks observed in the chemical shift range of -75 to -85 ppm. B: Sum of the integral values ​​of peaks observed in the chemical shift range of -100 to -115 ppm. C: Sum of integral values ​​of peaks observed in the chemical shift range of -118.5 to -122 ppm

[0067] The chemical shifts in A, B, and C are observed when the chemical shift of the CF2 peak at the location where two consecutive TFE units of this copolymer directly bond to one TFE unit (i.e., the CF2-side CF2 in the TFE2 chain structure) is set to -120 ppm.

[0068] Equation (4-1) will be explained in detail with reference to Figure 5. Figure 5 shows a molten copolymer containing E units, TFE units, and units based on CF2=CF-O-C3F7, at 400 MHz. 19 This chart was obtained by F-NMR measurement.

[0069] Figure 5A area B area and C area The meanings of each are shown in Figure 1, A. area B area and C area It has the same meaning as [the other meaning]. Furthermore, the meaning of the letters attached to the peaks in each region of Figure 5 is the same as the meaning of the letters attached to the peaks in each region of Figure 1.

[0070] Figure 5A area In this system, a peak corresponding to CF3 in the unit -CF2-CF(OCF2CF2CF3)- and a peak e corresponding to one CF2 in the unit -CF2-CF(OCF2CF2CF3)- are observed. Therefore, A in equation (4-1) represents the sum of the integral values ​​of these peaks.

[0071] Figure 5B area In this, peak a, corresponding to CF2 in the TFE-E alternating structure, and peak c, corresponding to CH2-side CF2 in the TFE2 chain structure, are observed. Furthermore, B areaThen, a peak corresponding to one CF2 is detected in the unit based on CF2 = CF(OCF2)3F, that is, the unit expressed as -CF2-CF(OCF2CF2CF3)-. Therefore, B in equation (4-1) represents the sum of the integral values ​​of these peaks. Here, the unit represented by -CF2-CF(OCF2CF2CF3)- is a unit that does not constitute a part in which TFE units and E units are alternately combined. Therefore, from B in equation (4-1), B area It is necessary to remove the integral value of the peak corresponding to one of the CF2 units in the unit represented by -CF2-CF(OCF2CF2CF3)- detected, but the integral value of that peak cannot be calculated directly. Therefore, A area The integral of CF2 is calculated by multiplying the sum of the integral values ​​of the peaks corresponding to CF3 and the peaks corresponding to one CF2 in the unit -CF2-CF(OCF2CF2CF3)- observed by 2 / 5. The reason for multiplying by 2 / 5 is that CF3 has 3 fluorine atoms and one CF2 has 2 fluorine atoms, totaling 5, while CF2 has 2 fluorine atoms. Therefore, the sum of the integral values ​​of the peaks corresponding to CF3 and one CF2 multiplied by 2 / 5 corresponds to the integral value of CF2. Since the integral value of CF3 is A, in equation (4-1), (A / 5) × 2 is subtracted from B.

[0072] Figure 5 C area In this equation, peak b is observed, corresponding to the CF2 side CF2 in the TFE2 chain structure. Therefore, C in equation (4-1) represents the integral value of peak b.

[0073] <Manufacturing method> This copolymer can be produced using the above-mentioned monomers (ethylene, tetrafluoroethylene, and compound A or compound B) by known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, and among these, production by solution polymerization is preferred. In the production of this copolymer, in addition to the monomers mentioned above, polymerization initiators, polymerization media, chain transfer agents, etc., can be used.

[0074] The polymerization initiator is preferably a radical polymerization initiator with a half-life of 10 hours and a temperature range of 0 to 100°C, and particularly preferably a radical polymerization initiator with a temperature range of 20 to 90°C. Specific examples of polymerization initiators include the various polymerization initiators exemplified in International Publication No. 2013 / 015202. Polymerization initiators may be used individually or in combination of two or more. The amount of polymerization initiator used is preferably 0.01 to 0.9 parts by mass, and particularly preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of monomer used.

[0075] Perfluorocarbons, hydrofluorocarbons, hydrofluoroethers, etc., can be used as polymerization media. Specific examples of polymerization media are those exemplified in International Publication No. 2013 / 015202. Two or more polymerization media may be used in combination. The amount of polymerization medium used is preferably 5 times or more by mass ratio of the amount of monomer used, more preferably 7 times or more. Furthermore, it is preferably 20 times or less, and more preferably 17 times or less.

[0076] As chain transfer agents, alcohols such as methanol, ethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoropropanol, 1,1,1,3,3,3-hexafluoroisopropanol, and 2,2,3,3,3-pentafluoropropanol are preferred because they have a large chain transfer constant and require only small amounts of additive; hydrocarbons such as n-pentane, n-hexane, and cyclohexane; hydrofluorocarbons such as CF2H2; ketones such as acetone; mercaptans such as methyl mercaptan; esters such as methyl acetate and ethyl acetate; and ethers such as diethyl ether and methyl ethyl ether are preferred because they have a large chain transfer constant and require only small amounts of additive. Among these, alcohols, hydrocarbons, and hydrofluorocarbons are preferred due to their higher chain transfer constant and greater stability of the end groups of the copolymer, with alcohols and hydrocarbons being more preferred, and alcohols being particularly preferred. Among alcohols, methanol and ethanol are particularly preferred. Of these, methanol is particularly preferred due to its reactivity and availability. Two or more chain transfer agents may be used. The amount of chain transfer agent used is preferably 0.001 times or more by mass ratio of the amount of monomer used, more preferably 0.005 times or more. Furthermore, it is preferably 5 times or less, and more preferably 4 times or less.

[0077] The polymerization temperature is preferably 15 to 60°C, more preferably 20 to 58°C, and particularly preferably 25 to 55°C. Polymerizability is excellent when the polymerization temperature is 25°C or higher. If the polymerization temperature is 60°C or lower, the melting point of the copolymer can be improved, and a copolymer with an M value within the above range can be easily obtained. The polymerization pressure is preferably 0.5 to 3.0 MPa, and particularly preferably 0.9 to 2.5 MPa. The polymerization time is preferably 1 to 12 hours.

[0078] [Composition] The composition of the present invention (hereinafter also referred to as "this composition") comprises the copolymer described above and an additive. Because this composition contains the copolymer, a molded article with excellent engine oil resistance can be obtained by using this composition. Furthermore, because the copolymer has a high melting point, a molded article with excellent heat resistance can be obtained by using this composition. Preferred additives include heat stabilizers and antioxidants. Furthermore, this composition may contain two or more additives. The content of this copolymer is preferably 50% by mass or more and less than 100% by mass, more preferably 70% by mass or more and less than 100% by mass, and particularly preferably 90% by mass or more and less than 100% by mass, based on the total mass of the composition.

[0079] <Heat stabilizer> This composition preferably contains a heat stabilizer because the molded articles obtained using this composition exhibit excellent strength at high temperatures. Copper compounds are preferred as the heat stabilizer. Specific examples of copper compounds used as heat stabilizers include cuprous oxide (copper(I) oxide), cupric oxide (copper(II) oxide), cuprous iodide, and cupric iodide. Of these, cupric oxide is particularly preferred due to its excellent stability in humid air. If the composition contains a heat stabilizer, the amount of heat stabilizer is preferably 0.00015 to 0.02 parts by mass, more preferably 0.0002 to 0.005 parts by mass, and particularly preferably 0.0003 to 0.002 parts by mass, per 100 parts by mass of the copolymer in the composition. If the amount of heat stabilizer is within the above range, the molded article obtained using the composition will have good strength and suppress discoloration even when used at high temperatures.

[0080] <Antioxidant> This composition preferably contains an antioxidant, as it can improve the heat resistance of the molded article obtained using this composition. Specific examples of antioxidants include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, hindered phenolic antioxidants, amine-based antioxidants, and polymeric acrylate-type radical scavengers. Phenolic antioxidants are preferred because they can further improve the heat resistance of the molded article. If the composition contains an antioxidant, the antioxidant content is preferably 0.00002 to 0.02 parts by mass, more preferably 0.00005 to 0.0015 parts by mass, and particularly preferably 0.0001 to 0.001 parts by mass, per 100 parts by mass of the copolymer in the composition. If the antioxidant content is within the above range, the heat resistance of the molded article can be further improved.

[0081] <Other additives> This composition may contain additives other than those listed above. Specific examples of such other additives include resins other than this copolymer, colorants, UV absorbers, fillers, crosslinking agents, crosslinking aids, and organic peroxides. If this composition contains other additives, the content of the other additives is preferably 0.0000001 to 70 parts by mass, more preferably 0.0000005 to 60 parts by mass, and particularly preferably 0.000001 to 50 parts by mass, per 100 parts by mass of the copolymer in this composition.

[0082] One method for producing this composition is to melt-knead the copolymer and the components used as needed using a known method.

[0083] [Molded body] The molded article of the present invention is obtained by molding the copolymer described above or the composition described above. Because the molded article contains the copolymer, it has excellent resistance to engine oil. Furthermore, because the copolymer has a high melting point, the molded article also has excellent heat resistance. Specific examples of molding methods include injection molding, extrusion molding, blow molding, press molding, rotational molding, and electrostatic coating. This molded product is suitably used as a wire insulation material for various types of equipment. Specifically, it can be used as a wire insulation material for electrical equipment such as robots, electric motors, generators, and transformers; for household electrical appliances; for communication transmission equipment such as telephones and wireless devices; for electronic equipment such as computers, data communication equipment, and terminal equipment; for railway vehicles; for automobiles; for aircraft; for ships; and for system components such as buildings, factory trunk lines, power plants, petrochemical plants, and steel plants. In particular, this molded product is especially suitable as a wire insulation material for automobiles and other devices that use engine oil, due to its excellent resistance to engine oil. Furthermore, this molded product can be used not only as a wire insulation material, but also for tubes, sheets, films, filaments, pump casings, fittings, packings, linings, coatings, and more.

[0084] [Insulated wire] The insulated electric wire of the present invention (hereinafter also referred to as "this insulated electric wire") comprises a conductor and a coating layer disposed on the surface of the conductor and formed from the copolymer or composition described above. Because this coated wire contains this copolymer, it has excellent resistance to engine oil. Furthermore, because this copolymer has a high melting point, this coated wire also has excellent heat resistance.

[0085] The materials used to make up the conductor include copper, aluminum, and alloys thereof, with copper being preferred. The conductor may be plated with tin, silver, or the like. The conductor is preferably a core wire.

[0086] The cross-sectional diameter of the conductor is preferably 200 μm to 18.0 mm. The thickness of the coating layer is preferably 100 μm to 2.0 mm. The cross-sectional diameter of the insulated wire is preferably between 400 μm and 22.0 mm.

[0087] A specific example of a method for manufacturing this coated wire is a method in which the molten copolymer or composition is attached to the surface of a conductor to form a coating layer on the surface of the conductor, which is made from the copolymer or composition.

[0088] Specific examples of the applications of insulated wires are as described in the section on this molded product above, so we will omit further explanation here. [Examples]

[0089] The present invention will be described in detail below with reference to examples. Examples 1 to 3 and Example 6 are examples, and Examples 4 to 5 and Examples 7 and 8 are comparative examples. However, the present invention is not limited to these examples.

[0090] [Percentage of each unit] The content (mol%) of each unit in the copolymer is: 19 The calculation was performed by 1F-NMR measurement. However, the content of E units in the copolymer is as follows: 1 H and 13 The calculation was performed using 1C-NMR measurement.

[0091] [Crystal lamellar thickness] The crystalline lamellar thickness (nm) of the copolymer was calculated from the profile obtained by small-angle X-ray scattering (SAXS). Specifically, the measurement by the SAXS method was carried out on the beamline BL8S3 of the Aichi Synchrotron Light Center. Using an X-ray wavelength of 1.5 Å, a camera length of 1131.07 mm, and an exposure time of 60 seconds as the measurement conditions, an R-AXIS was used as the detector. The data obtained by the two-dimensional detector was made one-dimensional by circular averaging. The obtained one-dimensional SAXS profile was subjected to air cell scattering correction to obtain the SAXS profile of the copolymer. 0.15 nm -1 <q (scattering vector) < 1.5 nm -1 The SAXS profile of the copolymer in the region of was converted into a one-dimensional electron density correlation function, and the crystal lamellar thickness was determined from the one-dimensional electron density correlation function profile. The conversion to the one-dimensional electron density correlation function was in accordance with the method described in Fujimori, A. et al. J. Polym. Sci. Part B: Polym. Phys. 2015, 53, 1674-1690.

[0092] [Melting point] The melting point (°C) of the copolymer was determined from the endothermic peak when the copolymer was heated by using a scanning differential thermal analyzer (trade name "DSC7020", manufactured by Hitachi High-Tech Sciences Corporation) and raising the temperature to 300 °C at 10 °C / min in an air atmosphere.

[0093] [M value] Using the melt of each copolymer, based on the chart obtained by 400 MHz 19 F-NMR measurement, the M value of each copolymer was calculated by the above formula (2-1). 19 The F-NMR measurement was carried out under the following measurement conditions. Measuring device: "AVANCE III 400" manufactured by Bruker

[0094] [MFR (melt flow rate)] Using a melt indexer (manufactured by Technoseven), in accordance with ASTM D3159, under the conditions of a temperature of 297 °C and a load of 49 N, the mass (g) of the copolymer flowing out from an orifice with a diameter of 2 mm and a length of 8 mm in 10 minutes was measured and taken as MFR (g / 10 min).

[0095] [Evaluation Test] A wire insulated manufacturing apparatus was prepared, comprising a feeder for feeding out core wires, an extruder (IKG Corporation, MS30-25) equipped with a screw (IKG Corporation, full flight, L / D=24, diameter 30 mm) for melt-mixing a composition containing a copolymer, a take-up machine (Sei Seisakusho Co., Ltd.) for taking up insulated wires, and a winding machine (Sei Seisakusho Co., Ltd.) for winding up insulated wires. The composition supplied to the extruder was melted and kneaded at a temperature of 280-320°C. The molten composition was extruded from the extruder nozzle and adhered to the surface of a core wire (product name "TA Copper Core 37 / 0.26", manufactured by Yasuda Kogyo Co., Ltd.) fed from a feeder. The composition adhering to the surface of the core wire was cooled and solidified to obtain a coated wire (cross-sectional diameter of coated wire: 2.8 mm ± 0.02 mm) with a coating layer formed on the surface of the core wire. The wire retrieval speed was adjusted to 10 m / min. The following evaluation tests were conducted using the obtained insulated wires.

[0096] <Engine oil resistance> After cutting the insulated wire to a length of 600 mm, the insulation layer was stripped from both ends of the wire to a length of 25 mm. The core wires of the stripped sections were then wrapped together to obtain a teardrop-shaped insulated wire (evaluation sample). Subsequently, the evaluation samples were immersed in oil (IRM902) manufactured by Nippon Sun Oil Co., Ltd. for 10 seconds, then removed, the oil was drained, and the samples were suspended in an oven heated to 200°C. After 240 hours, the evaluation samples were removed and visually inspected for cracks in the coating layer. Samples without cracks were again immersed in oil (IRM902) for 10 seconds, removed, the oil was drained, and the samples were suspended in an oven heated to 200°C. This procedure was repeated two more times, and after a total of 1000 hours had elapsed since the initial placement of the evaluation samples in the oven, the evaluation samples were removed from the oven. A load of 5 kgf was applied to these samples, and they were wrapped around a 30 mm diameter mandrel at least five times. The presence or absence of cracks in the coating layer of the evaluation samples was then visually determined.

[0097] <Abrasion Resistance> The insulated wires, obtained in the same manner as the engine oil resistance evaluation, were cut to a length of 2m, and then subjected to a scrape abrasion test using a Yasuda Seiki Co., Ltd. "Magnet Wire Abrasion Tester (Reciprocating Type)" in accordance with the test method compliant with ISO 6722-1. Specifically, the test was conducted under the following conditions: needle diameter: 0.45±0.01mm, needle material: SUS316 (compliant with JIS K-G7602), wear distance: 1.55±1mm, wear rate: 55±5 times / min, load: 7N, and test environment: 23±1℃. Abrasion resistance is expressed by the number of times the needle reciprocates before the core wire is exposed from the coating layer. The higher the abrasion resistance (number of needle reciprocations), the better the abrasion resistance of the coating layer.

[0098] [Example 1] <Production of Copolymer 1> After purging a 21.3L stainless steel polymerization tank with nitrogen, the pressure was reduced to -0.1 MPaG, and C6H (21050g), CH3OH (206.8g), CH2=CH(CF2)4F (290g), tetrafluoroethylene (TFE) (3393g), and ethylene (E) (155g) were added. Next, the solution in the polymerization tank was heated to 50°C (polymerization temperature) while stirring, and a solution of IPP dissolved in C6H (2% by mass, 200 mL) was poured into the polymerization tank. When the pressure in the polymerization tank began to drop, a mixed monomer of TFE / E = 54 / 46 (molar ratio) was added to maintain the internal pressure of the polymerization tank at 1.5 MPaG, and polymerization proceeded. Every time 50 g of the mixed monomer was added, a CH2=CH(CF2)4F solution (76% by mass, 5 mL) was added to the polymerization tank. When the continuous addition of mixed monomer reached 1718 g, the polymerization tank was cooled to room temperature, and the gas in the polymerization tank was released and recovered. The polymerization time was 220 minutes. The solvent was removed, and the copolymer 1 powder was obtained by drying at 150°C. Note that C6H stands for 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane, and IPP stands for diisopropyl peroxydicarbonate.

[0099] <Preparation of Composition 1> Copolymer 1 (100 parts by mass), copper(II) oxide (0.00065 parts by mass), and Smirizer GP (0.02 parts by mass) were mixed and melt-extruded in a 30 mm diameter extruder (IKG, MS30-25) under the conditions of cylinder temperature 260-300°C, die temperature 300°C, and screw rotation speed 60 rpm to obtain a strand-shaped molded product, which was then cut with a pelletizer to obtain pellet-shaped composition 1.

[0100] [Example 2] Copolymer 2 of Example 2 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 1. CH2=CH(CF2)6F was used as compound A. A pelletized composition 2 of Example 2 was obtained in the same manner as in Example 1, except that the obtained copolymer was used.

[0101] [Example 3] Copolymer 3 of Example 3 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 1. CH2=CH(CF2)2F was used as compound A. Using the obtained copolymer, and without using Smirizer GP, the pelletized composition 3 of Example 3 was obtained in the same manner as in Example 1.

[0102] [Example 4] Copolymer 4 of Example 4 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 1, and the polymerization temperature was changed from 50°C to 66°C. CH2=CF(CF2)3H was used as compound A. A pelletized composition 4 of Example 4 was obtained in the same manner as in Example 1, except that copolymer 4 was used.

[0103] [Example 5] Copolymer 5 of Example 5 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 1. Compound B used was CF2=CF(OCF2)3F. A pelletized composition 5 of Example 5 was obtained in the same manner as in Example 1, except that copolymer 5 was used.

[0104] Table 1 shows the evaluation results using the compositions of Examples 1 to 5. [Table 1]

[0105] As shown in Table 1, it was confirmed that coated wires with excellent engine oil resistance can be obtained by using copolymers containing E units, TFE units, and A units, with a crystal lamellar thickness of 4.0 nm or less and a melting point of 245°C or higher (Examples 1-3).

[0106] [Example 6] Copolymer 6 of Example 6 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 2. Compound B used was CF2=CF(OCF2)3F. A pelletized composition 6 of Example 6 was obtained in the same manner as in Example 1, except that the obtained copolymer was used.

[0107] [Example 7] Copolymer 7 of Example 7 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 2. As in Example 1, CH2=CH(CF2)4F was used as compound A. A pelletized composition 7 of Example 7 was obtained in the same manner as in Example 1, except that the obtained copolymer was used.

[0108] [Example 8] Copolymer 8 of Example 8 was obtained in the same manner as in Example 1, except that the amount of each component added was adjusted so that the composition ratio of the copolymer was the value shown in Table 2. As in Example 1, CH2=CH(CF2)4F was used as compound A. A pelletized composition 8 of Example 8 was obtained in the same manner as in Example 1, except that the obtained copolymer was used.

[0109] Table 2 shows the evaluation results using the compositions of Examples 6 to 8. [Table 2]

[0110] Furthermore, the entire contents of the specification, claims, abstract, and drawings of Japanese Patent Application No. 2021-020979, filed on February 12, 2021, are incorporated herein by reference as disclosure of the specification of the present invention.

Claims

1. A copolymer comprising units based on ethylene, units based on tetrafluoroethylene, and units based on a compound represented by formula (A), The content of the unit based on the compound represented by formula (A) is 2.8 to 5 mol%, The M value of the copolymer, calculated by the following method, is 0.20 or less. According to ASTM D3159, the melt flow rate of the copolymer, measured under conditions of a temperature of 297°C and a load of 49N, is 15 to 25 g / 10 min. A copolymer characterized by having a crystal lamellar thickness of 4.0 nm or less, as determined by small-angle X-ray scattering, and a melting point of 245°C or higher. CH ２ =CX(CF ２ ) ｎ Y formula (A) In equation (A), X and Y are independently either a hydrogen atom or a fluorine atom, and n is an integer between 2 and 6. Calculation method: The M value is calculated using the following formula (1) based on a chart obtained by 400 MHz 19F-NMR measurement using the molten copolymer. M value = C1 / B1 Equation (1) B1: Integral value of peaks observed in the chemical shift range of -100 to -115 ppm C1: Integral value of peaks observed in the chemical shift range of -118.5 to -122 ppm. The chemical shifts in B1 and C1 are observed when the chemical shift of the CF2 peak at the location where two consecutive tetrafluoroethylene-based units of the copolymer directly bond with one tetrafluoroethylene-based unit and the other tetrafluoroethylene-based unit is set to -120 ppm. However, B1 does not include the integral value of the peak observed in the chemical shift range of -100 to -115 ppm originating from the compound represented by formula (A). Also, C1 does not include the integral value of the peak observed in the chemical shift range of -118.5 to -122 ppm originating from the compound represented by formula (A).

2. The copolymer according to claim 1, wherein the content of the tetrafluoroethylene-based units is 40 to 65 mol% of the total units contained in the copolymer.

3. The copolymer according to claim 1 or 2, wherein the content of the ethylene-based units is 35 to 60 mol% of the total units contained in the copolymer.

4. A composition comprising the copolymer and additive described in any one of claims 1 to 3.

5. The composition according to claim 4, comprising a heat stabilizer as the aforementioned additive.

6. The composition according to claim 5, wherein the heat stabilizer is a copper compound.

7. The composition according to any one of claims 4 to 6, comprising an antioxidant as the aforementioned additive.

8. A molded article characterized by being obtained by molding a copolymer according to any one of claims 1 to 3, or a composition according to any one of claims 4 to 7.

9. A coated electric wire characterized by comprising a conductor and a coating layer disposed on the surface of the conductor and formed from a copolymer according to any one of claims 1 to 3, or a composition according to any one of claims 4 to 7.

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