Copolymer, composition, and molded body

Abstract

Provided are: a copolymer comprising a unit A based on tetrafluoroethylene and a unit B based on a compound represented by formula (1) CF2=CF-CF2-O-Rf1, wherein the content of the unit B is more than 2.0 mol% and at most 6.0 mol% with respect to all units contained in the copolymer, the total content of the unit A and the unit B is at least 90.0 mol% with respect to all units contained in the copolymer, and the total number of functional groups per 106 main-chain carbon atoms in the copolymer is less than 150; a composition containing said copolymer; and a molded body of said composition.

Description

Copolymer, composition, and molded article

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

[0002] Tetrafluoroethylene copolymers containing units based on tetrafluoroethylene are used in various industrial fields due to their excellent heat resistance, chemical resistance, flame retardancy, weather resistance, etc. Hereinafter, tetrafluoroethylene will be referred to as "TFE," and units based on TFE will be referred to as "TFE units." As TFE copolymers, copolymers consisting of TFE units and units based on perfluoroalkyl vinyl ethers (hereinafter also referred to as "PAVE units") are known. Furthermore, Patent Document 1 discloses copolymers containing TFE units and units based on perfluoroalkyl allyl ethers, and optionally further containing units based on perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and combinations thereof.

[0003] Special Publication No. 2021-514015

[0004] For example, when a copolymer is used as a material for a component through which a fluid flows while contacting the surface at high temperatures, such as a tube used in a semiconductor manufacturing device, the copolymer is required to have excellent heat resistance and to provide a molded article having excellent surface smoothness. An object of one embodiment of the present invention is to provide a copolymer having excellent heat resistance and to provide a molded article having excellent surface smoothness, a composition containing the copolymer, and a molded article of the composition.

[0005] The present disclosure includes the following aspects: [1] A copolymer containing units A based on tetrafluoroethylene and units B based on a compound represented by the following formula (1), wherein the content of the units B is more than 2.0 mol % and not more than 6.0 mol % based on all units contained in the copolymer, the total content of the units A and the units B is 90.0 mol % or more based on all units contained in the copolymer, and the copolymer has a main chain carbon number of 10 ６ A copolymer having a total number of functional groups per CF unit of less than 150. ２ =CF-CF ２ -O-Rf １...(1) In formula (1), Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom between carbon atoms. [2] The copolymer according to [1], wherein the melt flow rate of the copolymer measured at 372°C in accordance with ASTM D1238 is 1 to 200 g / 10 min. [3] The copolymer according to [1] or [2], wherein the copolymer is substantially free of units C based on a compound represented by the following formula (3): CF ２ ═CF—O—Rf ３ ...(3) In formula (3), Rf ３ is a perfluoroalkyl group having 1 to 10 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom between carbon atoms. [4] The copolymer according to [1] or [2], wherein the copolymer contains a unit C based on a compound represented by the following formula (3), and the content of the unit C is 6.0 mol % or less based on all units contained in the copolymer. CF ２ ═CF—O—Rf ３ ...(3) In formula (3), Rf ３ is a perfluoroalkyl group having 1 to 10 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom between carbon atoms. [5] A composition comprising the copolymer according to any one of [1] to [4]. [6] The amount of eluted fluoride ions measured in accordance with SEMI F57-0314 is 200 μg / m ２ [7] The composition according to [5] or [6], wherein the total content of the compound represented by the following formula (2) is less than 100 ppb by mass with respect to the entire composition: CF ３ -(CF ２ ) ｎ —COOH … (2) In formula (2), n is an integer of 5 to 12. [8] A molded body of the composition according to [5]. [9] A molded body of the composition according to [6].

[10] A molded body of the composition according to [7].

[0006] According to one embodiment of the present invention, there are provided a copolymer having excellent heat resistance and excellent surface smoothness of the molded article obtained, a composition containing the copolymer, and a molded article of the composition.

[0007] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0008] [Copolymer] A copolymer according to one embodiment of the present disclosure (hereinafter also referred to as "the copolymer") comprises units A which are TFE units and units B based on a compound represented by the following formula (1), the content of units B being more than 2.0 mol % and not more than 6.0 mol % based on all units contained in the copolymer, the total content of units A and units B being 90.0 mol % or more based on all units contained in the copolymer, and the copolymer has a main chain carbon number of 10 or more. ６ The total number of functional groups per CF is less than 150. ２ =CF-CF ２ -O-Rf １ ...(1) In formula (1), Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom between the carbon atoms. Hereinafter, the content relative to the total units contained in the copolymer will be simply referred to as "content." The compound represented by formula (1) will be referred to as "compound (1)," and the copolymer having 10 main chain carbon atoms will be referred to as "compound (2)." ６The total number of functional groups per molecule is also called the "total number of functional groups."

[0009] As mentioned above, for example, when copolymer is used as the material of the member that fluid flows while contacting with the surface under high temperature, said copolymer is required to be excellent in heat resistance and the surface smoothness of the molding that can be obtained.On the other hand, it has been found that the copolymer that is a kind of TFE-based copolymer that is generally used in the past, and that is made up of TFE unit and PAVE unit, has room for improvement in heat resistance and the surface smoothness of the molding that can be obtained.

[0010] The copolymer contains 90.0 mol % or more of units A and units B in total, and contains more than 2.0 mol % to 6.0 mol % of units B, and has a total number of functional groups of less than 150. This results in excellent heat resistance and excellent surface smoothness of the resulting molded article. The reason for this is unclear, but is presumed to be as follows.

[0011] It is believed that the radicals generated during the polymerization process of compound (1) are more stable than those of perfluoroalkyl vinyl ethers, and that they are less likely to form low-molecular-weight components such as oligomers. When the copolymer contains a large amount of low-molecular-weight components, not only does the heat resistance decrease, but the low-molecular-weight components may seep out onto the surface of the molded body during the manufacturing process, which may also reduce the surface smoothness of the molded body. Since this copolymer contains fewer low-molecular-weight components than a copolymer consisting of TFE units and PAVE units, it is believed that it has excellent heat resistance and that the decrease in surface smoothness caused by the seepage of low-molecular-weight components is suppressed. In addition, it is believed that this copolymer has fewer low-molecular-weight components, is superior in heat resistance, and the surface smoothness of the resulting molded body is superior compared to when the content of unit B exceeds the above upper limit. Furthermore, it is believed that this copolymer is less likely to produce particulate matter due to the copolymer's excessively high crystallinity than when the content of unit B is below the above lower limit, and that a molded body with reduced surface smoothness caused by particulate matter can be obtained. Furthermore, since the total number of functional groups of the present copolymer is within the above range, it is presumed that thermal decomposition of the copolymer originating from the functional groups is suppressed compared to when the total number of functional groups exceeds the above upper limit, resulting in excellent heat resistance.

[0012] <Units Contained in Copolymer> The present copolymer contains units A, which are TFE units, and units B, which are based on compound (1). ２ =CF-CF ２ -O-Rf １ ...(1) In formula (1), Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an etheric oxygen atom between carbon atoms.

[0013] Rf １ The number of carbon atoms in Rf is preferably 2 to 8, and more preferably 3 to 8. １ Rf may be linear, branched, or may contain a ring structure. １ Examples of the group include -(CF ２ ) ｍ CF ３ , and −(CF ２ ) ｒ１ -O-(CF ２ ) ｒ２ CF ３ From the viewpoint of improving the crystallinity of the copolymer, -(CF ２ ) ｍ CF ３ Preferably, m is an integer of 0 to 9. r1 is an integer of 1 to 9, r2 is an integer of 0 to 8, and r1+r2 is an integer of 1 to 9.

[0014] Among these, m is preferably an integer of 1 to 7, and more preferably an integer of 1 to 5. r1 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4. r2 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.

[0015] In particular, compound (1) is CF ２ =CF-CF ２ -OCF ２ CF ２ CF ３ is preferred.

[0016] The content of units B is greater than 2.0 mol% and less than 6.0 mol%, based on all units contained in the copolymer. From the viewpoints of heat resistance and the surface smoothness of the resulting molded article, it is preferably 2.2 to 5.5 mol%, more preferably 2.4 to 5.0 mol%, and even more preferably 2.4 to 3.5 mol%. From the viewpoint of mechanical properties, the content of units B is preferably greater than 2.0 mol% and less than 3.0 mol%, based on all units contained in the copolymer. Furthermore, from the viewpoints of heat resistance and the surface smoothness of the resulting molded article, the content of units B relative to the total of units A and units B is preferably greater than 2.0 mol% and less than 6.0 mol%, more preferably 2.2 to 5.5 mol%, even more preferably 2.4 to 5.0 mol%, and particularly preferably 2.4 to 3.5 mol%. From the viewpoint of mechanical properties, it is preferable that the content of units B relative to the total of units A and units B is greater than 2.0 mol% and less than 3.0 mol%.

[0017] The content of unit A is preferably 94.0 mol% or more and less than 98.0 mol% relative to the total units contained in the copolymer, and from the viewpoint of heat resistance and the surface smoothness of the obtained molded article, it is more preferably 95.0 mol% or more and less than 98.0 mol%, and even more preferably 96.0 mol% or more and less than 98.0 mol%. In addition, the content of unit A relative to the total of unit A and unit B is preferably 94.0 mol% or more and less than 98.0 mol%, more preferably 95.0 mol% or more and less than 98.0 mol%, more preferably 96.0 mol% or more and less than 98.0 mol%, and even more preferably 96.5 mol% or more and less than 98.0 mol%. The content of each unit contained in the copolymer is determined by the solid １９ Calculated by F-NMR analysis.

[0018] From the viewpoint of surface smoothness, it is preferable that the present copolymer is substantially free of unit C based on the compound represented by the following formula (3). Hereinafter, the compound represented by formula (3) will also be referred to as "compound (3)." "Substantially free of unit C" means that the content of units based on unit C is 0.01 mol% or less, more preferably 0.00 mol%, based on the total units contained in the copolymer. From the viewpoint of mechanical properties, the present copolymer may further contain unit C. Since the present copolymer contains unit B at a predetermined content, even if it contains unit C, it has excellent heat resistance and the surface smoothness of the resulting molded article is likely to be relatively excellent. CF ２ ═CF—O—Rf ３ ...(3) In formula (3), Rf ３ is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an etheric oxygen atom between carbon atoms.

[0019] Rf ３ The number of carbon atoms in Rf is preferably 2 to 8, and more preferably 3 to 8. ３ Rf may be linear, branched, or may contain a ring structure. ３ Examples of the group include -(CF ２ ) ｍ CF ３ , and −(CF ２ ) ｒ１ -O-(CF ２ ) ｒ２ CF ３ From the viewpoint of improving the crystallinity of the copolymer, -(CF ２ ) ｍ CF ３ Preferably, m is an integer of 0 to 9. r1 is an integer of 1 to 9, r2 is an integer of 0 to 8, and r1+r2 is an integer of 1 to 9.

[0020] Among these, m is preferably an integer of 1 to 7, and more preferably an integer of 1 to 5. r1 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4. r2 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.

[0021] In particular, compound (3) is CF ２ =CF-OCF３ , C.F. ２ =CF-OCF ２ CF ３ , C.F. ２ =CF-OCF ２ CF ２ CF ３ is preferred, and CF ２ =CF-OCF ２ CF ２ CF ３ is more preferred.

[0022] When the copolymer contains unit C, the content of unit C is preferably 6.0 mol% or less, more preferably 4.0 mol% or less, and even more preferably 2.0 mol% or less, based on all units contained in the copolymer, from the viewpoint of reducing rigidity. When the copolymer contains unit C, the content of unit C is preferably 0.1 mol% or more, more preferably 0.2 mol% or more, and even more preferably 0.3 mol% or more, based on all units contained in the copolymer, from the viewpoint of improving mechanical properties. When the copolymer contains unit C, the content of unit C is preferably 0.1 to 6.0 mol%, more preferably 0.2 to 4.0 mol%, and even more preferably 0.3 to 2.0 mol%, based on all units contained in the copolymer, from the above viewpoints.

[0023] When the copolymer contains unit C, the total content of unit B and unit C is preferably 8.0 mol% or less, more preferably 7.0 mol% or less, and even more preferably 6.0 mol% or less, based on all units contained in the copolymer, from the viewpoint of reducing rigidity. When the copolymer contains unit C, the total content of unit B and unit C is preferably 2.1 mol% or more, more preferably 2.3 mol% or more, and even more preferably 2.5 mol% or more, based on all units contained in the copolymer, from the viewpoint of improving mechanical properties. When the copolymer contains unit C, the total content of unit B and unit C is preferably 2.1 to 8.0 mol%, more preferably 2.3 to 7.0 mol%, and even more preferably 2.5 to 6.0 mol%, based on all units contained in the copolymer, from the above viewpoint.

[0024] When the copolymer contains unit C, the ratio of the content of unit B to the total content of unit B and unit C is preferably 99.5 mol% or less, more preferably 99.0 mol% or less, and even more preferably 98.0 mol% or less, from the viewpoint of heat resistance. When the copolymer contains unit C, the ratio of the content of unit B to the total content of unit B and unit C is preferably 1.0 mol% or more, more preferably 5.0 mol% or more, and even more preferably 10.0 mol% or more, from the viewpoint of mechanical properties. When the copolymer contains unit C, the ratio of the content of unit B to the total content of unit B and unit C is preferably 1.0 to 99.5 mol%, more preferably 5.0 to 99.0 mol%, and even more preferably 10.0 to 98.0 mol%, from the above viewpoints.

[0025] When the copolymer contains units C, the content of units A relative to the total of units A, units B, and units C is preferably 94.0 mol% or more and less than 98.0 mol%, and from the viewpoints of heat resistance and surface smoothness of the obtained molded article, is more preferably 95.0 mol% or more and less than 98.0 mol%, and even more preferably 96.0 mol% or more and less than 98.0 mol%.

[0026] When the present copolymer contains units C, the content of units B relative to the total of units A, units B, and units C is preferably more than 2.0 mol% and less than 6.0 mol%, more preferably 2.05 mol% or more and less than 5.0 mol%, and even more preferably 2.08 mol% or more and less than 4.0 mol%, from the viewpoint of surface smoothness.

[0027] When the present copolymer contains units C, the content of units C relative to the total of units A, units B, and units C is preferably 0.1 mol % or more and less than 4.0 mol %, more preferably 0.15 mol % or more and less than 3.5 mol %, and even more preferably 0.2 mol % or more and less than 3.0 mol %, from the viewpoint of surface smoothness.

[0028] The copolymer may contain units based on other monomers other than TFE, compound (1), and compound (3) as needed. From the viewpoint of heat resistance, the content of units based on other monomers is preferably 10.0 mol% or less, more preferably 5.0 mol% or less, based on the total units contained in the copolymer. It is more preferable that the copolymer of this embodiment does not substantially contain units based on other monomers. "Substantially not containing units based on other monomers" means that the content of units based on other monomers is 0.01 mol% or less, based on the total units contained in the copolymer, more preferably 0.00 mol%. In other words, from the viewpoint of heat resistance, the total content of units A, units B, and units C is preferably 90.0 mol% or more, more preferably 95.0 mol% or more, even more preferably 99.99 mol% or more, and particularly preferably 100.00 mol%, based on the total units contained in the copolymer. Examples of the other monomers include hexafluoropropylene (HFP), fluoroolefins (excluding TFE, compound (1), and compound (3)); and acid anhydrides such as itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.

[0029] <Total number of functional groups in copolymer> The copolymer has 10 carbon atoms in its main chain ６ The total number of functional groups per unit, i.e., the total number of functional groups, is less than 150, and from the viewpoint of superior heat resistance, it is preferably less than 100, more preferably 50 or less, even more preferably 30 or less, and particularly preferably less than 25.

[0030] The functional groups in the copolymer 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. ３ Examples of terminal groups include terminal groups other than -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ , and -CH ２ Examples include OH.

[0031] The total number of functional groups is -CF=CF ２ , -CF ２H, -COF, -COOH, -COOCH ３ , -CONH ２ , and -CH ２ The total number of OH groups may be used. Hereinafter, -CF = CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ , and -CH ２ At least one selected from the group consisting of OH is also referred to as a "specific functional group".

[0032] The specific functional group is introduced by, for example, a chain transfer agent, a polymerization initiator, etc. used in producing the copolymer. Specifically, for example, when an alcohol is used as a chain transfer agent, a —CH ２ When a peroxide having an OH structure is used, the main chain terminal of the copolymer is formed with -CH ２ Furthermore, by polymerizing a monomer having a specific functional group as another monomer, the specific functional group is introduced into the side chain terminal of the copolymer.

[0033] As a method for adjusting the total number of functional groups in the copolymer to fall within the above range, a method of subjecting a polymer having functional groups to a fluorination treatment as described below can be mentioned. That is, the present copolymer is preferably a polymer that has been subjected to a fluorination treatment.

[0034] Infrared spectroscopy can be used to identify the types of functional groups contained in the copolymer and measure the total number of functional groups.

[0035] The total number of functional groups is measured by the following method. A copolymer to be measured is press-molded at 330°C to produce a film having a thickness of 300 to 350 μm. This film is analyzed using a Fourier transform infrared spectrometer to obtain an infrared absorption spectrum of the copolymer to be measured. Separately, an infrared absorption spectrum (base spectrum) of a copolymer that is completely fluorinated and does not contain any specific functional groups is obtained, and then a difference spectrum is obtained between the infrared absorption spectrum obtained from the copolymer to be measured that has not been subjected to fluorination treatment and the base spectrum. From the absorption peaks of the specific functional groups that appear in this difference spectrum, the total number of functional groups is calculated using the following formula (A) to determine the total number of functional groups in the main chain of 10 carbon atoms.６ The number of functional groups per molecule, N, is calculated for each functional group. The total number of functional groups is calculated by adding up the number of functional groups, N, for each functional group. N = I × K / t (A), where I: absorbance, K: correction coefficient, and t: film thickness (mm).

[0036] The absorption frequency, molar absorption coefficient, and correction factor for the specific functional group are shown in Table 1. The molar absorption coefficient of the specific functional group is determined from FT-IR (Fourier transform infrared spectroscopy) measurement data of the low molecular weight model compound.

[0037]

[0038] In the copolymer, -CH ２ CF ２ H, —CH ２ COF, -CH ２ COOH, -CH ２ COOCH ３ , and -CH ２ CONH ２ The absorption frequency of -CF is shown in the table. ２ H, -COF, -COOH (free and bonded), -COOCH ３ , and -CONH ２ From each absorption frequency, several tens of Kaiser (cm －１ ) becomes lower. For example, the number of -COF becomes lower. ２ Absorption frequency due to COF: 1883 cm －１ The number of functional groups determined from the absorption peak of -CH ２ Absorption frequency due to COF: 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.

[0039] <Copolymer Properties> (Melt Flow Rate) From the viewpoint of ease of molding, the melt flow rate (hereinafter also referred to as "MFR") of the present copolymer is preferably 1 to 200 g / 10 min, more preferably 1 to 150 g / 10 min, even more preferably 1 to 100 g / 10 min, particularly preferably 5 to 20 g / 10 min, and extremely preferably 13 to 20 g / 10 min. An example of a method for adjusting the MFR of the copolymer within the above range is a method of adjusting the molecular weight of the copolymer. The higher the molecular weight of the copolymer, the smaller the MFR. The MFR of the copolymer refers to the mass of the copolymer flowing out of an orifice with a diameter of 2 mm and a length of 8 mm in 10 minutes, measured at a temperature of 372°C and a load of 5 kg in accordance with ASTM D1238.

[0040] (Melting Point) From the viewpoint of heat resistance, the melting point of the copolymer in this embodiment is preferably 200 to 325°C, more preferably 220 to 320°C, and even more preferably 240 to 315°C. A method for adjusting the melting point of the copolymer within the above range includes a method of adjusting the content of unit B. The higher the content of unit B, the lower the melting point of the copolymer. The melting point of the 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 differential scanning calorimeter.

[0041] <Method for Producing the Copolymer> The present copolymer can be produced by a known method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. using the above-mentioned monomers (TFE and compound (1), and other monomers used as needed), and among these, production by solution polymerization is preferred. In producing the present copolymer, in addition to the above-mentioned monomers, a polymerization initiator, a polymerization medium, a chain transfer agent, etc. can be used.

[0042] The polymerization initiator is preferably a radical polymerization initiator having a half-life of 10 hours at a temperature of 0 to 100°C, and more preferably a radical polymerization initiator having the temperature of 20 to 90°C. Specific examples of the polymerization initiator include the various polymerization initiators exemplified in WO 2013 / 015202. The polymerization initiator may be used alone or in combination of two or more types. The amount of the polymerization initiator used is preferably 0.01 to 0.9 parts by mass, more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of the amount of the monomer used.

[0043] Examples of the polymerization medium include water, organic solvents, and mixed solvents of water and organic solvents. Fluorine-based solvents such as perfluorocarbons, hydrofluorocarbons, and hydrofluoroethers can be used as the organic solvent. Specific examples of the organic solvent include the polymerization media exemplified in International Publication No. 2013 / 015202. The polymerization medium may be used alone or in combination of two or more. A mixed solvent of water and a fluorine-based solvent is preferred as the polymerization medium, and a mixed solvent of water and a perfluorocarbon is more preferred. From the standpoints of suspension and economy, the amount of the fluorine-based solvent used is preferably 10 to 100% by mass relative to the mixed solvent. The amount of the polymerization medium used is preferably 3 times or more, more preferably 4.5 times or more, by mass, relative to the amount of the monomer used. Furthermore, the amount is preferably 20 times or less, more preferably 17 times or less.

[0044] The chain transfer agent may be selected from the group consisting of 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, hydrocarbons such as n-pentane, n-hexane, and cyclohexane, and CF ２ H ２Preferred are hydrofluorocarbons such as acetone, 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. Among these, at least one selected from the group consisting of alcohols, hydrocarbons, and hydrofluorocarbons is preferred, as it has a higher chain transfer constant and provides high stability of the end groups of the copolymer. At least one selected from the group consisting of alcohols and hydrocarbons is more preferred, and alcohols are even more preferred. Among alcohols, methanol or ethanol is preferred, with methanol being more preferred in terms of 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, more preferably 0.005 times or more, by mass, relative to the amount of monomer used. Also, it is preferably 5 times or less, more preferably 4 times or less.

[0045] The polymerization temperature is preferably 30 to 130°C, more preferably 35 to 110°C, even more preferably 40 to 90°C, and particularly preferably 60 to 90°C. A polymerization temperature of 60°C or higher provides excellent polymerizability. The polymerization pressure is preferably 0.5 to 3.0 MPaG, more preferably 0.9 to 2.5 MPaG. The polymerization time is preferably 1 to 12 hours.

[0046] When an aqueous dispersion containing the copolymer is obtained by polymerization, 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 polymerization, 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.

[0047] The copolymer obtained by polymerization may be formed into pellets. Copolymer pellets can be formed by conventional methods. Examples of methods for forming pellets include extruding the copolymer while melting it using a single-screw extruder, twin-screw extruder, or tandem extruder, cutting it to a predetermined length, and forming it into pellets. The extrusion temperature during melt extrusion varies depending on the melt viscosity of the copolymer and the production method, but is preferably between the melting point of the copolymer + 20°C and the melting point of the copolymer + 140°C. Conventional methods, such as strand cutting, hot cutting, underwater cutting, and sheet cutting, can be used to cut the copolymer. The resulting pellets may be heated to remove volatile components (degassing treatment). The resulting pellets may also 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.

[0048] The copolymer obtained by polymerization may be subjected to a fluorination treatment. By the fluorination treatment, the —COOH and —COOCH groups contained in the copolymer are removed. ３ , -CH ２ OH, -COF, -CF=CF ２ , -CONH ２ , and -CF ２ A specific functional group consisting of H is represented by -CF ３ As a result, even if the total number of functional groups of the copolymer exceeds a predetermined range, the total number of functional groups of the copolymer can be easily reduced by the fluorination treatment.

[0049] The fluorination treatment is carried out by contacting the copolymer that has not been fluorinated with a fluorine-containing compound. The fluorine-containing compound may be a fluorine radical source that generates fluorine radicals under the conditions of the fluorination treatment. The fluorine radical source may be F ２ Gas, N ２ F ２ , and halogen fluorides (e.g., IF ５ , ClF ３ ) are listed.

[0050] F ２The concentration of the fluorine radical source such as gas may be 100% by volume. ２ It is preferable to use a mixed gas obtained by diluting with an inert gas so that the gas concentration is 5 to 50% by volume (more preferably 15 to 30% by volume). Examples of the inert gas include nitrogen gas, helium gas, and argon gas, but nitrogen gas is preferable from an economical standpoint.

[0051] The fluorination treatment is usually carried out at a temperature below the melting point of the copolymer, preferably 20 to 240°C, more preferably 100 to 235°C. The fluorination treatment may be carried out by contacting the copolymer in a molten state with a fluorine-containing compound. As a specific method of the fluorination treatment, for example, a shelf on which pellets of the copolymer are placed is placed in an oven, and the inside of the oven is heated to F ２ An example of such a method is to fill a column packed with copolymer pellets with a gas or the above-mentioned mixed gas and heat it for a certain period of time. Another example is to pass a gas or the above-mentioned mixed gas through a flow column packed with copolymer pellets for a certain period of time while heating the column. The treatment time for the fluorination treatment varies appropriately depending on the total number of functional groups in the copolymer before the fluorination treatment, the target total number of functional groups, and the fluorination treatment method, but is, for example, 0.5 to 30 hours, and preferably 1 to 24 hours. The present copolymer is preferably produced by obtaining a copolymer by polymerization and then subjecting the copolymer to the above-mentioned fluorination treatment.

[0052] [Composition] A composition according to one embodiment of the present disclosure (hereinafter also referred to as "the composition") contains the above-described copolymer. Because the composition contains the copolymer, the heat resistance is excellent and the surface smoothness of the resulting molded article is excellent. The content of the copolymer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass, and extremely preferably 99 to 100% by mass, based on the total mass of the composition.

[0053] <Other Components> The present composition may contain other components in addition to those described above. Specific examples of such other components include resins other than the present copolymer, heat stabilizers, antioxidants, colorants, UV absorbers, fillers, crosslinking agents, crosslinking aids, and organic peroxides. When the present composition contains other components, the content of the other components is preferably 0.0000001 to 70 parts by mass, more preferably 0.0000005 to 60 parts by mass, and even more preferably 0.000001 to 50 parts by mass, per 100 parts by mass of the present copolymer in the present composition.

[0054] Among the other components, the total content of the compound represented by the following formula (2) (hereinafter also referred to as "compound (2)") is preferably less than 100 ppb by mass, more preferably less than 50 ppb by mass, and even more preferably less than 25 ppb by mass, relative to the entire composition, from the viewpoint of heat resistance. ３ -(CF ２ ) ｎ —COOH (2) In formula (2), n is an integer of 5 to 12.

[0055] The present composition can be produced by melt-kneading the present copolymer and the above-mentioned components, which are used as needed, by a known method.

[0056] <Characteristics of the composition> (Amount of eluted fluoride ions) The amount of eluted fluoride ions in the present composition measured in accordance with SEMI F57-0314 is set to 200 μg / m from the viewpoint of heat resistance. ２ Preferably, 175 μg / m or less ２ More preferably, 150 μg / m or less ２It is more preferable that the amount of eluted fluoride ions is less than 1000 kJ / cm. Hereinafter, the amount of eluted fluoride ions measured in accordance with SEMI F57-0314 will be simply referred to as the "amount of eluted fluoride ions." A copolymer contained in a composition with a high amount of eluted fluoride ions is thought to be a polymer that contains many specific functional groups and is easily decomposed by heat, chemicals, etc. Therefore, it is presumed that when the amount of eluted fluoride ions is within the above range, the composition will have excellent heat resistance. As a method for controlling the amount of eluted fluoride ions within the above range, for example, a method of reducing the total number of functional groups in the copolymer by subjecting a polymer having specific functional groups to a fluorination treatment described below can be mentioned. The amount of eluted fluoride ions is measured by the method described below.

[0057] [Molded Article] A molded article according to one embodiment of the present disclosure (hereinafter also referred to as "the molded article") is obtained by molding the above-described present copolymer or the above-described present composition. The molded article has excellent surface smoothness because it contains the present copolymer. Specific examples of the molded article include injection-molded articles obtained by injection molding the present copolymer or the present composition, extrusion-molded articles obtained by extrusion molding, blow-molded articles obtained by blow molding, transfer-molded articles obtained by transfer molding, press-molded articles obtained by press molding, rotation-molded articles obtained by rotation-molding, and coating films obtained by electrostatic coating. The molded article is preferably an injection-molded article because it can be obtained as an injection-molded article with high surface smoothness without corroding the mold used for molding.

[0058] Specific examples of the molded article include nuts, bolts, joints, films, bottles, gaskets, wire coating materials, tubes, hoses, pipes, valves, sheets, seals, packing, tanks, rollers, containers, cocks, connectors, filter housings, filter cages, flow meters, pumps, wafer carriers, and wafer boxes.

[0059] From the viewpoint of excellent heat resistance, the amount of eluted fluoride ions in the present molded body is 200 μg / m ２ Preferably, 175 μg / m or less ２ More preferably, 150 μg / m or less ２The method for measuring the amount of eluted fluoride ions is as described above.

[0060] The present copolymer, the present composition, or the present molded article can be used for the following purposes. Fluid transfer components for food manufacturing equipment, such as food packaging films, lining materials, packings, sealing materials, and sheets for fluid transfer lines used in food manufacturing processes; chemical liquid transfer components, such as chemical stoppers, packaging films, lining materials, packings, sealing materials, and sheets for fluid transfer lines used in chemical manufacturing processes; inner lining components for chemical liquid tanks and piping in chemical plants or semiconductor factories; fuel transfer components, such as O-rings, square rings, tubes, packings, valve core materials, hoses, and sealing materials used in automotive fuel systems and peripheral devices, and hoses and sealing materials used in automotive automatic transmissions; carburetor flange gaskets, shaft seals, valve stem seals, sealing materials, and hoses used in automotive engines and peripheral devices, as well as other automotive components, such as automotive brake hoses, air conditioner hoses, radiator hoses, and wire coating materials; chemical liquid transfer components for semiconductor manufacturing equipment, such as O-rings, square rings, tubes, packings, valve core materials, hoses, sealing materials, rolls, gaskets, diaphragms, and fittings; coating and ink components such as paint rolls, hoses, tubes, and ink containers for coating equipment; food and beverage transport components such as tubes, hoses, belts, packing, and fittings, such as food and beverage tubes or food and beverage hoses, 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 tubes and hoses for steam piping; anti-corrosion tapes for piping, such as tapes wrapped around piping on ship decks, etc.; various coating materials such as electric wire coating materials, optical fiber coating materials, and transparent surface coating materials and backing agents applied to the light-incident surface of photovoltaic elements in solar cells; sliding components such as diaphragms and various packings for diaphragm pumps; agricultural films, carrier films for fuel cells, and weather-resistant covers for various roofing materials and side walls, etc.; interior materials used in the construction field, and glass coating materials such as non-flammable fire-resistant safety glass; lining materials such as laminated steel sheets used in home appliances, etc.

[0061] In particular, the present molded article can be suitably used as piping components (e.g., piping, joints, gaskets, and packing), tubes, or films for transporting fluids. The present molded article can also be suitably used as a wire coating material. A specific use example is a coated electric wire comprising a core wire and a coating layer made of the present molded article that is provided around the core wire. A coated electric wire having a coating layer made of the present molded article has excellent electrical properties because the core wire is resistant to corrosion and there is almost no change in its outer diameter, and is therefore suitably used as a high-frequency transmission cable, a flat cable, a heat-resistant cable, and the like. Such a coated electric wire can be produced, for example, by melt-extrusion molding the present copolymer or the present composition onto a core wire to form a coating layer.

[0062] The present molded article can also be suitably used as a compressed member. The compressed member is a member used in a compressed and deformed state, and the size and shape of the compressed member are appropriately set depending on the application. The shape of the compressed member may be, for example, annular. The compressed member 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 its center. The compressed member can be used as a piping member for transporting fluids. The compressed member can also be used as a member for constituting a nonaqueous electrolyte battery, and is particularly suitable as a member used in contact with the nonaqueous electrolyte in a nonaqueous electrolyte battery. The compressed member can also be suitably used as a sealing member such as a sealing gasket and a sealing packing, and as an insulating member such as an insulating gasket and an insulating packing. A sealing member is a member used to prevent the leakage of liquid or gas or the intrusion of liquid or gas from the outside. An insulating member is a member used for electrical insulation. The compressed member may be a member used for both sealing and insulating purposes.

[0063] Hereinafter, embodiments of the present disclosure will be described in detail with reference to examples. Examples 2, 4, 6, and 11 are working examples, and Examples 1, 3, 5, and 7 to 10 are comparative examples. However, the present disclosure is not limited to these examples.

[0064] [Example 1] A 1.3 L stainless steel pressure reactor was charged with 872 g of a fluorine-based solvent (trade name: Asahiklin-AE3000, manufactured by AGC), CF ２ =CFCF ２ OCF ２ CF ２ CF ３ (84.3 g), methanol (19.7 g) as a chain transfer agent, and ultrapure water (262.5 g) were charged, and the temperature was raised to 70°C while stirring at 500 rpm. TFE was injected, and the pressure was raised to 1.4 MPaG. Next, an AE3000 solution (0.5 mass%, 6 ml, 0.027 parts by mass relative to 100 parts by mass of TFE and compound (1) combined) of tert-butyl peroxypivalate (temperature at which the half-life is 10 hours: 54.6°C, hereinafter also referred to as "PBPV") as a polymerization initiator was added, and polymerization was initiated. As the pressure in the reactor decreased with the initiation of polymerization, TFE was added to maintain the pressure constant. 0.6 g of compound (1) was injected every 9.4 g of TFE was injected. When 150 g of TFE had been injected, the reactor was cooled, and the polymerization reaction was terminated. After recovering the gas remaining in the reactor, a liquid containing a polymer slurry was extracted. After removing and recovering the AE3000 using an evaporator, the polymer and water were separated by filtration, and the resulting polymer was dried at 150°C for 15 hours to obtain Polymer Composition 1. １９ From the results of F-NMR analysis, the composition of Copolymer 1 contained in 99% by mass or more of the obtained Polymer Composition 1 was Unit A / Unit B=97.5 / 2.5 (molar ratio).

[0065] [Example 2] The obtained polymer composition 1 was subjected to a fluorination treatment as follows. Specifically, the obtained polymer composition 1 was placed in a vacuum reactor and heated to 210°C. After evacuation, fluorine gas diluted to 20% by volume with nitrogen gas was introduced. After 10 hours, the atmosphere in the reactor was thoroughly replaced with nitrogen gas to terminate the fluorination treatment, and a polymer composition 2 containing 99% by mass or more of copolymer 2 was obtained.

[0066] [Example 3] Polymer composition 3 was obtained in the same manner as polymer composition 1 in Example 1, except that the amount of methanol added was changed from 19.7 g to 27.7 g. Solid１９ From the results of F-NMR analysis, the composition of Copolymer 3 contained in 99% by mass or more of the obtained Polymer Composition 3 was Unit A / Unit B=97.5 / 2.5 (molar ratio).

[0067] [Example 4] Polymer composition 3 was fluorinated in the same manner as in Example 2, except that polymer composition 3 was used instead of polymer composition 1, to obtain polymer composition 4 containing 99% by mass or more of copolymer 4.

[0068] [Example 5] Polymer composition 5 was obtained in the same manner as polymer composition 1 in Example 1, except that the amount of methanol added was changed from 19.7 g to 10.7 g, the amount of compound (1) added before the start of polymerization was changed from 84.3 g to 134 g, and the step of injecting 0.6 g of compound (1) every time 9.4 g of TFE was inject- ed was changed to a step of injecting 1.2 g of compound (1) every time 8.8 g of TFE was inject- ed. Solid １９ From the results of F-NMR analysis, the composition of Copolymer 5 contained in 99% by mass or more of the obtained Polymer Composition 5 was Unit A / Unit B=96.0 / 4.0 (molar ratio).

[0069] [Example 6] Polymer composition 5 was subjected to a fluorination treatment in the same manner as in Example 2, except that polymer composition 5 was used instead of polymer composition 1, to obtain polymer composition 6 containing 99% by mass or more of copolymer 6.

[0070] [Example 7] Polymer composition 7-1 was obtained in the same manner as polymer composition 1 in Example 1, except that the amount of methanol added was changed from 19.7 g to 29 g, the amount of compound (1) added before the start of polymerization was changed from 84.3 g to 33.7 g, and the step of injecting 0.6 g of compound (1) every time 9.4 g of TFE was inject- ed was changed to a step of injecting 0.3 g of compound (1) every time 9.7 g of TFE was inject- ed. Solid １９From the results of F-NMR analysis, the composition of copolymer 7-1 contained in the obtained polymer composition 7-1 at 99% by mass or more was unit A / unit B=99.0 / 1.0 (molar ratio). Polymer composition 7-1 was fluorinated in the same manner as in Example 2, except that polymer composition 7-1 was used instead of polymer composition 1, to obtain polymer composition 7-2 containing copolymer 7-2 at 99% by mass or more.

[0071] [Example 8] Polymer composition 8-1 was obtained in the same manner as polymer composition 1 in Example 1, except that the amount of methanol added was changed from 19.7 g to 0 g, the amount of compound (1) added before the start of polymerization was changed from 84.3 g to 168.6 g, and the step of injecting 0.6 g of compound (1) every time 9.4 g of TFE was inject- ed was changed to a step of injecting 2.1 g of compound (1) every time 8.0 g of TFE was inject- ed. Solid １９ From the results of F-NMR analysis, the composition of copolymer 8-1 contained in the obtained polymer composition 8-1 at 99% by mass or more was unit A / unit B=92.0 / 8.0 (molar ratio). Polymer composition 8-1 was fluorinated in the same manner as in Example 2, except that polymer composition 8-1 was used instead of polymer composition 1, to obtain polymer composition 8-2 containing copolymer 8-2 at 99% by mass or more.

[0072] [Example 9] AE3000 (787.7 g), perfluoro(propyl vinyl ether) (PPVE, 84.3 g), and ultrapure water (262.5 g) were charged into a 1.3 L stainless steel pressure reactor, and the temperature was raised to 70°C while stirring at 500 rpm. TFE was injected and the pressure was raised to 1.4 MPaG. Next, an AE3000 solution (0.5 mass%, 6 ml) of PBPV was added to initiate polymerization. As the polymerization began, the pressure inside the reactor decreased, so TFE was added to maintain the pressure constant. When 150 g of TFE had been injected, the reactor was cooled and the polymerization reaction was terminated. After recovering the gas remaining in the reactor, a liquid containing a slurry-like polymer was extracted. AE3000 was removed and recovered using an evaporator, and the polymer and water were separated by filtration. The resulting polymer was dried at 150°C for 15 hours to obtain Polymer Composition 9. Solid １９From the results of F-NMR analysis, the composition of Copolymer 9 contained in 99% by mass or more of the obtained Polymer Composition 9 was Unit A / PPVE unit = 96.0 / 4.0 (molar ratio). The above "PPVE unit" is a unit based on PPVE.

[0073] [Example 10] Polymer composition 9 was fluorinated in the same manner as in Example 2, except that polymer composition 9 was used instead of polymer composition 1, to obtain polymer composition 10 containing 99% by mass or more of copolymer 10.

[0074] [Example 11] A 1.3 L stainless steel pressure reactor was charged with 679.5 g of a fluorine-based solvent (trade name: Asahiklin-AE3000, manufactured by AGC), CF ２ =CFCF ２ OCF ２ CF ２ CF ３ (138.8 g), compound (3) CF ２ = CFOCF ２ CF ２ CF ３ (25 g), methanol (27.9 g) as a chain transfer agent, and ultrapure water (338.6 g) were charged, and the temperature was raised to 70°C while stirring at 500 rpm. TFE was injected, and the pressure was raised to 1.4 MPaG. Next, an AE3000 solution (0.5 mass%, 6 ml, 0.027 parts by mass per 100 parts by mass of TFE, compound (1), and compound (3) combined) of tert-butyl peroxypivalate (temperature at which the half-life is 10 hours: 54.6°C, hereinafter also referred to as "PBPV") as a polymerization initiator was added, and polymerization was initiated. As the pressure in the reactor decreased with the initiation of polymerization, TFE was added to maintain the pressure constant. 0.6 g of compound (1) was injected every 9.4 g of TFE was injected. When 150 g of TFE had been injected, the reactor was cooled, and the polymerization reaction was terminated. After recovering the gas remaining in the reactor, a liquid containing a polymer slurry was extracted. After removing and recovering the AE3000 using an evaporator, the polymer and water were separated by filtration, and the resulting polymer was dried at 150°C for 15 hours to obtain Polymer Composition 11-1. １９From the results of F-NMR analysis, the composition of copolymer 11-1 contained in the obtained polymer composition 11-1 at 99% by mass or more was unit A / unit B / PPVE = 97.5 / 2.1 / 0.4 (molar ratio). Polymer composition 11-1 was fluorinated in the same manner as in Example 2, except that polymer composition 11-1 was used instead of polymer composition 1, to obtain polymer composition 11-2 containing copolymer 11-2 at 99% by mass or more.

[0075] [Measurement and Evaluation Methods] The measurement and evaluation methods are as follows. The results are shown in Table 2.

[0076] <Proportion of each unit in the copolymer> The proportion of each unit in the copolymer contained in the polymer composition obtained in each example was measured using a solid １９ It was determined by F-NMR analysis.

[0077] <MFR (Melt Flow Rate) of Copolymer> Using a melt indexer (manufactured by Techno Seven Co., Ltd.), the mass (g) of the copolymer flowing out of an orifice having a diameter of 2 mm and a length of 8 mm in 10 minutes was measured under conditions of a temperature of 372°C and a load of 5 kg in accordance with ASTM D1238, and this was taken as the MFR (g / 10 min).

[0078] <Melting Point of Copolymer> The melting point (°C) of the copolymer was determined from the endothermic peak observed when the copolymer was heated to 300°C at a rate of 10°C / min in an air atmosphere using a differential scanning calorimeter (trade name "DSC7020", manufactured by Hitachi High-Tech Science Corporation).

[0079] <Total Number of Functional Groups in Copolymer> The polymer composition obtained in each example was molded by hot pressing at 330°C to produce a film with a thickness of 0.30 to 0.35 mm. This film was scanned 40 times using a Fourier transform infrared spectrometer (FT-IR, "Spectrum One", manufactured by PerkinElmer) and analyzed to obtain an infrared absorption spectrum. Next, each of the above polymer compositions was subjected to a fluorination treatment for a long period of time (specifically, 20 hours) similar to the fluorination treatment performed in Example 2 above, and a polymer composition containing each base copolymer that was completely fluorinated and had no specific functional groups was separately prepared, and a base film was obtained in the same manner as above. A difference spectrum from the base spectrum of the base film was obtained. From the absorption peaks of the specific functional groups appearing in this difference spectrum, -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ , and -CH ２ For each functional group of OH, the carbon number of the copolymer in the sample is 10 according to the following formula (A): ６ The number of functional groups per unit, N, was calculated. The number of functional groups, N, for each functional group was then summed to determine the total number of functional groups. The correction coefficients used are as shown in Table 1 above. N = I x K / t (A) I: absorbance K: correction coefficient t: film thickness (mm) If the number of functional groups is less than 150, the specific functional groups are sufficiently reduced, and the copolymer is likely to have excellent heat resistance. In the table, "400<" means more than 400, "25>" means less than 25, and "100>" means 25 or more but less than 100.

[0080] <Amount of eluted fluoride ions> 10 g of a sample pelletized from the polymer composition obtained in each example and 20 mL of 3.6 wt % hydrochloric acid were placed in a polypropylene container that had been washed three times with 3.6 wt % hydrochloric acid water (EL grade diluted with ultrapure water) heated to 60°C, and the sample was immersed in hydrochloric acid for 7 days. The liquid after immersion was analyzed by ICP-MS to quantify the amount of fluoride ions contained in the liquid. The amount of fluoride ions contained in the liquid was 200 μg / m ２If the fluoride ion elution amount is less than 2000 μg / m, the amount of eluted fluoride ions is sufficiently reduced, and the heat resistance is likely to be excellent. ２ Exceeding 150μg / m ２ means less than.

[0081] <Content of Compound (2)> The content (mass ppb) of compound (2) in the polymer composition obtained in each example was measured by solid １９ The content was determined by F-NMR analysis. If the total content of the compound (2) is less than 100 mass ppb, the content of the compound (2) is sufficiently reduced and the heat resistance is likely to be excellent. In the table, "1000<" means more than 1000 mass ppb, "200<" means more than 200 mass ppb, and "25>" means less than 25 mass ppb.

[0082] <Evaluation of Surface Smoothness> The polymer composition obtained in each example was press-molded at 340°C to obtain a film having a thickness of 1 mm. The press molding was performed using a heated press ("SA-301" manufactured by Tester Sangyo Co., Ltd.). The smoothness of the surface of the obtained film was confirmed by touch with a finger and evaluated according to the following criteria. A: The surface is smooth. B: The surface is rough.

[0083] Furthermore, among the obtained films, the films of Examples 2, 4, 6, and 11 were examined for fine voids on the surface using a magnifying glass. The fewer the number of fine voids, the higher the surface smoothness. As a result of the examination, the number of fine voids was the smallest in Example 2, followed by Examples 4, 6, and 11. In other words, the number of voids was in the order of Example 2 < Example 4 < Example 6 < Example 11.

[0084] <Evaluation of Heat Resistance> The polymer composition obtained in each example was press-molded at 340°C to obtain a film having a thickness of 1 mm. The press molding was performed using a heated press ("SA-301" manufactured by Tester Sangyo Co., Ltd.). The obtained film was visually inspected for the presence or absence of coloring and foaming due to heat, and evaluated according to the following criteria: A: Neither coloring nor foaming was observed. B: At least one of coloring and foaming was observed.

[0085]

[0086] As shown in Table 2, it was confirmed that copolymers containing 90.0 mol% or more of units A and units B in total, containing units B in a range of more than 2.0 mol% to 6.0 mol% and having a total number of functional groups of less than 150, and compositions containing the copolymers have excellent heat resistance and excellent surface smoothness of the resulting molded articles. Furthermore, from the results of checking the number of fine voids with a magnifying glass, it was confirmed that Example 2 had the best surface smoothness, and that the order of surface smoothness was Example 2 > Example 4 > Example 6 > Example 11.

[0087] The disclosure of Japanese Patent Application No. 2024-081250, filed on May 17, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A copolymer containing units A based on tetrafluoroethylene and units B based on a compound represented by the following formula (1), wherein the content of the units B is more than 2.0 mol% and not more than 6.0 mol% of all units contained in the copolymer, the total content of the units A and the units B is 90.0 mol% or more of all units contained in the copolymer, and the copolymer has a main chain carbon number of 10 ６ A copolymer having a total number of functional groups per CF unit of less than 150. ２ =CF-CF ２ -O-Rf １ ...(1) In formula (1), Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an etheric oxygen atom between carbon atoms.

2. The copolymer according to claim 1, wherein the melt flow rate of the copolymer measured at 372°C in accordance with ASTM D1238 is 1 to 200 g / 10 min.

3. The copolymer according to claim 1, wherein the copolymer is substantially free of units C based on a compound represented by the following formula (3): CF ２ ═CF—O—Rf ３ ...(3) In formula (3), Rf ３ is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an etheric oxygen atom between carbon atoms.

4. The copolymer according to claim 1, wherein the copolymer contains units C based on a compound represented by the following formula (3), and the content of the units C is 6.0 mol % or less based on all units contained in the copolymer: CF ２ ═CF—O—Rf ３ ...(3) In formula (3), Rf ３ is a perfluoroalkyl group having 1 to 10 carbon atoms, which may have an etheric oxygen atom between carbon atoms.

5. A composition comprising the copolymer according to any one of claims 1 to 4.

6. The amount of fluoride ions eluted is 200 μg / m as measured based on SEMI F57-0314. ２ 6. The composition of claim 5, wherein:

7. The composition according to claim 5, wherein the total content of the compounds represented by the following formula (2) is less than 100 mass ppb with respect to the entire composition: CF ３ -(CF ２ ) ｎ —COOH (2) In formula (2), n is an integer of 5 to 12.

8. A molded article of the composition according to claim 5.

9. A molded article of the composition according to claim 6.

10. A molded article of the composition according to claim 7.

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