Pellet, method for producing pellet, and molded body

Abstract

Provided is a pellet and a method for producing the pellet with which it is possible to obtain a molded body having a small amount of undissolved pellet and excellent heat resistance, acid resistance, folding resistance, and high-speed formability for electric wire.　This pellet is cylindrical and contains a copolymer having units based on tetrafluoroethylene, units based on ethylene, and units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2), wherein the total content of the units based on tetrafluoroethylene and the units based on ethylene is 80.00 to 99.50 mol% of the total units of the copolymer, the content of the units based on a specific compound is 0.50 to 5.00 mol% of the total units of the copolymer, the height L of the pellet is greater than 2.00 mm, and when the short diameter of the pellet is D1 mm and the long diameter is D2 mm, the relationship in formula (Z) is satisfied, the specific surface area of ​​the pellet is 1,000 to 2,500 mm2 / g, and the melt flow rate of the pellet measured in accordance with ASTM D3169 under conditions of a temperature of 297°C and a load of 49 N is 1 to 50 g / 10 min.

Description

Pellets, pellet manufacturing method and compact

[0001] The present invention relates to a pellet, a method for producing the pellet, and a compact.

[0002] Ethylene / tetrafluoroethylene copolymer (hereinafter also referred to as "ETFE") is excellent in heat resistance, weather resistance, electrical insulation, non-stickiness, water and oil repellency, etc., and is characterized by high moldability and mechanical strength among fluororesins. Therefore, a variety of molded articles such as electric wire coverings, tubes, sheets, films, filaments, pump casings, joints, packings, linings and coatings are produced by melt molding methods such as extrusion molding, blow molding, injection molding and rotational molding. For example, Patent Document 1 discloses pellets of fluororesin.

[0003] JP 2017-128119 A

[0004] When pellets containing ETFE are used as a constituent material of molded articles, they are required to be excellent in various properties. Specifically, when various molded articles are produced using the pellets, it is required that the pellets have little undissolved residue, and that the obtained molded articles have excellent heat resistance, acid resistance, folding resistance and high-speed wire moldability.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide pellets and a method for producing the same, which can produce a molded article having little undissolved pellets and excellent heat resistance, acid resistance, folding resistance, and high-speed wire formability. Another object of the present invention is to provide a molded article using the pellets.

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0007] [1] A cylindrical pellet comprising a copolymer having units based on tetrafluoroethylene, units based on ethylene, and units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2), described later, wherein the total content of the units based on tetrafluoroethylene and the units based on ethylene is 80.00 to 99.50 mol % based on all units of the copolymer, the content of the units based on the specific compound is 0.50 to 5.00 mol % based on all units of the copolymer, the height L of the pellet is more than 2.00 mm, and the minor axis of the pellet is D １ mm, and the major diameter is D ２ mm, the relationship of formula (Z) described below is satisfied, and the specific surface area of ​​the pellets is 1,000 to 2,500 mm ２ / g, and the melt flow rate of the pellets, measured in accordance with ASTM D3169 at a temperature of 297°C and a load of 49 N, is 1 to 50 g / 10 min. [2] The pellets according to [1], wherein the copolymer is a copolymer consisting only of units based on tetrafluoroethylene, units based on ethylene, and units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2). [3] The pellets according to [1] or [2], wherein the specific compound is the compound represented by formula (1). [4] The pellets according to any one of [1] to [3], wherein the content of the units based on tetrafluoroethylene is 45.00 to 67.00 mol % based on all units of the copolymer. [5] The pellets according to any one of [1] to [4], wherein the content of the units based on ethylene is 30.0 to 55.0 mol % based on all units of the copolymer. [6] The pellets according to any one of [1] to [5], wherein the melting point of the copolymer is 210° C. to 290° C. [7] A method for producing pellets according to any one of [1] to [6], comprising melt-kneading the copolymer using a twin-screw extruder, extruding the resulting molten copolymer through a die of the twin-screw extruder, and cutting strands containing the copolymer with a pelletizer to obtain pellets containing the copolymer. [8] A molded product obtained by molding the pellets according to any one of [1] to [6].

[0008] According to the present invention, there can be provided pellets from which a molded article can be obtained that has little undissolved pellets and is excellent in heat resistance, acid resistance, folding resistance, and high-speed wire formability. Also, there can be provided a molded article using the above pellets.

[0009] 1 is a schematic diagram showing an example of an embodiment of a pellet of the present invention. 2 is a schematic diagram showing an example of an embodiment of a pellet of the present invention.

[0010] The meanings of terms used in the present invention are as follows. A numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In the numerical ranges described in this specification in stages, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0011] "Unit" is a general term for an atomic group derived from one molecule of the above-mentioned monomer, which is formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a part of the above-mentioned atomic group. "Unit based on a monomer" will also be simply referred to as "unit" below. The content (mass% or mol%) of each unit relative to the total units contained in the copolymer is determined by analyzing the copolymer by solid-state nuclear magnetic resonance spectroscopy (NMR), and usually the content of each unit calculated from the amount of each monomer added is approximately the same as the actual content of each unit. "TFE unit" is a unit based on tetrafluoroethylene (hereinafter also referred to as "TFE"), and "E unit" is a unit based on ethylene. "A unit" is a unit based on a specific compound described below.

[0012] [Pellets] The pellets of the present invention (hereinafter also simply referred to as "pellets") are cylindrical pellets containing a copolymer having TFE units, E units, and A units (hereinafter also simply referred to as "copolymer"), wherein the total content of the TFE units and E units is 80.00 to 99.50 mol% based on all units of the copolymer, the content of the A units is 0.50 to 5.00 mol% based on all units of the copolymer, the height L of the pellets is more than 2.00 mm, and the minor axis of the pellets is D. １mm, and the major diameter is D ２ mm, the relationship of the formula (Z) described below is satisfied, and the specific surface area of ​​the pellet is 1,000 to 2,500 mm ２ / g, and the melt flow rate (hereinafter also simply referred to as "MFR") of the pellets measured in accordance with ASTM D3169 under conditions of a temperature of 297°C and a load of 49 N is 1 to 50 g / 10 min.

[0013] Although the details of why the pellets of the present invention exhibit the desired properties are unclear, the inventors speculate that the reason is as follows. Specifically, when the specific surface area of ​​the pellets is 1,000 mm ２ When the specific surface area of ​​the pellet is 2,500 mm / g or more, the area of ​​the pellet that comes into contact with the heat source when producing a molded product such as a film from the pellet becomes appropriate, and the pellet is less likely to remain unmelted. ２ When the MFR is 1.0 / g or less, the area of ​​contact between the pellets and the heat source during the production of a molded product such as a film is appropriate, thermal degradation is unlikely to occur, and heat resistance is excellent. When the pellet height L is more than 2.00 mm, the time required for heat to be transferred to the end of the pellet that is not in contact with the mold or extruder during the production of a molded product such as a film is appropriate, thermal degradation is unlikely to occur, and heat resistance is excellent. Furthermore, since the content of A units is equal to or greater than a predetermined amount, molded products obtained from the pellets exhibit appropriate flexibility and therefore excellent folding endurance. On the other hand, since the content of A units, which are prone to deterioration due to the action of acids, etc., is equal to or less than a predetermined amount, acid resistance is excellent. In particular, it is expected that the acid resistance of a coating film (hereinafter simply referred to as "coating film") formed by electrostatic coating of a powder obtained from the pellets will also be excellent. Furthermore, when the MFR is within a predetermined range, the pellets have appropriate fluidity when used to produce a molded product, making it easy to mold, and also have excellent high-speed wire moldability.

[0014] <Copolymer> The pellets contain a copolymer having TFE units, E units, and A units. The A units are units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2).

[0015] CZ ２ =CX(CF ２) ｍ Y Formula (1) CF ２ =CF-O-(CF ２ ) ｎ F Formula (2) In formula (1), X, Y, and Z each independently represent a hydrogen atom or a fluorine atom, and m represents an integer of 2 to 6. Two Zs may be the same or different. In formula (2), n represents an integer of 1 to 6.

[0016] In the compound represented by formula (1), X and the two Zs are preferably hydrogen atoms from the viewpoint of polymerizability. Y is preferably a fluorine atom from the viewpoint of heat resistance. m is an integer of 2 to 6, preferably an integer of 3 to 6, and more preferably 3 or 4.

[0017] Specific examples of the compound represented by formula (1) include CH ２ =CH(CF ２ ) ２ F, CH ２ =CH(CF ２ ) ４ F (hereinafter also referred to as "PFBE"), CH ２ =CH(CF ２ ) ６ F, CH ２ =CF(CF ２ ) ３ F and CH ２ =CF(CF ２ ) ４ F, PFBE, CH ２ =CH(CF ２ ) ６ F or CH ２ =CF(CF ２ ) ３ F is preferred, and PFBE is more preferred.

[0018] In the compound represented by formula (2), n is preferably an integer of 1 to 4, more preferably an integer of 2 to 4, and even more preferably 3.

[0019] Specific examples of the compound represented by formula (2) include CF ２ =CF-O-(CF ２ ) F, CF ２ =CF-O-(CF ２ ) ２ F, CF２ =CF-O-(CF ２ ) ３ F, CF ２ =CF-O-(CF ２ ) ４ F, CF ２ =CF-O-(CF ２ ) ５ F and CF ２ =CF-O-(CF ２ ) ６ F is mentioned, and CF ２ =CF-O-(CF ２ ) ３ F is preferred.

[0020] The copolymer may have, as A units, either units based on a compound represented by formula (1) (hereinafter also referred to as "A1 units") or units based on a compound represented by formula (2) (hereinafter also referred to as "A2 units"), or may have both A1 units and A2 units. When the copolymer has both A1 units and A2 units, the "content of A units" means the sum of the content of A1 units and the content of A2 units.

[0021] As the copolymer, a copolymer having TFE units, E units and A1 units, or a copolymer having TFE units, E units and A2 units is preferred, and from the viewpoint of more excellent folding endurance, a copolymer having TFE units, E units and A1 units is more preferred.

[0022] The total content of TFE unit and E unit is 80.00 to 99.50 mol% based on the total units of copolymer, and from the viewpoint of folding endurance and acid resistance of coating film, it is preferably 85.00 to 99.5 mol%, more preferably 90.00 to 99.50 mol%, and more preferably 95.0 to 99.50 mol%.In particular, from the viewpoint of excellent folding endurance, the total content of TFE unit and E unit is preferably 98.50 mol% or less based on the total units of copolymer, more preferably 98.20 mol% or less, even more preferably 97.20 mol% or less, and particularly preferably 96.30 mol% or less.In particular, from the viewpoint of excellent acid resistance of coating film, the total content of TFE unit and E unit is preferably 96.30 mol% or more based on the total units of copolymer, more preferably 97.10 mol% or more, even more preferably 98.10 mol% or more, and particularly preferably 99.20 mol% or more. The content of TFE units is preferably 45.00 to 67.00 mol%, more preferably 48.00 to 64.90 mol%, even more preferably 50.00 to 64.50 mol%, and particularly preferably 50.0 to 57.5 mol%, based on the total units of the copolymer. If it is above the lower limit, the heat resistance of the molded article obtained from the pellets will be better, and if it is below the upper limit, the mechanical properties of the molded article will be better. The content of E units is preferably 30.0 to 55.0 mol%, more preferably 35.00 to 51.90 mol%, even more preferably 35.0 to 49.50 mol%, and particularly preferably 39.0 to 46.50 mol%, based on the total units of the copolymer. If it is above the lower limit, the mechanical properties of the molded article obtained from the pellets will be better, and if it is below the upper limit, the heat resistance of the molded article will be better.

[0023] The content of A units is 0.50 to 5.00 mol% relative to the total units of the copolymer, and from the viewpoints of folding endurance and acid resistance of the coating film, it is preferably 0.60 to 4.00 mol%, more preferably 0.8 to 3.90 mol%. In particular, from the viewpoint of excellent folding endurance of the molded article, the content of A units is preferably 1.50 mol% or more relative to the total units of the copolymer, more preferably 1.80 mol% or more, even more preferably 2.80 mol% or more, and particularly preferably 3.70 mol% or more. In particular, from the viewpoint of excellent acid resistance of the coating film, the content of A units is preferably 3.70 mol% or less relative to the total units of the copolymer, more preferably 2.90 mol% or less, even more preferably 1.90 mol% or less, and particularly preferably 0.80 mol% or less.

[0024] The copolymer may have units based on a monomer other than TFE, ethylene, and the specific compound. Specific examples of the other monomer include fluoroolefins (e.g., vinyl fluoride, vinylidene fluoride, trifluoroethylene, and hexafluoroisobutylene, excluding the specific compound), CF ２ =CFORf １ SO ２ Y １ (However, Rf １ is a perfluoroalkylene group having 1 to 10 carbon atoms which may contain an oxygen atom between the carbon atoms, and Y １ is a halogen atom or a hydroxyl group.), CF ２ =CFORf ２ CO ２ Y ２ (However, Rf ２ is a perfluoroalkylene group having 1 to 10 carbon atoms which may contain an oxygen atom between the carbon atoms, and Y ２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.), CF ２ =CF(CF ２ ) pOCF=CF ２(where p is 1 or 2), fluorine-containing monomers having a ring structure (for example, perfluoro(2,2-dimethyl-1,3-dioxole), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, perfluoro(2-methylene-4-methyl-1,3-dioxolane)), itaconic acid, itaconic anhydride, citraconic acid, and citraconic anhydride. Among these, itaconic acid, itaconic anhydride, citraconic acid, and citraconic anhydride are preferred, and itaconic anhydride is more preferred.

[0025] When the copolymer contains units based on other monomers, the content of the units based on other monomers is preferably 0.01 to 2.00 mol %, more preferably 0.10 to 1.00 mol %, based on the total units of the copolymer.

[0026] The copolymer preferably comprises TFE units, E units and A units and does not contain units derived from other monomers, and more preferably comprises TFE units, E units and A1 units and does not contain A2 units and units derived from other monomers. Specifically, the total content of TFE units, E units and A units is preferably 90.00 to 100.00 mol%, more preferably 99.90 to 100.00 mol%, based on the total units of the copolymer.

[0027] The content of the copolymer is preferably from 50 to 100% by mass, more preferably from 70 to 100% by mass, and even more preferably from 90 to 100% by mass, based on the total mass of the pellets.

[0028] <Other Components> The pellets may contain other components in addition to those described above. Specific examples of other components include resins other than the copolymer, heat stabilizers, antioxidants, colorants, UV absorbers, fillers, crosslinking agents, crosslinking aids, and organic peroxides. When the pellets contain 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, relative to 100 parts by mass of the copolymer in the pellets.

[0029] <Pellet Shape> The pellets have a columnar shape. The shape of both end faces of the columnar body is not particularly limited. Examples of the columnar body include a polygonal columnar body having a polygonal end face shape, a cylindrical body having a circular end face shape, or modified shapes of these, with a cylindrical body being preferred. Note that the cylindrical body includes both a substantially elliptical columnar body and a substantially cylindrical body. The end faces of the columnar body do not have to be parallel to each other. The columnar body may be solid or hollow, but is preferably solid.

[0030] 1 and 2, the height L and minor diameter D of the pellet 10 are shown. １ and major diameter D ２ FIG. 1 is a schematic diagram showing an example of an embodiment of the pellet of the present invention, and is a schematic diagram of a pellet 10 placed on a horizontal surface and observed from the horizontal direction. The height L of the pellet 10 is the height from the surface of the substrate, and is the distance from the horizontal plane to the highest part of the pellet. An example of the horizontal plane is the horizontal plane of a container such as a tray. The height L of the pellet is more than 2.00 mm, and from the viewpoint of heat resistance, it is preferably 2.20 mm or more, more preferably 2.50 mm or more. It is also preferably 3.00 mm or less.

[0031] 2 is a schematic diagram showing an example of an embodiment of the pellet of the present invention, and is a schematic diagram of a pellet 10 placed on a horizontal surface and observed from the normal direction to the horizontal surface. １ and major diameter D ２ The measurement method for the height L and the minor diameter D of ten pellets is a method using a measuring instrument such as a caliper. Specifically, the height, minor diameter, and major diameter of ten pellets are measured with a caliper, and the arithmetic mean values ​​of the measured values ​​are calculated as the height L and the minor diameter D of the pellets. １ and major diameter D ２ This can be done as follows.

[0032] The minor axis of the pellet is D １ mm, and the major diameter is D ２ When the D in formula (Z) is expressed as mm, the pellet of the present invention satisfies the relationship of formula (Z). The pellet of the present invention preferably satisfies the relationship of formula (Z1). １ and D２ For example, if the minor axis is 1 mm and the major axis is 2 mm, the numerical value introduced as D １ As 1, D ２ 2 is introduced as 2. By satisfying the relationship of formula (Z), preferably formula (Z1), an appropriate pellet size is obtained, and the desired effects of the present invention are easily achieved. Furthermore, by satisfying the relationship of formula (Z), preferably formula (Z1), the resin filling rate in the screw during injection molding, extrusion molding, etc. becomes appropriate, and problems such as incomplete melting due to an excessive filling rate and excessive thermal history can be prevented. Furthermore, problems such as incomplete melting and excessive thermal history can be prevented during press molding. In this specification, for convenience, the terms short diameter and long diameter are used even if the short diameter and long diameter have the same value. That is, D １ and D ２ and may be equivalent.

[0033] 2.50≦D １ ×D ２ ≦9.60 Formula (Z) 4.00≦D １ ×D ２ ≦7.50 Formula (Z1)

[0034] D １ is preferably 1.58 to 3.10 mm, and more preferably 1.58 to 2.80 mm. ２ is preferably 1.58 to 3.10 mm, and more preferably 1.58 to 2.80 mm. ２ -D １ (Long diameter D ２ From minor diameter D １ The value obtained by subtracting (a value obtained by subtracting (b) from (c)) is preferably 0.5 or less, and more preferably 0.2 or less.

[0035] The specific surface area of ​​the pellets is 1,000 to 2,500 mm ２ / g, and 1,350 to 1,500 mm ２ / g is preferred, and 1,400 to 1,450 mm ２ The specific surface area of ​​the pellets can be calculated by a known method. Specifically, the specific surface area of ​​the pellets is calculated by dividing the height L, the minor axis D １ , and major diameter D ２ It can be calculated using the following:

[0036] Specific examples of methods for controlling the pellet shape include methods of controlling the discharge shape of the twin-screw extruder, the rotation speed of the pelletizer, the strand take-up speed, the resin feed amount, etc. In particular, the specific surface area of ​​the pellets tends to increase when the rotation speed of the pelletizer or the strand take-up speed is increased, and tends to decrease when the resin feed amount is increased.

[0037] <Pellet Properties> (MFR) The MFR of the pellets, measured in accordance with ASTM D3169 under conditions of a temperature of 297°C and a load of 49 N, is 1 to 50 g / 10 min. From the viewpoint of high-speed moldability, the MFR is preferably 3 to 49 g / 10 min, more preferably 4 to 47 g / 10 min, and even more preferably 5 to 17 g / 10 min. More specifically, the MFR is obtained by measuring the mass of solid matter flowing out of an orifice having a diameter of 2 mm and a length of 8 mm in 10 minutes under conditions of a temperature of 297°C and a load of 49 N in accordance with ASTM D3169.

[0038] (Melting Point) The melting point of the pellets is preferably 210°C or higher, more preferably 215°C or higher, even more preferably 220°C or higher, and particularly preferably 225°C or higher, from the viewpoint of superior mechanical strength when used at high temperatures. The upper limit of the melting point of the pellets is preferably 290°C or lower, more preferably 280°C or lower, and even more preferably 270°C or lower, from the viewpoint of superior moldability. The melting point of the pellets is preferably 210°C to 290°C, more preferably 215°C to 280°C, and even more preferably 225°C to 270°C, from the viewpoint of a well-balanced superiority in mechanical strength and moldability when used at high temperatures. The melting point of the pellets is the temperature corresponding to the endothermic peak detected when the pellets are heated at a rate of 10°C / min in an air atmosphere using a differential scanning calorimeter.

[0039] <Method for producing pellets> The method for producing pellets is not particularly limited, and may be a known method for producing pellets. Among them, a preferred method for producing pellets is to produce the above-mentioned copolymer, melt-knead the copolymer using a twin-screw extruder, and pelletize the copolymer to obtain pellets.

[0040] As the method for producing above-mentioned copolymer, TFE, ethylene, specific compound, and if necessary, other monomers can be used to produce by known methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization, among which, solution polymerization is preferred for production.In the production of copolymer, besides above-mentioned monomers, polymerization initiator, polymerization medium and chain transfer agent etc. can be used.

[0041] The amount of the monomer used can be appropriately selected depending on the composition and molecular weight of the target solid composition, etc. In particular, the amount of the specific compound used is preferably 0.1 to 3.0 parts by mass, more preferably 0.2 to 2.5 parts by mass, based on the total parts by mass of the polymerization solvent.

[0042] As the polymerization initiator, a radical polymerization initiator having a half-life of 10 hours at a temperature of 0 to 100°C is preferred, and a radical polymerization initiator having the above temperature of 20 to 90°C is more preferred. Specific examples of the polymerization initiator include 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] As the polymerization medium, perfluorocarbons, hydrofluorocarbons, hydrofluoroethers, etc. can be used. Specific examples of the polymerization medium 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. The amount of the polymerization medium used is preferably 5 times or more, more preferably 7 times or more, by mass ratio relative to the amount of the monomer used. Also, it 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 CF２ H ２ Preferred 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 they have a higher chain transfer constant and provide high stability to 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. Methanol or ethanol is particularly preferred, and methanol is most preferred from the standpoint of reactivity and availability. The chain transfer agent may be used alone or in combination with two or more. 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] From the viewpoint of heat resistance, the polymerization temperature is preferably 15 to 75°C, more preferably 15 to 60°C, even more preferably 20 to 58°C, and particularly preferably 25 to 55°C. If the polymerization temperature is 25°C or higher, the polymerizability is excellent. The polymerization pressure is preferably 0.5 to 3.0 MPa, more preferably 0.9 to 2.5 MPa. The polymerization time is preferably 1 to 12 hours.

[0046] The method of melt-kneading the copolymer using a twin-screw extruder includes melt-kneading the copolymer introduced into a raw material supply port of the twin-screw extruder in a twin-screw extruder having a melting zone. The twin-screw extruder may have a plurality of melting zones.

[0047] When a twin-screw extruder has multiple melting zones, the set temperature of the melting zone located most upstream of the multiple melting zones (hereinafter also referred to as the first melting zone) is preferably the melting point of the copolymer + 25°C or more, more preferably the melting point + 50°C or more, and even more preferably the melting point + 60°C or more. The set temperature of the first melting zone is preferably the melting point of the copolymer + 100°C or less, more preferably the melting point + 60°C or less, and even more preferably the melting point + 40°C or less. If the set temperature of the first melting zone is equal to or higher than the lower limit of the above range, melting of the copolymer is promoted, and excessive decomposition of the copolymer due to scission of molecular chains by the screw is suppressed. If the set temperature of the first melting zone is equal to or lower than the upper limit of the above range, oxidative decomposition of the copolymer due to heat is suppressed.

[0048] The screw rotation speed is preferably 200 to 450 rpm, more preferably 250 to 400 rpm. If the screw rotation speed is within the above range, decomposition of the copolymer due to shearing of the screw can be suppressed. The copolymer feed rate is preferably 10 to 100 kg / hour, more preferably 20 to 70 kg / hour, and even more preferably 25 to 55 kg / hour.

[0049] As a pelletization method, a method is preferred in which the molten copolymer discharged from the twin-screw extruder is extruded through a die attached to the discharge port of the twin-screw extruder to form strands, and the strands are cut and pelletized by a pelletizer to obtain pellets.

[0050] The conditions for extruding the molten copolymer are not particularly limited, and known conditions can be appropriately adopted. The diameter of the strand is preferably 1 to 10 mm, more preferably 1 to 6 mm, and even more preferably 2 to 5 mm. If the diameter of the strand is equal to or greater than the lower limit of the above range, the strand is not too thin and is less likely to break before being cut by the pelletizer. If the diameter of the strand is equal to or less than the upper limit of the above range, the strand is not too thick, cooling does not take much time, and pellets of the desired quality and shape can be easily obtained.

[0051] The temperature of the strand immediately after being discharged from the die is preferably the melting point of the copolymer + 10 to 150°C, more preferably the melting point + 20 to 130°C, and even more preferably the melting point + 30 to 100°C. If the strand temperature is at least the lower limit of the above range, melt fracture from the die discharge opening is reduced, thereby increasing the stability of the strand. If the strand temperature is at most the upper limit of the above range, decomposition of the copolymer is suppressed.

[0052] The means for transporting the strands is not particularly limited as long as it can transport the strands, and examples of the transport means include a belt conveyor, a mesh conveyor, a net conveyor, and a pelletizer.

[0053] The strands are preferably cooled. The strands may be air-cooled or water-cooled. Air-cooling methods include a method using a blower or the like, and a method of cooling the strands while transporting them by a transport means. Water-cooling methods include a method of immersing the strands in a cooling solution such as water filled in a container, and a method of spraying the cooling solution onto the strands.

[0054] The temperature of the strand after cooling (i.e., the temperature of the strand at the time of cutting) is preferably 35 to 200°C, more preferably 50 to 150°C, and even more preferably 70 to 120°C. If the temperature of the strand after cooling is equal to or higher than the lower limit of the above range, the elastic modulus of the strand does not become too high, the load on the pelletizer is reduced, and equipment failures such as damage to the strand cutter bearings are suppressed. If the temperature of the strand after cooling is equal to or lower than the upper limit of the above range, the elastic modulus of the strand does not become too low, and the strand can be easily cut by the pelletizer.

[0055] A pelletizer cuts the strand into pellets. A pelletizer typically includes a strand cutter, which cuts the cooled strand into pellets. The strand cutter includes, for example, a fixed blade and a rotary blade. The strand is sandwiched between the fixed blade and the rotary blade to be cut to a predetermined length, thereby obtaining pellets.

[0056] The rotary blade is preferably one having a length in the central axis direction of 80 to 550 mm and a diameter of 160 to 360 mm. The number of blades provided on the rotary blade is not particularly limited, as long as it is plural. Examples of materials for the blades provided on the rotary blade include WC-Co alloys, TiN-Ni alloys, TiCNi alloys, and alloys containing Fe as a main component. The rotation speed of the pelletizer is preferably 2,000 rpm or less, more preferably less than 1,000 rpm. The lower limit is preferably 100 rpm or more, more preferably 500 rpm or more. When the rotation speed of the pelletizer is within the above range, it is easy to adjust the specific surface area of ​​the resulting pellets to a predetermined range. Furthermore, the take-up speed of the strand is preferably 15 to 40 m / min, more preferably 20 to 30 m / min.

[0057] [Molded Article] The molded article of the present invention is obtained by molding the above-mentioned pellets. Since the molded article contains the copolymer in the pellets, it has excellent tensile strength after an acid resistance test, tensile strength after a heat aging test, and tensile elongation after a heat aging test. Specific molding methods include injection molding, extrusion molding, blow molding, press molding, rotational molding, and electrostatic coating. The molded article is preferably molded by press molding. Injection molding is also preferred because it can produce an injection-molded article with a beautiful appearance without corroding the mold used for molding.

[0058] Specific examples of the molded article of the present invention include nuts, bolts, joints, films, bottles, gaskets, wire coatings, 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] The pellets of the present invention or the molded article of the present invention 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, 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, 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 joints, 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.Among these, the molded article of the present invention is particularly suitable for use as a chemical liquid transport member and a coating material for semiconductor devices, because it is excellent in terms of the amount of undissolved pellets, heat resistance, acid resistance, folding resistance and high-speed wire forming ability.

[0060] The present invention will be described in detail below with reference to examples. Examples 1 to 15 are working examples, and Examples 16 to 22 are comparative examples. However, the present invention is not limited to these examples. Various measurement methods and evaluation methods are as follows.

[0061] [Measurement] <Measurement of pellets> The height, minor axis and major axis of 10 pellets obtained in each example were measured with a vernier caliper, and the arithmetic mean values ​​of these measurements were used to calculate the height L and minor axis D of the pellets. １ and major diameter D ２ In addition, using the obtained values, D １ ×D ２ , and specific surface area were calculated.

[0062] <Proportion of Each Unit> The content (mol %) of each unit in the copolymer is １９ The content (mol %) of E units in the copolymer was calculated by F-NMR measurement. １ H and １３ Calculated by C-NMR measurement.

[0063] <MFR> Using a melt indexer (manufactured by Techno Seven Co., Ltd.), the mass (g) of pellets 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 297°C and a load of 49 N in accordance with ASTM D3159, and this was taken as the MFR (g / 10 min).

[0064] <Melting Point> The melting point (°C) of the pellets 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).

[0065] [Evaluation Tests] <Method for Producing Resin Powder> Using the pellets obtained in each example, a resin powder was obtained according to the procedure described in paragraph

[0123] of WO 2016 / 017801.

[0066] <Film Forming> The pellets obtained in each example were press-molded at a temperature in the range of the melting point of the copolymer + 50°C ± 20°C (for example, 280 to 320°C when the melting point of the copolymer is 250°C) to obtain films with thicknesses of 200 μm, 0.23 mm, 1 mm, and 5 mm. The press-molding was carried out using a heated press ("SA-301" manufactured by Tester Sangyo Co., Ltd.).

[0067] <Remaining pellets during pressing> The 5 mm thick film obtained above was visually inspected for remaining pellets.

[0068] (Evaluation criteria for unmelted pellets during pressing) A: No unmelted pellets were found. B: Unmelted pellets were found.

[0069] <Heat Resistance> A dumbbell-shaped test piece defined in JIS K6301 No. 3 was cut out from the 1 mm thick film obtained above. The obtained test piece was pulled using a Strograph (manufactured by Toyo Seiki Seisaku-Sho, Ltd.) under conditions of a gauge length of 20 mm and a pulling speed of 200 mm / min in a constant temperature and humidity environment controlled at a temperature of 23±2°C and a humidity of 50%±10%, to measure the tensile strength (unit: %) before the heat aging test.

[0070] The above test pieces were placed in a gear oven (forced circulation air heating aging tester) (manufactured by Toyo Seiki Seisakusho, Ltd.) and subjected to a heat exposure treatment. The heat exposure treatment was performed at a temperature of 250°C, and the heat treatment was performed for 48 hours after placement. The heat-treated test pieces were subjected to a tensile test according to the above method, and the tensile strength (unit: %) after the heat aging test was measured. From the obtained results, the rate of change in tensile strength before and after the heat aging test (unit: %, tensile strength after heat aging test / tensile strength before heat aging test × 100) was calculated. From the calculated rate of change, the heat resistance of each pellet was evaluated based on the following evaluation criteria. A higher retention rate indicates better heat resistance.

[0071] (Evaluation criteria for heat resistance) A: The rate of change in tensile strength before and after the heat aging test is 40% or more. B: The rate of change in tensile strength before and after the heat aging test is less than 40%.

[0072] <Acid resistance of coating film> A SUS304 stainless steel plate measuring 50 mm in length, 150 mm in width, and 2 mm in thickness was baked at 400°C for 1 hour, and then its surface was sandblasted using alumina particles ("White Fused Alumina 50A (trade name)" manufactured by Pacific Random Co., Ltd.), and the blasted powder was removed with an air gun to obtain a substrate (1). The resin powder obtained in each example was electrostatically coated on the surface of the substrate (1), and the substrate was placed in an oven and baked at 275°C for 15 minutes. The coating step and the baking step were each performed four times, yielding a coated article in which a coating film layer made of powder and having a thickness of about 250 µm was formed on the substrate (1).

[0073] The resulting coated article (50 mm long, 150 mm wide) was used as a test piece to evaluate the adhesion between the substrate and the coating layer of the coated article using the following method. The coating layer was peeled from one lateral end of the test piece. The lateral length of the peeled portion of the coating layer was 10 mm. When peeling the coating layer, a cutter knife was used to make it easier to peel. The coating layer at the portion peeled from the substrate was fixed to the chuck of a tensile tester and pulled at a pulling rate of 50 mm / min, performing a 90-degree peel test. Peeling was performed from the one end of the test piece to a position 50 mm wide. The above measurement was performed three times, and the maximum load at 90-degree peeling was determined for each measurement. The average value was taken as the peel strength (unit: N / cm) before immersion in hydrochloric acid. The higher the peel strength, the better the adhesion. Furthermore, the coated article was immersed in 35% by mass hydrochloric acid at room temperature (23°C) for 24 hours, and then the above-mentioned 90-degree peel test was performed to determine the peel strength after hydrochloric acid immersion. Measurements after hydrochloric acid immersion were also performed three times, and the maximum load at 90-degree peeling in each measurement was determined. The average value was taken as the peel strength after hydrochloric acid immersion (unit: N / cm). From the obtained results, the rate of change in peel strength before and after hydrochloric acid immersion (unit: %, peel strength after hydrochloric acid immersion / peel strength before hydrochloric acid immersion × 100) was calculated. The acid resistance of the coating film was evaluated from the calculated rate of change based on the following evaluation criteria. A higher retention rate indicates better acid resistance of the coating film.

[0074] (Evaluation Criteria for Acid Resistance) A: The change in peel strength before and after immersion in hydrochloric acid is 23% or more. B: The retention of peel strength before and after immersion in hydrochloric acid is less than 23%.

[0075] <Folding Endurance> A folding fatigue test was carried out according to the MIT testing machine method, which is known as a method for evaluating stress crack resistance, in accordance with ASTM D2176. First, a rectangular test piece having a width of 12.5 mm and a length of 130 mm was cut out from the obtained film having a thickness of 0.23 mm. The obtained test piece was mounted on an MIT folding fatigue tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the test piece was bent under conditions of a load of 1.25 kg, a left and right bending angle of 135 degrees each, and a bending frequency of 175 times / min, and the number of times the test piece was bent until it broke (folding endurance) was measured. The folding endurance of each film was evaluated based on the measured folding endurance number according to the following evaluation criteria. A higher number of folding endurance numbers indicates better folding endurance.

[0076] (Evaluation criteria for folding endurance) A: Number of folding times is 40,000 or more B: Number of folding times is less than 40,000

[0077] <High-Speed ​​Wire Formability> An orifice with a diameter of 1 mm and a length of 10 mm was set in a melt flowability measuring device "Capilograph (registered trademark)" (manufactured by Toyo Seiki Seisakusho, Ltd.), and the temperature of the cylinder of the measuring device was set to 320°C. The pellets obtained in each example were filled into the cylinder of the measuring device and melted. The molten copolymer was extruded at a piston speed of 10 mm / min, and a strand extruded from the orifice was taken up using a roller. The take-up speed was gradually increased from 5 m / min to 200 m / min, and the maximum melt tension measured until the strand was broken was defined as the maximum melt tension (mN), and the take-up speed at which the strand was broken was defined as the maximum take-up speed (m / min). It can be said that the higher the maximum take-up speed, the better the high-speed wire formability. Furthermore, the upper limit of the take-up speed condition is 200 m / min due to the specifications of the machine. When the maximum take-up speed is the same, it can be said that the lower the ratio of the maximum melt tension to the maximum take-up speed, the better the high-speed wire formability. From the measured maximum melt tension and maximum take-up speed, the high-speed wire formability of each copolymer was evaluated based on the following evaluation criteria.

[0078] (Evaluation criteria for high-speed wire formability) A: The maximum take-up speed is 200 m / min, and the ratio (maximum melt tension / maximum take-up speed) is less than 0.08. B: The maximum take-up speed is less than 200 m / min, or the ratio (maximum melt tension / maximum take-up speed) is 0.08 or more.

[0079] [Example 1] Fluorine-based organic solvent (manufactured by AGC Inc., "ASAHIKLIN (registered trademark) AE-3000", CF ３ CH ２ OCF ２ CF ２ H) 1,167g and CH ２ =CH(CF ２ ) ４ 1.03 g of F(PFBE) and 11.9 g of methanol were charged into a pre-degassed polymerization vessel with an internal volume of 1.2 L and equipped with a stirrer. The solution in this polymerization vessel was heated to 72°C (polymerization temperature), and 180 g of a mixed gas of TFE / ethylene = 88 / 12 (molar ratio) was further charged, and then the pressure in the polymerization vessel was increased to 1.5 MPa [gauge]. Initially, 2.0 mL of a polymerization initiator solution in which tert-butyl peroxypivalate (PBPV) was dissolved in AE-3000 at a concentration of 1% by mass was charged, and polymerization was carried out. In addition, a mixed gas of TFE / ethylene = 54 / 46 (molar ratio) was continuously charged so that the pressure in the polymerization vessel during the polymerization reaction was maintained at 1.5 MPa [gauge]. In addition, PFBE in an amount corresponding to 0.60 mol% relative to the total moles of TFE, ethylene and PFBE charged during polymerization was continuously charged. When the amount of TFE / ethylene introduced reached 90 g, polymerization was terminated, the polymerization vessel was cooled, residual gas was purged, and polymerization was terminated. The same volume of water was added to the slurry in the polymerization vessel, and the mixture was heated with stirring to remove the solvent and unreacted monomers, and then heated and dried to obtain copolymer 1.

[0080] Next, the copolymer was fed into the raw material supply port of the twin-screw extruder and melt-kneaded (kneading conditions: cylinder temperature 280-300°C, die temperature 300). The resulting melt was then extruded from the die head to form a strand. The strand was then water-cooled in a cooling water tank and cut with a pelletizer to obtain pellets 1. The various conditions were as shown in the table. The specific equipment is as follows: As the twin-screw extruder, a fully intermeshing co-rotating twin-screw extruder (φ32, manufactured by Technovel Co., Ltd., KZW32T W) was used (ratio L / D of the overall screw length L to the barrel inner diameter D: 45, barrel inner diameter D: 32 mm, minimum tip clearance h in the kneading element: 0.267 mm, number of barrel blocks: 8, vacuum vent (vacuum degassing device): water-sealed vacuum pump (manufactured by Shinko Seiki Co., Ltd., SW-25AS, maximum exhaust speed: 450 L / min), strand die head: manufactured by Technovel Co., Ltd., STD321 (diameter of discharge port in die: 4 mm, number of discharge ports: 4). In addition, Technovel Co., Ltd.'s SCB250-2000 (width: 250 mm × depth: 250 mm × length: 2000 mm) was prepared as a cooling water tank. Technovel Co., Ltd.'s SCP-302 (diameter of rotary blade: 100 mm, length in the central axis direction of rotary blade: 100 mm, number of blades provided on rotary blade: 10) was used as a pelletizer.

[0081] The composition of Copolymer 1 was TFE unit / E unit / A unit (molar ratio) = 53.60 / 45.80 / 0.60. The MFR of Pellet 1 was 18 g / 10 min and the melting point was 268°C.

[0082] [Example 2] The amount of PFBE initially charged into the polymerization vessel was changed to 3.0 g, the amount of methanol to 7.9 g, the amount of polymerization initiator solution initially charged to 3.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.00 mol% relative to the total moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 2 of Example 2 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 2 of Example 2 was obtained in the same manner as in Example 1. The composition of copolymer 2 was TFE unit / E unit / A unit (molar ratio) = 53.30 / 45.70 / 1.00. The MFR of pellet 2 was 6 g / 10 min, and the melting point was 264 ° C.

[0083] [Example 3] The amount of PFBE initially charged into the polymerization vessel was changed to 3.0 g, the amount of methanol to 11.7 g, the amount of polymerization initiator solution initially charged was changed to 3.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.00 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 3 of Example 3 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 3 of Example 3 was obtained in the same manner as in Example 1. The composition of copolymer 3 was TFE unit / E unit / A unit (molar ratio) = 53.20 / 45.80 / 1.00. The MFR of pellet 3 was 17 g / 10 min, and the melting point was 264 ° C.

[0084] [Example 4] The amount of PFBE initially charged into the polymerization vessel was changed to 2.5 g, the amount of methanol to 15.9 g, the amount of polymerization initiator solution initially charged was changed to 3.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 0.90 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 4 of Example 4 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 4 of Example 4 was obtained in the same manner as in Example 1. The composition of copolymer 4 was TFE unit / E unit / A unit (molar ratio) = 53.80 / 45.30 / 0.90. The MFR of pellet 4 was 39 g / 10 min, and the melting point was 265 ° C.

[0085] [Example 5] The amount of PFBE initially charged into the polymerization vessel was changed to 4.9 g, the amount of methanol to 5.7 g, the amount of polymerization initiator solution initially charged to 5.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.40 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 5 of Example 5 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 5 of Example 5 was obtained in the same manner as in Example 1. The composition of copolymer 5 was TFE unit / E unit / A unit (molar ratio) = 53.80 / 44.80 / 1.40. The MFR of pellet 5 was 11 g / 10 min, and the melting point was 260 ° C.

[0086] [Example 6] The amount of PFBE initially charged into the polymerization vessel was changed to 5.9 g, the amount of methanol to 9.2 g, the amount of polymerization initiator solution initially charged was changed to 5.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.60 mol% relative to the total moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 6 of Example 6 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 6 of Example 6 was obtained in the same manner as in Example 1. The composition of copolymer 6 was TFE unit / E unit / A unit (molar ratio) = 53.80 / 44.60 / 1.60. The MFR of pellet 6 was 34 g / 10 min, and the melting point was 258 ° C.

[0087] [Example 7] The amount of PFBE initially charged into the polymerization vessel was changed to 7.8 g, the amount of methanol to 4.0 g, the amount of polymerization initiator solution initially charged to 6.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 2.00 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 7 of Example 7 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 7 of Example 7 was obtained in the same manner as in Example 1. The composition of copolymer 7 was TFE unit / E unit / A unit (molar ratio) = 53.40 / 44.60 / 2.00. The MFR of pellet 7 was 5 g / 10 min, and the melting point was 254 ° C.

[0088] [Example 8] The amount of PFBE initially charged into the polymerization vessel was changed to 7.8 g, the amount of methanol to 6.9 g, the amount of polymerization initiator solution initially charged was changed to 6.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 2.00 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 8 of Example 8 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 8 of Example 8 was obtained in the same manner as in Example 1. The composition of copolymer 8 was TFE unit / E unit / A unit (molar ratio) = 53.40 / 44.60 / 2.00. The MFR of pellet 8 was 24 g / 10 min, and the melting point was 254 ° C.

[0089] [Example 9] The amount of PFBE initially charged into the polymerization vessel was changed to 9.7 g, the amount of methanol to 5.6 g, the amount of polymerization initiator solution initially charged was changed to 8.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 2.40 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 9 of Example 9 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 9 of Example 9 was obtained in the same manner as in Example 1. The composition of copolymer 9 was TFE unit / E unit / A unit (molar ratio) = 53.40 / 44.20 / 2.40. The MFR of pellet 9 was 12 g / 10 min, and the melting point was 249 ° C.

[0090] [Example 10] The amount of PFBE initially charged into the polymerization vessel was changed to 12.6 g, the amount of methanol to 5.3 g, the amount of polymerization initiator solution initially charged was changed to 10.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 3.00 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 10 of Example 10 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 10 of Example 10 was obtained in the same manner as in Example 1. The composition of copolymer 10 was TFE unit / E unit / A unit (molar ratio) = 52.30 / 44.07 / 3.00. The MFR of pellet 10 was 10 g / 10 min, and the melting point was 243 ° C.

[0091] [Example 11] The amount of PFBE initially charged into the polymerization vessel was changed to 11.2 g, the amount of methanol to 7.0 g, the amount of polymerization initiator solution initially charged was changed to 10.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 2.70 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 11 of Example 11 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 11 of Example 11 was obtained in the same manner as in Example 1. The composition of copolymer 11 was TFE unit / E unit / A unit (molar ratio) = 52.80 / 44.50 / 2.70. The MFR of pellet 11 was 25 g / 10 min, and the melting point was 246 ° C.

[0092] [Example 12] The amount of PFBE initially charged into the polymerization vessel was changed to 17.5 g, the amount of methanol to 8.6 g, and the solution in the polymerization vessel was heated to 66 ° C (polymerization temperature), and 179 g of a mixed gas of TFE / ethylene = 90 / 10 (molar ratio) was further charged, and then the amount of polymerization initiator solution obtained by dissolving tert-butyl peroxypivalate in AE-3000 at a concentration of 2 mass% was changed to 16.0 mL initially, the mixed gas continuously charged during polymerization was changed to TFE / ethylene = 60 / 40 (molar ratio), the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 4.00 mol% with respect to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed to the amount shown in the table. Copolymer 12 of Example 12 was obtained in the same manner as in Example 1. Further, pellets 12 of Example 12 were obtained in the same manner as in Example 1, except for changing the production conditions shown in the table. The composition of copolymer 12 was TFE unit / E unit / A unit (molar ratio) = 56.80 / 39.20 / 4.00. The MFR of pellet 11 was 49 g / 10 min and the melting point was 233°C.

[0093] [Example 13] The amount of PFBE initially charged into the polymerization vessel was changed to 16.2 g, the amount of methanol to 4.0 g, and the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 3.60 mol% relative to the total moles of TFE, ethylene, and PFBE. Except for the polymerization time shown in the table, copolymer 13 of Example 13 was obtained in the same manner as in Example 12. Furthermore, except for the production conditions shown in the table, pellets 13 of Example 13 were obtained in the same manner as in Example 12. The composition of copolymer 13 was TFE unit / E unit / A unit (molar ratio) = 57.00 / 39.40 / 3.60. The MFR of pellets 13 was 12 g / 10 min, and the melting point was 230 ° C.

[0094] [Example 14] The amount of PFBE initially charged into the polymerization vessel was changed to 15.6 g, the amount of methanol to 4.8 g, the amount of polymerization initiator solution initially charged was changed to 13.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 3.50 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 14 of Example 14 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellets 14 of Example 14 were obtained in the same manner as in Example 12. The composition of copolymer 14 was TFE unit / E unit / A unit (molar ratio) = 57.10 / 39.40 / 3.50. The MFR of pellets 14 was 24 g / 10 min, and the melting point was 231 ° C.

[0095] [Example 15] The amount of PFBE initially charged into the polymerization vessel was changed to 15.6 g, the amount of methanol to 5.5 g, the amount of polymerization initiator solution initially charged was changed to 13.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 3.50 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 15 of Example 15 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellet 15 of Example 15 was obtained in the same manner as in Example 12. The composition of copolymer 15 was TFE unit / E unit / A unit (molar ratio) = 56.90 / 39.60 / 3.50. The MFR of pellet 15 was 42 g / 10 min, and the melting point was 231 ° C.

[0096] [Example 16] The amount of PFBE initially charged into the polymerization vessel was changed to 5.9 g, the amount of methanol to 7.2 g, the amount of polymerization initiator solution initially charged was changed to 5.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.60 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 16 of Example 16 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellets 16 of Example 16 were obtained in the same manner as in Example 1. The composition of copolymer 16 was TFE unit / E unit / A unit (molar ratio) = 53.60 / 44.80 / 1.60. The MFR of copolymer 16 was 19 g / 10 min, and the melting point was 258 ° C.

[0097] [Example 17] The amount of PFBE initially charged into the polymerization vessel was changed to 4.9 g, the amount of methanol to 5.7 g, the amount of polymerization initiator solution initially charged to 5.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 1.40 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 17 of Example 17 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellet 17 of Example 17 was obtained in the same manner as in Example 1. The composition of copolymer 17 was TFE unit / E unit / A unit (molar ratio) = 53.80 / 44.80 / 1.40. The MFR of pellet 17 was 11 g / 10 min, and the melting point was 260 ° C.

[0098] [Example 18] The amount of PFBE initially charged into the polymerization vessel was changed to 16.2 g, the amount of methanol to 4.6 g, the amount of polymerization initiator solution initially charged to 13.5 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 3.60 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 18 of Example 18 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellets 18 of Example 18 were obtained in the same manner as in Example 12. The composition of copolymer 18 was TFE unit / E unit / A unit (molar ratio) = 57.00 / 39.40 / 3.60. The MFR of pellets 18 was 12 g / 10 min, and the melting point was 230 ° C.

[0099] [Example 19] The amount of PFBE initially charged into the polymerization vessel was changed to 28.1 g, the amount of methanol to 4.0 g, the amount of polymerization initiator solution initially charged was changed to 13.5 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 5.50 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 19 of Example 19 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellet 19 of Example 19 was obtained in the same manner as in Example 12. The composition of copolymer 19 was TFE unit / E unit / A unit (molar ratio) = 56.80 / 37.70 / 5.50. The MFR of pellet 19 was 12 g / 10 min, and the melting point was 210 ° C.

[0100] [Example 20] The amount of PFBE initially charged into the polymerization vessel was changed to 0.07 g, the amount of methanol to 11.9 g, the amount of polymerization initiator solution initially charged to 2.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount equivalent to 0.40 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 20 of Example 20 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. Pellets 20 of Example 20 were obtained in the same manner as in Example 1. The composition of copolymer 20 was TFE unit / E unit / A unit (molar ratio) = 53.50 / 46.10 / 0.40. The MFR of pellet 19 was 18 g / 10 min, and the melting point was 270 ° C.

[0101] [Example 21] The amount of PFBE initially charged into the polymerization vessel was changed to 16.2 g, the amount of methanol to 6.0 g, the amount of polymerization initiator solution initially charged to 13.5 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 3.60 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 21 of Example 21 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellets 21 of Example 21 were obtained in the same manner as in Example 12. The composition of copolymer 21 was TFE unit / E unit / A unit (molar ratio) = 57.20 / 39.20 / 3.60. The MFR of pellets 21 was 65 g / 10 min, and the melting point was 230 ° C.

[0102] [Example 22] The amount of PFBE initially charged into the polymerization vessel was changed to 15.6 g, the amount of methanol to 0.2 g, the amount of polymerization initiator solution initially charged to 13.0 mL, the amount of PFBE continuously charged during polymerization was changed to an amount corresponding to 3.50 mol% relative to the total number of moles of TFE, ethylene, and PFBE, and the polymerization time was changed as shown in the table. Copolymer 22 of Example 22 was obtained in the same manner as in Example 12, except that the production conditions were changed as shown in the table. Pellets 22 of Example 22 were obtained in the same manner as in Example 12. The composition of copolymer 22 was TFE unit / E unit / A unit (molar ratio) = 57.30 / 39.20 / 3.50. The MFR of pellets 22 was 0.5 g / 10 min, and the melting point was 231 ° C.

[0103] The table below shows the composition of the copolymer of each example, as well as the measurement results and evaluation results. In the table, the "TFE units" column indicates the content (unit: mol%) of TFE units relative to all units contained in the copolymer. The "E units" column indicates the content (unit: mol%) of E units relative to all units contained in the copolymer. The "A units" column indicates the content (unit: mol%) of A units relative to all units contained in the copolymer. "MeOH" represents methanol. The "PFBE" column under "Additional Amount" indicates the amount of PFBE continuously added after the start of polymerization. The "Total PFBE Usage" column indicates the total amount of PFBE used in the polymerization reaction to obtain the copolymer. The "PFBE / AE-3000" column indicates the mass ratio of the total amount of PFBE used relative to the amount of AE-3000 used.

[0104]

[0105]

[0106] As shown in Tables 1 and 2, it was confirmed that the use of the pellets of the present invention resulted in molded articles with little residual pellets and excellent heat resistance, acid resistance, folding resistance, and high-speed wire moldability (Examples 1 to 15). The specific surface area of ​​the pellets tended to increase when the pelletizer rotation speed or strand take-up speed was increased, and tended to decrease when the resin feed rate was increased.

[0107] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2024-144370, filed on August 26, 2024, are incorporated herein by reference as part of the disclosure of the present invention.

[0108] 10 pellets

Claims

1. A cylindrical pellet comprising a copolymer having units based on tetrafluoroethylene, units based on ethylene, and units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2), wherein the total content of the units based on tetrafluoroethylene and the units based on ethylene is 80.00 to 99.50 mol% relative to the total units of the copolymer, the content of the units based on the specific compound is 0.50 to 5.00 mol% relative to the total units of the copolymer, the height L of the pellet is more than 2.00 mm, and the minor axis of the pellet is D １ mm, and the major diameter is D ２ mm, the relationship of formula (Z) is satisfied, and the specific surface area of ​​the pellet is 1,000 to 2,500 mm ２ / g, and the melt flow rate of the pellets is 1 to 50 g / 10 min, as measured in accordance with ASTM D3169 under conditions of a temperature of 297°C and a load of 49 N. １ ×D ２ ≦9.60 Formula (Z) CZ ２ =CX(CF ２ ) ｍ Y Formula (1) CF ２ =CF-O-(CF ２ ) ｎ F Formula (2) In formula (1), X, Y, and Z each independently represent a hydrogen atom or a fluorine atom, and m represents an integer of 2 to 6. Two Zs may be the same or different. In formula (2), n represents an integer of 1 to 6.

2. The pellet according to claim 1, wherein the copolymer is a copolymer consisting only of units based on tetrafluoroethylene, units based on ethylene, and units based on at least one specific compound selected from the group consisting of compounds represented by formula (1) and compounds represented by formula (2).

3. The pellet according to claim 1 or 2, wherein the specific compound is a compound represented by formula (1).

4. The pellet according to claim 1 or 2, wherein the content of units based on tetrafluoroethylene is 45.00 to 67.00 mol % based on the total units of the copolymer.

5. The pellet according to claim 1 or 2, wherein the content of units based on ethylene is 30.0 to 55.0 mol % based on the total units of the copolymer.

6. The pellet according to claim 1 or 2, wherein the melting point of the copolymer is 210°C to 290°C.

7. The method for producing pellets according to claim 1 or 2, wherein the copolymer is melt-kneaded in a twin-screw extruder, the resulting molten copolymer is extruded through a die of the twin-screw extruder, and strands containing the copolymer are cut by a pelletizer to obtain pellets containing the copolymer.

8. A molded article obtained by molding the pellets according to claim 1 or 2.

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