Method for producing perfluoroolefin and method for producing fluorine-containing polymer

Abstract

The present invention addresses the problem of providing: a method for producing a perfluoroolefin, the method being capable of efficiently producing a perfluoroolefin that contains tetrafluoroethylene and hexafluoropropylene through thermal decomposition; and a method for producing a fluorine-containing polymer.　The method for producing a perfluoroolefin is characterized by thermally decomposing a perfluoroalkyl iodide at 700 °C or higher to obtain a perfluoroolefin including tetrafluoroethylene and hexafluoropropylene, wherein the perfluoroalkyl group of the perfluoroalkyl iodide may further have an iodine atom.

Description

Method for producing perfluoroolefins, method for producing fluorine-containing polymers

[0001] The present invention relates to a method for producing perfluoroolefins and a method for producing fluorine-containing polymers.

[0002] Perfluoroolefins, particularly tetrafluoroethylene and hexafluoropropylene, are very useful as raw materials for fluorine-containing polymers. Patent Document 1 discloses a method for producing tetrafluoroethylene and hexafluoropropylene, which includes the thermal decomposition of low molecular weight fluorine compounds such as perfluoroalkenes by a continuous reaction in a microreactor.

[0003] Patent No. 7017982

[0004] Patent Document 1 describes a method for producing tetrafluoroethylene and hexafluoropropylene by thermal decomposition. However, there is a growing demand for a more efficient method for producing perfluoroolefins.

[0005] Therefore, the present invention aims to provide a method for producing perfluoroolefins containing tetrafluoroethylene and hexafluoropropylene more efficiently by thermal decomposition. Furthermore, the present invention aims to provide a method for producing fluorine-containing polymers.

[0006] As a result of diligent research into the above-mentioned problems, the present inventors discovered that perfluoroolefins containing tetrafluoroethylene and hexafluoropropylene can be produced more efficiently by thermally decomposing perfluoroalkyl iodide within a predetermined range of thermal decomposition temperatures, leading to the present invention.

[0007] In other words, the inventors have found that the above problems can be solved by the following configurations: [1] A method for producing a perfluoroolefin, characterized by thermally decomposing a perfluoroalkyl iodide at 700°C or higher to obtain a perfluoroolefin containing tetrafluoroethylene and hexafluoropropylene, wherein the perfluoroalkyl group in the perfluoroalkyl iodide may further contain an iodine atom. [2] The method for producing a perfluoroolefin according to [1], wherein the perfluoroalkyl iodide is thermally decomposed at 750°C or higher to obtain the perfluoroolefin. [3] The method for producing a perfluoroolefin according to [1] or [2], wherein the perfluoroalkyl iodide has one or two iodine atoms. [4] The method for producing a perfluoroolefin according to [1] or [2], wherein the perfluoroalkyl iodide is a compound represented by formula (1) described later. [5] The method for producing a perfluoroolefin according to any one of [1] to [4], wherein the thermal decomposition of the perfluoroalkyl iodide is carried out in an environment where the oxygen concentration is 10% by volume or less. [6] A method for producing a perfluoroolefin according to [1] to [5], wherein the perfluoroalkyl iodide is thermally decomposed at 1200°C or below. [7] A method for producing a fluorine-containing polymer, characterized by polymerizing a monomer containing at least one of tetrafluoroethylene and hexafluoropropylene contained in a perfluoroolefin produced by the method for producing a perfluoroolefin according to any one of [1] to [6] to obtain a fluorine-containing polymer.

[0008] According to the present invention, a method for producing perfluoroolefins containing tetrafluoroethylene and hexafluoropropylene can be provided, which allows for more efficient production by thermal decomposition. Furthermore, according to the present invention, a method for producing fluorine-containing polymers can be provided.

[0009] This is a schematic diagram showing an example of a manufacturing apparatus in which the manufacturing method of the present invention is carried out.

[0010] The meanings of terms used in this invention are as follows: A numerical range expressed using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. In this specification, each component may be made using one substance alone or two or more substances in combination. When two or more substances are used in combination for each component, the content for that component refers to the total content of the substances used in combination, unless otherwise specified. In this specification, combining two or more preferred embodiments is a more preferred embodiment.

[0011] [Method for Producing Perfluoroolefins] The method for producing perfluoroolefins according to the present invention (hereinafter also referred to as "this production method") is characterized by thermally decomposing perfluoroalkyl iodide (hereinafter also referred to as "PFAI") at 700°C or higher to obtain a perfluoroolefin containing tetrafluoroethylene (hereinafter also referred to as "TFE") and hexafluoropropylene (hereinafter also referred to as "HFP"). This production method will be described in more detail below.

[0012] <PFAI> The PFAI used in this manufacturing method is a compound obtained by substituting a fluorine atom of a perfluoroalkane with an iodine atom. Here, the perfluoroalkyl group of PFAI may further contain iodine atoms. In other words, the number of iodine atoms in PFAI may be one or two or more. PFAI preferably has one or two iodine atoms, and more preferably has one iodine atom. The number of carbon atoms in the perfluoroalkyl group of PFAI is, for example, 1 to 30, preferably 1 to 16, and more preferably 1 to 10. The perfluoroalkyl group may be linear or branched, and linear is preferred.

[0013] Among them, the compound represented by the following formula (1) is preferred as PFAI: X-(CF ２ CF ２ ) ｎ -I Equation (1) In Equation (1), X is F, I, CF ３ or CF ２Let I represent. n represents an integer of 2 or more.

[0014] As X, F, I or CF ３ is preferable, F or CF ３ is more preferable, and F is even more preferable. As n, an integer of 2 to 15 is preferable, an integer of 2 to 8 is more preferable, and an integer of 2 to 5 is even more preferable.

[0015] More specific PFAI includes C ６ F １３ I, C ８ F １７ I and C １０ F ２１ I are mentioned, C ６ F １３ I or C ８ F １７ I is preferable. In this production method, one kind of PFAI may be used as the raw material, or two or more kinds of PFAI may be used in combination.

[0016] PFAI can be obtained, for example, by the telomerization reaction of perfluoroalkyl iodide as a telogen and TFE. However, in the telomerization reaction, it is difficult to control the carbon number distribution. For example, for the purpose of obtaining PFAI with 4 carbon atoms, even if perfluoroethyl iodide (C ２ F ５ I) and TFE are reacted, PFAI with a wide molecular weight range of 2 to 20 carbon atoms is often generated.

[0017] According to this production method, not only low molecular weight PFAI but also PFAI with a large carbon number can be produced in a small number of steps of useful perfluoroolefins containing TFE and HFP by thermal decomposition reaction. Therefore, this production method is very useful not only in terms of excellent production efficiency of perfluoroolefins but also from the viewpoints of PFAI treatment and production cost.

[0018] PFAI is introduced into the reaction vessel described later as a raw material and is thermally decomposed. From the viewpoint of suppressing the generation of impurities other than the target product, perfluoroolefin, it is preferable that the amount of components other than the raw material PFAI and the inert gas described later introduced into the reaction vessel be small. For example, if the raw material contains a large amount of hydroxyfluoroalkyl iodide, which is formed by substituting at least one fluorine atom of PFAI with a hydrogen atom, thermal decomposition often produces fluoroolefins containing hydrogen atoms, which reduces the yield of TFE and / or HFP.

[0019] <Thermal Decomposition> This manufacturing method is characterized by thermal decomposition of PFAI at a temperature of 700°C or higher. From the viewpoint of further suppressing the formation of products other than perfluoroolefins, such as perfluorocarbons and various fluoroalkyl iodides, the thermal decomposition temperature is preferably 750°C or higher, and more preferably 780°C or higher. Furthermore, from the viewpoint of improving the yield of TFE and HFP, the thermal decomposition temperature is preferably 1200°C or lower, preferably 1000°C or lower, and more preferably 950°C or lower.

[0020] From the viewpoint of increasing the HFP content in the perfluoroolefin obtained by thermal decomposition, and more specifically, from the viewpoint of increasing the ratio of HFP content to the total content of HFP and TFE (hereinafter also referred to as "HFP selectivity"), a thermal decomposition temperature of 800°C or higher is preferable, and 830°C or higher is more preferable. One method of synthesizing HFP is the thermal decomposition of TFE. When HFP is the final target product, carrying out this production method at the above thermal decomposition temperature is advantageous because it yields a product with high HFP selectivity and allows for efficient production of HFP. When carrying out this production method at the above thermal decomposition temperature, in one embodiment, a product with an HFP yield of 40% by mass or more (more preferably 50% by mass or more) is obtained. Here, the HFP yield is the mass ratio of the amount of HFP produced by thermal decomposition to the total amount of carbon atoms and fluorine atoms contained in the raw materials supplied for thermal decomposition.

[0021] The reaction time in thermal decomposition is appropriately adjusted depending on the thermal decomposition temperature, but is, for example, 0.3 to 300 seconds, preferably 0.5 to 180 seconds, more preferably 0.8 to 90 seconds, and even more preferably 1.0 to 60 seconds. The reaction time is preferably above the lower limit from the viewpoint of reducing the content of undecomposed PFAI in the product, and preferably below the upper limit from the viewpoint of suppressing the decomposition of perfluoroolefins.

[0022] From the viewpoint of improving the yield of perfluoroolefins, thermal decomposition is preferably carried out in an environment with an oxygen concentration of 30% by volume or less, and more preferably in an environment with an oxygen concentration of 10% by volume or less. The oxygen concentration when carrying out thermal decomposition may be 0% by volume.

[0023] One method for reducing oxygen concentration is to fill the reaction vessel with an inert gas and perform thermal decomposition while the PFAI and inert gas are mixed. Examples of inert gases include nitrogen and H2. ２ Examples include oxygen (O) and noble gases (e.g., helium, neon, and argon), as well as nitrogen or H ２ O is preferred.

[0024] The thermal decomposition of PFAI may be carried out using either a batch reaction process or a continuous reaction process, but from the viewpoint of easy control of the reaction time, thermal decomposition using a continuous reaction process is preferred. A continuous reaction process means continuously supplying the raw materials containing PFAI to the reaction vessel for thermal decomposition and continuously removing the thermal decomposition product from the reaction vessel.

[0025] When PFAI is thermally decomposed in a continuous reaction process, the residence time of PFAI in the reaction vessel can be appropriately adjusted according to reaction conditions such as the thermal decomposition temperature, for example, 0.1 to 300 seconds. The residence time of PFAI in the reaction vessel refers to the time from when PFAI is introduced into the reaction vessel until the perfluoroolefin produced by the thermal decomposition of PFAI is discharged from the reaction vessel. When PFAI is thermally decomposed in a continuous reaction process, the flow rate of PFAI introduced into the reaction vessel can be appropriately adjusted according to reaction conditions such as the thermal decomposition temperature and the residence time of PFAI, for example, 0.01 to 100 g / min, with 0.05 to 50 g / min being preferred. When PFAI is thermally decomposed in a continuous reaction process, it is preferable to introduce an inert gas together with PFAI into the reaction vessel to adjust the concentration of PFAI, as this facilitates control of the residence time, flow rate, and linear velocity of PFAI in the reaction vessel, and thus facilitates control of the thermal decomposition behavior. When introducing an inert gas, the flow rate of the inert gas introduced into the reaction vessel should be, for example, 1 to 1000 mL / min, preferably 10 to 500 mL / min, when converted to conditions at room temperature (25°C) and atmospheric pressure (1 atm).

[0026] The product obtained after thermal decomposition of PFAI may be cooled. Cooling the product can stop side reactions or suppress product decomposition, thereby improving selectivity. One method of cooling the product is to cool it by contacting it with a quenching solution such as an aqueous KOH solution.

[0027] The reaction vessel used for the thermal decomposition of PFAI can be appropriately selected according to the reaction process, more specifically, the thermal decomposition temperature, reaction time, and the flow rates of the raw materials and inert gas. When thermally decomposing PFAI in a continuous reaction process, for example, a reaction vessel with a short width dimension perpendicular to the direction of movement relative to the direction of movement of the raw materials and products can be used. As such a reaction vessel, for example, a reaction vessel with a diameter (or flow path width) of 1 μm or more and 20 mm or less, preferably 1 to 20 mm, and a length of 20 to 200 cm, preferably 30 to 100 cm, can be used.

[0028] FIG. 1 is a schematic diagram showing an example of a manufacturing apparatus in which the present manufacturing method is implemented. The manufacturing apparatus 100 shown in FIG. 1 includes a preheater 10, a reaction vessel 20, a heating furnace 22, an iodine trap 30, a recovery vessel 40, and lines L1 to L5. In the manufacturing apparatus 100, a raw material containing PFAI is supplied from a raw material container (not shown) to the reaction vessel 20 via line L1. An inert gas is supplied from a gas tank (not shown) to line L1 via line L2 and mixed with the raw material. While the mixed gas of the raw material and the inert gas is being transferred in line L1, it is heated by the preheater 10 to a predetermined temperature (for example, the temperature at which PFAI vaporizes). Note that the confluence position of line L1 and line L2 may be between the preheater 10 and the reaction vessel 20. That is, each of the raw material and the inert gas may be heated by the preheater 10 and then mixed, and the mixed gas may be introduced into the reaction vessel 20.

[0029] The reaction vessel 20 is installed in a heating furnace 22 (for example, an electric furnace) and is heated by the heating furnace 22. The PFAI introduced into the reaction vessel 20 is pyrolyzed while flowing together with the inert gas in the reaction vessel 20, whereby a pyrolysis product containing TFE, HFP, and iodine (I ２ ) is obtained. The pyrolysis product and the inert gas are supplied to the iodine trap 30 via line L3 connected to the reaction vessel 20. In the iodine trap 30, iodine generated by the pyrolysis of PFAI is recovered. As the iodine trap 30, a known iodine recovery device can be used. The pyrolysis products other than iodine and the inert gas are supplied to the recovery vessel 40 via line L4 connected to the iodine trap 30. In the recovery vessel 40, perfluoroolefins containing TFE and HFP are recovered, and the inert gas is discharged from the recovery vessel 40 via line L5.

[0030] In this way, the perfluoroolefins containing TFE and HFP obtained by the thermal decomposition of PFAI are recovered in the recovery vessel 40. TFE, HFP, and other perfluoroolefins can be easily separated by subjecting the recovered perfluoroolefin product to known purification processes (e.g., separation processes utilizing differences in boiling points). The separated TFE and HFP can be used, respectively, in the production of fluorine-containing polymers.

[0031] In this production method, the iodine contained in PFAI can be recovered and recycled. This is because, since the thermal decomposition temperature is 700 °C or higher, the iodine radicals generated by thermal decomposition do not recombine with other radicals but are desorbed to generate iodine. The forms of iodine recovered include solid I ２ , solutions containing I ２ (e.g., aqueous solutions), iodine compounds such as KI, and solutions of iodine compounds (e.g., aqueous solutions), etc. The recovered iodine is a useful substance as a raw material for various chemical reactions including the synthesis of PFAI, and is also an important substance as a raw material and intermediate for various products such as pharmaceuticals, industrial products, and agricultural chemicals.

[0032] [Method for Producing Fluorine-Containing Polymer] The perfluoroolefins produced by this production method, particularly TFE and HFP, are suitably used in the production of fluorine-containing polymers. As one embodiment of the method for producing a fluorine-containing polymer, there is a method of polymerizing a monomer containing at least one of TFE and HFP contained in the perfluoroolefin produced by this production method to produce a fluorine-containing polymer.

[0033] In the polymerization step of this production method, examples of the polymerization method for polymerizing the monomer include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among them, solution polymerization is preferred. The amounts of TFE, HFP, and other monomers used in the polymerization are appropriately adjusted according to the composition of the target fluorine-containing polymer. In the polymerization step, in addition to the above monomers, polymerization initiators, polymerization media, chain transfer agents, etc. can be used.

[0034] The polymerization initiator is preferably a radical polymerization initiator with a half-life of 10 hours at a temperature of 0 to 100°C, and more preferably a radical polymerization initiator at a temperature of 20 to 90°C. Specific examples of polymerization initiators include the various polymerization initiators exemplified in International Publication No. 2013 / 015202. The polymerization initiator may be used alone or in combination of two or more. The amount of polymerization initiator used is preferably 0.01 to 0.9 parts by mass, and particularly preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of monomer used.

[0035] The polymerization medium can be perfluorocarbon, hydrofluorocarbon, hydrofluoroether, etc. Specific examples of polymerization mediums include those exemplified in International Publication No. 2013 / 015202. The polymerization medium may be used alone or in combination of two or more types. The amount of polymerization medium used is preferably 5 times or more by mass relative to the amount of monomer used, more preferably 7 times or more. It is also preferably 20 times or less, and more preferably 17 times or less.

[0036] Chain transfer agents include 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, due to their large chain transfer constants and the fact that they require small amounts of addition; hydrocarbons such as n-pentane, n-hexane, and cyclohexane; and CF ２ H ２Hydrofluorocarbons such as acetone; ketones such as methyl mercaptan; esters such as methyl acetate and ethyl acetate; ethers such as diethyl ether and methyl ethyl ether; etc. are preferred. Among these, at least one selected from the group consisting of alcohols, hydrocarbons and hydrofluorocarbons is preferred, at least one selected from the group consisting of alcohols and hydrocarbons is more preferred, and alcohols are particularly preferred, due to their higher chain transfer constant and high stability of the terminal groups of the fluorine-containing polymer. Among alcohols, methanol or ethanol is particularly preferred. Among these, methanol is particularly preferred due to its reactivity and availability. Two or more chain transfer agents may be used. The amount of chain transfer agent used is preferably 0.001 times or more by mass ratio to the amount of monomer used, more preferably 0.005 times or more. Also, 5 times or less is preferred, and 4 times or less is more preferred.

[0037] The polymerization temperature is preferably 15 to 60°C, more preferably 20 to 58°C, and particularly preferably 25 to 55°C. Polymerizability is excellent when the polymerization temperature is 25°C or higher. The melting point of the fluorine-containing polymer can be improved when the polymerization temperature is 60°C or lower. The polymerization pressure is preferably 0.5 to 3.0 MPa, and particularly preferably 0.9 to 2.5 MPa. The polymerization time is preferably 1 to 12 hours.

[0038] <Applications of Fluorine-Containing Polymers> Fluorine-containing polymers are preferably used in the manufacture of various molded articles. Specific examples of molding methods for manufacturing molded articles include injection molding, extrusion molding, blow molding, press molding, rotational molding, and electrostatic coating. As a method for manufacturing molded articles, fluorine-containing polymers may be molded, or compositions containing fluorine-containing polymers may be molded.

[0039] Specific examples of molded products include nuts, bolts, fittings, films, bottles, gaskets, wire insulation, tubes, hoses, pipes, valves, seats, seals, packings, tanks, rollers, containers, cocks, connectors, filter housings, filter cages, flow meters, pumps, wafer carriers, and wafer boxes.

[0040] Fluorine-containing polymers, compositions containing fluorine-containing polymers, or molded articles thereof can be used for the following purposes. Fluid transfer components for food manufacturing equipment, such as food packaging films, lining materials for fluid transfer lines used in food manufacturing processes, packings, seals, and sheets; chemical liquid transfer components for pharmaceuticals, such as chemical stoppers, packaging films, lining materials for fluid transfer lines used in pharmaceutical manufacturing processes, packings, seals, and sheets; internal lining components for chemical tanks and piping in chemical plants or semiconductor factories; fuel transfer components such as O-rings, square rings, tubes, packings, valve cores, hoses, and seals used in automobile fuel systems and peripheral equipment, as well as hoses and seals used in automobile automatic transmission systems; carburetor flange gaskets, shaft seals, valve stem seals, seals, and hoses used in automobile engines and peripheral equipment, as well as other automobile components such as brake hoses, air conditioning hoses, radiator hoses, and wire insulation materials; chemical liquid transfer components for semiconductor equipment, such as O-rings, square rings, tubes, packings, valve cores, hoses, seals, rolls, gaskets, diaphragms, and fittings used in semiconductor manufacturing equipment; Painting and ink components such as paint rolls, hoses, tubes, and ink containers for painting equipment; food transport components such as tubes or hoses for food and beverages, hoses, belts, gaskets, and fittings, food packaging materials, and glass cooking equipment; waste liquid transport components such as tubes and hoses for waste liquid transport; high-temperature liquid transport components such as tubes and hoses for high-temperature liquid transport; steam piping components such as tubes and hoses for steam piping; corrosion-resistant tapes for piping such as tapes wrapped around piping on ship decks, etc.; various coating materials such as wire coatings, optical fiber coatings, transparent surface coatings and backings provided on the light incident side surface of photovoltaic elements of solar cells; sliding components such as diaphragms and various gaskets for diaphragm pumps; agricultural films, fuel cell carrier films, and weather-resistant covers for various roofing materials and side walls, etc.; interior materials used in the building sector, and coating materials for glass such as non-combustible fire-resistant safety glass; lining materials such as laminated steel sheets used in the home appliance sector, etc.

[0041] The present invention will be described in detail below with reference to examples. Examples 1 to 5 and 9 are examples, and Examples 6 to 8 are comparative examples. However, the present invention is not limited to these examples.

[0042] [Example 1] The thermal decomposition of a raw material containing PFAI was carried out using the manufacturing apparatus shown in Figure 1. A quartz tube with an inner diameter of 6 mm and a length of 40 cm was placed in an electric furnace and heated to 850°C. The preheater was heated to 200°C. C as the raw material ８ F １７ I and N ２ After heating the gas in a preheater, it was continuously supplied to a quartz tube at flow rates of 0.1 g / min and 50 mL / min, respectively, for 20 minutes to carry out a thermal decomposition reaction at a temperature of 850°C. The oxygen concentration inside the quartz tube during the thermal decomposition was less than 1 volume percent. Of the thermal decomposition products obtained from the reaction, iodine was recovered as a solid using an iodine trap, while the thermal decomposition products other than iodine, including TFE and HFP, were recovered as gases.

[0043] [Examples 2-8] The thermal decomposition reaction of the raw materials was carried out in the same manner as in Example 1, except that the heating of the quartz tube in the electric furnace was adjusted and the thermal decomposition reaction was carried out at the thermal decomposition temperature (°C) listed in Table 1 below, and / or the compounds listed in the table below were used as raw materials, and the thermal decomposition products were recovered.

[0044] [Example 9] N used in Example 1 ２ H is heated and vaporized instead of being used as a gas. ２ The thermal decomposition reaction of the raw materials was carried out in the same manner as in Example 1, except that oxygen was used. Iodine and H ２ O was recovered using an iodine trap, and the pyrolysis products, including TFE and HFP, were recovered as gases.

[0045] [Measurement of Yield] The pyrolysis products obtained in each example were analyzed by gas chromatography (GC) (product name "7890B", manufactured by Agilent Technologies), and the yields (mass g) of TFE and HFP were measured. The yields (mass %) of TFE and HFP in the pyrolysis reaction of each example were calculated by dividing the obtained TFE and HFP yields (mass g) by the total amount (mass g) of carbon atoms and fluorine atoms contained in the supplied raw materials. In addition, the yield (mass g) of iodine recovered in each example was measured by titration. The yield (mass %) of iodine in the pyrolysis reaction of each example was calculated by dividing the obtained iodine yield (mass g) by the iodine atom content (mass g) in the supplied raw materials. The GC analysis above confirmed that in Examples 1 to 5, perfluoroolefins with 4 or more carbon atoms were produced in a yield range of 0.5 to 10 mass %.

[0046] Table 1 shows the raw materials used in the thermal decomposition reaction for each example, the thermal decomposition temperature (°C), and the yields (mass%) of TFE, HFP, and iodine, respectively.

[0047]

[0048] As shown in Table 1, the method for producing perfluoroolefins of the present invention, which involves thermally decomposing perfluoroalkyl iodide at 700°C or higher to obtain perfluoroolefins containing tetrafluoroethylene and hexafluoropropylene, was confirmed to be a method that can efficiently produce perfluoroolefins containing TFE and HFP, with a high total yield of TFE and HFP (Examples 1 to 5 and 9).

[0049] [Production of Fluorine-Containing Polymer] The product gas containing the pyrolysis product obtained in Example 9 was neutralized with an aqueous KOH solution, and then dehydrated with molecular sieves 4A to obtain a purified gas. Referring to Example 9 of International Publication No. 2020 / 196779, the HFP and TFE contained in the purified gas were reacted to obtain a fluorine-containing polymer. It was confirmed that the obtained fluorine-containing polymer was a copolymer of HFP and TFE.

[0050] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-189650, filed on October 29, 2024, are incorporated herein by reference as the disclosure of the present invention.

[0051] L1, L2, L3, L4, L5 lines 10 Preheaters 20 Reaction vessels 22 Furnaces 30 Iodine traps 40 Recovery containers 100 Manufacturing equipment

Claims

1. A method for producing a perfluoroolefin, characterized by thermally decomposing a perfluoroalkyl iodide at 700°C or higher to obtain a perfluoroolefin containing tetrafluoroethylene and hexafluoropropylene, wherein the perfluoroalkyl group in the perfluoroalkyl iodide may further contain an iodine atom.

2. The method for producing the perfluoroolefin according to claim 1, wherein the perfluoroalkyl iodide is thermally decomposed at 750°C or higher to obtain the perfluoroolefin.

3. The method for producing a perfluoroolefin according to claim 1, wherein the perfluoroalkyl iodide has one or two iodine atoms.

4. A method for producing a perfluoroolefin according to claim 1 or 2, wherein the perfluoroalkyl iodide is a compound represented by the following formula (1): X-(CF ２ CF ２ ) ｎ -I Equation (1) In Equation (1), X is F, I, CF ３ or CF ２ I represents n, and n represents an integer greater than or equal to 2.

5. The method for producing a perfluoroolefin according to claim 1 or 2, wherein the thermal decomposition of the perfluoroalkyl iodide is carried out in an environment with an oxygen concentration of 10% by volume or less.

6. A method for producing a perfluoroolefin according to claim 1 or 2, wherein the perfluoroalkyl iodide is thermally decomposed at 1200°C or below.

7. A method for producing a fluorine-containing polymer, characterized by polymerizing a monomer containing at least one of tetrafluoroethylene and hexafluoropropylene contained in a perfluoroolefin produced by the method for producing a perfluoroolefin according to claim 1 or 2, to obtain a fluorine-containing polymer.

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