Storage methods for fluoroolefins

Abstract

This invention provides a method for storing fluoroolefins that are less prone to reaction during storage and whose purity is not easily reduced, even without the addition of a stabilizer to inhibit the reaction of fluoroolefins. The fluoroolefin having bromine or iodine atoms within its molecule is at least one of vinyl fluorocarbon represented by the first general formula C₂H₁pF₂qXᵀr and fluoropropylene represented by the second general formula C₃H₂sF₂tXᵀ (X represents a bromine or iodine atom), and may or may not contain at least one of manganese, cobalt, nickel, and silicon as metallic impurities. When the fluoroolefin contains the aforementioned elements, the sum of the concentrations of manganese, cobalt, nickel, and silicon is set to below 1000 ppb by mass before storage in a container.

Description

Technical Field

[0001] This invention relates to a method for preserving fluoroolefins. Prior Technology

[0002] Fluoroolefins containing bromine or iodine atoms (e.g., 2-bromo-3,3,3-trifluoropropene) can be used as digesters or etching gases for dry etching (see, for example, Patent Documents 1 and 2). Furthermore, when referred to as "fluoroolefin" in this specification, it means "fluoroolefin containing bromine or iodine atoms." [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Publication No. 534840, 2014 [Patent Document 2] Japanese Patent Publication No. 190311, 2017 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] However, fluoroolefins are unstable compounds and are prone to decomposition reactions or the removal of bromine or iodine atoms, which may reduce their purity. While adding stabilizers such as antioxidants and water can inhibit the reactions of fluoroolefins, the addition of stabilizers also leads to a decrease in the purity of the fluoroolefins. The objective of this invention is to provide a method for preserving fluoroolefins that are less prone to fluoroolefin reactions and whose purity is less likely to decrease even without the addition of stabilizers to inhibit the reaction of fluoroolefins. [Methods used to solve problems]

[0006] In order to solve the aforementioned problems, one aspect of the present invention is as follows [1] to [5]. [1] A method for preserving fluoroolefins, which is a method for preserving fluoroolefins having bromine or iodine atoms in the molecule. The aforementioned fluoroolefins are at least one of fluoroethylene represented by the first general formula C2HpFqXr and fluoropropylene represented by the second general formula C3HsFtXu; In the aforementioned first general formula, X represents a bromine atom or an iodine atom, p is an integer greater than or equal to 0 and less than 2, q is an integer greater than or equal to 1 and less than 3, r is an integer greater than or equal to 1 and less than 3, and p+q+r equals 4; In the aforementioned second general formula, X represents a bromine atom or an iodine atom, s is an integer between 0 and 4, t is an integer between 1 and 5, u is an integer between 1 and 5, and s+t+u equals 6. The aforementioned fluoroolefin may or may not contain at least one of manganese, cobalt, nickel and silicon as metallic impurities. The sum of the concentrations of manganese, cobalt, nickel and silicon when the aforementioned fluoroolefin is present is set to be less than 1000 ppb by mass, and the aforementioned fluoroolefin is stored in a container.

[0007] [2] The method for storing fluoroolefins as described in [1], wherein the aforementioned fluoroolefin may contain or not contain at least one of sodium, potassium, magnesium and calcium as the aforementioned metallic impurities, and the total concentration of manganese, cobalt, nickel and silicon, as well as sodium, potassium, magnesium and calcium, when the aforementioned fluoroolefins are present, is set to less than 2000 ppb by mass, and the aforementioned fluoroolefins are stored in a container.

[0008] [3] The method of preserving fluoroolefins as in [1] or [2], wherein the aforementioned fluoroolefin is selected from at least one of 1-bromo-1,2,2-trifluoroethylene, 1-bromo-1-fluoroethylene, 1-iodo-1,2,2-trifluoroethylene, 1-iodo-1-fluoroethylene, 2-bromo-3,3,3-trifluoropropene and 2-iodo-3,3,3-trifluoropropene. [4] The method of preserving fluoroolefins as described in any of [1] to [3], wherein the fluoroolefins are preserved at a temperature between -20°C and 50°C. [5] The method for preserving fluoroolefins as described in any of [1] to [4], wherein the aforementioned container is made of manganese steel. [Invention Effects]

[0009] According to the present invention, even without the addition of a stabilizer to inhibit the reaction of fluoroolefins, the reaction of fluoroolefins is not easily generated during storage, and the purity of fluoroolefins is not easily reduced. Implementation

[0010] The following describes one embodiment of the present invention. This embodiment is merely one example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and any such modifications or improvements may also be included in the present invention.

[0011] The preservation method of fluoroolefins in this embodiment is a preservation method for fluoroolefins having bromine or iodine atoms in the molecule. The fluoroolefin contains or does not contain at least one of manganese (Mn), cobalt (Co), nickel (Ni) and silicon (Si) as a metallic impurity. The sum of the concentrations of manganese, cobalt, nickel and silicon when the fluoroolefin contains the aforementioned elements is set to 1000 ppb or less by mass, and the fluoroolefin is preserved in a container.

[0012] The fluoroolefin is at least one of vinyl fluoride and propylene fluoride. Vinyl fluoride is a compound represented by the first general formula C₂H₁pF₂qX₂r, where X represents a bromine atom or an iodine atom, p is an integer from 0 to 2, q is an integer from 1 to 3, r is an integer from 1 to 3, and p+q+r equals 4. Propylene fluoride is a compound represented by the second general formula C₃H₁sF₂tX₂u, where X represents a bromine atom or an iodine atom, s is an integer from 0 to 4, t is an integer from 1 to 5, u is an integer from 1 to 5, and s+t+u equals 6.

[0013] When fluoroolefins contain at least one of manganese, cobalt, nickel, and silicon as metallic impurities, the metallic impurities catalyze reactions such as the decomposition of fluoroolefins and the release of bromine or iodine atoms from the fluoroolefin. Therefore, fluoroolefins containing metallic impurities are prone to generating decomposition products or bromine and iodine molecules during long-term storage, resulting in a decrease in purity.

[0014] The fluoroolefins preserved using the preservation method of this embodiment contain no or, if they do contain metal impurities, their content is very low. Therefore, even during long-term storage, it is not easy for the fluoroolefins to undergo decomposition reactions or reactions that cause bromine or iodine atoms to be released from the fluoroolefins. It is also not easy to generate decomposition products of fluoroolefins or bromine or iodine molecules. As a result, the purity of the fluoroolefins is not easily reduced, and high purity can be maintained for a long period of time.

[0015] Therefore, even without adding stabilizers such as antioxidants and water to the fluoroolefins, the fluoroolefins can still be stored stably for a long period. Furthermore, the purity of the fluoroolefins will not decrease due to the addition of stabilizers, nor will the quality of the fluoroolefins (e.g., as a digester or etching gas) decrease due to the addition of stabilizers. While stabilizers can be added to the fluoroolefins in the storage method of this embodiment, the preferred embodiment of the storage method of this embodiment does not involve adding stabilizers to the fluoroolefins.

[0016] The following provides a more detailed description of the method for preserving fluoroolefins according to this embodiment. [Fluoroolefins containing bromine or iodine atoms within their molecules] The fluoroolefin in the preservation method of this embodiment is at least one of vinyl fluoride represented by the first general formula C2HpFqXr and fluoropropylene represented by the second general formula C3HsFtXu. The type of fluoroolefin is not particularly limited as long as the above requirements are met, but it is preferred to be a fluoroolefin in the first general formula where r is 1 and a fluoroolefin in the second general formula where u is 1.

[0017] Specific examples of fluoroalkenes containing bromine atoms within their molecules include CFBr=CH₂ (1-bromo-1-fluoroethylene), CFBr=CHF, CFBr=CF₂ (1-bromo-1,2,2-trifluoroethylene), CFBr=CFBr, CFBr=CHBr, CF₂=CHBr, CHF=CHBr, CFBr=CBr₂, CF₂=CBr₂, CHF=CBr₂, CHBr=CBr₂, CH₂=CBrCF₃ (2-bromo-3,3,3-trifluoropropene), CHF=CBrCF₃, CHBr=CBrCF₃, CF₂=CBrCF₃, CBr₂=CBrCF₃, CFBr=CBrCF₃, CH₂=CBrCF₂Br, CHF=CBrCF₂Br, CHBr=CBrCF₂Br, CF₂=CBrCF₂Br, CBr₂=CBrCF₃ 2Br, CFBr=CBrCF 2Br, CH 2=CBrCFBr 2, CHF=CBrCFBr 2, CHBr=CBrCFBr 2, CF 2=CBrCFBr 2.

[0018] Specific examples of fluoroolefins containing iodine atoms in their molecules include CFI=CH₂ (1-iodo-1-fluoroethylene), CFI=CHF, CFI=CF₂ (1-iodo-1,2,2-trifluoroethylene), CFI=CFI, CFI=CHI, CF₂=CHI, CHF=CHI, CFI=CI₂, CF₂=CI₂, CHF=CI₂, CHI=CI₂, CH₂=CICF₃ (2-iodo-3,3,3-trifluoropropene), CHF=CICF₃, CHI=CICF₃, CF₂=CICF₃, CI₂=CICF₃, CFI=CICF₃, CH₂=CICF₂I, CHF=CICF₂I, CHI=CICF₂I, CF₂=CICF₂I, CI₂=CICF₂I, CFI=CICF₂I, CH₂=CICFI 2. CHF=CICFI 2, CHI=CICFI 2, CF 2=CICFI 2.

[0019] These fluoroolefins can be used alone or in combination with two or more. Furthermore, some of the aforementioned fluoroolefins may sometimes have cis-trans isomers, but either the cis- or trans-type fluoroolefin can be used in the preservation method of the fluoroolefins of this embodiment.

[0020] When storing fluoroolefins in a container, the container can hold a gas consisting solely of fluoroolefins, or a mixture of fluoroolefins and an inert diluent gas. Furthermore, some or all of the fluoroolefins can be liquefied and stored in the container. As the diluent gas, at least one gas selected from nitrogen (N₂), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. The content of the diluent gas, relative to the total amount of gas stored in the container, is preferably 90% by volume or less, more preferably 50% by volume or less.

[0021] [container] Regarding containers for storing fluoroolefins, there are no particular restrictions on their shape, size, or material, as long as they can contain and seal the fluoroolefins. Container materials can include metals, ceramics, and resins. Examples of metals include manganese steel, stainless steel, Hastelloy (registered trademark), and Inconel (registered trademark).

[0022] [Metallic impurities] The preservation method for fluoroolefins in this embodiment contains or does not contain at least one of manganese, cobalt, nickel, and silicon as metallic impurities. Since the sum of the concentrations of manganese, cobalt, nickel, and silicon is below 1000 ppb by mass when the fluoroolefins are present, the aforementioned effects are achieved when the container is used for preservation. That is, the fluoroolefins are less prone to decomposition reactions, and the reaction involving the removal of bromine or iodine atoms from the fluoroolefins is less likely to generate decomposition products of the fluoroolefins or bromine or iodine molecules.

[0023] Here, "excluding" refers to situations where quantification cannot be performed using an inductively coupled plasma mass analyzer (ICP-MS). Furthermore, the metals such as manganese, cobalt, nickel, and silicon in this invention comprise both metal atoms and metal ions. In order to suppress the decomposition reaction of fluoroolefins during storage and the reaction in which bromine or iodine atoms are removed from fluoroolefins, the sum of the concentrations of manganese, cobalt, nickel and silicon contained in the fluoroolefins must be below 1000 ppb by mass, but preferably below 500 ppb by mass, and even more preferably below 100 ppb by mass.

[0024] To further suppress the aforementioned decomposition or detachment reactions during storage, the concentrations of manganese, cobalt, nickel, and silicon in the fluoroolefin are preferably below 300 ppb by mass, and more preferably below 100 ppb by mass. Furthermore, the combined concentrations of manganese, cobalt, nickel, and silicon can be above 1 ppb by mass.

[0025] The concentrations of metallic impurities such as manganese, cobalt, nickel, and silicon in fluoroolefins can be quantified using an inductively coupled plasma mass analyzer (ICP-MS). To further suppress the aforementioned decomposition or detachment reactions during storage, the concentrations of manganese, cobalt, nickel, and silicon, as well as the concentrations of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) in the preferred fluoroolefin are all set to low concentrations.

[0026] That is, fluoroolefins contain at least one of manganese, cobalt, nickel and silicon as metallic impurities or are not present. When they contain the aforementioned, in addition to ensuring that the sum of the concentrations of manganese, cobalt, nickel and silicon is less than 1000 ppb by mass, they also contain at least one of sodium, potassium, magnesium and calcium as the aforementioned impurities or are not present. When they contain the aforementioned, the sum of the concentrations of manganese, cobalt, nickel and silicon, as well as sodium, potassium, magnesium and calcium, is set to less than 2000 ppb by mass to preserve fluoroolefins.

[0027] The total concentration of manganese, cobalt, nickel and silicon, as well as sodium, potassium, magnesium and calcium, contained in the aforementioned conditions is preferably less than 1000 ppb by mass, and even more preferably less than 500 ppb by mass. Furthermore, the total concentration of manganese, cobalt, nickel, silicon, sodium, potassium, magnesium, and calcium can be above 2 ppb by mass.

[0028] In addition, to further suppress the above-mentioned desorption reaction during storage, the concentrations of manganese, cobalt, nickel and silicon, as well as the concentrations of sodium, potassium, magnesium and calcium, and the concentrations of copper (Cu), zinc (Zn) and aluminum (Al) in the preferred fluoroolefin are all set to low concentrations.

[0029] That is, when fluoroolefins contain at least one of manganese, cobalt, nickel, and silicon, and at least one of sodium, potassium, magnesium, and calcium as metallic impurities, and further contain at least one of copper, zinc, and aluminum as metallic impurities, it is preferable to store the fluoroolefins with the sum of the concentrations of all these metallic impurities set below 3000 ppb by mass. More preferably, the sum of the concentrations of all these metallic impurities is set below 1500 ppb by mass, and even more preferably below 1000 ppb by mass.

[0030] The aforementioned metallic impurities can sometimes be present in fluoroolefins as metallic monomers, metallic compounds, metallic halides, or metallic complexes. Examples of the forms in which metallic impurities in fluoroolefins exist include microparticles, droplets, and gases. It is also believed that manganese, cobalt, nickel, and silicon are introduced into fluoroolefins from the raw materials, reactors, and purification equipment used in their synthesis.

[0031] [Manufacturing method of fluoroolefins with low concentration of metallic impurities] The method for producing fluoroolefins with low concentrations of metal impurities is not particularly limited, but examples include methods for removing metal impurities from fluoroolefins with high concentrations of metal impurities. The method for removing metal impurities from fluoroolefins is not particularly limited, and conventional methods can be used. Examples include methods using filters, methods using adsorbents, and distillation.

[0032] The material of the filter that selectively allows fluoroolefins to pass through is preferably resin, and more preferably polytetrafluoroethylene (PTFE), to avoid the contamination of fluoroolefins with metal components. The average pore size of the filter is preferably 0.01 μm to 30 μm, and more preferably 0.1 μm to 10 μm. If the average pore size is within the above range, metal impurities can be effectively removed, and sufficient flow of fluoroolefin gas can be ensured, thereby achieving high productivity.

[0033] The optimal flow rate of fluoroolefin gas through the filter is between 3 mL / min and 300 mL / min per 1 cm² of filter area, more preferably between 10 mL / min and 50 mL / min. If the flow rate of fluoroolefin gas is within the above range, it can prevent the fluoroolefin gas from becoming high pressure, reduce the risk of leakage, and achieve high productivity.

[0034] [Pressure conditions during storage] The pressure conditions for storing fluoroolefins in this embodiment are not particularly limited, as long as the fluoroolefin can be sealed and stored in a container. However, it is preferable to have a pressure of 0.01 MPa to 5 MPa, and more preferably 0.05 MPa to 3 MPa. If the pressure conditions are within the above range, the fluoroolefin can be allowed to flow without humidification when the container is connected to a dry etching apparatus.

[0035] [Temperature requirements for storage] The storage temperature for fluoroolefins in this embodiment is not particularly limited, but it is preferably between -20°C and 50°C, and more preferably between 0°C and 40°C. If the storage temperature is above -20°C, the container is less likely to deform, thus reducing the possibility of oxygen or water entering the container due to loss of airtightness. The introduction of oxygen or water could promote polymerization and decomposition reactions of the fluoroolefins. On the other hand, if the storage temperature is below 50°C, polymerization and decomposition reactions of the fluoroolefins can be inhibited.

[0036] [Etching] The fluoroolefins preserved in the preservation method of this embodiment can be used as etching gases. Therefore, the etching gas containing fluoroolefins preserved in the preservation method of this embodiment can also be used in either plasma etching using plasma or plasmaless etching without plasma.

[0037] Examples of plasma etching include reactive ion etching (RIE), inductively coupled plasma (ICP), capacitively coupled plasma (CCP), electron cyclotron resonance (ECR) plasma etching, and microwave plasma etching. Furthermore, in plasma etching, plasma can be generated in a chamber containing the component to be etched, and can also be divided into a plasma generation chamber and a chamber containing the component to be etched (i.e., remote plasma can be used). [Example]

[0038] The following examples and comparative examples further illustrate the present invention. Fluoroolefins containing metal impurities at various concentrations were prepared. Examples of fluoroolefin preparation are described below. (Modulation Example 1) Prepare one 10L manganese steel gas cylinder and four 1L manganese steel sealable cylinders. These cylinders are designated Cylinder A, Cylinder B, Cylinder C, and Cylinder D, respectively. Fill the cylinder with 5000g of 1-bromo-1,2,2-trifluoroethylene, and liquefy it by cooling to 0°C, forming a liquid phase and a gas phase at approximately 100kPa. After depressurizing the internal pressure of cylinders A, B, C, and D to below 1kPa using a vacuum pump, cool them to -78°C.

[0039] 500g of 1-bromo-1,2,2-trifluoroethylene gas was drawn from the upper outlet of the gas phase section of the gas cylinder, passed through a filter, liquefied at -78°C, and collected in cylinder A under reduced pressure. The aforementioned filter was a PTFE filter manufactured by Flon Industrial Co., Ltd., with an outer diameter of 50mm, a thickness of 80μm, and an average pore size of 0.3μm. The gas flow rate through the filter was controlled at 500mL / min using a mass flow controller. The amount of 1-bromo-1,2,2-trifluoroethylene collected in cylinder A was 492g.

[0040] The 1-bromo-1,2,2-trifluoroethylene collected in cylinder A was designated as sample 1-1. The 1-bromo-1,2,2-trifluoroethylene collected in cylinder A consisted of a gaseous phase and a liquid phase. The gaseous phase was extracted from the upper outlet, and the concentrations of various metallic impurities were determined using an inductively coupled plasma mass analyzer. The results are shown in Table 1.

[0041] Furthermore, the method for determining the concentration of various metallic impurities using an inductively coupled plasma mass analyzer is described in detail below. At 20°C, the liquid phase of 1-bromo-1,2,2-trifluoroethylene in cylinder A is vaporized. Simultaneously, 1-bromo-1,2,2-trifluoroethylene gas is extracted from its gas phase section. 100g of a 1mol / L nitric acid aqueous solution is bubbled through the gas at a flow rate of 100mL / min. This gas introduction brings the 1-bromo-1,2,2-trifluoroethylene into contact with the nitric acid aqueous solution, absorbing metallic impurities into the solution. The mass of the nitric acid aqueous solution after the gas introduction is 80g (M1). The mass difference of cylinder A before and after the gas introduction is 50g (M2).

[0042] 10 g (M3) of nitric acid aqueous solution after gas introduction was taken and diluted to 100 mL (V) with ultrapure water in a volumetric flask. The concentrations of various metal atoms in the diluted nitric acid aqueous solution were determined using an inductively coupled plasma mass analyzer. The concentrations of various metal atoms in 1-bromo-1,2,2-trifluoroethylene (C, g / g) were calculated using the measured values ​​(c1, unit: g / mL) and the following formula.

[0043]

[0044] Next, cylinder A was cooled to approximately 0°C, forming a liquid phase and a gas phase. 100g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase in cylinder A and transferred to cylinder B under reduced pressure. Then, 10g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the gas cylinder and transferred to cylinder B under reduced pressure. Cylinder B was then heated to room temperature and allowed to stand for 24 hours. The 1-bromo-1,2,2-trifluoroethylene after standing was designated as sample 1-2. After standing, 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase in cylinder B, and the concentrations of various metallic impurities were determined using an inductively coupled plasma mass analyzer, in the same manner as described above. The results are shown in Table 1.

[0045] Similarly, 100g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase section of cylinder A and transferred to cylinder C under reduced pressure. Additionally, 100g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the gas cylinder and transferred to cylinder C under reduced pressure. Then, cylinder C was heated to room temperature and allowed to stand for 24 hours. The 1-bromo-1,2,2-trifluoroethylene after standing was designated as samples 1-3. After standing, 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase section of cylinder C, and the concentrations of various metallic impurities were determined using an inductively coupled plasma mass analyzer in the same manner as described above. The results are shown in Table 1.

[0046] Similarly, 100g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase section of cylinder A and transferred to cylinder D under reduced pressure. Additionally, 200g of 1-bromo-1,2,2-trifluoroethylene gas was extracted from the gas cylinder and transferred to cylinder D under reduced pressure. Then, cylinder D was heated to room temperature and allowed to stand for 24 hours. The 1-bromo-1,2,2-trifluoroethylene after standing was designated as samples 1-4. After standing, 1-bromo-1,2,2-trifluoroethylene gas was extracted from the upper outlet of the gas phase section of cylinder D, and the concentrations of various metallic impurities were determined using an inductively coupled plasma mass analyzer in the same manner as described above. The results are shown in Table 1.

[0047] (Modulation Example 2) Except for using 1-bromo-1-fluoroethylene as the fluoroolefin and setting the temperature of cylinder A to 10°C when the gas from cylinder A is delivered to cylinder B, the same operation as in Modulation Example 1 was performed to modify samples 2-1 to 2-4. Then, the concentrations of various metallic impurities in each sample were determined using an inductively coupled plasma mass analyzer in the same manner as in Modulation Example 1. The results are shown in Table 2.

[0048]

[0049] (Modulation Example 3) Except for using 2-bromo-3,3,3-trifluoropropene as the fluoroolefin and setting the temperature of cylinder A to 30°C when transferring gas from cylinder A to cylinder B, the same procedures as in Modification Example 1 were performed to modify samples 3-1 to 3-4. Then, using the same method as in Modification Example 1, the concentrations of various metallic impurities in each sample were determined by an inductively coupled plasma mass analyzer. The results are shown in Table 3.

[0050]

[0051] (Modulation Example 4) Except for using 1-iodine-1,2,2-trifluoroethylene as the fluoroolefin and setting the temperature of cylinder A to 30°C when the gas from cylinder A is delivered to cylinder B, the same operation as in Modulation Example 1 was performed to modify samples 4-1 to 4-4. Then, the concentrations of various metallic impurities in each sample were determined using an inductively coupled plasma mass analyzer in the same manner as in Modulation Example 1. The results are shown in Table 4.

[0052]

[0053] (Example 1) After a sealed cylinder A was left to stand at 20°C for 30 days, 1-bromo-1,2,2-trifluoroethylene gas was extracted from the gas phase section of cylinder A. The concentrations of decomposition products, bromine molecules, and iodine molecules in sample 1-1 were determined by gas chromatography and Raman spectroscopy. The results showed that none of the decomposition products, bromine molecules, or iodine molecules were detected.

[0054] Furthermore, the determination conditions for gas chromatography are as follows. Gas Chromatography System: Shimadzu Corporation GC-2014 Column: Carbopack B_1% sp-1000 Injection temperature: 200℃ Column temperature: 100℃ Detector: FID Detector temperature: 200℃ Carrier gas: Helium Detection limit: 1 ppm by mass

[0055] (Examples 2-12 and Comparative Examples 1-4) Table 5 shows a comparison of the analytical objects and results in Examples 2-12 and Comparative Examples 1-4 with those in Example 1. That is, except for the items shown in Table 5, the analyses were performed using the same procedures as in Example 1. Furthermore, in gas chromatography, the ratio (%) of the total area of ​​all peaks located on the lower molecular weight side than the original fluoroolefin to the peak area of ​​the original fluoroolefin (e.g., 1-bromo-1,2,2-trifluoroethylene in Example 1) is shown in Table 5.

[0056]

Claims

1. A method for preserving fluoroolefins, wherein the fluoroolefin having bromine or iodine atoms in its molecule is selected from at least one of 1-bromo-1,2,2-trifluoroethylene, 1-bromo-1-fluoroethylene, 1-iodo-1,2,2-trifluoroethylene, and 1-iodo-1-fluoroethylene, wherein the fluoroolefin contains or does not contain at least one of manganese, cobalt, nickel, and silicon as a metallic impurity, and the sum of the concentrations of manganese, cobalt, nickel, and silicon when the aforementioned metallic impurity is present is set to 1000 ppb by mass or less, and the fluoroolefin is preserved in a container.

2. The method for storing fluoroolefins as claimed in claim 1, wherein the aforementioned fluoroolefin may contain or not contain at least one of sodium, potassium, magnesium and calcium as the aforementioned metallic impurities, and the total concentration of manganese, cobalt, nickel and silicon, as well as sodium, potassium, magnesium and calcium when the aforementioned metallic impurities are present, is set to 2000 ppb by mass or less, and the aforementioned fluoroolefin is stored in a container.

3. The method for storing fluoroolefins as requested in item 1 or 2, wherein the fluoroolefins are stored at a temperature between -20°C and 50°C.

4. The method for preserving fluoroolefins as requested in item 1 or 2, wherein the aforementioned container is made of manganese steel.