How to store fluorobutene

Abstract

This invention provides a method for storing fluorobutene that is less prone to polymerization during storage. [Solution] General formula C4H x F y Fluorobutene, represented by the general formula where x is between 0 and 7, y is between 1 and 8, and x+y is 8, may or may not contain at least one of sodium, potassium, magnesium, and calcium as a metal impurity. This fluorobutene is stored in a container with the sum of the concentrations of sodium, potassium, magnesium, and calcium (in the case of containing the aforementioned) being 1000 ppb by mass or less.

Description

Technical Field

[0001] The present invention relates to a method for storing fluorobutene.

Background Art

[0002] For example, unsaturated fluorocarbons disclosed in Patent Documents 1, 2, etc. may be used as etching gases for dry etching.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, unsaturated fluorocarbons are likely to polymerize due to the reaction of unsaturated bonds, so there was a risk that polymerization would progress and the purity would decrease during long-term storage. An object of the present invention is to provide a method for storing fluorobutene in which polymerization hardly progresses during storage.

Means for Solving the Problems

[0005] To solve the above problems, one aspect of the present invention is as follows in [1] to [4]. [1] A method for storing fluorobutene represented by the general formula C4H x F y where x in the general formula is 0 or more and 7 or less, y is 1 or more and 8 or less, and x + y is 8, A method for storing fluorobutene, wherein the fluorobutene contains or does not contain at least one of sodium, potassium, magnesium, and calcium as a metal impurity, and in the case where it contains such impurities, the sum of the concentrations of sodium, potassium, magnesium, and calcium is 1000 ppb by mass or less, and the fluorobutene is stored in a container.

[0006] [2] The method for storing fluorobutene according to [1], wherein the fluorobutene further contains or does not contain at least one of manganese, cobalt, nickel, and silicon as a metal impurity, and in the case of such impurity, the total concentration of sodium, potassium, magnesium, and calcium, as well as manganese, cobalt, nickel, and silicon, is 2000 ppb by mass or less when the fluorobutene is stored in a container.

[0007] [3] A method for storing fluorobutene according to [1] or [2], wherein the fluorobutene is at least one selected from 1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,4,4,4-heptafluoro-2-butene, 3,3,4,4,4-pentafluoro-1-butene, and 2,3,3,4,4,4-hexafluoro-1-butene. [4] Store at a temperature of -20°C or higher and 50°C or lower. The storage method for fluorobutene described in any one of the items [1] to [3]. [Effects of the Invention]

[0008] According to the present invention, polymerization of fluorobutene is less likely to proceed during storage. [Modes for carrying out the invention]

[0009] One embodiment of the present invention is described below. This embodiment is merely an 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 such modified or improved forms may also be included in the present invention.

[0010] The storage method for fluorobutene according to this embodiment is based on the general formula C4H x F y A method for storing fluorobutene, which is represented by the general formula where x is between 0 and 7, y is between 1 and 8, and x+y is 8, wherein the fluorobutene contains or does not contain at least one of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) as a metal impurity, and in the case where it contains sodium, potassium, magnesium, and calcium, the sum of the concentrations of these impurities is 1000 ppb by mass or less, and the fluorobutene is stored in a container.

[0011] If fluorobutene contains at least one of the following metal impurities—sodium, potassium, magnesium, and calcium—the catalytic action of the metal impurity accelerates the polymerization reaction of the carbon-carbon double bond in fluorobutene. Therefore, fluorobutene containing metal impurities may undergo polymerization during storage, potentially leading to a decrease in purity.

[0012] Fluorobutene stored by the storage method according to this embodiment does not contain metal impurities, or if it does, the amount is small. Therefore, polymerization is less likely to proceed even during long-term storage, and a decrease in purity is less likely to occur. Thus, fluorobutene can be stored stably for a long period of time without adding a polymerization inhibitor to suppress the polymerization of fluorobutene.

[0013] The techniques disclosed in Patent Documents 1 and 2 do not take into account the concentration of metal impurities in unsaturated fluorocarbons. Therefore, when unsaturated fluorocarbons are stored using the techniques disclosed in Patent Documents 1 and 2, the polymerization reaction of the carbon-carbon double bond in the unsaturated fluorocarbons may be accelerated by the metal impurities. As a result, polymerization of the unsaturated fluorocarbons may progress during storage, leading to a decrease in purity.

[0014] The storage method for fluorobutene according to this embodiment will be described in more detail below. [Fluorobutene] The fluorobutene according to this embodiment has the general formula C4H x F y It is represented by the formula and satisfies the following three conditions: x is between 0 and 7 in the general formula, y is between 1 and 8, and x+y is 8. The type of fluorobutene is not particularly limited as long as it satisfies the above requirements, and may be linear fluorobutene or branched fluorobutene (isobutene), but those similar to fluoro-1-butene and those similar to fluoro-2-butene are preferred.

[0015] Specific examples of fluoro-1-butene include CHF2-CF2-CF=CF2, CF3-CF2-CF=CHF, CF3-CHF-CF=CF2, CF3-CF2-CH=CF2, CHF2-CHF-CF=CF2, CHF2-CF2-CF=CHF, CF3-CHF-CF=CHF, CF3-CF2-CH=CHF, CF3-CHF-CH=CF2, CHF2-CF2-CH=CF2, CH3-CF2-CF=CF2, CH2F-CHF-CF=CF2, CH2F-CF2-CH=CF2, CH2F-CF2-CF=CHF, CHF2-CH2-CF=CF2, CHF2-CHF-CH=CF2, CHF2-CHF-CF=CHF, CHF2-CF2-CH=CHF, CHF2-CF2-CF=CH2, CF3-CH2-CH=CF2, CF3-CH2-CF=CHF, CF3-CHF-CH=CHF, CF3-CHF-CF=CH2, CF3-CF2-CH=CH2, CH3-CHF-CF=CF2, CH3-CF2-CH=CF2, CH3-CF2-CF=CHF, CH2F-CH2-CF=CF2, CH2F-CHF-CH=CF2, CH2F-CHF-CF=CHF, CH2F-CF2-CH=CHF, CH2F-CF2-CF=CH2, CHF2-CH2-CH=CF2, CHF2-CH2-CF=CHF, CHF2-CHF-CH=CHF, CHF2-CHF-CF=CH2, CHF2-CF2-CH=CH2, CF3-CH2-CH=CHF, CF3-CH2-CF=CH2, CF3-CHF-CH=CH2, CH3-CH2-CF=CF2, CH3-CHF-CH=CF2, CH3-CHF-CF=CHF, CH3-CF2-CH=CHF, CH3-CF2-CF=CH2, CH2F-CH2-CH=CF2, CH2F-CH2-CF=CHF, CH2F-CHF-CH=CHF, CH2F-CHF-CF=CH2, CH2F-CF2-CH=CH2, CHF2-CH2-CH=CHF, CHF2-CH2-CF=CH2, CHF2-CHF-CH=CH2, CF3-CH2-CH=CH2, CH3-CH2-CH=CF2, CH3-CH2-CF=CHF, CH3-CHF-CH=CHF, CH3-CHF-CF=CH2, CH3-CF2-CH=CH2, CH2F-CH2-CH=CHF, CH2F-CH2-CF=CH2, CH2F-CHF-CH=CH2, CHF2-CH2-CH=CH2,Examples include CH3-CH2-CH=CHF, CH3-CH2-CF=CH2, CH3-CHF-CH=CH2, and CH2F-CH2-CH=CH2.

[0016] Specific examples of fluoro-2-butene include CHF2-CF=CF-CF3, CF3-CH=CF-CF3, CH2F-CF=CF-CF3, CHF2-CH=CF-CF3, CHF2-CF=CF-CHF2, CF3-CH=CH-CF3, CH3-CF=CF-CF3, CH2F-CH= CF-CF3, CH2F-CF=CH-CF3, CH2F-CF=CF-CHF2, CHF2-CH=CH-CF3, CHF2-CF=CH-CHF2, CH3-CH=CF-CF3, CH3-CF=CH-CF3, CH3-CF=CF-CHF2, CH2F-CH=CH-CF3, CH2F -CH=CF-CHF2, CH2F-CF=CH-CHF2, CH2F-CF=CF-CH2F, CHF2-CH=CH-CHF2, CH3-CH=CH-CF3, CH3-CH=CF-CHF2, CH3-CF=CH-CHF2, CH3-CF=CF-CH2F, CH2F-CF=CH- CH2F, CH2F-CH=CH-CHF2, CH3-CH=CH-CHF2, CH3-CH=CF-CH2F, CH3-CF=CH-CH2F, CH3-CF=CF-CH3, CH2F-CH=CH-CH2F, CH3-CH=CH-CH2F, CH3-CH=CF-CH3.

[0017] These fluorobutenes may be used individually or in combination of two or more. Furthermore, some of the above-mentioned fluorobutenes have cis-trans isomers; both cis and trans forms of fluorobutene can be used in the fluorobutene storage method according to this embodiment.

[0018] When storing fluorobutene in a container, a gas consisting only of fluorobutene may be stored in the container, or a mixed gas containing fluorobutene and a diluent gas may be stored in the container. As the diluent gas, at least one selected from nitrogen gas (N₂), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. The content of the diluent gas is preferably 90% by volume or less, more preferably 50% by volume or less, based on the total amount of the gas stored in the container.

[0019] 〔Container〕 Regarding the container for storing fluorobutene, the shape, size, material, etc. are not particularly limited as long as the container can accommodate and seal fluorobutene. As the material of the container, metal, ceramic, resin, etc. can be adopted. Examples of metals include manganese steel, stainless steel, Hastelloy (registered trademark), Inconel (registered trademark), etc.

[0020] 〔Metal Impurities〕 The fluorobutene according to this embodiment may or may not contain at least one of sodium, potassium, magnesium, and calcium as metal impurities. However, when contained, the sum of the concentrations of sodium, potassium, magnesium, and calcium is 1000 mass ppb or less and is stored in the container. Therefore, as described above, the polymerization reaction of the carbon-carbon double bond of fluorobutene is less likely to be promoted, and as a result, the polymerization of fluorobutene during storage is less likely to proceed. Here, "not containing" means the case where it cannot be quantified by an inductively coupled plasma mass spectrometer (ICP-MS).

[0021] In order to make the polymerization of fluorobutene less likely to proceed during storage, the sum of the concentrations of sodium, potassium, magnesium, and calcium contained in fluorobutene needs to be 1000 mass ppb or less, preferably 500 mass ppb or less, and more preferably 100 mass ppb or less.

[0022] To further suppress the polymerization of fluorobutene during storage, the concentrations of sodium, potassium, magnesium, and calcium contained in the fluorobutene are preferably 300 ppb by mass or less, and more preferably 100 ppb by mass or less.

[0023] Furthermore, the sum of the concentrations of sodium, potassium, magnesium, and calcium may be 1 ppb by mass or more. The concentrations of metallic impurities such as sodium, potassium, magnesium, and calcium in fluorobutene can be quantified using inductively coupled plasma mass spectrometry (ICP-MS).

[0024] To further suppress the polymerization of fluorobutene during storage, it is preferable to keep the concentrations of manganese (Mn), cobalt (Co), nickel (Ni), and silicon (Si) low, along with the concentrations of sodium, potassium, magnesium, and calcium in the fluorobutene.

[0025] In other words, it is preferable to store fluorobutene with or without containing at least one of sodium, potassium, magnesium, and calcium as a metal impurity, and in the case of containing such impurities, the sum of the concentrations of sodium, potassium, magnesium, and calcium being 1000 ppb by mass or less, and further containing or without containing at least one of manganese, cobalt, nickel, and silicon as a metal impurity, and in the case of containing such impurities, the sum of the concentrations of sodium, potassium, magnesium, and calcium, as well as manganese, cobalt, nickel, and silicon being 2000 ppb by mass or less, more preferably 1000 ppb by mass or less, and even more preferably 500 ppb by mass or less. Furthermore, the sum of the concentrations of sodium, potassium, magnesium, and calcium, as well as manganese, cobalt, nickel, and silicon, may be 2 ppb by mass or more.

[0026] Furthermore, in order to further suppress the polymerization of fluorobutene during storage, it is preferable to keep the concentrations of copper (Cu), zinc (Zn), and aluminum (Al) low, along with the concentrations of sodium, potassium, magnesium, and calcium, as well as manganese, cobalt, nickel, and silicon in the fluorobutene.

[0027] In other words, if fluorobutene contains at least one of sodium, potassium, magnesium, and calcium, and at least one of manganese, cobalt, nickel, and silicon as metal impurities, and further contains at least one of copper, zinc, and aluminum as metal impurities, it is preferable to store the fluorobutene with the sum of the concentrations of all these metal impurities being 3000 ppb by mass or less, more preferably 1500 ppb by mass or less, and even more preferably 1000 ppb by mass or less.

[0028] The metal impurities mentioned above may be present in fluorobutene as elemental metals, metal compounds, metal halides, or metal complexes. Examples of metal impurities in fluorobutene include fine particles, droplets, and gases. Sodium, potassium, magnesium, and calcium are thought to be introduced into fluorobutene from the raw materials, reactors, and purification equipment used in its synthesis.

[0029] [Method for producing fluorobutene with low concentration of metal impurities] The method for producing fluorobutene with a low concentration of metal impurities is not particularly limited, but one example is a method for removing metal impurities from fluorobutene with a high concentration of metal impurities. The method for removing metal impurities from fluorobutene is not particularly limited, and known methods can be employed. Examples include using filters, using adsorbents, and distillation.

[0030] The material of the filter that selectively passes fluorobutene gas is preferably resin, and particularly preferably polytetrafluoroethylene, in order to avoid contamination of fluorobutene 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, it is possible to sufficiently remove metal impurities and ensure a sufficient flow rate of fluorobutene gas to achieve high productivity.

[0031] The flow rate of fluorobutene gas passing through the filter is preferably between 100 mL / min and 5000 mL / min, and more preferably between 300 mL / min and 1000 mL / min. If the flow rate of fluorobutene gas is within the above range, the pressure of the fluorobutene gas is suppressed, reducing the risk of leakage of fluorobutene gas and enabling high productivity.

[0032] [Storage pressure conditions] The storage pressure conditions in the fluorobutene storage method according to this embodiment are not particularly limited as long as the fluorobutene can be stored in a sealed container, but it is preferable to set the pressure to 0.05 MPa or more and 5 MPa or less, and more preferably to 0.1 MPa or more and 3 MPa or less. If the pressure conditions are within the above range, the fluorobutene can be circulated without humidification when the container is connected to the dry etching apparatus.

[0033] [Storage temperature conditions] The storage temperature conditions for fluorobutene in the storage method according to this embodiment are not particularly limited, but it is preferably -20°C to 50°C, and more preferably 0°C to 40°C. If the storage temperature is -20°C or higher, deformation of the container is less likely to occur, so the airtightness of the container is lost and the possibility of oxygen, water, etc. entering the container is low. If oxygen, water, etc. enter, the polymerization and decomposition reactions of fluorobutene may be accelerated. On the other hand, if the storage temperature is 50°C or lower, the polymerization and decomposition reactions of fluorobutene are suppressed.

[0034] 〔etching〕 The fluorobutene according to this embodiment can be used as an etching gas. Furthermore, the etching gas containing the fluorobutene according to this embodiment can be used in both plasma etching, which uses plasma, and plasmaless etching, which does not use plasma.

[0035] Examples of plasma etching include reactive ion etching (RIE), inductively coupled plasma (ICP) etching, capacitively coupled plasma (CCP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave plasma etching. Furthermore, in plasma etching, the plasma may be generated within the chamber where the workpiece to be etched is placed, or the plasma generation chamber and the chamber in which the workpiece to be etched is placed may be separated (i.e., remote plasma may be used). [Examples]

[0036] The present invention will be further described below with reference to examples and comparative examples. Fluorobutene containing metal impurities at various concentrations was prepared. An example of fluorobutene preparation is described below. (Preparation Example 1) One 10L manganese steel cylinder and four 1L manganese steel cylinders were prepared. These cylinders were referred to as Cylinder A, Cylinder B, Cylinder C, and Cylinder D, respectively. 5000g of 1,1,1,4,4,4-hexafluoro-2-butene (boiling point: 9°C) was filled into the cylinder and liquefied by cooling to 0°C, forming a liquid phase and a gas phase at approximately 100kPa. Cylinders A, B, C, and D were then cooled to -78°C after the internal pressure was reduced to below 1kPa using a vacuum pump.

[0037] 500 g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of the cylinder where the gas phase is located, passed through a filter, and then collected in cylinder A under reduced pressure. This filter is a PTFE filter manufactured by Fluorocarbon Industries Co., Ltd., with an outer diameter of 50 mm, a thickness of 80 μm, and an average pore size of 0.3 μm. The gas flow rate through the filter was controlled to 500 mL / min by a mass flow controller. The amount of 1,1,1,4,4,4-hexafluoro-2-butene gas collected in cylinder A was 492 g.

[0038] The 1,1,1,4,4,4-hexafluoro-2-butene collected in cylinder A was designated as sample 1-1. The gas of 1,1,1,4,4,4-hexafluoro-2-butene collected in cylinder A was extracted from the upper outlet, and the concentrations of various metal impurities were measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 1.

[0039] [Table 1]

[0040] Next, cylinder A was heated to approximately 0°C to form a liquid phase and a gas phase. 100g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder B under reduced pressure. Furthermore, 10g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the 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 1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-2. After standing, the 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder B, where the gas phase was present, and the concentrations of various metal impurities were measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 1.

[0041] Similarly, 100g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder C under reduced pressure. Furthermore, another 100g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the cylinder and transferred to cylinder C under reduced pressure. Then, cylinder C was heated to room temperature and left to stand for 24 hours. The 1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-3. The 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder C, where the gas phase was present, and the concentrations of various metal impurities were measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 1.

[0042] Similarly, 100g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder D under reduced pressure. Furthermore, 200g of 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the cylinder and transferred to cylinder D under reduced pressure. Then, cylinder D was heated to room temperature and left to stand for 24 hours. The 1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-4. The 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder D, where the gas phase was present, and the concentrations of various metal impurities were measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 1.

[0043] (Preparation Example 2) Samples 2-1 to 2-4 were prepared using the same procedure as in Preparation Example 1, except that 1,1,1,2,4,4,4-heptafluoro-2-butene was used as the fluorobutene. The concentrations of various metal impurities in each sample were then measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 2.

[0044] [Table 2]

[0045] (Preparation Example 3) Samples 3-1 to 3-4 were prepared using the same procedure as in Preparation Example 1, except that 3,3,4,4,4-pentafluoro-1-butene was used as the fluorobutene. The concentrations of various metal impurities in each sample were then measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 3.

[0046] [Table 3]

[0047] (Preparation Example 4) Samples 4-1 to 4-4 were prepared using the same procedure as in Preparation Example 1, except that 2,3,3,4,4,4-hexafluoro-1-butene was used as the fluorobutene. The concentrations of various metal impurities in each sample were then measured using an inductively coupled plasma mass spectrometer. The results are shown in Table 4.

[0048] [Table 4]

[0049] (Example 1) After leaving cylinder A standing at 20°C for 30 days, the 1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the gas phase of cylinder A and analyzed by gas chromatography to quantify the concentration of the 1,1,1,4,4,4-hexafluoro-2-butene dimer in sample 1-1. As a result, no dimer was detected. The measurement conditions for gas chromatography are as follows: Gas chromatograph: Shimadzu Corporation GC-2014 Column:carbopackB_1% sp-1000 Injection temperature: 200℃ Column temperature: 100℃ Detector: FID Detector temperature: 200℃ Carrier gas: Helium Detection limit: 1 ppm by mass

[0050] (Examples 2-12 and Comparative Examples 1-4) Table 5 shows the analytes and analysis results for Examples 2-12 and Comparative Examples 1-4, in comparison with Example 1. That is, for items other than those shown in Table 5, the analysis was performed using the same procedure as in Example 1.

[0051] [Table 5]

Claims

1. General formula C 4 H x F y A method for storing fluorobutene, which is represented by the above general formula, wherein x is between 0 and 7, y is between 1 and 8, and x + y is 8, A method for storing fluorobutene, wherein the fluorobutene contains or does not contain at least one of sodium, potassium, magnesium, and calcium as a metal impurity, and in the case where it contains such impurities, the sum of the concentrations of sodium, potassium, magnesium, and calcium is 1000 ppb by mass or less, and the fluorobutene is stored in a container.

2. A method for storing fluorobutene according to claim 1, wherein the fluorobutene further contains or does not contain at least one of manganese, cobalt, nickel, and silicon as a metal impurity, and in the case of such impurity, the total concentration of sodium, potassium, magnesium, and calcium, as well as manganese, cobalt, nickel, and silicon, is 2000 ppb by mass or less, and the fluorobutene is stored in a container.

3. A method for storing fluorobutene according to claim 1 or claim 2, wherein the fluorobutene is at least one selected from 1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,4,4,4-heptafluoro-2-butene, 3,3,4,4,4-pentafluoro-1-butene, and 2,3,3,4,4,4-hexafluoro-1-butene.

4. A method for storing fluorobutene according to any one of claims 1 to 3, wherein the fluorobutene is stored at a temperature of -20°C or higher and 50°C or lower.

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