Method for producing vinylidene fluoride

Abstract

A method for producing vinylidene fluoride, the method including a reaction step for obtaining vinylidene fluoride using a starting material composition containing 1, 1, 2, 2-tetrafluorocyclobutane and water, the water content in the starting material composition being 1000 ppm by mass or less with respect to the 1, 1, 2, 2-tetrafluorocyclobutane content.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing vinylidene fluoride. Background Technology

[0002] Vinylidene fluoride is useful as a monomer for fluoropolymers.

[0003] For example, Patent Document 1 describes a method for obtaining vinylidene fluoride from 1,1,2,2-tetrafluorocyclobutane in the presence of helium.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: US Patent No. 3,996,301

[0007] Non-patent literature 1: Makoto Kuzumi, Journal of the Chemical Society of Japan, 1978, 10, 1406-1410. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, in Patent Document 1, since helium is used as a diluent, there is a tendency for the target compound, vinylidene fluoride, to be removed during the purification process when helium is removed. Alternatively, water vapor can be used as a diluent, but there is a tendency for the acidity of the reaction products to increase.

[0010] One objective of this disclosure is to provide a method for manufacturing vinylidene fluoride that can suppress the increase in acidity.

[0011] Solution for solving the problem

[0012] This disclosure includes the following methods.

[0013] <1>

[0014] A method for manufacturing vinylidene fluoride includes a reaction step of obtaining vinylidene fluoride using a raw material composition comprising 1,1,2,2-tetrafluorocyclobutane and water, wherein the water content relative to the 1,1,2,2-tetrafluorocyclobutane content is less than 1000 ppm by mass in the reaction step.

[0015] <2>

[0016] according to <1> In the method for manufacturing vinylidene fluoride, the content of the heat transfer medium gas in the reaction step is less than 10 mol% relative to the content of 1,1,2,2-tetrafluorocyclobutane.

[0017] <3>

[0018] according to <1> or <2> In the method for manufacturing vinylidene fluoride, the temperature inside the reactor used in the reaction process is above 600°C.

[0019] <4>

[0020] according to <1> ~ <3> In any one of the methods for manufacturing vinylidene fluoride, the contact time between 1,1,2,2-tetrafluorocyclobutane and water is more than 1 second.

[0021] <5>

[0022] according to <1> ~ <4> In any one of the methods for producing vinylidene fluoride, the pressure inside the reactor used in the reaction step is 0.6 MPaG or less.

[0023] <6>

[0024] according to <1> ~ <5> The method for manufacturing vinylidene fluoride according to any one of the following methods further includes: a step of supplying a crude product containing vinylidene fluoride obtained in the reaction step to a container in which at least a portion of a component in contact with the crude product is made of a metallic material; or a step of allowing it to flow in a flow path in which at least a portion of a component in contact with the crude product is made of a metallic material.

[0025] The effects of the invention

[0026] According to one embodiment of this disclosure, a method for manufacturing vinylidene fluoride that can suppress the increase in acidity is provided. Attached Figure Description

[0027] Figure 1 This is a schematic structural diagram illustrating an example of a manufacturing apparatus. Detailed Implementation

[0028] In this disclosure, the numerical range represented by “~” refers to the range in which the values ​​recorded before and after “~” are respectively the minimum and maximum values.

[0029] In the numerical ranges described in stages in this invention, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, in the numerical ranges described in this invention, the upper or lower limit value recorded in a certain numerical range can be replaced with the values ​​shown in the embodiments.

[0030] In this invention, a combination of two or more preferred methods is a more preferred method.

[0031] In this invention, when there are multiple substances equivalent to each component, unless otherwise specified, the amount of each component refers to the total amount of the multiple substances.

[0032] [VdF manufacturing method]

[0033] The method for producing vinylidene fluoride (VdF) disclosed herein includes a reaction step of obtaining VdF using a feedstock composition comprising 1,1,2,2-tetrafluorocyclobutane (C354) and water. In the feedstock composition, the water content relative to the C354 content is less than 1000 ppm by mass.

[0034] According to the method for manufacturing VdF disclosed herein, the increase in acidity can be suppressed. An increase in acidity refers to a decrease in pH.

[0035] In the VdF manufacturing method described in Patent Document 1, helium is used as a diluent. Helium has a boiling point of -269°C, while VdF has a boiling point of -83°C, lower than that of VdF. Therefore, in the purification process, when removing helium, there is a tendency for VdF, the target compound, to be removed along with the helium. Furthermore, nitrogen has a boiling point of -196°C, and tetrafluoromethane has a boiling point of -184°C. Therefore, it is believed that when using nitrogen or tetrafluoromethane as a diluent, VdF, the target compound, will also be removed in the purification process, similar to when using helium. Water vapor has also been considered as a diluent, but when using water vapor, there is a tendency for acidic components in the reaction products to dissolve in the condensed water after the reaction and corrode the metal components in contact with it. Additionally, it is believed that using water vapor as a diluent, as described in Non-Patent Document 1, tends to promote the dehydrohalogenation reaction and increase the acidic components in the reaction products.

[0036] In contrast, in the VdF manufacturing method of this disclosure, water is included in the reaction process, but the water content is less than 1000 ppm by mass relative to the C354 content, thus suppressing the increase in acidity of the reaction product. Because the increase in acidity of the reaction product can be suppressed, for example, even if the reaction product is supplied to a container in which at least a portion of the components in contact with the reaction product is made of a metallic material, the container is not easily corroded. Furthermore, even if the product flows through a flow path in which at least a portion of the components in contact with the reaction product is made of a metallic material, the flow path is not easily corroded.

[0037] -Reaction Process-

[0038] <Raw Material Composition>

[0039] In the reaction step of the VdF manufacturing method disclosed herein, a raw material composition containing C354 and water are used.

[0040] In this disclosure, the starting material composition refers to the components used in the reaction to generate VdF. It should be noted that the starting material composition may consist solely of C354.

[0041] In this disclosure, a portion of the water may be water vapor. Water vapor refers to steam or superheated steam composed of water (H2O).

[0042] From the viewpoint of suppressing the increase in acidity, the water content relative to the C354 content in the reaction process is 1000 ppm by mass or less, preferably 100 ppm by mass or less. There is no particular limitation on the lower limit of the water content, but it can be more than 5 ppm by mass.

[0043] The water content was determined by the Karl Fischer method (electroelectric method). It should be noted that the water content in the reaction process refers to the water content within the reactor where the reaction takes place. If water is not supplied to the reactor, the water content in the reaction process can be replaced by the water content of the raw material composition before it is supplied to the reactor.

[0044] The water used in the reaction process can be added later. During the manufacture of C354, the water can be dissolved in C354 or it can coexist with the raw material composition containing C354. To ensure that the water content relative to the C354 content is less than 1000 ppm by mass, it is preferable not to add water afterwards.

[0045] The content of C354 relative to the total volume of the raw material composition is preferably 50% by volume or more, more preferably 80% by volume or more. There is no particular upper limit to the content of C354, for example, it can be 100% by volume.

[0046] In the reaction process, the content of the heat transfer medium gas relative to the content of C354 is preferably 50 mol% or less, more preferably 30 mol% or less. From the viewpoint of separability, it is preferable that the heat transfer medium gas is substantially absent, and the content is preferably 10 mol% or less, more preferably 5 mol% or less, further preferably 3 mol% or less, even more preferably 1 mol% or less, particularly preferably 0.1 mol% or less, and most preferably 0 mol%.

[0047] In particular, a low content of a heat medium gas (e.g., nitrogen) with a boiling point lower than VdF can suppress the loss of VdF along with the heat medium gas during crude product distillation.

[0048] Based on the above viewpoint, the content of the heat medium gas with a boiling point lower than VdF is preferably 20 mol% or less relative to the content of c354, more preferably 10 mol% or less, and even more preferably 5 mol% or less.

[0049] In this disclosure, the heat transfer medium gas refers to a medium that does not substantially decompose when alone at the temperature inside the reactor, specifically, it is desirable for a medium that does not substantially decompose when alone at a temperature of 100 to 1000°C.

[0050] Examples of gases that can be used as heat transfer media include rare gases such as helium and argon; nitrogen; carbon dioxide; and perfluoroalkyl compounds such as tetrafluoromethane.

[0051] Examples of perfluoroalkyl compounds include tetrafluoromethane, hexafluoroethane, and octafluoropropane.

[0052] The raw material composition may contain other components besides C354. Examples of other components include, for instance, components derived from the manufacture of C354.

[0053] Components used in the manufacture of C354 include, for example, tetrafluoroethylene (TFE), ethylene, dichlorofluoromethane (R22), octafluorocyclobutane (C318), and 3,3-difluoropropylene.

[0054] <Reaction Conditions>

[0055] As a reactor supplying C354 and water, its shape and structure are not particularly limited, as long as it can withstand the temperature and pressure inside the reactor (described later). For example, a cylindrical vertical reactor can be used. Materials for the reactor include stainless steel, glass, and alloys primarily composed of iron, nickel, or chromium. The reactor may be equipped with a heating unit such as an electric heater to heat its interior.

[0056] C354 and water can be directly introduced into the reactor at room temperature, but to improve the reactivity within the reactor, they can also be heated (preheated) before being supplied. When preheating is performed, C354 is preferably heated to a temperature of 50–300°C before being supplied to the reactor.

[0057] In addition, the components contained in the raw material composition can be pre-mixed and then supplied to the reactor, or they can be supplied to the reactor separately and mixed in the reactor.

[0058] From the perspective of improving yield, the temperature inside the reactor during the reaction process is preferably above 600°C, and more preferably above 700°C.

[0059] From the viewpoint of improving yield, the contact time of C354 in the reactor is preferably 1 second or more, more preferably 5 seconds or more. The upper limit of the contact time is, for example, 300 seconds.

[0060] Contact time can also be described as residence time within the reactor. The contact time (in seconds) mentioned above is calculated using the following formula.

[0061] Contact time (seconds) = [Volume of feed composition at reaction temperature supplied to the reactor per second] / [Volume of reactor]

[0062] When the contact time of C354 is more than 1 second, the generation of ethylene, which is a heat medium gas with a boiling point lower than VdF, can be suppressed, and the loss of VdF along with ethylene during crude product distillation can be suppressed.

[0063] From the perspective of reactor pressure resistance, the pressure inside the reactor during the reaction process is preferably 0.6 MPaG or higher. There is no particular limitation on the lower limit of the pressure.

[0064] It should be noted that, in this invention, pressure expressed in MPaG is gauge pressure.

[0065] -Supply Process-

[0066] The method for manufacturing VdF disclosed herein preferably further includes: a step of supplying a crude product containing VdF obtained in the reaction step to a container in which at least a portion of a component in contact with the crude product is made of a metallic material; or a step of allowing it to flow in a flow path in which at least a portion of a component in contact with the crude product is made of a metallic material.

[0067] The preferred embodiment of "a container in which at least a portion of the component in contact with the crude product is made of a metallic material" is the same as the preferred embodiment of "a flow path in which at least a portion of the component in contact with the crude product is made of a metallic material".

[0068] Alternatively, the container can be replaced with a flow path.

[0069] A container whose components in contact with the crude product are made of at least a portion of a metallic material can be, for example, a container whose entire container is made of a metallic material, a container with a multi-layered structure in which the innermost layer is made of a metallic material, or a container with a metallic membrane covering the liquid-contacting portion.

[0070] As a metallic material, it is preferably a metal selected from the group consisting of iron, copper, aluminum, stainless steel, titanium, nickel, zinc, tin, brass, magnesium, chromium, lead, silver, tungsten, niobium, molybdenum and tantalum; an alloy containing at least one of the metals selected from the above group; or a compound containing at least one of the metals selected from the above group.

[0071] Examples of alloys include nickel-chromium plating, solder, and tin plating.

[0072] Examples of compounds containing metals include aluminum sulfate, zinc phosphate, and iron phosphate.

[0073] For containers, the container body and the parts in contact with the crude product can be made of different materials. Examples of materials that make up the container body include iron (steel), stainless steel, carbon steel, manganese steel, chromium-molybdenum steel, other low-alloy steels, aluminum alloys, and glass. Examples of stainless steels include SUS316, SUS304, and JFE443CT.

[0074] The shape and size of containers can be designed according to their purpose. Examples include storage tanks as fixed preservation containers, transportable containers, and conveying containers. Transportable containers include 1L glass bottles, 20L pails, 200L drums, ton containers, aerosol cans, and high-pressure gas containers (including containers that cannot be refilled, welded containers, and seamless containers). Conveying containers include tank trucks, ISO containers, and automatic loaders.

[0075] Containers can also be airtight. There are no particular limitations on the method of sealing a container; for example, methods such as sealing with a threaded cap or a valve can be used. Elastic components such as cushioning materials or sealing materials that improve airtightness can also be used.

[0076] Materials used as elastic components include, for example, styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), ethylene propylene rubber (EPM), polyurethane rubber (U), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluororubber (FKM) with carbon-hydrogen bonds in a portion of the main chain, perfluorinated elastomers with a fully fluorinated main chain, chlorinated polyethylene (CM), acrylic rubber (ACM), polysulfide rubber (T), epichlorohydrin rubber, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, ester-based thermoplastic elastomers, urethane-based thermoplastic elastomers, amide-based thermoplastic elastomers, PVC-based thermoplastic elastomers, and fluorinated thermoplastic elastomers.

[0077] In the VdF manufacturing method disclosed herein, the increase in acidity of the crude product containing VdF obtained in the reaction process is suppressed, so even if it is supplied to a container in which at least a portion of the component in contact with the crude product is made of a metallic material, the container is not easily corroded. Therefore, after the crude product is supplied to the aforementioned container, it can be stored or transported for a long period of time.

[0078] The method for manufacturing VdF disclosed herein may further include a step of obtaining c354 using a feedstock composition A comprising at least one of the group consisting of TFE, R22 and c318 and containing ethylene.

[0079] Previously, VdF was synthesized, for example, via the dehydrochlorination reaction of 1-chloro-1,1-difluoroethane (142b). 142b is synthesized from ethylene or acetylene through a multi-stage process involving chlorination and fluorination. The chlorine and hydrogen fluoride gases used in the reaction are difficult to handle, and the process is lengthy. Therefore, a simpler manufacturing method using readily available raw materials is desired.

[0080] In contrast, the VdF manufacturing method disclosed herein can use raw materials with fewer reaction steps and easier processing to manufacture VdF.

[0081] Example

[0082] The present disclosure will be specifically described below through embodiments, but the present disclosure is not limited to these embodiments.

[0083] [Example 1]

[0084] use Figure 1 The reaction apparatus shown uses C354 and water vapor to obtain VdF by the method described below.

[0085] C354 is supplied from tank 1 to preheater 8 via C354 supply line 2. C354 is heated to 80°C using oven 4.

[0086] C354 is continuously introduced into the Inconel 600 tube in the preheater 8, where the furnace temperature is set to 250°C (the “preheating temperature” in the table), and heated to 250°C.

[0087] In addition, nitrogen is supplied from nitrogen tank 5 to preheater 9 via nitrogen supply line 6. A small amount of nitrogen is supplied to prevent high-boiling-point C354 from liquefying in reactor 10, which would cause backflow and liquid accumulation.

[0088] C354, which is preheated and adjusted to the above temperature, is supplied to reactor 10, which is managed with an internal pressure (gauge pressure) of 0 MPaG and an internal temperature of 700°C.

[0089] Inside the reactor, the flow rates of C354 and nitrogen (supply per unit time) are controlled so that the contact time between the feed gas and nitrogen is 5.0 seconds.

[0090] The gas supply is adjusted by the C354 flow control device 3 and the nitrogen flow control device 7.

[0091] The outlet gas discharged from reactor 10 contains, in addition to gases generated or produced by the reaction, unreacted raw material composition.

[0092] The outlet gas is recovered via the outlet gas supply / cooling line 11 and stored in the gas tank 12. After cooling to below 100°C and separating the water vapor, a crude product is obtained. The crude product is analyzed using an analytical apparatus 13 (gas chromatography). The analytical results are shown in Table 1 along with the reaction conditions.

[0093] In addition, the molar composition of the crude product was derived from the gas chromatography analysis results. At this time, it was calculated based on the gas chromatography relative sensitivity of each component listed in Table 1, with the total of the components listed in Table 1 being 100 mol%.

[0094] [Examples 2~12]

[0095] Except for changes to the contact time, reactor temperature, raw material composition, and composition of the heat transfer gas shown in Tables 1 and 2, the reaction was carried out in the same manner as in Example 1. Examples 1-4, 6, 8-12 are exemplary cases, and Examples 5 and 7 are comparative examples.

[0096] In Tables 1 and 2, "water / c354" refers to the water content relative to the content of c354 on a mass basis. In Example 5, values ​​that significantly exceed 1000 ppm by mass are recorded as ">1000 ppm by mass".

[0097] In Table 2, "nd" indicates that the corresponding component was not detected.

[0098] [Table 1]

[0099]

[0100] [Table 2]

[0101]

[0102] The C354 used in Examples 1-4 and 6-12 was pre-distilled and purified. For the distilled and purified C354, the water content was determined using a Nittoseiko Analytech Co., Ltd. Karl Fischer moisture analyzer CA-310 model, employing the coulometric method. The result showed a water content of 42 ppm by mass. It should be noted that the water content in the nitrogen gas was below the detection limit. In Tables 1 and 2, "0" in the water column indicates that no water was subsequently added, and the raw material composition contained trace amounts of water from C354.

[0103] In Tables 1 and 2, “Added” in the water column means that water was added later, and the amount of water added was adjusted to become the value shown in the “Water / c354 (mass ppm)” column.

[0104] Furthermore, the acidity of the outlet gases from Examples 4 and 5 was analyzed using pH test paper UNIV (1-11) manufactured by Toyo Filter Paper Co., Ltd. The results showed that the pH in Example 4 was 4, while the pH in Example 5 was 1, confirming that limiting the amount of water could suppress the increase in outlet gas acidity. Additionally, an experiment was conducted at 850°C with a composition containing 85 mol% water vapor, and carbon monoxide and carbon dioxide were detected under these conditions. These oxygen-containing compounds are believed to originate from the oxygen contained in the large amount of water. Therefore, it is shown that in the VdF manufacturing method of this disclosure, the water content relative to the C354 content is 1000 ppm by mass or less, thus suppressing water-related side reactions.

[0105] Furthermore, in Example 6, the hydrogen fluoride content in the outlet gas was less than 0.5 ppm, and the pH was 4. In contrast, in Example 7, the hydrogen fluoride content in the outlet gas was more than 100 ppm, and the pH was 3. Examples 6 and 7 demonstrate that when the water content relative to the C354 content is less than 1000 ppm by mass, the increase in acidity is suppressed.

[0106] As can be seen from Examples 1 and 8, when the temperature inside the reactor is above 600℃, the VdF content in the crude product increases.

[0107] As can be seen from Examples 2 and 11, when the contact time between C354 and water is more than 1 second, the formation of ethylene is inhibited, which can reduce the ethylene content in the crude product.

[0108] It should be noted that in Example 11, the amount of ethylene produced as a heat medium gas with a boiling point lower than VdF increases, and there is a tendency for VdF to be lost along with ethylene during the distillation of the crude product.

[0109] In Example 9, the nitrogen content exceeds 10 mol% relative to the C354 content. Nitrogen is a low-boiling-point gas, so there is a tendency for VdF to be lost along with nitrogen during the distillation of the crude product.

[0110] It should be noted that the publications of Japanese Patent Application No. 2023-043649, filed on March 17, 2023, and Japanese Patent Application No. 2023-101233, filed on June 20, 2023, are incorporated herein by reference in their entirety. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent that each document, patent application, and technical standard is specifically and separately described and incorporated herein by reference.

Claims

1. A method for manufacturing vinylidene fluoride, comprising a reaction step of obtaining vinylidene fluoride using a raw material composition comprising 1,1,2,2-tetrafluorocyclobutane and water, wherein the water content relative to the 1,1,2,2-tetrafluorocyclobutane content is less than 1000 ppm by mass in the reaction step.

2. The method for manufacturing vinylidene fluoride according to claim 1, wherein, In the reaction process, the content of the heat medium gas is less than 10 mol% relative to the content of 1,1,2,2-tetrafluorocyclobutane.

3. The method for manufacturing vinylidene fluoride according to claim 1 or 2, wherein, The temperature inside the reactor used in the reaction process is above 600°C.

4. The method for manufacturing vinylidene fluoride according to claim 1 or 2, wherein, The contact time between 1,1,2,2-tetrafluorocyclobutane and water is more than 1 second.

5. The method for manufacturing vinylidene fluoride according to claim 1 or 2, wherein, The pressure inside the reactor used in the reaction process is below 0.6 MPaG.

6. The method for manufacturing vinylidene fluoride according to claim 1 or 2, further comprising: The process of supplying the crude product containing vinylidene fluoride obtained in the reaction process to a container in which at least a portion of the component in contact with the crude product is made of a metallic material. Or a process that allows it to flow through a flow path in which at least a portion of the component in contact with the crude product is made of a metallic material.

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