Method for producing perfluoropyruvic acid fluoride dimer

Abstract

To provide a method for producing a perfluoropyruvic acid fluoride dimer with superior production efficiency and energy saving performance.SOLUTION: The present invention provides a method for producing a perfluoropyruvic acid fluoride dimer represented by formula (1), the method including a reaction step of reacting a perfluorooxirane represented by formula (2) with an aldehyde, wherein the aldehyde has a water content ranging from 140 to 5000 mass ppm prior to the reaction step, and in formula (1), two R1's are identical and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, and in formula (2), R1 has the same meaning as above.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing perfluoropyruvic acid fluoride dimer.

Background Art

[0002] Poly[perfluoro(2-methylene-4-methyl-1,3-dioxolane)] can be obtained by polymerizing perfluoro(2-methylene-4-methyl-1,3-dioxolane) derived from trifluoromethylpyruvic acid fluoride dimer. Poly[perfluoro(2-methylene-4-methyl-1,3-dioxolane)] is a promising polymer as a resin for gas separation membranes and the like.

[0003] Patent Document 1 discloses a method for producing perfluoropyruvic acid fluoride dimer, in which benzophenone and hexafluoropropylene oxide are reacted at 185°C for 4 hours.

[0004] Patent Document 2 discloses a method for producing perfluoropyruvic acid fluoride dimer, in which hexafluoropropylene oxide is continuously or intermittently supplied to ketones and / or aldehydes and reacted at 0°C to 200°C.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when the inventors prepared perfluoropyruvic acid fluoride dimer by the method described in Patent Document 2, it was found that the reaction sometimes required a longer time than the described time. Under such circumstances, from the viewpoints of improving production efficiency and energy saving, it is desired to develop a method for completing the reaction in a short time.

[0007] In view of the above, an object of the present invention is to provide a method for producing a perfluoropyruvic acid fluoride dimer excellent in production efficiency and energy saving.

Means for Solving the Problems

[0008] As a result of intensive studies, the inventors have found that the water content contained in aldehydes affects the reaction time. Specifically, the inventors have found that by setting the water content of the aldehydes used in the reaction step within a predetermined range, it is possible to shorten the reaction time and provide a method for producing a perfluoropyruvic acid fluoride dimer excellent in production efficiency and energy saving.

[0009] That is, one aspect of the present invention is as follows. [1] Formula (1):

Chemical formula

Chemical formula

Advantages of the Invention

[0010] According to one aspect of the present invention, in the reaction of perfluoroepoxide and aldehydes, by using aldehydes with a water content within a predetermined range before the start of the reaction, the reaction time can be shortened, and a method for producing a perfluoropyruvic acid fluoride dimer excellent in production efficiency and energy saving can be provided.

Embodiments for Carrying Out the Invention

[0011] In the method for producing a perfluoropyruvic acid fluoride dimer according to one aspect of the present invention, in the reaction of perfluorooxirane and aldehydes, aldehydes having a water content within a predetermined range are used before the start of the reaction. Thereby, it becomes possible to shorten the reaction time. Hereinafter, the above production method will be described in more detail.

[0012] [Method for producing perfluoropyruvic acid fluoride dimer] In one form of the above production method, aldehydes having a water content in the range of 140 mass ppm to 5000 mass ppm are charged into a pressure-resistant container, and perfluorooxirane is preferably supplied and reacted at a temperature of -20°C to 300°C, more preferably 0°C to 200°C (reaction step). In the present invention and this specification, the temperature described for the reaction is the liquid temperature of the reaction solution unless otherwise specified. Also, in the present invention and this specification, "~" means greater than or equal to the left number and less than or equal to the right number unless otherwise specified.

[0013] In the present invention and this specification, "aldehydes" means one kind of aldehyde or a mixture of two or more kinds of aldehydes. In the above production method, one or more kinds of aldehydes can be used for the reaction. Also, perfluorooxirane may be supplied to the aldehydes preferably at a temperature of 0°C to 100°C, more preferably 50°C to 100°C, to once generate a perfluorooxirane adduct of the aldehydes as an intermediate, and then the temperature is preferably raised to 100°C to 200°C, more preferably 120°C to 180°C, and at a temperature within such a range, preferably for 1 hour to 48 hours, more preferably for 10 hours to 30 hours, a reaction (aging step) is carried out to produce a perfluoropyruvic acid fluoride dimer. In the present invention and this specification, "aging" means maintaining the temperature of the reaction solution within a predetermined range, and the temperature of the reaction solution during aging may be a constant temperature or may change.

[0014] The perfluoropyruvic acid fluoride dimer produced by the above production method is represented by the following formula (1).

[0015] [Chem.]

[0016] In formula (1), the two Rs 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.

[0017] The perfluoroalkyl group having 1 to 6 carbon atoms may be linear or branched. The number of carbon atoms is 1 or more, and can be 2 or more. Also, the number of carbon atoms is 6 or less, and can also be 5 or less, 4 or less, or 3 or less. Specific examples of the perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoro-n-propyl group, a heptafluoro-isopropyl group, a nonafluoro-n-butyl group, a nonafluoro-isobutyl group, a nonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, a perfluoro(methoxymethyl) group, a perfluoro(ethoxymethyl) group, etc. As R 1 Among these, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoro-n-propyl group, and a nonafluoro-n-butyl group are preferable, and a trifluoromethyl group and a pentafluoroethyl group are more preferable.

[0018] Specific examples of the perfluoropyruvic acid fluoride dimer represented by formula (1) include 2,4,4-trifluoro-5-oxo-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(trifluoromethyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(pentafluoroethyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(heptafluoropropyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(nonafluorobutyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(undecafluoropentyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(tridecafluorohexyl)-1,3-dioxolane-2-carbonyl fluoride, etc. Among them, 2,4,4-trifluoro-5-oxo-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(trifluoromethyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(pentafluoroethyl)-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(heptafluoropropyl)-1,3-dioxolane-2-carbonyl fluoride, and 4-fluoro-5-oxo-2,4-bis(nonafluorobutyl)-1,3-dioxolane-2-carbonyl fluoride are preferred, and 2,4,4-trifluoro-5-oxo-1,3-dioxolane-2-carbonyl fluoride, 4-fluoro-5-oxo-2,4-bis(trifluoromethyl)-1,3-dioxolane-2-carbonyl fluoride, and 4-fluoro-5-oxo-2,4-bis(pentafluoroethyl)-1,3-dioxolane-2-carbonyl fluoride are more preferred.

[0019] In the above production method, a perfluorooxirane represented by the following formula (2) is used.

[0020]

Chem.

[0021] In formula (2), R 1 is synonymous with the above. That is, in formula (2), two R 1 are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms.

[0022] Regarding R 1 in formula (2), it is as described above for R 1 in formula (1). Regarding the specific examples of R 1 in formula (2), they are also as described above for R 1 in formula (1).

[0023] Specific examples of the perfluoroepoxide represented by formula (2) include 2,2,3,3-tetrafluoroepoxide, hexafluoropropylene oxide, 2,2,3-trifluoro-3-(pentafluoroethyl)epoxide, 2,2,3-trifluoro-3-(heptafluoropropyl)epoxide, 2,2,3-trifluoro-3-(nonafluorobutyl)epoxide, 2,2,3-trifluoro-3-(undecafluoropentyl)epoxide, 2,2,3-trifluoro-3-(tridecafluorohexyl)epoxide, etc. Among them, 2,2,3,3-tetrafluoroepoxide, hexafluoropropylene oxide, 2,2,3-trifluoro-3-(pentafluoroethyl)epoxide, 2,2,3-trifluoro-3-(heptafluoropropyl)epoxide, and 2,2,3-trifluoro-3-(nonafluorobutyl)epoxide are preferred, and 2,2,3,3-tetrafluoroepoxide, hexafluoropropylene oxide, and 2,2,3-trifluoro-3-(pentafluoroethyl)epoxide are more preferred.

[0024] As aldehydes applicable to the above manufacturing method, from the viewpoint of the yield of trifluoropyruvic acid fluoride dimer and the like, aldehydes having no hydrogen atom at the α-position of the carbonyl group are preferred, aromatic aldehydes are more preferred, electron-donating group-substituted aromatic aldehydes are still more preferred, and electron-donating group-substituted benzaldehydes are even more preferred. Specific examples of aldehydes include propionaldehyde, butyraldehyde, valeraldehyde, isovaleraldehyde, pivalaldehyde, 1-adamantanecarbaldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, 2-ethylbenzaldehyde, 3-ethylbenzaldehyde, 4-ethylbenzaldehyde, 2-methoxybenzaldehyde, 3-methoxybenzaldehyde, 4-methoxybenzaldehyde, 2-ethoxybenzaldehyde, 3-ethoxybenzaldehyde, 4-ethoxybenzaldehyde, 2-fluorobenzaldehyde, 3-fluorobenzaldehyde, 4-fluorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, 2-bromobenzaldehyde, 3-bromobenzaldehyde, 4-bromobenzaldehyde, 1-naphthaldehyde, 5-methoxy-1-naphthaldehyde, 5-chloro-1-naphthaldehyde, 2-naphthaldehyde, 5-methoxy-2-naphthaldehyde, 5-chloro-2-naphthaldehyde and the like. Preferred aldehydes include benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, 2-ethylbenzaldehyde, 3-ethylbenzaldehyde, 4-ethylbenzaldehyde, 2-methoxybenzaldehyde, 3-methoxybenzaldehyde, 4-methoxybenzaldehyde, 2-ethoxybenzaldehyde, 3-ethoxybenzaldehyde, 4-ethoxybenzaldehyde and the like. One or more kinds of aldehydes can be used in the reaction.

[0025] The amount of aldehydes used is preferably 0.8 to 1.2 molar equivalents, more preferably 0.8 to 1.0 molar equivalents, relative to 1 mole of the perfluoroepoxide represented by formula (2) used in the reaction.

[0026] In the above production method, the water content of the aldehydes before the reaction step is in the range of 140 to 5000 ppm by mass. When the water content is less than 140 ppm by mass, the reaction takes a long time. On the other hand, when the water content exceeds 5000 ppm by mass, reaction inhibition, yield reduction, and premature deterioration of the kettle may occur due to the generation of a large amount of hydrofluoric acid, which is not preferable. The water content is preferably in the range of 200 to 3000 ppm by mass, more preferably in the range of 500 to 3000 ppm by mass.

[0027] The "water content" in the present invention and this specification is the water content determined by water measurement, specifically measurement using a Karl Fischer moisture meter. In the present invention and this specification, the "water content of the aldehydes before the reaction step" can be, for example, the water content of the aldehydes immediately before being introduced into the reaction vessel in which the reaction with the perfluoroepoxide represented by formula (2) is carried out, that is, immediately before the reaction. The "water content of the aldehydes before the reaction step" is also referred to as the "water content of the aldehydes before the reaction". In the above production method, it is sufficient that the water content of the aldehydes before the reaction step is within the above range, and the water content of the aldehydes before the reaction step may or may not be actually measured. For aldehydes, moisture absorption from the storage atmosphere does not occur or is negligible.

[0028] When the water content of the aldehydes used is in the range of 140 to 5000 ppm by mass, it can be used as it is. When the water content of the aldehydes is outside the above range, the water content can be adjusted by dehydration or adding water. Examples of the dehydration method include a method using molecular sieves and distillation purification using a dehydrating agent. Also, the water used when adding water is not particularly limited, and for example, tap water, ion-exchanged water, or distilled water can be used.

[0029] The reaction step in the above manufacturing method can be carried out without a solvent, but one or more solvents such as toluene, ethylbenzene, xylene, mesitylene, isopropylbenzene, anisole, chlorobenzene, etc. may be mixed in any ratio and used. When using a solvent, the amount used is preferably in the range of 0.1 part by mass to 5.0 parts by mass with respect to 1.0 part by mass of the perfluorooxirane represented by formula (2) used in the reaction.

[0030] As post-treatment after the reaction step, after cooling to room temperature and depressurizing, a layer composed of unreacted aldehydes, a difluoromethyl compound by-produced by the reaction, and / or a mixture of solvents is separated and removed, whereby the target trifluoropyruvic acid fluoride dimer can be obtained. "Room temperature" in the present invention and this specification is, for example, a temperature in the range of 20°C to 25°C. Further, after the reaction step is completed, purification can be carried out as necessary, and the purification method is not particularly limited. For example, the trifluoropyruvic acid fluoride dimer can be purified by methods commonly used by those skilled in the art as purification methods such as distillation, solvent extraction, silica gel column chromatography, preparative thin-layer chromatography, preparative liquid chromatography, etc.

[0031] The trifluoromethylpyruvic acid fluoride dimer obtained by the above manufacturing method can be induced to perfluoro(2,4-dimethyl-2-fluoromethyl-1,3-dioxolane) by reacting according to the description in U.S. Patent No. 3308107, and further according to the description in Patent No. 4776536, after hydrolysis and preparation of a potassium salt, it can be induced to perfluoro(2-methylene-4-methyl-1,3-dioxolane) by decarboxylation.

Examples

[0032] Hereinafter, the present invention will be further described with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0033] In the following analysis, the following equipment was used. Gas chromatography: GC-2025 manufactured by SHIMADZU Karl Fischer moisture meter: Karl Fischer coulometric moisture meter AQ-2200A manufactured by HIRANUMA 19 19F NMR: AVANCE II 400 manufactured by BRUKER

[0034] [Reaction conversion rate] The analysis of the reaction solution in the following examples and comparative examples was carried out using gas chromatography (hereinafter referred to as "GC"). The conversion rate is defined by the following formula based on aldehydes. Conversion rate (%) = a / (a + b + c + d + e) × 100 a = GC area % of the following formula (7) b = GC area % of the following formula (3) c = GC area % of the following formula (4) d = GC area % of the following formula (5) e = GC area % of the following formula (6) where [Chemical formula]

[0035] [In the above formula, R 1 represents a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. R 2 represents an alkyl group or an aryl group which may be substituted with one or more substituents selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom.]

[0036] In the following examples and comparative examples, 4-methoxybenzaldehyde was introduced into the autoclave within 24 hours after measuring the moisture after adjusting the moisture as necessary.

[0037] [Example 1] The moisture content of 4-methoxybenzaldehyde was measured using a Karl Fischer moisture meter in advance, and the water content was 245 ppm by mass. Ion-exchanged water (0.073 g) was added to 4-methoxybenzaldehyde (28.014 g) with a water content of 245 ppm by mass and mixed to adjust the moisture. When the moisture content of the 4-methoxybenzaldehyde after moisture adjustment was measured, the water content was 2693 ppm by mass. Subsequently, 4-methoxybenzaldehyde (27.3 g, 200 mmol, water content 2693 ppm by mass) was charged into a 150 mL autoclave (pressure-resistant container) made of SUS316 equipped with a stirrer with a pressure resistance of 2 MPa and a raw material supply port, heated to 90 °C, and then hexafluoropropylene oxide (34.2 g, 206 mmol) was continuously supplied as a gas from the raw material supply port over 2 hours while maintaining the same temperature. After closing the raw material supply port and holding at the same temperature for 2 hours, the temperature was raised to 140 °C. After heating at 140 °C for 16 hours, it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by gas chromatography (GC), the conversion rate was 95.3%. Thereafter, the reaction solution was withdrawn, 37.6 g of the upper layer of the organic layer and 21.2 g of the lower layer of the fluoras layer were obtained. Benzotrifluoride was used as an internal standard substance 19 In the quantification by 19F NMR, 16.4 g (56.9 mmol) of the target trifluoropyruvic acid fluoride dimer was produced in the fluoras layer (yield 56.9% based on 4-methoxybenzaldehyde). The obtained product was a mixture of two diastereomers, and the ratio was 1 / 1 (molar ratio). 19 19F NMR (neat, 376 MHz) (isomer 1) δ 22.4, -81.4, -81.8, -122.9, (isomer 2) δ 22.3, -81.7, -81.8, -122.1.

[0038] [Example 2] The moisture content of 4-methoxybenzaldehyde was measured using a Karl Fischer moisture meter in advance, and the water content was 936 mass ppm. 4-Methoxybenzaldehyde (27.3 g, 200 mmol, water content 936 mass ppm) was charged into a 150 mL autoclave (pressure-resistant container) made of SUS316 equipped with a stirrer with a pressure resistance of 2 MPa and a raw material supply port, and after heating to 90 °C, hexafluoropropylene oxide (59.3 g, 357 mmol) was continuously supplied as a gas from the raw material supply port over 2 hours while maintaining the same temperature. After closing the raw material supply port and holding at the same temperature for 2 hours, the temperature was raised to 140 °C. After heating at 140 °C for 16 hours, it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by gas chromatography (GC), the conversion rate was 98.2%. Then, the reaction solution was withdrawn, 37.6 g of the upper layer of the organic layer and 18.4 g of the lower layer of the fluoras layer were obtained. Benzotrifluoride was used as an internal standard substance 19 In the quantification by 19F NMR, 13.4 g (46.4 mmol) of the target trifluoropyruvic acid fluoride dimer was produced in the fluoras layer (yield 46.3% based on 4-methoxybenzaldehyde).

[0039] [Example 3] The water content of 4-methoxybenzaldehyde was measured using a Karl Fischer moisture meter in advance, and the water content was 275 mass ppm. 4-Methoxybenzaldehyde (45.5 g, 334 mmol, water content 275 mass ppm) was charged into a 250 mL autoclave (pressure-resistant container) made of SUS316 equipped with a stirrer with a pressure resistance of 2 MPa and a raw material supply port, and after heating to 90 °C, hexafluoropropylene oxide (57.1 g, 344 mmol) was continuously supplied as a gas from the raw material supply port over 3 hours while maintaining the same temperature. After closing the raw material supply port and holding at the same temperature for 2 hours, the temperature was raised to 140 °C. After heating at 140 °C for 16 hours, it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by gas chromatography (GC), the conversion rate was 85.2%. The temperature was raised to 140 °C again, and after additional heating for 8 hours (total 24 hours), it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by GC, the conversion rate was 94.6%. Then, the reaction solution was withdrawn, 59.3 g of the upper layer of the organic layer and 40.6 g of the lower layer of the fluoras layer were obtained. Benzotrifluoride was used as an internal standard substance 19 In the quantification by 19F NMR, 27.1 g (94.1 mmol) of the target trifluoropyruvic acid fluoride dimer was produced in the fluoras layer (yield 56.3% based on 4-methoxybenzaldehyde).

[0040] [Comparative Example 1] Prior to moisture measurement of 4-methoxybenzaldehyde using a Karl Fischer moisture meter, the water content was 1606 ppm by mass. Potassium carbonate powder (30% by mass relative to 4-methoxybenzaldehyde) was added to 4-methoxybenzaldehyde with a water content of 1606 ppm by mass, and after standing for 72 hours, it was filtered. Molecular sieve 4A was added to the filtrate, and it was left standing for 72 hours for dehydration. When moisture measurement of the dehydrated 4-methoxybenzaldehyde was carried out, the water content was 139 ppm by mass. Subsequently, 4-methoxybenzaldehyde (31.1 g, 228 mmol, water content 139 ppm by mass) was charged into a 190 mL autoclave (pressure-resistant container) made of SUS316 equipped with a stirrer and a raw material supply port at 2 MPa, heated to 90 °C, and then hexafluoropropylene oxide (39.1 g, 235 mmol) was continuously supplied as a gas from the raw material supply port over 3 hours while maintaining the same temperature. After closing the raw material supply port and holding at the same temperature for 2 hours, the temperature was raised to 140 °C. After heating at 140 °C for 16 hours, it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by gas chromatography (GC), the conversion rate was 81.9%. The temperature was raised to 140 °C again, and after additional heating for 8 hours (total 24 hours), it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by GC, the conversion rate was 91.7%. The temperature was raised to 140 °C again, and after further additional heating for 8 hours (total 32 hours), it was cooled to room temperature, the reaction solution was sampled, and as a result of analysis by GC, the conversion rate was 95.9%. Thereafter, the reaction solution was withdrawn, and 40.5 g of the upper layer of the organic layer and 27.0 g of the lower layer of the fluoras layer were obtained. Benzotrifluoride was used as an internal standard substance 19 In the quantification by 19F NMR, 17.6 g (60.9 mmol) of the target trifluoropyruvic acid fluoride dimer was formed in the fluoras layer (yield 53.3% based on 4-methoxybenzaldehyde).

[0041] [Comparative Example 2] Prior to the experiment, Karl Fischer moisture meter was used to measure the water content of 4-methoxybenzaldehyde, and the water content was found to be 245 ppm by mass. Ion-exchanged water (0.283 g) was added to 4-methoxybenzaldehyde (28.004 g, water content 245 ppm by mass) and mixed to adjust the water content. After the water content adjustment, the water content of 4-methoxybenzaldehyde was measured and found to be 9873 ppm by mass. Subsequently, 4-methoxybenzaldehyde (27.3 g, 198 mmol, water content 9873 ppm by mass) was charged into a 150 mL autoclave (pressure-resistant container) made of SUS316 equipped with a stirrer and a raw material supply port at 2 MPa, heated to 90 °C, and then hexafluoropropylene oxide (34.1 g, 205 mmol) was continuously supplied as a gas from the raw material supply port over 2 hours while maintaining the same temperature. After closing the raw material supply port and holding at the same temperature for 2 hours, the temperature was raised to 140 °C. After heating at 140 °C for 16 hours, it was cooled to room temperature. After degassing, the contents were checked, and no fluoras layer was present and the target trifluoropyruvic acid fluoride dimer could not be obtained. Instead, only a purple solid had precipitated.

[0042] The results of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 are shown in Table 1. From the results shown in Table 1, the following points can be confirmed. When the water content of the aldehydes before the reaction is less than 140 ppm by mass, it takes an aging time exceeding 24 hours until the conversion rate reaches 94% or more. In contrast, when the water content of the aldehydes before the reaction is 140 ppm by mass or more, the conversion rate reaches 94% or more within an aging time of 24 hours. On the other hand, when the water content of the aldehydes before the reaction is 9873 ppm by mass or more, the target product cannot be obtained.

[0043]

Table 1

[0044] The perfluoropyruvic acid fluoride dimer obtained according to one aspect of the present invention can be used as a synthetic raw material such as a resin for a gas separation membrane.

Claims

1. Formula (1): 【Chemical 1】 [In formula (1), two Rs １ are the same and represent a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. ] A method for producing a perfluoropyruvic acid fluoride dimer represented by Formula (2): 【Chemical Formula 2】 [In formula (2), R １ has the same meaning as described above. ] comprising a reaction step of reacting a perfluoroepoxide represented by with aldehydes, The method for producing a perfluoropyruvic acid fluoride dimer, wherein the water content of the aldehydes before the reaction step is in the range of 140 ppm by mass to 5000 ppm by mass.

2. The method for producing a perfluoropyruvic acid fluoride dimer according to Claim 1, wherein the water content of the aldehydes is in the range of 200 ppm by mass to 3000 ppm by mass.

3. The method for producing a perfluoropyruvic acid fluoride dimer according to Claim 1 or Claim 2, wherein in the reaction step, the perfluoroepoxide represented by Formula (2) and aldehydes are reacted at 0°C to 100°C.

4. The method for producing a perfluoropyruvic acid fluoride dimer according to Claim 1 or Claim 2, having an aging step of aging at 100°C to 200°C after the reaction step.

5. The method for producing a perfluoropyruvic acid fluoride dimer according to Claim 1 or Claim 2, wherein the aldehydes are aromatic aldehydes.

6. The method for producing a perfluoropyruvic acid fluoride dimer according to Claim 5, wherein the aromatic aldehyde is 4-methoxybenzaldehyde.

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