JPH0380145B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing perfluorovinylcarboxylic acid ester. Perfluorovinyl carboxylic acid esters are useful as monomers for producing perfluorocarbon polymers, particularly perfluorocarbon cation exchange resins. Generally, a method of thermally decomposing a perfluorocarbon having an acid fluoride group is known as a method for introducing a vinyl group into a perfluorocarbon. Therefore, the following method can be considered as a method of utilizing the above reaction for producing the perfluorovinyl carboxylic acid ester. That is, the expression

By partially thermally decomposing the dicarboxylic acid fluoride represented by the formula,

A conceivable method is to produce a perfluorovinyl carboxylic acid ester by producing a compound represented by the formula and then esterifying the remaining acid fluoride groups with alcohol. However, with the above method, it is difficult to generate vinyl groups while selectively leaving one acid fluoride group, and the rate of generation (decomposition rate) of vinyl groups is fast. When attempting to produce perfluorovinylcarboxylic acid ester, a considerable amount of the raw material dicarboxylic acid fluoride remains, making it extremely difficult to obtain perfluorovinylcarboxylic acid ester in high yield. In addition, in the above method, it is also possible to esterify one of the acid fluoride groups of the dicarboxylic acid fluoride in advance to form a half ester, and then decompose it, but this method does not allow the selective production of half esters. The problem is that the yield is extremely low when based on dicarboxylic acid fluoride. The present inventors have conducted intensive research to develop a method for producing perfluorovinyl carboxylic acid ester in high yield, and have discovered that perfluorovinyl carboxylic acid ester can be obtained extremely easily by esterification of the dicarboxylic acid fluoride. The present inventors have discovered that perfluorovinylcarboxylic acid esters can be obtained extremely selectively by thermally decomposing dicarboxylic acid esters under specific conditions, leading to the completion of the present invention. That is, the present invention provides the formula (However, R ₁ and R ₂ are different or similar alkyl groups having 1 to 10 carbon atoms, m is an integer of 1 or more, l and n are 0
or 1 _, X ₁ and X ₂ are F or CF ₃ , and when X ₁ and
This is a method for producing perfluorovinyl carboxylic acid ester, which is characterized by heating at 450°C. The perfluorodicarboxylic acid ester used in the present invention may be obtained by any method, but generally, as described above, a method in which dicarboxylic acid fluoride is esterified by a known method is preferred. Furthermore, in the above formula, those in which R ₁ and R ₂ have 1 to 3 carbon atoms and m has 2 to 6 carbon atoms are particularly preferably used. Furthermore, in order to improve the polymerizability of the obtained perfluorovinylcarboxylic acid ester as a monomer, it is preferable that l or n be 1. Typical structural formulas of perfluorodicarboxylic acid esters used in the present invention are as follows: etc. In particular, perfluorodicarboxylic acid esters have a structure that forms double bonds by thermal decomposition, that is,

[Formula] or

Those having [Formula] at both ends are preferable because, as described later, the perfluorovinylcarboxylic acid ester produced can be further partially thermally decomposed to produce perfluorodivinyl in an arbitrary ratio. Note that although the above formula only exemplifies a methyl group as an ester group, other compounds such as ethyl and propyl groups may also be mentioned. In the present invention, the perfluorodicarboxylic acid ester described above is heated at a temperature of 150 to 450°C, preferably 200 to 450°C.
Heating at 350°C is extremely important to obtain a high yield of perfluorovinylcarboxylic acid ester. That is, if the heating temperature is higher than the above range, side decomposition of the raw material perfluorodicarboxylic acid ester is likely to occur, resulting in a problem that the yield of perfluorovinylcarboxylic acid ester is significantly reduced. Furthermore, if the heating temperature is lower than the above range, the thermal decomposition rate will drop significantly, and if the reaction is carried out for a long time under these conditions, the selectivity of the reaction will also drop, making it difficult to obtain perfluorovinyl carboxylic acid ester in high yield. I can't. Further, the heating time may be appropriately determined in consideration of the heating temperature and the like. Generally 0.1
A heating time of ~10000 seconds, preferably 1 to 1000 seconds is suitable. In the present invention, it is preferable to heat the perfluorodicarboxylic acid ester in the presence of an alkaline substance in order to accelerate the rate of thermal decomposition and efficiently carry out the reaction. As the alkaline substance, known substances used in decarboxylation reactions are preferably used. For example, oxides such as zinc oxide, calcium oxide, and silicon oxide, and carbonates such as sodium carbonate, potassium carbonate, and lithium carbonate are generally used. In the present invention, the method of heating the perfluorodicarboxylic acid ester is not particularly limited, but heating is generally performed in a gas phase or a liquid phase. However, from the viewpoint of ease of controlling heating temperature and heating time, a method in which the heating is carried out in a gas phase is preferable. To illustrate a typical embodiment, a perfluorodicarboxylic acid ester is vaporized under reduced pressure, normal pressure, or increased pressure and diluted with an inert gas such as nitrogen, argon, helium, etc., and then heated in a heating zone, e.g., a heated column. An example of this method is to pass the inside for an appropriate amount of time. In the above embodiment, it is preferable that the above-mentioned alkaline substance be present (filled) in the column. The gas that has passed through the column may be cooled and condensed, and the generated perfluorovinyl carboxylic acid ester may be separated if necessary. Although the mechanism of double bond formation in the present invention is not clear, analysis of the product after thermal decomposition revealed that carboxylic acid ester groups (

[Formula] However, it is presumed that R (representing R ₁ or R ₂ ) is broken and a double bond is formed between the two carbons connected to this. The perfluorovinyl carboxylic acid ester produced by the method of the present invention can be separated from unreacted substances, etc.
After purification, or as it is, or depending on the product, it may be further heated under the above heating conditions to decompose the perfluorocarboxylic acid ester, resulting in the formula CF ₂ = CF
−(O) _l --(-CF ₂ ) _P --(-O) _o --CF=CF ₂ (
However, l,
n is 0 or 1, p is an integer determined by thermal reaction), and the perfluorodivinyl compound may be used after being produced in an arbitrary ratio. Among the above embodiments, an embodiment in which the produced perfluorovinyl carboxylic acid ester is further decomposed to produce a perfluorodivinyl compound at an arbitrary ratio,
Since the mixture has a relationship of monomer and crosslinking agent to each other, it is suitable for producing a polymer. EXAMPLES Hereinafter, in order to explain the present invention more specifically, Examples will be shown, but the present invention is not limited to these Examples. Example 1 (1) Synthesis of perfluorocarboxylic acid ester Using 94 parts by weight of oxalyl fluoride, 10 parts by weight of cesium fluoride as a catalyst, and 200 parts by weight of tetraglyme as a solvent, 500 parts by weight of hexafluoropropylene oxide was added at 0°C. Parts by weight were reacted. After the reaction, the product is distilled to obtain perfluorovinylcarboxylic acid fluoride.

[Formula] was separated. The obtained perfluorovinylcarboxylic acid fluoride was esterified with an alcohol having an alkyl group shown in Table 1 to produce a perfluorovinylcarboxylic acid ester, which was separated and purified and used as a raw material. (2) Production of perfluorovinylcarboxylic acid ester The perfluorodicarboxylic acid ester obtained by the above method and nitrogen were each simultaneously supplied to a vaporization chamber maintained at 250°C to vaporize the perfluorodicarboxylic acid ester as a raw material. . The molar ratio of perfluorodicarboxylic acid ester/nitrogen was adjusted to 1/10. This gas was thermally decomposed by passing through a column filled with the alkaline substance shown in Table 1 and heated to the temperature shown in Table 1 for the residence time shown in Table 1. After the thermal decomposition, the gas was cooled, and the thermal decomposition products, raw materials, etc. were condensed and recovered. The raw material reaction rate and the selectivity of perfluorovinylcarboxylic acid ester were measured from the above condensate. The results are also shown in Table 1. The structure of each component was determined by IR and NMR. That is, when IR measurement of perfluorocarboxylic acid methyl ester was performed, it showed an absorption at 2950 cm ^-1 , indicating the presence of a CH group, and an absorption at 1780 cm ^-1 , indicating the presence of an ester group, indicating an absorption at 1840 cm ^-1 . Therefore, the existence of vinyl ether group, 1380
CF because it exhibits strong and wide absorption at ~930 cm ^-1
I was able to learn about the existence of bonds. Furthermore, by measuring ¹³ C-NMR,
Chemical shift value (δ,
ppm) 159.4, 147.5, 130.1, 118.4, 115.1,
A total of 7 peaks were shown at 100.9 and 53.6, and each peak can be assigned as follows. Through the above measurements, the perfluorovinylcarboxylic acid methyl ester of this example could be identified. In addition, for perfluorodivinyl ether,
IR measurement revealed the presence of a perfluorovinyl ether group at 1840 cm ^-1 and the presence of a C--F bond from the strong and broad absorption between 1380 cm ^-1 and 930 cm ^-1 . Furthermore, by measuring ¹³ C-NMR, a total of three peaks were observed at chemical shift values of 147.5, 130.1, and 115.4, which can be assigned as shown below. 130.0 115.3 ( _CF2 =CF-O- _CF2 ) _-2 147.5 Through the above measurements, perfluorodivinyl ether of this example could be identified.

【table】

[Table] Comparative example 1 Perfluorodicarboxylic acid fluoride

When [Formula] was thermally decomposed under the same thermal decomposition conditions as in Example 1, the results shown in Table 2 were obtained. Either perfluorodivinyl ether is produced by thermal decomposition or the raw material is recovered, and it is clear that it is not easy to produce perfluorovinylcarboxylic acid fluoride as the main component.

[Table] Example 2 In the same manner as in Example 1, twice the molar amount of hexafluoropropylene oxide was added to perfluorosuccinyl fluoride, and then esterified with anhydrous methanol to form a perfluorodicarboxylic acid ester. was synthesized. Next, this perfluorodicarboxylic acid ester raw material was thermally decomposed under the same thermal decomposition conditions as in Example 1, and the results shown in Table 3 were obtained.

[Table] ｜
A〓CF ₂ = CFO(CF ₂ ) ₄ OCFCOOCH ₃
B〓CF ₂ = CFO(CF ₂ ) ₄ OCF = CF ₂
Example 3 Into a 500 ml glass autoclave, 10 parts by weight of cesium fluoride and 100 parts by weight of tetraglyme were charged, followed by 100 parts by weight of FOCCF ₂ COF, and 100 parts by weight of hexafluoropropylene oxide were reacted at a reaction temperature of 0°C for one day. I let it happen. After that, by distillation

160 parts by weight of [Formula] (BP66-68°C) were obtained. Furthermore, by esterifying 100 parts by weight of this perfluorodicarboxylic acid fluoride with anhydrous methanol,

104 parts by weight of [Formula] was obtained. When this perfluorodicarboxylic acid ester was thermally decomposed under the same thermal decomposition conditions as Nos. 2 and 3 of Example 1, the results shown in Table 4 were obtained.

[Table] Example 4 Esterification of perfluoroazibonyl fluoride with anhydrous methanol
When CH ₃ OOCCF ₂ CF ₂ CF ₂ CF ₂ COOCH ₃ was thermally decomposed under the same thermal decomposition conditions as in Example 1, the results shown in Table 5 were obtained.

【table】

Claims (1)

[Claims] 1 formula (However, R ₁ and R ₂ are different or similar alkyl groups having 1 to 10 carbon atoms, m is an integer of 1 or more, l and n are 0
or 1, X ₁ and X ₂ are F or CF _{3 ,} and when X ₁ and A method for producing perfluorovinylcarboxylic acid ester. 2. The method according to claim 1, wherein the heating is performed in the presence of an alkaline substance.