Method for producing perfluoroacyl peroxide

Abstract

To provide a method for producing a perfluoroacyl peroxide described as formula (1) having a bulky structure in high yield and high reaction conversion without causing hyperacid decomposition in hydrofluoroether having zero ozone depletion coefficient and a low global warming coefficient.SOLUTION: A method for producing a perfluoroacyl peroxide described as formula (1) includes: a process A of obtaining a mixed liquid from an aqueous solution of a basic alkali metal compound having a concentration of 11 to 13 mass%, an aqueous solution of hydrogen peroxide, and hydrofluoroether represented by CF3(CH2)mO(CF2)nH (m is an integer of 1 to 6, and n is an integer of 1 to 4.); a process B of dropping a perfluorocyclohexanecarbonyl halide to the mixed liquid controlled in liquid temperature to 5 to 10°C at a constant rate for 10 to 30 minutes to obtain a reaction liquid; and a process C of stirring the reaction liquid controlled in liquid temperature to 5 to 10°C for 60 to 90 minutes, wherein a preparation mole ratio in the reaction liquid is a range of 1.60 to 1.80 of the alkaline metal compound, 1.60 to 2.20 of hydrogen peroxide with respect to 1.00 of the perfluorocyclohexanecarbonyl halide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing perfluoroacyl peroxides. [Background technology]

[0002] Perfluoroacyl peroxides are primarily used as polymerization initiators for fluororesins. It is known that polymerization using perfluoroacyl peroxides allows the introduction of perfluoroacyl peroxide-derived structures at the polymer end. While typical linear perfluoroacyl peroxides react quickly, they use excess hydrogen peroxide as a raw material, and extending the reaction time is known to cause peracid decomposition. For this reason, they are produced at low temperatures and in a short time.

[0003] Non-Patent Document 1 and Patent Document 1 describe a method for producing a perfluoroacyl peroxide represented by the following formula (1). [ka]

[0004] In the methods described in Non-Patent Document 1 and Patent Document 1, the perfluoroacyl peroxide represented by formula (1) is reacted at a low temperature of -5°C, and CCl2FCClF2, CF3CF2CCl2H, or CClF2CF2CClFH is used as a fluorine solvent, but the use of more environmentally friendly solvents is desired. Patent Document 2 describes a method for continuously producing perfluoroacyl peroxide. However, due to its high reactivity, the molar ratio of each component used in the reaction is set to 1:1 perfluoroacyl halide, with the basic alkali metal compound in the range of 1.00 to 1.35 and the hydrogen peroxide or metal oxide in the range of 0.60 to 40, and the production is carried out under mild conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-49749 [Patent Document 2] International Publication No. 2010 / 117029 [Non-patent literature]

[0006] [Non-Patent Document 1] J.App.Polym.Sci,1999,72,1101-1108. Summary of the Invention [Problem to be solved by the invention]

[0007] Due to environmental regulations, the number of fluorinated solvents that can be used has been limited in recent years, and efforts are being made to switch to environmentally friendly solvents. Among these, efforts are being made to switch to hydrofluoroethers, which have zero ozone depletion potential and low global warming potential, in compliance with environmental regulations, while retaining the properties of fluorinated solvents. Perfluoroacyl peroxides are primarily used as polymerization initiators for fluororesins, but their low decomposition temperature is essential to ensure safety during production. To obtain the bulky perfluoroacyl peroxides of formula (1) in high yield, excess amounts of basic alkali metal and hydrogen peroxide must be used due to their lower reactivity compared to linear perfluoroacyl peroxides. However, prolonged reactions under such excessive conditions can easily lead to peracid decomposition, making it difficult to balance yield and safety. Furthermore, the reactivity of perfluoroacyl peroxides when synthesized under diluted conditions varies greatly depending on the type of fluorine solvent used. Furthermore, due to environmental regulations, in recent years there has been a shift to hydrofluoroethers, which retain the properties of fluorinated solvents but comply with environmental regulations by having zero ozone depletion potential and a low global warming potential. In view of the above circumstances, an object of the present invention is to provide a method for producing a perfluoroacyl peroxide represented by formula (1) having a bulky structure in a hydrofluoroether having an ozone depletion potential of zero and a low global warming potential, without causing peracid decomposition, with a high yield and a high reaction conversion. Peracid decomposition is generally known as a phenomenon in which foaming occurs after the acid chloride is consumed during synthesis under conditions in which an excess amount of alkali or hydrogen peroxide is used relative to the acid chloride. When peracid decomposition occurs, the temperature of the reaction system may rise rapidly, significantly reducing safety. [Means for solving the problem]

[0008] As a result of intensive research in light of the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a method for producing a perfluoroacyl peroxide according to formula (1), which includes steps A to C described below, and in which the molar ratios of the basic alkali metal compound and hydrogen peroxide in the reaction solution are in the range of 1.60 to 1.80, relative to 1.00 of perfluorocyclohexanecarbonyl halide, and 1.60 to 2.20, and have completed the present invention. That is, the present invention relates to the following [1] to [5].

[0009] [1] A method for producing a perfluoroacyl peroxide according to the following formula (1): Step A: obtaining a mixed solution from an aqueous solution of a basic alkali metal compound having a concentration of 11 to 13 mass %, an aqueous solution of hydrogen peroxide, and a hydrofluoroether represented by the following general formula (2); Step B: A step of adding perfluorocyclohexanecarbonyl halide dropwise to the mixed liquid at a constant rate for 10 to 30 minutes while controlling the liquid temperature to 5 to 10°C to obtain a reaction liquid; Step C: Stirring the reaction solution at a temperature of 5 to 10°C for 60 to 90 minutes; Including, A method for producing a perfluoroacyl peroxide, wherein the molar ratio of the basic alkali metal compound to hydrogen peroxide in the reaction solution is 1.60 to 1.80, and 1.60 to 2.20, per 1.00 of perfluorocyclohexanecarbonyl halide. [ka] CF3(CH2) m O(CF2) n H···(2) (In formula (2), m represents an integer of 1 to 6, and n represents an integer of 1 to 4.) [2] The method according to the above [1], wherein the perfluorocyclohexane carbonyl halide is perfluorocyclohexane carbonyl chloride. [3] The method for producing a compound according to the above [1] or [2], wherein the hydrofluoroether is CF3CH2O(CF2)2H. [4] The method according to any one of the above [1] to [3], wherein the concentration of the aqueous solution of the basic alkali metal compound is 11 to 13 mass %. [5] The method according to any one of the above [1] to [4], wherein the aqueous solution of the basic alkali metal compound is an aqueous solution of sodium hydroxide. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for producing a perfluoroacyl peroxide represented by formula (1) having a bulky structure in a hydrofluoroether having an ozone depletion potential of zero and a low global warming potential, without causing peracid decomposition, with a high yield and a high reaction conversion. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Method of producing perfluoroacyl peroxide] The present invention provides a method for producing a perfluoroacyl peroxide represented by formula (1), Step A: obtaining a mixed solution from an aqueous solution of a basic alkali metal compound, an aqueous solution of hydrogen peroxide, and a hydrofluoroether represented by the following general formula (2); Step B: A step of adding perfluorocyclohexanecarbonyl halide dropwise to the mixed liquid at a constant rate for 10 to 30 minutes while controlling the liquid temperature to 5 to 10°C to obtain a reaction liquid; Step C: Stirring the reaction solution at a temperature of 5 to 10°C for 60 to 90 minutes; Including, This is a method for producing perfluoroacyl peroxide, characterized in that the molar ratio of the basic alkali metal compound and hydrogen peroxide charged in the reaction liquid is 1.60 to 1.80, and 1.60 to 2.20, respectively, relative to 1.00 of perfluorocyclohexanecarbonyl halide. [ka] CF3(CH2) m O(CF2) n H···(2) (In formula (2), m represents an integer of 1 to 6, and n represents an integer of 1 to 4.)

[0012] <Process A> Step A in the method for producing a perfluoroacyl peroxide of the present invention is a step of obtaining a mixed solution from an aqueous solution of a basic alkali metal compound having a concentration of 11 to 13 mass%, an aqueous solution of hydrogen peroxide, and a hydrofluoroether represented by the following general formula (2): Examples of the basic alkali metal compound in the aqueous solution of the basic alkali metal compound include one or more compounds selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, and potassium carbonate. Among these, sodium hydroxide is preferred from the viewpoint of reactivity. That is, it is preferable to use an aqueous solution of sodium hydroxide as the aqueous solution of the basic alkali metal compound.

[0013] The concentration of the aqueous solution of the basic alkali metal compound is 11 to 13 mass %, preferably 11.5 to 12.5 mass %. When the concentration of the aqueous solution of the basic alkali metal compound is within this range, the yield and reaction conversion rate can be increased in the production of the perfluoroacyl peroxide of formula (1).

[0014] The concentration of the aqueous hydrogen peroxide solution used in step A is not particularly limited, but is preferably 20 to 80% by mass, more preferably 30 to 75% by mass, and even more preferably 50 to 70% by mass.

[0015] The fluorine solvent used in step A is a hydrofluoroether represented by the following general formula (2). CF3(CH2) m O(CF2) n H···(2) (In formula (2), m represents an integer of 1 to 6, and n represents an integer of 1 to 4.)

[0016] The hydrofluoroether of formula (2) is a hydrofluoroether with zero ozone depletion potential and low global warming potential, and is a solvent with little environmental impact. The hydrofluoroether of general formula (2) is a compound with a global warming potential of 1,000 or less. The global warming potential is a numerical value that represents the ratio of the degree to which a greenhouse gas causes global warming to that of carbon dioxide (CO2), and is stipulated in the Enforcement Order of the Act on Promotion of Measures to Cope with Global Warming. In formula (2), from the viewpoint of the solubility of the perfluoroacyl peroxide, m is preferably an integer of 1 to 3, more preferably an integer of 1 or 2, and even more preferably 1. Furthermore, n is preferably an integer of 1 to 3, and more preferably 2. That is, the hydrofluoroether of formula (2) is preferably CF3CH2O(CF2)2H.

[0017] In step A, a mixed solution is obtained by mixing the above-mentioned aqueous solution of a basic alkali metal compound, an aqueous solution of hydrogen peroxide, and the hydrofluoroether represented by formula (2). The mixing ratio of the aqueous solution of the basic alkali metal compound, the aqueous solution of hydrogen peroxide, and the hydrofluoroether represented by formula (2) is not particularly limited, but may be adjusted appropriately so that the molar ratio of perfluorocyclohexanecarbonyl halide, the basic alkali metal compound, and the hydrogen peroxide in the reaction solution in step B described below falls within a specific range described below.

[0018] <Process B> Step B in the method for producing a perfluoroacyl peroxide of the present invention is a step of obtaining a reaction solution by adding perfluorocyclohexanecarbonyl halide dropwise to the mixed solution, the temperature of which is controlled to 5 to 10°C, at a constant rate for 10 to 30 minutes.

[0019] In step B, perfluorocyclohexanecarbonyl halide and hydrogen peroxide are reacted in an organic solvent (the hydrofluoroether represented by formula (2)) in the presence of a basic alkali metal compound. Because the reaction is carried out in an organic solvent, the reaction is carried out in a state in which two phases, an aqueous solution and an organic solvent, coexist, although this depends on the amount of organic solvent used.

[0020] In step B, the mixed solution prepared in step A is used. The temperature of the mixed solution is controlled to 5 to 10°C. If the mixed solution temperature is lower than 5°C, the reaction conversion rate decreases in the production of the perfluoroacyl peroxide of formula (1). On the other hand, if the mixed solution temperature is higher than 10°C, the yield decreases in the production of the perfluoroacyl peroxide of formula (1). The temperature of the mixture is preferably 7 to 10°C, and more preferably 8 to 10°C.

[0021] In step B, perfluorocyclohexanecarbonyl halide is added dropwise to the mixed solution. Examples of perfluorocyclohexanecarbonyl halide include perfluorocyclohexanecarbonyl fluoride, perfluorocyclohexanecarbonyl chloride, and perfluorocyclohexanecarbonyl bromide. Among these, perfluorocyclohexanecarbonyl chloride is preferred from the viewpoint of availability.

[0022] The perfluorocyclohexanecarbonyl halide is added dropwise to the mixture at a constant rate for 10 to 30 minutes. If the addition time is less than 10 minutes, the yield of the perfluoroacyl peroxide of formula (1) and the reaction conversion rate will decrease. If the addition time is more than 30 minutes, the yield of the perfluoroacyl peroxide of formula (1) will decrease. The dropwise addition time is preferably 10 to 20 minutes, more preferably 10 to 15 minutes, from the viewpoint of increasing the yield. The term "constant rate" means that the rate of dripping does not fluctuate significantly during the dripping time. To drip at a constant rate, an appropriate dripping device may be used, and for example, a dripping funnel or the like may be used to drip at a constant rate.

[0023] As described above, a reaction liquid is obtained by adding perfluorocyclohexanecarbonyl halide dropwise to the mixed liquid. The molar ratio (charge molar ratio) of perfluorocyclohexanecarbonyl halide to basic alkali metal compound in the reaction liquid is 1.00 perfluorocyclohexanecarbonyl halide to 1.60 to 1.80 basic alkali metal compound. If the molar ratio of perfluorocyclohexanecarbonyl halide to basic alkali metal compound in the reaction solution is less than 1.60, the reaction conversion of the perfluoroacyl peroxide of formula (1) will decrease. On the other hand, if the molar ratio of perfluorocyclohexanecarbonyl halide to basic alkali metal compound in the reaction solution is more than 1.80, peracid decomposition will easily occur, and the yield of the perfluoroacyl peroxide of formula (1) will decrease. From the viewpoint of improving yield, the molar ratio (charge molar ratio) of perfluorocyclohexanecarbonyl halide to basic alkali metal compound in the reaction liquid is preferably 1.00 perfluorocyclohexanecarbonyl halide to 1.70 to 1.80 basic alkali metal compound.

[0024] The molar ratio (charge molar ratio) of perfluorocyclohexanecarbonyl halide to hydrogen peroxide in the reaction liquid is 1.00 perfluorocyclohexanecarbonyl halide to 1.60 to 2.20 hydrogen peroxide. If the molar ratio of perfluorocyclohexanecarbonyl halide to hydrogen peroxide in the reaction mixture is less than 1.60, the yield of the perfluoroacyl peroxide of formula (1) will decrease. On the other hand, if the molar ratio of perfluorocyclohexanecarbonyl halide to hydrogen peroxide in the reaction mixture is more than 2.20, peracid decomposition will occur easily, resulting in a decrease in the yield of the perfluoroacyl peroxide of formula (1). The molar ratio (charge molar ratio) of perfluorocyclohexanecarbonyl halide to hydrogen peroxide in the reaction liquid is preferably 1.00 perfluorocyclohexanecarbonyl halide to 1.60 to 2.00 hydrogen peroxide, from the viewpoint of improving yield.

[0025] <Process C> Step C in the method for producing a perfluoroacyl peroxide of the present invention is a step of stirring the reaction liquid, the liquid temperature of which is controlled to 5 to 10°C, for 60 to 90 minutes. The liquid temperature and stirring time of the reaction liquid in step C may also be referred to as the aging temperature and aging time, respectively.

[0026] The aging temperature in step C is 5 to 10° C. If the aging temperature is lower than 5° C., the reaction conversion rate of the perfluoroacyl peroxide of formula (1) decreases. On the other hand, if the aging temperature is higher than 10° C., the yield of the perfluoroacyl peroxide of formula (1) decreases. The aging time in step C is 60 to 90 minutes. If the aging time is less than 60 minutes, the yield of the perfluoroacyl peroxide of formula (1) and the reaction conversion rate decrease. On the other hand, if the aging time exceeds 90 minutes, the generated perfluoroacyl peroxide is decomposed by the basic alkali metal compound, resulting in a decrease in yield.

[0027] <Cleaning process> It is preferable to carry out a washing step after carrying out the above step C. Specifically, after carrying out step C, the organic phase and the aqueous phase are separated at room temperature (for example, 10 to 30°C), and the obtained organic phase is washed with water to obtain the perfluoroacyl peroxide of formula (1).

[0028] According to the above-described production method of the present invention, a perfluoroacyl peroxide having a bulky structure represented by formula (1) can be produced in a hydrofluoroether having an ozone depletion potential of zero and a low global warming potential, without peracid decomposition, with high yield and high reaction conversion.

[0029] The perfluoroacyl peroxide represented by formula (1) has a perfluorohexyl group, and therefore has a higher 10-hour selected half-life temperature than that of ordinary fluorine-based organic peroxides, and is therefore used as a radical polymerization initiator for general ethylenic polymerizable groups, and is particularly suitable as a polymerization initiator for fluorine-based monomers. [Example]

[0030] The present invention will be described in more detail below with reference to examples and comparative examples.

[0031] In the examples and comparative examples, the following solvents were used. AE-3000: Asahiklin AE-3000 manufactured by AGC Corporation CF3CH2O(CF2)2H PFH: Perfluorohexane C6F manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 14 AC-2000: Asahiklin AC-2000 C6F manufactured by AGC Corporation 13 H

[0032] Example 1 A 300 mL four-neck flask was charged with 55.6 g (0.15 mol) of 11% by weight NaOH aqueous solution and 170 g of CF3CHO(CF2)2H. While stirring and maintaining the liquid temperature at 10°C, 10.3 g (0.18 mol) of 60% by weight H2O2 aqueous solution was added to obtain a mixed solution. Further, while stirring, 17.5 g (0.09 mol) of perfluorocyclohexanecarbonyl chloride was added dropwise over 10 minutes while maintaining the liquid temperature at 10°C to obtain a reaction solution. After aging and stirring for 60 minutes while maintaining the liquid temperature at 10°C, the organic phase was separated from the aqueous phase, and the resulting organic phase was washed twice with 195 g of water. After washing, 192 g of the perfluoroacyl peroxide of formula (1) was obtained, with a yield of 83.1% and a reaction conversion of 96%.

[0033] <Examples 2-10, Comparative Examples 1-14> In each example and comparative example, the synthesis was carried out in the same manner as in Example 1, except that the solvent type, NaOH concentration, molar ratio of NaOH and H2O2, dropping time and temperature, and aging time and temperature were changed as shown in Table 1, to obtain the perfluoroacyl peroxide of formula (1).

[0034] <Evaluation method> The evaluations in the examples and comparative examples were carried out by the following methods.

[0035] <Peracid decomposition> During the reaction, if no foaming or heat generation of 5°C or more was observed in the system, it was marked as "Good", and if foaming or heat generation of 5°C or more was observed, it was marked as "Poor".

[0036] <Yield> The yield was calculated from the yield and purity of the perfluoroacyl peroxide of formula (1) and the theoretical yield. The purity was calculated from the theoretical amount of active oxygen measured. A yield of 80% or more was marked "Good", and a yield of less than 80% was marked "Poor". The amount of active oxygen was measured using the following method. Isopropanol, glacial acetic acid, and saturated potassium iodide solution were placed in a 200 mL flask. The sample was then weighed and left at room temperature. The sample was then titrated with sodium thiosulfate solution until the color disappeared, and the amount of active oxygen was calculated. The theoretical yield was calculated by adding the amount of solvent used to the theoretical yield of perfluoroacyl peroxide calculated from the amount of perfluorocyclohexanecarbonyl chloride used, as shown in formula (1).

[0037] <Reaction conversion rate> The reaction conversion rate was calculated from the amount of residual chlorine, the yield of the perfluoroacyl peroxide of formula (1), and the amount of perfluorocyclohexanecarbonyl chloride charged using the following formula.

number

[0038] [Table 1]

[0039] In Examples 1 to 10, in which the perfluoroacyl peroxide of formula (1) was produced by a production method satisfying the requirements of the present invention, no peracid decomposition occurred, and the yield was 80% or more and the reaction conversion was 95%. Furthermore, in Examples 1 to 10, the production was carried out in hydrofluoroether, which has zero ozone depletion potential and a low global warming potential, so the environmental load is low.

Claims

1. A method for producing a perfluoroacyl peroxide according to the following formula (1): Step A: obtaining a mixed solution from an aqueous solution of a basic alkali metal compound having a concentration of 11 to 13% by mass, an aqueous solution of hydrogen peroxide, and a hydrofluoroether represented by the following general formula (2); Step B: A step of adding perfluorocyclohexanecarbonyl halide dropwise to the mixed solution at a constant rate for 10 to 30 minutes while controlling the liquid temperature to 5 to 10°C to obtain a reaction solution; Step C: Stirring the reaction solution at a temperature of 5 to 10°C for 60 to 90 minutes; Including, A method for producing perfluoroacyl peroxide, characterized in that the molar ratio of the basic alkali metal compound and hydrogen peroxide in the reaction solution is 1.60 to 1.80, relative to 1.00 of perfluorocyclohexanecarbonyl halide, and 1.60 to 2.20, respectively. 【Chemical 1】 CF ３ (CH ２ ) ｍ O(CF ２ ) ｎ H・・・(2) (In formula (2), m represents an integer of 1 to 6, and n represents an integer of 1 to 4.)

2. The method according to claim 1, wherein the perfluorocyclohexane carbonyl halide is perfluorocyclohexane carbonyl chloride.

3. The hydrofluoroether is CF ３ CH ２ O (CF ２ ) ２ The method according to claim 1 or 2, wherein the compound is H.

4. 3. The method according to claim 1, wherein the aqueous solution of the basic alkali metal compound is an aqueous solution of sodium hydroxide.

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