RU2213730C1 - Method for preparing perfluoro-2-methyl-3-oxahexanoylperoxide - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to preparing perfluoro-2-methyl-3-oxahexanoylperoxide that is used as an initiating agent in radical copolymerization of fluorinated olefins. Perfluoro-2-methyl-3-oxahexanoic acid fluoroanhydride is mixed with an perfluoropropylvinyl ester using as an organic solvent. Aqueous solutions of hydrogen peroxide and sodium hydroxide (preferably as 5-10%) are fed to mixture by separate currents simultaneously in cooling being preferably in the range of temperature from 0 to 5 C. The ratio of total volume of aqueous solutions to the mixture volume = (0.57-1.84) : 1 being the parent reagents are taken in the mole ratio hydrogen peroxide : sodium hydroxide : fluoroanhydride = (1.5- 2.5) : (2.0-2.5) : 1, respectively. Method provides simplifying isolation of the end substance, to improve its quality and to enhance safety and yield of product. EFFECT: improved preparing method. 5 cl, 2 tbl, 12 ex

Description

 The invention relates to the field of organic chemistry, and in particular to methods for producing perfluorinated diacyl peroxide obtained on the basis of hexafluoropropylene oxide - perfluoro-2-methyl-3-oxahexanoyl peroxide (PFOG), which is intended for use as an initiator for the radical copolymerization of fluorinated olefins.

A known method for producing perfluorodipropionyl peroxide obtained on the basis of hexafluoropropylene oxide, comprising contacting percarboxylic acid fluoride, namely perfluoropropionyl fluoride, organofluoric acid (FA) with an aqueous solution of an inorganic peroxide in liquid fluorinated hydrocarbon: 113 at + 15 ^° C, for example, moreover, the contacting is carried out by feeding perfluoropropionyl fluoride into the contact mass formed by mixing freon 113 and 30% by weight aqueous solutions of peroxide hydrogen sulfide and sodium hydroxide in a volume ratio of 1: (0.05-0.12): (0.05-0.15) with the addition of sodium chloride (to reduce the freezing temperature of the mass) with vigorous stirring with heat dissipation (RF patent 2154057 , class C 07 C 407/00, 409/16, publ. 10.08.2000). The chemistry of the process consists in the action of sodium peroxide at the time of its formation on perfluoropropionyl fluoride introduced into the reaction medium. A solution of perfluorodipropionyl peroxide in chladone 113 is obtained with a concentration of 57-150 g / l (3.6-9.4 wt.%) And an organic yield of 74.2-80.8%. The above method has disadvantages. Due to the high concentration of aqueous solutions of reagents, the by-product formed in the process - sodium fluoride - is released in solid form at the interface between the aqueous and organic phases, complicating the separation of the aqueous and organic layers, which leads to product losses. In addition, the use of concentrated solutions leads to a sharp heating of the reaction mass, complicates the process, requires more powerful cooling and introduction of sodium chloride into the reaction medium to reduce the freezing temperature of the mixture, which additionally pollutes the wash and waste water. In addition, working with concentrated solutions of hydrogen peroxide and sodium hydroxide is dangerous and requires special precautions.

 In addition to using classical synthesis in an aqueous-organic medium, methods are known for producing perfluorodiacyl peroxides in non-aqueous solvents. The authors of these methods believe that the presence of water promotes the formation of an organic acid resulting from the hydrolysis of fluorohydride, as well as peracid or acid formed during the hydrolysis of diacyl peroxide. In addition, the water remaining in the peroxide can cause corrosion of the equipment used for polymerization, since hydrogen fluoride is formed during the hydrolysis of the fluoride hydride. Water complicates the removal and purification of the solvent used in the polymerization.

A known method of producing diacyl peroxides, including perfluoro-2-methyl-3-oxahexanoyl peroxide (PFOG), in liquid or supercritical carbon dioxide by contacting the fluorohydride with a peroxide complex, taken in a 2-4-fold excess with respect to the fluorohydride, and peroxide the complex is introduced into the polymerization medium in the form of a solid phase, and cooling is carried out to a temperature of from -40 to +40 ^o With subsequent filtration of the organic phase to separate the excess peroxide complex (US Pat. EP 1157988, publ. 28.11.2001). In a special steel autoclave with a capacity of 300 ml, preliminarily dried with nitrogen for several hours at a temperature of 100 ^° C, 2 g (12.7 mmol) of dry sodium percarbonate (Na ₂ CO ₃ 11/2 H ₂ O ₂ ) are placed. The autoclave is closed, vacuum and cooled to -20 ^o C. 5.2 ml (24.7 mmol) of hexafluoropropylene oxide dimer fluoride are placed in a special steel cylinder, cooled with dry ice, vacuum and 220 g of carbon dioxide CO ₂ are placed in it . The cylinder is connected to the autoclave with a special steel tube with a diameter of 3.2 mm, invert and pour 199 g of liquid (FA) into the autoclave. The contents of the autoclave are stirred at a speed of 5000 rpm for 4 hours at a temperature of 0 ^o C, while the temperature in the autoclave is maintained in the range from -2 ^o C to 0.5 ^o C, and the pressure varies from 3.29 MPa to 3, 59 MPa. Then the contents of the autoclave with stirring are cooled to -27 ^o C, while the pressure drops to 1.27 MPa. The contents of the autoclave are transferred to a cylinder evacuated and cooled by liquid nitrogen. After transferring the mixture, the pressure in the cylinder is 0.2 atm (20 kPa). The cylinder was opened and 100 ml of 2,3-dihydroperfluoropentane (CF ₃ —CFHCHFCF ₂ CF ₃ ) was added to facilitate control of the peroxide yield. The cylinder is removed from the bath with nitrogen, slowly heated to room temperature and CO _{2 is} evaporated by pressure drop (30-45 min). The contents of the cylinder in liquid form are poured into a polyethylene bottle cooled by dry ice. The resulting liquid was washed three times with water at room temperature. The result is 85 ml of a liquid containing 41% peroxide. After opening, a solid white precipitate is detected on the walls of the autoclave, the weight of which approximately corresponds to the amount of sodium percarbonate initially added. The specified method has disadvantages: the presence of additional stages of preliminary drying of the autoclave and washing the obtained peroxide from the excess solid reagents used, which complicate and delay the process of obtaining the finished product. The high concentration of the resulting peroxide solution (41% by weight) complicates its use. It is known that the higher the concentration of the obtained peroxide solution, the less stable this solution during storage. Concentrated peroxide solutions are explosive and working with them requires special precautions. In addition, the preparation of peroxide in liquid carbon dioxide at a pressure of 32.9-35.9 atm requires the use of special equipment and increases the danger of the method.

The closest set of essential features to the proposed is a method for producing perfluoro-2-methyl-3-oxahexanoyl peroxide in an aprotic organic solvent, including in fluorinated ether - 2H-perfluoro-5-methyl-3,6-dioxanonan under cooling, including contacting fluoride with a peroxide complex, taken in excess with respect to the fluoride, moreover, the peroxide complex is introduced into the polymerization medium in the form of a solid phase, followed by filtration of the organic phase to separate the excess remaining peroxide complex (Pat. EP 1164130, publ. 28.11.2001). 50 ml of a solvent, 2H-perfluoro-5-methyl-3,6-dioxanonan and 2.0 g (13 mmol) of dry sodium percarbonate or (19 mmol) of an equivalent of H ₂ O _2, are placed in a round-bottom flask. After cooling to 0 ^{° C.} , 5.2 ml (25 mmol) of hydrofluoride are added to the contents of the flask. The resulting mixture was stirred with a magnetic stirrer for 3 hours. The reaction mass is filtered through a desiccant - calcium sulfate on glass wool to remove residues of unreacted sodium percarbonate or H ₂ O ₂ . 0.18 M peroxide was determined in the filtrate, assuming that the product volume was 55 ml, this represents a 79% yield of peroxide to the starting organic fluoride. The known method has the following disadvantages. In this method, a ready-made peroxide complex (sodium peroxydicarbonate) is used, it is taken in excess from stoichiometry with respect to the starting fluorohydride, and since it is proposed to use peroxide complexes insoluble in aprotic solvents in the solid phase, quite a result is required for contacting the peroxide complex and fluorohydride a long time. In addition, it becomes necessary to introduce an additional filtration step for the resulting diacyl peroxide, which complicates the known method and increases its danger.

 The technical task of the present invention is to reduce the contact time of the peroxide complex with fluoride and to simplify the process of producing perfluoro-2-methyl-3-oxahexanoyl peroxide.

 The problem is solved by the method of producing perfluoro-2-methyl-3-oxahexanoyl peroxide (PFOG), including contacting with cooling of perfluoro-2-methyl-3-oxahexanoic acid fluoride (PA) with peroxide in an organic solvent, according to the invention, contacting is carried out with an aqueous solution of peroxide hydrogen and sodium hydroxide, perfluoropropyl vinyl ether is used as an organic solvent, and contacting is carried out by simultaneously supplying aqueous solutions of hydrogen peroxide and sodium oxide in the contact mass formed by mixing the fluoride of perfluoro-2-methyl-3-oksageksanovoy acid with perfluoropropylvinylether.

 Contacting is carried out with the ratio of the total volume of aqueous solutions to the volume of contact mass (0.57-1.84): 1.

 Preferably, 5-10% (by weight) aqueous solutions of hydrogen peroxide and sodium hydroxide are used.

 The starting reagents take in a molar ratio hydrogen peroxide: sodium hydroxide: fluorohydride (1.5-2.5): (2.0-2.5): 1.

Contacting is carried out in the temperature range from 0 to 5 ^o C.

 The method was tested in laboratory conditions.

PRI me R 1. Perfluoro-2-methyl-3-oxaperfluorohexanoyl peroxide (PFOG) is obtained in a round-bottomed four-necked flask equipped with a stirrer, a thermometer and two dropping funnels for supplying reagents. 100 ml (0.59 mol) of perfluoropropyl vinyl ether (PFPE) was charged into the flask, it was cooled to a temperature of -10 ^° C and 16 ml (0.075 mol) of perfluoro-2-methyl-3-oxaperfluorohexanoic acid fluoride was added to the flask. 49.1 ml of hydrogen peroxide and 54.1 ml of sodium hydroxide in the form of 10% (by weight) aqueous solutions, which is 0.15 each, are fed into the obtained contact mass with a temperature of -10 ^° C with vigorous stirring simultaneously from two dispensers mole of each reagent. The volumetric ratio of the aqueous phase to the organic contact mass is 0.89: 1, and the molar ratio of the starting reagents is hydrogen peroxide: sodium hydroxide is 2: 2: 1. The supply of reagents is carried out at such a speed that the temperature of the reaction mass does not exceed +5 ^o C. After the end of the supply of reagents, stirring of the reaction mass is continued for 1 h at a temperature of 0 ^o C. Then the reaction mass is transferred to a separatory funnel, sedimented and the lower organic a layer representing a solution of the obtained peroxide in perfluoropropyl vinyl ether from an aqueous solution of mineral substances. With sludge, the separation of layers occurs almost instantly, the boundary of the layers is very clear, washing of the organic product is not required. 19.7 g of PFOG are obtained in the form of a 10.8% (by weight) solution in PFPVE (analyzed by iodometric titration). The yield of the target product for organic raw materials is 80.0%. The resulting solution is used as an initiator in the copolymerization of tetrafluoroethylene (TFE) with perfluoropropyl vinyl ether, which is carried out as follows. A laboratory reactor with a capacity of 1.6 liters of chromium-nickel steel is used, equipped with a high-speed propeller stirrer (1500 rpm), a heating jacket, a dropper and a syringe device for introducing the initiator. The reactor is sealed, cooled to a temperature of -25 ^o C and vacuum to a residual pressure of 0.001 MPa. In a dropper cooled to the same temperature, 1 g of the obtained PFOG initiator is placed in the form of a 10.8% (by weight) solution in PFEPVE, 3.25 g of PFVVE are added, the dropper is sealed and its contents are poured into the reactor. Then, 600 g of liquefied octafluorocyclobutane (SFC) is charged into the reactor. The contents of the reactor with heating are heated to a temperature of 35 ^o C. 25 g of TFE are fed into the reactor and the monomers are copolymerized at a constant temperature and steady pressure, adding to the reactor a comonomer feed mixture containing 97 mol.% TFE and 3 mol.% PFPVE to the initial pressure each time with a decrease in pressure of 0.02 MPa. The copolymerization process is carried out until 170 g of the make-up mixture is consumed for 3.7 hours. Then the reaction is stopped by stopping the stirrer and blowing off the unreacted monomers in a pre-cooled and evacuated container. The copolymer is degassed by heating under vacuum, the reactor is cooled and opened. The resulting copolymer is heated for another 24 hours at 120 ^o C and determine its properties. 190 g of a white powder of TFE copolymer with perfluoropropyl vinyl ether are obtained.

 The conditions for obtaining a solution of PFOG in a fluorine-containing organic solvent and the results of this and subsequent examples are summarized in table 1, and the results of copolymerization using the obtained initiator are shown in table 2.

 PRI me R 2. Get a solution of PFOG in PFPVE, as described in example 1, but using 5% (by weight) solutions of hydrogen peroxide and sodium hydroxide in the amount of 100.0 and 113.8 ml, respectively. With sediment, phase separation occurs rather quickly, the boundary of the layers is clear, washing of the organic product is not required. Obtain 17.2 g of PFOG in the form of a 9.4% (by weight) solution in PFPVE.

PRI me R 3. Get a solution of PFOG in PFPVE, as described in example 1, but using 15% (by weight) solutions of hydrogen peroxide and sodium hydroxide in the amount of 32.0 and 34.3 ml, respectively. When sedimentation, phase separation occurs satisfactorily, the layer boundary is fuzzy, a slight haze appears, which is eliminated by washing the organic product with water at a temperature of +5 ^o C. Receive 17.3 g of PFOG in the form of a 9.5% (by weight) solution in PFPVE.

 PRI me R 4. Get a solution of PFOG in PFPVE, as described in example 1, but 10% solutions of hydrogen peroxide and sodium hydroxide take in the amount of 36.7 and 67.4 ml, respectively. With sludge, phase separation occurs rather quickly, but the layer boundary is fuzzy, a slight haze appears, which is eliminated by washing the organic product with cold water. 16.8 g of PFOG are obtained in the form of a 9.1% (by weight) solution in PFPVE.

 PRI me R 5. The experiment is carried out as in example 4, but a solution of hydrogen peroxide is taken in the amount of 61.2 ml With sludge, phase separation occurs rather quickly, but the layer boundary is fuzzy, a slight haze appears, which is eliminated by washing, as in Example 4. 18.5 g of PFOG are obtained in the form of a 10.1% (by weight) solution in PFEPVE.

PRI me R 6. The experiment is carried out as described in example 1, but the supply of reagents is carried out at such a speed that the temperature of the reaction mass does not exceed 0 ^o , and at the end of the supply of reagents with stirring, the temperature is maintained at + 5 ^o C. phase separation occurs rather quickly, the boundary of the layers is clear, washing of the organic product is not required. Obtain 14.4 g of PFOG in the form of an 8% (by weight) solution in PFPVE.

 PRI me R 7 (control). The experiment is carried out as described in example 2, but 5% solutions of hydrogen peroxide and sodium hydroxide are taken in the amount of 26.0.0 and 56.1 ml, while the molar ratio of these reagents and fluorohydride corresponds to stoichiometric coefficients of the reaction equation 0.5 : 1: 1, but the layer boundary is fuzzy, a slight haze appears, which is eliminated by washing the organic product with cold water. Obtain 5.7 g of PFOG in the form of a 3.1% (by weight) solution in PFPVE.

 PRI me R s 8k-11k - control. These examples are carried out on the same equipment and in the same mode as described in example 1, using the starting materials in the same quantities and with the same concentrations as in example 1, but the feed order of the starting reagents is different from the sequence provided by the present invention .

 PRI me R 8k. In the contact mass obtained as described in example 1, a hydrogen peroxide solution, then a sodium hydroxide solution, is sequentially fed first. In sedimentary phase separation occurs slowly, the layer boundary is fuzzy, a white precipitate precipitates, and an intermediate layer is formed, including a precipitated solid phase. The organic layer is washed with cold water to remove solid inclusions of mineral salts. 12.3 g of PFOG are obtained in the form of a 6.8% (by weight) solution in PFPVE.

 PRI me R 9k. With stirring, first, a solution of sodium hydroxide, then a solution of hydrogen peroxide is successively charged into the reaction flask, the mixture is cooled, and a pre-prepared solution of perfluoro-2-methyl-3-oxahexanoic acid fluoride in perfluoropropyl vinyl ether is fed into the resulting contact mass. When defending the resulting reaction mass, phase separation occurs rather quickly, the layer boundary is clear, washing of the organic product is not required. 12.4 g of PFOG are obtained in the form of a 7.7% (by weight) solution in PFPVE.

 PRI me R 10k. PFEPVE was charged into the reaction flask, cooled and, with stirring, first a hydrogen peroxide solution was added, then a sodium hydroxide solution, then perfluoro-2-methyl-3-oxahexanoic acid fluoride was added. When defending the resulting reaction mass, phase separation occurs rather quickly, the layer boundary is clear, washing of the organic product is not required. Obtain 10.1 g of PFOG in the form of a 7.6% (by weight) solution in PFPVE.

 PRI me R 11k. The experiment is carried out, as in example 10k, but aqueous solutions of the reagents are served in a different sequence: first, a solution of sodium hydroxide, then a solution of hydrogen peroxide. When defending the resulting reaction mass, phase separation occurs rather quickly, the layer boundary is clear, washing of the organic product is not required. Obtain 10.3 g of PFOG in the form of a 6.6% (by weight) solution in PFPVE.

 PRI me R 12k. This example is carried out on the same equipment and in the same mode as described in example 1, using the starting materials in the same quantities and with the same concentrations as in example 1, but in the flask instead of PFPVE, as a solvent, load 100 ml ( 0.35 mol) - 2H-perfluoro-5-methyl-3,6-dioxanonan (as in the prototype). When defending the resulting reaction mass, phase separation occurs rather quickly, the layer boundary is clear, washing of the organic product is not required. 12.3 g of PFOG are obtained in the form of a 9% (by weight) solution in 2H-perfluoro-5-methyl-3,6-dioxanonan. The resulting solution is used as an initiator in the copolymerization process (TFE) with PFPE, which is carried out as described in Example 1, but the amount of PFPE added is 12.5 g. 150 g of a white copolymer powder are obtained.

 From the presented data it can be seen that the proposed method provides the production of perfluoro-2-methyl-3-oxahexanoyl peroxide with the desired concentration and suitable for producing a fluoropolymer. The use of aqueous solutions of hydrogen peroxide and sodium hydroxide, which are introduced into the contact mass by simultaneously feeding them into the contact mass, allows, in contrast to the prototype, to reduce the time of contacting the peroxide with fluorohydride, as well as to exclude the filtration stage, which makes it possible to simplify the process of producing perfluoroperoxide.

 The presented examples also show that the proposed method compared to the prototype is more economical, simpler and safer, since it is characterized by a high yield of the target product, does not require the use of additional stages of separation and washing of the product; the solid phase does not form in the method, there are no fractions with a high concentration of peroxides. All this is achieved by the proposed procedure for introducing reagents into the process, as well as by changing the molar ratio of the reactants and the volume ratio of the aqueous and organic phases.

 In the synthesis of PFOG in perfluoropropyl vinyl ether, the resulting initiator solution is most promising for use in the copolymerization of tetrafluoroethylene and other fluoroolefins with perfluoropropyl vinyl ether, since the copolymer obtained in this case has better thermal stability and physicomechanical properties (see table 2, example 1).

Claims (5)

 1. The method of producing perfluoro-2-methyl-3-oxahexanoyl peroxide, comprising contacting with cooling perfluoro-2-methyl-3-oxahexanoic acid fluoride with peroxide in an organic solvent, characterized in that the contacting is carried out with an aqueous solution of hydrogen peroxide and sodium hydroxide, perfluoropropyl vinyl ether is used as an organic solvent, and contacting is carried out by simultaneously supplying aqueous solutions of hydrogen peroxide and sodium hydroxide to the contact mass, image mixing bath fluoride of perfluoro-2-methyl-3-oksageksanovoy acid with perfluoropropylvinylether.  2. The method according to p. 1, characterized in that the contacting is carried out at a ratio of the total volume of aqueous solutions to the volume of the contact mass of 0.57-1.84: 1.  3. The method according to claim 1 or 2, characterized in that 5 to 10% by weight aqueous solutions of hydrogen peroxide and sodium hydroxide are used.  4. The method according to any one of claims 1 to 3, characterized in that the starting reagents take in a molar ratio of hydrogen peroxide: sodium hydroxide: fluorohydride: 1.5-2.5: 2.0-2.5: 1. 5. The method according to any one of claims 1 to 4, characterized in that the contacting is carried out in the temperature range from 0 to 5 ^o C.

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