RU2671812C1 - Method of obtaining perfluoro-3-oxapentenesulfonyl fluoride copolymer and tetrafluoroethylene as precursor of perfluorinated proton-conducting membranes - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to the field of the chemistry of high-molecular compounds. Method of obtaining a perfluoro-3-oxapentenesulfonyl fluoride copolymer and tetrafluoroethylene as a precursor of perfluorinated proton-conducting membranes by emulsion copolymerization consists in preparing an aqueous microemulsion of the first comonomer – perfluoro-3-oxapentenesulfonyl fluoride with an average particle size of 1,000 nm by the method of ultrasonic dispersion in an atmosphere of inert gas at a temperature of 20 °C with the volume ratio of the phases of comonomer: water 1:6–1:12 (monomer concentration of perfluoro-3-oxapentenesulfonyl fluoride 22.2–12.8 wt.%, 13.5–7.8 % by volume) in the presence of an emulsifier – perfluorinated surfactant in an amount of 2–3 wt. % relative to the comonomer perfluoro-3-oxapentenesulfonyl, component of the water-soluble redox system – potassium or ammonium persulfate in the amount of 0.85–1.2 wt. % relative to perfluoro-3-oxapentenesulfonyl fluoride and pH regulator to pH 7–8, then the microemulsion is loaded into the reactor in an inert gas atmosphere, the reactor is flushed with a second comonomer – tetrafluoroethylene to a pressure of 0.1 MPa, the microemulsion is stirred at 100 rpm and heated to an operating temperature of 40–50 °C, add another component of a water-soluble redox system – sodium metabisulfite in the amount of 0.26–0.30 wt. % relative to perfluoro-3-oxapentenesulfonyl fluoride, a redox system of two components is formed in a microemulsion, the stirring speed is set to 450 rpm and the copolymerization is carried out by feeding tetrafluoroethylene directly into the microemulsion by bubbling at a working pressure of tetrafluoroethylene 0.9–1.1 MPa with constant stirring of the reaction medium for 4.5–6.5 h with the formation of latex, the copolymerization process is completed with the conversion of perfluoro-3-oxapentenesulfonyl fluoride of 90–92 %, the latex is subjected to coagulation by freezing, followed by separation of the target copolymer from the liquid phase by filtration, the copolymer is washed from the starting materials with deionized water at 80–90 °C and dry under vacuum. Proposed technology allows to carry out the process of copolymerization to deep degrees of transformation of the first comonomer (more than 90 %) while maintaining the constancy of the composition of the resulting copolymer, regardless of the degree of conversion of the comonomer.EFFECT: mechanical properties of the resulting sulfonic acid membranes are not inferior to the mechanical properties of extruded unmodified Aquivion E-87membranes of Solvay Solexis brand.5 cl, 7 ex

Description

The claimed invention relates to the field of chemistry of macromolecular compounds, specifically to the preparation of proton conducting membrane precursors — perfluorinated copolymers with shortened side chain lengths containing sulfonyl fluoride groups, with improved performance properties. Membranes based on copolymers of this type are characterized by increased crystallinity, chemical and thermal resistance, good strength and increased electrochemical properties and can be used in hydrogen fuel cells with a higher operating temperature than standard Nafion membranes.

State of the art

A number of methods are known for producing copolymers of tetrafluoroethylene (TFE) with perfluoro-3-oxapentenesulfonyl fluoride (PFOPSF) of the structure FSO ₂ CF ₂ CF ₂ OCF = CF ₂ during the process in an aqueous emulsion of sulfonyl fluoride monomer.

According to a known method for emulsion copolymerization of PFOPSF with TFE [US Pat. 4940525, С25В 13/08, 07/10/1990] in the prepared aqueous solution of an emulsifier of ammonium perfluorooctanoate emulsifier and pH regulators - a mixture of mono- and disubstituted sodium phosphates at a temperature of 45 ° C and stirred with a turbine stirrer at a speed of 800 rpm, PFOPSF is obtained, obtaining an emulsion system , add an aqueous solution of a radical initiator of ammonium persulfate and carry out the process of copolymerization of TFE with PFOPSF at a temperature of 45 ° C and under a pressure of TFE in the range of 0.88-1.06 MPa for 4 hours (example No. 1 from the description of the invention in the patent). The copolymer is isolated from the obtained latex by coagulation with the addition of concentrated hydrochloric acid. To wash the copolymer from the emulsifier and salt solutions, 31.4 ml of water / g of the copolymer and 31.4 ml of methyl alcohol / g of the copolymer are used. The copolymer is dried under vacuum at 110 ° C.

The disadvantages of this method are:

1. A very low degree of conversion of PFOPSF (15%), leading to the loss of unregenerated expensive monomer.

2. A very high water content of the membranes obtained by this method: with an equivalent mass (EM) of 564 g / eq, 646 wt. %, with an EM equal to 675 g / eq, 103.2 wt. % (examples Nos. 2 and 6), which leads to the loss of mechanical properties during operation of the membranes.

According to a known method for emulsion copolymerization of PFOPSF with TFE [US Pat. 8357725, B01J 39/20, 01/22/2013] the process is carried out under a TFE pressure of 13.5 bar with potassium persulfate initiation at a temperature of 60 ° C using perfluoropolyoxyalkylene with a terminal carboxylate group in potassium form CF ₂ ClO (CF ₂ CF ( CF ₃ ) O) _n (CF ₂ O) _m CFCOOK and fractional supply of PFOPSF monomer during the process (example No. 1 from the description of the invention in the patent).

A copolymer of PFOPSF with TFE is isolated from the formed latex by freezing methods, washed from surfactant with water and dried in vacuum at 40-150 ° C. After alkaline hydrolysis of the copolymer and its translation into the membrane form, the EM copolymer is 890 g / equiv.

The disadvantages of this method are:

1. The use of significant quantities of emulsifier (4.3% by weight of loaded PFOPSF), which requires an increased amount of water to wash the copolymer from the emulsifier.

2. The presence in the resulting copolymer of unstable COF groups in an amount of 14 mmol / kg (example No. 1). To reduce the content of unstable groups in the copolymer by a factor of 3, additional drying at 100 ° C in a stream of dry helium is required after the standard procedure for isolating and drying the copolymer, followed by treatment (purging) with a nitrogen / fluorine mixture in a volume ratio of 1: 1 at 80 ° C for 12 h, which reduces the content of COF groups to 4.5 mmol / kg. The use of highly aggressive fluorine imposes special requirements on the materials in the equipment of the used plants, requires an increase in safety systems, and disposal of unreacted fluorine, which greatly complicates the technology.

A known method of copolymerization of PFOPSF with TFE [Pat. EP 1172382, C08F 14/18, C08F 2/16, 01/16/2002], where a mixture of a perfluoropolyoxyalkylene with a terminal carboxylate group in the potassium form CF ₂ CIO (CF ₂ CF (CF ₃ ) O) _n (emulsifiers is used to obtain a microemulsion) CF ₂ O) _m CF ₂ COOK and Galden ^® D02 perfluoropolyether of the formula CF ₃ O (CF ₂ CF (CF ₃ ) O) _n (CF ₂ O) _m CF ₃ . The microemulsion is obtained by simple mixing of the above emulsifiers. The process of copolymerizing TFE with PFOPSF is carried out in an autoclave by diluting the resulting microemulsion with water, adding PFOPSF monomer, initiator solution, stirring at 700 rpm, TFE pressure within 0.3-1.1 MPa, temperature 50-75 ° С, reaction pH medium in the range of 4-7, using potassium persulfate as a radical initiator, and thereby obtaining a copolymer with EM in the range of 494-768 g / equiv. The emulsion is copolymerized with constant feed of PFOPSF monomer during the process.

The disadvantages of this method are:

1. The use of a complex and inaccessible mixture of perfluorinated polyesters as a stabilizer for the resulting PFOPSF microemulsion.

2. The need for dosing of liquid aggressive components (PFOPSF) during the process under pressure, which complicates the technology.

3. Upon receipt of copolymers with EM 496-494 g / equiv (Examples Nos. 1 and 2), the membranes are characterized by very high water content (more than 500 wt.%.) And low mechanical strength.

A known method of emulsion copolymerization of PFOPSF and TFE in an aqueous microemulsion of PFOPSF [RF 2545182, C08F 2/24, C08F 214/26, C08F214 / 18, 02/19/2015], carried out by the method of pre-emulsified emulsion copolymerization of PFOPF, in aqueous microFEMP perfluorinated surfactant stabilized using a redox system and pH regulators when applying builder - perfluorinated hydrocarbon C ₆ -C ₁₀ for controlling the composition (the equivalent weight) the image yuschegosya copolymer. The copolymer conversion is up to 80%, EM is up to 800, the water content in the membrane is 40-60%, beats. electrical conductivity - 0.14 S / cm, data on mechanical properties are not in the description.

The disadvantages of this method are:

1. The use of a modifying additive — perfluorinated C ₆ -C ₁₀ hydrocarbon to control the EM or composition of the resulting copolymer, which requires an additional processing step to purify the resulting copolymer from the modifier.

2. The supply of TFE is carried out in the gas phase of the reaction system, which allows the process to be carried out at an elevated pressure of TFE in the range 1.1-1.3 MPa to obtain a copolymer of the required composition or EM.

3. The process of copolymerization of TFE with PFOPSF is carried out at temperatures of 40-50 ° C, which requires the use of a low-temperature redox system to initiate copolymerization.

An analysis of known analogues indicates that the problem of developing an effective technology for the preparation of copolymers of perfluoro-3-oxapentensulfonyl fluoride and tetrafluoroethylene as precursors of proton-conducting membranes remains relevant.

Disclosure of invention

The objective of the invention is to create effective from the point of view of optimizing process parameters technology for producing perfluorinated copolymer of perfluoro-3-oxapentensulfonyl fluoride and tetrafluoroethylene by emulsion copolymerization with the ability to control the characteristics of the resulting copolymer (chemical composition, degree of conversion of the monomer - perfluoro-3-oxapentensulfonyl fluoride, equivalent weight, equivalent mass target product.

This problem is solved by the claimed invention - a method for producing a copolymer of tetrafluoroethylene and perfluoro-3-oxapentensulfonyl fluoride as a precursor of perfluorinated proton conducting membranes by emulsion copolymerization.

The inventive method is characterized by the following set of essential features:

1. A method of obtaining a copolymer of perfluoro-3-oxapentenesulfonyl fluoride and tetrafluoroethylene as a precursor of perfluorinated proton conducting membranes by emulsion copolymerization, which consists in preliminarily preparing an aqueous microemulsion of the first comonomer - perfluoro-3-oxapentensulfonyl fluoride with an average particle size of 1000 nm atm inert gas at a temperature of 20 ° C with a volumetric phase ratio comonomer: water 1: 6-1: 12 (concentration of perfluoro-3-oxapente monomer nsulfonyl fluoride 22.2-12.8 wt.%, 13.5-7.8 vol.%) in the presence of an emulsifier - perfluorinated surfactant in an amount of 2-3 wt. % with respect to the comonomer of perfluoro-3-oxapentensulfonyl fluoride, a component of a water-soluble redox system - persulfa potassium or ammonium in an amount of 0.85-1.2 wt. % with respect to perfluoro-3-oxapentenesulfonyl fluoride and a pH regulator to pH 7-8, then the microemulsion is loaded into the reactor in an inert gas atmosphere, the reactor is blown with the second comonomer - tetrafluoroethylene to a pressure of 0.1 MPa, the microemulsion is stirred at 100 rpm min and heat it to a working temperature of 40-50 ° C, add another component of the water-soluble redox system - sodium metabisulfite in an amount of 0.26-0.3 wt. % with respect to perfluoro-3-oxapentenesulfonyl fluoride, while a redox system of two components is formed in the microemulsion, the mixing speed is set at 450 rpm and copolymerization is carried out by feeding tetrafluoroethylene directly into the microemulsion by bubbling at a working pressure of tetrafluoroethylene of 0.9-1.1 MPa with constant stirring of the reaction medium for 4.5-6.5 hours with the formation of latex, the copolymerization process is completed with the conversion of perfluoro-3-oxapentensulfonyl fluoride 90-92%, latex subjected to coagulation by freezing, followed by separation of the target copolymer from the liquid phase by filtration, the copolymer is washed from the starting materials with deionized water at 80-90 ° C and dried under vacuum.

2. The method according to p. 1, which consists in the fact that for the preparation of an aqueous microemulsion of perfluoro-3-oxapentensulfonyl fluoride, deoxygenated deionized water is used.

3. The method according to p. 1, which consists in the use of a perfluorinated surfactant from the series: ammonium perfluorononate, ammonium perfluorooctanoate, ammonium salt of tetramer of hexafluoroethylene oxide.

4. The method according to p. 1, which consists in the fact that a phosphate buffer of disubstituted and monosubstituted sodium phosphates is used as a pH regulator, reaching a pH of 7-8.

5. The method according to p. 1, which consists in the fact that the ultrasonic dispersion is carried out in an ultrasonic bath with a power of 250 W while mixing the phases, the monomer perfluoro-3-oxapentensulfonyl fluoride - water at 600 rpm and simultaneous ultrasonic exposure for 30 minutes when thermostatic system for maintaining a constant dispersion temperature of 20 ° C.

Thus, the problem is solved by the method of producing a copolymer of tetrafluoroethylene and perfluoro-3-oxapentenesulfonyl fluoride, a precursor of proton conducting membranes, by the method of emulsion copolymerization in an aqueous microemulsion stabilized with a perfluorinated surfactant using a water-soluble initiator, including a redox initiating system, and a redox initiating system and in which to control the composition of the obtained copolymers, the supply of tetrafluoroethylene is carried out by bubbling it into the reaction mass, while the working pressure of tetrafluoroethylene does not exceed 1.1 MPa.

The set of essential features of the claimed device provides a technical result - obtaining a copolymer while maintaining a constant composition of the resulting copolymer (EM) regardless of the conversion of PFOPSF with an increased yield of the target product using effective technology (simpler - no modifying additives are used, less energy-intensive - lower working pressure TFE , environmentally friendly and with a high yield of the target product).

The inventive method is characterized in that the TFE supply is carried out by bubbling into the microemulsion at a pressure of 0.9-1.1 MPa. Sparging leads to the penetration and contact of the monomer with the reagents directly in the volume of the reaction mass and to its additional mixing.

The analysis of the prior art did not allow to find a solution that completely coincides in the totality of essential features with the claimed, which may indicate its novelty.

Only the set of essential features of the claimed device allows to achieve the specified technical result. It turned out to be completely unexpected that the use of a technique known in chemistry - sparging a gaseous reagent into the reaction mass - will lead to such a significant positive result: an increase in the conversion of PFOPSF monomer by 20% (above 90%), the possibility of controlling the EM copolymer within 800-900 without using special modifying additives, improving the properties of membranes - maintaining a high level of electrical conductivity of the membranes in the range of 0.133-0.165 S / cm, increasing the values of mechanical characteristics. At the same time, it was possible to reduce the maximum working pressure of TFE to 1.1 MPa to obtain membranes with an optimal complex of electrochemical and mechanical properties. It was impossible to predict such an effect in advance. It is possible that in this case, bubbling, in addition to the traditional effect of increasing the contact surface of the monomers in the reaction volume, produces another additional positive effect with respect to this complex polymerization system, for example, in the formation of latex. This effect is also not obvious. This allows us to confirm the compliance of the proposed method with the eligibility condition "inventive step" ("non-obviousness").

To confirm the compliance of the claimed invention to the requirement of "industrial applicability" we give examples of specific implementations.

The properties of the obtained copolymers are determined as follows:

1. The equivalent mass of the copolymer (EM) is determined by IR Fourier spectroscopy on samples of extruded films with a thickness of 0.20 ± 0.05 mm in sulfonyl fluoride form. The integrated intensities A of the absorption bands of 2705 cm ⁻¹ (combined vibration frequency of the —SO ₂ F group) and 2365 cm ⁻¹ (overtone of vibration of the —CF ₂ group) are measured.

EM is calculated by the formula:

EM = k [A ²³⁶⁵ / A ²⁷⁰⁵ ]

where: coefficient k = 18.27 was determined from reference samples with a known exchange capacity determined by titration.

2. The melt flow rate (MFR) is determined according to GOST 11645-73 on an IIRT-M plastometer at 270 ± 0.5 ° C, a load of 2.16 kg, a capillary diameter of 2.095 ± 0.005 mm with a sample holding time in the extrusion chamber for 5 minutes.

3. The conversion of PFEVE is calculated based on the values of EM, the yield of the copolymer (W), the amount of PFEVE loaded into the reaction mixture (W ₁ ), according to the formula:

Conversion of PFEVE (%) = [280⋅W⋅100] / [W ₁ ⋅EM],

where: 280 is the molecular weight of PFEVE.

4. Membrane film material is obtained from dilute solutions (2-3% of the mass) in dimethylformamide copolymer in sulfonic acid form by irrigation by controlled evaporation of the solvent followed by annealing of the formed membranes.

Get a film with a thickness of 30-50 microns with a smooth smooth surface without inclusions, shells and other visible defects with dimensions of 500 × 300 × 0.03-0.05 mm with a thickness of not more than 10%.

5. The equilibrium water content in the membrane (water absorption) is determined as follows. The membrane in -SO ₃ H form is kept in distilled water at 25 ° C for 24 hours. The mass of the wet membrane is determined (W ₂ ), and then it is dried in vacuum at 70 ° C to constant weight (W ₃ ). Determine the moisture content of the membrane (C _w ) by the formula:

C _w (%) = (W ₂ -W ₃ ) ⋅100 / W ₃

6. The electrical conductivity of the membranes (σ _n ) in the state of equilibrium saturation with water at 20 ° C is measured by impedance spectroscopy on an Elins Z-3000X impedance meter using a cell with stainless steel electrodes in a four-electrode circuit in the frequency range 100-100000 Hz. The conductivity calculation is carried out according to the formula:

σ _n = L / (R _cp ⋅h⋅b),

where: L is the distance between the voltage electrodes of the measuring cell, cm; (L = 1.77 cm - passport data of the measuring cell);

h is the average thickness of the membrane, cm;

b is the average width of the membrane, cm;

R _cp is the membrane resistance, Ohm.

7. The mechanical tests of the membranes were carried out using the AG-100X Plus universal mechanical testing facility (Shimadzu Corp., Japan), carried out in the uniaxial tension mode for a specimen with a working length of specimens of 25 mm and a fixed specimen stretching speed of 100 mm / min. The measurements were carried out at a fixed humidity RH (50%), which affects the mechanical properties of sulfonic acid membranes. In the process of testing, the following characteristics of the material were determined: elastic modulus E, plasticity limit σ _p , tensile strength to fracture σ _p and ultimate strain to fracture ε _p .

Example 1

In a glass flask equipped with a stirrer, a solution of 0.87 g (2.54 wt% with respect to perfluoro-3-oxapentenesulfonyl fluoride (PFOPSF)) of ammonium perfluorononate, 1.15 g of disubstituted sodium phosphate, 0.57 g of monosubstituted sodium phosphate is loaded 0.29 g of potassium persulfate (0.85 wt.% With respect to PFOPSF) in 200 g of deoxygenated deionized water, vacuum the flask with reagents for 1 min, and then purge with argon. The procedure is repeated 2 more times. To the resulting solution was added 34.2 g of perfluoro-3-oxapentensulfonyl fluoride (PFOPSF), pH = 7-8. The flask is immersed in an ultrasonic bath (dimensions 150 × 160 × 200 mm, power 250 W) filled with water. The flask is immersed in a bath below the water level. Dispersion is carried out with a working milling fluoroplastic mixer at n = 600 rpm and simultaneous ultrasonic action for 30 min at a constantly maintained temperature of 20 ° C. A microemulsion of PFOPSF monomer stable with an average particle size of 1000 nm is obtained during the process.

After that, in the prepared reactor with a volume of 450 cm ³ , treated with 3% hydrogen peroxide, dried and purged with argon, the prepared microemulsion is loaded and the flask is washed with 2 portions of 10 ml of water, adding it to the reactor. The contents of the reactor are purged with argon. The reactor was purged three times with tetrafluoroethylene (TFE) to a pressure of 0.1 MPa. The reactor was stirred at 100 rpm. and heating the reactor to an operating temperature of 50 ° C, including supplying water to the jacket through a thermostat. Duration of heating 15 minutes After reaching the operating temperature, a solution of 0.09 g of sodium metabisulfite (0.26 wt.% With respect to PFOPSF) in 10 g of water is loaded into the reactor. The volumetric ratio of PFOPSF monomer to water phase = 1:12 (concentration of PFOPSF 12.8 wt.%, 7.8 vol.%). Turn on the reactor stirrer at a working speed of 450 rpm and set the working pressure of TFE 1.1 MPa and conduct the copolymerization process for 269 minutes, maintaining a constant pressure of TFE 1.1 MPa. TFE is fed directly to the PFOPSF emulsion through a capillary tube with an inner diameter of 3 mm. The constant pressure of TFE in the reaction zone is maintained automatically by a pressure reducer. After the copolymerization process is completed, the reactor is cooled down to 20 ° С, while the pressure of TFE is vented. In the copolymerization process, 40 g of TFE was consumed. Unloaded 297.9 g of latex. Latex is transparent opalescent.

The density of the latex is 1.166 g / cm ³ .

The dry residue is 23.5%.

The average particle size of latex is 70 nm.

The latex is coagulated by freezing, the precipitated copolymer is filtered off on a Buchner funnel, washed with 8 portions of water in 100 ml each at a temperature of 80-90 ° C and dried under vacuum without drying. 77.9 g of copolymer are obtained. The conversion of the PFOPSF monomer is 91.1%.

MFI of the copolymer (270 ° C, 2.16 kg, 2.095 mm) - 0.13 g / 10 min.

The equivalent mass of the copolymer determined by FTIR spectroscopy is 700.

The equivalent mass of the copolymer, determined by the ion-exchange capacity of the membrane, is 800.

Characteristics of a sulfonic acid-derived membrane obtained from a copolymer at 20 ° C:

Water Content - 50.5%

Electrical conductivity - 0.145 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The elastic modulus E is 285 MPa.

The plastic limit σ _p - 13.6 MPa.

The tensile strength σ _p - 30 MPa.

Ultimate deformation to fracture ε _p - 352%.

Example 2

It differs from example 1 in that to obtain the initial emulsion PFOPSF use a solution of 1.61 g of ammonium perfluorononate (2.57 wt.% In relation to PFOPSF), 2.14 g of disubstituted sodium phosphate, 1.07 g of monosubstituted sodium phosphate, 0 , 54 g of potassium persulfate (0.86 wt.% In relation to PFOPSF), pH = 7-8, 0.17 g of sodium metabisulphite (0.275 wt.% In relation to PFOPSF) and 62.5 g of PFOPSF in 213 g of oxygen-free deionized water, and the copolymerization process is carried out at a TFE pressure of 1.1 MPa and a temperature of 50 ° C. The volumetric ratio of PFOPSF - water phase = 1: 6 (concentration of PFOPSF 22.2 wt.%, 13.5 vol.%) .. The copolymerization time is 6.5 hours. 88 g of TFE are consumed. Received 374.0 g of latex.

The density of the latex is 1.297 g / cm ³ .

The dry residue is 41.5%.

The average particle size of latex is 80 nm.

The dry weight of the polymer is 145.5 g.

PFOPSF conversion - 91%.

The MFI of the copolymer is 0.18 g / 10 min.

The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 765.

The equivalent mass of the copolymer, determined by the ion-exchange capacity of the membrane, is 880.

Characteristics of the membrane in sulfonic acid form at 20 ° C:

Water Content - 45.9%

Electrical conductivity - 0.137 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The elastic modulus E is 287 MPa.

The plastic limit σ _p - 13.6 MPa.

The tensile strength σ _p - 31 MPa.

The ultimate strain to failure ε _p - 337%.

Example 3

It differs from example 1 in that to obtain the initial emulsion PFOPSF use a solution of 1.45 g of ammonium perfluorononate (3 wt.% In relation to PFOPSF), 1.66 g of disubstituted sodium phosphate, 0.83 g of monosubstituted sodium phosphate, 0.58 g of ammonium persulfate (1.2 wt.% in relation to PFOPSF), pH = 7-8, 0.145 g of sodium metabisulfite (0.3 wt.% in relation to PFOPSF) and 48.5 g of PFOPSF in 220 g of deoxygenated deionized water and the copolymerization process is carried out at a TFE pressure of 1.1 MPa and a temperature of 40 ° C. The volumetric ratio of PFOPSF - water phase = 1: 8 (concentration of PFOPSF 17.8 wt.%, 10.9 vol.%). The copolymerization time is 6.5 hours. 72 g of TFE are consumed. Received 334 g of latex.

The density of the latex is 1.262 g / cm ³ .

The dry residue is 35.5%.

The average particle size of latex is 70 nm.

The mass of dry polymer is 121.2 g.

PFOPSF conversion - 92%.

The MFI of the copolymer is 0.59 g / 10 min.

The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 762.

The equivalent mass of the copolymer, determined by the ion exchange capacity of the membrane, is 877.

Characteristics of the membrane in sulfonic acid form at 20 ° C:

Water Content - 45.6%

Electrical conductivity - 0.133 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The modulus of elasticity E is 286 MPa.

The plastic limit σ _p - 13.6 MPa.

The tensile strength σ _p - 27 MPa.

The ultimate strain to failure ε _p - 314%.

Example 4

It differs from Example 1 in that, to obtain the initial emulsion PFOPSF, a solution of 1.25 g of ammonium perfluorooctanoate (2 wt% with respect to PFOPSF) is used), 2.14 g of disubstituted sodium phosphate, 1.07 g of monosubstituted sodium phosphate, 0, 54 g of potassium persulfate (0.86 wt.% In relation to PFOPSF), pH = 7-8, 0.17 g of sodium metabisulfite (0.27 wt.% In relation to PFOPSF) and 62.5 g of PFOPSF in 213 g deoxygenated deionized water, and the copolymerization process is carried out at a TFE pressure of 0.9 MPa and a temperature of 50 ° C. The volumetric ratio of PFOPSF - water phase = 1: 6 (concentration of PFOPSF 22.2 wt.%, 13.5 vol.%). Instead of ammonium perfluorooctanoate, the ammonium salt of the tetramer of hexafluoroethylene oxide can be used.

The copolymerization time is 6.5 hours. 86.5 g of TFE are consumed. Received 342 g of latex.

The density of the latex is 1.292 g / cm ³ .

The dry residue is 39%.

The average particle size of latex is 90 nm.

The mass of dry polymer is 143 g.

PFOPSF conversion - 90.3%.

The MFI of the copolymer is 0.53 g / 10 min.

The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 710.

The equivalent mass of the copolymer, determined by the ion-exchange capacity of the membrane, is 800.

Characteristics of the membrane in sulfonic acid form at 20 ° C:

Water Content - 50.2%

Electrical conductivity - 0.150 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The modulus of elasticity E is 290 MPa.

The plastic limit σ _p - 12.6 MPa.

The tensile strength σ _p - 28 MPa.

Ultimate deformation to fracture ε _p - 312%.

Membranes from copolymers obtained by the implementation of the claimed invention are not inferior to the mechanical properties of extruded unmodified membranes Aquivion ^® E-87 company Solvay Solexis.

Example 5 (Control Supply TFE in the gas phase).

The process was carried out as in example 1, feeding TFE through a fitting in the lid of the reactor into the gas phase. The copolymerization process was carried out at a TFE pressure of 1.1 MPa and a temperature of 50 ° C. The volumetric ratio of PFOPSF monomer to water phase = 1:12 (concentration of PFOPSF 12.8 wt.%, 7.8 vol.%). The copolymerization time was 4.5 hours. 22.4 g of TFE were consumed. Received 275.6 g of latex. Coagulum (wet in the form of a gel from a mixer) was isolated - 11 g.

The density of the latex is 1.1447 g / cm ³ .

The dry residue is 21.7%.

The average particle size of latex is 90 nm.

The mass of dry polymer is 51 g.

PFOPSF conversion - 66.1%.

The MFI of the copolymer is 0.8 g / 10 min.

The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 642.

The equivalent mass of the copolymer, determined by the ion-exchange capacity of the membrane, is 752.

Characteristics of the membrane in sulfonic acid form at 20 ° C:

Water Content - 72.3%

Electrical conductivity - 0.158 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The modulus of elasticity E is 220 MPa.

The plastic limit σ _p - 10.1 MPa.

The tensile strength σ _p - 20 MPa.

Ultimate deformation to fracture ε _p - 405%.

Example 6 (Control Supply TFE in the gas phase).

The process was carried out as in example 4, feeding TFE through a fitting in the lid of the reactor into the gas phase. The copolymerization process was carried out at a TFE pressure of 1.3 MPa and a temperature of 50 ° C. The volumetric ratio of PFOPSF monomer to water phase = 1:12 (concentration of PFOPSF 12.8 wt.%, 7.8 vol.%). The copolymerization time was 4.5 hours. 30.4 g of TFE were consumed. Received 299.4 g of latex.

The density of the latex is 1.1447 g / cm ³ .

The dry residue is 21.7%.

The average particle size of latex is 90 nm.

The mass of dry polymer is 62.5 g.

PFOPSF conversion - 71%.

The MFI of the copolymer is 0.1 g / 10 min.

The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 721.

The equivalent mass of the copolymer, determined by the ion-exchange capacity of the membrane, is 807.

Characteristics of the membrane in sulfonic acid form at 20 ° C:

The water content is 50.8%.

Electrical conductivity - 0.146 S / cm (at 20 ° С and humidity (RH) 100%):

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

Elastic modulus E - 280 MPa.

The plastic limit σ _p - 13.1 MPa.

The tensile strength σ _p - 29 MPa.

Ultimate deformation to fracture ε _p - 355%.

In this example, the working pressure of TFE (1.3 MPa) is higher than in the claimed invention, but the result of the invention is not achieved when sparging is used.

Example 7 (Control according to the patent of the Russian Federation 2545182).

In a glass flask equipped with a stirrer, a solution of 0.8653 g (2.55 wt.% With respect to PFOPSF) of ammonium perfluorononate, 1.15 g of disubstituted sodium phosphate, 0.57 g of monosubstituted sodium phosphate, 0.0865 g (0 , 26 wt.% With respect to PFOPSF) sodium metabisulfite in 200 g of deoxygenated deionized water, add 33.9 g PFOPSF, 1.7 g of perfluorinated hydrocarbon C ₆ -C ₁₀ (5 wt.% With respect to PFOPSF monomer) vacuum flask with reagents for 1 min, and then purged with argon. The procedure is repeated 2 more times. The flask is immersed in an ultrasonic bath (dimensions 150 × 160 × 200 mm, power 250 W) filled with water. The flask is immersed in a bath below the water level. Dispersion is carried out at n = 600 rpm for 30 minutes A microemulsion of the PFOPSF monomer (FS-81) with a perfluorinated C ₆ -C ₁₀ hydrocarbon is stable during the process.

After that, in the prepared reactor with a volume of 450 cm ³ , treated with 3% hydrogen peroxide, dried and purged with argon, the prepared microemulsion is loaded and the flask is washed with 2 portions of 10 ml of water, adding it to the reactor. The contents of the reactor are purged with argon. The reactor was purged three times with tetrafluoroethylene (TFE) to a pressure of 0.1 MPa. The reactor was stirred at 100 rpm. and heating the reactor to an operating temperature of 50 ° C., including electrical heating. Duration of heating 15 minutes After reaching the operating temperature, a solution of 0.285 g (0.84 wt.% With respect to PFOPSF) potassium persulfate in 10 g of water is loaded into the reactor. The volume ratio of the monomer FS-81 + perfluorinated hydrocarbon With ₆ -C _{10 the} aqueous phase = 1: 11.5. Turn on the reactor stirrer at a working speed of 450 rpm and set the working pressure of TFE to 1.3 MPa and carry out the copolymerization process for 4.5 minutes, maintaining a constant pressure of TFE of 1.3 MPa.

After the copolymerization process is completed, the reactor is cooled down to 20 ° С, while the pressure of TFE is vented. In the copolymerization process, 32 g of TFE was consumed. Unloaded 300.5 g of latex.

The latex is coagulated by freezing, the precipitated copolymer is filtered off on a Buchner funnel, washed with 8 portions of 100 ml water at a temperature of 80 ° C until there are no traces of a surfactant. To remove residues of perfluorinated C ₆ -C ₁₀ hydrocarbon, the copolymer is additionally washed with 100 ml of chloroform.

Obtain 71 g of a copolymer. The conversion of the PFOPSF monomer is 77.7%. The performance of the process is 33.7 g of copolymer / l⋅h. The equivalent mass of the copolymer, determined by FTIR spectroscopy, is 755.

The MFI of the copolymer is 1.5 g / 10 min.

Characteristics of a sulfonic acid-derived membrane obtained from a copolymer at 20 ° C:

The water content is 46.3%,

The conductivity is 0.140 S / cm.

Membranes, in contrast to the claimed invention, are obtained by pressing followed by hydrolysis and acid treatment.

The mechanical properties of the membrane, determined at 20 ° C and RH = 50%:

The modulus of elasticity E is 205 MPa.

The plastic limit σ _p - 12.3 MPa.

The tensile strength σ _p - 27 MPa.

The ultimate strain to failure ε _p - 352%.

The implementation of the claimed invention is not limited to the above examples.

The results given in the examples show that the proposed technology for the copolymerization of TFE with PFOPSF with the supply of tetrafluoroethylene by bubbling it into the reaction mass (examples 1-4), provides a copolymer with optimal properties (EM according to IOE in the range of 800-900, melt flow rate 0 1-0.6 g / 10 min). It is possible to reduce the working pressure of TFE to 0.1 MPa in comparison with the method of introducing TFE into the gas phase, while membrane copolymers with optimal electrochemical and mechanical properties are obtained. For comparison: the analog has a pressure of 1.3 MPa and a modifying additive was used, while, for example, in the conversion of PFOPSF, the result is worse by 20%, the consistency of the composition of the copolymer is not ensured. The proposed technology allows the copolymerization process to deep degrees of PFOPSF conversion (more than 90%) to maintain a constant composition or EM of the resulting copolymer regardless of the degree of PFOPSF conversion. The mechanical properties of sulfonic acid membranes obtained by irrigation from a solution of the synthesized copolymer in sulfo-alkaline form in dimethylformamide are not inferior to the mechanical properties of extruded unmodified Aquivion ^® E-87 membranes from Solvay Solexis.

Claims (5)

1. A method of obtaining a copolymer of perfluoro-3-oxapentenesulfonyl fluoride and tetrafluoroethylene as a precursor of perfluorinated proton conducting membranes by emulsion copolymerization, which consists in preliminarily preparing an aqueous microemulsion of the first comonomer — perfluoro-3-oxapentensulfonyl fluoride with an average particle size of 1000 nm atomager inert gas at a temperature of 20 ° C with a volumetric phase ratio comonomer: water 1: 6-1: 12 (concentration of monomer perfluoro-3-oxapentene sulfonyl fluoride 22.2-12.8 wt.%, 13.5-7.8 vol.%) in the presence of an emulsifier - perfluorinated surfactant in an amount of 2-3 wt. % with respect to the comonomer of perfluoro-3-oxapentensulfonyl fluoride, a component of a water-soluble redox system - potassium or ammonium persulfate in an amount of 0.85-1.2 wt. % with respect to perfluoro-3-oxapentensulfonyl fluoride and a pH regulator to pH 7-8, then the microemulsion is loaded into the reactor in an inert gas atmosphere, the reactor is blown with the second comonomer - tetrafluoroethylene to a pressure of 0.1 MPa, the microemulsion is stirred at 100 rpm min and heat it to a working temperature of 40-50 ° C, add another component of the water-soluble redox system - sodium metabisulfite in an amount of 0.26-0.30 wt. % with respect to perfluoro-3-oxapentenesulfonyl fluoride, while a redox system of two components is formed in the microemulsion, the mixing speed is set at 450 rpm and copolymerization is carried out by feeding tetrafluoroethylene directly into the microemulsion by bubbling at a working pressure of tetrafluoroethylene of 0.9-1.1 MPa with constant stirring of the reaction medium for 4.5-6.5 hours with the formation of latex, the copolymerization process is completed with the conversion of perfluoro-3-oxapentensulfonyl fluoride 90-92%, latex subjected to coagulation by freezing, followed by separation of the target copolymer from the liquid phase by filtration, the copolymer is washed from the starting materials with deionized water at 80-90 ° C and dried under vacuum. 2. The method according to p. 1, which consists in the fact that for the preparation of an aqueous microemulsion of perfluoro-3-oxapentensulfonyl fluoride, deoxygenated deionized water is used. 3. The method according to p. 1, which consists in the use of a perfluorinated surfactant from the series: ammonium perfluorononate, ammonium perfluorooctanoate, ammonium salt of tetramer of hexafluoroethylene oxide. 4. The method according to p. 1, which consists in the fact that a phosphate buffer of disubstituted and monosubstituted sodium phosphates is used as a pH regulator, reaching a pH of 7-8. 5. The method according to p. 1, which consists in the fact that the ultrasonic dispersion is carried out in an ultrasonic bath with a power of 250 W while mixing the phases, the monomer perfluoro-3-oxapentensulfonyl fluoride - water at 600 rpm and simultaneous ultrasonic exposure for 30 minutes when thermostatic system for maintaining a constant dispersion temperature of 20 ° C.