RU2643960C1 - Proton conducting polymer membranes and the method of their obtaining - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: proton-conductive polymeric membranes with high conductivity based on modified polyvinyl chloride contain sulfonic acid fragments, vinyl chloride units and dehydrochlorinated units of vinyl chloride modified by sulfonation of polyvinyl chloride with chlorosulfonic acid in 1,2-dichloroethane medium in the presence of a thermal stabilizer (barium salts) at a temperature of 60°C and vigorous stirring for 1 hour. The process of preparation of proton-conductive polymer membranes involves sulfonation of polyvinyl chloride with chlorosulfonic acid in the presence of a heat stabilizer, followed by rolling a mixture based on modified polyvinyl chloride containing sulfonic acid fragments, vinyl chloride units and dehydrochlorinated units of vinyl chloride and dioctyl phthalate at a temperature of 100-120°C for 20 minutes. The method of producing proton-conductive polymer membranes involves rolling a mixture based on a sulfonated polymer and dioctyl phthalate in a ratio of 1:0.4 for 20 minutes.

EFFECT: invention makes it possible to develop a method for obtaining new effective thermally stable proton-conducting membranes in a simple and convenient manner.

4 cl, 7 ex

Description

The invention relates to hydrogen energy and fuel cells, in particular to methods for producing proton-conducting polymer membranes used in solid polymer fuel cells.

Perfluorinated electrolyte membranes of the type "Nafion", "Flemion" are known. Neosepta and their domestic counterpart (MF-4SK) based on copolymers of tetrafluoroethylene with perfluorinated vinyl esters [S.Walkins.In Full Cell Systems (Eds L.G. Blumen, M.N. Muqerwa). Phenum, New York. 1993. P. 493. W.G. Grot. Macromol. Symp. 1994. V. 82. P. 161. US patent 3718627 1973; US patent 4433082, 1984; RF patent 2412208, 2011].

Signs of membranes such as "Nafion", "Flemion", "Neosepta" and "MF-4SK), coinciding with the essential features of the claimed invention, are a linear polymer matrix containing sulfonic acid groups, and thermal stability in alkaline and in acidic environments.

The disadvantages of analogues of these types are the high cost of membranes due to the complexity and complexity of obtaining polyperfluorinated electrolyte: the initial monomer [perfluoro (3,6-dioxa-4-methyl-oct-7-ene) sulfonyl fluoride] is obtained as a result of five-stage synthesis and the reaction products do not yield at all stages of the process quantitative. The multistage process for producing a polyperfluorinated polymer matrix and the high cost of the compounds used leads to the high cost of membranes and significantly limits the possibility of their use in fuel cells and practically negates the possibility of their use in electromembrane separation and purification processes, where blocks of a large number of membranes with a large area are required.

Proton-conducting polymer membranes based on trifluorostyrene and substituted vinyl compounds are known (US Patent 6765027, July 20, 2004).

Signs of an analog membrane that coincide with the essential features of the claimed invention is a linear macromolecule containing sulfo groups in its structure.

The disadvantages of the analogue are low proton conductivity at low humidity and temperatures below 100 ° C, a tendency to destruction, as well as low physical and mechanical properties.

A known method for producing proton-conducting polymer membranes [RF Patent 2279906, B01D 71/62 (2006M), H01M 8/02 (2006.01), published on July 20, 2006].

The signs of the analogue method, which coincides with the essential features of the proposed method, is a polymer matrix containing phosphate groups.

The disadvantage of the analogue method is the need for doping the polymer matrix with phosphoric acid. The resulting complex is unstable in time and, as a result, the membrane ceases to have proton conductivity.

A known method of producing proton-conducting polymer membranes (RF Patent 2285557, B01D 71/38 (2006.01), B01D 71/52 (2006.01), published on 10/20/2006).

The features of the analogue method, which coincide with the essential features of the proposed method, are a linear polymer matrix containing sulfonic acid groups.

The disadvantages of the analogue method are the multi-stage production of a polymer electrolyte and the possibility of interaction of the resulting sulfonic acid fragments with the hydroxyl groups of polyvinyl alcohol, which is part of the polymer base, with the formation of various structures:

Such an interaction leads to a decrease in sulfonic acid groups in the polymer and, accordingly, to a decrease in the proton conductivity of the membrane.

Closest to the described polymer ionic membranes are membranes based on a copolymer of vinyl chloride and vinyl butyl ether containing sulfonic acid groups [Trofimov B.A., Ermakova T.G., Volkova L.I., Kuznetsova N.P., Myachina G.F. , Chipanina N.N., Kanitskaya L.V., Vakulskaya T.I., Rokhin A.V., Mognonov D.M. Plastics. 2007. No1. S. 20-23].

Signs of an analog membrane that coincide with the essential features of the claimed invention is a polymer matrix containing sulfonic acid fragments, vinyl chloride units and polyvinylylene blocks:

The disadvantages of the analogue are low proton conductivity values (1-3) ⋅ 10 ^-4 S / cm at room temperature.

Closest to the described invention in technical essence are proton-conducting polymer membranes based on modified polyvinyl chloride containing sulfonic acid groups [Shaglaeva NS, Sultangareev RG, Orkhokova EA, Prozorova GF, Dmitrieva GV , Dambinova A.S., Stenina I.A., Yaroslavtsev A.B. Membranes and membrane technologies. 2011. No3. from. 213-219].

The above membranes and the method for their preparation are closest to the claimed membranes and method according to the technical essence and are selected as a prototype.

The features of the prototype method, which coincides with the essential features of the claimed invention, are a linear polymer matrix containing sulfonic acid fragments, vinyl chloride units and dehydrochlorinated vinyl chloride units:

The disadvantages of the prototype method are the low values of the proton conductivity of the membranes from 2.0 × 10 ^-4 S / cm to 5.9 × 10 ^-3 S / cm in the temperature range 45-100 ° C and poor physical and mechanical properties. The low proton conductivity of the membranes is explained by the low degree of substitution of chlorine atoms in the initial polyvinyl chloride for a sulfo group due to the dehydrochlorination process with the formation of a carbon-carbon double bond in the polymer chain, the chlorine atom in the α-position to it becomes more mobile, which is expressed in lowering the activation energy of the further dehydrochlorination process and, as a result, the resulting hydrogen chloride accelerates the dehydrochlorination reaction and suppresses the substitution reaction [Shaglaeva NS, Sultan Gareev R.G., Orkhokova E.A., Prozorova G.F., Dmitrieva G.V., Dambinova A.S., Stenina I.A., Yaroslavtsev A.B. Membranes and membrane technologies. 2011. No3. from. 213-219].

The group of inventions is aimed at creating proton-conducting polymer membranes with high proton conductivity in a simple and effective way.

The technical result of the inventions is to create proton-conducting polymer membranes and methods for their preparation, devoid of the above disadvantages, namely, to increase proton conductivity at temperatures up to 150 ° C, increase mechanical and chemical strength and thermal stability. The advantage of proton-conducting polymer membranes is a significant reduction in their cost as a result of a simple and effective method for their preparation.

The technical result of the inventions is achieved by the development of proton-conducting polymer membranes based on modified polyvinyl chloride by increasing the content of sulfonic acid groups using thermal stabilizers ("traps" of hydrogen chloride) in the original polymer, which leads to an increase in its proton conductivity.

In contrast to the prototype - (Shaglaeva N.S., Sultangareev R.G., Orkhokova E.A., Prozorova G.F., Dmitrieva G.V., Dambinova A.S., Stenina I.A., Yaroslavtsev A .B. Membranes and membrane technologies. 2011. No. 3. S. 213-219) the maximum degree of substitution of which is 11.6%, in the inventive polymer membranes, the degree of substitution is 32.9% and the claimed polymer membranes are much more heat-resistant. According to differential thermal analysis, the membranes are thermostable up to 200 ° C, at 220 ° C the weight loss is only 3%, at 260 ° C - 10%, and a 30% loss is recorded only at 320 ° C. The mechanical properties of the claimed polymer membranes in both alkaline and acidic environments are satisfactorily preserved.

The proposed proton-conducting polymer membranes and the method for their preparation have significant advantages:

the obtained proton-conducting polymer membranes have high proton conductivity at temperatures up to 150 ° C at low humidity;

- the developed proton-conducting polymer membranes are characterized by mechanical strength, chemical strength and thermal stability;

- ease of obtaining membranes;

- low cost of membranes.

A method of obtaining proton-conducting polymer membranes is as follows.

The method of obtaining new proton-conducting polymer membranes is based on the reaction of nucleophilic substitution of chlorine atoms in a finished industrial polyvinyl chloride to sulfo groups:

The process is carried out in a solvent medium with vigorous stirring and a temperature of 60-80 ° C. Blocking the process of dehydrochlorination of vinyl chloride units is carried out using the "traps" of hydrogen chloride. For all experiments, the yield of modified PVC is quantitative and ranges from 82% to 90%.

The IR spectra of the inventive proton-conducting polymer membranes retain absorption bands at 2920 cm ^-1 1430 cm ^-1 , related to -CH ₂ groups of polyvinyl chloride and stretching vibrations of the C-C1 bond at 600, 680 cm ^-1 , but absorption bands appear at 1200 cm ^-1 and 1150 cm ^-1 , characteristic for vibrations of sulfo groups.

The method of obtaining new proton-conducting polymer membranes is illustrated by the following examples.

Example 1. 5 g (0.08 base mol) of PVC and 0.25 g of thermostabilizer were dissolved at room temperature in 50 ml of 1,2-dichloroethane and 32.92 ml (0.50 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 50 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The degree of substitution of chlorine atoms in PVC (a) was calculated according to the elemental analysis according to the sulfur content:

where α is the degree of substitution of chlorine atoms in PVC;

X is the sulfur content in the sample, wt. %;

108 - molecular weight of the link of the General formula:

The preparation of sulfonated PVC membranes was carried out by rolling a mixture based on sulfonated polymer and dioctyl phthalate in a ratio of 1: 0.4 at a temperature of 100-120 ° C for 20 minutes. The membrane obtained by rolling the mixture at temperatures below 100 ° C is characterized by heterogeneity of the structure over the entire thickness, and at temperatures above 120 ° C, thermal and thermal oxidative degradation are possible. An increase in rolling time and a decrease in the amount of dioctyl phthalate in the mixture leads to a deterioration in the quality of the membrane. With an increase in the content of dioctyl phthalate in the mixture of more than 0.4, it is not possible to obtain a uniform membrane.

Conductometric measurements of the obtained membranes were carried out in contact with deionized water using an AC bridge "2 V-1" in the frequency range 10-600000 Hz at 100 ° C. The value of ionic conductivity at this temperature was found by extrapolating the impedance hodographs to the axis of active resistances. The degree of substitution and the value of proton conductivity were 6.6% and (3-8) ⋅ 10 ^-4 S / cm at 150 ° C, respectively.

Example 2. 5 g (0.08 base mol) of PVC and 0.10 g of stabilizer were dissolved at room temperature in 50 ml of 1,2-dichloroethane and 26.33 ml (0.40 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 60 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The determination of the degree of substitution of chlorine atoms in PVC, the formation of the membrane and the determination of proton conductivity was carried out analogously to example 1.

The degree of substitution and the value of proton conductivity were 13.6% and (3-8) ⋅ 10 ^-3 S / cm at 150 ° C, respectively.

Example 3. 5 g (0.08 basic mol) of PVC and 0.25 g of thermal stabilizer were dissolved at room temperature in 50 ml of 1,2-dichloroethane and 26.33 ml (0.45 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 60 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The determination of the degree of substitution of chlorine atoms in PVC, the formation of the membrane, and the determination of proton conductivity were carried out analogously to example 1. The degree of substitution and the value of proton conductivity were 24.9% and 1⋅10 ^-2 S / cm at 150 ° С, respectively.

Example 4. 5 g (0.08 basic mol) of PVC and 0.25 g of thermal stabilizer were dissolved at room temperature in 50 ml of 1,2-dichloroethane, and 32.92 ml (0.50 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 60 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The determination of the degree of substitution of chlorine atoms in PVC, the formation of the membrane, and the determination of proton conductivity were carried out analogously to example 1. The degree of substitution and the value of proton conductivity were 32.9% and 2.9 × 10 ^-1 S / cm at 150 ° C, respectively.

Example 5. 5 g (0.08 base mol) of PVC and 0.25 g of thermostabilizer were dissolved at room temperature in 50 ml of 1,2-dichloroethane and 39.50 ml (0.60 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 60 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The determination of the degree of substitution of chlorine atoms in PVC, the formation of the membrane and the determination of proton conductivity was carried out analogously to example 1. The degree of substitution and the value of proton conductivity was 29.1% and (5-9) ⋅ 10 ^-3 S / cm at 150 ° C, respectively.

Example 6. 5 g (0.08 basic mol) of PVC and 0.25 g of thermal stabilizer were dissolved in 50 ml of 1,2-dichloroethane at room temperature, and 32.92 ml (0.50 mol) of chlorosulfonic acid were added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 80 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The determination of the degree of substitution of chlorine atoms in PVC, the formation of the membrane and the determination of proton conductivity was carried out analogously to example 1. The degree of substitution and the value of proton conductivity was 5.9% and (6-8) ⋅ 10 ^-4 S / cm at 150 ° C, respectively.

Example 7. 5 g (0.08 basic mol) of PVC and 0.25 g of thermal stabilizer were dissolved in 50 ml of 1,2-dichloroethane at room temperature and 32.92 ml (0.50 mol) of chlorosulfonic acid was added dropwise with stirring. The reaction mixture was kept under vigorous stirring for 1 hour at 90 ° C. After cooling, the reaction mass was poured into cold water, the precipitated modified PVC was washed with water and dried in vacuum to constant weight. The degree of substitution of chlorine atoms in PVC, the formation of the membrane and the determination of proton conductivity were determined analogously to example 1. The degree of substitution and the value of proton conductivity was 3.8% and (2-3) ⋅ 10 ^-4 S / cm at 150 ° C, respectively.

For all experiments, the yield of sulfonated polyvinyl chloride is quantitative and ranges from 70 to 90%.

For the studied membranes, an increase in proton conductivity is observed with an increase in the content of sulfonic acid groups in the polymer chain. The maximum number of sulfonic acid fragments in the polymer is achieved with a polymer: chlorosulfonic acid ratio of 0.08: 0.50 (Example 4).

An increase in the temperature of sulfonation of polyvinyl chloride leads to a decrease in the number of sulfonic acid groups in the macromolecule due to the acceleration of the dehydrochlorination reaction of vinyl chloride units. According to differential thermal analysis, the membranes are thermostable up to 200 ° C, at 220 ° C the weight loss is only 3%, at 220 ° C - 10%, and a 30% loss is recorded only at 320 ° C. The mechanical properties of the studied membranes up to 200 ° C are satisfactorily preserved.

Claims (4)

1. Proton-conducting polymer membranes with high conductivity based on modified polyvinyl chloride containing sulfonic acid fragments, vinyl chloride units and dehydrochlorinated vinyl chloride units, modified by sulfonation of polyvinyl chloride with chlorosulfonic acid in 1,2-dichloroethane medium in the presence of a heat stabilizer at a temperature of 60 ° C for 1 hour and vigorous stirring. 2. Proton-conducting polymer membranes according to claim 1, characterized in that barium salts are used as thermostabilizer. 3. A method of producing proton-conducting polymer membranes according to claim 1, comprising sulfonating polyvinyl chloride with chlorosulfonic acid in the presence of a thermal stabilizer, followed by rolling a mixture based on modified polyvinyl chloride containing sulfonic acid fragments, vinyl chloride units and dehydrochlorinated vinyl chloride units and dioctyl phthalate 100 ° C at a temperature of 100 ° C for 20 ° C at a temperature of 100 ° C. 20 minutes. 4. A method of producing proton-conducting polymer membranes according to claim 1, comprising rolling the mixture based on sulfonated polymer and dioctyl phthalate in a ratio of 1: 0.4 for 20 minutes