Cross-linked high stable anion exchange blend membranes with polyethyleneglycols as hydrophilic membrane phase

Abstract

The invention relates to: —anion exchange blend membranes consisting the following blend components: —a halomethylated polymer (a polymer with —(CH.sub.2).sub.x—CH.sub.2—Hal groups, Hal=F, Cl, Br, I; x=0-12), which is quaternised with a tertiary or a n-alkylated/n-arylated imidazole, an N-alkylated/N-arylated benzimidazole or an N-alkylated/N-arylated pyrazol to form an anion exchanger polymer. —an inert matrix polymer in which the anion exchange polymer is embedded and which is optionally covalently crosslinked with the halomethylated precursor of the anion exchanger polymer, —a polyethyleneglycol with epoxide or halomethyl terminal groups which are anchored by reacting with N—H-groups of the base matrix polymer using covalent cross-linking—optionally an acidic polymer which forms with the anion-exchanger polymer an ionic cross-linking (negative bound ions of the acidic polymer forming ionic cross-linking positions relative to the positive cations of the anion-exchanger polymer)—optionally a sulphonated polymer (polymer with sulphate groups —SO.sub.2Me, Me=any cation), which forms with the halomethyl groups of the halomethylated polymer covalent crosslinking bridges with sulfinate S-alkylation. The invention also relates to a method for producing said membranes, to the use of said membranes in electrochemical energy conversion processes (e.g. Redox-flow batteries and other flow batteries, PEM-electrolyses, membrane fuel cells), and in other membrane methods (e.g. electrodialysis, diffusion dialysis).

Claims

1. An anion exchange blend membrane, comprising: a halomethylated polymer including functional groups (CH.sub.2).sub.x—CH.sub.2Hal, Hal being fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) and x being an integer between 0 and 12, inclusive, and one or more cationic function groups derived from a tertiary amine, an alkylated imidazole, an alkylated pyrazole, or an alkylated benzimidazole in a quaternization reaction; a basic or neutral non-fluorinated or partially fluorinated inert matrix polymer; and a polyethylene glycol with epoxy or halomethylene ends groups on one or both chain ends.

2. The anion exchange blend membrane of claim 1, further comprising a polymer with acidic functional groups S0.sub.3M, P0.sub.3M.sub.2 or COOM, M being a cation.

3. The anion exchange blend membrane of claim 1, further comprising a polymer containing sulfinate groups S0.sub.2M, M being a cation.

Description

FIGURE DESCRIPTION

(1) FIG. 1 shows the chloride conductivities of the membranes 2175 and 2176 in the temperature range between 30 and 90° C. with a constant relative humidity of 90%.

(2) FIG. 2 shows the chloride conductivity of the membrane 2176 before and after 10, 20 and 30 days incorporation in 1M KOH in a temperature range of 30 to 90° C. and a relative humidity of 90%.

(3) FIG. 3 shows the TGA curves of membranes 2175 and 2176 before and after 10 days treatment in 1 M KOH at 90° C.

(4) FIG. 4 shows the TGA curves of membrane 2176 before and after 10, 20 and 30 days treatment in 1 M KOH at 90° C.

(5) FIG. 5 shows the chloride conductivity of the membrane 2190A before and after 10 days storage in 1 M KOH in the temperature range 30-90° C. at a relative humidity of 90%.

(6) FIG. 6 shows the TGA curves of membrane 2190A before and after 10 days storage in 1M KOH at 90° C.

(7) FIG. 7 shows the chloride conductivity of the membrane 2215 before and after 10 days storage in 1 M KOH in the temperature range 30-90° C. at a relative humidity of 90%.

(8) FIG. 8 shows the TGA curves of membrane 2215 before and after 10 days storage in 1M KOH at 90° C.

(9) FIG. 9 shows the chloride conductivity of the membrane 2179B before and after 10 days storage in 1 M KOH in the temperature range 30-90° C. at a relative humidity of 90%.

(10) FIG. 10 shows the chloride conductivity of the membrane 2216 before and after 10 days storage in 1 M KOH in the temperature range 30-90° C. at a relative humidity of 90%.

(11) FIG. 11 shows the chloride conductivity of the commercial anion exchange membrane Tokuyama A201 in the temperature range 30-80° C. at a relative humidity of 90%.

APPLICATION EXAMPLES

Example 1: AEM Blends of PVBCI, PBIOO, a Sulfonated Polyethersulfone (SAC098, See Description) Tetramethylimidazole for Quaternization of PVBCI and an Epoxide-Terminated Polyethylene Glycol (Membranes MJK2175 and MJK2176)

(12) Membrane Production and Aftertreatment:

(13) 12 g of a 10% by weight solution of polyvinylbenzyl chloride (ALDRICH product no. 182532, structure see FIG. 2) in N,N-dimethylacetamide (DMAc) are mixed with 6 g of a 33.3% by weight solution of 1,2,4,5-tetramethyl-1H-imidazole (TCI Product No. T0971, see FIG. 1 for structure), 6.7 g of a 10% by weight solution of PBIOO (manufacturer FumaTech, structure see FIG. 3) and 2.67 g of a 10% by weight solution of a sulfonated polyethersulfone (SAC098, IEC=1.8 meq SO.sub.3H/g, see description) mixed in DMAc. In the case of membrane 2175, 0.25 g of epoxide-terminated polyethylene glycol (molecular mass 500 daltons, ALDRICH product no. 475696) are added to this mixture after homogenization, in the case of membrane 2176 0.25 g of epoxide-terminated polyethylene glycol (Molecular mass 6000 daltons, ALDRICH product no. 731803). After homogenization, the polymer solutions are doctored on a glass plate. Thereafter, the solvent is evaporated in a convection oven at 130° C. for a period of 2 hours. The polymer films are then removed under water and after-treated as follows: At 60° C. for 24 hours in a 10% by weight solution of tetramethylimidazole in ethanol At 90° C. for 48 hours in a 10 wt % solution of NaCl in water At 60° C. for 48 hours in deionised water Parts of the membranes are placed in an aqueous 1 M KOH solution for a period of 10 days at a temperature of 90° C.*
Membrane Characterization:

(14) Membrane 2175: ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]: 2.92/2.96 Conductivity before/after KOH treatment*(Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 29.3/72.7 Water uptake at 25° C. before/after KOH treatment*[%]: 367/324 Gel content after extraction in DMAc at 90° C. before/after KOH treatment*[%]: 97.6/100

(15) Membrane 2176: ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]: 2.79/2.84 Conductivity before/after KOH treatment*(Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 21.6/69.9 Water uptake at 25° C. before/after KOH treatment*[%]: 370/313 Gel content after extraction in DMAc at 90° C. before/after KOH treatment*[%]: 97.4/97
Comparison of Characterization Results of Membranes 2175 and 2176

(16) Remarkable and surprising in the two membranes 2175 and 2176 of this application example was that the conductivity of the membranes after 10 days of KOH treatment was significantly higher than before the KOH treatment. Because of this surprising finding, the chloride conductivities were measured in another impedance measurement stand as a function of the temperature in a temperature range between 30 and 90° C. at a constant relative humidity of 90%. The chloride conductivity vs. temperature curves of the two membranes 2175 and 2176 are shown in FIG. 1. It shows, that:

(17) 1) both membranes have nearly equal conductivity curves;

(18) 2) even under these conditions, the conductivities measured after 10 days of KOH incorporation were significantly higher than before, although the molecular masses of the epoxide-terminated polyethylene glycols (PEG) used in membrane production are very different (2175: PEG molecular mass 500 daltons; 2176: PEG molecular mass 6000 daltons).

(19) The gel content of the membranes of almost 100% surprisingly shows a complete formation of the network of these anion exchange blend membranes. Due to the excellent membrane stabilities, the storage time of membrane 2176 in 1M KOH at 90° C. was extended by a further 20 days to a total of 30 days, and the membrane chloride conductivity was determined experimentally after a total of 20 days and after a total of 30 days in the temperature range from 30 to 90° C. under a relative humidity of 90%. FIG. 2 shows the chloride conductivities of the membrane 2176 before and after 10, 20 and 30 days incorporation in 1 M KOH in the temperature range from 30 to 90° C. There was a surprising development: after 10 days, the conductivity of the membrane was greatly increased over before the KOH treatment, and then decreased to a slightly lower level after 20 days compared to before the KOH treatment. This value then no longer changed in the time interval between 20 and 30 days storage in KOH. Since the thermogravimetry (TGA) studies of the membranes can also give indications of degradation processes in the membranes, for the two membranes 2175 and 2176 TGA curves were recorded before and after the KOH treatment. FIG. 3 shows the TGA curves of membranes 2175 and 2176 before and after 10 days of treatment in 1 M KOH at 90° C. From the TGA curves of both membranes no conclusions can be drawn on degradation processes in KOH solution, since the TGA curves of both membranes before and after 10 days of KOH treatment are almost congruent.

(20) To determine if in 2176 membrane degradation occurs during the KOH long-term stability test of the membrane, TGA curves of the 2176 were recorded before and after 10, 20 and 30 days of incorporation in KOH. These TGA curves are shown in FIG. 4. From FIG. 4, it can be seen that the TGA curves of all 4 samples are nearly congruent up to a temperature of about 430° C., from which one can conclude that the 2176 still shows no sign of significant degradation even after 30 days of incorporation into KOH which confirms the results of the conductivity tests.

Example 2: AEM Blend of PVBCI, PBIOO, a Sulfonated Polyethersulfone (SAC098, See Description), Tetramethylimidazole for Quaternization of the PVBCI and an Epoxide-Terminated Polyethylene Glycol Having a Lower AEM Content than in Application Example 1 but the Same Molar Ratio Between PBIOO and PEG-Diepoxid 6000 (Membrane MJK2190A)

(21) Membrane Production and Aftertreatment:

(22) 12 g of a 10% by weight solution of polyvinylbenzyl chloride (ALDRICH product no. 182532, structure as described) in N, N-dimethylacetamide (DMAc) are mixed with 6 g of a 33.3% by weight solution of 1,2,4,5-Tetramethyl-1H-imidazole (TCI product no. T0971, structure see description), 10.34 g of a 10 wt % solution of PBIOO (manufacturer FumaTech, structure see description) and 2.67 g of a 10 wt % solution of a sulfonated polyethersulfone (SAC098, IEC=1.8 meq SO.sub.3H/g, structure see description) mixed in DMAc. After homogenization, 0.386 g of epoxide-terminated polyethylene glycol (molecular mass 6000 daltons, ALDRICH product no. 731803) are added to this mixture. After homogenization, the polymer solution is doctored onto a glass plate. Thereafter, the solvent is evaporated in a convection oven at 130° C. for a period of 2 hours. The polymer film is then removed under water and after-treated as follows: At 60° C. for 24 hours in a 10% strength by weight solution of tetramthylimidazole in ethanol At 90° C. for 48 hours in a 10 wt % solution of NaCl in water At 60° C. for 48 hours in deionised water

(23) Part of the membrane is placed in an aqueous 1M KOH solution for a period of 10 days at a temperature of 90° C.*.

(24) Membrane Characterization: ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]: 2.1/2.7 Conductivity before/after KOH treatment*(Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 14.3/16.3 Water absorption at 25° C. before/after KOH treatment*[%]: 67/90.5 Gel content after extraction in DMAc at 90° C. before KOH treatment [%]: 95.9

(25) As with the membranes 2175 and 2176, the chloride conductivity was also determined in this membrane as a function of the temperature between 30 and 90° C. at a relative humidity of 90%. The conductivity curves are shown in FIG. 5. Surprisingly, the conductivity of the 2190A membrane also increases during KOH treatment. In order to determine the thermal stability of the membrane and possible degradation processes in the membrane, TGA curves of the membrane were recorded before and after 10 days of KOH treatment. The TGA curves are shown in FIG. 6. Also in this membrane, the TGA curves before and after 10 days of KOH treatment almost congruent, at least up to a temperature of about 350° C., indicating that after 10 days of incorporation in 1 M KOH at 90° C. still no significant degradation of the membranes has taken place.

Example 3: AEM Blend of PVBCI, F.SUB.6.PBI, a Sulfonated Partially Fluorinated Aromatic Polyether (SFS001, See Description), Tetramethylimidazole for Quaternization of the PVBCI and a Double-Sidedly Epoxide-Terminated Polyethylene Glycol Having a Molecular Mass of 2000 Daltons (Membrane MJK2215)

(26) Membrane Production and Aftertreatment:

(27) 3 g of a 20% by weight solution of polyvinylbenzyl chloride (ALDRICH product no. 182532, structure see FIG. 2) in dimethyl sulfoxide (DMSO) are mixed with 3 g of a 33.3% by weight solution of 1,2,4,5-tetramethyl 1H-imidazole (TCI Product No. T0971, see FIG. 1 structure), 10.34 g of a 5% by weight solution of F.sub.6PBI (see structure in description) in DMSO and 1.11 g of a 10% by weight solution of a sulfonated partially fluorinated aromatic Polyether (SFS001) in SO.sub.3Li form (IEC=2.39 meq SO.sub.3H/g, structure see description) mixed in DMSO. After homogenization, 0.193 g of epoxide-terminated polyethylene glycol (molecular mass 2000 daltons, ALDRICH product no. 731811) are added to this mixture. After homogenization, the polymer solution is doctored onto a glass plate. Thereafter, the solvent is evaporated in a convection oven at 140° C. for a period of 2 hours. The polymer film is then removed under water and after-treated as follows: At 60° C. for 24 hours in a 10% strength by weight solution of tetramethylimidazole in ethanol At 90° C. for 48 hours in a 10 wt % solution of NaCl in water At 60° C. for 48 hours in deionised water

(28) Part of the membrane is placed in an aqueous 1M KOH solution for a period of 10 days at a temperature of 90° C.*

(29) Membrane Characterization:

(30) ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]: 2.37/2.7
Conductivity before/after KOH treatment*(Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 37.2/29.2 Water uptake at 25° C. before/after KOH treatment*[%]: 56.7/68 Gel content after extraction in DMAc at 90° C. before KOH treatment [%]: 92.7

(31) As with the membranes 2175 and 2176 as well as 2190A, the chloride conductivity was also determined in this membrane as a function of the temperature between 30 and 90° C. at a relative humidity of 90%. The conductivity curves are shown in FIG. 7. Again, as in the previous examples, the chloride conductivity after 10 d storage in 1M KOH at 90° C. is higher than before. In order to determine the thermal stability of the membrane and possible degradation processes in the membrane, TGA curves of the membrane were recorded before and after 10 days of KOH treatment. The TGA curves are shown in FIG. 8. Also in this membrane, the TGA curves before and after 10 days of KOH treatment almost congruent, at least up to a temperature of about 350° C., indicating that after 10 days of incorporation in 1M KOH at 90° C. still no significant degradation of the membranes has taken place.

Comparative Example 1: AEM Blend of PVBCI, PBIOO, a Sulfonated Polyethersulfone (SAC098, See Description), Tetramethylimidazole for Quaternization of the PVBCI with the Same Calculated IEC as the Membranes MJK2175 and MJK2176, but without PEG Diglycidyl Ether (Membrane 2179B)

(32) Membrane Production and Aftertreatment:

(33) 6 g of a 10% by weight solution of polyvinylbenzyl chloride (ALDRICH product no. 182532, structure see description) in DMSO are mixed with 2.2 g of a 33.3% by weight solution of 1,2,4,5-tetramethyl-1H-Imidazole (TCI product no. T0971, see structure for description) in DMAc, 4.6 g of a 10% strength solution of PBIOO (manufacturer FumaTech, structure see description) in DMAc and 1.335 g of a 10% by weight solution of a sulfonated polyethersulfone (SAC098, IEC=1.8 meq SO.sub.3H/g, structure see description) mixed in DMAc. After homogenization, the polymer solutions are doctored on a glass plate. Thereafter, the solvent is evaporated in a convection oven at 140° C. for a period of 2 hours. The polymer films are then removed under water and after-treated as follows: At 60° C. for 24 hours in a 10% strength by weight solution of tetramethylimidazole in ethanol At 90° C. for 48 hours in a 10 wt % solution of NaCl in water At 60° C. for 48 hours in deionised water Parts of the membranes are placed in an aqueous 1 M KOH solution for a period of 10 days at a temperature of 90° C.*
Membrane Characterization: ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]: 2.5/2.64
Conductivity before/after KOH treatment*(Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 10.7/15.9 Water uptake at 25° C. before/after KOH treatment*[%]: 63/87
Gel content after extraction in DMAc at 90° C. before KOH treatment*[%]: 94.2

(34) If these data are compared with those of membranes 2175 and 2176, the following results: The Cl— conductivity is much lower than in the two membranes of the invention. This shows what a positive influence the addition of a hydrophilic PEG phase has to the membrane Water uptake is significantly lower than at 2175 and 2176. This can be explained by the lower hydrophilicity of the control membrane.

(35) Since the Cl conductivity of the 2179B was higher in conductivity measurement at room temperature and in 0.5N NaCl as at 2175 and 2176 after the KOH treatment, the impedance of the 2179B was again measured in dependence of the temperature at a relative humidity of 90%. The conductivity curve of the 2179B under these conditions is shown in FIG. 9. Here, it is found that, as in the impedance measurement at room temperature in 0.5M NaCl, the chloride conductivity is much lower than that of the 2175 and 2176 containing a PEG phase and that the impedance after KOH treatment is significantly lower than before. Since at 2175 and 2176 the chloride conductivity was higher after 10 d KOH treatment than before, on the one hand shows the conductivity-increasing effect and on the other hand, the stabilizing effect of the presence of a PEG microphase in the blend AEMs.

Comparative Example 2: AEM Blend of PVBCI, F.SUB.6.PBI, a Sulfonated Partially Fluorinated Polyether (SFS001, See Description), Tetramethylimidazole for Quaternization of PVBCI with the Same Calculated IEC as the Membrane MJK2215, but without PEG Diglycidyl Ether (Membrane 2216)

(36) Membrane Production and Aftertreatment:

(37) 3 g of a 20% by weight solution of polyvinylbenzyl chloride (ALDRICH product no. 182532, structure as described) in DMSO are mixed with 3 g of a 33.3% by weight solution of 1,2,4,5-tetramethyl-1H-imidazole (TCI Product No. T0971, structure see description) in DMSO, 14.2 g of a 5 wt % solution of F.sub.6PBI (structure see description) in DMSO and 1.1 g of a 10 wt % solution of the sulfonated polyether SFS001 (IEC=2.39 meq SO.sub.3H/g, structure see description) mixed in DMSO. After homogenization, the polymer solutions are doctored on a glass plate. Thereafter, the solvent is evaporated in a convection oven at 140° C. for a period of 2 hours. The polymer film is then removed under water and after-treated as follows: At 60° C. for 24 hours in a 10% strength by weight solution of tetramethylimidazole in ethanol At 90° C. for 48 hours in a 10 wt % solution of NaCl in water At 60° C. for 48 hours in deionised water Parts of the membranes are placed in an aqueous 1 M KOH solution for a period of 10 days at a temperature of 90° C.
Membrane Characterization: ion exchange capacity before/after KOH treatment*[meq OH—/g membrane]:
2.48/2.7 Conductivity before/after KOH treatment (Cl— form, measured in 0.5N NaCl at room temperature) [S/cm]: 7.4/8.2 Water absorption at 25° C. before/after KOH treatment [%]: 44/33 Gel content after extraction in DMAc at 90° C. before KOH treatment*[%]: 95.7 If these data are compared with those of the membrane 2215, the following results: The Cl— conductivity at room temperature in 0.5N NaCl is significantly lower than in the inventive membrane 2215. This shows the positive influence of the addition of a hydrophilic PEG phase has to the membrane. The water absorption is significantly lower than at 2215. This can be explained by the lower hydrophilicity of the control membrane.

(38) Since the Cl conductivity of the 2216 was higher in the conductivity measurement at room temperature and in 0.5N NaCl as in 2215 after the KOH treatment, the impedance of the 2215 was again measured as a function of the temperature at a relative humidity of 90%. measured. The conductivity curve of the 2215 under these conditions is shown in FIG. 10. Here it can be seen that, as in the impedance measurement at room temperature in 0.5M NaCl, the chloride conductivity is much lower than in the 2215 containing a PEG phase, and that the impedance after the KOH treatment is significantly lower than before. Comparative Example 2 shows, as in Comparative Example 1, on the one hand, the conductivity-increasing effect and, on the other hand, the stabilizing effect of the presence of a PEG microphase in the blend AEMs.

Comparative Example 3: Commercial Anion Exchange Membrane A201 (Development Code A006) of the Manufacturer Tokuyama

(39) The structure of this membrane is company secret. The anion exchange group of this membrane is the trimethylammonium group. But it is obviously a cross-linked membrane because the extraction of the membrane gave a gel content of 95%.

(40) Membrane characterization: Ion exchange capacity [meq OH/g membrane]: 1.7 Conductivity (Cl— form, measured in 1 N NaCl at room temperature) [S/cm]: 12 Water absorption at 30° C. [%]: 19 Gel content after extraction in DMAc at 90° C. before KOH treatment*95 Conductivity (Cl— form, measured at 90° C. and 90% relative humidity, after 10 d incorporation in 1M KOH at 90° C.): 21% of the original conductivity

(41) This commercial membrane is thus much less stable in 1M KOH at 90° C. compared to the membranes of the invention. In addition, the chloride conductivity of this membrane is substantially lower than most of the membranes of this invention listed as examples in this chapter. The chloride conductivity of the A201 in the temperature range of 30 to 80° C. at 90% relative humidity is shown in FIG. 11.

Comparative Example 4: Commercial Anion Exchange Membrane FAB from the Manufacturer Fuma-Tech

(42) The structure of this membrane is company secret. But it is obviously a cross-linked membrane, as the extraction of the membrane gave a gel content of 93.3%.

(43) Membrane Characterization:

(44) Ion exchange capacity before/after 10 d in 1 M KOH at 90° C. [meq OH—/g membrane]: 0.88/0.89 Conductivity before/after 10 d in 1M KOH at 90° C. (Cl— form, measured in 1 N NaCl at room temperature) [S/cm]: 4/3.2 Water absorption at room temperature/at 90° C. ° C. [%]: 12.1/13.2

(45) Gel content after extraction in DMAc at 90° C. before/after KOH treatment*[%]: 93.3/97

(46) The chloride conductivity of this membrane is substantially lower than that of most of the membranes of this invention listed as examples, which is also (among others) because this membrane is fabric-reinforced.