Claimed are the following types of composite membranes:
1. Composites or composite membranes by addition of a metal salt, e.g. ZrOCl2, in a solvent, e.g. DMSO, to a solution of one or more polymers in an organic solvent or in aqueous systems as well as the subsequent precipitation in the matrix of the hence produced composite membrane by post-treatment in an acid or in a salt solution, e.g. phosphoric acid.
2. Composites or composite membranes by subsequent ion exchange of finished polymer membranes with a suitable salt cation, e.g. ZrO2+, whereas the polymer membrane if necessary is swollen prior to ion exchange with an organic solvent or a mixture of organic solvent with water as well as the subsequent precipitation of a sparingly soluble salt, e.g. of Zr3(PO4)4, in the membrane by post-treatment in an acid or in a salt solution, e.g. phosphoric acid.
3. Composites or composite membranes by addition of nano-size Zr3(PO4)4-powder to a polymer solution.
4. Claimed are also composites or composite membranes, which are produced as in 1. and/or 2. and/or 3, whereas additionally hetero polyacids are incorporated into the polymermorphologie or the membranemorphologie.
Claimed are also processes to produce polymers and membranes according to the invention.
Composite membranes from organic polymers and inorganic fillers have been described often, and in fact in journals as well as in patents. A patent example, which contains also many hints to other developments in composite membrane s, is a U.S. patent of Lynntech, Inc.1. In this patent however no composite membranes are described, whose organic phase is ionically and/or covalently cross-linked, as is the case in the present invention. In2 composite membranes from Nafion® and zirconiumphosphate are described, where the zirconiumphosphate has been incorporated subsequently into the membrane by 1) ion exchange H+ against Zro2+ in the Naflon®-membrane, 2) Soaking of the ionexchanged Nafion®-membrane in phosphoric acid and precipitation of ZrO2+-ions in the membrane matrix as Zr-phosphates. Disadvantage of the method is however that only as much Zr-phosphate can be precipitated in the membrane, as are SO3H-groups in the Nafion®-matrix. Also own developments in this field have been filed as patent: first composite-membranes from organic polymers and organic polymer blends containing cation exchange groups and/or basic groups alternatively non ionic precursors of cation exchange groups, whereas acid-base-blends are preferred, and inorganic compounds, whereas the inorganic compounds are incorporated in the membrane matrix as organometalic compounds (such as e.g. metal acetylacetonates, metal alkoxides) and are hydrolysed in the membrane matrix to the respective metaloxide or metalhydroxide3,4. The materials according to the invention respectively processes to produce the polymers and membranes according to the invention as described in this invention have not been described in the above mentioned own patent applications. A further group of composite membranes are composites from sulfonated poly(etherketones) and the hetero polyacids phosphoric tungsten acid hydrate H3PW12O40x29 H2O (TPA) and molybdatophosphoric acid hydrate H3PMo12O40x29 H2O (MPA) as well as the disodium salt of TPA (Na-TPA)5. In this publication no ionically and/or covalently cross-linked ionomer membranes have been described as is the case in the present invention.
1 U.S. Pat. No. 6,059,943, O. J. Murphy, A. J. Cisar, Lynntech, Inc. (2000)
2C. Yang, et al., Electrochem. Solid St. Lett. 4(4) A31-A34 (2001)
3 Jochen Kerres, German patent application 10021106 from 2.5.2000
4 Jochen Kerres, Thomas Häring, German patent application 10021104 from 2.5.2000
5S. M. J. Zaidi, S. D. Mikhailenko, G. P. Robertson, M. D. Guiver, S. Kaliaguine, J. Memb. Sci. 173, 17-34 (2000)
It has been found surprisingly, that composites oder composite membranes made from polymer metal salt or polymer metal oxide or polymer metal hydroxide can be produced with the following method method 1 in the most general embodiment:
Furthermore it has been found surprisingly, that composites or composite membranes made from polymer metal salt or polymer metal oxide or polymer metal hydroxide can be produced with the following method method II in the most general embodiment:
Thereby it has been found surprisingly, that the production processes Method I and Method II can be combined as follows:
First the composite film is produced according to Method I. Then the process is carried out according to methode II starting from II.5. Thereby multinary composite films are formed, which due to the incorporation of inorganic components into the various areas of the polymermorphologie show very good mechanical and thermal stability as well as very good ion conductivity and in use in direct methanol fuel cells also very good methanol retention. The advantages of the composite membranes produced according to Method I or Method II or a combination of Method I with Method II are:
The components of the composite membranes according to the invention are defined as follows:
(1) Main Chains (Backbones) of Polymers According to the Invention:
As polymer main chains all polymers are possible. Preferred as main chains are however:
Especially preferred are (Het)arylmain chain polymers such as:
Polymertyp A comprises all polymers, composed from the above mentioned Polymermain chains (1) and the following cation exchange groups or their non ionic precursors:
SO3H, SO3Me; PO3H2, PO3Me2; COOH, COOMe
SO2X, POX2, COX with X represents Hal, OR2, N(R2)2, anhydride radical, N-imidazolee radical
N-pyrazole radical
Polymertyp B comprises all polymers, composed from the above mentioned (1) and from the following anion exchange groups or their non-ionic precursor (with primary, secondary or tertiary basic N):
N(R2)3+Y−, P(R2)3+Y−, whereat R2 radicals can be the same or different from each other;
N(R2)2 (primary, secondary or tertiary amines);
Polymere with N-basic (Het)aryl- and Heterocyclic groups as in
As polymer main chains preferred are (Het)aryl main chain polymers such as poly(etherketones), poly(ethersulfones) and poly(benzimidazolee). As basic groups preferred are primary, secondary and tertiary amino groups, pyridyl groups and imidazolee groups.
(4) Polymers of typs C (Polymers with Cross-Linking Groups Such as Sulfinate Groups and/or Unsaturated Groups):
Polymertyp C comprises all polymers composed from the above mentioned polymer main chains (1) and cross-linking groups. Cross-linking groups are e.g.:
4a) alkene groups: polymer-C(R13)═C(R14R15) with R13, R14, R15═R2 or R4
4b) polymer-Si(R16R17)—H with R16, R17═R2 or R4
4c) polymer-COX, polymer-SO2X, polymer-POX2
4d) sulfinate groups polymer-SO2Me
4e) polymer-N(R2)2 with R2≠H
Thereby one or more of the mentioned cross-linking groups can be present on the polymer main chain. The cross-linking can be carried out according to the following reactions known from the literature:
Thereby the cross-linking reactions (III), (IV) and (V) are preferred, especially the cross-linking reaction (III).
(5) Polymers of typ D (Polymers with Cation Exchange Groups and Anion Exchange Groups and/or Basic N-Groups and/or Cross-Linking Groups):
Polymertyp D comprises all polymers carrying the main chains from (1), which can carry different groups: cation exchange groups or their nonionic precursors as in (2) and anion exchange groups or primary, secondary or tertiary N-basic groups as in (3) and/or the cross-linking groups as in (4).
The following combinations are possible:
The covalently cross-linked (blend)membranes can consist of the following components:
As main chains (1) aryl main chain polymers are preferred and especially poly(etherketones) or poly(ethersulfones), as cation exchange groups (2) SO3H-groups or phosphonic acid groups or their non-ionic precursors, and as cross-linking groups (4) SO2Me-groups. As cross-linking agents dihalogenalkane- or dihalogenaryl compounds are preferred. Especially preferred as cross-linking agents are Hal-(CH2)x-Hal, x represents a number between 3 and 20, with Hal═I, Br, Cl, F.
(6.2) Ionically Cross-Linked (Blend)Membranes:
The ionically cross-linked (blend)membranes can consist of the following components:
As main chain (1) aryl main chain polymers are preferred and especially poly(etherketones) or poly(ethersulfones), as cation exchange groups (2) SO3H-groups or phosphonic acid groups or their non-ionic precursors.
(6.3) Covalent-Ionically Cross-Linked (Blend)Membranes:
The covalently-ionically cross-linked (blend)membranes can consist of the following components:
As main chains (1) aryl main chain polymers are preferred and especially poly(etherketones) or poly(ethersulfones), as cation exchange groups (2) SO3H-groups or phosphonic acid groups or their non-ionic precursors, and as cross-linking groups (4) SO2Me-groups. As cross-linking agents dihalogenalkane- or dihalogenaryl compounds are preferred. Especially preferred as cross-linking agents are Hal-(CH2)x-Hal, x represents a number between 3 and 20, with Hal═I, Br, Cl, F.
(7) Solvent L1:
(7.1) Protic Solvents:
Water, alcoholes (e.g. methanol, ethanol, n-propanol, i-propanol, tert. butanol); aqueous and/or alcoholic metal salt solutions, aqueous and/or alcoholic lowmolecular polymer solutions conataining cation exchange groups;
(7.2) Dipolar-Aprotic Solvents:
acetone, methylethylketone (MEK), acetonitrile (ACN), N-methylformamide, N,N-dimethylformamide (DMF), N-methylacetamide, N,N-dimethylacetamide (DMAc), N-methylpyrrolidinone (NMP), dimethylsulfoxide (DMSO), sulfolane;
(7.3) Ether Solvents:
tetrahydrofurane, oxane, dioxane, glyme, diglyme, triglyme, tetraglyme, diethylether, di-tert. Butylether.
(8) Metal Oxide Powder, Metal Salt Powder or Metal Hydroxide Powder, Especially Preferred are Nano-Sized Powder:
Water containing particles, carrying OH-groups on their surface, preferably based on Al2O3 (bayerite, pseudobohmite, gibbsite=hydrargillite, diaspor, böhmit), as well as vanadium- or tungsten-based oxides (V2O5, VOx, WOx) or alloys from these oxides:
As preferred component Me in Me2O Na or K is used. The produced, alkali containing compounds have to be ion exchanged before they can be used for the membrane. In doing so the alkali ion is removed and the protonated form is generated.
with Me = Na, K, z = 0.7-1.2.
(with x = 0.1-10, y = 0.1-10), stable until appr. 300° C.
Especially preferred are the oxides TiO2, ZrO2 and Al2O3 and the sparingly soluble metal phosphates Zr3(PO4)4 and ZrP2O7 and zirconhydrogenphosphates.
(9) (Hetero)Polyacids and their Salts:
As (Hetero)polyacids can be used: polyphosphoric acid and heteropolyacids such as phosphor-tungsten-acid hydrate H3PW12O40x29H2O (TPA) and molybdatophosphoricacid hydrat H3PMo12O40x29 H2O (MPA) as well as the alkalimetalsalts of heteropolyacids such as e.g. the disodiumsalt of TPA (Na-TPA).
(10) Metal Salts Me+X− and Covalent Metal Compounds:
The metal salts are salts of transition metal cations (e.g. of metals Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Sn, Nb, Mo, Ce, Ta, W, Sm, Eu, Gd, Yb, La) or transition metal oxycations such as Zro2+, TiO2+, and anions of mineral acids, such as e.g. Hal− (Hal═F, Cl, Br, I) or SO42−, which are in solvents L2 (see below) soluble. As metal salts are especially preferred ZrOCl2, ZrOSO4, TiOCl2, TiOSO4, ZrCl4 or TiCl4.
(11) Organic Solvent L2:
As organic solvent for the metal salts (10) mainly dipolar-aprotic solvents are suitable. As solvent L2 is DMSO especially preferred.
(13) Cation Exchange Counter Ions C+:
As C+ are in principal all dissociating cations suitable. Preferred are however alkalimetal cations or primary, secondary or tertiary ammoniumions or pyrazolium- or imidazoleiumions as well as pyridiniumions.
(14) Basic Metal Hydroxides MOH or Amines:
Suitable basic metal hydroxides are the alkali hydroxides or the alkaline-earth hydroxides, thereby NaOH and KOH are preferred. Suitable amines are ammonia or triethylamine.
(15) Sparingly Soluble Metal Oxides MemOn:
All in (8) mentioned oxides are in principle suitable as sparingly soluble metal oxides. Preferred are however the in part water-containing oxides, which form by reaction of compounds (10) with the aqueous bases (14). Thereby are especially preferred TiO2 or ZrO2.
Sparingly Soluble Metal Hydroxides Mem(OH)n:
All in (8) mentioned hydroxides are in principle suitable as sparingly soluble metal hydroxides.
Mineral Acid HY:
Mono-, di- or polyphosphoric acid or heteropolyacids or sulfuric acid are suitable as mineral acids. Preferred is however ortho-phosphoric acid.
1. Acid-Base-Blend-Composite-Membranes by Addition of a Solution of ZrOCl2*8H2O in Dimethylsulfoxide to the Polymer Solution
Preparations:
In this work blend membranes from sulfonated poly(etherketon) PEK (S-PEK; IEC=1,8 meq SO3H/g Polymer) and PBI (IEC=6,5 meq basic N/g Polymer) as acid respective base component are produced. Another base (imidazolee) is used to neutralise S-PEK. As inorganic material, which is incorporated into the membranes, ZrOCl2*8H2O has been chosen. S-PEK and Imidazole are used as 10% solutions in NMP. A 9,5% PBI solution in DMAc was made. Due to the solubility and mixability with polymer solutions ZrOCl2*8H2O was dissolved in DMSO (also 10%).
To produce clear membranes, all solutions have been filtered to seperate floating particles.
Membrane Production:
S-PEK solution was neutralised with imidazolee (solution 3), then PBI (solution 2) added and stirred. Then ZrOCl2*8H2O was added and stirred. For comparaison a membrane was made (CPM2) from a solution without addition of ZrOCl2*8H2O. The polymer solution was cast on a glassplate and coated with a doctor knife (1,0 mm notch). The glass plate was immediately stored in a drying oven at 120° C. for 3 h and then over night a vacuum applied. The glass plate was cooled to room temperature and finally to remove the membrane placed for some minutes in water. The membrane was cut into 3 sections and marked as A, B or C. The sections have been post-treated as followed:
The reference membrane CPM2 was treated as C, because it does not contain inorganic material.
The following membranes according to Table 1 were made:
(Reference)
#To neutralise the poly(etherketonsulfonic acid) SPEK
*Based to S-PEK and PBI
Results:
Swelling:
If the quantity of ZrOCl2*8H2O is doubled (CPM4), the membrane reacts as follows: between 25° C. and 90° C. almost no water is taken up.
The presence of the inorganic components causes apparently and surprisingly a stabilisation of the swelling over a wide temperature range.
In both cases (CPM1 and CPM4) the membrane sections treated with NaOH show the least swelling followed by those treated in H3PO4. The biggest water up-take capacity show the membranes post-treated in NaOH and then in H3PO4.
Determination of Residue with TGA:
With thermal gravimetric analysis (TGA) the residues of the mentioned membranes have been measured. First small membrane sections are dried at 100° C. for 3 days in a drying oven. Then they are cut for the thermo balance. They are heated with a heating rate of 20 K/min. under oxygen.
Table 2 shows the calculated and experimentally found residues of the membranes.
*A: treated NaOH,
*B: treated NaOH/H3PO4,
C: treated H3PO4
Membranes of the row A, post-treated in NaOH and according to equation 1 contain ZrO2 as residue, show a good match of the calculated value with the experimental result. (CPM1-A: 5,0%/5,4%; CPM4-A: 9,4%/8,1%).
When the zirkonoxidaquat, which is formed according to eq (1) during post-treatment, is treated with phosphoric acid (membrane section B), first an adsorption takes place6, which is slowly superposed by the formation of zirconphosphate (eq.2). The adsorption compound contains (formally) ZrO2 and P2O5, which releases on rinsing (formally) P2O5.
6 E. Wedekind, H. Wilke, Koll.-Z. 34 [1924] 283/9, 284
During the annealing of the zirconphosphate as residue according to7 remains zirkonylmetaphosphate ZrO(PO3)2. J. H. De Boer8 however understands the residue as diphosphate (ZrP2O7). Independently from the different views both formulae are identical for the explanation of the analytical results. As a result the residue of the B row is ZrO(PO3)2 or ZrP2O7.
7 G. v. Hevesy, K. Kimura, Z.anorg.Ch. 38 [1925] 774/6; J. Am. Soc. 47 [1925] 2540/4
8 J. H. De Boer, Z. Anorg. Ch. 144 [1925] 190/6
Based on the assumption that (formally) P2O5 is rinsed out partly during post-treatment, the experimentally found residue for CPM1-B of 7,9% corresponds to a value between pure ZrO2 and ZrO(PO3)2. However the high residue for CPM4B can not be explained in this way. The zirconphosphate (membrane section C) directly obtained with H3PO4 from the solutions of Zr salts behaves differently. Due to the great stability of the ZrO2+ ion and the practical nonexistence of Zr4+ ions in aqueous solutions G. v. Hevesy and K. Kimura7 consider the formula ZrO(H2PO4)2 as propable. In this case P2O5 (formally) can not be rinsed out6. The zirkonyldihydrogenphosphate transforms on annealing to metaphosphate ZrO(PO3)2. The observed residues for CPM1C and CPM4C compare well with the theoretical value for ZrO(PO3)2 (CPM1-C: 14,8%/11,1%, CPM4-C: 15,9%/16,1%).
7 G. v. Hevesy, K. Kimura, Z.anorg.Ch. 38 [1925] 774/6; J. Am. Soc. 47 [1925] 2540/4
6 E. Wedekind, H. Wilke, Koll.-Z. 34 [1924] 283/9, 284
The reference membrane CPM2 does not show a residue due to no inorganic components.
Ionic Capacity and Specific Resistance
The ionic capacity of a membrane is determined by soaking a membrane piece in an aqueous saturated sodium chloride solution. An ion exchange takes place Na+ ion diffusing into the membrane, and displacing H+ ions. The protons present in solution are titrated with NaOH to the equivalence point. From the consumed quantity of NaOH the direct ion capacity can be (IECdirect) calculated. It corresponds to the number of free protons in the membrane. If overtitrated with NaOH, the ionic interaction of the membrane is broken. The overtitrated NaOH determined by backtitration corresponds to the quantity of ionic interaction and contributes to the total ion capacity (IECoverall).
Table 3 shows the experimental and theoretical ion capacity of the membranes CPM1, CPM2 and CPM4.
*A: treated NaOH,
*B: treated NaOH/H3PO4,
C: treated H3PO4
For the calculation of the theoretical ion capacity of the row A (NaOH post-treatment) zircondioxide according to eq. (2) is taken into account among S-PEK and PBI in the matter balance, and for the row C(H3PO4 post-treatment) ZrO(H2PO4)2 according to eq (3). Moreover the protons of dihydrogenphosphate are taken into account for the total ion capacity. There is no calculation for membranes of the row B (NaOH—H3PO4 post-treatment) because from eq. (2) is not known how much (formally) P2O5 is rinsed out. The IEC of this row of membranes must be intermediate compared to the IEC of the row A and C.
Good agreement between the theoretical and experimental IEC show membranes with inorganic component (CPM1 and CPM4) as well as the reference membrane without zircon compound (CPM2). Solely for the membranes post-treated with NaOH (row A) greater differences (marked in bold) are found.
Striking is the big difference between the IECdirect and IECoverall. of CPM1-C and CPM4-C (circa 1,5 meq SO3H/g/g) as compared to the reference membrane (circa 0,6 meq SO3H).
It is ascribed to the zircondihydrogenphosphate contained in these membranes, which releases both protons only in neutral to strongly basic medium9, and are therfore only taken into account during the determination of the total ion capacity.
9 Holleman, Wiberg, Lehrbuch der Anorganischen Chemie, 91.-100. [1985] 653
These additional protons provided by the dihydrogenphosphate should decrease strongly the ionic resistance of the membrane. The resistance of membranes of row C should therefore be smaller than those of row A and B. The experimental fact however show a reversed picture.
The reason of this discrepancy lies in the routine sample preparation for the determination of the membrane impedancy. For this purpose the membranes are cut into small pieces (ca. 1,5 cm×1,5 cm) and conditioned in 1N H2SO4. In this acidic medium the specific resistance is determined.
According to10 zirconium sulphate Zr(SO4)2*4H2O is formed from a solution containing ZrO2 and excess H2SO4. This exists in aqueous solution as a complex zirconium oxide sulphuric acid having the formula H2[ZrO(SO4)2] and dissociates under liberation of protons according to equation 4.
10 Gmelin, Handbuch Syst. Nr. 42 [1958] 337
Presumably the same reaction occurs in the membranes of the series A and partially also in in the series B. In both cases the sulphuric acid is bound in the membrane matrix and leads to a strong decrease of resistance. Due to the fact that sulphuric acid is a strong acid the effect is the more marked.
The experimentally determined membrane impedance reflects therefore not the actual ionic resistance, because it is falsified by the presence of sulphuric acid.
It is unclear whether the ions formed by the dissociation remain in the membrane and perpetuate the state of high protone conductivity, or are washed out with time.
The sparingly soluble zirconium dihydrogen phosphate in CPM1-C and CPM4-C is not influenced by this reaction10 [5]. In the dihydrogen phosphate protons are present, they are however tightly bound and have less influence onto the proton conductivity than zirconium oxide sulfuric acid.
10 Gmelin, Handbuch Syst. Nr. 42 [1958] 337
It is certain that composite membranes of this type have a smaller ionic resistance than a entirely organic membrane.
Summary:
1) Optical appearance of the membranes:
Investigated Membranes:
aImpedance, measured between 2 Nafion ® 117 membranes in water
bImpedance, measured between 2 Nafion ® 117 membranes in 0.5N HCl
cCross-linking via alkylation of sulfinate groups with 1,4-diiodbutane11
dIonical cross-linking via proton transfer of SO3H-group onto basic imidazole-N
esulfonated poly(etherketon)e Victrex ®
fsulfinated PSU, prepared via reaction of lithiated PSU with SO212
gsulfonated poly(etherethe rketon)e Victrex ®
hPolybenzimidazole Celazol ®
iprepared via reaction of lithiated PSU with bis(diethylamino)benzophenone13
11Jochen Kerres, Wei Cui, Martin Junginger, J. Memb. Sci. 139, 227-241 (1998)
12J. Kerres, W. Cui, S. Reichle, J. Polym. Sci.: Part A: Polym. Chem. 34, 2421-2438 (1996)
13J. Kerres, A. Ullrich, M. Hein, J. Polym. Sci.: Part A: Polym. Chem. 39, 2874-2888 (2001)
Preparation of Post-Treatment-Solution:
Results of Resistance Measurements of the Membranes with the Respective Posttreatment:
From the table can be seen (apart from run-offs) that the resistance of the membranes is decreasing with an increasing portion of NMP in the 1 molar ZrOCl2-solution The run-offs can result from the fact that the membrane-posttreatment was performed at room temperature, leading to limited accessibility of the membrane for the ion-exchange and precipitation reaction
2. Composite Membranes Via Subsequent Ion-Exchange/Precipitation in Preformed Binary Arylene Main-Chain Polymer Blend Membranes, into which Nano-Scaled Zirconium Phosphate “ZrP” was Mixed Prior to Membrane Preparation
A Preparation of Composite Membranes Via Mixture of ZrP-Powder in Polymer Solutions, which Contain an Acidic (sPEK) and a Basic Polymer (PBI)
The polymer solutions are prepared in mass relation as indicated in the table. Subsequently the anorganic “ZrP” powder is added to the polymer solution
*sulfonated polyetherketone (Producer: Victrex), IEC = 1.8 meq SO3H/g
**Polybenzimidazole Celazol (Producer: Celanese)
***ZrP: finely dispersed layered zirconium phosphate, prepared via precipitation from ZrOCl2, from the group of Prof. Linkov, University of the Western Cape, South Africa
All solutions are warmed onto the magnetic stirrer prior to casting and are processed when warm.
800 μm-doctor knife, 2 membranes per glass plate, 2 h at 130° C./800 mbar, then vacuum 2 h/130° C., remove in H2O, 2 d posttreatment with 10% HCl at 90° C., neutral-washing and 1 post-treatment at 60° C. in H2O.
The sensoric check of the membranes yields:
B Change of the Membrane-Conductivity Via Subsequent Introduction of Zirconium Compounds
Pieces of the membranes are swollen for 24 h at 60° C. in a solution of 30% NMP/70% H2O The so-treated membranes are immersed in a 1 M ZrOCl2 solution und again treated for 24 h at 60° C. to exchange the H+-ions of the sulfonic acid groups with Zr4+. The membranes are washed with H2O and are subsequently cut into 2 similarly big pieces (A+B). The Membranes A are treated in a 10% H3PO4-soln for 24 h at 60° C. (column “H” in table), the Membranes B referring in 10% NaOH (column “N” in table). The pieces are again washed with H2O and heated for 24 h at 60° C. with 10% HCl to, transform them into the SO3H-form. After the washing with H2O small pieces are cut off to measure with them the swelling (25-, 40-,60- and 90° C.), conductivity (only in HCl) and IEC. The further membrane pieces are again immersed in ZrOCl2 at 60° C. for 24 h, then treatment analogous to the first sequence.
“2” means: respective property of the membrane after the 2. ZrOCl2—H3PO4— or ZrOCl2—NaOH-posttreatment
4. Composite Membranes Viasubsequent Ion-Exchange/Precipitation in Preformed Ternary Arylene Main-Chain Polymer Blend Membranes, into which was Mixed a Zirconium Phosphate “ZrP” as Nano-Scaled Powder Prior to Membrane Preparation
a Preparation of Composite Membranes Via Mixture of ZrP-Powder in Polymer Solutions, Containing an Acidic Polymer (sPEK) and Two Basic Polymers (PBI and PSU-Ortho-Sulfone-(C(Oh)(4-diethylaminophenyl)2)
The polymer solutions are prepared in the mass relations which are indicated in the table. Subsequently the inorganic “ZrP” powder is added to the polymer solution.
*sulfonated Polyetherketone (Producer: Victrex), IEC = 1.8 meq SO3H/g
**Polybenzimidazole Celazol (Producer: Celanese)
***ZrP: finely dispersed layered zirconium phosphate, prepared via precipitation from ZrOCl2, from the group of Prof. Linkov, University of the Western Cape, South Africa
****structure-formula:
All solutions are warmed onto the magnetic stirrer prior to casting and are processed when warm.
60-doctor knife, 2 membranes per glass plate, 2 h at 130° C./800 mbar, then vacuum 2 h/130° C., remove in H2O, 2 d posttreatment with 10% HCl at 90° C., neutral washing and 1 post-treatment at 60° C. in H2O
The sensoric check of the membranes yields:
b Change of the Membrane-Conductivity Via Subsequent Introduction of Zirconium Compounds
Pieces of the membranes are swollen for 24 h at 60° C. in a solution of 30% NMP/70% H2O The so-treated membranes are immersed in a 1 M ZrOCl2 solution und again treated for 24 h at 60° C. to exchange the H+-ions of the sulfonic acid groups with Zr4+. The membranes are washed with H2O. The membranes are treated in a 10% H3PO4-soln for 24 h at 60° C.
The pieces are again washed with H2O and heated for 24 h at 60° C. with 10% HCl to, transform them into the SO3H-form. After the washing with H2O small pieces are cut off to measure with them the swelling (25-, 40-,60- and 90° C.), conductivity (only in HCl) and IEC.
“0” means: respective property of the membrane before ZrOCl2-H3PO4-posttreatment
“1” means: respective property of the membrane after the 1. ZrOCl2—H3PO4-posttreatment
5. Composite Membranes Via Subsequent Ion-Exchange/Precipitation in Preformed Ionically and/or Covalently Cross-Linked Arylene Main-Chain Polymer Blend Membranes
5.1 Membrane Preparation
5.1.1 Membrane 1202
The following polymers are mixed as 15 wt % solutions in N-methylpyrrolidinone (NMP):
After the homogenisation 0,7 ml diiodbutane are syringed into the polymer solution. After that a thin film of the polymer solution is cast onto a glass plate with a doctor knife to a thin film. The solvent is evaporated in a vacuum drying oven following the following method:
Subsequently the glass plate with the membrane is removed fom the drying oven, and after cooling down it is immersed in a water bath. There the membrane comes off the glass plate. The membrane is posttreated in the following manner:
1) 48 h at 25° C. in 10% NaOH
2) 48 h at 90° C. in 7% HCl
3) 48 h at 60° C. in H2O
Then the membrane is characterized.
5.1.2 Membrane 1203
The following polymers are mixed as 15 wt % solutions in N-methylpyrrolidinone (NMP):
After the homogenisation 0,7 ml diiodbutane are syringed into the polymer solution. After that a thin film of the polymer solution is cast onto a glass plate with a doctor knife to a thin film. The solvent is evaporated in a vacuum drying oven following the following method:
Subsequently the glass plate with the membrane is removed from the drying oven, and after cooling down it is immersed in a water bath. There the membrane comes off the glass plate. The membrane is posttreated in the following manner:
1) 48 h at 25° C. in 10% NaOH
2) 48 h at 90° C. in 7% HCl
3) 48 h at 60° C. in H2O
Then the membrane is characterized.
5.1.3 Membrane 1204
At first 4 g sulfonated PEKEKK are dissolved to a 15 wt % solution in NMP, then 1,95 g carbonyldiimidazole are added to the solution to mask the SO3H group. Then 1,95 g PSU-ortho-sulfone(C(OH)CH3(4-Pyridyl))1,5 are added as a 15 wt % solution to the reaction mixture.
After the homogenisation a thin film of the polymer solution is cast onto a glass plate with a doctor knife to a thin film. The solvent is evaporated in a vacuum drying oven following the following method:
Subsequently the glass plate with the membrane is removed from the drying oven, and after cooling down it is immersed in a water bath. There the membrane comes off the glass plate. The membrane is posttreated in the following manner:
1) 48 h at 25° C. in 10% NaOH
2) 48 h at 90° C. in 7% HCl
3) 48 h at 60° C. in H2O
Then the membrane is characterized.
5.1.4 Membrane 1205
At first 4 g sulfonated PEKEKK are dissolved to a 15 wt % solution in NMP, then 1,95 g carbonyldiimidazole are added to the solution to mask the SO3H group. Then 1,95 g PSU ortho-sulfone(C(OH)CH3(4-Pyridyl))1,5 are added as a 15 wt % solution to the reaction mixture. Subsequently still 2,6 g PSU(SO2Li) (1 group per repeating unit) are added to the solution, and finally 0,48 ml 1,4-diiodobutane are syringed into the reaction mixture.
After the homogenisation a thin film of the polymer solution is cast onto a glass plate with a doctor knife to a thin film. The solvent is evaporated in a vacuum drying oven following the following method:
Subsequently the glass plate with the membrane is removed from the drying oven, and after cooling down it is immersed in a water bath. There the membrane comes off the glass plate. The membrane is posttreated in the following manner:
1) 48 h at 25° C. in 10% NaOH
2) 48 h at 90° C. in 7% HCl
3) 48 h at 60° C. in H2O
Then the membrane is characterized.
5.1.5 Membrane 504
At first 4,5 g sulfonated PEK (IEC=1,8 meq/g) are dissolved to a 15 wt % solution in NMP, then 3 ml npropylamine are added to the solution to neutralize the SO3H-groups. After that 0,3 g PSU-ortho-sulfone(C(OH)(4-diethylaminophenyl)2 as 15 wt % solution are added to the reaction mixture. then still 0,3 g Polybenzimidazole PBI Celazol® are added to the solution as a 8,755 wt % solution
After the homogenisation a thin film of the polymer solution is cast onto a glass plate with a doctor knife to a thin film. The solvent is evaporated in a vacuum drying oven following the following method:
Subsequently the glass plate with the membrane is removed from the drying oven, and after cooling down it is immersed in a water bath. There the membrane comes off the glass plate. The membrane is posttreated in the following manner:
1) 48 h at 25° C. in 10% NaOH
2) 48 h at 90° C. in 7% HCl
3) 48 h at 60° C. in H2O
Then the membrane is characterized.
5.2 Membrane Posttreatment with ZrOCl2—H3PO4
5.2.1 1. Cycle
The membranes are immersed two days at 60° C. in a 1M ZrOCl2-solution Subsequently the membranes are immersed 2 days at 60° C. in water, then 2 days at 60° C. in 10% H3PO4, and finally 2 days in water.
5.2.2 2. Cycle
The membranes are immersed 3 days at 60° C. in a 1M ZrOCl2-solution. Subsequently the membranes are immersed 2 days at 60° C. in water, then 2 days at 60° C. in 10% H3PO4, and finally 2 days in water.
5.2.3 3. Cycle
The membranes are immersed 3 days at 60° C. in a 1M ZrOCl2-solution. Subsequently the membranes are immersed 2 days at 60° C. in water, then 2 days at 60° C. in 10% H3PO4, and finally 2 days in water.
5.3 Membrane Characterization
In the following table are listed the characterization results of the membranes. “2d” means the characterization results after the first posttreatment-cycle with ZrOCl2—H3PO4, “5d” the characterization results after the second posttreatment cycle with ZrOCl2—H3PO4, and “8d” the characterization results after the third posttreatment cycle with ZrOCl2—H3PO4.
14Direct titration with 0.1 N NaOH
15Specific resistance, measured via Impedance spectroscopy in 0.5 N HCl
16Water uptake (Swelling) at 25° C., determined via SW = ((mnaβ − mtrocken)/mtrocken) * 100
17Back titration: at first addition of an excess of 0.1 N NaOH, then back-titration with 0.1 N HCl
In the following figures the swelling (water uptake) of the membranes 1202 (
One sees from the figures that the posttreatment with ZrOCl2—H3PO4 leads to a strong reduction of water uptake, and partially even to an increase in proton conductivity. This was not to be foreseen and is therefore surprising.
Number | Date | Country | Kind |
---|---|---|---|
102 09 774.7 | Feb 2002 | DE | national |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/DE03/00640 | Feb 2003 | US |
Child | 10929648 | Aug 2004 | US |