DE10054233A1 - Covalently cross-linked composite membranes - Google Patents

Abstract

The invention relates to covalently crosslinked composites and covalently crosslinked composite polymer membranes, consisting of one or more polymers and framework and / or layered silicates. The framework and / or layered silicates can be both functionalized and non-functionalized. DOLLAR A The polymers are characterized in that they can carry the following functional groups (M = Hal, (F, Cl, Br, I), OR, NR¶2¶; R = alkyl, hydroxyalkyl, aryl; (Me = H , Li, Na, K, Cs or other metal cations or ammonium ions): a) Precursors of cation exchange groups: SO¶2¶Me and / or POMe¶2¶ and / or COMe b) Sulfinate groups SO¶2¶Me and those using the following organic Compounds can be covalently cross-linked: DOLLAR A a) di-, tri- or oligofunctional haloalkanes or halogen aromatics which have been reacted with sulfinate groups SO¶2¶Me, whereby the following cross-linking bridges are present in the polymer / in the polymer blend / in the polymer membrane ( Y = cross-linking bridge, X = Hal (F, Cl, Br, I) OR, Y = - (CH¶2¶) ¶x¶-; -arylene-; - (CH¶2¶) ¶x¶-arylene-; CH¶2¶-arylene-CH¶2¶-, x = 3-12): polymer-SO¶2¶-Y-SO¶2¶-polymer and / or b) compounds containing the following groups: Hal- ( CH¶2¶) ¶x¶-NHR, which on one side (Hal-) m it had been reacted with sulfinate groups SO¶2¶Me, and on the other side (-NHR) with SO¶2¶Me groups, whereby the following cross-linking bridges are present in the polymer / in the polymer blend / in the polymer membrane: ...

Description

STATE OF THE ART

The invention on which the present additional application is based relates to a Further training or alternative to the German patent application DE 100 24 575.7 (Covalently cross-linked polymers and polymer membranes via sulfinate alkylation).

The content of this earlier German application DE 100 24 575.7 is hereby incorporated by reference expressly referred to.

However, the products and processes according to this aforementioned master application have the following disadvantages:
Membranes that are manufactured according to the described method still require humidified gases for operation in the hydrogen fuel cell. If the gases are not moistened, the membrane dries out and the proton conductivity decreases very sharply.

To solve this problem, the present application proposes functionalized especially in a covalent network after the parent registration and add non-functionalized framework and layered silicates.

The parent application only describes that polymers into the covalent Network. When using functionalized layer and / or framework silicates was surprisingly found that the layers and / or structural silicate-bound low molecular weight functional groups Connections, during the use of the membrane, especially in the application the hydrogen fuel cell, not or only moderately discharged. This enables an increase in the concentration of ion conducting groups within the covalent network, without the mechanical Properties of the membrane deteriorate very strongly (embrittlement or strong Swelling). In extreme cases, it is even possible to use included ion-conducting polymers in the covalent network completely dispense. The ion conduction then takes place exclusively via the functional ones Groups carrying silicates instead.

With the present invention, the problem of dehydration of the Membranes and the limited number of ion conducting groups within the Membrane defused to a not inconsiderable degree.  

It is therefore an object of the invention to develop new covalently crosslinked polymers / membranes To provide, even in operation with gases that are not or only slightly humidified Have proton conductivity. It is also another task low molecular weight functionalized compounds so into the covalent network, coupled to a silicate, insert that they have a technically applicable Period remain in the membrane.

Furthermore, the method according to the invention contributes to solving this problem.

invention description

The following text expressly refers to the parent application DE 100 24 575.7:
A mixture is prepared in a suitable solvent, preferably an aprotic one, which contains polymers and functionalized framework and / or layered silicates and optionally low-molecular compounds.

The mixture contains polymers and the following functional groups:

• - Sulfinate groups SO ₂ Me (Me = a or multivalent metal cation).
• - Sulfochloride groups and / or other precursors of cation exchange

In addition, the mixture, preferably polymer solution, is a bi- or oligo-functional alkylation crosslinking agent (typically an α, ω-dihaloalkane) and optionally a sec. Diamine crosslinker NHR- (CH ₂ ) _x -NHR added. The covalent crosslinking bridges are formed during the membrane formation during evaporation of the solvent by alkylation of the sulfinate groups and optionally sulfonamide formation via reaction of the sulfohalide groups present in the polymer with the sec. Amine groups of the diamine crosslinker. During the acidic and / or basic and / or neutral aqueous aftertreatment of the membranes following the membrane formation, the precursors of the ion exchanger groups are hydrolyzed or oxidized to ion exchanger groups.

In Fig. 1, the formation of the covalent cross-linking bridges in blends of sulfochlorinated polymer and sulfinated polymer is shown schematically, in Fig. 2, the formation of the covalent cross-linking bridges in a polymer that contains both sulfinate and sulfochloride groups.

The composites according to the invention consist of polymers, with the following functional groups:

After membrane production, before hydrolysis:

• - SO ₂ M and / or POM ₂ and / or COM (M = Hal (F, Cl, Br, I), OR, NR ₂ ; R = alkyl, hydroxyalkyl, aryl)
• - Network bridges:
  • a) Polymer-SO ₂ -Y-SO ₂ polymer
    possibly:
  • b) Polymer-SO ₂ -Y'-NR-SO ₂ polymer
  • c) Polymer-SO ₂ -NR-Y "-NR-SO ₂ polymer

After hydrolysis:

• - -SO ₃ M-, -PO ₃ M ₂ -, -COOM groups
• - o. G. crosslinks

Through the covalent crosslinking of the sulfinate polymers in a mixture with precursors of Ion exchange polymers, especially cation exchange polymers, in The presence of functionalized layered and / or framework silicates becomes one better mixing of the blend phases and thus also a higher degree of crosslinking achieved what resulted in better mechanical stability of the result Polymer film expresses, compared to covalently cross-linked polymer (blend) films Cation exchange polymers and polymeric sulfinates. Through the targeted Inclusion of an amino group-containing crosslinking component, which with the Precursors of the cation exchange groups react, one in the polymer network achieved further improvement in mechanical properties.

By installing functionalized framework and / or layered silicates in the covalent network during membrane formation will increase the water holding capacity of the Membrane increased. The functional groups that emerge from the surface of the protruding functionalized framework or layered silicates also change the Properties of the membrane according to its functionality.

Description of the inorganic filler

If the inorganic active filler is a layered silicate, it is based on Montmorillonite, smectite, illite, sepiolite, palygorskite, muscovite, allevardite, amesite, Hectorite, talc, fluorhectorite, saponite, beidelite, nontronite, stevensite, bentonite, Mica, vermiculite, fluor vermiculite, halloysite, fluorine-containing synthetic Talc types or mixtures of two or more of the sheet silicates mentioned. The  Layered silicate can be delaminated or pillarted. Is particularly preferred Montmorillonite.

The weight fraction of the layered silicate can generally be from 1 to 80 percent, especially from 2 to 30% by weight and especially from 5 to 20% by weight.

Is the functionalized filler, especially zeolites and representatives of the Beidelith series and bentonite, the only ion-conducting component, is its weight percentage generally between 5 and 80%, especially between 20 and 70% and especially in Ranges from 30 to 60% by weight.

Description of the functionalized layered silicate

Layered silicate is generally understood to mean silicates in which the SiO ₄ tetrahedra are connected in two-dimensional infinite networks. (The empirical formula for the anion is (Si ₂ O ₅ ^2- ) _n ). The individual layers are connected to one another by the cations lying between them, with Na, K, Mg, Al and / or Ca mostly being present as cations in the naturally occurring layered silicates.

Layered silicates are said to be under a delaminated functionalized layered silicate be understood, in which by implementation with so-called Functionalization means the layer distances are initially increased. The layer thicknesses of such silicates before delamination are usually from 5 to 100 angstroms, preferably 5 to 50 and in particular 8 to 20 angstroms. The layer silicates are used to increase the layer spacing (hydrophobization) (before the production of the composites according to the invention) with so-called Functionalizing water repellents implemented, which often as Onium ions or onium salts are referred to.

The cations of the layered silicates are functionalized by organic ones Hydrophobing agent replaced, the by the nature of the organic residue desired layer spacing can be set, which depends on the type of respective functionalizing molecule or polymer, which in the Layered silicate should be installed.

The exchange of the metal ions or the protons can be complete or partial respectively. A complete exchange of the metal ions or protons is preferred. The amount of exchangeable metal ions or protons is usually in  Milliequivalents (meq) per 1 g of framework or layered silicate stated and as Designated ion exchange capacity.

Layered or framework silicates with a cation exchange capacity are preferred of at least 0.5, preferably 0.8 to 1.3 meq / g.

Suitable organic functionalizing water repellents are derived from Oxonium, ammonium, phosphonium and sulfonium ions from which one or can carry several organic residues.

Suitable functionalizing hydrophobizing agents are those of the general formula I and / or II:

The substituents have the following meaning:
R1, R2, R3, R4 independently of one another are hydrogen, a straight-chain branched, saturated or unsaturated hydrocarbon radical having 1 to 40, preferably 1 to 20, carbon atoms, which optionally carries at least one functional group or 2 of the radicals are bonded to one another, in particular to form one heterocyclic radical with 5 to 10 C atoms, particularly preferably with one and more N atoms,
X for phosphorus or nitrogen,
Y for oxygen or sulfur,
n for an integer from 1 to 5, preferably 1 to 3 and
Z stands for an anion.

Suitable functional groups are hydroxyl, nitro or sulfo groups, where Carboxyl and sulfonic acid groups are particularly preferred. Are also special preferably sulfochloride and carboxylic acid chlorides.  

Suitable anions Z are derived from proton-providing acids, in particular Mineral acids, whereby halogens such as chlorine, bromine, flour, iodine, sulfate, sulfonate, Phosphate, phosphonate, phosphite and carboxylate, especially acetate, are preferred. The layered silicates used as starting materials are usually in the form of a Suspension implemented. The preferred suspending agent is water, optionally in a mixture with alcohols, especially lower alcohols with 1 to 3 carbon atoms. Is not the functionalizing water repellent water-soluble, the solvent is preferred by dissolving. Is special this is an aprotic solvent. Other examples of suspending agents are Ketones and hydrocarbons. Usually one becomes miscible with water Suspending agent preferred. When adding the water repellent to Layered silicate ion exchange occurs, whereby the layered silicate usually fails from the solution. The resulting as a by-product of ion exchange Metal salt is preferably water-soluble, so that the hydrophobized layered silicate as crystalline solid by e.g. B. filtering can be separated.

The ion exchange is largely independent of the reaction temperature. The Temperature is preferably above and below the crystallization point of the medium its boiling point. In aqueous systems the temperature is between 0 and 100 ° C, preferably between 40 and 80 ° C.

Alkylammonium ions are preferred for cation and anion exchange polymer, especially when a carboxylic acid chloride is added as a functional group or sulfonic acid chloride is present on the same molecule. The Alkyl ammonium ions are available via common methylation reagents, such as methyl iodide available. Suitable ammonium ions are omega-aminocarboxylic acids, in particular preferred are omega-aminoarylsulfonic acids and the omega- Alkylaminosulfonsäuren. The omega-aminoarylsulfonic acids and the omega Alkylaminosulfonic acids are available with conventional mineral acids, for example Hydrochloric acid, sulfuric acid or phosphoric acid or from methylating reagents such as Methyl iodide.

Other preferred ammonium ions are pyridine and laurylammonium ions. After the hydrophobization, the layered silicates generally have one Layer spacing from 10 to 50 angstroms, preferably from 13 to 40 angstroms. The hydrophobized and functionalized layered silicate is penetrated by water Free drying. In general, the layered silicate treated in this way contains one more  Residual water content of 0-5% by weight of water. Then the hydrophobized Layered silicate as a suspension in a suspension medium that is as anhydrous as possible the polymers mentioned are mixed and processed into a membrane become.

A particularly preferred functionalization of the framework and / or layered silicates is generally carried out with modified dyes or their precursors, especially with triphenylmethane dyes. They have the general formula:

R = alkyl (especially CH ₃ ; C ₂ H ₅ ).

In the present invention, dyes are used which are derived from the following basic structure:
The dye or its reduced amount is used to functionalize the layered silicate

Precursor in an aprotic solvent (e.g. tetrahydrofuran, DMAc, NMP) sufficiently stirred together with the silicate in a vessel. After about 24 hours the dye or the precursor is intercalated into the cavities of the layered silicate. The intercalation must be such that the ion conducting group on the Surface of the silicate particle.

The following figure shows the process schematically

The layered silicate thus functionalized is added to the polymer solution as in Application DE 100 24 575.7 was added. It turned out to be special Proven to use the precursor of the dyes. Only in the acidic The actual dyes are aftertreated by splitting off water educated.

In the case of triphenylmethane dyes, it was surprisingly found that a proton line that supports the membranes made from it. Whether it Even an anhydrous proton line is not sufficient Security can be said. If the dyes are not bound to the silicate, they lie So in free form in the membrane, they become with after a short time discharged the water of reaction in the fuel cell.

According to the invention, the polymer mixtures containing sulfinate groups are made from the parent application mentioned above, particularly preferably the thermoplastic functionalized polymers (ionomers) to the suspension of the hydrophobized  Given layered silicates. This can be done in already solved form or the Polymers are brought into solution in the suspension itself. General is the Share of layered silicates between 1 and 70% by weight. Especially between 2 and 40% by weight and especially between 5 and 15% by weight.

A further improvement compared to the parent application is the additional mixing of zirconyl chloride (ZrOCl ₂ ) into the membrane polymer solution and into the cavities of the layer and / or framework silicates. If the aftertreatment of the membrane is carried out in phosphoric acid, sparingly soluble zirconium phosphate precipitates in the immediate vicinity of the silicate grain. Zirconium phosphate shows its own proton conductivity during operation of the fuel cell. Proton conductivity functions as intermediate steps via the formation of the hydrogen phosphates and is state of the art. The targeted introduction in the immediate vicinity of a water reservoir (silicates) is new.

1. Embodiment for membrane production

Sulfochlorinated PSU Udel® (IEC = 1.8 meq SO ₂ Cl / g) and PSUSO ₂ Li (IEC = 1.95 meq SO ₂ Li / g) (polymer structures see Fig. 2) and montmorillonite functionalized with triphenylmethane dye are Methylpyrrolidinone (NMP) dissolved. Then the crosslinking agent α, ω-diiodobutane is added to the solution. Stir for 15 minutes. The solution is then filtered and degassed. A thin film of the polymer solution is scraped out on a glass plate. The glass plate is placed in a vacuum drying cabinet and the solvent is drawn off at temperatures of 80-130 ° C. at a negative pressure of 700 to finally 15 mbar. The film is removed from the drying cabinet and cooled. The polymer film is detached from the glass plate under water and first hydrolyzed / aftertreated in 10% hydrochloric acid and then in deionized water at temperatures from 60 to 90 ° C. for 24 hours.

2nd embodiment

Sulfochlorinated PSU Udel® (IEC = 1.2 meq SO ₂ Cl / g) and PSUSO ₂ Li (IEC = 1.95 meq SO ₂ Li / g) and montmorillonite treated with α, ω-aminoalkylsulfochloride (with outwardly pointing sulfochloride Group) are dissolved in N-methylpyrrolidinone (NMP). Then the crosslinking agent α, ω-diiodobutane is added to the solution. Stir for 15 minutes. The solution is then filtered and degassed and processed into a membrane as in Example 1.

After treatment, this membrane has a higher IEC than the control without the functionalized layered silicate.

3rd embodiment

Sulfochlorinated PSU Udel® (IEC = 1.8 meq SO ₂ Cl / g) and PSUSO ₂ Li (IEC = 1.95 meq SO ₂ Li / g) (polymer structures see Fig. 2) and montmorillonite treated with zirconyl chloride are dissolved in dimethyl sulfoxide ( DMSO) resolved.

The dissolution takes place in the following order: First, montmorillonite K10 suspended in DMSO and with 10% wt. Zirconyl chloride based on the Total membrane amount offset. After that, the other polymer components hintzugegeben. Then the crosslinking agent α, ω-diiodobutane is added to the solution. you stir for 15 minutes. The solution is then filtered and degassed. A thin film of the Polymer solution is doctored on a glass plate. The glass plate is in one Vacuum drying cabinet, and at temperatures of 80-130 ° C it will Solvent removed at a negative pressure of 700 to finally 15 mbar. The Film is removed from the drying cabinet and cooled. The polymer film will detached from the glass plate under phosphoric acid and in phosphoric acid for about 10 hours stored at a temperature between 30 and 90 ° C and then if necessary in 10% hydrochloric acid and then in deionized water at temperatures from 60 to 90 ° C hydrolyzed / aftertreated for 24 hours each.  

4th embodiment

The procedure is as in Example 1, with the difference that the unmodified Montmorillonite K10 is used.

Claims (14)

1. Covalently cross-linked composite or covalently cross-linked composite polymer membrane, consisting of one or more polymers and framework and / or layered silicates.
The framework and / or layered silicates can be both functionalized and non-functionalized.
The polymers are characterized in that they can carry the following functional groups (M = Hal (F, Cl, Br, I), OR, NR ₂ ; R = alkyl, hydroxyalkyl, aryl; (Me = H, Li, Na, K, Cs or other metal cations or ammonium ions):

• a) Precursors of cation exchange groups: SO ₂ M and / or POM ₂ and / or COM
• b) sulfinate groups SO ₂ Me

and which can be covalently crosslinked using the following organic compounds:

• a) di- or oligofunctional haloalkanes or haloaromatics which have been reacted with sulfinate groups SO ₂ Me, whereby the following crosslinking bridges are present in the polymer / in the polymer blend / in the polymer membrane (Y = crosslinking bridge, X = Hal (F, Cl , Br, I), OR, Y = - (CH ₂ ) _x -; -arylene-; - (CH ₂ ) _x arylene-; CH ₂ -arylene-CH ₂ -, x = 3-12): polymer-SO ₂ -Y-SO ₂ polymer and / or
• b) Compounds containing the following groups: Hal- (CH ₂ ) _X -NHR, which had been reacted on one side (Hal-) with sulfinate groups SO ₂ Me and on the other side (-NHR) with SO ₂ M groups, whereby the following cross-linking bridges are present in the polymer / in the polymer blend / in the polymer membrane: Polymer-SO ₂ - (CH ₂ ) _x -NR- SO ₂ polymer
  and or
• c) Compounds which contain the following groups: NHR- (CH ₂ ) _x -NHR which had been reacted with SO ₂ Me groups, as a result of which the following crosslinking bridges are present in the polymer / in the polymer blend / in the polymer membrane: polymer SO ₂ -NR- (CH ₂ ) _x - NR-SO ₂ polymer

2. Covalently cross-linked polymer blend or polymer blend membrane according to claim 1, characterized in that it is composed of the following polymers:

• a) a polymer with at least SO ₂ M groups
• b) a polymer with at least SO ₂ Me groups

3. Covalently cross-linked polymer blend or polymer blend membrane according to claims 1 to 2, characterized in that it consists of a polymer which contains the following groups: SO ₂ M groups and SO ₂ Me groups. 4. Covalently cross-linked polymer blend or polymer blend membrane according to the claims 1 to 3, characterized in that the base polymer carrying the functional groups or the base polymers carrying the functional groups are selected from the Group of polyether sulfones, polysulfones, polyphenyl sulfones, polyether ether sulfones, Polyether ketones, polyether ether ketones, polyphenylene ethers, polydiphenylphenylene ethers, Polyphenylene sulfides or copolymers are at least one of these components contain. 5. Covalently and ionically crosslinked polymer blend or polymer blend membrane according to the Claims 1 to 4, characterized in that the following polymers as base polymers preferred are: polysulfones, polyphenylene ethers or other lithiable polymers. 6. Covalently crosslinked polymer blend or polymer blend membrane according to claims 1 to 5, characterized in that preferred crosslinkers are: Hal (CH ₂ ) _x -Hal or Hal-CH ₂ -phenylene-CH ₂ -Hal (x = 3-12 , Hal = F, Cl, Br, I). 7. Covalently cross-linked polymer blend or polymer blend membrane according to claims 1 to 6, characterized in that the SO ₂ M and / or POM ₂ - and / or COM groups of the polymer / the polymer (blend) membrane by the following aftertreatment (s) to the respective cation exchanger groups SO3Me and / or PO3Me2 and / or COOMe (Me = H, Li, Na, K, Cs or other metal cations or ammonium ions) are hydrolyzed:

• a) in 1 to 50 wt .-% aqueous alkali at T = RT-95 ° C.
• b) in deionized water at T = RT-95 ° C
• c) in 1 to 50 wt .-% aqueous mineral acid at T = RT-95 ° C.
• d) in deionized water at T = RT-95 ° C

If necessary, one or more of the post-treatment steps can be omitted. 8. A process for the preparation of covalently crosslinked polymers, polymer blends or polymer (blend) membranes according to claims 1-7, characterized in that the polymers simultaneously or successively in a dipolar aprotic solvent which is selected from N, N-dimethylformamide ( DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidinone (NMP), dimethyl sulfoxide (DMSO) or sulfolane, are dissolved, then the crosslinker is added, then the crosslinker is homogeneously distributed in the polymer solution by stirring, then the polymer solution is filtered, then the polymer solution is degassed, then the polymer solution is spread as a thin film on a support (glass plate, metal plate, fabric, fleece, etc.), then the solvent by heating to 80 to 130 ° C and / or by applying negative pressure or is removed in a circulating air dryer, after which the polymer film, if appropriate, is detached from the base, after which the polymer film subsequently follows delt is:

• a) in 1 to 50% by weight aqueous alkali at T = RT to 95 ° C.
• b) in deionized water at T = RT to 95 ° C
• c) in 1 to 50 wt .-% aqueous mineral acid at T = RT to 95 ° C.
• d) in deionized water at T = RT to 95 ° C

If necessary, one or more of the post-treatment steps can be omitted. 9. Use of the membranes according to claims 1-8 for the production of energy electro-chemical way. 10. Use of the membranes according to claims 1-8 as a component of membrane fuel cells (H ₂ - or direct methanol fuel cells) at temperatures from 0 to 180 ° C. 11. Use of the membranes according to claims 1-8 in electrochemical cells. 12. Use of the membranes according to claims 1-8 in secondary batteries 13. Use of the membranes according to claims 1-8 in electrolytic cells. 14. Use of the membranes according to claims 1-8 in membrane separation processes such as gas separation, pervaporation, perstraction, reverse osmosis, electrodialysis, and Diffusion dialysis.