Novel phosphonized fluoroelastomers (pFKM), phosphonized perfluoroelastomers (pFFKM), their preparation methods, and their use in electrofilm applications.

Abstract

The present invention comprises a new class of high and low phosphonated aliphatic fluoropolymer rubbers (pFKM) and perfluoropolymer rubbers (pFFKM) based on FKM and FFKM, as well as methods for their preparation and their uses.

Description

Technical Field

[0001] Novel phosphonated fluoroelastomers (pFKM), phosphonated perfluoroelastomers (pFFKM), methods for their preparation and their use in electrical membrane applications.

Background Art

[0002] The most commonly described phosphonation systems are based on aryl polymers synthesized by nucleophilic substitution (via the Michaelis-Arbuzov and Michaelis-Becker rearrangements) of aryl halides with di- or trialkyl phosphites, such as those described in DE102011015212A1.

[0003] These phosphonated aryl polymers are characterized by their high thermal and chemical stability. In addition, they have good proton conductivity even in the dry state at temperatures above 100 °C. [1] The disadvantage of phosphonated aryl polymers, such as those from DE102011015212A1, is that they are mechanically unstable and brittle in the dry or non-humidified state. [1 - 5]

Summary of the Invention

[0004] Presentation of the Invention The steps of the present invention are based on the discovery of new phosphonated compounds which are proton conductive, chemically and mechanically stable even in the dry state and at high temperatures. These compounds must also be easy to synthesize. This is achieved by phosphonating non-conductive polymers such as FKM (fluororubber) or FFKM (perfluororubber) with trialkyl phosphites such as tris(trimethylsilyl) phosphite (TTMSP). The base rubbers FKM and FFKM already have high mechanical flexibility at both very low and very high temperatures and are chemically stable.

[0005] Surprisingly, after phosphononation, they retain their excellent mechanical and chemical properties even at temperatures above 100°C, are good proton conductors, and are soluble in organic solvents.

[0006] To date, no compounds possessing these positive properties have been synthesized, nor have any compounds been synthesized through this manufacturing method. Therefore, the polymer synthesized here represents a new class of material and the associated manufacturing process.

[0007] The reaction must be as effective and simple as possible, and the one described herein is such a case because it allows for the recovery of unused phosphononating agent. Phosphoned polymers should be soluble in common solvents so that films can be fabricated from them.

[0008] Phosphonation reactions can be carried out with all FKM and FFKM derivatives in the classification types 1 through 5 listed below. The monomer ratio of the FKM or FFKM is irrelevant; the only relevant condition is the presence of a monomer component with a reactive group -X in the FKM or FFKM. See illustrative Figure 1. It is a type 1 copolymer consisting of vinylidene fluoride (VDF) and hexafluoropropylene (HFP). It consists of Type 2 terpolymers VDF, HFP, and tetrafluoroethylene (TFE). It consists of Type 3 VDF, TFE, and perfluoroalkyl vinyl ether (PAVE). It consists of Type 4 TFE, VDF, and propylene. Type 5 perfluoroelastomers consisting of VDF, HFP, TFE, PAVE, and ethylene, as well as perfluoroelastomers consisting mainly of TFE and PAVE.

[0009] The present invention is based on the reaction of a reactive group -X of a side chain consisting of bisphenol AF already bonded to a fluororubber and perfluororubber or aliphatic polymer backbone with TTMSP. The reactive group -X (Figure 1) may be -I, -Br, -Cl, -H, or the free -OH of the bisphenol AF side chain, or a pseudohalogen (-CN, -N3, -OCN, -NCO, -CNO, -SCN, -NCS, -SeCN), depending on the substrate.

[0010] As a non-limiting example, the basic structure of a perfluoroelastomer (FFKM) is shown in Figure 1. In the formula, n, m, and z may be mixed in any ratio, and the constituent unit z determines the number of phosphonylated sites.

[0011] The only crucial element for the phosphononization reaction is the presence of a reactive group -X in FKM / FFKM that can react with TTMSP. Phosphoned polymers may still contain free reactive groups -X depending on the degree of phosphononization. These free groups can then be used to covalently crosslink the phosphononized polymer. Phosphonation to pFKM and pFFKM is carried out in solution. For this purpose, the base polymer can be dissolved in ethyl acetate, butanone, N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), etc. TTMSP can be optionally added before the dissolution process, directly during the dissolution process, or after the polymer has been dissolved. Depending on the desired degree of phosphononization, TTMSP is added based on the weight of the polymer, ranging from a low phosphononization of 0.1 wt.% to a high phosphononization of 5000 wt.%.

[0012] Depending on the FKM / FFKM used, the substrate is dissolved in the solvent either before or after phosphononization. The reaction proceeds best and most rapidly in aprotic solvents with high boiling points, such as NMP, DMAc, and DMSO. Gas generation can be observed during the reaction, indicating the start of the reaction. Trimethylsilyl-X (TMS-X) is formed as a byproduct.

[0013] The reaction is maintained at the reaction temperature (60°C to 200°C) until gas generation stops, depending on the FKM / FFKM and solvent used. The reaction is then maintained at the reaction temperature for a further 2 to 8 hours to ensure that the reaction is completed.

[0014] TMS-X and excess TTMSP are removed by distillation. Phosphoned polymers in the form of trimethylsilyl esters of pFKM or pFFKM remain in the solvent. The polymer solution is then added to water and, depending on the degree of phosphononization, precipitates as a solid (low degree of phosphononization) or becomes a solution (high degree of phosphononization). By boiling the water / polymer mixture, the phosphononized polymer is hydrolyzed from its trimethylsilyl ester form to high molecular weight phosphonic acid.

[0015] To completely separate hydrolysis by-products, the polymer can be washed in water depending on the degree of phosphononization. Non-water-soluble pFKM / pFFKM or a portion thereof can be separated by washing and filtration, while water-soluble components can be purified by dialysis.

[0016] Another method involves directly fabricating a polymer solution into a film, rather than precipitating the polymer solution in water, and then hydrolyzing this polymer film in hot water. The resulting polymers and films can be used in electrochemical cells. Preferably, the polymers or blended films can be used in low-temperature or medium-temperature fuel cells in the temperature range of -30°C to 250°C, or in low-temperature or medium-temperature electrolytic cells in the temperature range of 0°C to 250°C. In addition, the films can be used in chemical synthesis reactors at temperatures of -70°C to 250°C. The films can also be used as separators in primary and secondary batteries, or as binders in the electrodes of primary and secondary batteries.

Brief Description of the Drawings

[0017] [Figure 1] It is an example of the basic structure of FFKM having a reactive group -X. [Figure 2] Conductivity of phosphonated polymer (upper) and Nafion 212 (lower) for comparison, measured by decreasing from 50% RH at 30°C to 0.2% RH at 180°C. [Figure 3] Polarization curve of a membrane made from a phosphonated polymer having IECtotal = 2.62 mmol / g, indicating that phosphonation has occurred and its use in an electrochemical cell functions. <00D0083>An exemplary reaction scheme of the phosphonation reaction.

Modes for Carrying Out the Invention

[0018] Examples of non-limiting embodiments Mix 10 g of FKM with 90 g of N-methylpyrrolidone (NMP), stir, heat, and dissolve. Add 50 g of TTMSP to the solution and heat to 160°C. After a few minutes, gas begins to evolve, which is initially accelerating but then slows down and stops, indicating the end of the reaction. Keep the solution at the reaction temperature for an additional 2 - 12 hours to ensure the reaction is complete.

[0019] Here, by-products and excess TTMSP can be removed by distillation. The pFKM dissolved in NMP can here either be precipitated in water or a membrane can be prepared directly from the reaction solution. Both the precipitated and directly cast variants still need to be post-treated in hot water to boiling water or with hot steam to obtain the -phosphonic acid form (Figure 4).

[0020] Analysis of the experiment Here, as an example, we describe one of the phosphonized polymers with different degrees of phosphonization, including its ion exchange capacity, conductivity up to 180°C, and electrolytic tests as a proof of concept.

[0021] Determination of ion exchange capacity Cover 100 mg of the prepared polymer with saturated NaCl solution and stir for approximately 2 hours, then add 2 drops of bromothymol blue as an indicator. The protons of phosphonated pFKM are exchanged with Na ions, forming HCl. The formed HCl is detected by titration with 0.1 mol of NaOH. From this, IEC direct This can be determined. To determine the total IEC, 3 ml of 0.1 M NaOH is added in excess to the same solution, stirred again for another 2 hours, and then back-titrated with HCl.

[0022] In the above experiment, IEC direct = 0.99 mmol / g and IEC total = 2.62 mmol / g is obtained. If the same experiment is performed with 10g of FKM and 10g of TTMSP, then IEC direct = 0.56 mmol / g and IEC total = 0.8 mmol / g is obtained. This clearly demonstrates the relationship between the reactant ratio, degree of phosphononization, and conductivity (Figure 2).

[0023] Conductivity Figure 2 clearly shows the effect of phosphononization on conductivity, and also clearly demonstrates that conductivity does not decrease even above 100°C. Therefore, a new type of electrochemical cell capable of operating above 150°C is possible. For comparison with current technology, the Nafion 212 is also shown under the same measurement conditions.

[0024] IEC total Proof-of-concept electrolysis with a membrane containing 2.6 mmol / g IEC totalA film was prepared from a phosphonized polymer with a concentration of 2.6 mmol / g, and this film was measured using an electrolytic cell. This demonstrated its potential for use in electrofilm processes (Figure 3).

[0025] literature [1] Vladimir Atanasov and Jochen Kerres Highly Phosphonated Polypentafluorostyrene; Macromolecules 2011, Volume 44, Issue 16, Pages 6416-6423 [2] Vladimir Atanasov, Dietrich Gudat, Bastian Ruffmann, Jochen Kerres Highly phosphonated polypentafluorostyrene: Characterization and blends with polybenzimidazole, European Polymer Journal, Volume 49, Issue 12, 2013, Pages 3977-3985. [3] VIadimir Atanasov, Matthias Burger, Sandrine Lyonnard, Lionel Porcar, Jochen Kerres Sulfonated poly(pentafluorostyrene): Synthesis & characterization, Solid State Ionics, Volume 252, 2013, Pages 75-83. [4] Vladimir Atanasov, Jochen Kerres ETFE-g-pentafluorostyrene: Functionalization and proton conductivity, European Polymer Journal, Volume 63, 2015, Pages 168-176. [5] Vladimir Atanasov, Andrey Oleynikov, Jiabing Xia, Sandrine Lyonnard, Jochen Kerres Phosphonic acid functionalized poly(pentafluorostyrene) as polyelectrolyte membrane for fuel cell application; Journal of Power Sources, Volume 343, 2017, Pages 364-372. Specific embodiments of the present invention are as follows. [Aspect 1] Phosphono-aliphatic fluoropolymer rubber (pFKM) and phosphono-aliphatic perfluoropolymer rubber (pFFKM) synthesized from fluoropolymer rubber (FKM) and perfluoropolymer rubber (FFKM), characterized in that a phosphonic acid group is directly present on the main chain and / or side chain of the polymer, and the side chain is aliphatic and aryl in each case. [Aspect 2] A phosphonized partially fluorinated, fluorinated, and perfluorinated aliphatic rubber of types 1 to 5 (as described in "Presentation of the Invention") as described in Embodiment 1, characterized in that it has a degree of phosphonization such that it can have a maximum of one phosphonic acid group per repeating unit, and a film can be produced from this aliphatic rubber. [Aspect 3] The phosphononized polymer according to embodiment 1 or 2, characterized in that there exists an unreacted reactive group -X (phosphononization degree less than 1) which can be covalently crosslinked thereafter and from which a covalently bonded film can be produced, and -X is at least one member selected from the group consisting of -I, -Br, -Cl, -HCN, -N3, -OCN, -NCO, -CNO, -SCN, -NCS, -SeCN, or the free -OH of the bisphenol AF side chain. [Aspect 4] The phosphonized polymer membrane according to embodiments 1 to 3, characterized in that the obtained phosphonized polymer can be blended with a basic polymer such as polybenzimidazole or an anion exchange polymer to form an acid-base blend membrane, a covalently crosslinked membrane, and a covalently crosslinked acid-base blend membrane. [Aspect 5] The phosphonized polymer film according to embodiment 4, characterized in that the mixing ratio between the phosphonized polymer and the basic polymer is between 99 mol% phosphonized polymer and 1 mol% basic polymer and 1 mol% phosphonized polymer and 99 mol% basic polymer. [Aspect 6] A phosphonized polymer membrane according to any one of embodiments 1 to 5, characterized in that any sulfonated polymer can be added to the blend in any amount. [Aspect 7] The phosphonized polymer film according to any one of embodiments 4 to 6, characterized in that the blend film can be further doped with any amount of phosphoric acid. [Aspect 8] The phosphononized polymer film according to embodiment 7, characterized in that the phosphate doping level is preferably 40 wt.% to 500 wt.%. [Aspect 9] A method for preparing pFKM or pFFKM, which are phosphonized polymers and films, comprising: dissolving or suspending the FKM or FFKM in a phosphonizing agent; heating to a temperature between 40°C and 200°C for 30 minutes to 12 hours; then removing excess phosphonizing agent by distillation or other means; and isolating the polymer by dialysis or precipitation, wherein the FKM or FFKM has at least one reactive group -X, and -X is at least one member selected from the group consisting of -I, -Br, -Cl, -H, -CN, -N3, -OCN, -NCO, -CNO, -SCN, -NCS, -SeCN, or the free -OH of the bisphenol AF side chain. [Aspect 10] The method according to embodiment 9, characterized in that the FKM or FFKM is dissolved or suspended in the phosphonolating agent with the addition of at least one further solvent. [Aspect 11] The method according to embodiment 10, characterized in that the solvent is at least one member selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), or dimethyl sulfoxide (DMSO). [Aspect 12] The method according to any one of embodiments 9 to 11, characterized in that the phosphonosing agent is tris(trimethylsilyl)phosphite. [Aspect 13] Use of polymers and membranes according to embodiments 1 to 8 in an electrochemical cell. [Aspect 14] Use of the membrane or blended membrane according to Embodiment 13 in a low-temperature or medium-temperature polymer electrolyte membrane (PEM) fuel cell in the temperature range of -30°C to 250°C. [Aspect 15] Use of the film according to embodiment 13 in a low-temperature or medium-temperature PEM electrolytic cell in the temperature range of 0°C to 250°C. [Aspect 16] Use of the membrane described in embodiment 13 in a chemical synthesis reactor operating at -70°C to 250°C. [Aspect 17] Use of the film described in embodiment 13 as a separator in primary and secondary batteries. [Aspect 18] Use of the polymers according to embodiments 1 to 4 as binders in electrodes of primary and secondary batteries.

Claims

1. It is a phosphonized polymer: Aliphatic polymer skeletons; and phosphonic acid group Includes, The phosphonized polymer is selected from the group consisting of phosphonized aliphatic fluoropolymer rubber (pFKM) synthesized from fluoropolymer rubber (FKM) and phosphonized aliphatic perfluoropolymer rubber (pFFKM) synthesized from perfluoropolymer rubber (FFKM). The phosphonic acid group is present directly on the main chain of the phosphonized polymer or directly on both the main chain and the side chains. There are unreacted reactive groups -X (phosphonization degree less than 1) which can be covalently crosslinked thereafter, and from which a covalently bonded film can be produced, and -X is -I, -Br, -Cl, -CN, -N ３ The phosphononized polymer is characterized by being at least one member selected from the group consisting of -OCN, -NCO, -CNO, -SCN, -NCS, -SeCN, and the free -OH of the bisphenol AF side chain.

2. The phosphononized polymer according to claim 1, wherein the phosphononized polymer is selected from the group consisting of a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a terpolymer consisting of VDF, HFP, and tetrafluoroethylene (TFE), a terpolymer consisting of VDF, TFE, and perfluoroalkyl vinyl ether (PAVE), a terpolymer consisting of TFE, VDF, and propylene, a polymer consisting of VDF, HFP, TFE, PAVE, and ethylene, and a perfluoroelastomer consisting of TFE and PAVE.

3. A film comprising the phosphonized polymer described in claim 1, The film is an acid-base blend film which is a blend of the phosphonized polymer and the basic polymer, a covalently crosslinked film, or a covalently crosslinked acid-base blend film which is a blend of the phosphonized polymer and the basic polymer.

4. The membrane according to claim 3, characterized in that the mixing ratio between the phosphonized polymer and the basic polymer in the acid-base blend membrane is between 99 mol% phosphonized polymer and 1 mol% basic polymer and 1 mol% phosphonized polymer and 99 mol% basic polymer.

5. The membrane according to claim 3, characterized in that any sulfonated polymer can be added to the blend in any amount.

6. The membrane according to any one of claims 3 to 5, characterized in that the acid-base blend membrane can be further doped with any amount of phosphoric acid.

7. The membrane according to claim 6, characterized in that the phosphate doping level is between 40 wt.% and 500 wt.%.

8. A method for preparing a phosphonized polymer, Fluoropolymer rubber (FKM) or perfluoropolymer rubber (FFKM) is dissolved or suspended in a phosphonizing agent, heated to a temperature between 40°C and 200°C for 30 minutes to 12 hours, then excess phosphonizing agent is removed by distillation or other means, and the phosphonized polymer is isolated by dialysis or precipitation. Here, the phosphonized polymer is a phosphonized aliphatic fluoropolymer rubber (pFKM) or a phosphonized aliphatic perfluoropolymer rubber (pFFKM), and the FKM or FFKM has at least one reactive group -X, where -X is -I, -Br, -Cl, -CN, -N ３ It is at least one member selected from the group consisting of -OCN, -NCO, -CNO, -SCN, -NCS, -SeCN, and the free -OH group of the bisphenol AF side chain, and A method characterized in that the phosphonolating agent is tris(trimethylsilyl) phosphite.

9. The method according to claim 8, characterized in that the FKM or FFKM is dissolved or suspended in the phosphonon agent with the addition of at least one further solvent.

10. The method according to claim 9, characterized in that the solvent is at least one member selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

11. Use of the membrane according to claim 3 in an electrochemical cell.

12. Use of the membrane according to claim 11 in a low-temperature or medium-temperature polymer electrolyte membrane (PEM) fuel cell in the temperature range of -30°C to 250°C.

13. Use of the film according to claim 12 in a low-temperature or medium-temperature PEM electrolytic cell in the temperature range of 0°C to 250°C.

14. Use of the membrane according to claim 11 in a chemical synthesis reactor operating at -70°C to 250°C.

15. Use of the film according to claim 11 as a separator in primary and secondary batteries.

16. Use of the phosphonized polymer according to claim 1 as a binder in the electrodes of primary and secondary batteries.

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