Membranes

Abstract

An anion exchange membrane obtainable by curing a curable composition comprising: (a) a monomer (a) of Formula (I) AR.sup.1(CH.sub.2).sub.nN.sup.+(R.sup.aR.sup.b)(CH.sub.2).sub.n-AR.sup.2, X.sup. wherein: each n independently has a value of 1 or 2; (i) R.sup.a and R.sup.b are each independently an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group; or (ii) R.sup.a and R.sup.b, together with the positively charged nitrogen atom to which they are attached, form an optionally substituted 5- or 6-membered ring; or (iii) one of R.sup.a and R.sup.b is an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group and the other of R.sup.a and R.sup.b, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring; or (iv) R.sup.a, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring, and R.sup.b, together with the group of formula N.sup.+(CH.sub.2).sub.n-AR.sup.2, forms an optionally substituted 5- or 6-membered ring; X is an anion; and AR.sup.1 and AR.sup.2 each independently comprise aromatic groups; wherein: (I) at least one of AR.sup.1 and AR.sup.2 comprises a curable ethylenically unsaturated group; (II) the monomer (a) of Formula (I) comprises at least two curable ethylenically unsaturated groups; and (III) the molar fraction of component (a) in relation to all curable components of the curable composition is at least 0.90.

Claims

1. An anion exchange membrane obtainable by curing a curable composition comprising: (a) a monomer (a) of Formula (I) ##STR00009## wherein: each n independently has a value of 1 or 2; (i) R.sup.a and R.sup.b are each independently an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group; or (ii) R.sup.a and R.sup.b, together with the positively charged nitrogen atom to which they are attached, form an optionally substituted 5- or 6-membered ring; or (iii) one of R.sup.a and R.sup.b is an optionally substituted C.sub.1-3-alkyl group or an optionally substituted C.sub.2-3-alkenyl group and the other of R.sup.a and R.sup.b, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring; or (iv) R.sup.a, together with the group of formula AR.sup.1(CH.sub.2).sub.nN.sup.+, forms an optionally substituted 5- or 6-membered ring, and R.sup.b, together with the group of formula N.sup.+(CH.sub.2).sub.n-AR.sup.2, forms an optionally substituted 5- or 6-membered ring; X.sup. is an anion; and AR.sup.1 and AR.sup.2 each independently comprise aromatic groups; wherein: (I) at least one of AR.sup.1 and AR.sup.2 comprises a curable ethylenically unsaturated group; (II) the monomer (a) of Formula (I) comprises at least two curable ethylenically unsaturated groups; and (III) the molar fraction of component (a) in relation to all curable components of the curable composition is at least 0.90.

2. The anion exchange membrane according to claim 1 wherein in Formula (I) n has a value of 1.

3. The anion exchange membrane according to claim 1 wherein AR.sup.1 and AR.sup.2 each comprise a curable ethylenically unsaturated group.

4. The anion exchange membrane according to claim 1 wherein in Formula (I) both AR.sup.1 and AR.sup.2 comprise a styrenyl group.

5. The anion exchange membrane according to claim 1 wherein the curable composition further comprises a monomer (b) a cationically charged group and one and only one curable ethylenically unsaturated group.

6. The anion exchange membrane according to claim 1 wherein the curable ethylenically unsaturated groups are vinyl groups.

7. The anion exchange membrane according to claim 1 which has an ion exchange capacity lower than 1.65 meq/g of dry membrane.

8. The anion exchange membrane according to claim 1 wherein the curable composition further comprises (c) a radical initiator.

9. The anion exchange membrane according to claim 1 wherein the curable composition further comprises (d) a monomer free from cationically charged groups.

10. The anion exchange membrane according to claim 1 wherein the curable composition further comprises (e) solvent.

11. The anion exchange membrane according to claim 1 wherein the curable composition comprises: from 50 to 90 wt % of component (a), from 0 to 10 wt % of a monomer comprising a cationically charged group and one and only one curable ethylenically unsaturated group as component (b), from 0 to 10 wt % of a radical initiator as component (c), from 0 to 5 wt % of a monomer free from cationically charged groups as component (d) and from 10 to 40 wt % solvent as component (e).

12. The anion exchange membrane according to claim 1 which further comprises a porous support.

13. A process for preparing an anion exchange membrane which comprises curing a curable composition as defined in claim 1.

14. The process according to claim 13 which comprises the steps of: (i) providing a curable composition as defined in claim 1; (ii) applying the curable composition onto a porous support whereby at least a part of the curable composition impregnates the porous support; and (iii) curing the curable composition.

15. An electrodialysis device, a bipolar electrodialysis device, an electrolyser, a redox flow battery, an acid-base flow battery or a fuel cell comprising one or more anion exchange membranes according to claim 1.

16. A method of using the anion exchange membrane according to claim 1 for the treatment of polar liquids, for the production the acids and bases or for the generation or storage of electricity.

Description

EXAMPLES EX1 TO EX6 AND COMPARABLE EXAMPLES CEX1 AND CEX2

TABLE-US-00003 TABLE 3 Curable Compositions and results Materials (wt %) Component Ex1 Ex2 Ex3 Ex4 Ex5 Ex6 AXL-1 (a) 73.00 67.92 70.50 AXL-2 (a) 73.00 AXL-3 (a) 73.00 AXL-4 (a) 73.00 CL-1 VBTMAC (b) 5.08 2.50 4-OH-TEMPO 0.02 0.02 0.02 0.02 0.02 0.02 1173 (c) 0.75 0.75 0.75 0.75 0.75 0.75 TPO-L (c) 0.75 0.75 0.75 0.75 0.75 0.75 V-501 (c) 0.50 0.50 0.50 0.50 0.50 0.50 n-propanol (e) 5.50 5.50 5.50 5.50 5.50 5.50 PW (e) 19.48 19.48 19.48 19.48 19.48 19.48 Total (e) 100 100 100 100 100 100 Molar fraction of 1.00 0.90 0.95 1.00 1.00 1.00 component (a) pH stability OK OK OK OK OK OK IEC (meq/g dry 1.55 1.59 1.57 1.32 1.38 1.43 membrane) PS (%) 63.2 50.8 56.3 62.8 63.5 62.4 ER (ohm .Math. cm.sup.2) 12.6 9.5 6.7 11.2 12.3 13.8 Materials (wt %) Component CEx1 CEx2 AXL-1 (a) 53.70 AXL-2 (a) AXL-3 (a) AXL-4 (a) CL-1 73.00 VBTMAC (b) 19.30 4-OH-TEMPO 0.02 0.02 1173 (c) 0.75 0.75 TPO-L (c) 0.75 0.75 V-501 (c) 0.50 0.50 n-propanol (e) 5.50 5.50 PW (e) 19.48 19.48 Total (e) 100 100 Molar fraction of 0.65 1.00 component (a) pH stability OK NG IEC (meq/g dry 1.70 2.03 membrane) PS (%) 32.8 30.8 ER (ohm .Math. cm.sup.2) 8.7 3.1

[0116] The molar fraction of component (a) in Comparative Example 1 is low resulting in a low PS. In Comparative Example 2 component (a) is not according to Formula (I).

Preparation of the Curable Compositions and the Anion Exchange Membranes

[0117] The curable compositions shown in Table 3 above were prepared by mixing sequentially the stated amounts of the components (in wt %) in a mixture of the stated amounts of water/n-propanol at a temperature of 40 C.

[0118] Anion exchange membranes according to the first aspect of the present invention and Comparative Examples were prepared by applying at room temperature (21 C.) each of the curable compositions described in Table 3 to a porous support (PS1) using a 100 m Meyer bar, removing excess curable composition using a 4 m Meyer bar and then curing the composition. UV curing was performed by placing the samples of the porous supports carrying the curable compositions on a conveyor at 5 m/min equipped with a D bulb in a Light Hammer 10 of Fusion UV Systems Inc. and exposing the curable compositions to the UV light emitted from the D bulb at 50% power. The UV cured samples were covered by a 60 m polyethylene terephthalate (PET) foil without any surface treatment (from Toray) and were placed into a metallized vacuum sealed bag. The bag containing the UV cured membrane was then cured thermally (as a second curing step) in a regular oven for 3 hours at 90 C.