Curable compositions and membranes
A curable composition comprising: (i) 2.5 to 50 wt % crosslinker comprising at least two acrylamide groups; (ii) 12 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and a cationic group; (iii) 10 to 70 wt % solvent; and (iv) 0 to 10 wt % of free radical initiator; and (v) non-curable salt; wherein the molar ratio of (i):(ii) is >0.10. The compositions are useful for preparing ion exchange membranes.
1. A curable composition comprising:
(i) 2.5 to 50 wt % crosslinker comprising at least two acrylamide groups;
(ii) 12 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and a cationic group;
(iii) 10 to 70 wt % solvent;
(iv) 0 to 10 wt % of free radical initiator; and
(v) non-curable salt comprising a cation and an anion, wherein the anion is not sulfate;
wherein the molar ratio of (i):(ii) is greater than 0.10.
2. The composition according to claim 1 wherein the molar ratio of (i):(ii) is less than 5.
3. The composition according to claim 1 wherein the total wt % of components (i) and (ii) relative to the total weight of the composition is 30 to 88 wt %.
4. The composition according to claim 1 comprising 2 to 50 wt % of non-curable salt as component (v).
5. The composition according to claim 1 wherein the molar ratio of (i):(ii) is at least 0.15 and which comprises 20 to 65 wt % of component (ii).
6. The composition according to claim 1 wherein the solvent comprises water and a water-miscible organic solvent.
7. The composition according to claim 1 which comprises 0.005 to 10 wt % photoinitiator as component (iv).
8. The composition according to claim 1 which is free from ethylenically unsaturated compounds other than components (i) and (ii).
9. The composition according to claim 1 wherein the ethylenically unsaturated group is an acrylamide or a methacrylamide group.
10. The composition according to claim 1 comprising:
(i) 5 to 35 wt % crosslinker comprising at least two acrylamide groups;
(ii) 20 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and a cationic group; and
(iii) 16 to 45 wt % solvent;
(iv) 0.01 to 2 wt % of photoinitiator; and
(v) 3 to 40 wt % of non-curable salt comprising a cation and an anion, wherein the anion is not sulfate;
wherein the molar ratio of (i):(ii) is at least 0.15.
11. The composition according to claim 1 wherein the molar ratio of (i):(ii) is at least 0.15 and less than 1.5.
12. A process for preparing a membrane comprising the following steps:
(i) applying a curable composition to a support; and
(ii) curing the composition to form a membrane;
wherein the curable composition is as defined in claim 1 .
13. The process according to claim 12 wherein the composition comprises
(i) 5 to 35 wt % crosslinker comprising at least two acrylamide groups;
(ii) 20 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and an cationic group; and
(iii) 16 to 45 wt % solvent;
(iv) 0.01 to 2 wt % of photoinitiator; and
(v) 3 to 40 wt % of non-curable salt comprising a cation and an anion, wherein the anion is not sulfate;
wherein the molar ratio of (i):(ii) is at least 0.15.
14. The process according to claim 12 wherein the composition is cured by irradiation with an electron beam or UV light for a period of less than 30 seconds.
15. The process according to claim 12 wherein the curable composition is applied continuously to a moving support using a manufacturing unit comprising a curable composition application station, an irradiation source for curing the composition, and a membrane collecting station and wherein the support moves from the curable composition application station to the irradiation source and to the membrane collecting station.
16. A composition according to claim 1 wherein the molar ratio of (i):(ii) is less than 1.5.
17. A process according to claim 13 wherein the composition is cured by irradiation with an electron beam or UV light for a period of less than 30 seconds.
18. A process according to claim 13 wherein the curable composition is applied continuously to a moving support using a manufacturing unit comprising a curable composition application station, an irradiation source for curing the composition, and a membrane collecting station and wherein the support moves from the curable composition application station to the irradiation source and to the membrane collecting station.