Curable compositions and membranes
A curable composition comprising: (i) 2.5 to 50 wt % crosslinker comprising at least two acrylamide groups; (ii) 20 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and an anionic group; (iii) 15 to 45 wt % solvent; and (iv) 0 to 10 wt % of free radical initiator; wherein the composition has a pH of 0.8 to 12. 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) 20 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and an anionic group;
(iii) 15 to 45 wt % solvent; and
(iv) 0 to 10 wt % of free radical initiator;
wherein the composition has a pH of 0.8 to 12.
2. A composition according to claim 1 wherein the total wt % of components (i)+(ii) relative to the total weight of the composition is 30 to 85 wt %.
3. A composition according to claim 1 which comprises 20 to 40 wt % solvent.
4. A composition according to claim 1 wherein the molar ratio of component (i) to (ii) is at least 0.05 and below 1.0.
5. A composition according to claim 1 comprising 20 to 40 wt % solvent and wherein the molar ratio of component (i) to (ii) is at least 0.05 and below 1.0.
6. A composition according to claim 5 wherein the solvent comprises water and a water-miscible organic solvent.
7. A composition according to claim 1 which comprises 0.005 to 10 wt % photoinitiator.
8. A composition according to claim 1 wherein the ethylenically unsaturated group is an acrylamide or a methacrylamide group.
9. A composition according to claim 1 comprising:
(i) 8 to 16wt % crosslinker comprising at least two acrylamide groups;
(ii) 40 to 60 wt % curable ionic compound comprising an ethylenically unsaturated group and an anionic group;
(iii) 22 to 40 wt % solvent; and
(iv) 0.01 to 2 wt % of photoinitiator;
wherein the composition has a pH of 1 to 7.
10. 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 .
11. A process according to claim 10 wherein the composition is cured by irradiation with an electron beam or UV light for a period of less than 30 seconds.
12. A process according to claim 10 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 wherein the support moves from the curable composition application station to the irradiation source and to the membrane collecting station.
13. A composition according to claim 1 comprising 20 to 40 wt % solvent and wherein the ethylenically unsaturated group is an acrylamide or a methacrylamide group.
14. A composition according to claim 9 wherein the molar ratio of component (i) to (ii) is at least 0.05 and below 1.0.
15. A composition according to claim 9 wherein the ethylenically unsaturated group is an acrylamide or a methacrylamide group.