Curable compositions and membranes

1. A curable composition comprising:

(i) 7.47 to 43.33 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 molar ratio of (i):(ii) is 0.1 to 1.5.

2. The composition according to claim 1 wherein the molar ratio of (i):(ii) is 0.1 to 1.0 wherein the ethylenically unsaturated group is an acrylamide group or a methacrylamide group and which contains 20 to 40 wt % solvent.

3. The composition according to claim 1 comprising 20 to 40 wt % solvent and wherein the total wt % of components (i) and (ii) relative to the total weight of the composition is 30 to 85 wt % and the solvent comprises at least 40 wt % water and wherein the molar ratio of (i):(ii) is 0.13 to 0.7.

4. The composition according to claim 1 which comprises 20 to 40 wt % solvent.

5. 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 85 wt %.

6. The composition according to claim 1 wherein the solvent comprises at least 40 wt % water.

7. The composition according to claim 1 wherein the solvent comprises water and a water-miscible organic solvent.

8. The composition according to claim 1 wherein the solvent comprises a water-miscible organic solvent having a boiling point below 100° C.

9. The composition according to claim 1 which comprises 0.005 to 10 wt % photoinitiator.

10. The composition according to claim 1 which is free from ethylenically unsaturated compounds other than components (i) and (ii).

11. The composition according to claim 1 comprising:

(i) 8 to 16 wt % 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 molar ratio of (i):(ii) is 0.1 to 1.0.

12. A process for preparing a membrane comprising the following steps:

(i) applying a curable composition as defined in claim 1 to a support; and

(ii) curing the composition to form a membrane.

13. The process according to claim 12 wherein the curing is performed using electron beam or UV radiation.

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 process according to claim 12 wherein the curable composition comprises:

(i) 8 to 16 wt % 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 molar ratio of (i):(ii) is 0.1 to 1.5.

17. The process of claim 16 wherein the curing is performed using electron beam or UV radiation.

18. The process according to claim 16 wherein the composition is cured by irradiation with an electron beam or UV light for a period of less than 30 seconds.

19. The curable composition of claim 1 including 8 to 40 wt % crosslinker comprising at least two acrylamide groups.