Curable compositions and membranes

1. An ion exchange membrane obtainable from curing a composition comprising:

(i) a curable compound of the Formula (1) comprising at least two (meth)acrylic groups and a sulphonic acid group:

wherein:

R1 and R2 are each independently H or methyl;

R3 and R4 are each independently H or alkyl, or R3 and R4 together with the N atoms to which they are attached and Y form an optionally substituted 6- or 7-membered ring; and

Y is an optionally substituted and optionally interrupted alkylene or arylene group;

provided that the compound of Formula (1) has 1, 2, 3 or 4 sulphonic acid groups;

and having a molecular weight which satisfies the equation:

MW<(300+300 n )

wherein:

MW is the molecular weight of the said curable compound of the Formula (1); and

n has a value of 1, 2, 3 or 4 and is the number of sulphonic acid groups present in the said curable compound of the Formula (1);

and optionally (ii) a curable compound having one ethylenically unsaturated group;

wherein the molar fraction of curable compounds comprising at least two (meth)acrylic groups, relative to the total number of moles of curable compounds present in the composition, is at least 0.5.

2. The ion exchange membrane according to claim 1 wherein the composition further comprises a radical initiator.

3. The ion exchange membrane according to claim 1 wherein the composition further comprises water or a mixture comprising water and a water-miscible organic solvent.

4. The ion exchange membrane according to claim 1 wherein component (ii) further comprises an anionic group.

5. The ion exchange membrane according to claim 1 comprising a structural unit of Formula (1′):

wherein:

R 1 and R 2 are each independently H or methyl;

R 3 and R 4 are each independently H or alkyl, or R 3 and R 4 together with the N atoms to which they are attached and Y form an optionally substituted 6- or 7-membered ring; and

Y is an optionally substituted and optionally interrupted alkylene or arylene group;

provided that the structural unit of Formula (1′) has 1, 2, 3 or 4 sulphonic acid groups.

6. A process for preparing an ion exchange membrane comprising the following steps:

a) applying a composition to a support; and

b) curing the composition to form an ion exchange membrane;

wherein the composition comprises:

(i) a curable compound of the Formula (1) comprising at least two (meth)acrylic groups and a sulphonic acid group:

wherein:

R1 and R2 are each independently H or methyl;

R3 and R4 are each independently H or alkyl, or R3 and R4 together with the N atoms to which they are attached and Y form an optionally substituted 6- or 7-membered ring; and

Y is an optionally substituted and optionally interrupted alkylene or arylene group;

provided that the compound of Formula (1) has 1, 2, 3 or 4 sulphonic acid groups;

and having a molecular weight which satisfies the equation:

MW<(300+300 n )

wherein:

MW is the molecular weight of the said curable compound of the Formula (1); and

n has a value of 1, 2, 3 or 4 and is the number of sulphonic acid groups present in the said curable compound of the Formula (1);

and optionally (ii) a curable compound having one ethylenically unsaturated group; wherein the molar fraction of curable compounds comprising at least two (meth)acrylic groups, relative to the total number of moles of curable compounds present in the composition, is at least 0.5.

7. The process according to claim 6 wherein the curing is performed using electron beam or UV radiation.

8. The process according to claim 6 wherein the composition is applied continuously to a moving support by means of a manufacturing unit comprising a composition application station, an irradiation source for curing the composition, an ion exchange membrane collecting station and a means for moving the support from the composition application station to the irradiation source and to the ion exchange membrane collecting station.

9. An electrodialysis or reverse electrodialysis unit, a flow through capacitor device, an electrodeionization module, a continuous electrodeionization module, a fuel cell, a diffusion dialysis apparatus, a membrane distillation module or a membrane electrode assembly comprising one or more polymeric ion exchange membranes according to claim 1 .

10. The ion exchange membrane according to claim 5 wherein the composition further comprises a radical initiator and water or a mixture comprising water and a water-miscible organic solvent.

11. The ion exchange membrane according to claim 1 wherein the composition further comprises a radical initiator and water or a mixture comprising water and a water-miscible organic solvent and component (ii) further comprises an anionic group.

12. An electrodialysis or reverse electrodialysis unit, a flow through capacitor device, an electrodeionization module, a continuous electrodeionization module, a fuel cell, a diffusion dialysis apparatus, a membrane distillation module or a membrane electrode assembly comprising one or more polymeric ion exchange membranes according to claim 5 .

13. The ion exchange membrane according to claim 1 wherein the composition further comprises:

(iii) a curable compound comprising at least two (meth)acrylic groups and being free from sulphonic acid groups;

(iv) a radical initiator; and

(v) a solvent;

wherein the composition comprises:

(a) 2 to 80 wt % of component (i), 1 to 70 wt % of component (ii), 0 to 40 wt % of component (iii), 0 to 10 wt % of component (iv); and 15 to 70 wt % of component (v); or

(b) 5 to 75 wt % of component (i), 0 to 60 wt % of component (ii), 0 to 30 wt % of component (iii), 0.1 to 10 wt % of component (iv); and 20 to 45 wt % of component (v).