Composite membranes
A composite membrane comprising a discriminating layer and a porous support layer for the discriminating layer, CHARACTERISED IN THAT the discriminating layer comprises at least 60 wt % of oxyethylene groups and the porous support layer has a CO 2 gas flux of 5 to 150×10 −5 m 3 (STP)/m 2 ·s·kPa at a feed pressure of 2.07 kPa. The membranes are particularly useful for purifying waste gas streams e.g. by removing greenhouse gases.
1. A composite membrane comprising a discriminating layer and a porous support layer for the discriminating layer, CHARACTERISED IN THAT the discriminating layer comprises at least 60 wt % of oxyethylene groups and the porous support layer has a CO 2 gas flux of 5 to 150×10 −5 m 3 (STP)/m 2 ·s·kPa at a feed pressure of 2.07 kPa.
2. A membrane according to claim 1 wherein the porous support layer has a CO 2 gas flux of 7 to 100×10-5 m 3 (STP)/m2·s·kPa at a feed pressure of 2.07 kPa.
3. A membrane according to claim 1 wherein the discriminating layer comprises at least 70 wt % of oxyethylene groups.
4. A membrane according to claim 1 wherein the thickness of the discriminating layer is 0.1 to 1 μm.
5. A membrane according to claim 1 wherein the discriminating layer is derived from a radiation curable composition.
6. A membrane according to claim 1 wherein the porous support layer has a CO 2 gas flux of 7 to 100×10-5 m3 (STP)/m2·s·kPa at a feed pressure of 2.07 kPa, the discriminating layer comprises at least 70 wt % of oxyethylene groups, the thickness of the discriminating layer is 0.1 to 1 μm and the discriminating layer is derived from a radiation curable composition.
7. A membrane according to claim 5 wherein the curable composition comprises:
(i) 0 to 80 parts in total of monofunctional compounds;
(ii) 1 to 99 parts in total of difunctional compounds;
(iii) 0 to 50 parts in total of polyfunctional compounds;
(iv) 2 to 99 parts of an inert liquid;
wherein all parts are by weight and at least 60 wt % of non-volatile components in the composition are oxyethylene groups.
8. A membrane according to claim 5 wherein the curable composition comprises:
(i) 0 to 20 parts in total of monofunctional compounds;
(ii) 1 to 20 parts in total of difunctional compounds;
(iii) 0 to 5 parts in total of polyfunctional compounds;
(iv) 70 to 99 parts of an inert liquid;
(v) 0.01 to 5 parts of photoinitiator;
wherein all parts are by weight.
9. A membrane according to claim 6 wherein oxyethylene groups constitute at most 96 wt % of the total weight of non-volatile components in the curable composition.
10. A membrane according to claim 6 wherein the curable composition comprises:
(i) 0 to 20 parts in total of monofunctional compounds;
(ii) 1 to 20 parts in total of difunctional compounds;
(iii) 0 to 5 parts in total of polyfunctional compounds;
(iv) 70 to 99 parts of an inert liquid;
(v) 0.01 to 5 parts of photoinitiator;
wherein all parts are by weight.
11. A gas separation cartridge comprising a membrane according to claim 1 .
12. A gas separation cartridge comprising a membrane according to claim 6 .
13. A gas separation cartridge comprising a membrane according to claim 10 .
14. A gas separation cartridge according to claim 11 wherein the cartridge is in spiral-wound, plate-and-frame or envelope form.
15. A gas separation cartridge according to claim 12 wherein the cartridge is in spiral-wound, plate-and-frame or envelope form.
16. A gas separation cartridge according to claim 13 wherein the cartridge is in spiral-wound, plate-and-frame or envelope form.
17. A process for preparing a composite membrane comprising applying a curable composition to a porous support layer having a CO 2 gas flux of 5 to 150×10 −5 m 3 (STP)/m 2 ·s·kPa, when measured at a feed pressure of 2.07 kPa, and curing the composition, thereby forming a discriminating layer on the porous support layer, wherein the curable composition comprises non-volatile and optionally volatile components and at least 60 wt % of the non-volatile components are oxyethylene groups.
18. A process according to claim 17 wherein the curable composition is applied continuously to the porous support layer by means of a manufacturing unit comprising a curable composition application station, an irradiation source, a composite membrane collecting station and a means for moving a porous support layer from the curable composition application station to the irradiation source and to the composite membrane collecting station.
19. A process according to claim 17 wherein the composition is a radiation curable composition and the curing is achieved by irradiating the composition for less than 30 seconds.
20. A process according to claim 18 wherein the composition is a radiation curable composition and the curing is achieved by irradiating the composition for less than 30 seconds.