Composite Membranes

Abstract

A process for preparing a composite membrane comprising the steps: a) applying a radiation-curable composition to a porous support; b) irradiating the composition present on the support, thereby forming a gutter layer of cured polymer; c) forming a discriminating layer on the gutter layer; and d) applying a radiation-curable composition to the discriminating layer and irradiating that composition, thereby forming a protective layer on the discriminating layer; wherein one or both of the radiation-curable compositions applied in steps a) and d) comprise a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1. Also claimed are composite membranes and gas separation cartridges comprising the membranes.

Claims

1. A process for preparing a composite membrane comprising the steps: a) applying a radiation-curable composition to a porous support; b) irradiating the composition present on the support, thereby forming a gutter layer of cured polymer; c) forming a discriminating layer on the gutter layer; and d) applying a radiation-curable composition to the discriminating layer and irradiating that composition, thereby forming a protective layer on the discriminating layer; wherein one or both of the radiation-curable compositions applied in steps a) and d) comprise a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

2. The process according to claim 1 wherein the radiation-curable composition applied in step a) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1 cm.sup.?1.

3. The process according to claim 1 wherein the radiation-curable composition applied in step a) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1 and the radiation-curable composition applied in step d) is free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

4. The process according to claim 1 wherein the radiation-curable compositions applied in step a) and in step d) each independently comprise a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

5. The process according to claim 1 wherein the radiation-curable composition applied in step a) is free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1 and the radiation-curable composition applied in step d) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

6. The process according to claim 1 wherein the photo acid generator has an absorbency coefficient ? at 313 nm of more than 3?10.sup.4 mol.sup.?1*cm.sup.?1.

7. The process according to claim 1 wherein the photo acid generator is a compound which generates acid when irradiated with light of wavelength 313 nm.

8. (canceled)

9. The process according to claim 1 wherein the photo acid generator comprise a cation having a solubility parameter value greater than 22 (J/cm.sup.3).sup.0.5.

10.-16. (canceled)

17. The process according to claim 1 wherein: the radiation-curable composition is applied continuously to the porous support in step a) by means of a manufacturing unit comprising a radiation-curable composition application station, step b) is performed using an irradiation source located downstream from the radiation-curable composition application station, the discriminating layer is formed on the layer of cured polymer in step c) by a discriminating layer application station, and the resultant composite membrane is collected at a collecting station, wherein the manufacturing unit comprises a means for moving the porous support from the radiation-curable composition application station to the irradiation source and to the discriminating layer application station and to the composite membrane collecting station.

18. The process according to claim 17 wherein the porous support is continuously unwound from a spool and the resultant composite membrane is continuously wound onto a spool.

19. The process according to claim 1 wherein step a) and/or step c) is or are performed by curtain coating, meniscus type dip coating, kiss coating, pre-metered slot die coating, reverse or forward kiss gravure coating, multi roll gravure coating, spin coating and/or slide bead coating.

20. A composite membrane comprising: i) a porous support; ii) a gutter layer; iii) a discriminating layer on the gutter layer; and iv) a protective layer; wherein one or both of the gutter layer ii) and the protective layer iv) comprise a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

21. (canceled)

22. The composite membrane according to claim 20 wherein the gutter layer ii) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

23. The composite membrane according to claim 20 wherein (a) the gutter layer ii) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1; and (b) the protective layer iv) is free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

24. The composite membrane according to claim 20 wherein the gutter layer ii) and the protective layer iv) each independently comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

25. The composite membrane according to claim 20 wherein (a) the gutter layer ii) is free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1; and (b) the protective layer iv) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

26. A gas separation cartridge comprising the composite membrane according to claim 20 wherein the cartridge is of plate-and-frame, spiral-wound, hollow-fibre, tubular or envelope type.

27. The process according to claim 1 wherein the radiation-curable composition applied in step a) is free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1 and the radiation-curable composition applied in step d) comprises a photo acid generator having an absorbency coefficient ? at 313 nm of more than 3?10.sup.4 mol.sup.?1*cm.sup.?1.

28. The composite membrane according to claim 20 wherein the photo acid generator has an absorbency coefficient ? at 313 nm of more than 3?10.sup.4 mol.sup.?1*cm.sup.?1.

Description

EXAMPLES AND COMPARATIVE EXAMPLES

Stage a) Preparation of the PCP Polymer

[0211] A solution of a PCP Polymer (PCP Polymer 1) was prepared by heating the components described in Table 1 together for 105 hours at 95? C. The resultant solution of PCP Polymer 1 had a viscosity of about 64,300 mPas when measured at 25? C.

TABLE-US-00002 TABLE 1 Ingredients used to prepare PCP Polymer 1 Ingredient Amount (w/w %) UV-9300 46.4% X-22-162C 13.6% n-Heptane 40.0% DBU 0.0% Total 100.0%

Stage b) Preparation of Radiation-Curable Compositions (RCCs) 1 to 4

[0212] Portions of the solution of PCP Polymer 1 obtained in stage a) above were cooled to 20? C., diluted with n-heptane and then filtered through a filter paper having an average pore size of 2.7 ?m. The ingredients indicated in Table 2 below were added to make RCC1 to 4 as indicated in Table 2 below wherein the % are w/w % (weight/weight %).

TABLE-US-00003 TABLE 2 Ingredient RCC1 RCC2 RCC3 RCC4 PCP Polymer 1 16.67% 16.67% 16.67% 16.67% n-Heptane 81.00% 62.97% 63.06% 63.02% MEK 2.00% 20.00% 20.00% 20.00% Tyzor.sup.(R) TPT 0.22% 0.22% 0.22% 0.22% I0591 0.11% Irgacure.sup.(R) 290 0.14% CPI-100P 0.05% UV9390C 0.09% Total 100.0% 100.0% 100.0% 100.0% Solids content 10% 10% 10% 10% PAG content mmol/g 0.00104 0.00104 0.00104 0.00104

Stage c) Preparation of the Composition Used to Form a Discriminating Layer

[0213] Composition DSL1 was prepared by mixing the components shown in Table 3 (wherein the % are w/w %) and filtering the mixture through a filter paper having an average pore size of 2.7 ?m.

TABLE-US-00004 TABLE 3 Ingredient DSL1 PI 1.00% MEK 94.0% DIOX 5.0% APTMS 0.0100% Total 100.01%

Stage d) Preparation of Compositions Used to Form a Protective Layer

[0214] Compositions PL1 to PL4 were prepared by mixing the components shown in Table 4 (wherein the % are w/w %) and filtering the mixture through a filter paper having an average pore size of 2.7 ?m.

TABLE-US-00005 TABLE 4 Ingredient PL1 PL2 PL3 PL4 PCP polymer 11.67% 11.67% 11.67% 11.67% n-Heptane 86.11% 68.08% 68.14% 68.12% MEK 2.00% 20.00% 20.00% 20.00% Tyzor.sup.(R) TPT 0.15% 0.15% 0.15% 0.15% I0591 0.07% Irgacure.sup.(R) 290 0.10% CPI-110P 0.04% UV9390C 0.06% Total 100.0% 100.0% 100.0% 100.0% Solid content 7% 7% 7% 7% PAG content mmol/g 0.00073 0.00073 0.00073 0.00073

Stage e) Preparation of Composite Membranes

[0215] Composite membranes were prepared using the combinations of radiation-curable composition and discriminating layers described in Table 5.

[0216] The radiation-curable compositions RCC1 to RCC4 were applied to a MAT (step a)) at a speed of 10 m/min by a meniscus dip coating and irradiated. Irradiation (step b)) was performed using a Light Hammer LH10 from Fusion UV Systems fitted with a D-bulb and irradiating with an intensity of 16.8 kW/m (70%). The resultant gutter layers had a dry thickness of 300 nm. Discriminating layers were formed on the gutter layers (step c)) using the compositions DSL1 as indicated in Table 4, using a meniscus type coating T 10 m/min coating speed. In Examples 1 to 5 the GL and/or PL comprised a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1. In Comparative Examples CEx1 and CEx2 both the GL and PL were free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1.

[0217] After steps a) to d) had been completed, the resultant composite membranes were dried and tested. The tests were performed on circular patches of the composite membrane having a diameter of 47 mm and the patches were exposed to the relevant gases (clean or dirty) for a continuous period of 5 minutes by applying the gases to one side of the membrane under test at a pressure of 60 bar while the other side of the membrane was open to the atmosphere and therefore was subjected to air at a pressure of 1 atmosphere. The test results are shown in Table 5 below.

TABLE-US-00006 TABLE 5 CEx1 Ex1 Ex2 Ex3 Ex4 Ex5 CEx2 Porous Support GMT GMT GMT GMT GMT GMT GMT Radiation-curable RCC1 RCC1 RCC2 RCC1 RCC3 RCC2 RCC4 composition used to form the GL Coating speed used 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min to form the GL Amount of radiation- 6 mL/m2 6 mL/m2 6 mL/m2 6 mL/m2 6 mL/m2 6 mL/m2 6 mL/m2 curable composition applied to the porous support to form the GL UV bulb used to H-bulb H-bulb H-bulb H-bulb H-bulb H-bulb H-bulb irradiate the radiation- curable composition Dry thickness of 600 nm 600 nm 600 nm 600 nm 600 nm 600 nm 600 nm the resultant GL Composition used DSL1 DSL1 DSL1 DSL1 DSL1 DSL1 DSL1 to form the DL Amount of composition 10 mL/m.sup.2 10 mL/m.sup.2 10 mL/m.sup.2 10 mL/m.sup.2 10 mL/m.sup.2 10 mL/m.sup.2 10 mL/m.sup.2 applied to the GL to form the DL Dry thickness of the 100 nm 100 nm 100 nm 100 nm 100 nm 100 nm 100 nm resultant DL Composition used to PL1 PL2 PL2 PL3 PL3 PL1 PL4 form the PL Coating speed used to 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min 10 m/min form the PL Amount of composition 9 mL/m.sup.2 9 mL/m.sup.2 9 mL/m.sup.2 9 mL/m.sup.2 9 mL/m.sup.2 9 mL/m.sup.2 9 mL/m.sup.2 applied to the DL to form the PL UV bulb used to H-bulb H-bulb H-bulb H-bulb H-bulb H-bulb H-bulb irradiate the composition used to form the PL Dry thickness of 595 nm 595 nm 595 nm 595 nm 595 nm 595 nm 595 nm the resultant PL ? at 313 nm (mol.sup.?1*cm.sup.?1) 6,915 6,915 44,239 6,915 16,497 44,239 850 of PAG in GL ? of PAG cation in GL 20.60 20.60 25.20 20.60 23.20 23.20 19.00 ? at 313 nm (mol.sup.?1*cm.sup.?1) 6,915 44,239 44,239 16,497 16,497 6,915 850 of PAG in PL ? of PAG cation in PL 20.60 25.20 25.20 23.20 23.20 20.60 19.00 RESULTS: Clean Gas evaluation: 60 bar, 40? C. CO.sub.2 flux (GPU) 52 44 38 48 41 36 55 CO.sub.2/CH.sub.4 selectivity 27 32 32 26 26 33 23 Dirty Gas evaluation: 60 bar, 40? C. CO.sub.2 flux (GPU) 48 35 30 43 38 32 60 CO.sub.2/CH.sub.4 selectivity 17 26 29 19 20 24 13 Relative Performance: Dirty Gas evaluation vs. Clean Gas evaluation: Selectivity ratio (Dirty 0.63 0.81 0.91 0.73 0.77 0.73 0.57 Gas/Clean Gas)

[0218] In Table 5 GL means gutter layer, DL means discriminating layer and PL means protective layer.

[0219] As can be seen from Table 5, Comparative Examples 1 and 2 in which the GL and PL were both free from photo acid generators having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1 suffered from much lower selectivity for dirty gas than for clean gas. However the Examples of the invention in which the GL and/or PL comprised a photo acid generator having an absorbency coefficient ? at 313 nm of more than 1?10.sup.4 mol.sup.?1*cm.sup.?1 retained good selectivity even when the gas was a dirty gas.