Membranes and Their Uses

Abstract

Ion exchange membranes obtainable by curing a composition comprising: (a) a curable monomer comprising at least one anionic or cationic group; (b) a photoinitiator which has an absorption maximum at a wavelength longer than 380 nm when measured in one or more of the following solvents at a temperature of 23° C.: water, ethanol and toluene; (c) at least one co-initiator; and optionally (d) optionally a curable monomer which is free from anionic and cationic groups; wherein at least one of the curable monomers present in the composition comprises an aromatic group.

Claims

1. An ion exchange membrane obtainable by curing a composition comprising: (a) a curable monomer comprising at least one anionic or cationic group; (b) a photoinitiator which has an absorption maximum at a wavelength longer than 380 nm when measured in one or more of the following solvents at a temperature of 23° C.: water, ethanol and toluene; (c) at least one co-initiator; and optionally (d) a curable monomer which is free from anionic and cationic groups; wherein at least one of the curable monomers present in the composition comprises an aromatic group.

2. The ion exchange membrane according to claim 1 wherein component (b) is a photoinitiator which has an absorption maximum at a wavelength in the range 385 to 800 nm when measured in one or more of the following solvents at a temperature of 23° C.: water, ethanol and toluene.

3. The ion exchange membrane according to claim 1 wherein the said photoinitiator is a Norrish Type II photoinitiator.

4. The ion exchange membrane according to claim 1 wherein the composition further comprises: (e) solvent.

5. The ion exchange membrane according to claim 1 wherein the molar attenuation coefficient of component (b) at the absorption maximum is at least 7,500 M.sup.−1 cm.sup.−1.

6. The ion exchange membrane according to claim 1 wherein the co-initiator is a chemical which can generate a free radical in reaction with component (b) when the latter is in an electronic exited state.

7. The ion exchange membrane according to claim 1 wherein the composition satisfies Equation 1:
(A1/A2)>1.5   Equation 1 wherein: A1 is the attenuation coefficient of the composition at wavelength X nm; A2 is the attenuation coefficient at wavelength X nm of a composition identical to the composition except that component (b) is omitted; and X nm is the wavelength of the absorption maximum of component (b); wherein the attenuation coefficients are all measured at a temperature of 23° C.

8. The ion exchange membrane according to claim 1 wherein component (c) comprises a tertiary amine, an acrylated amine, an onium salt (e.g. a salt of an iodonium, sulfonium, phosphonium or diazonium ion), a triazine derivative, an organohalogen compound, an ether group, a ketone, a thiol, a borate salt, a sulfide, a pyridinium salt, a ferrocenium salt, or two or more thereof.

9. The ion exchange membrane according to claim 1 wherein component (b) comprises a xanthene, flavin, curcumin, porphyrin, anthraquinone, phenoxazine, camphorquinone, phenazine, acridine, phenothiazine, xanthone, thioxanthone, thioxanthene, acridine, acridone, flavone, coumarin, fluorenone, quinolone, naphtaquinone, quinolinone, arylmethane, azo, benzophenone, carotenoid, cyanine, phtalocyanine, dipyrrin, squarine, stilbene, styryl, triazine and/or anthocyanin derived photoinitiator, in each case having an absorption maximum at a wavelength longer than 380 nm, when measured in a solvent selected from water, ethanol and toluene at a temperature of 23° C.

10. The ion exchange membrane according to claim 1 wherein the composition comprises: (a) from 2 to 95 wt % of component (a); (b) from 0.002 to 4 wt % of component (b); (c) from 0.01 to 40 wt % of component (c); and (d) from 0 to 50 wt % of component (d).

11. The ion exchange membrane according to claim 1 wherein the composition further comprises 0 to 60 wt % of (e) solvent.

12. The ion exchange membrane according to claim 11 wherein component (e) comprises at least 50 wt % water.

13. The ion exchange membrane according to claim 1 which further comprises a porous support.

14. The ion exchange membrane according to claim 1 comprising at least 0.0005 wt % of the photoinitiator which has an absorption maximum at a wavelength longer than 380 nm when measured in one or more of the following solvents at a temperature of 23° C.: water, ethanol and toluene.

15. A process for preparing an ion exchange membrane comprising curing the composition defined in claim 1.

16. The process according to claim 15 wherein the composition is cured using light having a peak irradiance at a wavelength longer than 380 nm using a dose of at least 40 mJ/cm.sup.2.

17. The process according to claim 15 which comprises the step of applying the composition to a porous support prior to curing.

18. The process according to claim 15 which further comprises the step of washing and/or drying the cured composition.

19. A method of using an ion exchange membrane according to claim 1 for treatment of an aqueous stream, for example for water softening, tartaric stabilization of wine, demineralization of whey, for purification of a liquid (e.g. water, a sugar syrup, fruit juice, organic solvents, mineral oils and a solution of metal ions), catalyzing a chemical reaction, dehumidification, or for the generation of energy.

20. A stack comprising ion exchange membranes according to claim 1 comprising alternate anionic membranes cationic membranes wherein the anionic membranes each have the same colour and/or depth of shade as each other and a different colour and/or depth of shade from the cationic membranes.

21. An electrodialysis or reverse electrodialysis unit, an electrodeionization module, a flow through capacitor, a diffusion dialysis apparatus, a membrane distillation module, an electrolyser, a redox flow battery or an acid-base flow battery, comprising one or more ion exchange membranes according to claim 1.

22. The ion exchange membrane according to claim 1 wherein said photoinitiator comprises a conjugated system having at least 10 delocalized electrons.

Description

PREPARATION OF MEMBRANE EXAMPLES 1 TO 34 AND COMPARATIVE MEMBRANE EXAMPLES CEX1 TO CEX4

[0161] The compositions described in Table 2 below were prepared by dissolving the ingredients specified in pure water (the water makes up the amount to 100 wt %). In the final column of Table 2 “A” means an anionic exchange membrane (CEM) and “C” means a cationic exchange membrane (AEM).

[0162] In Table 2 “Time (sec.)” means the time in seconds required for the composition to become 90% cured. The point at which the composition was 90% cured was determined by the DSC method described above.

[0163] Procedure: 20 mg of each composition under test was placed in a DSC pan at 25° C. and irradiated for 10 minutes from 1 cm distance using a Sylvania ES50 V4 620LM DIM 865 36° SL lamp. The curing was followed by measuring the heat of the reaction formed against a reference DSC pan containing 20 mg of the same photoinitiator as that used in the composition under test in the same solvent. The composition under test was deemed to be acceptable if the cure time in seconds (i.e. the time in seconds required for the composition to become 90% cured) was less than 300 seconds. Preferably, the cure time was lower than 150 seconds. Results are given in Table 2.

TABLE-US-00003 TABLE 2 Preparation of Membranes Composition Cure Component Photointiator Component Time Type of Example (a) (wt %) (wt %) (c) (wt %) (sec.) membrane CEX1 DMAPAA-Q Anthraquinone 2- TEOA (1.0) >600 C (50) sulfonate (0.25) (Comparative) CEX2 Na-AMPS Michlers' ketone (0.10) TEOA + IO >600 A (50) (Comparative) (1.0 + 0.1) CEX3 LiP (50) Darocur ™ 1173 (0.50) — >600 A (Comparative) CEX4 VBTMAC (50) Anthraquinone 2- TEOA + IO >600 C sulfonate (0.50) (1.0 + 0.1) (Comparative) 1 LiP (50) Methylene Blue (0.20) TEOA + IO 120 A (4.0 + 0.2) 2 LiP (50) Rose Bengal (0.20) TEOA + IO 100 A (3.0 + 0.2) 3 LiP (50) Flavin mononucleotide TEOA + IO 150 A (0.50) (4.0 + 0.2) 4 LiP (50) Fluorescein sodium TEOA + IO 80 A salt (0.20) (4.0 + 0.5) 5 LiP (50) Eosin Y disodium salt TEOA + IO 100 A (0.20) (4.0 + 0.2) 6 LiP (50) Eosin Y disodium salt TEOA + IO 150 A (0.05) (4.0 + 0.2) 7 LiP (50) Eosin Y disodium salt TEOA + IO 150 A (0.50) (4.0 + 0.2) 8 LiP (50) Eosin Y disodium salt TEOA + IO 250 A (1.0) (4.0 + 0.2) 9 VBTMAC (50) Methylene Blue (0.20) TEOA + IO 120 C (4.0 + 0.2) 10 VBTMAC (50) Rose Bengal (0.20) TEOA + IO 100 C (3.0 + 0.2) 11 VBTMAC (50) Flavin mononucleotide TEOA + IO 100 C (0.50) (4.0 + 0.2) 12 VBTMAC (50) Fluorescein sodium TEOA + IO 70 C salt (0.20) (4.0 + 0.5) 13 VBTMAC (50) Eosin Y disodium salt TEOA + IO 80 C (0.20) (4.0 + 0.2) 14 VBTMAC (50) Eosin Y disodium salt TEOA + IO 120 C (0.05) (4.0 + 0.2) 15 VBTMAC (50) Eosin Y disodium salt TEOA + IO 120 C (0.50) (4.0 + 0.2) 16 VBTMAC (50) Eosin Y disodium salt TEOA + IO 200 C (1.0) (4.0 + 0.2) 17 DMAPAA-Q Methylene Blue (0.20) TEOA + IO 90 C (50) (1.0 + 0.1) 18 DMAPAA-Q Rose Bengal (0.20) TEOA (1.0) 70 C (50) 19 DMAPAA-Q Flavin mononucleotide TEOA (1.0) 60 C (50) (0.20) 20 DMAPAA-Q Fluorescein sodium TEOA (0.5) 80 C (50) salt (0.20) 21 DMAPAA-Q Eosin Y disodium salt TEOA + IO 40 C (50) (0.20) (1.0 + 0.1) 22 DMAPAA-Q Curcumin (0.20) TEOA + IO 120 C (50) (1.0 + 0.1) 23 DMAPAA-Q Lumichrome (0.20) TEOA + IO 250 C (50) (1.0 + 0.1) 24 Na-AMPS Methylene Blue (0.20) TEOA + IO 90 A (50) (1.0 + 0.1) 25 Na-AMPS Rose Bengal (0.20) TEOA + IO 40 A (50) (1.0 + 0.1) 26 Na-AMPS Flavin mononucleotide TEOA + IO 60 A (50) (0.20) (1.0 + 0.1) 27 Na-AMPS Fluorescein sodium TEOA + IO 60 A (50) salt (0.20) (0.5 + 0.1) 28 Na-AMPS Eosin Y disodium salt TEOA (1.0) 100 A (50) (0.20) 29 Na-AMPS Quinoline yellow WS TEOA (1.0) 120 A (50) (0.20) 30 DMAPAA-Q Erythrosin B (0.025) TEOA + IO 60 A (15) + CL-3 (0.5 + 0.25) (45) 31 DMAPAA-Q Erythrosin B (0.1) TEOA + IO 40 A (15) + CL-3 (0.5 + 0.25) (45) 32 DMAPAA-Q Erythrosin B (0.5) TEOA + IO 60 A (15) + CL-3 (0.5 + 0.25) (45) 33 DMAPAA-Q Flavin mononucleotide TEOA + IO 60 A (15) + CL-3 (0.1) (0.5 + 0.25) (45) 34 DMAPAA-Q Flavin mononucleotide TEOA + IO 80 A (15) + CL-3 (0.5) (0.5 + 0.25) (45)

[0164] For a few examples from Table 2 the attenuation coefficients of the compositions were determined with and without photoinitiator. A ratio (A1/A2)>1.5 is preferred. The results are shown in Table 3 below. [0165] A1 is the attenuation coefficient of the composition at wavelength X nm; [0166] A2 is the attenuation coefficient at wavelength X nm of a composition identical to the composition except that component (b) is omitted; and [0167] X nm is the wavelength of the absorption maximum of component (b).

TABLE-US-00004 TABLE 3 A1/A2 Component Photoinitiator Wavelength Example (a) (wt %) (wt %) A1 (/cm) A2 (/cm) X (nm) A1/A2 CEX3 LiP (50) Darocur ™ 42850 42500 240 1.01 1173 (0.50) 4 LiP (50) Fluorescein 491 2 480 246 sodium salt (0.20) 21 DMAPAA-Q Eosin Y 325 0.01 525 32500 (50) disodium salt (0.20) 29 Na-AMPS Quinoline 95 0.1 412 950 (50) yellow WS (0.20)

[0168] Anion exchange membranes (AEMs) were prepared using the compositions described in Table 4.

TABLE-US-00005 TABLE 4 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Component (type) (wt %) (wt %) (wt %) (wt %) (wt %) DMAPAA-Q (a) 15.0 15.0 15.0 15.0 15.0 CL-3 (a) 45.0 45.0 45.0 45.0 45.0 Erythrosin B (b) 0.025 0.1 0.5 Flavin 0.1 0.5 mononucleotide (b) IO (c) 0.25 0.25 0.25 0.25 0.25 TEOA (c) 0.5 0.5 0.5 0.5 0.5 Water (e) 39.225 39.15 38.75 39.15 38.75

[0169] The compositions described in Table 4 were applied to a PET sheet using a 100 μm Meyer bar. A porous support (2223-10) was placed in the layer of composition and any excess composition was scraped-off. The composition present in the porous support was then cured by placing it on a conveyer belt set at 5 m/min, equipped with a Heraeus F450 microwave-powered UV-curing system with a medium-pressure mercury bulb (240 W/cm, 100%) to give the AEMs.

[0170] The presence of photoinitiator in the membrane may be determined visibly, photospectrometrically or analytically.

[0171] The amounts of photoinitiator were determined analytically by extraction (in duplo). The analysis was performed by cutting 10×10 cm pieces of the AEMs into small rectangles that were placed in a 20 ml glass container to which 5 ml of pure water was added. The glass containers were capped and packed in aluminum foil to protect them from light. The glass containers were shaken at 125 RPM on the rotary shaker for 24 hours. Thereafter, the content of the glass containers were filtered through a 0.45 μm cellulose filter and transferred to a HPLC

[0172] Analysis Method HPLC

Instrument: Waters ACQUITY arc HPLC

Detector: 2998 ACQ-PDA

[0173] Column: TKSgelODA-100V HPLC column (4.6×150, 5 μm)
Maximum pressure: 450 [bar]

Column Temperature: 40 [° C.]

Sample Temperature: 5 [° C.]

[0174] Absorbance, resolution: 254, 270, 280, 440, 540, 485 (4.8) [nm]

[0175] 254 nm=identification Riboflavin monophosphate

[0176] 485 nm=identification of erythrosine B

Injection volume: 100 [microliter]
Run Time: 24 [min]
Next inj. Delay: 0 [min]
Installed sample loop: 250 [microliter]
Solvents: A: acetonitrile+0.1% trifluoroacetic acid [0177] B: pure water+0.1% trifluoroacetic acid

[0178] Gradient:

TABLE-US-00006 Time [min] Flow [ml/min] A [%] B [%] Initial 0.5 5 95 1 0.5 5 95 3 0.5 40 60 5 0.5 40 60 6 0.5 80 20 7 0.5 80 20 8 0.5 100 0 11 0.5 100 0 20 0.5 100 0 20.1 0.5 5 95 24 0.5 5 95 Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Extracted amounts (wt %) (wt %) (wt %) (wt %) (wt %) Erythrosin B (b) 0.002 0.012 0.050 Flavin 0.020 0.080 mononucleotide (b)