Radiation-Curable Compositions, Membranes and the Manufacture and Use of Such Membranes

Abstract

A radiation-curable composition comprising: a) 10 to 65 wt % of curable ionic compound(s) comprising one ethylenically unsaturated group; b) 3 to 60 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight below 800; c) 5 to 55 wt % of inert solvent(s) having a boiling point above 100? C.; d) 0 to 10 wt % of free-radical initiator(s); and e) 0.5 to 25 wt % of thickening agent(s).

Claims

1-31. (canceled)

32. A process for preparing an ion-exchange membrane having a textured surface profile comprising the steps (i) and (ii): (i) applying a radiation-curable composition to a membrane in a patternwise manner; and (ii) irradiating and thereby curing the radiation-curable composition present on the membrane; wherein the radiation-curable composition comprises: a) 10 to 65 wt % of curable ionic compound(s) comprising one ethylenically unsaturated group; b) 3 to 60 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight below 800; c) 5 to 55 wt % of inert solvent(s) having a boiling point above 100? C.; d) 0 to 10 wt % of free-radical initiator(s); and e) 0.5 to 25 wt % of thickening agent(s).

33. The process according to claim 32 wherein the inert solvent is free from diols having a boiling point above 100? C.; triols having a boiling point above 100? C.; carbonates having a boiling point above 100? C.; dimethyl formamide; N-methyl-2-pyrrolidinone; and mixtures comprising two or more of the foregoing.

34. The process according to claim 32 wherein the inert solvent comprises dimethyl sulphoxide, 1,3-dimethyl-2-imidazolidinone, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-methoxyethyl ether or a mixture comprising two or more of the foregoing.

35. The process according to claim 32 wherein the radiation-curable composition comprises d) 0.01 to 10 wt % of photoinitiator(s).

36. The process according to claim 32 wherein the radiation-curable composition comprises a) 12 to 60 wt % of curable ionic compound(s) comprising one acrylic group and one or more acidic or basic group selected from sulfo, carboxy, phosphato, quaternary amino and tertiary amino groups.

37. The process according to claim 32 wherein the radiation-curable composition comprises b) 4 to 55 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight below 800.

38. The process according to claim 32 wherein the radiation-curable composition further comprises h) 1 to 15 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight of 800 to 8,000 Daltons.

39. The process according to claim 32 wherein the The process according to claim 1 wherein the radiation-curable composition comprises e) 1 to 15 wt % of thickening agent(s) comprising an inorganic filler selected from hydrophilic metal oxides, carbon black, clays and calcium carbonate in a form which has a BET surface area greater than 50 m.sup.2/g.

40. The process according to claim 32 wherein the radiation-curable composition comprises: a) 12 to 60 wt % of curable ionic compound(s) comprising one acrylic group and one or more acidic or basic group selected from sulfo, carboxy, phosphato, quaternary amino and tertiary amino groups; b) 4 to 55 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight below 800; c) 5 to 50 wt % of inert solvent(s) having a boiling point above 100? C.; d) 0.01 to 10 wt % of free-radical initiator(s); e) 1 to 15 wt % of thickening agent(s) comprising an inorganic filler selected from hydrophilic metal oxides, carbon black, clays and calcium carbonate in a form which has an average particle size below 0.05 ?m and/or a BET surface area greater than 50 m.sup.2/g; and h) 1 to 15 wt % of crosslinking agent(s) comprising at least two ethylenically unsaturated groups and having a number average molecular weight of 800 to 8,000 Daltons.

41. The process according to claim 32 wherein the radiation-curable composition further comprises f) 2 to 40 wt % water.

42. The process according to claim 32 wherein the step (i) comprises screen printing the radiation-curable composition onto a membrane in a patternwise manner.

43. The process according to claim 32 wherein during curing some or all components of the composition polymerise to form the desired surface profile.

44. The process according to claim 32 wherein the radiation-curable composition used in step (i) has a viscosity of at least 10 Pa.Math.s at a shear rate of 1.5 s.sup.?1 and a viscosity of <10 Pa.Math.s at a shear rate of 1000 s.sup.?1, when measured at 20? C.

45. The process according to claim 32 wherein the ratio of the viscosity when measured at a shear rate of 1.5 s.sup.?1 at 20? C. to the viscosity when measured at a shear rate of 1000 s.sup.?1 at 20? C. is between 1.5 and 5000.

46. The process according to claim 32 wherein the textured surface profile comprises protrusions which have an average height of 5 to 500 ?m.

47. The process according to claim 42 wherein the screen-printing comprises rotary screen-printing, flatbed screen-printing or rotary-stop-cylinder screen-printing.

48. The process according to claim 42 wherein the screen-printing comprises applying the radiation-curable composition to the membrane through a rotating, tubular screen.

49. The process according to claim 32 which is a continuous process and wherein the radiation-curable composition is applied to the membrane while the membrane is moving.

50. The process according to claim 32 which further comprises the preparation of the membrane used in step (i) by a process comprising the steps (A) and (B): (A) impregnating a porous support with a radiation-curable composition; (B) forming the membrane by irradiating and thereby curing the radiation-curable curable composition present in the porous support.

51. The process according to claim 50 wherein the radiation-curable composition used in step (i) has a higher viscosity than the radiation-curable composition used in step (A).

52. An ion-exchange membrane having a textured surface profile obtained by a process according to claim 32.

53. The ion-exchange membrane according to claim 52 wherein the textured surface profile comprises protrusions which have an average length (L) to average width (W) ratio of 10:1 to 1:10 when measured at the base of the protrusion.

54. The ion-exchange membrane according to claim 52 wherein the textured surface profile comprises protrusions which are separated from each other by an average of at least 0.1 mm.

55. The ion-exchange membrane according to claim 52 wherein the textured surface profile comprises protrusions wherein at least 80% of the protrusions have a maximum dimension in all directions of less than 20 mm.

56. The ion-exchange membrane according to claim 52 wherein the textured surface profile comprises protrusions that are ionically charged and wherein the ratio of the area of texture is 2 to 40%.

57. The ion-exchange membrane according to claim 52 wherein the textured surface profile comprises protrusions which have a maximum dimension in all directions of 0.04 to 10 mm.

58. An electrodialysis or reverse electrodialysis unit, an electrodeionization module, a capacitive deionization device, a diffusion dialysis apparatus or a membrane distillation module, comprising one or more textured ion-exchange membranes according to claim 52.

Description

EXAMPLES EX1 TO EX8 AND COMPARATIVE EXAMPLES CEX1 TO CEX3

[0221] The components indicated in Tables 1 and 2 below, except for the crosslinking agents and thickening agents were mixed together at 60? C. until a homogeneous solution was formed. The crosslinking agents and thickening agents were then added and the mixture stirred again to provide radiation-curable compositions. The pH was measured using Whatman? Panpeha? pH indicator strips (pH range 0 to 14); if needed the pH was adjusted by adding a small amount of concentrated NaOH solution.

TABLE-US-00001 TABLE 1 Radiation-Curable Compositions (Anionic) Component Component type CEx1 CEx2 Ex1 Ex2 Ex3 Ex4 Ex5 Water* f) 11.25 11.25 11.25 11.25 11.25 11.25 11.25 MEHQ other 0.05 0.05 0.05 0.05 0.05 0.05 0.05 IPA other 16.2 12.2 4.0 0 0 0 0 DMSO c) 0 4.0 12.2 16.2 0 0 0 EG c) 0 0 0 0 16.2 0 0 PC c) 0 0 0 0 0 16.2 0 DMI c) 0 0 0 0 0 0 16.2 AMPS a) 38.5 38.5 38.5 38.5 38.5 38.5 38.5 MBA b) 14.5 14.5 14.5 14.5 14.5 14.5 14.5 LiOHH2O g) and f) 8.5 8.5 8.5 8.5 8.5 8.5 8.5 CN998 h) 4.7 4.7 4.7 4.7 4.7 4.7 4.7 HDDA b) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Surfactant other 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Darocur 1173 d) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 BYK?-425 e) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 AeroSil? 380 e) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 total 100 100 100 100 100 100 100 pH 8 7.5 7.5 7.5 7.5 2 7.5 crystallization Not OK Not OK OK OK OK OK OK Visco at 1.5 s.sup.?1 145 151 258 301 255 27 222 Visco at 1000 s.sup.?1 3.2 3.8 6.8 6.6 4.7 2.5 4.9 Recovery OK OK OK OK OK OK OK *Added water. The compositions contained additional water from other components.

TABLE-US-00002 TABLE 2 Radiation-Curable Compositions (Cationic) Component Component type CEx3 Ex6 Ex7 Ex8 Water* f) 10.05 10.35 10.35 10.35 MEHQ Other 0.05 0.05 0.05 0.05 IPA Other 7.4 0 0 0 DMSO c) 0 7.7 0 0 EG c) 0 0 7.7 0 DMI c) 0 0 0 7.7 DMAPAA-Q a) and f) 40.5 41.7 41.7 41.7 MBA b) 11.5 11.9 11.9 11.9 LiNO3 g) 17.6 11.8 11.8 11.8 LiOHH2O g) and f) 0 3.4 3.4 3.4 CN998 h) 4.6 4.8 4.8 4.8 HDDA b) 1.2 1.2 1.2 1.2 Surfactant Other 0.3 0.3 0.3 0.3 Darocur 1173 d) 0.5 0.5 0.5 0.5 BYK?-425 e) 0.3 0.3 0.3 0.3 BYK?-428 e) 1.0 1.0 1.0 1.0 AeroSil? 380 e) 5.0 5.0 5.0 5.0 Total 100 100 100 100 pH 5 9 9 8.5 crystallization Not OK OK OK OK Visco at 1.5 s.sup.?1 55 151 172 333 Visco at 1000 s.sup.?1 0.15 1.6 4.1 2.4 Recovery OK OK OK OK *Added water. The compositions contained additional water from other components.

[0222] The radiation-curable compositions described in the Table 1 above were screen-printed in a patternwise manner using a Flat Screen Printing Machine AT-P760 from Alraun Technik, Germany, onto ion exchange membranes from FUJIFILM. The radiation-curable compositions described in Table 1 were printed onto anion exchange membranes and the radiation-curable compositions described in Table 2 were printed onto cation exchange membranes.

[0223] The printed compositions were cured on the membranes using a Light Hammer LH10 from Fusion UV Systems fitted with a D-bulb working at 100% intensity with a speed of 30 m/min (single pass) to give membranes having textured surface profiles. The surface profiles had a rectangular form of about 1 mm length, 1 mm width and a height of 120 ?m. The distance between the protrusions was about 2 mm.

[0224] The wet adhesion of the cured, screen printed compositions to the underlying membranes was measured by equilibrating the printed, textured membranes in water for 2 hours and then scratching the textured surface profile with a finger nail. When the protrusions present in the textured surface profile could not be removed by scratching, the wet adhesion was good; and when they could be removed easily the wet adhesion it was bad. The wet adhesion of all samples was good.