Membranes

Abstract

A composite membrane comprising: a. a porous support; b. a polymeric layer comprising dialkylsiloxane groups and a metal, the polymeric layer being present on the porous support; c. a discriminating layer present on the polymeric layer; and d. optionally a protective layer present on the discriminating layer wherein the polymeric layer has a molar ratio of metal:silicon of at least 0.0005.

Claims

1. A composite membrane comprising: a. a porous support; and b. a polymeric layer comprising dialkylsiloxane groups and a metal, the polymeric layer being present on the porous support; c. a discriminating layer present on the polymeric layer; and d. optionally a protective layer present on the discriminating layer wherein the polymeric layer has a molar ratio of metal:silicon of at least 0.0005.

2. The membrane according to claim 1, wherein the metal is derived from a metal complex.

3. The membrane according to claim 1, wherein the metal is selected from any one of groups 4 and 5 of the periodic table.

4. The membrane according to claim 1, wherein the metal is titanium, zirconium, hafnium, vanadium or niobium.

5. The membrane according to claim 1, wherein the discriminating layer comprises a polyimide comprising trifluoromethyl groups.

6. The membrane according to claim 1, wherein the average thickness of the discriminating layer is 20 nm to 2 m and the polymeric layer has an average thickness of 25 to 1200 nm.

7. The membrane according to claim 1, wherein the porous support has surface pores of average diameter 0.001 to 0.1 m.

8. The composite membrane according to claim 1 which is a composite gas separation membrane.

9. A gas separation cartridge comprising a composite membrane according to claim 1.

10. The composite membrane according to claim 1 wherein: (a) the metal is derived from a metal complex; (b) the metal is selected from any one of groups 4 and 5 of the periodic table; (c) the discriminating layer comprises a polyimide comprising trifluoromethyl groups; (d) average thickness of the discriminating layer is 20 nm to 2 m; and (e) the polymeric layer has an average thickness 25 to 1200 nm.

11. The composite membrane according to claim 10 which is a composite gas separation membrane.

12. The composite membrane according to claim 1 which is a composite gas separation membrane and has a pure water permeability at 20 C. of less than 6.10-8 m3/m2.Math.s.Math.kPa.

13. The composite membrane according to claim 10 which is a composite gas separation membrane and has a pure water permeability at 20 C. of less than 6.10-8 m3/m2.Math.s.Math.kPa.

14. A gas separation cartridge comprising a composite membrane according to claim 4.

15. A gas separation cartridge comprising a composite membrane according to claim 6.

16. A gas separation cartridge comprising a composite membrane according to claim 10.

17. A process for preparing a composite membrane comprising the steps: (i) applying to a porous support a radiation-curable composition comprising a polymerisable dialkylsiloxane and a metal; (ii) irradiating the radiation-curable composition on the support, thereby forming a polymeric layer comprising dialkylsiloxane groups and a metal on the porous support; (iii) forming a discriminating layer on the polymeric layer; and (iv) optionally forming a protective layer on the discriminating layer; wherein the polymeric layer has a molar ratio of metal:silicon of at least 0.0005.

18. The process according to claim 17 wherein the radiation-curable composition comprises a metal complex and a polymerisable poly(dialkylsiloxane).

19. The process according to claim 17 which further comprises the step of forming a protective layer on the discriminating layer (step (iv)).

20. The process according to claim 19 wherein: (a) the metal is derived from a metal complex; (b) the metal is selected from any one of groups 4 and 5 of the periodic table; (c) the discriminating layer comprises a polyimide comprising trifluoromethyl groups; (d) average thickness of the discriminating layer is 20 nm to 2 m; and (e) the polymeric layer has an average thickness 25 to 1200 nm.

Description

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLE 1

Preparation of Radiation-Curable Polymers Comprising Dialkylsiloxane Groups

(1) The components UV9300, X-22-162C and DBU in the amounts indicated in Table 2 were dissolved in n-heptane and maintained at a temperature of 95 C. for the period indicated in Table 2 to form solutions of radiation curable polymer having poly(siloxane) groups having the viscosity shown in Table 2.

(2) Preparation of Radiation-Curable Compositions

(3) The solutions of radiation-curable polymers were cooled to 20 C. and diluted using n-heptane to the PCP Polymer concentrations indicated in Table 2. The solutions were then filtered through a filter paper having a pore size of 2.7 m to give radiation curable compositions. The photoinitiator UV9390C and a metal complex (Ti(OiPr).sub.4) were then added in the amounts indicated in Table 2 to give curable radiation-curable compositions.

(4) Steps (i) and (ii)Applying the Radiation-Curable Composition to a Porous Support & Curing to Form a polymeric Layer

(5) The abovementioned radiation-curable compositions were applied to a porous support (PAN) by spin coating and subsequently cured using a Light Hammer LH10 from Fusion UV Systems fitted with a D-bulb with an intensity of 24 kW/m and dried. This resulted in a porous support having a polymeric layer comprising a metal complex and dialkylsiloxane groups.

(6) Step (iii)Forming a Discriminating Layer on the Polymeric Layer

(7) The composition for the Discriminating layer was prepared by mixing the ingredients indicated in Table 1:

(8) TABLE-US-00001 TABLE 1 DL PI1 (w/w %) 1.50 APTMS (w/w %) 0.015 MIBK (w/w %) 4.50 THF (w/w %) 7.485 MEK (w/w %) 86.50

(9) A discriminating layer was formed on the polymeric layer (obtained by performing steps (i) and (ii) described above) by applying the composition thereto by spin coating.

(10) The resultant membranes had the polymeric layer thickness, Q.sub.CO2 and selectivity indicated in Table 2. The thickness of the polymeric layer was measured by cutting through the membrane and measuring the thickness from the surface of the porous support outwards by SEM.

(11) TABLE-US-00002 TABLE 2 CEx 1 Ex 1 Ex 2 Ex 3 Ex 4 Preparation UV9300 (w/w %) 39.078 39.078 39.078 39.078 36.670 of radiation- X-22-162C (w/w %) 10.789 10.789 10.789 10.789 13.322 curable DBU (w/w %) 0.007 0.007 0.007 0.007 0.009 polymer n-Heptane (w/w %) 50.126 50.126 50.126 50.126 49.999 (PCP Reaction time (h) 168 168 168 168 239 Polymer) Si (meq/g polymer) 12.2 12.2 12.2 12.2 12.2 Viscosity of PCP 22.8 22.8 22.8 22.8 240.6 polymer (mPas at 25.0 C.) Preparation PCP Polymer 5.00 5.00 5.00 5.00 3.50 of radiation- concentration in curable curable composition (w/w %) composition UV9390c (w/w %) 0.10 0.10 0.10 0.10 0.07 Ti(OiPr).sub.4 (w/w %) 0 0.1 0.15 0.2 0.0788 Ti(OiPr).sub.4 0 70.4 105.6 140.7 79.3 (mol/g PCP polymer) molar ratio of 0 0.0058 0.0087 0.0116 0.0065 metal:silicon Results polymeric layer 200-300 200-300 200-300 200-300 200-300 thickness (nm) Q.sub.CO2 3.49 .Math. 10.sup.7 2.43 .Math. 10.sup.7 1.91 .Math. 10.sup.7 1.64 .Math. 10.sup.7 2.56 .Math. 10.sup.7 (m.sup.3(STP)/m.sup.2 .Math. kPa .Math. s) Selectivity (.sub.CO2/CH4) 21.4 28.7 27.0 25.9 32.6 (Note: CEx means Comparative Example and Ex means Example. The stated molar ratio or metal:silicon is for the radiation-curable composition and the resultant polymeric layer).

(12) Using another recipe for the PCP polymer, several further metal complexes were tested. Results are given in Table 3.

(13) TABLE-US-00003 TABLE 3 Ex 5 Ex 6 Ex 7 Ex 8 Ex 9 Preparation UV9300 (w/w %) 47.371 47.371 47.371 47.371 47.371 of radiation- X-22-162C (w/w %) 12.62 12.62 12.62 12.62 12.62 curable DBU (w/w %) 0.008 0.008 0.008 0.008 0.008 polymer n-Heptane (w/w %) 40.00 40.00 40.00 40.00 40.00 (PCP Reaction time (h) 138 138 138 138 138 Polymer) Si (meq/g polymer) 12.2 12.2 12.2 12.2 12.2 Viscosity of PCP 132.6 132.6 132.6 132.6 132.6 polymer (mPas at 25.0 C.) Preparation PCP Polymer 10 10 10 10 10 of radiation- concentration in curable curable composition (w/w %) composition UV9390c (w/w %) 0.2 0.2 0.2 0.2 0.2 Ti(OBu).sub.4 (w/w %) 0.269 0 0 0 0 Ti(AcAc).sub.2(iOPr).sub.2 (w/w %) 0 0.384 0 0 0 Nb(OEt).sub.5 (w/w %) 0 0 0.252 0 0 Zr(OiPr).sub.4 (w/w %) 0 0 0 0.307 0 Zr(AcAc).sub.4 (w/w %) 0 0 0 0 0.386 Metal complex 79.3 79.3 79.3 79.3 79.3 (mol/g PCP polymer) molar ratio of 0.0065 0.0065 0.0065 0.0065 0.0065 metal:silicon Results polymeric layer 314 484 707 662 499 thickness (nm) Q.sub.CO2 2.57 .Math. 10.sup.7 2.45 .Math. 10.sup.7 2.66 .Math. 10.sup.7 2.31 .Math. 10.sup.7 2.38 .Math. 10.sup.7 (m.sup.3(STP)/m.sup.2 .Math. kPa .Math. s) Selectivity (.sub.CO2/CH4) 26.3 30.5 28.9 27.4 28.0

(14) The thickness of the polymeric layers was determined using ellipsometry, except when indicated otherwise, as follows:

(15) Equipment: Ellipsometer model M-2000F from J.A. Woollam Co. Inc.

(16) Lamp: Xenon.

(17) Software: Windows V.A.S.E.32.

(18) Settings: as model Cauchy is chosen for all layers.

(19) Thickness substrate (bulk): 0.17 mm

(20) Wavelength: all wavelengths (240-1000 nm)

(21) Measurement angles: 50-80 in steps of 5.

(22) Revs/meas.: 100.

(23) The fitting software was applied to determine the thickness of the layers as a function of refractive index.

(24) The thickness of some Examples as determined by ellipsometry, were verified in some cases by SEM.