Porous membranes for high pressure filtration

1 . A method for purifying a fluid containing at least one contaminant, said method comprising the steps of:

(I) providing a fluid containing at least one contaminant;

(II) providing a flat membrane (membrane (PSP)) comprising at least one porous layer (layer (PSP)), wherein the layer (PSP) is obtained from a composition (C) comprising at least one aromatic sulfone polymer (polymer (SP)) in an amount from 7 to 60 wt. %, at least one polyphenylene polymer (polymer (PP)) in an amount of 4 to 30 wt. % and a remaining amount up to 100 wt. % of said composition (C) being provided by at least one solvent (medium (L));

(III) contacting said fluid containing at least one contaminant and said membrane (PSP) by applying a pressure higher than 1 bar to said fluid; and

(IV) recovering a fluid free from said at least one contaminant,

wherein

said polymer (PP) comprises at least about 10 mole percent, based on 100 moles of polymer (PP), of repeat units (R pm ) represented by the following formula:

and at least about 10 mol percent repeat units (Rpp) represented by the following formula:

wherein

R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylester, arylester, fluorine, chlorine, and bromine and

wherein said membrane (PSP) is characterized by:

a tensile modulus, measured according to ASTM D638 type V, of at least 235 MPa,

a gravimetric porosity comprised between 5% and 90%, and

a ratio between the tensile modulus as defined above and gravimetric porosity higher than 310 MPa.

2 . The method according to claim 1 , wherein said membrane (PSP) comprises said layer (PSP) as the only layer.

3 . The method according to claim 1 , wherein said polymer (SP) is a polymer comprising at least one group of formula —Ar—SO 2 —Ar′-(recurring units (R SP )), wherein Ar and Ar′, equal to or different from each other, are aromatic groups, and wherein more than 50% by moles of the recurring units (R SP ) of said polymer (SP) are connected by ether linkages in the main chain of the polymer.

4 . The method according to claim 3 , wherein the recurring units (R SP ) are selected from the group consisting of:

(I) recurring units (R SP- 1) of formula:

Ar 1 —(T′—Ar 2 ) n —O—Ar 3 —SO 2 —[Ar 4 —(T—Ar 2 ) n —SO 2 ] m —Ar 5 —O—(R SP-1 )

wherein:

Ar 1 , Ar 2 , Ar 3 , Ar 4 , and Ar 5 , equal to or different from each other and at each occurrence, are independently aromatic mono- or polynuclear groups;

T and T′, equal to or different from each other and at each occurrence, is independently a bond or a divalent group optionally comprising one or more than one heteroatoms;

n and m, equal to or different from each other, are independently zero or an integer of 1 to 5;

(II) recurring units (R SP-2 ) of formula:

Ar *1 —SO 2 —[Ar *2 —(T*-Ar* 3 ) n* —SO 2 ] m* —Ar* 4 —E—(R SP-2 )

wherein

each of Ar* 1 , Ar* 2 , Ar* 3 and Ar* 4 , equal to or different from each other at each occurrence, is an aromatic moiety;

n* and m*, equal to or different from each other, are independently zero or an integer of 1 to 5;

T* is a bond or a divalent group optionally comprising one or more than one heteroatom; and

E is a 1,4:3,6-dianhydrohexitol sugar diol unit selected from one or more of formulae (E-1) to (E-3):

5 . The method according to claim 3 , wherein said polymer (SP) is selected from poly (phenylene sulfone) polymers (polymers (PPSU)), poly (sulfone) polymers (polymers (PSU)) and poly (ether sulfone) polymers (polymers (PESU)).

6 . The method according to claim 5 , wherein

said poly (phenylene sulfone) polymer (polymer (PPSU)) is a polymer comprising recurring units wherein more than 50% by moles of the recurring units (R SP-1 ) of said polymer (PPSU) are recurring units (R PPSU ) of formula (K-A):

said poly (sulfone) polymer (polymer (PSU)) is an aromatic sulfone polymer wherein at least 50% by moles of the recurring units (R SP-1 ) of said polymer (PSU) are recurring units (R PSU ) of formula:

said poly (ether sulfone) polymer (polymer (PESU)) is a polymer wherein more than 50% by moles of the recurring units (R SP-1 ) of said polymer (PESU) are recurring units (RPESU) of formula:

wherein each of R′, equal to or different from each other, is selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium, and each of j′, equal to or different from each other and at each occurrence, is independently zero or is an integer from 0 to 4.

7 . The method according to claim 1 , wherein

one or more of R 1 , R 2 , R 3 , and R 4 is independently represented by formula Ar-T-, wherein

Ar is represented by a formula selected from the following group of

wherein

each R j , R k and R l is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium,

with j and l equal or different from each other, being independently 0, 1, 2, 3, 4, or 5 and,

k, equal or different from j or 1, being independently 0, 1, 2, 3 or 4;

T is selected from the group consisting of —CH 2 —; —O—; —SO 2 —; —S—; —C(O)—; —C(CH 3 ) 2 —; —C(CF 3 ) 2 —; —C(═CCl 2 )—; C—C(CH 3 )(CH 2 CH 2 COOH)—; —N═N—; —RaC═CRb—,

wherein

each Ra and Rb, independently of one another, is hydrogen, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy, or C 6 -C 18 -aryl group; —(CH 2 ) n — and —(CF 2 ) n — with n being an integer

from 1 to 6; a linear or branched aliphatic divalent group having from 1 to 6 carbon atoms;

and/or

wherein one or more of R 5 , R 6 , R 7 , and R 8 is independently represented by formula Ar″-T″-,

wherein

Ar″ is represented by a formula selected from the following group of formulae

wherein

each R j″ , R k″ and R l″ is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium,

j″ and l″, equal or different from each other being independently 0, 1, 2, 3, 4, or 5 and,

k″, equal or different from j″ or l″, being independently 0, 1, 2, 3 or 4;

T″ is selected from the group consisting of —CH 2 —; —O—; —SO 2 —; —S—; —C(O)—; —C(CH 3 ) 2 —; —C(CF 3 ) 2 —; —C(═CCl 2 )—; —C(CH 3 )(CH 2 CH 2 COOH)—; —N═N—; —R a C═CR b —,

wherein each R a and R b , independently of one another, is hydrogen, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy, or C 6 -C 18 -aryl group; —(CH 2 ) n — and —(CF 2 ) n — with n being an integer from 1 to 6; a linear or branched aliphatic divalent group having from 1 to 6 carbon atoms.

8 . The method according to claim 1 , wherein the repeat units (R pm ) is represented by the formula

and the polymer (PP) comprises at least about 30 mole percent of the repeat units (R pm ).

9 . The method according to claim 1 , wherein the repeat units (R pp ) is represented by the formula:

and the polymer (PP) comprises at least about 40 mole percent of the repeat units (R pp ).

10 . The method according to claim 1 , wherein said method is for purifying non-drinkable water, said fluid is saline water or brackish water, said contaminant is the salts content dissolved into said fluid, and said membrane (PSP) is a multi-layered membrane comprising (I) a substrate layer, (II) an outer layer consisting of aromatic polyamides and (III) the layer (PSP), said layer (PSP) being interposed between said substrate layer and said outer layer.

11 . The method according to claim 1 , wherein said fluid containing at least one contaminant is a liquid phase or a gas phase.

12 . The method of claim 4 , wherein

T′ is selected from the group consisting of a bond, —CH 2 —, —C(O)—, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —C(═CCl 2 )—, —SO 2 —, —C (CH 3 )(CH 2 CH 2 COOH)—, and a group of formula:

and

T is selected from the group consisting of a bond, —CH 2 —, —C(O)—, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —C(═CCl 2 )—, —C(CH 3 )(CH 2 CH 2 COOH)—, and a group of formula:

and

T* is selected from the group consisting of a bond, —CH 2 —, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —C(═CCl 2 )—, —C(CH 3 )(CH 2 CH 2 COOH)—, and a group of formula:

13 . The method according to claim 1 , wherein the membrane (PSP) has a thickness between 15 μm and 200 μm.

14 . The method according to claim 1 , wherein the membrane (PSP) is characterized by a gravimetric porosity between 30 and 70%.

15 . The method according to claim 1 , wherein the membrane (PSP) has an average pore diameter ranging from 0.5 to 50 microns.

16 . The method according to claim 1 , wherein said membrane (PSP) is a multi-layered membrane comprising (I) a substrate layer, (II) an outer layer consisting of aromatic polyamides and (III) the layer (PSP), said layer (PSP) being interposed between said substrate layer and said outer layer.

17 . The method according to claim 16 , wherein the substrate is partially or fully interpenetrated with the at least one porous layer (layer (PSP)).