Crosslinked hollow-fibre membranes and new process for manufacturing the same

1. A process for manufacturing a hollow-fibre membrane, comprising:

(a) spinning a hollow-fibre membrane by:

(a1) extruding through an orifice of a hollow-fibre die a phase (a1) composition comprising:

(a1.i) a polymer selected from the group consisting of: polyimides, copolyimides; block-copolyimides; polyetherimides; polyamidoimides; and mixtures and blends thereof; and

(a1.ii) a solvent or a solvent mixture for said polymer (a1.i);

(a2) co-extruding through a central orifice of the hollow-fibre die and/or through an outer orifice of a hollow-fibre die a phase (a2) composition comprising:

(a2.i) an amine based crosslinker, with at least two amino groups;

(a2.ii) a non-solvent or a non-solvent mixture for the polymer (a1.i);

(b) passing the hollow-fibre membrane through a coagulation bath;

(c) drying the hollow-fibre membrane to an overall water and/or residual solvent content of from 0% to 5% by weight;

(d) thermally treating the hollow-fibre membrane at an annealing temperature of 150 to 280° C.; wherein annealing takes place in a surrounding atmosphere with less than 0.5% oxygen by volume.

2. The process of claim 1 , wherein the amine based crosslinker (a2.i) is an aliphatic or aromatic amine.

3. The process of claim 1 , wherein the hollow-fibre die is a double-orifice spinneret, a triple-orifice spinneret or a quadruple-orifice spinneret.

4. The process of claim 3 , wherein the die is a spinneret with annular orifices.

5. The process of claim 1 , wherein the phase (a1) composition comprises in sum 15% to 35% by weight of the polymer (a1.i) based on the total weight of the phase (a1) composition.

6. The process of claim 1 , wherein the phase (a2) composition comprises in sum 0.1% to 30% by weight of an amine based crosslinker (a2.i) with at least two amino groups based on the total weight of the composition (a2).

7. The process of claim 1 , wherein the amine based crosslinker (a2.i) comprises an octanol-water-partition coefficient log P equal to or higher than −0.5.

8. The process of claim 2 , wherein the aliphatic and/or aromatic amine with at least two amino groups (a2.i), is selected from the group consisting of:

substituted or unsubstituted, linear or branched aliphatic amines with 6 to 30 carbon atoms, comprising:

a carbon chain with 5 to 24 carbon atoms; and

2 to 5 amino groups;

substituted or unsubstituted cyclic aliphatic amines with 6 to 24 carbon atoms, optionally comprising heteroatoms in alkyl chains or as a linkage between aliphatic rings;

substituted or unsubstituted aromatic or alkyl aromatic amines with 6 to 24 carbon atoms, optionally comprising heteroatoms; and mixtures thereof.

9. The process of claim 8 , wherein the aliphatic and/or aromatic amine with at least two amino groups (a2.i), is selected from the group consisting of: 1,6-Hexamethylene-diamine; 1,7-Heptamethylenediamine; 1,8-Octamethylenediamine; 1,9-Nonamethylene diamine; 1,10-Decamethylenediamine; 1,11-Undecamethylenediamine; 1,12-Dodecamethylenediamine; 2,2,4-trimethylhexan-1,6-diamine; 2,4,4-trimethylhexan-1,6-diamine; 2-methylpentanediamine; isophoronediamine (3,5,5-trimethyl-3-aminomethyl-cyclohexylamine); 4,4′-diaminodicyclohexylmethane; 2,4′-diaminodicyclohexylmethane; 2,2′-diaminodicyclohexylmethane alone or in mixtures of isomers; 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane; N-cyclohexyl-1,3-propanediamine; 1,2-diaminocyclohexane; TCD-diamine (3(4),8(9) bis(aminomethyl)-tricyclo[5.2.1.0 2,6 ]decane); xylylenediamines; aromatic amines; o-, m- or p-phenylenediamines; trimethylphenylenediamines; 4,4′-diaminodiphenylmethane; and mixtures thereof.

10. The process of claim 2 , wherein the aliphatic and/or aromatic amine with at least two amino groups (a2.i), is selected from the group consisting of: aliphatic amines; 1,6-Hexamethylenediamine; 1,7-Heptamethylenediamine; 1,8-Octamethylenediamine; 1,9-Nonamethylenediamine; 2,2,4-trimethylhexan-1,6-diamine; 2,4,4-trimethylhexan-1,6-diamine; Decane-1,10-diamine; Dodecane 1,12-diamine; 2-methylpentanediamine; 1,3-Cyclohexanebis-(methylamine); and mixtures thereof.

11. The process of claim 1 , wherein the solvent (a1.ii) for the polymer (a1.i) comprises a polar aprotic solvent.

12. The process of claim 1 , wherein the solvent (a1.ii) for the polymer (a1.i) is selected from the group consisting of: dimethylsulfoxide; dimethylformamide; dimethylacetamide; N-methylpyrrolidone; N-ethylpyrrolidone; sulpholane; tetrahydrofuran; and mixtures thereof.

13. The process of claim 12 , wherein the non-solvent (a2.ii) comprises a protic solvent.

14. The process of claim 13 , wherein the non-solvent (a2.ii) for the polymer (a1.i) is selected from the group consisting of: water; C1-C6 alkanols; C2-C6 alkanediols; C3-C12 alkanetriols; C4-C20 polyols; and hydrophilic polymers or copolymers.

15. The process of claim 1 , wherein thermal treatment of the hollow-fibre membrane in step d) is carried out at an annealing temperature of 180 to 230° C.

16. The process of claim 1 , wherein,

in step (a1) the phase (a1) composition consists of:

(a1.i) a polymer selected from the group consisting of: polyimides, copolyimides; block-copolyimides; polyetherimides; polyamidoimides; and

mixtures and blends thereof; and

(a1.ii) a solvent or a solvent mixture for said polymer (a1.i);

in step (a2) the phase (a2) composition consists of:

(a2.i) an amine based crosslinker, with at least two amino groups;

(a2.ii) a non-solvent or a non-solvent mixture for the polymer (a1.i).

17. The process of claim 1 , wherein, in step d), annealing takes place for 15-300 minutes and, after heating ends, the hollow fibre membrane is actively cooled.

18. The process of claim 17 , wherein annealing takes place in a surrounding atmosphere with less than 0.01% oxygen by volume.