POLYIMIDE MEMBRANES MADE OF POLYMERIZATION SOLUTIONS

• US 20120123079A1
• Filed: 07/22/2010
• Published: 05/17/2012
• Est. Priority Date: 07/23/2009
• Status: Abandoned Application

• Current Assignee: Evonik Fibres Gmbh (Rag-Stiftung)
• Original Assignee: Evonik Fibres Gmbh (Rag-Stiftung)
• Inventors: Ungerank, Markus, Baumgarten, Goetz
• Application Number:
  US13/384,685
• Publication Number:
  US 20120123079A1
• Time in Patent Office: Days
• US Class Current: 528/67
• CPC Class Codes: B01D 2323/18 Pore-control agents or pore formers
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/00091 by evaporation
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/0013 Casting processes
• CPC Class Codes: B01D 69/087 Details relating to the spinning process
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: C08G 73/1042 Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
• CPC Class Codes: C08G 73/1067 Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
• CPC Class Codes: C08L 79/08 Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

The invention relates to polyimide membranes and to a phase inversion method for the production thereof. The polyimide membranes can be used to separate different gas mixtures.

Claims

1. A process for producing a polyimide membrane, the process comprising:

(a) forming a casting solution comprising a polyimide; and

(b) forming a polyimide membrane from the casting solution,

by a phase inversion process,

wherein the polyimide has not been isolated as a solid material and then redissolved prior to forming said casting solution.

2. The process of claim 1, further comprising forming the polyimide from an aromatic dianhydride,

an aromatic diisocyanate,

an aprotic dipolar solvent, or mixtures thereof.

3. The process of claim 1, wherein

the polyimide is a polyimide of formula (I):

4. The process of claim 1, wherein the casting solution further comprises a water-soluble additive.

5. The process of claim 1, wherein the forming (b) of the polyimide membrane comprises coating a backing fleece with the casting solution.

6. The process of claim 1, wherein the polyimide membrane is crosslinked with at least one aliphatic diamine or polyethyleneimine.

7. The process of claim 1, wherein the forming (b) of the polyimide membrane comprises forming an integrally asymmetrically hollow fiber membrane by spinning a hollow fiber with a two-material die from the casting solution and a bore solution in a continuous process.

8. The process of claim 7, wherein the forming (b) satisfies at least one condition selected from the group consisting of:

the bore solution comprises a mixture of water and an alcohol with at least one selected from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, N-ethylpyrrolidinone, sulfolane, and dimethyl sulfoxide;

the two-material die is at a distance of 1 to 60 cm from a spin bath of water into which the hollow fiber is spun and an integrally asymmetrical hollow fiber membrane is formed by precipitating the polymide;

during the spinning a hollow thread is subjected to a flow of a dry thermostated stream of nitrogen or air before entry into a spin bath in order to adjust separation properties of the polyimide membrane;

the polyimide is crosslinked with at least one aliphatic diamine or polyethyleneimine;

a crosslinking of the polyimide occurs by dipping the polyimide into a solution of diamine in water or at least one alcohol;

a crosslinking of the polyimide occurs at temperatures between 0 and 90°

C.;

a crosslinking time for a crosslinking of the polyimide is between 10 seconds and 16 hours; and

a concentration of diamine in a crosslinking of the polyimide is between 0.01% by weight and 50% by weight.

9. A polyimide membrane obtained by the process of claim 1.

10. The polyimide membrane of claim 9, comprising a polyimide having an Mp>

100 000 g·

mol<sup>−

1</sup> and a PDI in the range from 1.7 to 2.3.

11. The polyimide membrane of claim 9, wherein:

the polyimide is a polyimide of formula (II);

12. The polyimide membrane of claim 9, in the form of:

a micro-, ultra- or nanofiltration membrane suitable for separating homogeneous dissolved or particulate products from organic solvents or from water;

or

a no-pore membrane suitable for separation of gases.

13. The polyimide membrane of claim 9, in the form of:

an integrally asymmetrical flat sheet membrane on a backing fleece;

or

an integrally asymmetrical hollow fiber membrane.

14. The polyimide membrane of claim 13, wherein the polyimide membrane is an integrally asymmetrical hollow fiber membrane suitable for separating a wide variety of gas mixtures.

16. The process of claim 4, wherein the water-soluble additive is at least one selected from the group consisting of a water-miscible solvent, a non-solvent, and a pore-former.

17. The process of claim 5, further comprising vaporizing some solvent of the casting solution with a dry thermostated stream of nitrogen or air, after the coating of the backing fleece with the casting solution, to adjust separation limits of the polyimide membrane.

18. The process of claim 6, satisfying at least one condition selected from the group consisting of:

the polyimide membrane is crosslinked with at least one aliphatic diamine selected from the group consisting of diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminooctane, diaminodecane, diaminododecane, bis-4,4′

-(aminomethyl)benzene, a oligoethyleneimine, and a polyethyleneimine;

the polyimide membrane is crosslinked by dipping into a solution of diamine in water or at least one alcohol;

the polyimide membrane is crosslinked at temperatures between 0 and 90°

C.;

a crosslinking time is between 10 seconds and 16 hours; and

a concentration of diamine is between 0.01% by weight and 50% by weight.

19. The polyimide membrane of claim 13, wherein the polyimide membrane is an integrally asymmetrical flat sheet membrane on a backing fleece of polyphenylene sulfide, polyethylene terephthalate or polypropylene.

20. The polyimide membrane of claim 14, wherein the integrally asymmetrical hollow fiber membrane is suitable for separating at least one selected from the group consisting of:

methane and carbon dioxide;

oxygen and nitrogen;

hydrogen and process gases; and

water vapor and a gas or a mixture of gases.

15. A casting solution comprising a polyimide, wherein the polyimide is not isolated as a solid material and then redissolved.