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Cross-linked polyimide membranes

A polyimide membrane, polyimide technology, applied in the field of solvent stability, can solve problems such as decreased affinity of permeable compounds

Inactive Publication Date: 2010-03-24
EVONIK FIBERS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is known that many chemical (crosslinking reactions, etc.) or physical (plasma treatment, etc.) treatments break down the polymer chains (see Example 6), thus destroying the mechanical stability of the membrane and / or increasing the pore size of the membrane, or Modification of the membrane surface such that the affinity for permeating compounds and thus their permeation is significantly reduced

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] An 18% by weight solution of matrimid 9725 polyimide (Huntsman) was made in NMP and THF (2:1 ratio) by stirring overnight. The polymer solution was cast on a polypropylene nonwoven support by an automatic casting device set at a gap of 250 microns. The resulting film was immersed in a deionized water bath after 30 seconds of evaporation.

[0033] Several aliquots of the resulting membrane were dipped in a methanolic solution of p-xylylenediamine for crosslinking. After 5, 60 and 120 minutes, the membrane pieces were removed and rinsed with methanol to remove all reactants. The membranes were then dipped in IPA until used for dipping experiments. Several cross-linked membranes were soaked in DMSO for a few days, after which they were soaked in IPA until they were used for filtration.

[0034] Filtration with Rose Bengal in IPA (35 μM) was performed on the cross-linked membrane in a stainless steel dead-end filter unit pressurized to 6 bar with nitrogen before and afte...

Embodiment 2

[0037] Membranes were prepared and crosslinked as in Example 1. Soak the crosslinked membrane pieces in NMP for several days. Uncrosslinked membrane pieces were dipped in NMP where they dissolved after a few hours. Filtration was performed as in Example 1. The results showed that the membranes crosslinked for 60 min or longer maintained their excellent properties in IPA after immersion in NMP.

[0038]

[0039] The first results demonstrate the non-obvious success of the chemical modification of the membrane.

Embodiment 3

[0041] Membranes were prepared and crosslinked as in Example 1, but NMP-exchanged clarified solution (NMP-CS) was added as an additional component to the polymer casting solution. This NMP-CS emulsifies the polymer stock solution before casting, which is further processed as in Example 1. During this modified phase inversion process known as "emulsion polymer dope solidification by phase inversion" or "SEPPI" (Gevers, 2006), membranes with uniform spherical pores that are more resistant to high pressure compression are produced. The membrane was further processed as in Example 1. Dip the cross-linked membrane block in DMF. Uncrosslinked blocks soaked in DMF were completely dissolved after a few hours. Filtration was performed as in Example 1.

[0042] The results indicated that a crosslinking treatment of 60 min or longer was sufficient to fabricate membranes stable in DMF, which retained their excellent properties in IPA after immersion in DMF.

[0043]

[0044] The fi...

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Abstract

The present invention provides a method for improving the performance of polyimide membranes as used in solvent-resistant nanofiltration. More specifically the method of the present invention allows to imrove the solvent stability of the polyimide membranes to solvents or solvent mixtures that would dissolve polyimide under the conditions applied during the filtration, such as dimethylforrnamide (DMF), N-methylpyrrolidinone (NMP), dimethylacetamide (DMAC), tetrahydrofuran (THF), y-butyrolacton (GBL), dimethylsulphoxide (DMSO) and chlorinated solvents.

Description

technical field [0001] This invention relates to improving the performance of polyimide membranes used in solvent resistant nanofiltration, and more particularly to extending the resistance of the polyimide membranes to solvents or solvent mixtures which dissolve the polyimide under the conditions used in the filtration process. Solvent stability. Background technique [0002] Nanofiltration is a pressure-driven separation method. It involves the separation of two or more components on a membrane by means of a pressure gradient created by applying pressure (gas pressure or mechanical pressure) to the feed side of the membrane. The pressure-driven membrane method can be divided into 4 categories according to the applied pressure, the typical values ​​of which are listed in Table 1 (Mulder, 1996). When referring specifically to solvent applications, the term "solvent resistant nanofiltration (SRNF)" also includes the high pressure side of reverse osmosis and ultrafiltration....

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D71/62B01D53/22B01D67/00B01D61/02
CPCB01D53/228B01D67/0088B01D2325/34B01D71/64B01D61/027B01D2325/30B01D2323/30B01D67/0095B01D67/0093
Inventor P·范德桑德K·范赫克I·范凯莱科姆
Owner EVONIK FIBERS
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