Membrane based on graft copolymers

Details Membrane based on graft copolymers Membrane based on graft copolymers

1994-12-20

1997-01-21

Spear, Frank

Liquid purification or separation

Filter

Supported, shaped or superimposed formed mediums

21050027, 210640, B01D 6902

Patent

active

055956580

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a membrane, especially a gas separation and pervaporation membrane based on graft copolymers.
The inventive membrane serves to separate gas mixtures and/or gas mixtures that are comprised of gases and vapors of organic solvents, and/or for pervaporation of aqueous/organic or organic/organic mixtures.
It is known to use for the separation of gas mixtures and vapors dense films of organic plastic materials which have the function of a membrane. In general, two types of membranes are known, i.e., a) integral asymmetric membranes and b) composite membranes.
Integral-asymmetric membranes are comprised of polymers or compatible polymer mixtures that are brought into the form of a self-carrying and supporting membrane by a phase inversion process. Accordingly, it is possible to achieve a very thin, stable separating layer of the polymer or the polymer mixture.
Composite membranes are comprised of thin films that are applied onto suitable support of materials of organic or inorganic substances. The support materials must be stable with respect to their shape and must allow for incorporation into modular systems. They must provide a high gas permeability. The supports can be selected in the form of polymer, organic materials, for example, from microporous polysulfone, polypropylene, polyvinylidene fluoride, or polyetherimide supports and in the form of inorganic materials as microporous glasses or microporous aluminum oxide. Both organic and inorganic support materials can be treated for smoothing the surface with a very thin film of an especially gas permeable polymer, for example, polydimethylsiloxane or polytrimethysilypropine.
The actual separating layer is applied to the surface of the treated or untreated microporous carrier whereby for the purpose of allowing great gas flows during the gas and gas/vapor separation it is desirable to apply a film of the separating polymer that is as thin as possible, for example, 0.5 to 3 .mu.m. With especially thin films free of micropores the gas flow through the separating layer however may be so great that the resistance of the support material has an effect on the separating efficiency of the membrane (I. Pinnau, J. G. Wijmans, I. Blume, T. Kuroda, K.-V. Peinemann, Gas Permeation through Composite Membranes, J. Membrane Sci., 37 (1988) 81 and U.S. Pat. No. 4,931,181). As a rule of thumb it can be presupposed that the effect of the support resistance on the selectivity is negative when the flow of gas through the separating layer is in the range of approximately 10% of the flow through the support. The efficiency of the entire membrane thus depends on the adjustment of the support material and the actual separating layer relative to one another. Not every support material, for example, PVDF supports, polysulfone supports, and especially hollow fiber membranes, can be manufactured so as to have the required gas flows in order to provide an optimal basis for very quick separating materials, as, for example, a PDMS membrane of 0.5 to 1 .mu.m thickness.
For a special application in the separation of vapors under high pressure, and especially in pervaporation of organic/organic or aqueous/organic solutions it is advantageous to use thicker polymer films of approximately 3 .mu.m up to 100 .mu.m. An increased feed pressure is, for example, advantageous for the membrane process of a gas/vapor separation for cleaning exhaust air because this achieves, on the one hand an increased flow through the membrane can be achieved and, on the other hand, the ratio of feed pressure to permeate pressure can be adjusted in a cost efficient manner.
The separating efficiency of a given polymer will decrease more or less with an unfavorable pressure ratio.
Known polymers that are suitable for membrane separating processes are the following:
In practice the elastomer polydimethylsiloxane (PDMS) has been proven to be the most used membrane material for the above described applications for problem solving.
The manufacture of composite membranes m

REFERENCES:
patent: 4245069 (1981-01-01), Covington
patent: 5444106 (1995-08-01), Zhou et al.

Affiliated with

Also associated with

Rating

Membrane based on graft copolymers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Membrane based on graft copolymers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Membrane based on graft copolymers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2322044