Liquid purification or separation – Filter – Material
Patent
1996-02-15
1998-05-05
Fortuna, Ana
Liquid purification or separation
Filter
Material
21050038, 21050041, 21050043, 210490, 2041823, 2041824, 521 27, 427244, B01D 3900
Patent
active
057469172
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention refers to a new ion exchange membrane and a process for producing the same.
Ion exchange membranes are of importance as indispensable diaphragms for the electrodialysis and the electrolysis, and alternatingly used in form of cation and anion exchange membranes between a pair of electrodes for subdividing the electrolyte solutions in different process streams.
Both types of ion exchange membranes facilitate the transport of one of the respective types of ions, i.e. either cations or anions. Together, a pair of membranes thus effects the transfer of salt.
DESCRIPTION OF THE PRIOR ART
To date, anion exchange membranes are mainly made on the basis of copolymers of styrene. Primarily, styrene and divinyl benzene/ethyl vinyl benzene are polymerized together with inert polymers (Paste-Method) and subsequently functionalized through chloromethylation and following amination.
Apart from styrene as a matrix polymer, polysulfones, polyether sulfones or poly (vinylpyridine) derivatives can also be used.
This method effects formation of film and functionalization of the film in two separate steps. This significantly complicates a development of membranes with special properties. Often, the use of e.g. softeners must be added as filler material for the not yet functionalized film.
Besides this Paste-method (Mizutani et al.; Bull. Chem. Soc. Japan, 38(5) p. 689-94), polymers that contain an active halogen can be formed in one method step into a film (membrane formation step), at the same time functionalized, and a crosslinking can be effected that corresponds to the degree of crosslinking of the product (Desalination, 79 (1990) 125-144). Such a membrane must be swollen before being used in the application medium. This process requires, however, a chloromethylated polystyrene which is not available on a large scale and necessitates the use of toxic (chloromethyl) methyl ether. The use of the aromatic matrix polymer results also in membranes which are easily contaminated as the aromatic matrix has a tendency to pick up dirt. This is one of the greatest unsolved problems of electrodialysis.
Membranes were also made through crosslinking of polyethylene imine with epichlorohydrin oligomerics (An. Quim., Ser. B 1982, 78(2), 221-3; CA 98:75956y). The resulting membranes have the great drawback of being weakly basic (See: Advances in polymer science 70 p. 92) and therefore unsuitable for use in neutral solution. They have a statistical distribution of secondary, tertiary and quaternary nitrogen atoms. The reproduction of such membranes becomes therefore difficult; the degree of swelling of the membranes is pH dependent.
SUMMARY OF THE INVENTION
It is the subject matter of this invention to provide a strong alkaline anion exchange membrane which membrane forming step, without any successive derivativation reactions. blockers, permeable membranes for great anions, alkaline stable anion exchange membranes).
It was found that the highly aminated products obtained by the reaction of poly (epichlorohydrin), poly (epichlorohydrin-co-ethylenoxide) or similar polymers with tertiary amines, preferably 1,4-diazabicyclo-(2,2,2)-octane, in dipolar aprotic solvents can be converted to mechanically self-supporting membranes with suitable inert polymers, to meet the afore-mentioned conditions. These membranes can particularly be made as acid blocker membranes for the electrodialysis of acids with high current output, or as membranes for transport of particular large anions.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a schematic cross section through the experimental structure for making the anion exchange membranes. The closed reaction vessel 4 is installed in a conditioned room 1 (drying cabinet). Its size is suited to the size of the membrane surface 2 which is placed upon a flat surface 3 (e.g. a glass plate).
FIG. 2 shows a schematical arrangement to electroosmotically pump (EOP) acids. The minimum configuration is realized comprising a repeating unit, with the diluate compartment being iden
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patent: B433930 (1976-03-01), Gregor
patent: 3454490 (1969-07-01), Wallace
patent: 3700623 (1972-10-01), Keim
patent: 4116889 (1978-09-01), Chlanda et al.
patent: 5045171 (1991-09-01), MacDonald
patent: 5085784 (1992-02-01), Ostreicher
Feiereisen Henry M.
Fortuna Ana
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