Liquid purification or separation – Filter – Material
Patent
1989-09-07
1991-09-24
Woo, Jay H.
Liquid purification or separation
Filter
Material
210490, 210654, 427243, 427244, 427245, 264183, 264347, B01D 6100
Patent
active
050511785
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process of producing a composite semipermeable membrane which is useful for selective separation of liquid mixtures, especially for desalination of brackish and sea water.
BACKGROUND ART
Composite semipermeable membranes prepared by covering a microporous substrate with a ultra-thin membrane of a crosslinked polyamide obtained by interfacial polycondensation reaction between a polyfunctional aromatic amine and a polyfunctional acid halide are now drawing attention as reverse osmosis membranes with high permeability and high separation selectivity. Preparation of the composite membrane by the interfacial polycondensation reaction between the polyfunctional aromatic amine and the polyfunctional acid halide is disclosed in, for example, U.S. Pat. Nos. 4,277,344, 4,520,044, 4,529,646, 4,626,468, 4,643,829, 4,661,254, 4,749,488 and 4,761,234.
On the other hand, a composite semipermeable membrane prepared by laminating a ultra-thin membrane of a polyamide obtained by interfacial polycondensation reaction between ethylenediamine and a polyfunctional acid halide on a microporous substrate is known as a reverse osmosis membrane with excellent oxidation resistance and high separation selectivity, which semipermeable membrane is disclosed in, for example, European Patent Publication No. 0,085,111.
Although the composite semipermeable membrane prepared by covering a microporous substrate with an ultra-thin membrane of a crosslinked polyamide obtained by interfacial polycondensation reaction between a polyfunctional aromatic amine and a polyfunctional acid halide has excellent permeability and separation selectivity, it does not have a satisfactory oxidation resistance which is required for a practical reverse osmosis membrane. That is, in a practical reverse osmosis process, the system is usually washed with an oxidant for removing organic substances fixed in the system, so that the reverse osmosis membrane is desired to have resistance against the oxidant, expecially against free chlorine.
On the other hand, although the composite semipermeable membrane prepared by laminating an ultra-thin membrane of a polyamide obtained by interfacial polycondensation reaction between ethylenediamine and a polyfunctional acid halide on a microporous substrate has excellent oxidation resistance and separation selectivity, it does not have the satisfactory permeability required for a practical reverse osmosis membrane. The permeability is one of the most important factors for the economic efficiency of a practical reverse osmosis process. Thus, a reverse osmosis membrane which has both high permeability and high oxidation resistance is desired.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a process of producing a composite semipermeable membrane which has both high oxidation resistance and high permeability, thereby overcoming the above-mentioned problems in the prior art.
That is, the present invention provides a process of producing a composite semipermeable membrane comprising the step of forming on a microporous substrate an ultra-thin membrane containing as a major component a crosslinked polyamide obtained by interfacial polycondensation reaction between a polyfunctional aromatic amine having not less than 2 amino groups in the molecule and a polyfunctional acid halide having not less than 2 halogenated carbonyl groups in the molecule, to form a composite semipermeable membrane. The polycondensation reaction is performed in the presence of a copolymerization component comprising. at least one member selected from the group consisting of 1,3,5-trihydroxybenzene, 1,3-dihydroxybenzene and an alkyldiamine of the formula (1): ##STR1## wherein R.sup.1 and R.sup.2 independently represent C.sub.1 -C.sub.3 alkyl, C.sub.6 phenyl or hydrogen, R.sup.3 represents C.sub.1 -C.sub.7 straight chain alkyl group which may have one or more side chains or C.sub.3 - C.sub.7 cycloalkyl group which may have one or more side chains).
The latter copolymerization is added
REFERENCES:
patent: 4626468 (1986-12-01), Sundet
patent: 4643829 (1987-02-01), Sundet
patent: 4661254 (1987-04-01), Zupancic
patent: 4749488 (1988-06-01), Arthur
patent: 4761234 (1988-08-01), Uemura
Fujimaki Hideo
Ikeda Toshihiro
Uemura Tadahiro
Durkin II Jeremiah F.
Miller Austin R.
Toray Industries Inc.
Woo Jay H.
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