Reverse osmosis using a composite isocyanurate membrane
 A method for the selective separation of at least one water-soluble useful material from an aqueous solution by reverse osmosis is provided. The method comprises contacting the aqueous solution under pressure maintained above the osmotic pressure of the aqueous solution with a semipermeable composite membrane. The semipermeable composite membrane comprises a microporous substrate and a barrier layer having about 0.01 to about 0.1 micron thickness and composed of a cross-linked polymeric material having isocyanurate structures of Formula (I) formed on the microporous substrate: ##STR1## wherein each of R.sub.1, R.sub.2 and R.sub.3 is selected from the group consisting of hydrogen, a glycidyl group, and an alkyl radical containing from 2 to 5 carbon atoms, an alkyl radical carrying a functional hydroxyl group and an alkyl radical carrying a functional glycidyl group, with the proviso that at least two of R.sub.1, R.sub.2 and R.sub.3 are glycidyl groups, alkyl radicals carrying functional hydroxyl groups, alkyl radicals carrying glycidyl groups or a combination thereof. The cross-linked polymeric material has ether linkages, ester linkages or a combination thereof connecting the isocyanurate structures to each other. 
Toray Industries, Inc.
C C C C B C
C08G C08G C08G C08G B01D C08G
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Masaru Tetsuo Tetsuo
Kurihara Watanabe Inoue