Method of making a reverse osmosis semipermeable membrane
 A method of producing a semipermeable membrane comprising a polymeric material based upon a trisisocyanurate structure ##STR1## wherein, R.sub.1, R.sub.2 and R.sub.3 are hydrogen or alkyl radicals containing from 2 to 5 carbon atoms, and at least two of R.sub.1, R.sub.2 and R.sub.3 are alkyl radicals having hydroxyl or glycidyl groups. The membrane has high solute rejection, high flux, excellent high pressure resistance, and high temperature resistance and is a highly useful composite membrane for reverse osmosis. In the method, an aqueous solution containing, for example, a reaction product of Formula I is applied to the surface of a porous substrate and is heated at a temperature of about 100.degree. C. to 190.degree. C. to provide a cross-linked structure including a multiplicity of isocyanurate groups on the porous substrate. 
Toray Industries, Inc.
C C B C C C
C08G C08G B01D C08G C08G C08G
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Tetsuo Masaru Tetsuo
Inoue Kurihara Watanabe