Development of Dry-RO (Trade Mark) Membranes from Sulfonated Cellulose Acetates and Quaternized Cellulose Acetate Carbamates.

摘要

The program treated two aspects of ionogenic cellulosic reverse osmosis membranes: (1) The feasibility of incorporating anionic (sulfonate groups) charges into cellulose acetate (CA);and (2) the feasibility of the covalent attachment of quaternary ammonium groups via carbamate -rather than ester -linkages. The synthesis of anionic cellulose triesters (ACTEs), i.e. sulfonated CAs reacted the free OH groups of CA with o-sulfobenzoic anhydride. Precipitation of this polymer into aqueous sodium bicarbonate produced the sodium salt. The addition of the anhydride to CA was found to be nearly quantitative. Permeability increased with increasing ion exchange capacity (I.E.C.). The synthesis of aliphatic sulfonates was effected via sodium bisulfite addition to CA mixed esters containing terminal olefinic groups, e.g. CA undecylenate. Membranes of the sodium salt of CA 11-sulfoundecanoate were the best developed on the ACTE program. ACTE development may be the preferred path for future cellulosic RO membrane development. The second part of the program resulted in the simplified approach of in situ formation of CA carbamates. This revolutionary approach consisted of preparing blocked isocyanate monomers bearing quaternary ammonium groups and the inclusion of these monomers in ordinary CA casting solutions such that they wound up incorporated within the final membrane.