Dryable (co)polyacrylonitrile membrane with reversible properties - by water immersion, for reverse osmosis and ultrafiltration

摘要

A semipermeable membrane which can be dried is prepd. by (a) forming a 15-30 pref. 15-25 wt.% soln. of an acrylonitrile polymer or copolymer contg. 65, pref. 85-99 wt.%, acrylonitrile, in pref. dimethyl acetamide (DMA) DMF and/or DMSO, (b) evenly spreading the soln. according to desired shape and immersing it in a non-solvent medium (pref. water or a mixt. of water and DMA, DMF and/or DMSO), to eliminate the solvent and form a membrane, (c) heating the membrane in a moist atmosphere at 60-90 degrees C and (d) drying the membrane of a temp. lower than used in (c), thus forming a dried semipermeable membrane with open pores of dia. 0.5 mu and porosity 0.40-0.7. The membrane is used in reverse osmosis and ultrafiltration processes. The membrane after drying can be made to recover its semipermeability properties by immersion in water.