Daicel Chemical Industries, Ltd.

Kengo Magara

Hitoshi Tsugaya

Yasushi Maeda

A separatory membrane is provided which has a sufficient durability and shows a high rate of permeation therethrough and a high separation factor to a variety of organic substances and a wide range of concentration thereof in mutual separation of organic substances and separation of a water/organic substance mixture by pervaporation, vapor permeation or perstraction. The separatory membrane shows the performance that water permeates selectively through the membrane while satisfying such conditions that the product (QL) of the rate Q (kg/m.sup.2 .multidot.hr) of permeation and the thickness L (.mu.m) of the membrane is at least 0.5 kg.multidot..mu.m/m.sup.2 .multidot.hr and that the separation factor .alpha..gtoreq.10 and log.alpha..gtoreq.-1.77.times.log(QL)+2.77 when the pervaporation performance of a 5-30 .mu.m-thick dense uniform membrane is evaluated using as a liquid feed, an 80 wt. % aqueous solution of acetic acid at a temperature of 70.degree. C., and comprises, as the membrane material, a polyacrylonitrile copolymer constituted of 90 to 97 mol % of acrylonitrile monomer units and a specific comonomer(s).

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Hyogo, Japan

Kengo Magara