SEPARATION MEMBRANE

PURPOSE:To improve durability and to increase the amt. of liquid transmitting the membrane by forming the separation film in a manner that a porous polymer film of an asymmetric structure having a dense thin layer on at least one surface thereof is used and that polyamines are made to exist by acid-amide coupling into the dense thin layer. CONSTITUTION:A stable separation membrane which is made more dense and functional is obtained by introducing functional groups from a reaction reagent to polyamines which are distributed on the dense thin layer of the porous polymer film or by effecting the crosslinking reaction of the polyamines. The polymer material for the porous polymer film is, for example, condensation polymers having aromatic rings such as polysulfon, polyethersulfon, etc. These polymers are preferable and well-known as engineering plastics. In the reaction process of forming the acid-amide coupling, a deoxidizer such as liquid ion exchanger, ion-exchange resin, tertiary amine which does not react with acid-halide group, and quaternary ammonium hydroxide may be used in the reaction bath to absorb acid produced in the reaction.