US 4,061,821 A · Semipermeable composite membranes

Abstract

A semipermeable composite membrane which shows only a small reduction of water permeability even when it is subjected to one time hot water treatment or drying treatment is provided according to the method of the present invention. Said semipermeable composite membrane consists of a porous substance and a reinforcing material embedded therein. Said porous substance has a porous region of network structure at least in one part thereof and numbers of voids in said porous region. Said reinforcing material is a fabric in case of flat type membrane or a braid having a central hollow portion in case of hollow fiber type membrane which is embedded in the wall of the membrane. Said method comprises impregnating said reinforcing material with a polymer solution and treating the impregnated reinforcing material with a coagulating liquid.

Claims9

Dependent claims

A semipermeable composite membrane consisting of a porous substance and a reinforcing material made of fibrous material embedded in the wall of the porous substance, at least one part of said porous substance forming a porous region of a network structure having pore sizes in the range from 500A to 5.mu.;

said porous region containing a number of voids having diameters of 10.mu. or greater;
and the ratio of water permeability of said membrane after one time treatment with hot water at 80.degree. C or after drying at 20.degree. C to the respective water permeability before said treatment being 0.3 or higher.

Dependencies are inferred from the claim text.

Semipermeable composite membranes

Life of this patent

Semipermeable composite membranes

Life of this patent

Abstract

Claims9