Abstract: An aromatic polysulfone type resin hollow fiber membrane having a thickness of 100 to 600 .mu.m and a five-layer structure of an outer surface layer, an outer void layer, an intermediate layer, an inner void layer and an inner surface layer and wherein the inner and outer void layers are present in a thickness ratio of the inner void layer to the outer void layer of 1.5 to 0.6, the intermediate layer has a thickness of 5 to 70 .mu.m, and each of the outer and inner surface layers has an extremely small thickness. The hollow fiber membrane of the kind is excellent in heat resistance, acid resistance, alkali resistance, chemicals resistance and has an improved mechanical strength as well as a high water permeability.

Abstract: There is disclosed a composite membrane comprising [A] a polysulfone type porous membrane capable of rejecting 90% or more of dextran molecules having a weight average molecular weight of 70,000 and [B] a specific styrene type resin coated on at least one side of the polysulfone type porous membrane in a thickness of 5 .mu.m or less and in an amount of 1.times.10.sup.-7 g/cm.sup.2 of the polysulfone type porous membrane, the styrene type resin being selected from the group consisting of (I) a specific styrene type linear polymer having a weight average molecular weight of 1.times.10.sup.-5 or more, (II) a specific blend polymer prepared by blending at least two different styrene type linear polymers each as defined above and (III) a specific crosslinked polymer selected from the group consisting of (i) a crosslinked polymer prepared by crosslinking a styrene type linear polymer having a weight average molecular weight of 1.times.10.sup.

Abstract: An aromatic polysulfone type resin hollow fiber membrane having a thickness of less than 100 .mu.m and a three-layer structure of inner and outer surface skin layers and a void layer disposed therebetween and connected thereto. The hollow fiber membrane of the kind has an improved burst strength, while exhibiting an extremely excellent water permeability. Such a hollow fiber membrane can be produced by a process which comprises extruding a spinning solution of an aromatic polysulfone type resin in an organic polar solvent for said resin, said solution containing a glycol and having a resin concentration of from 10 to 35% by weight, from an annular spinning nozzle of which the orifice width is 10 to 110 .mu.m while simultaneously injecting an internal coagulating liquid into the annular spinning nozzle at an inside bore thereof, thereby to obtain an extrudate in the form of a hollow fiber, and introducing said extrudate into an external coagulating liquid.

Abstract: A screen type hollow filament microfilter made of a polyvinylidene fluoride type resin and having a layer structure of two kinds of layers with the support layer and the internal and external skin layers having an easily-controllable and wide average effective pore diameter of 0.05 to 1.0 .mu.m, characterized by having a high selectivity in permeation, a high permeability, a high porosity, an excellent mechanical strength and an excellent chemical resistance and an excellent inertness to living bodies. The microfilter, which has a number of excellent performances, can be produced by extruding a spinning solution comprising a polyvinylidene fluoride type resin, a solvent therefor and at least one kind of surfactant from an annular hollow filament spinning orifice and coagulating the extrudate by using coagulating liquids.

Abstract: A specific porous membrane is found to be extremely useful for permeation-separation of an oil from an oil-containing emulsion. By contacting a stable oil-containing emulsion of either water-in-oil type or oil-in-water type with the surface of a specific porous membrane having at its surface a critical surface tension of less than 35 dynes/cm to not less than 20 dynes/cm and having an average pore diameter of 0.03 .mu.m to 5 .mu.m, a pore radius distribution of not more than 1.5 and a porosity of 1 to 85%, only the oil can be permeation-separated, without permeation of the liquid immiscible with the oil, with high selectivity and high oil permeation.