[Problem] Provided is a semipermeable membrane that achieves chemical resistance (chlorine resistance, acid resistance, alkali resistance), membrane performance, and membrane strength by sulfonating a polyphenylene-based semipermeable membrane base material under specific conditions. [Solution] A polyphenylene-based semipermeable membrane that is composed of a material containing a polyphenylene-based resin, wherein the semipermeable membrane has a first surface of which at least a portion is sulfonated, and wherein, when concentration distribution of elemental sulfur derived from a sulfonic acid group is measured by elemental analysis in a cross section in a thickness direction of the semipermeable membrane, a ratio of a sulfonated layer obtained by the following expression is 50% or less: Ratio of Sulfonated Layer (%)=Sulfonated Layer Thickness/(Sulfonated Layer Thickness+Non-Sulfonated Layer Thickness)×100.

A composite semipermeable membrane 12 of the present invention includes a porous support membrane 12a and a skin layer 12b supported by the porous support membrane 12a. The membrane surface of the composite semipermeable membrane 12 has an elastic modulus of 250 MPa or more and 500 MPa or less as calculated by force curve measurement using AFM in water. A spiral membrane element 20 of the present invention includes the composite semipermeable membrane 12 of the present invention. A water treatment system 100 of the present invention includes the spiral membrane element 20 of the present invention.

The present invention relates to a separation membrane including an organic polymer resin, in which a volume V1 of fine pores having a pore diameter of 100 nm or more is 0.3 cm.sup.3/g or more and 0.5 cm.sup.3/g or less, a volume V2 of fine pores having a pore diameter of less than 100 nm is 0.02 cm.sup.3/g or more and less than 0.1 cm.sup.3/g, and a ratio V1/V2 of the fine pore volume V1 to the fine pore volume V2 is 3 or more and 60 or less.

One aspect of the present invention provides a method of manufacturing a separator including: (a) obtaining a laminate by laminating a first porous support and a second porous support; (b) forming a functional layer by applying a composition including a binder and a solvent on both sides of the laminate and drying the composition; and (c) dividing the laminate into two separators along an interface formed by the lamination, and a separator manufactured using the method.

Disclosed are copolymers suitable for hydrophilically modifying the surface of porous fluoropolymer supports, for example, a copolymer of the formula (I) or (II): ##STR00001##
wherein Rf, Rh, Ra, Y, m, and n are as described herein. Also disclosed are a method of preparing the copolymers, a method of hydrophilically modifying porous fluoropolymer supports, hydrophilic fluoropolymer porous membranes prepared from the polymers, and a method of filtering fluids through the porous membranes.

Hydrophilic flat-sheet membrane based on a hydrophobic first polymer from the group consisting of aromatic sulfone polymers and a hydrophilic second polymer, wherein the membrane has a thickness in the range between 30 and 200 μm, a first and a second surface and a supporting layer having a three-dimensional sponge-like network structure, wherein the supporting layer has a first cover layer on the side thereof facing the first surface and a second cover layer on the side thereof facing the second surface, which cover layers are formed integrally with the supporting layer, and wherein the first and second surfaces have approximately oval or circular openings which penetrate the first and second cover layers, respectively, and are connected to the supporting layer, wherein the average diameter of the openings in the surfaces differ by a factor of less than 2, wherein the three-dimensional network structure of the supporting layer is made up of thick branches and a continuous pore system, and the predominant proportion of the branches have a diameter of at least 0.5 μm at the thinnest point thereof and wherein the pores in the supporting layer are larger than the openings in the surfaces.

There is provided a semi-crystalline polymer membrane, the membrane being a single-layer membrane and su-perwettable without provision of a coating or additives. There is also provided a method of forming the membrane comprising: depositing a solution on a substrate surface, the solution comprising a semi-crystalline polymer to form a nascent membrane; spraying a fluid on the nascent membrane; and immersing the nascent membrane in a non-solvent to form the semi-crystalline polymer membrane. In preferred embodiments, the fluid sprayed on the nascent membrane is selected from compressed air, water, a mixture of ethanol and water, or a solid suspension of ethanol/water/sodium chloride.

An object of the present invention is to provide a porous hollow-fiber membrane having high strength while maintaining high pure-water permeation performance. A porous hollow-fiber membrane of the present invention is a porous hollow-fiber membrane including a fluororesin-based polymer, in which the porous hollow-fiber membrane has a columnar texture oriented in a longitudinal direction of the porous hollow-fiber membrane, and a molecular chain of the fluororesin-based polymer is oriented in the longitudinal direction of the porous hollow-fiber membrane.

A cation-exchange membrane using a polyolefin-based substrate with reduced swelling of an ion-exchange resin and a low electrical resistance is provided. The cation-exchange membrane of the present invention includes a substrate made of polyolefin-based woven fabric, and a sulfonic acid group-containing cation-exchange resin. A portion of the cation-exchange membrane other than the substrate has 23 mass % or more to 35 mass % or less of polyvinyl chloride.

Hydrophobic flat membrane made from a vinylidene fluoride polymer with a wall, a first surface, and a second surface. The membrane has on its first surface a network structure with open pores and on its second surface a continuous skin in which pores are formed, and adjacent to the skin of the second surface a supporting layer with an isotropic pore structure across the wall thickness, wherein the supporting layer extends over at least 80% of the wall thickness and wherein the pores of the supporting layer have an average diameter of less than 1 μm. The weight average of the molecular weight M.sub.W of the vinylidene fluoride polymer lies in the range from 300 000 to 500 000 daltons, and the polydispersivity M.sub.W/M.sub.N is greater than 5.5.

The pores in the skin of the second surface have a closed perimeter in the plane of the skin and an average ratio of the extension in the direction of the longest axis thereof to the extension in the direction of the shortest axis thereof of at most 5. The pores in the first surface and second surface have an essentially isotropic distribution of their orientation. The porosity of the membrane lies in the range from 50 to 90 vol. % and the wall thickness in the range from 50 to 300 μm. The membrane has a maximum separating pore diameter d.sub.max in the range from 0.05 to 1.5 μm.