Conventional porous membranes have a mesh structure having a relatively large pore diameter in order to improve the removability of a relatively large component such as a virus. When a contaminative liquid to be filtered is filtered, contaminants are easily accumulated in the porous membranes, clogging or the like occurs in the porous membranes, and contamination of the porous membranes easily occurs. Accordingly, an object is to provide a porous membrane having high contamination resistance and high-precision removability. To achieve the object, provided is a porous membrane including, in at least one surface, a surface portion spanning 10 ?m in thickness from the surface, being denser than an inner portion, and having a removal rate T of dextran having a weight-average molecular weight of 40,000 Da of 60 to 95%, in which a number of surface pores per unit area observed on the surface of the surface portion is 200 pores/?m.sup.2 to 2,000 pores/?m.sup.2.

The invention relates to a method for creating a porous film through aqueous phase separation, the method comprising: i) providing an aqueous solution comprising a responsive copolymer, and optionally a charged polymer, wherein at least one of the monomers in the responsive copolymer is a responsive monomer; ii) forming the aqueous solution into a thin layer and contacting the thin layer of aqueous solution with an aqueous coagulation solution in which the responsive copolymer is not soluble, or contacting the thin layer of aqueous solution with an aqueous coagulation solution in which a complex comprising the responsive copolymer and the charged polymer is not soluble; and iii) allowing solvent exchange between the aqueous solution and the aqueous coagulation solution to produce a porous film. The invention further relates to porous films or membranes thus obtained.

A hollow fiber membrane and a method of preparing the same. The hollow fiber membrane has an inner surface and an outer surface, wherein the inner surface has a zebra-stripe pattern in which a dense portion and a porous portion are alternately formed in a longitudinal direction of the hollow fiber membrane.

The present invention is an integral multilayered composite membrane having at least one ultrafiltration layer made by cocasting or sequentially casting a plurality of polymer solutions onto a support to form a multilayered liquid sheet and immersing the sheet into a liquid coagulation bath to effect phase separation and form a multilayered composite membrane having at least one ultrafiltration layer.

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.

Provided is a method for manufacturing a sheet-shaped separation membrane that allows a sheet-shaped separation membrane having uniform separating ability to be manufactured at a high speed, the method comprising manufacturing a sheet-shaped separation membrane by forming a microporous layer on a porous substrate, wherein the method is characterized in having: a membrane-forming solution application step of coating a porous substrate with a membrane-forming solution in which a polymer is dissolved in a solvent, a congealing liquid application step of applying a congealing liquid by a liquid membrane drop method to the porous substrate coated with the membrane-forming solution, and a solvent removal step of removing the solvent from the congealed microporous layer.

Provided is a method for preparing a durable hydrophilic ultrafiltration membrane. In the disclosure, a functional hydrophilic molecule is synchronously synthesized during conventional dissolution of a polymer membrane material; and a resulting casting solution (a nascent membrane) is introduced into a coagulation bath, which initiates a cross-linking reaction between the functional hydrophilic molecules to form a hydrophilic cross-linked network. A hydrophilic cross-linked interpenetrating network is formed in situ during polymer phase separation to limit movement of polymer chains and formation and growth of micelles, thereby forming a relatively uniform polymer interpenetrating network structure to obtain the durable hydrophilic ultrafiltration membrane with a relatively uniform membrane pore structure.

The present invention relates to a membrane (M) comprising a sulfonated poly(arylene ether sulfone) polymer (sP) and a non-sulfonated poly(arylene sulfone) polymer (P), to a method for the preparation of the membrane (M) and to the use of the membrane as nanofiltration membrane. Further, the present invention relates to a monolithic film (F) comprising a sulfonated poly(arylene ether sulfone) polymer (sP) and a non-sulfonated poly(arylene sulfone) polymer (P), wherein the monolithic film has a contact angle of 63 to 77.

A polymer membrane for water treatment, characterized in comprising a hollow fiber membrane having a self-supporting design composed of the substantially single principal structural material, with an outer diameter of 3.6 mm to 10 mm and a ratio of outer diameter to thickness, SDR, of 3.6 to 34.

Hollow fiber membranes comprising fluoro-copolymers, and processes of making and using the hollow fiber membranes are described. The fluoro-copolymers have a weight average molecular weight between about 100,000 and about 500,000 Daltons. The fluoro-copolymer comprises trans-1,3,3,3-tetrafluoropropene monomers and vinylidene difluoride monomers, and at least 50 wt % of the fluoro-copolymer comprises trans-1,3,3,3-tetrafluoropropene monomers.