Abstract: Provided is a porous membrane having high filtration performance and little deterioration of water permeation performance due to membrane surface abrasion when used in a method of clarifying, by membrane filtration, turbid water that is natural water, domestic wastewater, or water resulting from treatment thereof. In the porous membrane, a ratio of internal porosity in a thickness up to 0.12% of membrane thickness from a topmost surface of a surface at a filtration feed side relative to surface porosity of the surface at the filtration feed side is 1.05 or more.

Abstract: A method of producing a hollow fiber membrane is provided. The method includes: extruding from a molding nozzle a membrane-forming stock solution, the membrane-forming stock solution containing a vinylidene fluoride-based resin, polyethylene glycol, and a common solvent, and having a slope (B) of 1.15 or more and less than 3.00 where the slope (B) is calculated by I=A×q?B from a scattering intensity of a small-angle X-ray; and solidifying the extruded membrane-forming stock solution in a solution containing water as a main component.

Abstract: Provided is a porous membrane which has a high water permeability performance, a high blocking performance, and a durability performance against loads of long-term and high operation pressures, which are suitable for filtering applications. The porous membrane includes one surface to be on a side of a filtrate; and the other surface to be on a side of a liquid to be filtered, wherein a surface pore diameter index of the one surface is 2.5 or more, the surface pore diameter index being determined by dividing a pore diameter in a top surface by a pore diameter in a second top surface.

Abstract: A porous membrane has a thickness of 150 ?m or greater. The pore diameters of a first surface are smaller than the pore diameters of a second surface. The average value of the pore diameters of the first surface is 60 nm or less, and the coefficient of variation of the pore diameters is 10% or greater and 50% or less.

Abstract: A hollow fiber membrane contains a vinylidene fluoride-based resin and polyethylene glycol. In the hollow fiber membrane, the polyethylene glycol has a content of 1.0 part by weight or more and less than 5.0 parts by weight with respect to 100 parts by weight of the vinylidene fluoride-based resin. In a case where the hollow fiber membrane is divided in three equal parts by a line drawn from an inner surface side to an outer surface side of the hollow fiber membrane in a radial direction of a cross section perpendicular to a longitudinal direction of the hollow fiber membrane, and where polyethylene glycol normalized intensities at respective intermediate points are defined as inner surface part a, central part b, and outer surface part c, c is less than 0.3 and a is 0.5 or more.

Abstract: When the porous membrane, which has two surfaces of a surface A and a surface C, is equally divided in the thickness direction of the porous membrane into three layers of a first layer including the surface A, a second layer that is a central layer in the thickness direction, and a third layer including the surface C, an average trunk size of the third layer is larger than an average trunk size of the second layer, and when a continuous layer from the surface A having a thickness of 10 ?m in the first layer is a first layer component, a continuous layer component having a thickness of 10 ?m and an average trunk size smaller than an average trunk size of the first layer component is present in the first layer, the second layer, and the third layer other than the first layer component.

Abstract: Provided is a porous membrane which has a high water permeability performance, a high blocking performance, and a durability performance against loads of long-term and high operation pressures, which are suitable for filtering applications. The porous membrane includes one surface to be on a side of a filtrate; and the other surface to be on a side of a liquid to be filtered, wherein a surface pore diameter index of the one surface is 2.5 or more, the surface pore diameter index being determined by dividing a pore diameter in a top surface by a pore diameter in a second top surface.

Abstract: A porous membrane has a thickness of 150 ?m or greater. The pore diameters of a first surface are smaller than the pore diameters of a second surface. The average value of the pore diameters of the first surface is 60 nm or less, and the coefficient of variation of the pore diameters is 10% or greater and 50% or less.

Abstract: When the porous membrane, which has two surfaces of a surface A and a surface C, is equally divided in the thickness direction of the porous membrane into three layers of a first layer including the surface A, a second layer that is a central layer in the thickness direction, and a third layer including the surface C, an average trunk size of the third layer is larger than an average trunk size of the second layer, and when a continuous layer from the surface A having a thickness of 10 ?m in the first layer is a first layer component, a continuous layer component having a thickness of 10 ?m and an average trunk size smaller than an average trunk size of the first layer component is present in the first layer, the second layer, and the third layer other than the first layer component.

Abstract: Methods of producing a deformed porous hollow fiber membrane by thermally induced phase separation, particularly by discharging a fusion kneaded product containing a thermoplastic resin and an organic liquid through an orifice of a hollow fiber-forming deformed nozzle; cooling and solidifying the fusion kneaded product discharged through the deformed nozzle to form the product into a hollow fiber-like material having a deformed cross section at a cross section vertical to a discharging direction; and extracting away the organic liquid from the hollow fiber-like material to obtain the deformed porous hollow fiber membrane, wherein an inorganic fine powder is kneaded in the fusion kneaded product.

Abstract: A porous hollow fiber membrane that is suitable for treatment of liquid containing an inorganic substance and/or an organic substance, is obtained at a low cost performance, and has high water permeability performance, fretting resistance, and drying resistance. A deformed porous hollow fiber membrane according to the present invention is composed of a thermoplastic resin and includes a continuous asperity provided on the periphery in the longitudinal direction of the membrane, in which the periphery of the hollow fiber membrane in the circumferential direction includes continuous projected and depressed parts.

Abstract: Methods of producing a deformed porous hollow fiber membrane by thermally induced phase separation, particularly by discharging a fusion kneaded product containing a thermoplastic resin and an organic liquid through an orifice of a hollow fiber-forming deformed nozzle; cooling and solidifying the fusion kneaded product discharged through the deformed nozzle to form the product into a hollow fiber-like material having a deformed cross section at a cross section vertical to a discharging direction; and extracting away the organic liquid from the hollow fiber-like material to obtain the deformed porous hollow fiber membrane, wherein an inorganic fine powder is kneaded in the fusion kneaded product.

Abstract: A porous hollow fiber membrane that is suitable for treatment of liquid containing an inorganic substance and/or an organic substance, is obtained at a low cost performance, and has high water permeability performance, fretting resistance, and drying resistance. A deformed porous hollow fiber membrane according to the present invention is composed of a thermoplastic resin and includes a continuous asperity provided on the periphery in the longitudinal direction of the membrane, in which the periphery of the hollow fiber membrane in the circumferential direction includes continuous projected and depressed parts.

Abstract: A porous hollow fiber membrane which has high blocking performance and high water permeability suitable for filtration and the like and exhibits excellent strength, and a process for stably producing the porous hollow fiber membrane are disclosed. The process utilizes a hollow fiber molding nozzle having two or more circular discharge ports which are disposed concentrically. Multilayer melt-extrusion is performed by discharging molten mixtures which include a thermoplastic resin and an organic liquid and differ in composition from the adjacent discharge ports. The resulting product is cooled to solidify to obtain a hollow fiber. The organic liquid is then removed from the hollow fiber by extraction to produce a porous hollow fiber membrane. The molten mixture discharged from at least one circular discharge port includes an inorganic fine powder in addition to the thermoplastic resin and the organic liquid. The inorganic fine powder is removed by extraction after cooling in addition to the organic liquid.

Abstract: A porous hollow fiber membrane which has high blocking performance and high water permeability suitable for filtration and the like and exhibits excellent strength, and a process for stably producing the porous hollow fiber membrane are disclosed. The process utilizes a hollow fiber molding nozzle having two or more circular discharge ports which are disposed concentrically. Multilayer melt-extrusion is performed by discharging molten mixtures which include a thermoplastic resin and an organic liquid and differ in composition from the adjacent discharge ports. The resulting product is cooled to solidify to obtain a hollow fiber. The organic liquid is then removed from the hollow fiber by extraction to produce a porous hollow fiber membrane. The molten mixture discharged from at least one circular discharge port includes an inorganic fine powder in addition to the thermoplastic resin and the organic liquid. The inorganic fine powder is removed by extraction after cooling in addition to the organic liquid.