Abstract: The object of the present invention is to provide a porous membrane by which a useful component can be recovered while suppressing the clogging during filtration of a protein solution and from which only a small amount of an eluate is eluted even when an aqueous solution is filtered. The present invention provides a porous membrane containing a hydrophobic polymer and a water-insoluble hydrophilic polymer, the porous membrane having a dense layer in the downstream portion of filtration in the membrane, having a gradient asymmetric structure in which the average pore diameter of fine pores increases from the downstream portion of filtration toward the upstream portion of filtration, and having a gradient index of the average pore diameter from the dense layer to the coarse layer of 0.5 to 12.0.

Abstract: A porous membrane containing a hydrophobic polymer and a water-insoluble hydrophilic polymer, the porous membrane having a dense layer in the downstream portion of filtration in the membrane, having a gradient asymmetric structure in which the average pore diameter of fine pores increases from the downstream portion of filtration toward the upstream portion of filtration, and having a gradient index of the average pore diameter from the dense layer to the coarse layer of 0.5 to 12.0.

Abstract: The present invention provides a porous hollow fiber membrane including a polysulfone-based polymer and a hydrophilic polymer, and having a dense layer in a section from an outer surface portion to a center region of a membrane thickness, a thickness of the dense layer being 10 to 30 ?m, and a ratio of a pore having a pore size of more than 50 nm and a ratio of a pore having a pore size of 10 nm or smaller in the dense layer being 25 to 40% and 20% or less, respectively.

Abstract: The present invention provides a porous hollow fiber filtration membrane comprising a polysulfone-based polymer and hydrophilic polymer, the porous hollow fiber filtration membrane including a gradient asymmetric structure in which the average pore diameter of fine pores increases from the outer surface toward the inner surface, a content of the hydrophilic polymer in the membrane is 6.0 to 12.0% by mass, and a ratio of the content of the hydrophilic polymer in the outer surface to the content of the hydrophilic polymer in the membrane is 1.20 to 1.60.

Abstract: A hollow fiber filtration membrane in which even when a relatively small contaminant having a size close to that of a permeation effective component is present in a filtration solution, Flux decrease over time during filtration is suppressed, and a useful component can be efficiently recovered, the hollow fiber filtration membrane including a polysulfone-based polymer and a hydrophilic polymer and having a large number of pores, the hollow fiber filtration membrane having a gradient asymmetric porous structure in which an average pore diameter of the pores increases from an outer surface portion toward an inner surface portion of the membrane, a content of the hydrophilic polymer of the membrane being from 6.0 to 10.0% by mass, a ratio between a content of the hydrophilic polymer at the inner surface portion and the content of the hydrophilic polymer of the membrane being in the range of from 0.50 to 0.80.

Abstract: The object of the present invention is to provide a porous membrane by which a useful component can be recovered while suppressing the clogging during filtration of a protein solution and from which only a small amount of an eluate is eluted even when an aqueous solution is filtered. The present invention provides a porous membrane containing a hydrophobic polymer and a water-insoluble hydrophilic polymer, the porous membrane having a dense layer in the downstream portion of filtration in the membrane, having a gradient asymmetric structure in which the average pore diameter of fine pores increases from the downstream portion of filtration toward the upstream portion of filtration, and having a gradient index of the average pore diameter from the dense layer to the coarse layer of 0.5 to 12.0.