Abstract: A virus removal membrane is formed from a hydrophilized synthetic polymer, in which, when a solution containing gold colloids having a diameter of 20 nm is applied through a primary surface to the virus removal membrane to allow the virus removal membrane to capture the gold colloids for measurement of brightness in a cross section of the virus removal membrane, a value obtained by dividing a standard deviation of a value of an area of a spectrum of variation in the brightness by an average of the value of the area is 0.01 or more and 1.5 or less; and a thickness of a portion, where gold colloids having a diameter of 20 nm or more and 30 nm or less are captured, in the cross section of the virus removal membrane in a wet state is 10 ?m or more and 30 ?m or less.

Abstract: A virus removal membrane is formed from a hydrophilized synthetic polymer, in which, when a solution containing gold colloids having a diameter of 20 nm is applied through a primary surface to the virus removal membrane to allow the virus removal membrane to capture the gold colloids for measurement of brightness in a cross section of the virus removal membrane, a value obtained by dividing a standard deviation of a value of an area of a spectrum of variation in the brightness by an average of the value of the area is 0.01 or more and 1.5 or less; and a thickness of a portion, where gold colloids having a diameter of 20 nm or more and 30 nm or less are captured, in the cross section of the virus removal membrane in a wet state is 10 ?m or more and 30 ?m or less.

Abstract: A heat resistant microporous membrane containing a thermoplastic resin having a crystalline melting point of 140-300° C. and having a layer structure formed in the direction of membrane thickness, said layer structure containing 5-100% of a layer defined by the following (A) and 95-0% of a layer defined by the following (B): (A) a layer in which the micropores are intra-spherulitic voids, and (B) a layer in which the micropores are intra-spherulitic voids and inter-spherulitic voids.

Abstract: A hydrophilic microporous membrane comprising a thermoplastic resin, having been subjected to hydrophilizing treatment and having a maximum pore size of 0 to 100 nm, wherein when 3 wt % bovine immunoglobulin having a monomer ratio of 80 wt % or more is filtered at a constant pressure of 0.3 MPa, an average permeation rate (liter/m2/h) for 5 minutes from the start of filtration (briefly referred to as globulin permeation rate A) satisfies the following formula (1) and an average permeation rate (liter/m2/h) for 5 minutes from the time point of 55 minutes after the start of filtration (briefly referred to as globulin permeation rate B) satisfies the following formula (2): Globulin permeation rate A>0.0015 ×maximum pore size (nm)2.75 ??(1) Globulin permeation rate B/globulin permeation rate A>0.2 .

Abstract: A multilayer microporous membrane containing a thermoplastic resin, comprising a coarse structure layer with a higher open pore ratio and a fine structure layer with a lower open pore ratio, wherein said coarse structure layer is present at least in one membrane surface having a thickness of not less than 5.0 ?m, a thickness of said fine structure layer is not less than 50% of the whole membrane thickness, and said coarse structure layer and said fine structure layer are formed in one-piece.

Abstract: A hydrophilic microporous membrane comprising a thermoplastic resin, having been subjected to hydrophilizing treatment and having a maximum pore size of 10 to 100 nm, wherein when 3 wt % bovine immunoglobulin having a monomer ratio of 80 wt % or more is filtered at a constant pressure of 0.3 MPa, an average permeation rate (liter/m2/h) for 5 minutes from the start of filtration (briefly referred to as globulin permeation rate A) satisfies the following formula (1) and an average permeation rate (liter/m2/h) for 5 minutes from the time point of 55 minutes after the start of filtration (briefly referred to as globulin permeation rate B) satisfies the following formula (2): Globulin permeation rate A>0.0015×maximum pore size (nm)2.75 ??(1) Globulin permeation rate B/globulin permeation rate A>0.2 ??(2).

Abstract: A microporous membrane is produced by cooling a solution comprising a vinylidene fluoride homopolymer or copolymer having a weight average molecular weight of 1×105 or more and a solvent therefor, to form a two-phase gel, said microporous membrane comprising a polymer phase comprising said vinylidene fluoride homopolymer or copolymer, and intercommunicating voids which have an average pore size measured by the half-dry method of 0.005 to 5 &mgr;m and range from one side of the membrane to the other side, and said microporous membrane having as its internal structure a percolation structure in which the polymer phase forms an isotropic network structure by three-dimensional branching in arbitrary directions, the voids are formed by surrounding by said polymer phase of the network structure and intercommunicate with one another, and the ratio of the maximum pore size measured by the bubble point method to the average pore size measured by the half-dry method is 2.0 or less.

Abstract: A multilayer microporous membrane containing a thermoplastic resin, comprising a coarse structure layer with a higher open pore ratio and a fine structure layer with a lower open pore ratio, wherein said coarse structure layer is present at least in one membrane surface having a thickness of not less than 5.0 &mgr;m, a thickness of said fine structure layer is not less than 50% of the whole membrane thickness, and said coarse structure layer and said fine structure layer are formed in one-piece.