The invention relates to a mechanically stable ultrafiltration membrane and to a method for producing such an ultrafiltration membrane.

The invention relates to a mechanically stable ultrafiltration membrane and to a method for producing such an ultrafiltration membrane.

The present invention relates to a separation membrane including a thermoplastic polymer selected from a cellulose ester and a polyamide, in which, when regions obtained by dividing a cross-sectional surface perpendicular to a longitudinal direction of the separation membrane into 5 at an equal interval are defined as regions 1 to 5, all the regions 1 to 5 have a number average pore diameter changing rate a of −0.25 to 0.25, and at least one of the regions 1 to 5 is a region P that satisfies conditions (a) and (b): (a) a value of area average pore diameter D.sub.s/number average pore diameter D.sub.n is 2.50 to 6.00; and (b) a number average W of fine pores that are located at a distance smaller than L.sub.a from a center of respective coarse pores is 10 to 30.

The present invention relates to a separation membrane including a thermoplastic polymer selected from a cellulose ester and a polyamide, in which, when regions obtained by dividing a cross-sectional surface perpendicular to a longitudinal direction of the separation membrane into 5 at an equal interval are defined as regions 1 to 5, all the regions 1 to 5 have a number average pore diameter changing rate a of −0.25 to 0.25, and at least one of the regions 1 to 5 is a region P that satisfies conditions (a) and (b): (a) a value of area average pore diameter D.sub.s/number average pore diameter D.sub.n is 2.50 to 6.00; and (b) a number average W of fine pores that are located at a distance smaller than L.sub.a from a center of respective coarse pores is 10 to 30.

Provided is a method for preparing a gas separation membrane, the method including forming a porous layer by coating a hydrophilic polymer solution on a porous substrate; and forming an active layer by coating a composition for forming an active layer including a polymer of Chemical Formula 1 on the porous layer, ##STR00001## wherein in Chemical Formula 1, n is the number of a repeating unit, and is an integer of 500 to 3,000, and R1 to R5 are the same as or different from each other, and each independently is hydrogen, an alkyl group, or —(C═O)R6, and R6 is an alkyl group, wherein the polymer of Chemical Formula 1 is included in an amount from 1% by weight to 5% by weight based on the composition for forming an active layer, and a gas separation membrane prepared using the same.

Provided is a method for preparing a gas separation membrane, the method including forming a porous layer by coating a hydrophilic polymer solution on a porous substrate; and forming an active layer by coating a composition for forming an active layer including a polymer of Chemical Formula 1 on the porous layer, ##STR00001## wherein in Chemical Formula 1, n is the number of a repeating unit, and is an integer of 500 to 3,000, and R1 to R5 are the same as or different from each other, and each independently is hydrogen, an alkyl group, or —(C═O)R6, and R6 is an alkyl group, wherein the polymer of Chemical Formula 1 is included in an amount from 1% by weight to 5% by weight based on the composition for forming an active layer, and a gas separation membrane prepared using the same.

There are provide a cell separation filter with which cells can be separated without damage and can suppress adsorption, a filtering device, and a manufacturing method for a cell separation filter. The cell separation filter is composed of a nonwoven fabric that is formed of fibers containing a water-insoluble polymer and a hydrophilizing agent and has a fiber density difference in the film thickness direction. The nonwoven fabric has an average through-hole diameter of 2.0 μm or more and less than 10.0 μm, a void ratio of 75% or more and 98% or less, a film thickness of 100 μm or more, and a critical wet surface tension of 72 mN/m or more.

Provided are a hydrophilic porous membrane including a porous membrane and a hydroxyalkyl cellulose retained in the porous membrane, in which the average pore size differs between two surfaces of the porous membrane, the hydroxyalkyl cellulose distributed in the thickness direction of the hydrophilic porous membrane exhibits two or more peaks of detection intensity in GPC, and the weight-average molecular weight Mw.sub.min of the peak that is detected latest among the above-mentioned peaks is less than 100,000; and a method for producing a hydrophilic porous membrane, the method including separately preparing a hydrophilizing liquid including a hydroxyalkyl cellulose having a smaller weight-average molecular weight and a hydrophilizing liquid including a hydroxyalkyl cellulose having a larger weight-average molecular weight, and applying each of the hydrophilizing liquids on two surfaces of the porous membrane or sequentially on one surface thereof.

Provided are a hydrophilic porous membrane including a porous membrane and a hydroxyalkyl cellulose retained in the porous membrane, in which the average pore size differs between two surfaces of the porous membrane, the hydroxyalkyl cellulose distributed in the thickness direction of the hydrophilic porous membrane exhibits two or more peaks of detection intensity in GPC, and the weight-average molecular weight Mw.sub.min of the peak that is detected latest among the above-mentioned peaks is less than 100,000; and a method for producing a hydrophilic porous membrane, the method including separately preparing a hydrophilizing liquid including a hydroxyalkyl cellulose having a smaller weight-average molecular weight and a hydrophilizing liquid including a hydroxyalkyl cellulose having a larger weight-average molecular weight, and applying each of the hydrophilizing liquids on two surfaces of the porous membrane or sequentially on one surface thereof.

The present invention relates to a separation membrane including a thermoplastic polymer selected from a cellulose ester and a polyamide, in which, when regions obtained by dividing a cross-sectional surface perpendicular to a longitudinal direction of the separation membrane into 5 at an equal interval are defined as regions 1 to 5, all the regions 1 to 5 have a number average pore diameter changing rate α.sub.i of −0.25 to 0.25, and at least one of the regions 1 to 5 is a region P that satisfies conditions (a) and (b): (a) a value of area average pore diameter D.sub.s/number average pore diameter D.sub.n is 2.50 to 6.00; and (b) a number average W of fine pores that are located at a distance smaller than L.sub.a from a center of respective coarse pores is 10 to 30.