Cellulose hydrate membrane, method for the production thereof, and use thereof

A crosslinked cellulose hydrate membrane having a porous double structure consisting of

• micropores having a diameter in the range from >100 nm to 20 μm, and
• ultrapores which have a diameter of <100 nm and which are not accessible to Blue Dextran having an average molecular weight Mw of 2 000 000, wherein the fraction of the volume of the ultrapores is more than 15% of the entire pore volume accessible to water,
• wherein the crosslinked cellulose hydrate membrane is obtained by a method comprising:
• providing a cellulose ester membrane having a pore diameter in the range from 0.1 to 20 μm;
• hydrolyzing the cellulose ester membrane under a swelling condition;
• and
• crosslinking the hydrolyzed cellulose ester membrane;
• wherein the hydrolysis and the crosslinking are carried out separately, and;
• the hydrolysis is carried out in a hydrolysis medium consisting of water and one or both of sodium hydroxide and lithium hydroxide, wherein the concentration of one or both of sodium hydroxide and lithium hydroxide in the hydrolysis medium is in the range of 0.4 to 10% by weight, based on the hydrolysis medium.