Macroporous filtration membrane

A hydrophilic, macroporous filtration membrane comprising:

• a flat-sheet membrane based on a film-forming hydrophobic first polymer from the group consisting of aromatic sulfone polymers, and a hydrophilic second polymer, the membrane consisting of a first surface, a second surface, and a supporting layer extending between the first and second surfaces and having a three-dimensional sponge-like network structure,
• the supporting layer has a first cover layer on the side thereof facing the first surface and a second cover layer on the side thereof facing the second surface, which cover layers are formed integrally with the supporting layer, and
• the first and second surfaces have approximately oval or circular openings which penetrate the first and second cover layers, respectively, and are connected to the supporting layer, wherein an average diameter of the openings in the first surface and an average diameter of the openings in the second surface differ by a factor of less than 2,
• the three-dimensional sponge-like network structure of the supporting layer is made up of thick branches and a continuous pore system, and a predominant proportion of the branches have a diameter of at least 0.5 μm at the thinnest point thereof,
• the pores in the supporting layer are larger than the openings in the surfaces, a diameter of the pores in the supporting layer, starting from the first surface cover layer in a direction of the second cover layer, is essentially constant in a first area of the supporting layer over at least 50% of the thickness of the supporting layer, and
• the filtration membrane has a thickness in the range between 30 and 200 μm.