Abstract: Process for the partial modification of porous, hydrophilitic filter membranes, of filter membranes treated in such manner and filter modules equipped with such filter membranes. When hydrophilic filter membranes are embedded in hydrophobic securing components of filter modules, the membrane filters are hydrophobized beyond the embedding area in an edge region, so that this edge region, that can no longer be wetted by water, forms an air by-pass when the filter modules are tested, rendering thus impossible that the filter modules can be tested. The novel process is intended to modify the edge regions in such a manner that, even after partial areas have been embedded in a hydrophobic polymer material, they remain porous and hydrophilic over the whole of their effective area.

Abstract: The disclosure is a more economical process for producing fibrets of superior quality by directing a dope comprising a cellulose derivative and a suitable solvent therefor into a coagulant and exposing it there to a shearing field to coagulate of the dope and form the fibrets. The fibrets, the solvent and the coagulant are then separated off. The suspension formed from the dope and the coagulant is alternately accelerated and decelerated in the shearing field at least once, preferably at least twice. This makes it possible to maintain a high average degree of turbulence over a long distance, so that a dope of high viscosity can be processed. In the apparatus for producing fibrets, the at least one nozzle (46-49) is disposed within a dispersing facility (40) comprising rotor (44) and stator (43, 45) and further comprising at least two sprockets (50-53), of which at least one sprocket (50) is part of the rotor (44) of the dispersing facility (40).

Abstract: A multi-layer microfiltration membrane having an integrated prefiltration layer. Pursuant to a phase inversion process, several layers are successively poured out onto one another prior to phase separation of a lower layer, with the viscosity for the pour solution decreasing toward the upper layers. This produces a microporous, multi-layer, integral filtration membrane having a homogenous symmetrical pore structure for the final filtration layer and an open-pored structure for the prefiltration layer disposed therebelow. Even with small pore diameters, this membrane can be easily pleated for installation in filter cartridges without the formation of damage at the crease edges. High throughput rates are possible at a low tendency to clog.