US 5,620,790 AGranted

Multi-layer microfiltration membrane having an integrated prefiltration layer and method of making same

AssigneeSeitz-Filter-Werke GmbH und Co.

InventorsUdo Holzki, Heinz-Joachim Muller, Tilo Renner

Life of this patent

Estimating the term…

Loading patent…

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.

Claims20

Dependent claims

A multi-layer, unsupported, integral microfiltration membrane of polymeric material that is suitable for a phase inversion process, said membrane comprising:

at least one final filtration layer having a thickness of from 50 to 300 .mu.m and a symmetrical pore structure;
and
at least one integrated prefiltration layer, wherein the ratio of said thickness of said final filtration layer to a thickness of said prefiltration layer is in the range of from 1:4 to 4:1, said multi-layered membrane having been formed by
pouring out a first layer of a solution of polymeric material onto a substrate and
subsequently successively pouring out one or more further layers of a solution of polymeric material onto said first layer prior the occurrence of turbidity in each successive immediately preceding layer, the viscosity of each successive layer of a solution of polymeric material having been the same as or less than that of the preceding layer.

2 more elements

Dependencies are inferred from the claim text.