Pall Corporation

Moira H Bilich

Peter J Degen

Trevor A Staff

Robert E Kesting

John Mischenko, Iii

Richard F Salinaro

John R Gerringer

The present invention provides a filtration medium comprising an ultrafiltration membrane and a monomer surface coating thereon of an acrylic or methacrylic acid monomer having alcohol functional groups, wherein the filtration medium after having been fully dried is characterized by having a titer reduction of at least about 10.sup.3 with respect to PP7 bacteriophage and a critical wetting surface tension of at least about 70 mN/m. The filtration medium preferably further comprises a fibrous nonwoven web embedded in the membrane. The present invention also provides a method of filtering a fluid through the present inventive filtration medium, as well as a method of preparing such a filtration medium.

Filtration medium

The present invention provides for the first time ultrafiltration/diafiltration membranes that are capable of excluding 0.02 .mu.m diameter, monodisperse, latex particles and are capable of being dried without loss of such ultrafiltration properties. A rapid, reliable method for integrity testing membranes also has now been discovered. The test has particular applicability to ultrafiltration membranes, although it may also be used for testing microfiltration membranes as well. In accordance with the method, referred to as the K.sub.UF method, the membrane to be tested is first thoroughly wetted with a wetting liquid that is capable of fully wetting the membrane; a displacing liquid is placed in contact with one side of the wetted membrane and increasing pressure is then applied to said displacing liquid; and the flow rate through said membrane is measured as a function of the applied pressure; wherein the displacing liquid is substantially insoluble in the wetting liquid and the interfacial tension between the two liquids is about 10.0 dynes/cm or less. A plot of the flow rate of liquid, per unit area of the membrane, through the membrane as a function of applied pressure can be made and a straight line may be drawn through the steep part of the resulting curve, using regression analysis, which will intersect the horizontal axis at a given pressure value, which is then the K.sub.UF value.

Integrity-testable wet-dry-reversible ultrafiltration membranes and

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Massapequa, NY, United States of America

Moira H Bilich