Pall Corporation

John Mischenko, Iii

Peter J Degen

Robert E Kesting

Moira H Bilich

Trevor A Staff

David B Pall

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

A self-cleaning system and method for dispersing aggregates in a fluid medium is provided. The system is comprised of first and second members operatively associated to form an internal chamber and having an inlet to the chamber for admitting the fluid to be treated. At least one of the members is biased toward the other whereby the introduction of a fluid medium to be treated into the chamber under an operating pressure in the range of from about 50 to about 1,000 psid (3.5 to 70.3 kg/cm.sup.2) provides an elongated orifice between the first and second members having a transverse dimension or width of from about 1 to about 1,500 micrometers for egress of the fluid medium. As the fluid passes through the elongated orifice, aggregates contained therein are dispersed. The system is self-cleaning by virtue of the biased nature of at least one of the members toward the other, thereby providing longer onstream operation and requiring less servicing. The system can be used for treating aggregate-containing fluids such as oil well completion fluids, dispersions used in the manufacture of magnetic tape, and dispersion of particulates such as carbon black and other pigments.

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Amityville, NY, United States of America

John Mischenko, Iii