Gradient density filter
AssigneeMinnesota Mining and Manufacturing Company
InventorsPeter J. Ellefson, David A. Wells
Life of this patent
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Abstract
A gradient density filter made from sheets of blown polypropylene microfibers where the microfibers of at least one of the sheets have an effective fiber diameter less than that of the other sheets is described. This filter is especially useful in solid phase extraction processes, particularly those where biological fluids are being analyzed.
Claims16
A filter for removing insoluble materials from a liquid, said filter having upstream and downstream sides, comprising a plurality of sheets of blown polypropylene microfibers, at least one of said sheets having an effective pore diameter smaller than the effective pore diameter of at least one sheet upstream therefrom, all of said polypropylene fibers having a critical wetting surface tension less than about 50 dynes/cm, the aggregate average diameter of said microfibers being at least 3 .mu.m.
Dependencies are inferred from the claim text.