Fine particle liquid filtration media

Abstract

The present invention provides a filter media comprising (a) a nonwoven composite material comprising a stabilized mixture of thermoplastic microfibers and at least about 50%, by weight, of a secondary fibrous material such as pulp or polymeric staple fibers; (b) a first outer nonwoven web comprising a substantially uniform nonwoven web of autogenously bonded multicomponent fibers; and (c) a second outer nonwoven web wherein the nonwoven composite material is positioned between the first outer nonwoven web and second outer nonwoven web. The filter material is well suited to filtering liquid borne particulate matter ranging in size from 5.mu. to about 25.mu..

Description

FIELD OF THE INVENTIONThe present invention relates to nonwoven composite fabrics suitable for use for fine particle liquid filtration.BACKGROUND OF THE INVENTIONNonwoven fabrics have been used for a variety of filtration and filtration-like applications. As an example, fine fiber webs such as meltblown fabrics and laminates thereof have commonly been used within air filtration media. Meltblown fabrics comprise a web of randomly inter-laid fine fibers, which provide a structure having excellent barrier properties. Generally, as the average fiber diameter decreases there is a corresponding decrease in the average pore size of the fabric. Thus, fabrics with finer fibers or smaller diameter fibers typically have increased barrier properties when compared to like webs of relatively larger fiber size. Therefore, due to fine fibers achievable in meltblown fiber webs and the excellent barrier properties resulting therefrom, meltblown fiber webs have been used in a variety of air filtration...

AI Technical Summary

Problems solved by technology

However, the needs of air filtration media often vary considerably from those of liquid filtration media.

In this regard, air filtration media are often expected to collect particles having a size less than about 5.mu. whereas with fine particle liquid filtration the particle size often varies between about 5.mu.to about 30.mu.. Multilayer filtration media suitable for air filtration, such as that described above, will often have an unacceptably short filter life when used for liquid filtration.

Additionally, meltblown fiber nonwoven webs can be relatively weak fabrics and often cannot, by themselves, withstand the conditions experienced by liquid filtration media.

However, many nonwoven laminates are point bonded to form an integrated structure and, in this regard, the point bonds undesirably increase pressure drop without a corresponding increase in filter life and / or efficiency.