Melt-blown fibrous electrets
AssigneeMinnesota Mining and Manufacturing Company
InventorsDonald A. Kubik, Charles I. Davis
Life of this patent
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Abstract
A persistent electric charge is introduced into melt-blown fibers during the melt-blowing process. When these charged fibers are incorporated into fibrous webs, they provide unique properties, including improved filtering properties.
Claims18
A fibrous web electret comprising melt-blown fibers prepared by extruding molten fiber-forming material through orifices into a high-velocity gaseous stream where the extruded material is drawn out into fibers and solidified in the fibrous form, said fibers having electrically charged particles and a persistent electric charge that is useful to enhance filtering properties of the web, said charge having a half-life of at least one week in a room-temperature, 100-percent-relative-humidity environment.
A fibrous web electret comprising a coherent mass of randomly intertangled melt-blown microfibers which average less than 10 micrometers in diameter, said microfibers being prepared by extruding molten fiber-forming material through orifices into a high-velocity gaseous stream where the extruded material is drawn out into fibers and solidified in the fibrous form, said microfibers having electrically charged particles in an amount sufficient to provide a persistent electric charge of at least 10.sup.-8 coulombs per gram of said microfibers, with a half-life of at least six months in a room-temperature, 100-percent-relative-humidity environment.
A method for forming a melt-blown fibrous web electret comprising
- (1) extruding molten fiber-forming material that exhibits a volume resistivity of at least 10.sup.14 ohm-centimeters through a plurality of orifices into a high-velocity gaseous stream where the extruded material is attenuated to form a stream of fibers;
- (2) bombarding electrically charged particles at said stream of fibers as the fibers issue from the orifices wherein the fibers are both near the source of the electrically charged particles and are in a molten or near-molten state;
- and
- (3)collecting said fibers at a point sufficiently remote from the orifices for the fibers to have cooled to a solid fibrous shape-retaining form.
Dependencies are inferred from the claim text.