Stable electret polymeric articles
View Patent ↗A porous polymeric sheet is provided having an electrostatic charge and comprising a zero-three composite of a polymeric matrix and a ferroelectric material dispersed therein. The polymeric component comprises a non-polar thermoplastic polymer, such as a polyolefin, and a second thermoplastic polymer having polar functional units, such as a telomer. The composite material is formed into a porous sheet and is electrically or corona poled to create an electret material which is well suited four use in various filtration, air-masking and dust wipe applications.
1. An electret material comprising:
a porous material having an electrostatic charge and comprising a composite;
said composite comprising (i) a polymeric matrix comprising a first thermoplastic polymer and a second thermoplastic polymer substantially compatible with said first thermoplastic polymer, wherein said second thermoplastic polymer is a telomer having polar end units; and (ii) from about 0.01% and about 50% by weight of a ferroelectric material dispersed therein.
2. The electret material of claim 1 wherein said first thermoplastic polymer comprises a non-polar polymer.
3. The electret material of claim 2 wherein said first thermoplastic polymer comprises a polyolefin.
4. The electret material of claim 3 wherein said second polymer comprises between 0.5% and about 25% by weight of said composite and said ferroelectric material comprises from about 0.1% and about 30% by weight of said composite.
5. The electret material of claim 4 wherein said ferroelectric material comprises a perovskite.
6. The electret material of claim 5 wherein said porous material comprises a nonwoven web and wherein said ferroelectric material has an average size less than about 2 micrometers.
7. The electret material of claim 4 wherein said porous material is selected from the group consisting of fibrillated films, sintered films, porous films, woven fabrics, foams, nonwoven webs and multilayer laminates thereof.
8. The electret material of claim 4 wherein said porous material comprises a spunbond fiber web.
9. The electret material of claim 4 wherein said porous material comprises a meltblown fiber web.
10. The electret material of claim 3 wherein said second thermoplastic polymer comprises a nonpolar polymer which has been modified to include a plurality of polar functional groups.
11. The electret material of claim 10 wherein said second thermoplastic polymer comprises a polyolefin polymer randomly grafted to include a plurality of polar functional groups.
12. The electret material of claim 11 wherein said second thermoplastic polymer comprises from about 1% and about 25% by weight of said composite and said ferroelectric material comprises from about 0.5% and about 30% by weight of said composite and further wherein said porous material comprises a nonwoven web.
13. The electret material of claim 3 wherein said second thermoplastic polymer comprises a copolymer of two or more ethylinically unsaturated monomers wherein at least one of the monomers possesses a polar functional group.
14. The electret material of claim 13 wherein said second thermoplastic polymer comprises from about 1% and about 25% by weight of said composite and said ferroelectric material comprises from about 0.5% and about 30% by weight of said composite and further wherein said porous material comprises a nonwoven web.
15. The electret material of claim 1 wherein said telomer has a functional end group selected from the group consisting of aldehyde, acid halide, acid anhydrides, carboxylic acids, amines, amine salts, amides, sulfonic acid amides, sulfonic acid and salts thereof, thiols, epoxides, alcohols, acyl halides, and derivatives thereof.
16. The electret material of claim 1 wherein said first thermoplastic polymer and said telomer each comprise a polymer having a significant fraction of propylene repeat units.
17. The electret material of claim 16 wherein said first thermoplastic polymer comprises polypropylene and wherein said telomer comprises a polypropylene telomer having a functional group selected from acrylic acid, acid anhydrides, carboxylic acids and derivatives thereof.
18. The electret material of claim 1 wherein said first thermoplastic polymer and said telomer comprise a copolymer of propylene and ethylene.
19. The electret material of claim 1 wherein said ferroelectric material is selected from the group consisting of barium titanate, barium strontium titanate, lead titanate and solid solutions thereof.
20. The electret material of claim 1 wherein said porous material is selected from the group consisting of meltblown fiber webs, spunbond fiber webs, hydroentangled webs, air-laid and bonded-carded webs.
21. The electret material of claim 1 wherein said telomer comprises from about 1% and about 15% by weight of said composite and said ferroelectric material comprises from about 0.5% and about 30% by weight of said composite.
22. The electret material of claim 21 wherein the first and second thermoplastic polymers comprise substantially compatible polyolefins.
23. A face mask comprising the electret material of claim 3 .
24. A sterilization wrap comprising the electret material of claim 2 .
25. A sterilization wrap comprising a spunbond/meltblown/spunbond laminate wherein at least one of said layers comprises the electret material of claim 2 .
26. A dust wipe comprising the electret material of claim 3 .
27. An air filter material comprising the electret material of claim 3 .