Electret filter media and filtering masks that contain electret filter media

• US 6,783,574 B1
• Filed: 09/02/1997
• Issued: 08/31/2004
• Est. Priority Date: 08/17/1993
• Status: Expired due to Fees

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Angadjivand, Seyed A., Jones, Marvin E., Meyer, Daniel E.
• Primary Examiner(s): Chiesa, Richard L.
• Application Number:
  US09/111,833
• Time in Patent Office: 2,555 Days
• Field of Search: 555/28, 555/24, 555/27, 55D/IG.5, 55D/IG.39, 55D/IG.35, 264/436, 264/12, 264/234, 264/483, 264/423, 264/DIG.8, 264/DIG.48, 96/15, 96/66, 128/206.19, 128/205.29, 442/340, 442/351, 307/400, 428/172
• US Class Current: 96/15
• CPC Class Codes: A62B 23/025 the filter having substantially the shape of a mask surgical face masks A41D13/11
• CPC Class Codes: B01D 2239/0225 Side-by-side
• CPC Class Codes: B01D 2239/0233 Island-in-sea
• CPC Class Codes: B01D 2239/0407 comprising particulate additives, e.g. adsorbents apparatus incorporating gas filtering material B01D46/0036
• CPC Class Codes: B01D 2239/0435 Electret apparatus incorporating such gas filtering material B01D46/0032
• CPC Class Codes: B01D 2239/0618 Non-woven
• CPC Class Codes: B01D 2239/0622 Melt-blown
• CPC Class Codes: B01D 2239/064 The fibres being mixed
• CPC Class Codes: B01D 2239/065 More than one layer present in the filtering material apparatus incorporating such gas filtering material B01D2275/10
• CPC Class Codes: B01D 2239/0654 Support layers
• CPC Class Codes: B01D 2239/0663 The layers being joined by hydro-entangling
• CPC Class Codes: B01D 2239/069 Special geometry of layers
• CPC Class Codes: B01D 2239/10 Filtering material manufacturing
• CPC Class Codes: B01D 2239/1233 Fibre diameter
• CPC Class Codes: B01D 2239/1291 Other parameters
• CPC Class Codes: B01D 39/08 Filter cloth, i.e. woven, knitted or interlaced material metallic B01D39/10
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: D04H 1/407 containing absorbing substances, e.g. activated carbon
• CPC Class Codes: D04H 1/4291 Olefin series
• CPC Class Codes: D04H 1/43828 sheath-core
• CPC Class Codes: D04H 1/43835 : Mixed fibres, e.g. at least two chemically different fibres or fibre blends
• CPC Class Codes: D04H 1/43838 : Ultrafine fibres, e.g. microfibres
• CPC Class Codes: D04H 1/492 : by fluid jet D04H1/49 takes precedence
• CPC Class Codes: D04H 1/56 : in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: D06M 10/025 : Corona discharge or low temperature plasma
• CPC Class Codes: D06M 11/05 : with water, e.g. steam; with heavy water
• CPC Class Codes: D06M 2101/18 : Synthetic fibres consisting of macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: Y10S 264/48 : Processes of making filters
• CPC Class Codes: Y10S 55/05 : Methods of making filter
• CPC Class Codes: Y10S 55/35 : Respirators and register filters
• CPC Class Codes: Y10S 55/39 : Electrets separator
• CPC Class Codes: Y10T 442/626 : Microfiber is synthetic polymer

Abstract

Electret filter media comprising a nonwoven web of thermoplastic nonconductive microfibers having trapped charge, said charge provided by (1) subjecting the nonwoven web to a corona treatment, followed by (2) impingement of jets of water or a stream of water droplets on the web at a pressure sufficient to provide the web with filtration enhancing electret charge and (3) drying the web. This electret filter media may be used in a respiratory mask to provide extraordinarily good filtration properties.

Claims

1. Electret filter media comprising a nonwoven web of thermoplastic nonconductive microfibers having trapped charge, said charge provided by (1) subjecting the nonwoven web to a corona treatment, followed by (2) impingement of jets of water or a stream of water droplets on the web at a pressure sufficient to provide the web with filtration enhancing electret charge and (3) drying the web.

2. A resilient cup-shaped filtration face mask adapted to cover the nose and mouth of the wear of the mask comprising a nonwoven web of thermoplastic nonconductive microfibers having trapped charge, said charge provided by (1) subjecting the nonwoven web to a corona treatment, followed by (2) impingement of jets of water or a stream of water droplets on the web at a pressure sufficient to provide the web with filtration enhancing electret charge and (3) drying of the web.

3. A respirator mask assembly comprising a facepiece comprising at least an inhalation port, inhalation valve, and inhalation filter and at least one exhalation port and exhalation valve, a face seal supported by the face piece and a harness for supporting the facepiece on a wearer'"'"'s head, said inhalation filter comprising a nonwoven web of thermoplastic nonconductive microfibers having trapped charge, said charge provided by (1) subjecting the nonwoven web to a corona treatment, followed by (2) impingement of jets of water or a stream of water droplets on the web at a pressure sufficient to provide the web with filtration enhancing electret charge and (3) drying of the web.

4. A nonwoven web that contains nonconductive thermoplastic microfibers and that has an electric charge imparted thereto by the steps comprising:

(1) subjecting the nonwoven web that contains nonconductive thermoplastic microfibers to a corona treatment, followed by (2) contacting the nonconductive nonwoven web that contains thermoplastic microfibers with water in manner sufficient to provide the nonwoven web with filtration enhancing electret charge, and then (3) drying the nonwoven web.

5. The product of claim 4, wherein the thermoplastic microfibers are polypropylene microfibers, poly(4-methyl-1-pentene) microfibers, or blends thereof.

6. The product of claim 4 wherein the thermoplastic microfibers comprise polypropylene and poly(4methyl-1-pentene).