# US 11,077,394 B2 · Electret-containing filter media

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- Number: US 11,077,394 B2
- Document ID: US11077394B2
- Status: Granted
- Kind: B2
- Application number: 15/438,042
- Filed: 2017-02-21
- Published: 2018-08-23
- Granted: 2021-08-03
- Earliest claimed: 2017-02-21
- Assignees: Hollingsworth & Vose Company
- Applicants: Hollingsworth & Vose Company
- Inventors: Bruce Smith
- Web page: https://patentgrep.com/patent/US11077394B2

## CPC

- B01D 39/1623: {of synthetic origin}
- B03C 3/28: Plant or installations without electricity supply, e.g. using electrets
- B32B 3/30: characterised by a layer formed with recesses or projections, e.g. {hollows, grooves, protuberances, ribs (apertured layer B32B3/266; layer with cavities or internal voids B32B3/26)}
- B32B 5/022: {Non-woven fabric}
- B32B 5/024: {Woven fabric}
- B32B 5/028: {Net structure, e.g. spaced apart filaments bonded at the crossing points}
- B32B 5/06: characterised by a fibrous {or filamentary} layer {mechanically connected, e.g. by needling} to another layer, e.g. of fibres, of paper
- B32B 5/08: the fibres or filaments of a layer being of different substances {, e.g. conjugate fibres, mixture of different fibres}
- B32B 5/26: another layer {next to it} also being fibrous or filamentary {(relative arrangement of fibres or filaments of different layers B32B5/12)}
- B32B 7/12: using interposed adhesives or interposed materials with bonding properties
- B01D 35/06: Filters making use of electricity or magnetism (ultrafiltration, microfiltration B01D61/14; electrodialysis, electro-osmosis B01D61/42; devices comprising filters and magnetic separators B03C1/30)
- B01D 46/0032: {using electrostatic forces to remove particles, e.g. electret filters}
- B01D 2239/0241: comprising electrically conductive fibres or particles
- B01D 2239/0435: Electret
- B01D 2239/065: More than one layer present in the filtering material
- B01D 2239/0654: Support layers
- B01D 2239/069: Special geometry of layers
- B01D 2239/1233: Fibre diameter
- B01D 2239/1258: Permeability
- B01D 2239/1291: Other parameters
- B32B 2250/02: 2 layers
- B32B 2250/03: 3 layers
- B32B 2250/20: All layers being fibrous or filamentary
- B32B 2262/02: Synthetic macromolecular fibres
- B32B 2262/0215: Thermoplastic elastomer fibers
- B32B 2262/0223: Vinyl resin fibres
- B32B 2262/023: Aromatic vinyl resin, e.g. styrenic (co)polymers
- B32B 2262/0238: Vinyl halide, e.g. PVC, PVDC, PVF, PVDF
- B32B 2262/0246: Acrylic resin fibres
- B32B 2262/0253: Polyolefin fibres
- B32B 2262/0261: Polyamide fibres
- B32B 2262/0269: Aromatic polyamide fibres
- B32B 2262/0276: Polyester fibres
- B32B 2262/0292: Polyurethane fibres
- B32B 2262/12: Conjugate fibres, e.g. core/sheath or side-by-side
- B32B 2262/14: Mixture of at least two fibres made of different materials
- B32B 2307/204: Di-electric
- B32B 2307/718: Weight, e.g. weight per square meter
- B32B 2307/724: Permeability to gases, adsorption
- B32B 2307/732: Dimensional properties
- B32B 2535/00: Medical equipment, e.g. bandage, prostheses or catheter
- B32B 2571/00: Protective equipment
- D04H 1/498: entanglement of layered webs
- H01G 7/021: {having an organic dielectric}
- H01G 7/028: {having a heterogeneous dielectric}
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B03C: MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS (separating isotopes B01D59/00; combinations of magnetic or electrostatic separation with separation of solids by other means B03B, B07B)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- D04H: MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL (weaving D03; knitting D04B; braiding D04C; net-making D04G; sewing D05B; tufting D05C; finishing non-woven fabrics D06); FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING {; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION}(non-woven fabrics having an intermediate or external layer of a different kind, e.g. of woven fabric, B32B)
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)

## Abstract

Filter media, such as electret-containing filtration media for filtering gas streams (e.g., air), are described herein. In some embodiments, the filter media may be designed to have desirable properties such as stable filtration efficiency over the lifetime of the filter media, increased normalized gamma, relatively low pressure drop (i.e. resistance), and/or relatively low basis weight. In certain embodiments, the filter media may be a composite of two or more types of fiber layers where each layer may be designed to enhance its function without substantially negatively impacting the performance of another layer of the media. For example, one layer of the media may be designed to have a relatively low basis weight and/or a relatively high air permeability, and another layer of the media may be designed to have stable filtration efficiency and/or a relatively high efficiency throughout the filter media's lifetime. The filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment), though the media may also be used in other applications.

## Claims

### Claim 1

A filter media, comprising:
a charged fiber layer;
an open support layer mechanically attached to the charged fiber layer; and
a coarse support layer that holds the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer,
wherein the charged fiber layer has a basis weight of greater than or equal to 12 g/m2 and less than or equal to 250 g/m2,
wherein the open support layer is a mesh,
wherein the mesh comprises a plurality of strands having an average strand diameter of greater than or equal to 500 microns and less than or equal to 2 mm,
wherein the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM, and
wherein the filter media has an overall air permeability of greater than or equal to 10 CFM and less than or equal to 1000 CFM.

### Claim 2 (depends on 1)

The filter media as in claim 1, wherein the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer.

### Claim 3 (depends on 2)

The filter media as in claim 2, wherein the first polymer and the second polymer have different dielectric constants.

### Claim 4 (depends on 2)

The filter media as in claim 2, wherein a difference in dielectric constants between the first polymer and the second polymer is greater than or equal to 0.8 and less than or equal to 8, or greater than or equal to 1.5 and less than or equal to 5.

### Claim 5 (depends on 2)

The filter media as in claim 2, wherein the second polymer is present in the charged fiber layer in an amount of greater than or equal to 10 wt % and less than or equal to 90 wt % versus the total weight of the charged fiber layer.

### Claim 6 (depends on 2)

The filter media as in claim 2, wherein the first polymer is present in the charged fiber layer in an amount of greater than or equal to 10 wt % and less than or equal to 90 wt % versus the total weight of the charged fiber layer.

### Claim 7 (depends on 1)

The filter media as in claim 1, wherein the charged fiber layer has a periodicity of greater than or equal to 10 and less than or equal to 40 waves per 6 inch.

### Claim 8 (depends on 1)

The filter media as in claim 1, wherein the open support layer has a solidity of less than or equal to 10% and greater than or equal to 0.1%.

### Claim 9 (depends on 1)

The filter media as in claim 1, wherein the charged fiber layer is needled to the support layer.

### Claim 10 (depends on 1)

The filter media as in claim 1, wherein the charged fiber layer is needled to the support layer at a punch density of greater than or equal to 15 punches per square centimeter and less than or equal to 60 punches per square centimeter.

### Claim 11 (depends on 1)

The filter media as in claim 1, wherein the open support layer has a strand count along a first axis of greater than or equal to 3 strands per inch and less than or equal to 20 strands per inch.

### Claim 12 (depends on 1)

The filter media as in claim 1, wherein the charged fiber layer has an air permeability of greater than or equal to 10 CFM and less than or equal to 1200 CFM.

### Claim 13 (depends on 1)

The filter media as in claim 1, wherein the open support layer is formed by a spunbond process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 10 microns and less than or equal to 20 microns.

### Claim 14 (depends on 1)

The filter media as in claim 1, wherein the open support layer is formed by a meltblown process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 10 microns.

### Claim 15 (depends on 1)

The filter media as in claim 1, wherein the filter media has an overall basis weight of greater than or equal to 30 g/m2 and less than or equal to 800 g/m2.

### Claim 16 (depends on 1)

The filter media as in claim 1, wherein the filter media has an overall thickness of greater than or equal to 100 mil and less than or equal to 4000 mil.

### Claim 17 (depends on 1)

The filter media as in claim 1, wherein the filter media has an overall air permeability of greater than or equal to 100 CFM and less than or equal to 700 CFM.

### Claim 18 (depends on 1)

The filter media as in claim 1, wherein the filter media has a dust holding capacity of greater than or equal to 5 g/m2 and less than or equal to 600 g/m2.

### Claim 19 (depends on 1)

The filter media as in claim 1, wherein the filter media has a gamma of greater than or equal to 75 and less than or equal to 150.

### Claim 20 (depends on 1)

The filter media as in claim 1, wherein the filter media has an initial efficiency of greater than or equal to 50% and less than or equal to 99.999%.

### Claim 21 (depends on 1)

The filter media as in claim 1, wherein the coarse support layer comprises a plurality of fibers having an average fiber diameter of greater than or equal to 8 micron and less than or equal to 85 microns.

### Claim 22 (depends on 1)

The filter media as in claim 1, wherein the coarse support layer has a basis weight of less than or equal to 100 g/m2 and greater than or equal to 5 g/m2.

### Claim 23 (depends on 1)

The filter media as in claim 1, wherein the filter media comprises an outer layer.