WO2001054796A2

WO2001054796A2 - Impregnated filter

Info

Publication number: WO2001054796A2
Application number: PCT/US2001/002348
Authority: WO
Inventors: Ronald P. Rohrbach; Daniel Bause; Gordon W. Jones; Peter D. Unger
Original assignee: Honeywell International Inc.
Priority date: 2000-01-27
Filing date: 2001-01-25
Publication date: 2001-08-02
Also published as: EP1251930A2; WO2001054796A3; JP2003520669A

Abstract

A filter medium for an air filtration system is described. The filter medium includes at least one fiber having a liquid or solid material disposed on an external surface thereof. The fiber can include structures such as an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to the outer fiber formed between adjacent lobes. The material, which can be disposed within the internal cavity of the fiber, has a high affinity for particulate matter in order to strongly attract and retain the particulate matter, while at the same time not causing a substantial pressure drop across the filter medium.

Description

IMPREGNATED FILTER

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to filter media, and more particularly to filter media comprised of a plurality of fibers having a material disposed on an exterior surface thereof for, among other things, selectively attracting and retaining particulate matter.

2. Discussion Conventional filtration systems, especially those employed for air filtration in homes and automobiles, typically employ a filter element comprised of a web, mat, or sheet of filter media in order to trap and retain particulate matter entrained in an air flow that passes through the filter media. Most filtration systems rely on physical entrapment, whereas recently developed ^' filtration systems employ either electrostatically charged fibers (e.g., electrets) or chemically treated fibers (e.g., adhesives and aerogels) in order to attract and retain a greater amount of particulate matter than conventional filtration systems. Additionally, filter manufacturers have begun applying anti-micrpbial agents onto filter media as a way of alleviating the spread of airborne microbes (e.g., "sick- building" syndrome) .

A description of this technology can be found in the following U.S. Patents: U.S. Patent No. 4,976,749 entitled "Air Filter

And Particle Removal System" and issued to Adamski et al . ; U.S. Patent No. 5,091,102 entitled "Method Of Making A Dry Antimicrobial Fabric" and issued to Sheridan; U.S. Patent No. 5,288,298 entitled "Antimicrobial Air Filter And Method Of Making Same" and issued to Aston; U.S. Patent No. 5,308,533 entitled "Aerogel Mesh Getter" and issued to Hotaling et al . ; U.S. Patent No. 5,356,621 entitled "Method For Attracting Flies" and issued to Tabaru et al . ; U.S. Patent No. 5,360,572 entitled "Aerogel Mesh Getter" and issued to Hotaling et al . ; U.S. Patent No. 5,470,612 entitled "Aerogel Mesh Getter" and issued to Hotaling et al . ; U.S. Patent No. 5,747,053 entitled "Antiviral Filter Air Cleaner Impregnated With Tea Extract" and issued to Nashimoto et al . ; and U.S. Patent No. 5,840,245 entitled "Air Filter And Method For Reducing The Amount Of Microorganisms In Contaminated Air" ^' and issued to Coombs et al . , the entire specifications of which are all incorporated herein by reference .

Although conventional filter media, including filters that employ externally coated material, generally perform adequately well, they do not achieve the high level of attraction and retention of particulate matter due to the fact that the material, typically in a liquid phase, in located only in inter-fiber voids, thus reducing the overall void volume and increasing the pressure drop across the filter. Thus, the filter manufacturer is forced into the undesirable position of deciding whether to reduce the amount of liquid phase material applied to the surface of the filter in order to avoid a large pressure drop (thus letting more particulate matter pass through the filter) , or whether to increase the amount of liquid phase material applied to the surface of the filter in order to attract and retain more particulate matter (thus causing a large pressure drop) . This technology also suffers from loss of the liquid phase material either due to gravity or to the phenomenon known as "spit-out."

Therefore, there exists a need for filter media that can, among other things, selectively attract and retain a large amount of particulate matter without causing a large pressure drop across the filter.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved filter media.

It is another object of the present invention to provide a new and improved filter media having a liquid phase material contained therein. It is another object of the present invention to provide a new and improved filter media having a solid phase material contained therein.

It is yet another object of the present invention to provide a new and improved filter media having a liquid phase material contained therein, wherein the liquid phase material attracts and retains a large amount of particulate matter without causing a large pressure drop across the filter.

It is still yet another object of the present invention to provide a new and improved filter media having a solid phase material contained therein, wherein the solid phase material attracts and retains a large amount of particulate matter without causing a large pressure drop across the filter. In accordance with one embodiment of the present invention, a filter medium for attracting and retaining particulate matter is provided, comprising: at least one fiber; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes ; wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

In accordance with another embodiment of the present invention, a filter medium for attracting and retaining particulate matter is provided, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter.

In accordance with yet another embodiment of the present invention, a method for attracting and retaining particulate matter entrained in an air stream is provided, comprising: providing at least one fiber; and passing the air stream through the at least one fiber,- wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

In accordance with still yet another embodiment- of the present invention, a method for for attracting and retaining particulate matter entrained in an air stream is provided, comprising: providing at least one fiber; and passing the air stream through the at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter. A more complete appreciation of the present invention and its scope can be obtained from the following brief description of the drawings, detailed description of the invention, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a perspective view showing a fiber which is suitable for practicing the invention.

DETAILED DESCRIPTION OF THE INVENTION The filter medium of the present invention is primarily intended to be used to filter particulate matter entrained in an air stream. The filter medium can include an optional support member, such as a peripheral cardboard or plastic frame or bracket to support the filter medium, so as to form a filter element .

The present invention is based on the use of a class of fibrous materials which have the ability to capillarily hold an impregnated liquid and/or solid phase material due to the nature of their unique cross-section. This fiber which has this unique cross-section can be made into a variety of particulate filters, either of the woven or nonwoven varieties.

Examples of suitable fibers include, without limitation, elongated fibers having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to the outer fiber formed between adjacent lobes.

A description of several suitable fibers can be found in the following U.S. Patents, the entire specifications of which are all incorporated herein by reference :

U.S. Patent No. 5,057,368 entitled "Filaments Having Trilobal Or Quadrilobal Cross-Sections" and issued to Larg an et al . describes a trilobal or quadrilobal fiber formed from thermoplastic polymers, the fiber having a cross-section comprised of a central core having three or four T-shaped lobes, the legs of each intersecting at the center of the core such that the angle between the legs of adjacent lobes is from about 80° to about 130°.

U.S. Patent No. 5,704,966 entitled "Method And Apparatus For The Continuous Capturing And Removal Of Gas Molecules" and issued to Rohrbach et al . describes a filtration method and device which continuously removes several gas phase contaminants from an air stream through the use of partially hollow wicking fibers impregnated with a selected liquid which can capture the gas phase contaminants . U.S. Patent No. 5,713,971 entitled "Filtration

Device Using Absorption For The Removal Of Gas Phase Contaminants" and issued to Rohrbach et al . describes a filter device and technique which rely on absorption rather than adsorption for the removal of gas phase contaminants . A filter media is composed of a plurality of wicking fibers each of which comprise a strand with a hollow region impregnated with any of a variety of liquid phase absorbing systems made from the combination of a carrier liquid and soluble complexing/degrading agent or agents . The filter media may be made from any of a variety of fibers which can rapidly transport a liquid phase by the nature of either their geometry or their chemical composition. Geometries may include multilobal cross-sectional configurations, porous hollow fibers, porous or striated fibers or tightly bundled microfibers, all of which exhibit the property of wicking fluid from an external, source.

U.S. Patent Nos . 5,744,236 and 5,759,394 entitled "Hollow Fibers Impregnated With Solid Particles" and "Elongate Fiber Filter Mechanically Securing Solid Absorbent Particles Between Adjacent Multilobes", respectively, and both issued to Rohrbach et al . describe a non-woven filter media or mat formed from a plurality of elongated generally hollow fibers each having an internal cavity which has an opening, smaller than the cavity width, to the fiber surface and retaining within the internal cavity a large number of relatively small solid particles . U.S. Patent Nos. 5,902,384 and 5,951,744 entitled "Wicking Fiber With Solid Particulates For A High Surface Area Odor Removing Filter And Method Of Making" and "Multicomponent Depth Odor Control Filter And Method Of Manufacture", respectively, and both issued to Rohrbach et al . describe a filtration device which continuously removes gas phase contaminants from an air stream through the use of partially hollow wicking fibers impregnated with a fine solid carbon powder or zeolites and formed into a fiber filter with a selected chemisoptive liquid applied to one side of the fiber filter and large carbon particles applied to the other side of the fiber filter.

The impregnated or pregnant fibers can either be ^'formed into fibrous mats, sheets, or webs by any number of conventional methods, or alternatively, the pregnant fibers can be mechanically incorporated (e.g., disposed) onto and/or within a conventional fibrous mat, sheet, or web (typically comprised of a plurality of entangled non- woven fibers) . Preferably, the resulting filter media, whether comprised of, or incorporating, pregnant fibers is a low density, high pore volume material (e.g., 50% pore volume for fibers) . The high pore volume is preferred so as to allow the proper level of air flow through the filter media without a significant pressure drop occurring.

The liquid phase material which is, in part, entrapped on the exterior of each fiber can assist in the overall filtration efficiency of the filter. This liquid' phase material adds extra collecting ability of the filter medium (e.g., fibrous mat) beyond simple physical entrapment of the particles . By properly choosing the liquid phase material .so that it- has a high collecting affinity for various particulates, a virtual "fly paper- like" material -can be made. In this manner, one can raise the overall efficiency of the filter by simply using this cross-section with the liquid phase material externally trapped therein. Furthermore, because the liquid phase material is preferably entrapped within the internal cavity of the fiber, it is envisioned that there will not be a substantial pressure drop across the filter medium.

In order to target a particulate type of particle, one would choose that liquid phase material which matches the surface energy and wettability of that particular particle. By way of a non-limiting example, liquid phase materials such as oils can be used for attracting and retaining dust and dirt particles.

Additionally, the present invention has application in customized filtration applications such as the removal of microbes. By way of a non-limiting example, some solvents have strong affinity for microbes such as, but not limited to, polymers such as polyvinylpyridine .

Solid phase materials can be used equally as well as liquid phase materials in order to attract and retain particulate matter without any substantial pressure drop across the filter medium. By way of a non-limiting example, particulates, such as carbon powders can be impregnated into the fibers of the present invention. Additionally, solid phase materials can also be melted into a free flowing state and then applied onto the fiber of the present invention.

Referring now to the FIGURE, a generally hollow fiber 10 which is suitable for practicing this invention is shown. The fiber 10 has a cross-section with a central core 12 and three (or alternatively four) T-shaped lobes 14 that terminate on an external wall member 16. The legs of the lobes 14 intersect at the core 12 so that the angle between the legs of the adjacent lobes 14 is from about 80° to 130°. The thermoplastic polymer is typically a polyamide, a polyester, a polyolefin or a combination thereof. The fiber 10 as illustrated in the FIGURE is formed as an extruded strand having three hollow interior longitudinally extending cavities 18 each of which communicates with the outer strand surface by way of longitudinally extending slots 20 which are defined between the outer ends of the T-shaped lobes 14. The material 22 (either liquid phase and/or solid phase) is applied in any number of conventional methods to at least a portion of one or more surfaces of the cavities 18.

The foregoing description is considered illustrative only of the principles of the invention-. Furthermore, because numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and process shown as described above. Accordingly, all suitable modifications and equivalents that may be resorted to that fall within the scope of the invention as defined by the claims that follow.

Claims

What is claimed is:

1. ^'A filter medium for attracting and retaining particulate matter, comprising: at least one fiber; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

2. The invention according to claim 1, wherein the lobes are T-shaped.

3. The invention according to claim 1, wherein the at least one material does not cause a substantial pressure drop across the filter medium.

4. The invention according to claim 1, wherein the at least one material is selected from the group consisting of liquid phase materials, solid phase materials, and combinations thereof.

5. A filter medium for attracting and retaining particulate matter, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter.

6. The invention according to claim 5, wherein the lobes are T-shaped.

7. The invention according to claim 5 , wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

8. The invention according to claim 5, wherein the at least one material does not cause a substantial pressure drop across the filter medium.

9. The invention according to claim 5, wherein the at least one material is selected from the group consisting of liquid phase materials, solid phase materials, and combinations thereof.

10. A method for attracting and retaining particulate matter entrained in an air stream, comprising: providing at least one fiber; and passing the air stream through the at least one fiber; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

11. The invention according to claim 10, wherein the lobes are T-shaped.

12. The invention according to claim 10, wherein the at least one material does not cause a substantial pressure drop across the filter medium.

13. The invention according to claim 10, wherein the at least one material is selected from the group consisting of liquid phase materials, solid phase materials, and combinations thereof.

14. A method for for attracting and retaining particulate matter entrained in an air stream, comprising: providing at least one fiber; and passing the air stream through the at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the particulate matter.

15. The invention according to claim 14, wherein the lobes are T-shaped.

16. The invention according to claim 14, wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

17. The invention according to claim 14, wherein the at least one material does not cause a substantial pressure drop across the filter medium.

18. The invention according to claim 14, wherein the at least one material is selected from the group consisting of liquid phase materials, solid phase materials, and combinations thereof.