Filter media construction with nanofiber and carbon web

Abstract

Disclosed herein, among other things, is an improved filter media construction that comprises multiple layers for improved odor control that can be used for vacuum cleaner air filtration cartridge applications. The filter media comprises anti-microbial ePTFE HEPA filter media to prevent mold growth. The filter media may also be used for air cleaner filtration, central air filtration for home and industrial buildings (HVAC), cleanrooms, and microelectronic devices. In an embodiment, the improved filter media construction comprises at least a PTFE layer, a bi-component layer, and a base layer. In an embodiment the PTFE layer comprises ePTFE. In an embodiment, the bi-component layer comprises non-woven polyethylene/polyethylene terephthalate (PE/PET). In yet another embodiment, the base layer comprises activated carbon. Other aspects and embodiments are provided herein.

Claims

1. A multi-layer filter media construction comprising: an upstream media layer comprising nanofiber, a bi-component layer comprising non-woven polyethylene/polyethylene terephthalate, and a base layer, wherein the upstream media layer is bonded to the base layer by the bi-component layer.

2. The filter media construction of claim 1, the base layer comprising activated carbon.

3. The filter media construction of claim 2 wherein the base layer comprises a minimum of 45% activated carbon.

4. The filter media construction of claim 2, the base layer further comprising nanofiber.

5. The filter media construction of claim 1, the base layer comprising carbon loaded melt-blown media.

6. The filter media construction of claim 5, the base layer further comprising nanofiber.

7. A method for making a three-layer filter media construction comprising: bonding an upstream media layer to a base layer using a bi-component layer under heat and pressure, wherein the upstream media layer comprises nanofiber and wherein the bi-component layer comprising non-woven polyethylene/polyethylene terephthalate.

8. The method of claim 7, the base layer comprising activated carbon.

9. The method of claim 8, wherein the base layer comprises a minimum of 45% activated carbon.

10. The method of claim 8, wherein the base layer further comprises nanofiber.

11. The method of claim 7, the base layer comprising carbon loaded melt-blown media.

12. The method of claim 11, the base layer further comprising nanofiber.

13. A multi-layer filter media construction comprising: an upstream media layer comprising nanofiber, a bi-component layer comprising non-woven polyethylene/polyethylene terephthalate, and a base layer comprising carbon loaded nanofiber.

14. The filter media construction of claim 13, wherein the base layer comprises a minimum of 45% activated carbon.

15. The filter media construction of claim 13, wherein the filter media construction further comprises an anti-microbial treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention may be more completely understood in connection with the following drawings, in which:

(2) FIG. 1 is a schematic front perspective view of the filter construction in accordance with the present invention.

(3) FIG. 2 is a cross sectional view of a multi-layered filter media in accordance with an embodiment of the invention.

(4) FIG. 3 is a scanning electron microscope micrograph of the filter media shown in FIG. 2.

(5) FIG. 4 is a cross sectional view of a multi-layered filter media in accordance with an embodiment of the invention.

(6) FIG. 5 is a cross sectional view of a multi-layered filter media in accordance with an embodiment of the invention.

(7) FIG. 6 is a cross sectional view of a multi-layered filter media in accordance with an embodiment of the invention.

(8) FIG. 7 is a cross sectional view of a multi-layered filter media in accordance with an embodiment of the invention.

(9) FIG. 8A shows test results from conducting off-gassing tests where media made in accordance with the invention was challenged with ammonia

(10) FIG. 8B shows test results from conducting off-gassing tests where media made in accordance with the invention was challenged with H.sub.2S.

(11) FIG. 9 shows the fractional efficiency for two different samples of the media used in an embodiment of the invention.

(12) While the invention is susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the invention is not limited to the particular embodiments described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(13) The market for general-purpose vacuum cleaners and for wet/dry vacuum systems has imposed increasingly high standards of performance for the vacuum cleaners and their filters over recent years. The devices are required to remove greater and greater proportions of smaller and smaller particles from streams obtained by the vacuum cleaner from often-harsh wet or dry environments in the home, garage, basement, shop, yard, and a variety of industrial environments. The increased requirements satisfy needs for improved health, reduced allergies, improved cleanability, reduced ambient particle counts, and other requirements for home, shop, and industrial environments.

(14) The prior art filter media has had adequate performance in assigned roles in filtration equipment and processes. However, these media all suffer from various problems. At present, filter technology provides odor control, but improved odor control is desired. Damp filters often facilitate unwanted mold and mildew growth on the filters. The mold in turn produces mold spores, which can add pollution to the air. Additionally, it is typical that filters that can achieve a desired efficiency for residential or other non-industrial applications often result in a pressure drop across the filter media that is too high for the applications.

(15) The present invention provides a multi-layered anti-microbial ePTFE HEPA filter media for improved odor control. The media is specifically designed for vacuum cleaner air filtration cartridge application, but it can also be used for a variety of other filtration systems. Such systems include but are not limited to air cleaner filtration, central air filtration for home and industrial buildings (HVAC), cleanrooms, and microelectronic devices.

(16) Filter Construction

(17) Referring to FIG. 1, the filter media construction 10 of an example embodiment comprises at least three layers: an upstream media layer 20, a bi-component (PE/PET) layer 30, and a base layer 40. In use, air flow starts from the upstream media layer 20, passes through the bi-component layer 30, and exits through the base layer 40.

(18) In one embodiment, PTFE is used for the upstream media layer 20. In a typical embodiment, the PFTE used for the upstream media layer 20 is expanded PTFE (ePTFE). The ePTFE film layer provides several important benefits to the filtration media, including optional HEPA efficiency and tap cleanability with minimal pressure drop at HEPA efficiency. HEPA efficiency is defined as a minimum 99.97% at 0.3 micron particles (U.S. standard).

(19) In one embodiment, the base layer 40 comprises an activated carbon layer, and the upstream media layer 20 is ePTFE. In another embodiment, the activated carbon layer comprises a minimum of 45% activated carbon. The ePTFE filtration layer is bonded using a low melt bi-component layer 30 with carbon based media under heat and pressure.

(20) FIG. 2 shows one embodiment of the present invention where the upstream media layer 20 comprises ePTFE film, the bi-component layer 30 is non-woven PE/PET, and the base layer 40 comprises activated carbon. The bi-component layer 30 may be treated with an anti-microbial substance. As shown in FIG. 2, the bi-component layer 30 may also be alternatively formed using a low melt adhesive web. Additionally, the base layer activated carbon may be treated with an anti-microbial substance. FIG. 3 shows a scanning electron microscope micrograph of the filter media shown in FIG. 2.

(21) In one embodiment, the base layer 40 comprises activated carbon and nanofiber, and the upstream media layer 20 is PTFE, as shown in FIG. 4.

(22) In one embodiment, the base layer 40 is melt-blown media with carbon particles, and the upstream media layer 20 is PTFE, as shown in FIG. 5.

(23) In one embodiment, the base layer 40 is particle laden melt-blown nanofiber with carbon particles, and the upstream media layer 20 is PTFE, as shown in FIG. 6.

(24) In one embodiment, the base layer 40 is particle laden melt-blown material further containing carbon particles, and the upstream media layer 20 is nanofiber created by Donaldson Company, Inc. of Bloomington, Minn. This embodiment is shown in FIG. 7. In one embodiment, the nanofiber may be coated on one side. In another embodiment, the nanofiber may be coated on two sides. In the various embodiments nanofiber media may be co-pleated with other media, such as carbon loaded melt blown media.

(25) Exemplary Materials

(26) The present invention may be constructed with a variety of materials. HEPA filtering material is preferred as, by definition, HEPA filters remove at least 99.97% of airborne particles 0.3 μm in diameter. However, due to the construction of the filter, the starting materials used to construct the filters of the present invention need not be HEPA efficiency in order for the entire filter media construction to be HEPA efficiency. In one embodiment, polytetrafluoroethylene (PTFE) is used for the upstream media layer. Expanded PTFE (ePTFE) may also be utilized in the present invention. Typically, ePTFE media have very high pressure drops and moderate HEPA efficiency.

(27) Alternatively, as shown in FIG. 7, the upstream media layer 20 may comprise nanofiber, such as that created by Donaldson Company, Inc. of Bloomington, Minn. These nanofibers provide a low cost option with mid-range filtration efficiency. Examples of these nanofibers include some coated on one side and others coated on two sides, co-pleated or bonded with melt-blown carbon media. The melt-blown carbon media is available from a variety of commercial sources, such as Hollingsworth and Vose of East Walpole, Mass.

(28) In one embodiment, the bi-component layer 30 may comprise polyethylene/polyethylene terephthalate (PE/PET). In another embodiment, the bi-component layer 30 may comprise a low melt adhesive web.

(29) In one embodiment, the base layer 40 comprises activated carbon. In a preferred embodiment, the base layer 40 comprises a minimum of 45% activated carbon. The base layer may be produced with or without anti-microbial treatment. Alternatively, the base layer 40 comprises nanofiber with activated carbon. In this application, the nanofibers serve a multifunctional purpose: in addition to helping to capture airborne contaminants that escape ePTFE film, the nanofibers cause the overall pressure drop to be lower than if PTFE film alone is used. Consequently, use of these materials does not necessitate that the starting PTFE film be HEPA efficiency.

(30) In another embodiment, the base media 40 comprises melt-blown media with carbon particles. The melt-blown media with carbon particles serves dual purposes: not only does it aid control odor, it also helps to capture airborne contaminants that escape the ePTFE film layer. Furthermore, the overall pressure drop is lower than if PTFE film alone is used, so the starting PTFE film need not be HEPA efficiency.

(31) In yet another embodiment, the base media 40 comprises carbon particle laden melt-blown media with nanofibers. Such a material is suitable for removing odor with lower pressure drop and higher efficiency. The starting PTFE film of this embodiment need not be HEPA efficiency.

(32) One exemplary material that may be used for the base media 40 is a 2-in-1 carbon substrate developed by Lydall, Inc. of Manchester, Conn. An example of such a material is C-680 ActiPure® media developed by Lydall, Inc. of Manchester, Conn. The ActiPure® media comprises a non-woven material and activated carbon.

(33) Interbasic Resources Inc. (IBR) performed efficiency and off-gassing tests on media, which is shown in FIGS. 8A and 8B. These tests were developed by IBR for vacuum odor control. For the off-gassing tests, the media was challenged with ammonia and H.sub.2S.

(34) FIG. 8A shows the test results from conducting off-gassing tests where the media was challenged with ammonia in order to determine offgassing from a loaded vacuum cleaner filter under static conditions. The contaminant used in the off-gassing test was 50 grams of IEC 60312 household test dust saturated with ammonia at 200 ppm(v). The tests were conducted at 70 degrees Fahrenheit with a relative humidity of 48% and barometric pressure of 736 mmHg. The media samples tested were 12″×12″ flat sheet media formed into a pocket and filled with 50 grams of dust.

(35) FIG. 8B shows the test results from conducting off-gassing tests where the media was challenged with ammonia in order to determine offgassing from a loaded vacuum cleaner filter under static conditions. In these tests, the contaminant used in the off-gassing test was 50 grams of IEC 60312 household test dust saturated with H.sub.2S at 200 ppm(v). The tests were conducted at 71 degrees Fahrenheit with a relative humidity of 47% and barometric pressure of 739 mmHg. The media samples tested were 12″×12″ flat sheet media formed into a pocket and filled with 50 grams of dust.

(36) Another exemplary material for use in the base media 40 shown in FIG. 9 shows the fractional efficiency of the material for two different samples of the media.

(37) Additionally, the filter media 10 may be treated in any number of ways to improve its efficiency in removing minute particulates and for other purposes. For example, electrostatically treated media can be used, as can cellulose media having one or more layers of fine fiber, or other types of media known to those skilled in the art. The filter media 10 may also be treated with anti-microbial substances to prevent the growth of mold on the filters. Anti-viral or anti-mycotic agents may also be used to treat the filter media 10 to reduce the populations of infectious agents.

(38) It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

(39) It should also be noted that, as used in this specification and the appended claims, the phrase “configured” describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration. The phrase “configured” can be used interchangeably with other similar phrases such as “arranged”, “arranged and configured”, “constructed and arranged”, “constructed”, “manufactured and arranged”, and the like.

(40) All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

(41) This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.