Filter media construction using ptfe film and carbon web for hepa efficiency and odor control

[Cross-reference of related applications] This application was filed on July 22, 2010 by Donaldson Company, Inc. (applicant for designation in all countries except the United States) and Kirit Patel (application for designation in the United States only), a US citizen. It is filed as a PCT international patent application in the name of (person), claiming priority over US Provisional Patent Application No. 61 / 227,784 filed on July 22, 2009, and this provisional patent application. The contents of are incorporated herein by reference.

The present invention generally relates to a laminated filter medium.

Allergic and respiratory patients are often sensitive to particulate matter in the air. Vacuum cleaners and air purifiers Filtration devices seek to remove particulate matter at home and at work and require filters to capture these particles. Without such a filter, the vacuum cleaner would simply return the particulate matter back into the air and recirculate it. As regulatory requirements for industrial dust collectors become more stringent, there is a need to remove smaller and smaller particles from the process air stream at a higher rate. Gas turbine intake filtration systems must also remove a large number of very small particles, as the presence of such particles can cause irreparable damage to the turbine blades. For the cleanliness of the environment, the health of its residents, the efficiency of industrial processes, the maintenance of industrial equipment, and the overall beauty of life, submicron particulate matter needs to be immediately filtered out of the air stream. ..

To achieve the removal of submicron particles from the airflow through such a system, the inertial separator simply provides a physical barrier in the path of the particulate matter, then collides the particulate matter and traps it from the airflow. In many cases, it is simply put in a collection bottle. The paper bag dust collector is nothing more than a filter based on the paper filter technology in the form of a bag. Such paper bags are typically simply mounted across the air stream to separate the particles from the air stream.

Newer filters have been designed with collection filters or flat or cylindrical cartridges. HEPA filter media are used in these applications. By definition, HEPA filters remove at least 99.97% of levitating particles larger than 0.3 μm in diameter. Due to their general reliability and high level of performance, HEPA filters are often used to minimize the release of radioactive materials, asbestos, lead, beryllium, and other toxic particulates. In vacuum cleaners, HEPA filters are used for air pollution control. Often, HEPA structures include a foamed PTFE (ePTFE) layer in combination with a layer of melt-blow fibers in the filter construction, or a cellulose filter paper layer in combination with a layer of melt-blow fibers in the filter construction. These structures are often cleaned by tapping the filter or by blowing filter cakes or particulates off the filter using a compressed air stream.

Filtration efficiency and cleanliness of newer filters are important. These filters must be able to remove dust and dirt, but must be easily clean without damaging the filters. In many cases, cleaning a dirty filter by hitting a hard object with the filter to remove dust and dirt can cause the filter medium to fail or delaminate the multilayer elements. As a result, the formation of dust and dirt paths through the filter structure can cause the filter to fail. Another failure mode occurs when fine dust particles are trapped deep inside the filter medium, making it impossible for dust to be removed by typical filter cleaning mechanisms, resulting in reduced vacuum force. However, the filter life will be shortened.

An example of dust filter vacuum cleaner technology using a fine fiber layer in a vacuum cleaner bag is Patent Document 1 of Emig et al. An example of a filter cartridge in a wet / dry vacuum cleaner using foamed PTFE is Patent Document 2 of Scanlon et al. Filter materials such as scrimmed HEPA media often have high efficiencies, but often have a short service life and can be degraded by water exposure.

<p num="0008"><patcit num="1"><text>U.S. Pat. No. 6,395,046</text></patcit><patcit num="2"><text>U.S. Pat. No. 5,783,086</text></patcit></p>

<p num="0009"> There is still a need for a filter medium construct suitable for removing odors while maintaining a smaller pressure drop and higher efficiency. In addition, there is a need for filter medium constructs that provide HEPA efficiency, odor control, and antimicrobial treatment in a single medium to control mold growth in cartridge media.</p>

<p num="0010"> The present invention generally relates to multi-layer HEPA filter media for improved odor control and filtration. The present invention provides a multi-layer antimicrobial ePTFE HEPA filter medium for improved odor control. This medium is specifically designed for vacuum cleaner air filtration cartridge applications, but it can also be used in a variety of other filtration systems. Such systems include, but are not limited to, air purifier filtration, central air filtration (HVAC) for residential and industrial buildings, clean rooms, and microelectronic devices.</p><p num="0011"> The filter medium construct typically comprises at least three layers: an upstream medium layer, a two-component polyethylene / polyethylene terephthalate (PE / PET) layer, and a base layer. In one embodiment, PTFE is used for the upstream media layer. In another embodiment, the PFTE used for the upstream medium layer is foamed PTFE (ePTFE). The ePTFE film layer offers a number of important advantages for the filtration medium, including HEPA efficiency and tap cleanability with minimal pressure drop at HEPA efficiency. In one embodiment, the binary layer comprises non-woven polyethylene / polyethylene terephthalate (PE / PET). In certain embodiments, the base layer comprises activated carbon.</p><p num="0012"> This overview is an overview of some of the teachings of this application and is not intended to be an exclusive or comprehensive treatment of the subject matter. Further details can be found in the detailed description and the appended claims. Other aspects will become apparent to those skilled in the art by reading and understanding the detailed description below and considering the drawings that make up a portion thereof, each of which is construed in a limited sense. Should not be. The scope of the present invention is defined by the appended claims and their legal equivalents.</p><p num="0013"> The present invention may be more fully understood in connection with the drawings below.</p>

<figref num="1">It is a schematic front view of the filter structure according to this invention.</figref><figref num="2">FIG. 5 is a cross-sectional view of a multilayer filter medium according to one embodiment of the present invention.</figref><figref num="3">It is a scanning electron microscope micrograph of the filter medium shown in FIG.</figref><figref num="4">FIG. 5 is a cross-sectional view of a multilayer filter medium according to one embodiment of the present invention.</figref><figref num="5">FIG. 5 is a cross-sectional view of a multilayer filter medium according to one embodiment of the present invention.</figref><figref num="6">FIG. 5 is a cross-sectional view of a multilayer filter medium according to one embodiment of the present invention.</figref><figref num="7">FIG. 5 is a cross-sectional view of a multilayer filter medium according to one embodiment of the present invention.</figref><figref num="8A">The test result which carried out the outgassing test (off-gassing test) which challenged the medium produced according to this invention with ammonia is shown.</figref><figref num="8B">The medium prepared according to the present invention is H.₂The test result of the gas emission test challenged in S is shown.</figref><figref num="9">It shows the sorting efficiency for two different samples of the medium used in one embodiment of the present invention.</figref>

Various modifications and alternative forms of the present invention are possible, the particular ones of which are shown, by way of example, in the drawings and will be described in detail. However, it should be understood that the invention is not limited to the particular embodiments described. On the contrary, the invention is intended to include variants, equivalents, and alternatives that fall within the spirit and scope of the invention.

The market for general purpose vacuum cleaners and wet / dry vacuum cleaner systems has imposed higher performance standards on vacuum cleaners and their filters over the last few years. These devices produce an ever-increasing proportion of smaller particles from streams obtained by vacuum cleaners from often harsh moist or dry environments in homes, parking lots, basements, stores, gardens, and various industrial environments. Is required to be removed with. This growing demand meets the need for improved health, reduced allergies, improved cleanliness, reduced total ambient particles, and other requirements for residential, store and industrial environments.

Prior art filter media have had adequate performance in their assigned roles in filtration equipment and methods. However, all of these media have various problems. At present, although filter technology provides odor control, improved odor control is desired. Wet filters often promote the growth of unwanted and mildew on the filters. This mold in turn produces mold spores, which can pollute the air. Moreover, filters that can typically achieve the desired efficiency for residential or other non-industrial applications often result in a pressure drop across the filter medium that is too large for that application.

The present invention provides a multi-layer antimicrobial ePTFE HEPA filter medium for improved odor control. This medium is specifically designed for vacuum cleaner air filtration cartridge applications, but it can also be used in a variety of other filtration systems. Such systems include, but are not limited to, air purifier filtration, central air filtration (HVAC) for residential and industrial buildings, clean rooms, and microelectronic devices.

Filter construct Referring to FIG. 1, the filter medium construct 10 of the embodiment includes at least three layers, an upstream medium layer 20, a two-component (PE / PET) layer 30, and a base layer 40. In use, the airflow starts from the upstream medium layer 20, passes through the binary layer 30, and exits through the base layer 40.

In one embodiment, PTFE is used for the upstream media layer 20. In one typical embodiment, the PFTE used for the upstream medium layer 20 is foamed PTFE (ePTFE). The ePTFE film layer offers a number of important advantages for filtration media, including optional HEPA efficiency and light tap cleanliness with minimal pressure drop at HEPA efficiency. HEPA efficiency is defined as a minimum of 99.97% for 0.3 micrometer particles (US GAAP).

In one embodiment, the base layer 40 comprises an activated carbon layer and the upstream medium layer 20 is ePTFE. In another embodiment, the activated carbon layer comprises at least 45% activated carbon. The ePTFE filtration layer is bonded to a carbon-based medium using a low melt binary layer 30 under heat and pressure.

FIG. 2 shows one embodiment of the present invention in which the upstream medium layer 20 contains an ePTFE film, the binary layer 30 is a non-woven PE / PET, and the base layer 40 contains activated carbon. The binary layer 30 can be treated with an antimicrobial agent. As shown in FIG. 2, the binary layer 30 can also be formed by using a low melt adhesive web as an alternative. In addition, the base layer activated carbon can be treated with antimicrobial material. FIG. 3 shows a scanning electron microscope micrograph of the filter medium shown in FIG.

In one embodiment, as shown in FIG. 4, the base layer 40 contains activated carbon and nanofibers and the upstream medium layer 20 is PTFE.

In one embodiment, as shown in FIG. 5, the base layer 40 is a melt blow medium containing carbon particles and the upstream medium layer 20 is PTFE.

In one embodiment, as shown in FIG. 6, the base layer 40 is particle laden melt blow nanofibers containing carbon particles and the upstream medium layer 20 is PTFE.

In one embodiment, the base layer 40 is a particle-rich melt blow material further containing carbon particles, and the upstream medium layer 20 is nanofibers produced by Donaldson Company, Inc. (Bloomington, Minnesota). .. This embodiment is shown in FIG. In one embodiment, the nanofibers can be coated on one side. In another embodiment, the nanofibers can be coated on both sides. In various embodiments, the nanofiber medium can be co-pleated with other media (eg, carbon-blended melt blow media).

Illustrative material The present invention can be constructed using a variety of materials. By definition, HEPA filters are preferred because they remove at least 99.97% of levitated particles with a diameter of 0.3 μm. However, because it is a filter construct, the entire filter medium construct can be HEPA efficient, even if the starting material used to build the filters of the present invention is not HEPA efficient. In one embodiment, polytetrafluoroethylene (PTFE) is used for the upstream media layer. Foamed PTFE (ePTFE) can also be utilized in the present invention. Typically, the ePTFE medium has a very large pressure drop and moderate HEPA efficiency.

Alternatively, as shown in FIG. 7, the upstream medium layer 20 may include nanofibers (eg, nanofibers produced by Donaldson Company, Inc. (Bloomington, Minnesota)). These nanofibers offer a low cost option with moderate filtration efficiency. Examples of such nanofibers include one-sided coated ones and two-sided coated ones that are folded or bonded together with a melt blow carbon medium. Melt blow carbon media are available from a variety of commercial sources (eg, Hollingsworth and Vose (East Walpole, Massachusetts)).

In one embodiment, the binary layer 30 may comprise polyethylene / polyethylene terephthalate (PE / PET). In another embodiment, the binary layer 30 may include a low melt adhesive web.

In one embodiment, the base layer 40 comprises activated carbon. In one preferred embodiment, the base layer 40 comprises at least 45% activated carbon. The base layer can be produced with or without antimicrobial treatment. Alternatively, the base layer 40 contains nanofibers along with activated carbon. In the present application, the nanofibers have a multifunctional purpose, and in addition to helping to capture levitating contaminants escaped from the ePTFE film, the nanofibers are more than if the PTFE film alone is used. Reduce the overall pressure drop. Therefore, the use of these materials eliminates the need for the starting PTFE film to be HEPA efficient.

In another embodiment, the base medium 40 includes a melt blow medium containing carbon particles. Melt blow media containing carbon particles serve two purposes. This not only helps control odors, but also helps capture airborne contaminants that have escaped the ePTFE film layer. Moreover, the starting PTFE film does not need to be HEPA efficient, as the overall pressure drop will be smaller than if only the PTFE film was used.

In yet another embodiment, the base medium 40 comprises a carbon particle-rich melt blow medium containing nanofibers. Such materials have smaller pressure reduction and higher efficiency and are suitable for removing odors. The starting PTFE film of this embodiment need not be HEPA efficient.

One exemplary material that can be used for the base medium 40 is a two-in-1 carbon support developed by Lydall, Inc. (Manchester, Connecticut). An example of such a material is the C-680 ActiPure® medium developed by Lydall, Inc. (Manchester, Connecticut). This ActiPure® medium comprises a non-woven material and activated carbon.

Interbasic Resources Inc. (IBR) conducted efficiency and gas emission tests on the medium. This is shown in Figures 8A and 8B. These tests are tests developed by IBR for controlling the odor of vacuum cleaners. For gas emission tests, the medium is ammonia and H₂I was challenged with S.

FIG. 8A shows the results of a gas emission test in which the medium was challenged with ammonia to measure gas emissions from a filled vacuum cleaner filter under static conditions. The pollutant used in the gas emission test was 50 g of household dust for IEC 60312 test saturated with 200 ppm (volume) of ammonia. This test was performed at 70 degrees Fahrenheit with a relative humidity of 48% and a pressure of 736 mmHg. The medium sample tested was a pocket-shaped 12 "x 12" (30.48 cm x 30.48 cm) flat sheet medium filled with 50 grams of dust.

FIG. 8B shows the results of a gas emission test in which the medium was challenged with ammonia to measure gas emissions from a filled vacuum cleaner filter under static conditions. The pollutants used in the gas emission test were 200 ppm (volume) of H in this test.₂It was 50 g of S-saturated household dust for IEC 60312 testing. This test was performed at 71 degrees Fahrenheit with a relative humidity of 47% and a pressure of 739 mmHg. The medium sample tested was a pocket-shaped 12 "x 12" (30.48 cm x 30.48 cm) flat sheet medium filled with 50 grams of dust.

Another exemplary material for use in the base medium 40 shown in FIG. 9 shows the fractionation efficiency of this material for two different samples of that medium.

In addition, the filter medium 10 can be processed in any number of ways to improve the efficiency of removing fine particles and for other purposes. Electrostatically treated media can be used, for example, just as cellulosic media with one or more microfiber layers or other types of media known to those of skill in the art can be used. The filter medium 10 can also be treated with an antimicrobial agent to prevent the growth of mold on the filter. Antiviral or antibacterial agents can also be used to treat the filter medium 10 to reduce the population of infectious agents.

As used herein and in the appended claims, the singular forms "one (a)", "one (an)" and "the" are clearly different in content. Note that it includes references to multiple references unless instructed to do so. It should also be noted that the term "or" is generally used to include "and / or (and / or)" unless the content clearly indicates something else. ..

As used herein and in the appended claims, the phrase "configured" is a system constructed or configured to perform a particular task or adopt a particular configuration. It should also be noted that the device, or other structure, is described. The phrase "composed" is another similar phrase (eg, "arranged", "arranged, composed", "constructed, arranged", "constructed". , "Manufactured, placed, etc.") and can be used interchangeably.

All documents and patent applications herein indicate the level of one of ordinary skill in the art involved in the present invention. All documents and patent applications are incorporated herein by reference to the same extent as if each individual document or patent application were specifically and individually indicated by reference.

The present application is intended to include modifications or variants of the subject matter. It should be understood that the above description is intended to be exemplary and not intended to be limiting. The scope of this subject matter should be determined with reference to the appended claims, along with the full scope of the equivalents to which the claims are entitled.