News Column

Researchers Submit Patent Application, "Waved Filter Media and Elements", for Approval

July 3, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Healey, David T. (Bellingham, MA); Gahan, Richard (Wrentham, MA), filed on September 30, 2013, was made available online on June 19, 2014.

The patent's assignee is Hollingsworth & Vose Company.

News editors obtained the following quote from the background information supplied by the inventors: "The removal of air borne particulate contaminants from the air is a concern to everyone. Gas phase particulate filtration has traditionally been accomplished by methods that utilize woven or nonwoven fabrics or webs. The performance of such a system is characterized by the initial efficiency of removal or capture of the particulate as a function of particle size, the initial resistance of the system to air or gas flow as a function of gas flow rate or face velocity, and the way both of these factors change as the filter element loads with the particulate contaminant. One common measurement is the alpha value of a media, which is the product of the pressure drop and the filtration efficiency, and is calculated as follows:

"alpha=-100*log((100-efficiency)/100)/Pressure Drop.

"Generally, it is desirable that a particular filter media have a higher alpha value, as this is indicative that media has a low pressure drop and a high efficiency. For example, the glass materials that are used for ASHRAE bag filters have alpha values (obtained with a DOP challenge) that are in the range of 12-16 (depending upon the particular efficiency of the media), and are not reliant on any type of electrostatic charge to achieve this alpha value. Glass paper can have alpha values of about 12-13, membrane materials can have alpha values of about 20, and nanofiber electrospun materials can have alpha values in the range of about 5-12. None of these materials is reliant on any type of electrostatic charge to achieve these alpha values.

"Filtration media formed from using meltblown, spunbond, carded nonwoven, and wet laid synthetic materials can have very high alpha values when they are electrostatically charged. However, when the charge is removed, the alpha values of these media significantly decreases to levels that are well below the alpha values of media made using other materials.

"Accordingly, there remains a need to provide an improved filter, and more particularly to provide filter media and filter elements having improved discharged alpha value."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "In one embodiment, a filter media is provided having a fine fiber filtration layer and a coarse support layer that holds the fine fiber filtration layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the filtration layer. The layers of the filter media, as well as the various properties of each layer can vary. In one embodiment, the coarse support layer has a density that is greater at the peaks than a density in the troughs. In another embodiment, the fine fiber filtration layer can have a surface area that is at least 50%, and more preferably 100%, greater than a surface area of the fine fiber filtration layer in a planar configuration. In another embodiment, the coarse support layer can be a downstream coarse support layer, and the filter media can further include an upstream coarse support layer. The fine fiber filtration layer can be disposed between the upstream coarse support layer and the downstream coarse support layer. The filter media can also include at least one additional filtration layer disposed between the downstream coarse support layer and the upstream coarse support layer. In one exemplary embodiment, the at least one additional filtration layer can be formed from fibers having an average diameter greater than an average fiber diameter of fibers that form the fine fiber filtration layer.

"The fiber diameters of the various layers can vary. In one embodiment, the upstream coarse support layer can be formed from fibers having an average diameter greater than an average diameter of fibers forming the fine fiber filtration layer and equal to or less than an average diameter of fibers forming the downstream coarse support layer. In an exemplary embodiment, the upstream coarse support layer, the fine fiber filtration layer, and the downstream coarse support layer all have a waved configuration. In an exemplary embodiment, the filter media has about 2 to 6 waves per inch. The upstream and downstream coarse support layers can be formed from, for example, staple fiber layers, and the fine fiber filtration layer can be at least one of a meltblown layer and a glass fiber layer. The coarse support layer can also be formed from at least one binder fiber and at least one non-binder fiber.

"In another embodiment, the filter media can include at least one of a planar layer disposed upstream of the upstream coarse support layer and a planar layer disposed downstream of the downstream coarse support layer. The planar layer can be formed from fibers having an average diameter less than an average diameter of fibers forming the upstream coarse support layer and the downstream coarse support layer, and greater than an average diameter of fibers forming the fine fiber filtration layer. In another embodiment, the planar layer can be formed from fibers having an average diameter that is greater than the upstream and downstream coarse support layers and the fine fiber filtration layer. In such an embodiment, the planar layer is preferably disposed downstream of the downstream coarse support layer.

"The filter media can also have various properties. For example, the filter media can have a DOP alpha value of greater than about 9, and more preferably greater than about 11; a dust holding capacity of at least about 8 g/ft.sup.2 at 25 FPM face velocity using ASHRAE dust loading to 1.5 inch H.sub.2O pressure drop; a NaCl loading of less than about 50 mm H.sub.2O after loading approximately 60 mg/100 cm.sup.2 of 0.26.mu. particles at 25 FPM face velocity; an air permeability in the range of about 10 CFM to 300 CFM; a basis weight in the range of about 70 gsm to 1100 gsm; and/or a thickness in the range of about 1.5 mm to 25 mm.

"In yet another embodiment, a filter media is provided having a first fibrous layer with a waved configuration forming a plurality of waves, each wave having a random wave form and height, and each wave having a peak and a trough, adjacent peaks being spaced a distance apart from one another and adjacent troughs being spaced a distance apart from one another. The filter media can also include a second fibrous layer mated to the first fibrous layer and formed from fibers that are more coarse than fibers forming the first layer.

"In one embodiment, the first fibrous layer can have a surface area that is at least about 50% greater, and more preferably 100% greater, than a surface area of the first fibrous layer in a planar configuration. The first fibrous layer can be formed from, for example, fine fibers having an average diameter less than an average diameter of fibers forming the second fibrous layer. The average diameter of the fibers of the first fibrous layer can be less than about 5.mu. and the average diameter of the fibers of the second fibrous layer is greater than about 10. In another embodiment, the second fibrous layer can have a fiber density that is greater adjacent to the peaks of the first fibrous layer than the fiber density adjacent to the troughs of the first fibrous layer. The second fibrous layer can be disposed downstream of the first fibrous layer, and the filter media can also include a third fibrous layer disposed upstream of the first fibrous layer. In one exemplary embodiment, the third fibrous layer is formed from fibers having an average diameter that is equal to or less than an average diameter of fibers forming the second fibrous layer, and the diameter of the fibers forming the second fibrous layer is greater than an average diameter of fibers forming the first fibrous layer. The first, second, and third fibrous layers can have a waved configuration, and the filter media can also include at least one of a fourth layer disposed upstream of the third fibrous layer and having a planar configuration and a fifth layer disposed downstream of the second fibrous layer and having a planar configuration. In certain exemplary embodiments, the first fibrous layer is a meltblown layer or a glass fiber layer, and the second fibrous layer is formed from at least one binder fiber and at least one non-binder fiber.

"In yet another embodiment, a multi-layer filter media is provided having a curvilinear web formed from a fine fiber layer and at least one coarse support layer formed from a blend of binder fibers and non-binder fibers. The at least one coarse support layer can maintain spacing between adjacent peaks of the fine fiber layer and maintain spacing between adjacent troughs of the fine fiber layer. The filter media can also include a planar web mated to the curvilinear web.

"In one embodiment, the fine fiber layer can be a meltblown layer or a glass layer, and the at least one coarse support layer can be formed from at least one binder fiber and at least one non-binder fiber. The at least one coarse support layer can include a first coarse support layer disposed upstream of the fine fiber layer and a second coarse support layer disposed downstream of the fine fiber layer. The planar web can be disposed upstream of the first coarse support layer. In an exemplary embodiment, the second coarse support layer is formed from fibers having an average fiber diameter that is greater than an average fiber diameter of fibers forming the first coarse support layer, and the average fiber diameter of the fibers forming the second coarse support layer is greater than an average fiber diameter of the fibers forming planar web, and the average fiber diameter of the fibers forming the planar web is greater than an average fiber diameter of fibers forming the fine fiber layer. In other aspects, the fine fiber layer can have a surface area that is at least about 50% greater than a surface area of the fine fiber layer in a planar configuration.

"In other aspects, a filter element is provided having a filter media with at least two fibrous layers having a waved configuration such that the filter media includes a plurality of non-uniform waves having a height that is about 2'' or less. At least one of the fibrous layers can be a fine fiber filtration layer, such as a meltblown layer or a glass layer, and at least one of the fibrous layers can be a coarse fiber support layer. The filter element can also include a housing disposed around a perimeter of the filter media. In one embodiment, the housing can be formed by stiffening a portion of the perimeter of the filter media. In another embodiment, the housing can be a frame disposed around the perimeter of the filter media. The filter media preferably has a MERV rating of 7 to 16.

"In another embodiment, a pleated filter element is provided having a filtration layer and a support layer mated together to form a waved filter media with a plurality of peaks and troughs. The waved filter media is pleated. In an exemplary embodiment, the waved filter media includes a stiff backing sufficient to allow the waved filter media to maintain pleats. Alternatively or in addition, the waved filter media can have a stiffness that allows the waved filter media to maintain pleats. In an exemplary embodiment, the waved filter media has a thickness, before pleating, of about 0.5'' or less, and a thickness when pleated of about 12'' or less, and more preferably about 2'' or less. The pleated waved filter media can also include a housing disposed around a perimeter of the filter media. In an exemplary embodiment, the pleated filter media has MERV rating of 7 to 16.

"In other aspects, a bag filter is provided having a housing and a plurality of filters mated to the housing. Each filter can have a pocket formed therein and can be configured to receive airflow therethrough, and each filter can be formed from a filter media having a first fibrous layer, such as a meltblown or glass layer, that is held in a waved configuration by a second fibrous layer to form peaks and troughs. The housing can be, for example, a frame and an open end of each filter can be mated to the frame. The filters can be positioned parallel to one another. The filters can also optionally include at least one spacer disposed therein and adapted to maintain opposed sidewalls of the filter at a predetermined distance apart from one another. In an exemplary embodiment, the filter media has a thickness that is about 2'' or less, and more preferably about 0.5'' or less, and/or a MERV rating in the range of about 7 to 16, and more preferably about 10 to 16. The filter media can also include a third fibrous layer disposed on a side of the first fibrous layer opposite to the second fibrous layer.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1A is a side view illustration of one embodiment of a filter media;

"FIG. 1B is a side view illustration of another embodiment of a filter media;

"FIG. 1C is a side view illustration of one layer of the filter media of FIG. 1A;

"FIG. 2A is a perspective view of one embodiment of a panel filter;

"FIG. 2B is a side cross-sectional view of the panel filter of FIG. 2A taken across line 2B;

"FIG. 3 is a side view of another embodiment of a panel filter;

"FIG. 4A is a perspective view of one embodiment of a pleated filter element;

"FIG. 4B is a side cross-sectional view of another embodiment of a pleated filter element;

"FIG. 4C is a side cross-sectional view of yet another embodiment of a pleated filter element;

"FIG. 5A is a perspective view of one embodiment of a bag filter having multiple filter bags disposed therein;

"FIG. 5B is a perspective view of one of the filter bags of FIG. 5A;

"FIG. 5C is a side cross-sectional view of the filter bag of FIG. 5B;

"FIG. 6 is a chart showing discharged DOP penetration versus pressure drop for various filter media;

"FIG. 7 is a chart showing dust holding capacity for various filter media;

"FIG. 8 is a chart showing NaCl Loading for various filter media; and

"FIG. 9 is a chart showing a multi-pass liquid test for various filter media."

For additional information on this patent application, see: Healey, David T.; Gahan, Richard. Waved Filter Media and Elements. Filed September 30, 2013 and posted June 19, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=7508&p=151&f=G&l=50&d=PG01&S1=20140612.PD.&OS=PD/20140612&RS=PD/20140612

Keywords for this news article include: Hollingsworth & Vose Company.

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Source: Politics & Government Week


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