Pleated filter element comprising pleated filter media

Abstract

A filter element is presented that includes a pleated filter media including a major upstream face and a major downstream face and including a plurality of pleats with a pleat direction and with a plurality of upstream pleat tips and upstream valleys and a plurality of downstream pleat tips and downstream pleat valleys. The pleated filter media includes a single layer of a nonwoven web including melt-blown polymeric fibers, the melt-blown polymeric fibers having a fiber solidity of at least 10% and an effective fiber diameter of at least 2 μm. The pleated filter media is self-supporting.

Description

[0001] PLEATED FILTER ELEMENT COMPRISING PLEATED FILTER MEDIA

[0002] Background

[0003] Respirators are often used for cleansing air to be breathed by a user, and commonly include a mask body along with one or more filter elements that are fluidly connected to the mask body.

[0004] Summary

[0005] A filter element is presented that includes a pleated filter media including a major upstream face and a major downstream face and including a plurality of pleats with a pleat direction and with a plurality of upstream pleat tips and upstream valleys and a plurality of downstream pleat tips and downstream pleat valleys. The pleated filter media includes a single layer of a nonwoven web including melt-blown polymeric fibers, the melt-blown polymeric fibers having a fiber solidity of at least 10% and an effective fiber diameter of at least 2 pm. The pleated filter media is self-supporting.

[0006] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. It is to be understood, therefore, that the following description should not be read in a manner that would unduly limit the scope of this disclosure.

[0007] Brief Description of the Drawings

[0008] FIG. 1 illustrates an exemplary reusable respirator in which embodiments herein may be useful.

[0009] FIGS. 2A-2B illustrate fiberglass and polymeric filter media, respectively.

[0010] FIGS. 3A-4D illustrate pleated media in filter elements in accordance with embodiments herein.

[0011] FIGS. 5A-5C illustrate an example filter element and housing therefore in accordance with embodiments herein.

[0012] FIG. 6 illustrates a process of making a pleat pack in accordance with embodiments herein.

[0013] Like reference numbers in the various figures indicate like elements. Some elements may be present in identical or equivalent multiples; in such cases only one or more representative elements may be designated by a reference number but it will be understood that such reference numbers apply to all such identical elements. Unless otherwise indicated, all figures and drawings in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. In particular the dimensions of the various components are depicted in illustrative terms only, and no relationship between the dimensions of the various components should be inferred from the drawings, unless so indicated. Detailed Description

[0014] Although terms such as "top”, bottom”, 'upper", lower”, "under", “over”, “up” and “down”, and “first” and “second” may be used in this disclosure, it should be understood that those terms are used in their relative sense only unless otherwise noted. As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties). The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. The term “essentially” means to a very high degree of approximation (e.g., within plus or minus 2 % for quantifiable properties): it will be understood that the phrase “at least essentially” subsumes the specific case of an “exact” match. However, even an “exact” match, or any other characterization using terms such as e.g. same, equal, identical, uniform, constant, and the like, will be understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.

[0015] The term “upstream” is used to denote the side of an entity (e.g. a pleated air filter media) from which moving air impinges on the entity: the term "downstream" is used to denote the side of an entity through which air exits the entity7. Terms such as inward, outward, outermost, and the like, are with reference to the upstream-downstream direction of the pleated filter media. The term “lateral”, and terms such as e.g. “laterally inward” and the like, are with reference to a direction along the Pleat Direction of the pleated air filter media, as discussed in detail herein.

[0016] By “occlude”, “occlusive”, and like terms is meant to block so that at least substantially no air can flow therethrough.

[0017] FIG. 1 illustrates an exemplary reusable respirator in which embodiments herein may be useful. FIG. 1 illustrates an individual 100 wearing a half-face reusable respirator 102 which is configured to couple to one or more pleat packs 110, each pleat pack containing a pleated filter media (not shown in FIG. 1).

[0018] However, while a half-face reusable respirator (e.g. a reusable respirator that only covers half of the face of individual 100) is illustrated in FIG. 1. it is expressly contemplated that embodiments described herein may be more broadly applicable to powered air-purifying respirator (PAPR) filters as w ell as to other types of reusable respirator, such as full-face respirators, for example.

[0019] The filter element inside pleat pack 110 is important for both user comfort and safety. The filter element is designed to filter out particulates from the ambient air. From a safety7perspective, it is desired to have a filter element that has sufficient filtration and loading capacity. From a comfort perspective, it is desired to have a filter element with a low pressure drop across the filter media. Pressure drop correlates to an ability of a user to breathe through the filter element.

[0020] Pleated media, as illustrated in FIGS. 3-4, refers to a filter element that has been pleated - e.g. folded repeatedly into a zig-zag or accordion form. The pleated filter element is then placed within a housing of a respirator, and air is forced through the filter element either by a user breathing (reusable respirator) or by a motor and fan (PAPR).

[0021] The purpose of pleating a fiber element is to increase the area of filter element that is available for filtration and particulate loading. However, the pleated media must be formed such that air flows unimpeded through as much of the filter media as possible. If adjacent pleats close off air flow channels, the pressure drop increases and the available filter media surface area decreases.

[0022] Generally, pleatable filter media is designed such that, when pleated, it will (1) maintain a sharp fold line and (2) be self-supported. Fiberglass is an example material that can meet both of these requirements - it partially fractures when folded (as seen in FIG. 2A) and is a stiff material that can result in a self-supported pleated media.

[0023] However, fiberglass as a filter media has some undesirable features. Fiberglass filter media is fragile and prone to breakage. Additionally, filter media formed from fiberglass may be treated to be oil resistant, for example in compliance with any of the NIOSH R95, P95, P99 and / or P100 classification or similar standards in other jurisdictions. Oil resistant treatments ty pically include fluorinated elements, which is undesirable.

[0024] A filter media is desired that is less fragile and prone to breakage than fiberglass material and meets regulatory' requirements for oil-resistance without the use of a fluorinated material or a fluorination treatment. A filter media is also desired that has low penetration and pressure drop while meeting penetration, loading, and stiffness requirement.

[0025] A filter media is also desired that can meet these requirements with a single sheet of media, which reduces the complexity' of the manufacturing process. FIGS. 2A-2B illustrate fiberglass and polymeric filter media, respectively. FIG. 2A illustrates fiberglass material 210 which, after scoring, has fractured along a fold line 212. FIG. 2B illustrates a polymeric blown microfiber filtration media 220 which does not fracture along the fold line 222.

[0026] A filter media is also desired that can meet these requirements without requiring a coating process. Self-supporting filter media in accordance with embodiments herein is a single sheet of media free of a coating. U.S. Patent No. 12,030,006, issued on July 9, 2024, for example, describes a self- supporting filtering media that includes a binder component as part of the filtration media. Embodiments of self-supporting media described herein are free of a binder material, comprising nonwoven fibers formed into a pleated structure. Similarly, U.S. Patent No, 1 1,819,793, issued on November 21, 2023. in another example, describes a filter cartridge with a filtration layer having a cured stiffening agent to maintain the pleated form. Embodiments of self-supporting media described herein are free of a binder material, stiffening agent, or a laminate layer.

[0027] Filter media in accordance with embodiments herein is formed of a single layer of nonwoven material that is sufficiently stiff to be self-supporting once pleated into a pleat pack construction. Many previous filter media used for pleat pack constructions required a separate stiffener element. For example, filter media may have been laminated, welded or thermally bonded to a scrim or stiffening elements. Stiffening elements could be woven materials, nonwoven materials, or metal, for example. Multilayer filter media constructions may have been coupled together by lamination, by ultrasonic or other welding techniques, thermal bonding or using adhesives. The filter media, in accordance with embodiments herein, does not undergo a laminating step to another, stiffer material. The filter media herein contains a single layer of material which is not coupled to another separate layer of material using any welding, bonding or adhesive treatment.

[0028] Forming pleat packs, in accordance with embodiments herein, may include the application of adhesive to the pleated media, for example to form edge dams or to seal the filter media to an interior surface of a cartridge. However, it is expressly noted that filter media described herein is self- supporting prior to the use of adhesive to form edge dams or the sealing of the filter media to the interior of a filter cartridge housing.

[0029] Nonwoven blown microfiber polymer-based electret filter material provides some benefits over fiberglass media. Polymeric filter material can be quasi-permanently charged, for example using the process described in US Pat. No. 5,496,507 issued on March 5, 1996, which is herein incorporated by reference, or using a similar process. Filtration-grade fiberglass is generally not charged and may have limited ability to hold a charge. Non-charged filter material generally works based on mechanical filtration - e.g. the filter media fibers are woven or formed densely enough such that particulates are caught across a depth of the filter media. Charging a filter media causes the fibers of the filter media to capture particulates through the additional mechanism of electrostatic attraction. Because particulates are captured with this additional capture mechanism within the filter media, it is also possible to form a filter media that maintains the same filtration efficiency with a lower pressure drop.

[0030] However, polymeric filter media, traditionally, is soft and limp, which limits the ability to pleat it densely within a pleat pack. This can be solved by adding a stiff material to the filter media to achieve the desired stiffness. However, it is desired to densely pleat polymeric filter media without the addition of a stiff material layer.

[0031] The importance of sharp fold lines and self-supporting structure is illustrated in the comparison of FIGS. 3A and 3B. In FIG. 3A, a nonwoven polymeric electret material 300 is pleated. The polymeric material, because of its low stiffness and flexibility, forms a rounded pleat tip 310. It is desired for ambient air to flow through all available channels formed by the pleating process. However, approximately half of the channels are at least partially occluded, as illustrated by reference numeral 320. Ambient air can flow more easily through channels 314 than through channels 312.

[0032] In contrast, FIG. 3B, which illustrates a filter media in accordance with embodiments herein, exhibits sharp tips 360 when pleated, with most air channels being not-occluded, as illustrated by channels 362 and 364. As used herein, sharpness of tips 360 refers to a radius of curvature at the pleat tip. A sharp tip as defined as having a radius of curvature less than half of a pleat distance (e g. a diameter of curvature is less than a width of each pleat). When a radius of curvature is larger than half the pleat distance, occlusion of air channels is more likely to occur.

[0033] Embodiments herein include a filter element composed of a single sheet of polymeric filter media, the filter media being able to form sharp fold lines and is self-supported when pleated. The single sheet of filter media, in accordance with embodiments herein, is formed of a chargeable polymeric material.

[0034] Embodiments herein include filter element formed of a single sheet of non-laminated media that has consistent, or uniform, mechanical properties throughout the thickness of the polymeric web that is self-supported when pleated. Embodiments herein include a filter media with a lower basis weight than other polymeric filter media materials while maintaining a sufficient stiffness to be self- supporting when pleated. The lower basis weight enables a higher pleat count (e.g. folding the filter media more times) which lowers the pressure drop across the filter element.

[0035] In some embodiments herein, filter media is composed of a melt-blown polypropylene material with a suitable charging additive. Filter material herein may have a basis weight between 60-100 grams per square meter (g / m2or gsm) in some embodiments. In some embodiments, the basis weight is between 70-100 gsm.

[0036] In some embodiments herein, filter media may have a thickness between 300-500 pm, composed of fibers having an effective fiber diameter of between about 2 pm to about 8 pm. and a fiber solidity of 10-18 %.

[0037] "Solidity" is a nonwoven web property inversely related to density and characteristic of web permeability and porosity (low Solidity corresponds to high permeability and high porosity) and is defined by Equation 1 below.

[0038] 1000

[0039] Solidity (%) = -

[0040] Web Thickness (

[0041] Equation 1 Filter media in accordance with embodiments herein may have a Gurley stiffness between 100- 1000 mg in accordance with some embodiments. In some embodiments, filter media herein has a Gurley stiffness of at least about 100 mg. In some embodiments, filter media herein has a Gurley stiffness of at least about 150 mg. In some embodiments, filter media herein has a Gurley stiffness of less than 1000 mg. In some embodiments herein, filter media herein has a Gurley stiffness of less than about 550 mg. In some embodiments, the filter media has a Gurley stiffness between 150-350 mg.

[0042] Filter media in accordance with embodiments herein may have a pleat density of at least 7 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 8 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 9 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 10 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 11 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 12 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 13 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 14 pleats per inch. Filter media in accordance with embodiments herein may have a pleat density of at least 15 pleats per inch.

[0043] In some embodiments herein, a filter media has a low penetration, quantified as lower than 0.01%, or even lower than 0.001%, at a face velocity' of 13.8 cm / s, determined using the Percent Penetration test method described in the Examples below. In some embodiments herein, filter media may have a pressure drop between 3-50 mmFbO at area face velocity of 13.8 cm / s. In some embodiments herein, a filter media has a quality factor of greater than 0.3 at a face velocity of 13.8 cm / s.

[0044] The combination of stiffness and flat media filtration allows for a single sheet of filter media in accordance with embodiments herein to form a self-supported, filtering pleated structure.

[0045] FIGS. 4A-4D illustrate a pleat pack and associated filter media in accordance with embodiments herein.

[0046] FIG. 4A illustrates a perspective view' from the upstream side of an exemplary' pleated filter element 401 comprising pleated air filter media 410. Pleated air filter media 410, in accordance with embodiments is a single sheet of media having fibers with an effective diameter between about 2 and about 8 pm. In some embodiments, the single sheet of media has fibers with an effective diameter betw een about 4 and about 6 pm. The fibers of pleated air filter media 410 have a fiber solidity between about 9-18%. The pleated air filter media 410 has a basis weight between about 50 and about 120 gsm. In some embodiments, the sheet of filter media has a basis weight between about 50 gsm and about 100 gsm. The single sheet of air filter media, prior to pleating, has a thickness between about 0.3 and about 1.2 mm. In some embodiments, the single sheet of air filter media has a thickness between about 0.3 and about 0.5 mm.

[0047] When pleated, filter element 401 can be characterized as having pleats with a pleat height between about 6-23 mm or between 10-23 mm. Pleat heights may vary based on application. Filter element 401 is pleated such that a pleat density7is between about 7-15 pleats per inch.

[0048] Respirators containing filter media in accordance with embodiments herein can be characterized as having a pressure drop between about 3-50 mmFhO at 85 liters per minute. Respirators containing filter media described herein can be characterized as having a penetration of less than 0.001% (when evaluated using dioctyd phthalate, or DOP aerosol measured according to the procedures disclosed in the Working Examples) at 85 liters per minute.

[0049] Respirators containing filter media in embodiments herein may, when worn properly, filter at least 95% of airborne particles having an average diameter of 0.3 pm. In some embodiments, such respirators may, when worn properly, filter at least 99% of airborne particles having an average diameter of 0.3 pm. In some embodiments, such respirators may, when worn properly, filter at least 99.97% of airborne particles having an average diameter of 0.3 pm. In some embodiments, such respirators herein is at least partially resistant to oily aerosol particles having an average diameter of 0.3 pm.

[0050] Filter element 401 may be formed by pleating air filter media 410 using a suitable pleating process. Once pleated, the single sheet of air filter media 410 is self-supporting on its own, without an additional stiffening element. Filter element 401 does not contain a laminated element, e.g., pleats 420, 430 are formed from a single sheet of air filter media 41 alone. Filter element 401 is free of fiberglass or any fluorinated material.

[0051] A portion of an exemplary7filter element 401 is shown in a side view7in FIG. 4B. In some embodiments filter element 401 may be rectangular in shape (which specifically includes square shapes) with e.g. four comers; in such embodiments pleated filter media 410 may thus have a generally rectangular perimeter (which does not preclude irregularities, notches, chamfered or angled comers, or the like, in the perimeter of filter media 410). Pleated filter media 410 (and filter element 401) comprises major edges, e.g. four major edges as shown in FIG. 4A. Major edges (ends) 404 and 404’ (which terminate as exposed pleats) will be referred to herein as corrugated edges, and major edges (ends) 405 and 405’ will be referred to as noncormgated edges, all as shown in FIG. 4A.

[0052] Filter element 401 comprises an upstream major side 402 and a downstream major side 403; pleated filter media 410 thus includes an upstream major face 425 and a downstream major face 435. In some embodiments, filter element 401 may be upstream-downstream symmetrical (e.g., filter element 401 may be installed in a filter element housing with either major side oriented upstream); in such cases the designation of upstream and downstream sides / faces is interchangeable. In other embodiments, however, filter element 401 is not symmetrical in this manner and the designation of upstream and downstream sides and faces is not interchangeable.

[0053] Pleated filter media 410 may be made from any suitable nonwoven organic polymeric material. Any of polyethylene, polypropylene, poly(methyl pentene), cyclic olefins (COCs), polyester (PET), or poly(lactic acid) may be suitable, for example. In some embodiments, filter media may be formed from at least some partially recycled material. Any suitable method of making a nonwoven web that results in the fiber properties and properties of filter media 410 may be used. In particular embodiments, the nonwoven web may be a melt-blown nonwoven web, meaning that the fibers are meltblown and exhibit an Effective Fiber Diameter (EFD) of less than about 10 gm. In some embodiments, fibers herein exhibit an EFD of less than about 8 pm. In some embodiments, fibers herein exhibit an EFD of less than about 6 pm.

[0054] In specific embodiments, pleated filter media 410 is formed of an electret material. By an electret material is meant a material (e.g. an organic polymeric material) that, after a suitable charging processes, exhibits a quasi-permanent electric charge. The electric charge may be characterized by an X-ray Discharge Test as disclosed e.g. in U.S. Patent Publication No. 2011-0290119. Such a material may be chosen from any suitable material, e.g. split fibrillated charged fibers as described in U.S. Patent RE 30782. Such charged fibers can be formed into a nonwoven web by any suitable means such as disclosed in U.S. Patent 5,230,800. In other specific embodiments, filter media 410 can be a melt blown microfiber nonwoven web (e.g. of the general types disclosed in U.S. Patent 4,215.682 and U.S. Patent 7,989,371) that may include at least some fibers that comprise electrets. Filter media that may be particularly suitable for certain applications might include e.g. media of the general type described in U.S. Patent 8162153 to Fox; and media generally known as tribocharged media. Any such media can be charged to provide charged electret moieties if desired.

[0055] Any suitable charging method may be used, chosen from e.g. corona charging, hydrocharging, tribocharging, and so on. In some embodiments, a filter media may be formed from pre-charged electret fibers; or, a filter media may be formed (e.g. collected as a nonwoven web and consolidated if desired, or formed into a membrane) and then post-charged. If desired, the media may comprise one or more charging additives, e.g. chosen from any of the additives described in International Patent Publication W02016 / 033097, published March 3, 2016.

[0056] In various embodiments, any such filter media may exhibit a thickness of less than about 1.2 mm. In some embodiments, the filter media exhibits a thickness of less than about 1.0 mm. In some embodiments, the filter media exhibits a thickness of less than about 0.5 mm. In some embodiments, the filter media exhibits a thickness between about 0.3 mm and 0.5mm. In various embodiments, any such filter media may exhibit a basis weight of from at least about 50, 70, or 80 grams per square meter (g / m2). to at most about 120 or 100 g / m2In various embodiments, the media may exhibit a pressure drop that is greater than about 10.0 or 15.0 mm of water (measured according to the procedures disclosed in the Working Examples). In further embodiments, the media may exhibit a pressure drop that is less than about 60, 50, 40, or 30 mm of water. In various embodiments, the media may exhibit a Percent Penetration (i.e., DOP initial Percent Penetration, measured according to the procedures disclosed in the Working Examples) of less than about 1.0, 0.1, 0.05 or 0.01 or 0.001% at face velocity of 13.8 cm / s.

[0057] The stiffness of the media may be characterized by a Gurley Stiffness (measured as described in the Working Examples herein). In various embodiments, filtration media as disclosed herein may exhibit a Gurley Stiffness (measured individually) of at least about 150, or even at least about 200, or even at least about 250, or even at least about 300, or even at least about 350, or even at least about 400, or even at least about 450, or even at least about 500, or even at least about 550 mg. In some embodiments, filtration media as disclosed herein may exhibit a Gurley Stiffness of at least about 600 mg, or at least about 700 mg, or even at least about at 800 mg, or even at least about 900 mg. In some embodiments herein, filtration media exhibits a Gurley Stiffness of less than about 1000 mg. In some embodiments herein, filtration media exhibits a Gurley Stiffness of less than about 550 mg. In some embodiments herein, filtration media exhibits a Gurley Stiffness of less than about 350 mg.

[0058] Pleated Filter Media

[0059] As noted above, filter media 410 is pleated. In at least some embodiments, pleated filter media 410 does not comprise any type of planar reinforcing structure or support layer (e.g., strips of chipboard, a layer of wire mesh, anonwoven scrim, etc.) that is bonded to pleat tips of a major side of the pleated filter media to stabilize the pleat spacing. Moreover, in at least some embodiments pleated filter media 410 does not include any kind of protective layer or support layer (e.g. a wire mesh, a polymeric netting, or a non-woven scrim) that is pleated along with the pleated filter media and that does not perform a filtering function (e.g., that exhibits a Percent Penetration of greater than 99.0). Thus, in some embodiments, the filter element 401 may consist essentially of, or consist of, a pleated filter media comprising an organic polymeric nonwoven layer, free of any prefilter or stiffening layer or any other component layer being present. In some embodiments, the pleats of filter media 410 do not have any dimples of the type described e.g. in U.S. Patent 5,427,597.

[0060] As shown in FIGS. 4A and 4B, pleated filter media 410 comprises a plurality of upstream pleats 420 and downstream pleats 430. Each upstream pleat 420 includes an upstream pleat tip 421 and each adjacent pair of upstream pleats 420 defines an upstream pleat valley 422 therebetween. Downstream pleats 430 are in oppositely-facing configuration from upstream pleats 420. Each downstream pleat 430 includes a downstream pleat tip 431 and each adjacent pair of downstream pleats 430 defines a downstream pleat valley 432 therebetween. As used herein, the Pleat Direction (Dpin FIG. 4C, also referred to as the lateral direction) is a direction that is aligned with the long axis of the pleat tips (and that typically runs from one corrugated edge 404 to the other corrugated edge 404’ of the pleated filter media). The longitudinal direction (Di in FIG. 3C) is a direction that is orthogonal to the pleat direction and that typically runs from one noncorrugated edge 405 to the other noncorrugated edge 405’ of the pleated filter media. (Although the terms longitudinal and lateral are used herein for convenience of description, it is not strictly necessary that the longitudinal dimension of pleated filter media 410 must be greater than the lateral (Pleat Direction) dimension of pleated filter media 410.) The upstreamdownstream direction (Du-d in FIG. 4C) is a direction extending through the filter element from the upstream side 402 to the downstream side 403, and typically corresponds to the overall direction of air flow through the filter element.

[0061] Further details of pleat geometry are discussed with reference to the side view of FIG. 4C (in which a portion of an exemplary pleated air filter media 410 is viewed along the pleat direction DP■with the later-described adhesive dams omitted for clarity). Pleat spacing, pleat height, and pleat distance as defined herein are evaluated with the pleated air filter media 410 in a nominally planar configuration in which the pleated filter media 410 exhibits a readily recognizable overall major plane (notwithstanding the local deviations from this plane that are inherent in each pleat), as in FIG. 4C. The pleat height (pleat amplitude) is the distance (Ph in FIG. 4C) from a first-side pleat tip 421 to a second-side pleat tip 431 , along a direction that is orthogonal to the overall major plane of filter media 410 (i.e., along a direction that is aligned with the upstream-dow nstream direction Du-d of the pleated media). In various embodiments, the pleat height of media 410 may be at least about 2, 4, 6, 8, or 10, or 12 mm. In further embodiments, the pleat height may be at most about 45, 40, 35, 30, 25, 20, 15, 12, 10, 8, or 6 mm. In particular embodiments, a pleated media may exhibit a regularly varying pleat height, for example a predetermined alternating pattern of lower pleat heights interspersed with higher pleat heights.

[0062] The pleat spacing (Psin FIG. 4C) is the distance between nearest-neighbor same-side pleat tips, along a direction that is aligned with the overall major plane of the filter media (i.e., along the longitudinal direction Di of the pleated media). Pleated filter media 410 may have any suitable pleat spacing.

[0063] Embodiments herein include pleated filter media having sharp pleat tips. Sharp pleat tips are characterized by a radius of curvature, at the tip. of less than half of a distance between adjacent pleats. E.g. embodiments herein have a pleat width that is larger than the diameter of curvature at a pleat tip. In embodiments in which media 410 is tightly pleated, adjacent walls of a pleat may be at least substantially parallel to each other over at least about 70. 80 or even 90 % of the pleat height, on average. Such a tightly pleated media is shown in idealized representation in FIG. 4D.

[0064] Filter media 410 can be pleated by any suitable method that can provide a tight pleat spacing. In some embodiments the media may be scored to provide score lines, along which the media can be folded to form very sharp pleat tips with a small radius of curvature, if desired. Such a pleating operation, which may be conveniently done e.g. by rotary-score pleating, may often result in score lines being readily apparent on at least one major of filter media 410 of filter element 401. In some embodiments, both surfaces (upstream and downstream) of filter media 410 are rotary scored to exhibit score lines (noting that any such score lines may or may not be visible on casual inspection of the pleated media and that it may be necessary to physically manipulate (e.g.. partially unfold) the pleated media in order to see the score lines). In some embodiments, pleating is done using an ultrasonic pleating method, for example as described U.S. Provisional Patent Application No. 63 / 779,099, filed March 27, 2025. Ultrasonically pleated filter media of embodiments herein may exhibit the same, or characteristics similar to those described in said US Provisional Patent Application.

[0065] U.S. Provisional Patent 63 / 779,009 describes a filter element that includes pleated filter media including a nonwoven w eb having polymeric fibers and a plurality of pleat tips. The nonwoven web has a debossed portion on at least some of the pleat tips, and at least one of the following three conditions is met. 1) The debossed portion exhibits birefringence while the non wo ven web does not exhibit birefringence at a non-debossed portion. 2) The debossed portion has a retardance profile in which there is an average retardance, and the average retardance is at least three times an average retardance at the non-debossed portion. 3) The debossed portion has a total percent porosity' as determined by x-ray microtomography that is less than 80 percent of a total percent porosity of the nonwoven web at the non-debossed portion.FIGS. 5A-5C illustrate an example filter element and housing therefore in accordance with embodiments herein.

[0066] The discussions above have focused on a pleated filter media 410 and pleated filter element 401 that are essentially flat (planar) in their overall shape (disregarding local deviations due to the pleating). However, in some embodiments the pleated filter media and pleated filter element may be arcuate (as shown in exemplary embodiment in the side view of FIG. 5 A). In specific embodiments, filter element 401 is planar as made, and is conformed into an arcuate shape in order to be installed into an arcuate receptacle of a filter element housing.

[0067] Although an arcuate filter element may not be upstream-downstream reversible, it may have other advantages in e.g. allowing a filter element housing into which the filter element is installed to be curved so as to follow the contours of a user’s cheek or of a user’s hip, and so on. In some embodiments, a convex side of arcuate fdter element 401 is an upstream side 402, and a concave side of arcuate filter element 401 is a downstream side, as in the exemplary design of FIG. 5 A.

[0068] In at least some embodiments an arcuate pleated filter media 10 will exhibit a shape with single curvature, with the curvature being along a conforming axis Aothat is orthogonal to the pleat direction and is parallel to the longitudinal direction, as shown in FIG. 5A. Such a configuration will be contrasted with a shape that exhibits compound curvature (such as e.g. a section of a sphere, paraboloid or hyperboloid). This can minimize the chance of any wrinkling or crumpling of the pleated media when it is curved into an arcuate configuration. It will be appreciated that such single-cun- ature embodiments will be distinguished from filters (e.g. in respirator mask bodies) that are formed into complex, compound-curvature shapes so as to conform to e.g. a human face.

[0069] In some embodiments filter element 401 may comprise a casing that is a separately made component that is disposed on (e.g. fitted onto, wrapped around, etc.) at least portions of filter element 401. If such a casing is present, it will be provided as part of filter element 401, and will not be removable therefrom in ordinary' use of filter element 401. Such a casing is thus not a part of e.g. a filter element housing of a respirator. Such a casing may be made of any suitable material, e.g. molded plastic, paperboard, or the like. Such casings are described in detail in U.S. Pat. No. 10,751.660, issued August 25, 2020, entitled In other embodiments, filter element 401 does not include any such casing.

[0070] Filter Element Use

[0071] Filter element 401 may be used in any application in which it is desired to filter air (which term generally encompasses any breathable gaseous mixture).

[0072] In particular embodiments, filter element 401 may be used in any suitable respirator that is configured to filter breathing air. In order to include filter element 401 in a respirator, it may be convenient to install filter element 401 into the interior of a filter element housing 460 as shown in exemplary embodiment in FIGS. 5B-5C. Filter element 401 and filter element housing 460 may be used with any type of respirator, e.g. powered or unpowered, full-mask or half-mask, and so on. In various embodiments, such a respirator may comprise at least a mask body that comprises a portion that covers at least the nose and mouth of a user (and may take the form of e.g. a helmet) to define an interior air space. An exhalation valve may be provided to allow exhaled air to be discharged from the interior air space. Such a respirator may also include a harness assembly that is able to support the mask body on a user’s head. In some embodiments, filter element housing 460 may be mounted in close proximity' to the mask body. For example, a single filter element housing may be fl radically connected to the mask body, e.g. at a location in front of the mouth and / or nose of the user. Or dual filter element housings may be mounted e.g. at locations adjacent the right and left cheek of the user. In other embodiments, one or more filter element housings may be located in a unit that is remote from the mask body, e.g. a powered unit that is located e.g. on a hip belt and that comprises a fan that motivates the filtered air through a supply tube to the mask body. Filter element housing 460 as depicted in FIGS. 5B-5C may be particularly suitable e.g. for mounting on a hip belt as part of a so- called powered-air-purifying-respirator (e.g., such as the product available from 3M Company under the trade designation VERSAFLO™ TR-600) that e.g. delivers filtered air by way of a hose that fluidically connects filter element housing 460 wi th a mask body or helmet that resides on a user's face or head. However, it is emphasized that filter element 401 may be installed in a filter element housing of any suitable type.

[0073] Filter element housing 460 comprises at least one major housing portion that is configured to receive at least one filter element 401 and to fluidically connect the filter element to other components of a respirator (e.g. to a mask body). Housing 460 (e.g., major housing portion thereof) may comprise an upstream major face 61 that comprises an air-permeable area 462 (which may conveniently be achieved by providing numerous through-perforations in area 462 of upstream face 461 of filter element housing 460, as shown in FIG. 5B). In some embodiments, housing 460 (e.g. at least a major housing portion thereof) may be made of an organic polymeric resin that is molded (e.g. injection molded, vacuum-formed, thermoformed, etc.) into a desired shape. (Other ancillary parts, e.g. latches, fittings, and so on, may be attached to housing 460 as desired.)

[0074] In some embodiments, filter element 401 may be disposable with filter element housing 460 such that, when filter element 401 needs to be rechanged, the housing 460 is reusable. In such embodiments, filter element housing 460 is not a part of filter element 401 itself and in particular is removably attached to filter element 401. In such cases, housing 460 may comprise a closing portion (not shown in FIGS. 5B-5C) that is e.g. air-impermeable and that may, when closed, serve to securely hold filter element 401 in place within the interior 463 of filter element housing 460. Such a closing portion may be e.g. hingedly connected or snap-fittable to housing 460, so that the closing portion can be opened or temporarily removed so that a filter element 401 can be removed and a replacement filter element 401 installed.

[0075] In other embodiments, filter element 401 and a filter element housing 460 may be provided to a user as a unit. e.g. with filter element 401 non-removably attached to housing 460. Housing 460 containing filter element 401 will be removably attachable to other components of a respirator so as to establish a fluidic connection between housing 460 and a mask body of the respirator, so that filtered air can be delivered to the mask body. In such embodiments, housing 460 containing filter element 401 therein may be removed and discarded or recycled, and a new housing and filter element installed in the respirator, at a desired time. In the illustrative embodiment of FIG. 5C, interior 463 of housing 460 includes a receptacle 464 that is configured to receive filter element 401. (In the illustrated embodiment of FIG. 5C, receptacle 464 is arcuately shaped to receive an arcuate filter element.) However, it is expressly contemplated that both filter element 401 and housing 460 may have different shapes, e.g. housing 460 can be shaped to receive a flat filter, such as that shown in FIG. 4A. Flat or arcuate shaped filters may also have other shaped, such as ovular, circular, polygonal or non-polygonal shaped, having, for example, perimeter portions that are straight and / or curved.

[0076] Receptacle 464 may comprise sidewalls 465 that abut noncorrugated edges 405 and 405’, and sidewalls 467 that abut corrugated edges 404 and 404’, of pleated filter element 401 when installed within receptacle 464. In some embodiments the longitudinal distance between sidewalls 465 may be set so that filter element 401 is slightly longitudinally compressed (accordionized) in order to fit within the space between longitudinal sidewalls 465. Such an arrangement may help hold filter element 401 securely in place, while not compressing the pleats of filter element 401 together to such an extent as to disadvantageous^' affect the filtration performance. In various embodiments, a longitudinal distance between longitudinal sidewalls 465 may be at most about 100, 98, 96, or 94 % of the longitudinal length (before being compressed for installation into receptacle 464) of filter element 401.

[0077] If desired, a sealant or potting material (e.g. a hardenable material such as an RTV silicone or the like) may be disposed as a bead along corrugated edges 404 and 404’, and / or along noncorrugated edges 405 and 405’, e.g. at locations at which these edges are abutted against surfaces 466 of sidewalls 467 and / or 465 of housing 460, as seen in FIG. 5C. Such a material, after hardening, may minimize any air leaks around the edges of filter element 401. It will be appreciated that the presence of edge dams, in particular edge seals, within filter element 401 as discussed herein, may reduce or even eliminate the need for such a material to be used along sidewalls 467 for purposes of minimizing air leakage around corrugated edges 404 and 404’ of filter element 401. Such a material may of course be used to seal the noncorrugated edges 405 and 405’ of the pleated filter element, against sidewalls 465 of the housing, if desired. Moreover, even if no such material is needed for sealing, such a material may be applied to bond at least some portions of the edges of filter element 401 to surfaces of receptacle 464 if desired e.g. in order to more securely hold filter element 401 in place within housing 460.

[0078] In some embodiments, one or more gaskets (not shown in any Figure) may be provided within interior 464 of filter element housing 460 to assist in securely installing filter element 401 therein. Such a gasket may be permanently attached to housing 460; or it may be removable and replaceable if desired. Such a gasket may be made of a resilient polymeric material such as rubber, silicone, or the like. The polymeric material may be solid or a foam. If a foam, it may be an open-cell foam, or a closed cell foam. In some embodiments, no such gasket is present. In some embodiments, filter element 401 may be the only filtering component that resides wi thin filter element housing 460. However, in other embodiments, one or more layers of material may reside within housing 460 (e.g., in overlapping relation to, e.g. butted up against a major surface of, filter element 401) for some additional purpose. Such a layer or layers may contain one or more materials that interact with an airstream to at least partially remove one or more components (e.g., gases, vapors, solid particles, aerosols, and so on) therefrom. The components in the fluid may be e.g. sorbed onto or into an active sorbent, may be reacted with a reactive ingredient, may be exposed to a catalyst, and so on. Potentially suitable materials for such uses include e.g., activated carbon; alumina and other metal oxides; sodium bicarbonate; metal particles (e.g., silver particles) that can remove a component from a fluid by adsorption, chemical reaction, or amalgamation; catalytic agents such as hopcalite and / or gold (which can catalyze the oxidation of carbon monoxide); clay and other minerals treated with acidic solutions such as acetic acid or alkaline solutions such as aqueous sodium hydroxide; ion exchange resins; molecular sieves and other zeolites; silica; biocides; fungicides and virucides. Mixtures of any such materials can be employed. In other embodiments, such materials may be provided as particles in a parti cl e-loaded web layer. Combinations of any of these approaches may be used. If desired, such materials may be treated e.g. with one or more impregnants to enhance gas removal capability. Examples of treated materials include chemically surface-treated activated carbon.

[0079] In many embodiments, flowing air will locally approach filter element 401, and will locally leave filter element 401, along a direction that is at least generally aligned with the upstreamdownstream direction Du-d of the filter element. Such a direction will often be at least generally orthogonal to the pleat direction DPof the pleated filter media 410. That is, in ordinary use of a pleated filter element 401, there may often be little or no airflow along the long axis of the valleys of the pleated media. In particular, pleated filter element 401 is distinguished from arrangements in which a fluid flows along the valleys in between multiple layers (e.g., stacks or wraps) of pleated media. Pleated filter element 401 is thus distinguished from e.g. so-called spiral -wound filters and the like that, as supplied, comprise multiple layers of filter media and in which substantial fluid flow may occur along the long axis of the valleys in between layers of the pleated media.

[0080] FIG. 6 illustrates a process of making a pleat pack in accordance with embodiments herein. Method 600 illustrates one example process for making and using filter material as described herein. However, it is expressly contemplated that other suitable processes may also be applicable.

[0081] At block 610, filter material is obtained. The filter material may be similar to filter media 420 in embodiments herein. The filter media may have an effective diameter of about 2-6 pm, in some embodiments. In some embodiments, the filter media has an effective diameter of less than 5 pm, or less than 4 pm, or less than 3 pm. In some embodiments, the filter media has an effective diameter greater than 2 gm. The filter material may have a fiber solidity of at least about 10%, and less than about 18%. The filter media may have a basis weight of at least 50 gsm and less than about 100 gsm. The filter media may have a Gurley stiffness greater than about 150 milligrams, or even greater than about 200 milligrams, or even greater than about 250 milligrams, or even greater than about 300 milligrams, or even greater than about 350 milligrams, or even greater than about 400 milligrams, or even greater than about 450 milligrams, or even greater than about 500 milligrams or even greater than about 550 milligrams. The filter media may have a Gurley stiffness of less than about 1000 mg, or less than about 550 mg, or even less than about 350 mg.

[0082] The filter material, in accordance with embodiments herein, is a melt-blown nonwoven material. Melt-blown nonwoven materials may exhibit better filtering properties and may better facilitate a charging process.

[0083] At block 620, the filter media is charged. Any suitable charging method may be used, chosen from e.g. corona charging, hydrocharging, tribocharging, and so on. In some embodiments, a filter media may be formed from pre-charged electret fibers; or a filter media may be formed (e.g. collected as a nonwoven web and consolidated if desired or formed into a membrane) and then post-charged. If desired, the media may comprise one or more charging additives, e.g. chosen from any of the additives described in International Patent Publication WO 2016 / 033097, published March 3rd, 2016, which is hereby incorporated by reference. Other suitable charging mechanisms are envisioned. However, it is expressly contemplated that embodiments herein are formed such that the final pleated filter element is free of fluorinated compounds.

[0084] The sheet of media, in some embodiments experiences a pressure drop, when using the test methods described in the Examples, of less than about 50 mmH20 at a face velocity' of 13.8 cm / s, or even less than about 40 mmH20 at a face velocity of 13.8 cm / s. or even less than about 30 mmH20 at a face velocity of 13.8 cm / s, or even less than about 25 mmH20 at a face velocity of 13.8 cm / s, or even less than about 20 mrrd-fiO at a face velocity of 13.8 cm / s, or even less than about 15 mmH20 at a face velocity of 13.8 cm / s, or even less than about 10 mmlW at a face velocity of 13.8 cm / s. In some embodiments, the pleated media experiences a pressure drop of less than about 9 mmH20 at a face velocity of 13.8 cm / s, or even less than about 8 mmH20 at a face velocity of 13.8 cm / s, or even less than about 7 mmfhO at a face velocity of 13.8 cm / s. or even less than about 6 mmH20 at a face velocity of 13.8 cm / s, or even less than about 5 nimlbO at a face velocity of 13.8 cm / s, or even less than about 4 mmH20 at a face velocity of 13.8 cm / s, or even less than about 3 mmH20 at a face velocity of 13.8 cm / s.

[0085] At block 630, a single sheet of filter media is pleated to form a self-supporting pleated filter material. The pleated filter media is self-supporting, but free of an added stiffening element, or stiffening additive such as adhesive. The pleats in the pleated filter media are sharp pleats that exhibit a “zig-zag” shape, as opposed to softer rounded pleats in an “S” shape. The sharp pleats, as described above with respect to FIG. 3A-3B, reduces occlusion in the air channels formed by pleating.

[0086] The pleated filter media may exhibit a Percent Penetration (i.e., DOP initial Percent Penetration, measured according to the procedures disclosed in the Working Examples) of less than about 1.0, 0. 1, 0.05 or even less than about 0.01 at a face velocity of 13.8 cm / s. In some embodiments, the pleated filter media exhibits a percent penetration of even less than about 0.001% when measured according to the procedures disclosed in the Working Examples.

[0087] The pleats in the pleated filter media made in accordance with embodiments herein may have a pleat height of at least about 0.25 inches, or at least about 0.5 inches, or of at least about 1.0 inches, or of least about 1.5 inches. The pleat density’ of the pleated filter media is at least about 7 pleats per inch, at least about 8 pleats per inch, at least about 9 pleats per inch, at least about 10 pleats per inch, at least about 11 pleats per inch, or even at least about 12 pleats per inch, or even at least about 13 pleats per inch, or even at least 14 pleats per inch, or even at least 15 pleats per inch.

[0088] Pleating may be accomplished using a suitable pleating process, using various fold-line formation processes.

[0089] At block 640, a pleat pack is assembled. The pleat pack may include a housing that is configured to be received by a reusable respirator (RR) or a PAPR unit. For example, the reusable housing may include a suitable coupling feature to couple to the RR or PAPR unit. The coupling feature should be designed to significantly prevent ambient air from entering the RR or PAPR unit without passing through the pleated element. For example, the coupling feature may include a gasket or compliant material. In embodiments herein, the coupling feature is removeable, such that, when a service life of the pleat pack is reached, it can be removed from the RR or PAPR, and a new pleat pack can be coupled in place. In some embodiments, the housing of a pleat pack may be at least partially recyclable.

[0090] The pleat pack is assembled by placing the pleated material within the housing. In some embodiments herein, the pleated material is adhered to a surface of the housing with an adhesive. However, it is expressly contemplated that the adhesive used to adhere the pleated material within the housing does not meaningfully’ contribute to the pleated material being self-supporting.

[0091] Pleat packs formed in accordance with embodiments herein are configured to, when properly used with a RR or PAPR fitted for a wearer, to meet a variety’ of regulatory standards, including, for example, NIOSH standards of N95, N99, N100, High Efficiency (HE), R95, P95, P99 and / or P100. Embodiments herein may meet oily aerosol-resistant standards while being free of fluorinated compounds or fluorination treatment. Edge Dams

[0092] In some embodiments, filter element 401 has one or more adhesive edge dams (illustrated in FIGS. 4A-4D as edge dams 440). An adhesive edge dam may be located proximate a corrugated edge (404 or40 4’) of the pleated filter media. Each dam may be formed of hardened adhesive. In many embodiments, the adhesive may be provided as a liquid that is applied as an elongate bead extending along the longitudinal direction of the media, proximate an edge of the filter media. Adhesive beads may be applied simultaneously to the upstream and downstream major surfaces of the media; or, adhesive beads may be applied to one major surface and then to the other major surface. After the adhesive beads are applied to both major surfaces, the media may then be compressed (with the adhesive still in an at least semi-liquid state) along the longitudinal direction of the media to a final pleated configuration (that exhibits the pleat spacing, pleat height, and so on, that is desired to be present when filter element 401 is used). This will cause the adhesive to at least generally fill each pleat valley at a location proximate a corrugated edge of the pleated filter media. The adhesive may then be hardened while the filter media is held in this pleated configuration.

[0093] The hardened adhesive thus forms a dam 440. In at least some embodiments, pleated filter media 410 comprises a first edge dam 440 at one corrugated edge 404 of the pleated filter media, and a second edge dam 440’ at the other corrugated edge 404’, as shown in FIGS. 4A-4D (only a single edge dam 440 is visible in the side view of FIG. 4B). It will be appreciated that the hardened adhesive portions in upstream pleat valleys 422, and the hardened adhesive portions in downstream pleat valleys 432, act in concert to provide dam 440, even though the adhesive portions in the upstream pleat valleys and those in the dow nstream pleat valleys are separated from each other by the thickness of the filter media and thus may never physically contact each other. That is, the hardened upstream and downstream adhesive portions collectively form dam 440.

[0094] Dams 440 and 440’ (and optional interior dams) can provide structural rigidity- to the pleated air filter media, which can make the resulting filter element more mechanically robust, without e.g. having to use a casing material that might add undesirable weight and / or complexity. It is further noted that the presence of such adhesive dams can allow' the achievement of a tight pleating pattern. That is, if a very tight pleating pattern is used, the adhesive dams can act as spacers to provide that adjacent walls of pleats are not pushed completely against each other so that they are so closely spaced (e.g. touching each other) so as to disadvantageously block air flow through the pleat valleys.

[0095] In various embodiments, each adhesive edge dam may be located at a position from about even with the terminal ends of a corrugated edge, to a position that is recessed laterally inw ard (measured from the centerline of the dam) from the terminal ends of the corrugated edges, no more than about 0.1 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 2.0 mm, 3.0 mm, or 4.0 mm. By way of specific example, exemplary adhesive edge dams 40 and 40' as shown in FIG. 4A may be located e.g. 1-2 mm laterally inward from the terminal ends of corrugated edges 404 and 404’. and no portion of each adhesive edge dam extends outward beyond the terminal end of the corrugated edge to which it is proximate.

[0096] In some embodiments an edge dam of hardened adhesive may at least substantially or essentially fill the upstream and downstream pleat valleys so that it at least substantially occludes the pleat valleys so as to prevent airflow therethrough. In such a case an edge dam may serve as an edge seal that at least substantially or essentially prevents air (or any other flowing gas or gas mixture) from flowing laterally outward beyond a corrugated edge of the pleated filter media and thus at least partially bypassing the filter media. (The special case in which edge dams function as edge seals may be verified e.g. by mounting the filter element in a filter element housing as described later herein; if the performance of the filter element is substantially unaffected by any external sealing or gasketing that is applied to the filter element, this will indicate that the edge dams are performing as edge seals in the manner described herein.) It will be appreciated that the use of hardened adhesive edge dams 440 that serve as edge seals in this manner may e g. eliminate the need to cover the corrugated edges of the pleated filter element with casing portions or gaskets, or to seal the corrugated edges of the pleated filter element by dipping the edges in a sealing material. Or, at the very least, the extent to which such measures may be needed, and may thus allow the complexity and cost of filter element 401 to be reduced.

[0097] If desired, one or more additional interior dams 442 can be provided laterally in between the first and second adhesive edge dams 440 and 440’ as shown in exemplary embodiment in FIG. 4A. Although not necessarily needed for any occluding function, such additional, interior adhesive dams may provide mechanical rigidity' to the pleated filter element, and may also assist in maintaining the pleats of the filter media in e.g. a tightly pleated configuration (e.g. a configuration of the type shown in exemplary representation in Fig. 4D). The adhesive dams may be spaced at least generally uniformly across the lateral extent of the pleated filter media (as in the exemplary embodiment of FIG. 4A), if desired. Or, such spacing may vary as desired. Any number of interior dams (e.g. one, two, three, four, or more) may be present (two such interior dams are depicted in FIG. 4A).

[0098] Edge dams are discussed in greater detail in U.S. Patent 11.452,891 to Sebastian et al., issued on September 27, 2022, the text of which is hereby incorporated by reference.

[0099] A filter element is presented that includes a pleated filter media including a major upstream face and a major downstream face and including a plurality of pleats with a pleat direction and with a plurality of upstream pleat tips and upstream valleys and a plurality of downstream pleat tips and downstream pleat valleys. The pleated filter media includes a single layer of a nonwoven web including melt-blown polymeric fibers, the melt-blown polymeric fibers having a fiber solidity of at least 10% and an effective fiber diameter of at least 2 pm. The pleated filter media is self-supporting.

[0100] The filter element may be implemented such that the single sheet of nonwoven web has a basis weight of at least about 50 grams per square meter. The filter element may be implemented such that the single sheet of nonwoven web has a basis weight of at least about 70 grams per square meter. The filter element may be implemented such that the single sheet of nonwoven web has a basis weight of less than about 120 grams per square meter. The filter element may be implemented such that the single sheet of nonwoven web has a basis weight of less than about 100 grams per square meter.

[0101] The filter element may be implemented such that the single sheet of nonwoven web has a thickness of at least about 0.3 mm. The filter element may be implemented such that the single sheet of nonwoven web has a thickness of less than about 2 mm. The filter element may be implemented such that the single sheet of nonwoven web has a thickness of less than about 1.7 mm. The filter element may be implemented such that the single sheet of nonwoven web has a thickness of less than about 1.5 mm. The filter element may be implemented such that the single sheet of nonwoven web has a thickness of less than about 0.5 mm.

[0102] The filter element may be implemented such that the effective fiber diameter is at least 2.5 pm.

[0103] The filter element may be implemented such that the effective fiber diameter is at least 3 pm.

[0104] The filter element may be implemented such that the pleats are ultrasonically scored-pleats.

[0105] The filter element may be implemented such that the pleats are rotary-scored pleats or heat- scored pleats.

[0106] The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of at least about 150 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of at least about 200 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of at least about 300 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of at least about 400 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of less than about 1000 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of less than about 550 milligrams. The filter element may be implemented such that the single sheet of nonwoven web has a Gurley stiffness of less than about 350 milligrams.

[0107] The filter element may be implemented such that the pleated filter media has a pleat density of at least about 7 pleats per inch. The filter element may be implemented such that the pleated filter media has a pleat density of at least about 10 pleats per inch. The filter element may be implemented such that the pleated filter media has a pleat density of at least about 15 pleats per inch. The filter element may be implemented such that the pleated filter media has a pleat density of less than about 15 pleats per inch.

[0108] The filter element may be implemented such that the pleated filter media has a pleat height of less than 1.5 inches. The filter element may be implemented such that the pleated filter media has a pleat height of less than 1.0 inches. The filter element may be implemented such that the pleated filter media has a pleat height of less than 0.5 inches. The filter element may be implemented such that the pleated filter media has a pleat height of at least 0.25 inches.

[0109] The filter element may be implemented such that the single sheet of nonwoven web exhibits a quasi-permanent electric charge.

[0110] The filter element may be implemented such that the single sheet of nonwoven web includes electret fibers.

[0111] The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than about 50 mmfbO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than about 40 mmFLO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than about 30 mmfLO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than about 20 mmFLO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 15 mmPLO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 12 mmPhO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 10 mrnfhO The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 8 mmfhO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 5 mmPLO. The filter element may be implemented such that the pressure drop across the pleated filter media at 85 LPM air flow rate is less than or equal to about 3 mmPLO.

[0112] The filter element may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 1%. The filter element may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.5%. The filter element may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.1%. The filter element may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.01%. The filter element may be implemented such that percent penetration (DOP) of the pleated fdter media at 85 LPM air flow rate is less than 0.001%.

[0113] The filter element may be implemented such that the single sheet of nonwoven web is free of fluorinated compounds.

[0114] The filter element may be implemented such that the pleated filter media is free of laminating adhesive.

[0115] The filter element may be implemented such that the pleated filter media is free of fiberglass.

[0116] The filter element may be implemented such that the pleated filter media exhibits unitary mechanical properties across the major upstream face.

[0117] The filter element may be implemented such that the pleat tips are sharp tips.

[0118] The filter element may be implemented such that a pleat width is greater than twice a radius of curvature of the pleat tip.

[0119] The filter element may be implemented such that the pleat tips form a zig-zag pattern.

[0120] The filter element may be implemented such that the melt-blown polymeric fibers include polypropylene.

[0121] The filter element may be implemented such that a majority of upstream and downstream pleat valleys are at least partially nonoccluded.

[0122] A filter cartridge for a reusable respiratory device is presented that includes a housing and a single sheet of self-supporting pleated media and adhesive coupling the pleated media to an interior surface of the housing. The housing includes a coupling element configured to removably couple to the reusable respiratory device. At least one major surface with an air-permeable area. The housing is configured such that substantially all of an ambient air flow is forced through the air-permeable area. The single sheet of self-supporting pleated media exhibits a quasi-permanent electric charge and includes a web of melt-blown polymeric fibers having a fiber solidity of at least 9% and an effective fiber diameter between 2 and 8 pm. The single sheet of self-supporting pleated media is an unlaminated sheet free of a stiffening layer. The adhesive coupling provides no significant stiffening effect to the sheet of pleated media.

[0123] The pleat pack may be implemented such that the reusable respirator device is a half-facepiece respirator, and wherein the coupling element is configured to removably couple to the half-facepiece respirator.

[0124] The pleat pack may be implemented such that the reusable respirator device is a full-facepiece respirator, and wherein the coupling element is configured to removably couple to the full-facepiece respirator. The pleat pack may be implemented such that the reusable respirator device is a powered airpurifying respirator, and wherein the coupling element is configured to removably couple to the powered air-purifying respirator.

[0125] The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a basis weight of at least about 50 grams per square meter. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a basis weight of at least about 70 grams per square meter. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a basis weight of less than about 120 grams per square meter.

[0126] The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a thickness of at least about 0.3 mm. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a thickness of less than about 1.2 mm.

[0127] The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of at least 150 milligrams. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of at least 200 milligrams. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of at least 300 milligrams. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of at least 550 milligrams. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of less than about 1000 milligrams. The pleat pack may be implemented such that the single sheet of self- supporting pleated media has a Gurley stiffness of less than about 550 milligrams. The pleat pack may be implemented such that the single sheet of self-supporting pleated media has a Gurley stiffness of less than about 350 milligrams.

[0128] The pleat pack may be implemented such that the self-supporting pleated media has a pleat density of at least about 7 pleats per inch. The pleat pack may be implemented such that the self- supporting pleated media has a pleat density of at least about 10 pleats per inch. The pleat pack may be implemented such that the self-supporting pleated media has a pleat density of less than or equal to about 15 pleats per inch.

[0129] The pleat pack may be implemented such that the self-supporting pleated media has a pleat height of less than 1.5 inches. The pleat pack may be implemented such that the self-supporting pleated media has a pleat height of less than 1.0 inches. The pleat pack may be implemented such that the self- supporting pleated media has a pleat height of less than 0.5 inches. The pleat pack may be implemented such that the self-supporting pleated media has a pleat height of at least 0.25 inches. The pleat pack may be implemented such that the melt blown polymeric fibers include electret fibers. The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 50 mml bO The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 40 mmH20. The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 30 rnmfhO The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 20 mmLhO. The pleat pack may be implemented such that the pressure drop across the self- supporting pleated media at 85 LPM air flow rate is less than about 15 mmfhO. The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 12 mmfbO The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 10 inmFLO. The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 8 mmfbO. The pleat pack may be implemented such that the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 5 mmfbO.

[0130] The pleat pack may be implemented such that percent penetration (DOP) of the self-supporting pleated media at 85 LPM air flow rate is less than 1%. The pleat pack may be implemented such that percent penetration (DOP) of the self-supporting pleated media at 85 LPM air flow rate is less than 0.5%.

[0131] The pleat pack may be implemented such that percent penetration (DOP) of the self-supporting pleated media at 85 LPM air flow rate is less than 0.1%. The pleat pack may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.01 %. The pleat pack may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.001%.

[0132] The pleat pack may be implemented such that the self-supporting pleated media is free of fluorinated compounds.

[0133] The pleat pack may be implemented such that the self-supporting pleated media is free of fiberglass.

[0134] The pleat pack may be implemented such that the self-supporting pleated media exhibits uniform mechanical properties across the major upstream face.

[0135] The pleat pack may be implemented such that the pleat tips are sharp tips.

[0136] The pleat pack may be implemented such that the pleat tips form a zig-zag pattern.

[0137] The pleat pack may be implemented such that the melt-blown polymeric fibers include polypropylene. The pleat pack may be implemented such that a majority of upstream and downstream pleat valleys are at least partially nonoccluded.

[0138] A respirator is presented that includes a mask body and a filter element housing fluidly connected to the mask body. The filter element housing includes: a coupling element configured to mechanically couple to the mask body, a single sheet of a pleated filter media having a basis weight of at least 60 grams per square meter, the pleated filter media including melt-blown polymeric fiber. The filter element housing houses the single sheet of pleated filter media. The pleated filter media is self-supporting such that the single sheet of pleated media is free of a stiffening layer, and wherein the single sheet of pleated filter media exhibits a quasi-permanent electric charge.

[0139] The respirator may be implemented such that the mask body is a full-facepiece.

[0140] The respirator may be implemented such that the mask body is a half-facepiece.

[0141] The respirator may further include a remote unit that includes the filter element housing, the remote unit being a powered unit that includes a fan and including a supply tube that fluidically connects the remote unit to the mask body, whereby filtered air can be delivered from the remote unit to the mask body.

[0142] The respirator may be implemented such that the single sheet of the pleated filter media is adhered to an interior surface of the filter element housing.

[0143] The respirator may be implemented such that the pleated filter media has a basis w eight of at least 50 grams per square meter. The respirator may be implemented such that the pleated media has a basis weight of at least about 70 grams per square meter. The respirator may be implemented such that the pleated media has a basis weight of less than about 120 grams per square meter.

[0144] The respirator may be implemented such that the pleated media has a thickness of at least about 0.3 mm. The respirator may be implemented such that the pleated media has a thickness of at least about 0.5 mm. The respirator may be implemented such that the melt-blown polymeric fiber has an effective fiber diameter of at least about 2 pm. The respirator may be implemented such that the melt- blown polymeric fiber has an effective diameter of less than about 12 pm.

[0145] The respirator may be implemented such that the melt-blown polymeric fiber has a fiber solidity of at least about 9%. The respirator may be implemented such that the melt-blown polymeric fiber has a fiber solidity of at least about 12%. The respirator may be implemented such that the melt- blown polymeric fiber has a fiber solidity of at least about 14%. The respirator may be implemented such that the melt-blow n polymeric fiber has a fiber solidity7of at least about 16%. The respirator may be implemented such that the melt-blown polymeric fiber has a fiber solidity of less than or equal to about 18%. The respirator may be implemented such that the pleated media has a Gurley stiffness of at least 150 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of at least 200 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of at least 300 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of at least 550 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of less than about 550 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of less than about 1000 milligrams. The respirator may be implemented such that the pleated media has a Gurley stiffness of less than about 350 milligrams.

[0146] The respirator may be implemented such that the pleated filter media has a pleat height of less than 1.5 inches. The respirator may be implemented such that the pleated filter media has a pleat height of less than 0.5 inches. The respirator may be implemented such that the pleated filter media has a pleat height of less than 1.0 inches. The respirator may be implemented such that the pleated filter media has a pleat height of less than 0.5 inches.

[0147] The respirator may be implemented such that the pleated filter media has a pleat density of at least about 7 pleats per inch. The respirator may be implemented such that the pleated filter media has a pleat density of at least about 10 pleats per inch. The respirator may be implemented such that the pleated filter media has a pleat density' of less than or equal to about 15 pleats per inch.

[0148] The respirator may be implemented such that the melt blown polymeric fibers include electret fibers.

[0149] The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 50 mmlfO The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 40 mmbhO.

[0150] The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 30 mmH20. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 20 mmHiO. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 15 mmFLO. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 12 mmH20. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 10 mmFLO. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 8 mmFLO The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is less than about 5 mmfhO. The respirator may be implemented such that the pressure drop across the pleated media at 85 LPM air flow rate is greater than about 3 mmLhO.

[0151] The respirator may be implemented such that percent penetration (DOP) of the pleated media at 85 LPM air flow rate is less than 1%. The respirator may be implemented such that percent penetration (DOP) of the pleated media at 85 LPM air flow rate is less than 0.5%. The respirator may be implemented such that percent penetration (DOP) of the pleated media at 85 LPM air flow rate is less than 0.1%. The respirator may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.01%. The respirator may be implemented such that percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 0.001%.The respirator may be implemented such that the pleated media is free of fluorinated compounds.

[0152] The respirator may be implemented such that the pleated media is free of fiberglass.

[0153] The respirator may be implemented such that the pleated media exhibits uniform mechanical properties across the major upstream face.

[0154] The respirator may be implemented such that the pleated media includes a plurality of sharp pleat tips.

[0155] The respirator may be implemented such that the plurality of sharp pleat tips form a zig-zag pattern.

[0156] The respirator may be implemented such that the melt-blown polymeric fibers include polypropylene.

[0157] A filter media for a respiratory protective device, the filter media including: a nonwoven web having a thickness between about 0.3 mm and 2.0 mm, the nonwoven web including a plurality of polymeric melt-blow n fibers, wherein the nonw oven web exhibits a Gurley stiffness of at least 150 milligrams, and wherein the filter media exhibits a quasi-permanent electric charge.

[0158] The filter media may be implemented such that the plurality of polymeric melt-blown fibers exhibit an effective fiber diameter of betw een about 2 pm and about 8 pm.

[0159] The filter media may be implemented such that the plurality of melt-blow n fibers have a fiber solidity of at least about 9%. The filter media may be implemented such that the plurality of melt- blown fibers have a fiber solidity of at least about 12%. The filter media may be implemented such that the plurality of melt-blown fibers have a fiber solidity of at least about 14%. The filter media may be implemented such that the plurality of melt-blown fibers have a fiber solidity of at least about 16%. The filter media may be implemented such that the plurality of melt-blown fibers have a fiber solidity of less than about 20%. The filter media may be implemented such that the nonwoven web exhibits a Gurley stiffness of at least about 200 milligrams. The filter media may be implemented such that the nonwoven web exhibits a Gurley stiffness of at least about 300 milligrams. The filter media may be implemented such that the nonwoven web exhibits a Gurley stiffness of at least about 400 milligrams. The filter media may be implemented such that the nonwoven web exhibits a Gurley stiffness of at least about 500 milligrams. The filter media may be implemented such that the nonwoven web exhibits a Gurley stiffness of less than about 1000 milligrams.

[0160] The filter media may be implemented such that the nonwoven web has a basis weight of at least about 50 grams per square inch. The filter media may be implemented such that the nonwoven web has a basis weight of at least about 70 grams per square inch. The filter media may be implemented such that the nonwoven web has a basis weight of at least about 80 grams per square inch. The filter media may be implemented such that the nonwoven web has a basis weight of at least about 90 grams per square inch. The filter media may be implemented such that the nonwoven web has a basis weight of less than about 120 grams per square inch.

[0161] The filter media may be implemented such that the self-supporting pleated media is free of fluorinated compounds.

[0162] The filter media may be implemented such that the filter media is at least partially resistant to oily aerosols.

[0163] The filter media may be implemented such that the filter media is substantially oil-proof to oily aerosols.

[0164] The filter media may be implemented such that the nonwoven web is free of adhesive.

[0165] The filter media may be implemented such that the nonwoven web is free of fiberglass.

[0166] The filter media may be implemented such that the nonwoven web exhibits unitary' mechanical properties across the major upstream face.

[0167] The filter media may be implemented such that the melt blown polymeric fibers include electret fibers.

[0168] A respirator is presented that includes a mask body, and a filter element housing fluidly connected to the mask body. The filter element housing includes a coupling element configured to mechanically couple to the mask body and a single sheet of pleated filter media. The pleated filter media includes a sheet of nonwoven media that, before pleating, has a basis weight of at least 60 grams per square meter, a solidity' of at least 10%, and a Gurley stiffness of at least 150 mg. The single sheet of pleated filter media has a pleat density of at least about 9 pleats per inch. The filter media includes melt-blown polymeric fiber, wherein the filter element housing houses the single sheet of pleated filter media. The single sheet of pleated filter media is self-supporting such that the filter element housing is free of any type of reinforcing structure or support layer. The single sheet of pleated filter media exhibits a quasi-permanent electric charge.

[0169] The respirator may be implemented such that the melt-blown polymeric fibers have an effective diameter of at least about 2 pm. The respirator may be implemented such that the melt-blown polymeric fibers have an effective diameter of at least about 3 pm. The respirator may be implemented such that the melt-blown polymeric fibers have an effective diameter of at least about 4 pm. The respirator may be implemented such that the melt-blown polymenc fibers have an effective diameter of less than about 7 pm. The respirator may be implemented such that the melt-blown polymeric fibers have an effective diameter of less than about 5 pm.

[0170] The respirator may be implemented such that the pressure drop across a sheet of unpleated filter media is less than 25 mm H2O.

[0171] The respirator may be implemented such that the basis weight of the sheet of nonwoven media is at least about 80 gsm. The respirator may be implemented such that the basis weight of the sheet of nonwoven media is less than about 115 gsm.

[0172] The respirator may be implemented such that the sheet of nonwoven media has a sol i di ty of less than about 16%.

[0173] The respirator may be implemented such that the sheet of nonwoven media has a thickness of at least 0.2 inches.

[0174] The respirator may be implemented such that the sheet of nonwoven media has a thickness of less than 0.5 inches.

[0175] The respirator may be implemented such that the sheet of nonwoven filter media has a Gurley stiffness of less than 500 mg.

[0176] The respirator may be implemented such that the sheet of nonwoven filter media has a percent penetration (DOP) at 85 LPM air flow rate that is less than 0.01%.

[0177] Examples

[0178] Test Procedures

[0179] Effective Fiber Diameter

[0180] The Effective Fiber Diameter (EFD) of a web is evaluated according to the method set forth in Davies, C. N., 'The Separation of Airborne Dust and Particles,' Institution of Mechanical Engineers, London, Proceedings IB, 1952. Unless otherwise noted, the test is run at a face velocity of 13.8 cm / sec for flat filter media. Guriev Stiffness

[0181] Gurley Stiffness is measured using a Gurley Stiffness Tester Model 417 IE (Digital), available from Gurley Precision Instruments, Troy, NY. The Stiffness is measured according to the procedures provided in the operating manual for the Tester. For each material, three separate individual physical samples are tested. Each sample is a flat-web (unpleated) sample, cut (e.g. from roll) to a sample dimension of 2 inches by 1.5 inches. If the sample exhibits an identifiable machine direction (downweb direction), the sample is cut so that the long (test) dimension is crossweb with the machine direction of the sample. The sample bends into the downweb direction during the test. Each individual physical sample is tested two times, cycling back and forth from the left and right side of the sample. Results are averaged and are reported in milligrams of force (Gurley Units).

[0182] % Penetration. Pressure Drop, and Quality Factor

[0183] Percent Penetration, pressure drop, filtration Quality Factor (QF), and related parameters of a filtration media sample are obtained using a challenge aerosol containing either DOP (di oct l phthalate) liquid droplets or NaCl (sodium chloride) solid particulates, in generally similar manner as disclosed in PCT International Publication No. WO 2015 / 199972, published December 30, 2015, and in PCT Publication WO 2015 / 024891, published March 12, 2015, both of w hich are incorporated by reference herein. An Automated Filter Tester AFT Model 8130 (TSI, Inc., St. Paul MN) may be used, with a challenge aerosol that comprises DOP droplets or NaCl particulates, with a mass median diameter in the range of approximately 0.3 pm (e.g., a mass median diameter of approximately 0.26 pm for DOP, and a mass median diameter of approximately 0.33 pm for NaCl). In the following Examples, the challenge aerosol was delivered at a flow rate of 85 liters / min (LPM) to provide a face velocity of 13.8 cm / s, unless otherwise indicated. Testing was performed on flat webs except as noted.

[0184] The particle concentration is measured at the sample inlet and outlet and the Percent Penetration of particles through the filtration w eb is thus obtained, and the pressure drop through the filtration web is monitored by way of transducers e.g. of the general type available from MKS Instruments (Andover, MA). The equation: Equa etion 2 is used to calculate Quality Factor (QF).

[0185] Parameters which may be measured or calculated from such test procedures include initial Percent Penetration, initial pressure drop, and initial Quality Factor QF. Initial parameters are obtained upon initially exposing the filter media sample to the challenge aerosol, as will be well understood by the ordinary artisan. All Percent Penetration and pressure drop numerical values, ranges, etc. that are present in this document (including both the specification and the claims), will be understood to be initial parameters, using DOP, unless otherwise specified. All such numerical values will be understood to be at a face velocity of 13.8 cm / s.

[0186] Loading tests may be performed by continuously challenging the filter with aerosol over a period of time while monitoring penetration and pressure drop; the test may be stopped after a particular loading of particles is reached or after a clear maximum in the penetration is observed and the final Percent Penetration, final pressure drop, and / or final quality factor at the conclusion of the loading test may be recorded. All particle penetration results are reported as Percent Penetration (e.g. a reported value of 80 means 80 %; a reported value of 0. 1 means 0. 1 %). Filtration efficiency (e.g., initial or final) may also be obtained, which is 100 minus the Particle Penetration and is likewise reported in percent.

[0187] Representative Working Examples

[0188] Materials

[0189] Filter media Examples composed of a polypropylene melt-blown nonwoven web having charged electret moieties was made, with the resulting properties listed in Table 1, which also lists pressure drop, % penetration and Gurley stiffness for each Example. Filter media EX-9 and EX-10 w ere calendered after being formed.

[0190] Table 1 : Example Flat-web Filter Media Dimensions and Filtration Results

[0191] Pleating

[0192] Rolls of the media that had been slit to approximately 3 inches (7.5 cm) in lateral width had fold lines formed across the width of the media using a rotary scoring apparatus. Alternately, fold lines were formed using a servo knife pleating machine, manufactured by Roth Composite Machinery. The fold lines were spaced along the longitudinal (downweb) length of the mediate provide a pleat height (after the media was compressed into a pleated configuration) as described in the Examples.

[0193] The media with fold lines, while in a flat configuration, had four beads of liquid hot-melt adhesive (obtained from Truxes Company under the trade designation PF-3165) applied to the major surface of the media. The four upstream beads were applied (by nozzles of a grid melter as the flat media w as moved past the grid melter) as elongate stripes that were spaced across the width of the media and extended along the longitudinal length of the media. Of these four beads, first and second were edge beads that were applied at locations no more than approximately 2-3 mm laterally inward from first and second lateral edges of the media. The third and fourth beads were interior beads that w ere spaced generally similarly equally across the width of the media between the two edge beads (the lateral spacing betw een each pair of beads w as thus in the range of approximately 22-28 mm). Similar beads were simultaneously applied to the (opposing) major surface of the nonwoven web (which surface would eventually provide the downstream face of the pleated media). Each downstream beads was aligned with its corresponding upstream bead, within a lateral distance of approximately 2 mm or less.

[0194] While the adhesive beads were still in liquid form, the scored media was compressed (during which process the media folded along the score lines) to its final pleated configuration of a pleat spacing. During this process, the liquid adhesive penetrated into the pleat valleys as the pleats were formed, and at least substantially filled the pleat valleys and, at the pleat tips, protruded outward beyond the pleat tips a distance estimated to be (on average) approximately 0.5-1 mm. During this process the adhesive was still sufficiently tacky at the surfaces of the beads so that two portions of an adhesive bead, if meeting in a pleat valley during the folding operation, could adequately bond to each other. The adhesive was allowed to harden so that each pair of aligned upstream and downstream beads collectively formed a dam of hardened adhesive.

[0195] The pleated media bearing hardened adhesive dams was then cut into lengths to form pleated filter elements to fit the dimensions of Filter Cartridge 1 and 2. Each pleated filter element was installed into the filter element housings of Filter Cartridges 1 and 2. Since the filter element housing of Filter Cartridge 2 comprised an arcuate receptacle for receiving an arcuate filter element, the pleated filter element for Filter Cartridge 2 was conformed (along a conforming axis that was essentially parallel to the longitudinal axis of the pleated filter element) into an arcuate shape with a radius of curvature estimated to be in the range of approximately 30 cm.

[0196] The pleated filter element for both Filter Cartridges 1 and 2 were slightly oversized in length (e.g. in the range of 2-3 mm) in comparison to the receptacle, so that the noncormgated ends of the filter element were held in the receptacle under slight compression. A bead of glue (moisture-curable polyurethane adhesive, obtained from 3M Company under the trade designation SCOTCH- WELD™ TE040) was applied to the downstream perimeter of the filter element (overlapping onto the adjacent surfaces of the housing) to hold the filter element securely in place. It was noted that in at least some samples the edge beads appeared to at least substantially occlude the corrugated edges of the pleated filter media, so it was believed that satisfactory filtration performance could be achieved with a downstream glue bead only serving to secure the filter element in place (and to seal the noncorrugated edges of the filter element against the abutting walls of the receptacle of the housing) rather than such a downstream glue bead being necessary to seal the cormgated edges of the filter element against air leaks.

[0197] The pleated filter elements, as installed into housings as described above, were evaluated for their performance. The filter media was pleated for insertion into Filter Cartridge 1 which has nominal dimensions of 1.8 inches across pleats and 3 inches along pleats, with each Example having further dimensions, pressure drop (PD) and percent penetration illustrated in Tables 2 and 3. Table 2: Filter Cartridge 1 Dimensions and Penetration Results

[0198] The filter media was also pleated for insertion into a Filter Cartridge 2, which has nominal dimensions of 8.3 inches a DL and 3 inches DP, having further dimensions and penetration illustrated in Table 3.

[0199] Table 3: Filter Cartridge 2 Cartridge Dimensions and Penetration Results

[0200] The foregoing Examples have been provided for clarity of understanding only, and no unnecessary7limitations are to be understood therefrom. The tests and test results described in the Examples are intended to be illustrative rather than predictive, and variations in the testing procedure can be expected to yield different results. All quantitative values in the Examples are understood to be approximate in view of the commonly known tolerances involved in the procedures used.

[0201] It will be apparent to those skilled in the art that the specific exemplary elements, structures, features, details, configurations, etc., that are disclosed herein can be modified and / or combined in numerous embodiments. All such variations and combinations are contemplated by the inventor as being within the bounds of the conceived invention, not merely those representative designs that were chosen to serve as exemplary illustrations. Thus, the scope of the present invention should not be limited to the specific illustrative structures described herein, but rather extends at least to the structures described by the language of the claims, and the equivalents of those structures. Any of the elements that are positively recited in this specification as alternatives may be explicitly included in the claims or excluded from the claims, in any combination as desired. Any of the elements or combinations of elements that are recited in this specification in open-ended language (e.g., comprise and derivatives thereof), are considered to additionally be recited in closed-ended language (e.g., consist and derivatives thereof) and in partially closed-ended language (e.g., consist essentially, and derivatives thereof). Although various theories and possible mechanisms may have been discussed herein, in no event should such discussions serve to limit the claimable subject matter. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned and / or incorporated by reference herein, this specification as written will control.

Claims

What is claimed is:1 . A filter element comprising: a pleated filter media comprising a major upstream face and a major downstream face and comprising a plurality' of pleats with a pleat direction and with a plurality of upstream pleat tips and upstream valleys and a plurality of downstream pleat tips and downstream pleat valleys; wherein the pleated filter media comprises only a single layer of a nonwoven web comprising melt-blown polymeric fibers, the melt-blown polymeric fibers having a fiber solidity of at least 10% and an effective fiber diameter of at least 2 pm; and wherein the pleated filter media is self-supporting.

2. The filter element of claim 1 , wherein the single sheet of nonwoven web has a basis weight of at least about 50 grams per square meter.

3. The filter element of any of claims 1-2, wherein the single sheet of nonw oven web has a thickness of at least about 0.3 mm.

4. The filter element of any of claims 1-3, wherein the single sheet of nonwoven web has a thickness of less than about 2 mm.

5. The filter element of any of claims 1-4, wherein the pleats are ultrasonically scored-pleats, rotary-scored pleats or heat-scored pleats.

6. The filter element of any of claims 1-5, wherein the single sheet of nonwoven web has a Gurley stiffness of at least about 150 milligrams.

7. The filter element of any of claims 1-6, wherein the pleated filter media has a pleat density of at least about 7 pleats per inch.

8. The filter element of any of claims 1-7, wherein the pressure drop across the pleated filter media at 85 LPM air flow rate is less than about 50 mmLhO.

9. The filter element of any of claims 1-8, wherein percent penetration (DOP) of the pleated filter media at 85 LPM air flow rate is less than 1%.

10. The filter element of any of claims 1 -9, wherein the pleated filter media is free of laminating adhesive.1 1. The filter element of any of claims 1-10, wherein the pleated filter media is free of fiberglass.

12. The filter element of any of claims 1-11, wherein the pleat tips are sharp tips.

13. The filter element of any of claims 1-12, wherein the melt-blown polymeric fibers comprise polypropylene.

14. The filter element of any of claims 1-13, wherein a majority of upstream and downstream pleat valleys are at least partially nonoccluded.

15. A filter cartridge for a reusable respiratory device, the filter cartridge comprising: a housing comprising: a coupling element configured to removably couple to the reusable respiratory' device; at least one major surface with an air-permeable area; and wherein the housing is configured such that substantially all of an ambient air flow is forced through the air-permeable area; a single sheet of self-supporting pleated media, wherein the single sheet of self-supporting pleated media exhibits a quasi-permanent electric charge, the self-supporting pleated media comprising: a web of melt-blown polymeric fibers having a fiber solidity of at least 9% and an effective fiber diameter between 2 and 8 pm; and wherein the single sheet of self-supporting pleated media is an unlaminated sheet free of a stiffening layer; and adhesive coupling the pleated media to an interior surface of the housing, wherein the adhesive coupling provides no significant stiffening effect to the sheet of pleated media.

16. The filter cartridge of claim 15, wherein the reusable respirator device is a half-facepiece respirator, and wherein the coupling element is configured to removably couple to the halffacepiece respirator; or wherein the reusable respirator device is a full-facepiece respirator, and wherein the coupling element is configured to removably couple to the full -facepiece respirator; or wherein the reusable respirator device is a powered air-purifying respirator, and wherein the coupling element is configured to removably couple to the powered air-purifying respirator.

17. The filter cartridge of any of claims 15-16, wherein the single sheet of self-supporting pleated media has a basis weight of at least about 50 grams per square meter.

18. The filter cartridge of any of claims 15-17, wherein the single sheet of self-supporting pleated media has a thickness of at least about 0.3 mm.

19. The pleat pack of any of claims 15-18, wherein the single sheet of self-supporting pleated media has a Gurley stiffness of at least 150 milligrams.

20. The filter cartridge of any of claims 15-19, wherein the self-supporting pleated media has a pleat density of at least about 7 pleats per inch.

21. The filter cartridge of any of claims 15-20, wherein the pressure drop across the self-supporting pleated media at 85 LPM air flow rate is less than about 50 mmkbO.

22. The filter cartridge of any of claims 15-21, wherein percent penetration (DOP) of the self- supporting pleated media at 85 LPM air flow rate is less than 1%.

23. The filter cartridge of any of claims 15-22, wherein the self-supporting pleated media is free of fiberglass.

24. The filter cartridge of any of claims 15-23, wherein the pleat tips are sharp tips.

25. The filter cartridge of any of claims 15-24, wherein a majority of upstream and downstream pleat valleys are at least partially nonoccluded.

26. A respirator comprising: a mask body; a filter element housing fluidly connected to the mask body, wherein the filter element housing comprises: a coupling element configured to mechanically couple to the mask body; a single sheet of a pleated filter media having a basis weight of at least 60 grams per square meter, the pleated filter media comprising melt-blown polymeric fiber, wherein the filter element housing houses the single sheet of pleated filter media; and wherein the pleated filter media is self-supporting such that the single sheet of pleated media is free of a stiffening layer, and wherein the single sheet of pleated filter media exhibits a quasi-permanent electric charge.

27. The respirator of claim 26. wherein the mask body is a full-facepiece or a half-facepiece.

28. The respirator of any of claims 26-27, and further comprising a remote unit that comprises the filter element housing, the remote unit being a powered unit comprising a fan and comprising a supply tube that fluidically connects the remote unit to the mask body, whereby filtered air can be delivered from the remote unit to the mask body.

29. The respirator of any of claims 26-28, wherein the single sheet of the pleated filter media is adhered to an interior surface of the filter element housing.

30. The respirator of any of claims 26-29, wherein the pleated filter media has a basis weight of at least 50 grams per square meter.

31. The respirator of any of claims 26-30, wherein the pleated media has a thickness of at least about 0.3 mm.

32. The respirator of any of claims 26-31, wherein the melt-blow n polymeric fiber has an effective fiber diameter of at least about 2 pm, and less than about 12 pm.

33. The respirator of any of claims 26-32, wherein the melt-blown polymeric fiber has a fiber solidity of at least about 9%.

34. The respirator of any of claims 26-33. wherein the pleated media has a Gurley stiffness of at least 150 milligrams.

35. The respirator of any of claims 26-34, wherein the pleated media has a Gurley stiffness of less than about 1000 milligrams.

36. The respirator of any of claims 26-35, wherein the pleated filter media has a pleat density of at least about 7 pleats per inch.

37. The respirator of any of claims 26-36. wherein the pleated media is free of fiberglass.

38. The respirator of any of claims 26-37, wherein the pleated media exhibits uniform mechanical properties across the major upstream face.

39. The respirator of any of claims 26-38, wherein the pleated media comprises a plurality of sharp pleat tips.

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