Fireproof Filter

Abstract

Various disclosed embodiments relate to fire resistant filters and methods of making and using the same. The filters include a fibrous web or sheet comprising fire resistant fibers, where the fire resistant fibers include oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof.

Description

[Background technology]

[0001] Many commercial and residential kitchens install grease filtering or removal systems in exhaust hoods over various types of cooking equipment, including heavily oiled deep friers, grills, griddles, woks, and ovens, where grease can aerosolize and generate excessive heat and flames.

[0002] Baffles are a major component of exhaust hood construction. They are devices inserted into the exhaust hood and act to filter aerosolized grease. The baffle creates perturbations in the air passing through channels in the baffle, which in turn cause droplets of grease to strike the baffle's surface and may condense thereon.

[0003] This system requires that the baffles be removed from the exhaust hood and cleaned periodically. Because the baffles do not capture all of the grease that enters the exhaust hood, the interior of the exhaust hood also needs to be cleaned periodically. Both of these cleaning processes can be time consuming and costly. These cleaning processes often require the use of harsh chemicals that can contaminate food surfaces they may come into contact with. In addition, due to the complexity of cleaning the exhaust hood, this operation typically requires that the kitchen, or at least cooking equipment, is not in use. This often requires that the cleaning be performed during times when the kitchen or business is closed, or that the business be closed to allow for the cleaning opportunity.

[0004] When removing and replacing a baffle, this can be a difficult process for a worker in the kitchen to perform because the baffles are often very heavy and must be held over their head and placed in the correct channel in the exhaust hood system.

[0005] Existing filters or secondary filters are heavy, expensive, and are not backed by baffles, resulting in insufficient fire resistance. Summary of the Invention

[0006] Various embodiments of the present invention provide a filter comprising a fibrous web or sheet comprising fire resistant fibers, the fire resistant fibers comprising oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof.

[0007] Various embodiments of the present invention provide a filter assembly comprising a filter including a fibrous web or sheet that includes fire resistant fibers. The filter assembly also includes a filter frame.

[0008] Various embodiments of the present invention provide a self-supporting filter assembly that includes a fibrous nonwoven web or sheet that includes fire resistant fibers. The fire resistant fibers include OPAN, FR rayon, or a combination thereof. The OPAN, FR rayon, or a combination thereof is at least about 60% by weight of the fibrous web or sheet. The self-supporting filter assembly also includes a filter frame.

[0009] Various embodiments provide a method of using a filter including a fibrous web or sheet including fire resistant fibers, the method including mounting a filter or a filter assembly including a filter therethrough for air to be filtered.

[0010] Various embodiments provide a method of using a filter comprising a fibrous web or sheet comprising fire resistant fibers. The method comprises filtering air through the filter.

[0011] Various embodiments of the present invention provide a method of manufacturing a filter embodiment, the method comprising forming a fibrous web or sheet comprising fire resistant fibers, including OPAN, FR rayon, or combinations thereof.

[0012] In some embodiments, a filter including a fibrous web or sheet including fire resistant fibers, or a method of making or using the same, can provide certain advantages over other filters, at least some of which are unexpected. For example, in some embodiments, the filter can provide better fire resistance than other oleophilic filters. In some embodiments, the filter can provide better acoustics than other filters, and can more effectively attenuate noise effects in ventilation and hood systems. In various embodiments, the filter of the present invention can be lighter in weight, less expensive to manufacture, or a combination thereof, compared to other fire resistant filters. In various embodiments, the lighter weight can correspond to less waste when used in disposable applications, and can provide enhanced safety and easier installation.

[0013] In various embodiments, the fire-resistant filters can have enhanced oleophilic properties compared to other fire-resistant filters, reducing or eliminating the need for cleaning of baffles and air ducts, and correspondingly reducing maintenance costs. In some embodiments, the fire-resistant filters can be disposable or can be cleaned and reused. Reducing grease buildup in the exhaust hood reduces the risk of duct fires. Enhanced capture of grease particles can also reduce air emissions to nearby areas, which can result in buildup on roofs and exposure of nearby areas to grease emissions and odors. Reducing grease buildup in the hood can reduce exposure of workers to the hazards of climbing ladders or equipment to remove and replace standard baffles.

[0014] In various embodiments, the enhanced fire resistance of the filter allows the filter assembly of the present invention, including a filter and including a filter frame, to be fire resistant by providing a larger open area available for filtering and not obscured by the filter frame than other fire resistant filter assemblies that utilize the fire resistance of the filter frame. In various embodiments, the larger open area of ​​the filter assembly of the present invention provides a desired level of fire resistance by increasing the filtering efficiency per surface area of ​​the filter assembly compared to other filter assemblies made with filters that are less fire resistant and require more blocking of the open area by the fire resistant filter frame. In various embodiments, the larger open area allows the filter assembly of the present invention to be more visually appealing than other similar fire resistant filters. [Brief description of the drawings]

[0015] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments of the present invention. [Figure 1A] This is an image of a commercial kitchen with baffles. [Figure 1B] 1 is an image of a baffle used to capture grease. [Figure 2A] FIG. [Figure 2B] FIG. 1 is a cross-sectional view of a conventional baffle. [Diagram 3] 1 illustrates a filter assembly according to various embodiments. [Figure 4] 1 illustrates a filter frame according to various embodiments. [Figure 5A] 1 is an image of a multi-layer filter according to various embodiments. [Figure 5B] 1 is an image of a multi-layer filter according to various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Certain specific embodiments of the disclosed subject matter are described in detail below. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit those claims to the disclosed subject matter.

[0017] Throughout this document, values ​​expressed in range format should be interpreted flexibly to include not only the numerical values ​​expressly set forth as the limits of that range, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were expressly set forth. For example, the range "about 0.1% to about 5%" or "about 0.1% to 5%" should be interpreted to include not only about 0.1% to about 5%, but also each value (e.g., 1%, 2%, 3%, and 4%) and subrange (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the stated range. The statement "about X to Y" has the same meaning as "about X to about Y" unless otherwise specified. Similarly, the statement "about X, Y, or about Z" has the same meaning as "about X, about Y, or about Z" unless otherwise specified.

[0018] In this document, the terms "a," "an," or "the" are used to include one or more unless the context clearly indicates otherwise. The term "or" is used to refer to a nonexclusive "or" unless otherwise specified. The statements "at least one of A and B" or "at least one of A or B" have the same meaning as "A, B, or A and B." In addition, any expressions or terms used herein that are not specifically defined should be understood to be for descriptive purposes only and not for limiting purposes. Any use of section headings is intended to aid in the reading of this document and should not be construed as limiting, and information associated with a section heading may be found within or outside that particular section.

[0019] In the methods described herein, acts may be performed in any order without departing from the principles of the invention, unless a temporal or operational order is explicitly recited. Moreover, unless a claim explicitly recites that certain acts are performed separately, those acts may be performed simultaneously. For example, a claimed act of doing X and a claimed act of doing Y may be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the claimed process.

[0020] As used herein, the term "about" allows for some variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or within the limits of a stated range, and includes the exact stated value or range.

[0021] As used herein, the term "substantially" refers to a majority or majority or 100%, such as at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more. As used herein, the term "substantially free" can mean that the composition has no or insignificant amounts of a material from about 0% to about 5% by weight, or from about 0% to about 1% by weight, or less than about 5% by weight, or less than about 4.5%, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or less than about 0.001% by weight, such that the amount of material present does not affect the material properties of the composition including the material. The term "substantially free" can mean that the composition has an insignificant amount such as less than, equal to, or greater than about 0% to about 5% by weight of the material, or about 0% to about 1% by weight, or less than about 5% by weight, or less than about 4.5%, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or less than about 0.001% by weight.

[0022] 1A shows an image of an exemplary commercial kitchen 100 that includes a cooking surface 102 used to cook a variety of (often greasy) foods at high heat. A ventilated hood system 104 is positioned near the cooking surface to provide an outlet for greasy steam or mist rising from the cooking surface 102. A baffle 105 is positioned within the ventilated hood system 104 near the cooking surface 102, which requires greasy steam rising from the cooking surface 102 to first pass through the baffle and then exit through the ventilated hood system 104.

[0023] FIG. 1B illustrates a conventional baffle 110. Conventional baffles 110 are often made of metal, such as stainless steel, aluminum, or other metals, and can range in weight from 1 kilogram to 3 kilograms. The baffle may have a handle 112 in front of the baffle to aid in positioning and removal of the baffle. Baffles can be very cumbersome to manage when in an overhead vent hood system, especially since the edge 114 of the baffle 110 engages a lip in the vent hood system. Because the baffle is typically located above the user's head and can be bulky and heavy, it can be difficult to properly position the baffle 110 to engage a lip in the vent hood system. Even in an ideal kitchen, appliances or other objects often complicate positioning the baffle, especially in environments with high temperatures and slippery surfaces.

[0024] 2A is a cross-sectional view of ventilation hood system 200. Air (often an oily mist) flows through baffle 220 in the direction of arrow 211 and out exhaust duct 212 in the direction of arrow 213. Baffle 220 is the primary grease recovery element, as the air must exit after passing through exhaust duct 212. Because baffle 220 has traditionally not been very effective at capturing grease, a significant amount of grease typically escapes from the kitchen into the environment and collects in the exhaust duct and outside the building in the area of ​​exhaust duct 212. This can result in environmental contamination, as well as increased fire hazards caused by grease buildup throughout ventilation hood system 200 and on the exterior of the building.

[0025] 2B is a cross-section of a conventional baffle 220. Arrows 225 indicate the movement of oily mist or greasy air around the structure of baffle plate 227. Turbulence caused by air flowing around baffle plate 227 causes grease or oil droplets to come into contact with the baffle plate and collect or condense on the baffle 220. The baffles require periodic cleaning to remove collected oil and are relatively ineffective at collecting oil, resulting in a significant amount of greasy air entering the vent hood system and collecting throughout the system and outside the building in which the system is installed.

[0026] Fireproof Filter In various embodiments, the present invention provides a fire resistant filter. The filter includes a fibrous web or sheet including fire resistant fibers. The fire resistant fibers include oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof. The fibrous web or sheet may be flexible. The filter or fibrous web or sheet may be generally flat in shape, pleated, flat, or a combination thereof. The fibrous web or sheet may form substantially the entirety of the fire resistant filter, or the filter may include other layers, reinforcements (e.g., a filter frame), coatings, etc.

[0027] The filter, or a filter assembly including the filter, may be suitable for mounting into an air filter holder, such as in a slot, using a magnet or adhesive, using mechanical fasteners, and for self-supporting filters, a cover screen may be used that holds the air filter in place via a filter frame or band, or a combination thereof, which may be temporarily or permanently attached.

[0028] In some embodiments, the filter or filter assembly comprising the filter may have a pull tab that extends beyond the filter or filter frame, allowing a user to grasp the pull tab with one hand and the filter frame with the other to separate the filter or filter assembly from the frame. The ability to manually separate the filter from the filter frame with reasonable ease allows the user to reuse or re-use the filter frame and properly dispose of the grease-impregnated filter. In some cases, the filter frame may have a pull tab. Such a pull tab may be used instead of or in addition to a pull tab on the filter or filter assembly. In some cases, the filter frame may be reused or recycled at the core facility. The filter or filter assembly and the filter frame attached to each other using any other attachment mechanism contemplated herein may also comprise a system in which the filter frame can be reused or recycled. In some cases, the filter, filter frame, or the entire assembly may be disposable.

[0029] The fire-resistant filter fibrous web or sheet can pass the Bunsen Burner Flame Test without the aid of any other layers, such as metal baffles, as described in the Examples section of this application. For example, a 10 cm x 10 cm sample of the fibrous web or sheet placed 6 cm above a 10 cm long flame from a natural gas Bunsen burner can remain intact and free of flame penetration after 10 seconds of exposure to the flame, followed by 10 seconds of removal of the flame, followed by another 10 seconds of exposure to the flame. The sample can "char" without burning and still pass the test.

[0030] The fire-resistant fibers forming the fibrous web or sheet can be formed into a fibrous web or sheet in any suitable manner, such that the fibrous web or sheet provides the fire resistance described herein. For example, the fibrous web or sheet can be a nonwoven (e.g., lofted, carded, airlaid, or mechanically bonded, such as spunlaced, needle entangled, or needle tucked), woven, knitted, mesh, or perforated film. The fibrous web or sheet can be bonded (e.g., the fibers are bonded to each other at various locations) or unbonded.

[0031] The fibrous web or sheet may be bonded and may include a thermosetting or melting material that provides some or all of the bonds in the fibrous web or sheet, such as flakes, powders, fibers, or combinations thereof, including those that include any suitable thermoplastic or thermosetting polymer, such as polyester, polyethylene terephthalate (PET), polypropylene (PP), or combinations thereof. After melting or heat bonding, the flakes, powders, or fibers may melt to bond the fibers together. The bonding of the fibrous web or sheet may increase the stability and strength of the filter. The fibrous web or sheet may include any suitable material or fiber in addition to the fire-resistant fiber, including OPAN, FR rayon, or combinations thereof. For example, the fibrous web or sheet may include polyacrylonitrile (PAN), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polypropylene (PP), kapok fiber, poly(lactic acid) (PLA), cotton, nylon, polyester, rayon (e.g., non-flame retardant rayon), wool, or combinations thereof. The fibrous web or sheet may further include coatings, flame retardants, fibers, thermosetting or molten materials (e.g., powders, flakes, or fibers), metal fibers, glass fibers, ceramic fibers, aramid fibers, sorbents, intumescent materials (e.g., fibers or particles), mica, diatomaceous earth, glass bubbles, carbon particles, or combinations thereof. Examples of fibers that can be added include larger diameter fibers that can be added to provide greater bulk and body. Other fibers can be added to provide special properties, such as hollow fibers or sheath-core fibers, which provide the filter with enhanced oleophilic or oleophobic properties. Examples of flame retardants include any polymer designated as flame retardant or "FR" or can include aluminum, polyphosphates, phosphorus, nitrogen, sulfur, silicon, antimony, chlorine, bromine, magnesium, zinc, carbon, or combinations thereof (e.g., as pure materials or as compounds containing the materials). The flame retardant may be a halogen-containing flame retardant or a non-halogenated flame retardant.Examples of coatings or additives include expandable graphite, vermiculite, ammonium polyphosphate, alumina trihydrate (ATH), magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), molybdate compounds, chlorinated compounds, brominated compounds, antimony oxide, organophosphorus compounds, or combinations thereof.

[0032] The fibrous web or sheet may have any suitable overall density, for example, from about 10 to about 400 g / m 2 , or about 80 to about 250 g / m 2 , or about 10 g / m 2 or less, or about 20, 40, 60, 80, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375 g / m 2 , or about 400 g / m 2 The above values ​​can have values ​​that are less than these, equal to these, or greater than these.

[0033] The filter includes at least one layer of a fibrous web or sheet including fire-resistant fibers. The filter may include a single layer of a fibrous web or sheet including fire-resistant fibers, or may include multiple layers of a fibrous web or sheet. The multiple layers may be independent and adjacent or separate within the filter. For example, the filter may include 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more layers of a fibrous web or sheet.

[0034] The filter may include other layers in addition to one or more layers of fibrous webs or sheets comprising fire-resistant fibers. In some embodiments, one major surface of the fibrous web or sheet includes the additional layer and the opposite major surface of the fibrous web or sheet does not include the additional layer. In some embodiments, both major surfaces of the fibrous web or sheet include the additional layer. The one or more layers may be separate and distinct, or may be at least partially blended. One or more layers may be blended with adjacent layers, e.g., with each other, with one or more layers of the fibrous web or sheet comprising fire-resistant fibers.

[0035] The one or more additional layers may be any suitable layer, such as a flame retardant layer (e.g., a thin sheet of a flame retardant material such as Nextel™ Dot Paper, or other thin web composed of ceramic, metal, glass, or other flame retardant / fire resistant fibers), a non-flame retardant layer, a woven layer, a non-woven layer, a metal layer (e.g., a thin metal or foil, of perforated or expanded metal), an adhesive layer, a coating, a powder, an adsorbent layer, a gradient layer (e.g., a gradient layer that draws grease to its interior or edges, using a condensation management film or a heat-induced phase separation material that has a high affinity for oil / grease), a sacrificial layer (e.g., a layer that can be peeled off when saturated with grease and an additional sacrificial layer already present or added after peeling off the disposable layer), an grease-degrading layer (e.g., an enzyme or microbial), a resin layer, a scrim layer, or a combination thereof. The one or more additional layers may each independently comprise a fire retardant, an adhesive, a thermosetting or melting material (e.g., fiber, powder, or flake), a fire resistant fiber, a coated fiber, a powder, a metal, a glass, a ceramic, a metal fiber, a glass fiber, an aramid fiber, a ceramic fiber, an adsorbent, an intumescent material (e.g., fiber or particles), mica, diatomaceous earth, glass bubbles, carbon particles, or a combination thereof. The one or more additional layers may each independently be unbonded, adhesive laminated, thermally bonded, ultrasonically bonded, needled, physically attached with fasteners, or a combination thereof.

[0036] In some cases, the filter may include a material sandwiched between two layers of scrim. In some cases, the scrim may be used to reduce fiber shedding from the filter including fire-resistant fibers, thereby helping to ensure that fibers or other loose materials from the filter do not fall into food preparation or handling areas. Examples of such materials include activated carbon, oil-absorbing particles, vermiculite, or combinations thereof. Examples of scrim materials may include meshes formed from polymers or metals, nonwoven materials made from polymers, fibers (e.g., ceramic, glass, or aramid fibers), perforated films made from polymers or metals, and combinations thereof. The scrim material may optionally be fire resistant, such as those including metal, ceramic, glass, FR rayon, OPAN, and aramid fibers (Kevlar and Normex). The scrim material may be coated with a flame retardant, such as ammonium polyphosphate. Scrim materials that may be coated with a flame retardant may include polyethylene terephthalate (PET) or nylon. In some cases, the filter may include a fire resistant material that surrounds or sandwiches layers of different layers that may be non-fire resistant.

[0037] Fire-resistant fiber The fire resistant filter includes a fibrous web or sheet. The fibrous web or sheet includes a fire resistant fiber. The fire resistant fiber includes OPAN, flame retardant (FR) rayon, or a combination thereof. The fire resistant fiber can be oleophilic or non-oleophilic (e.g., oleophobic, or neither oleophilic nor oleophobic).

[0038] Any suitable percentage of each fire-resistant fiber may be OPAN, FR rayon, or a combination thereof. For example, about 60% to about 100% by weight, or about 90% to about 100% by weight, or about 60% or less, or about 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, 99.9, 99.99% by weight, or about 99.999% by weight or more of each of the fire-resistant fibers may be less than, equal to, or greater than OPAN, FR rayon, or a combination thereof. In some embodiments, the fire-resistant fibers are each independently 100% by weight OPAN or 100% by weight FR rayon, and the fire-resistant fibers are not composed of a blend of materials, but each is substantially formed of one material.

[0039] FR rayon is a regenerated cellulose (viscose) containing one or more flame retardant additives. The flame retardant may be any suitable flame retardant described herein, such as flame retardants containing phosphorus, sulfur, nitrogen, silicon, or combinations thereof. Flame retardants may include organophosphorus, silica, polysilicic acid, complexes of polysilicic acid, or combinations thereof. Flame retardants may include phosphorus and sulfur, such as 2,2'-oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinane]2,2'-disulfide. One or more flame retardants may be incorporated throughout the FR rayon, may be present as a coating on the rayon, or combinations thereof. The one or more flame retardants may form any suitable percentage of the FR rayon, such as less than, equal to, or greater than about 0.001% by weight to about 50% by weight, or about 0.001% by weight to about 25% by weight, or about 0.001% by weight to about 10% by weight, or about 0.001% by weight to about 5% by weight, or less than about 0.001% by weight, or about 0.01, 0.1, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 25, 30, 35, 40, 45% by weight, or about 50% by weight or more.

[0040] The fire resistant fibers OPAN, FR rayon, or combinations thereof may form any suitable percentage of the overall fibrous web or sheet. For example, OPAN, FR rayon, or combinations thereof may be at least about 50% by weight, or at least about 60% by weight, at least about 70% by weight, or about 50% to about 100% by weight, or about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 50% or less, or about 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 95, 96, 97, 98, 99, 99.5, 99.9, 99.99% by weight, or about 99.999% by weight or more of the fibrous web or sheet. 2 , or at least 50 g / m 2 , or about 25 g / m 2 or less than about 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375 g / m 2 , or about 400 g / m 2 The above values ​​may include values ​​less than, equal to, or greater than these values ​​of OPAN, FR rayon, or combinations thereof. References herein to properties per area of ​​a filter are relative to the planar surface area of ​​the major face of the filter.

[0041] The fire resistant fiber can have any suitable diameter and length, thereby providing the fire resistant properties described herein. For example, the fire resistant fiber can have a linear mass density of about 0.5 to about 20 denier, or about 3 to about 7 denier, or about 0.5 denier or less, or about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18 denier, or about 20 denier or more. As used herein, "denier" refers to the unit of linear mass density of the fiber, and refers to the mass in grams per 9000 meters of fiber. As used herein, "dtex" refers to the mass in grams per 10,000 meters of fiber. The refractory fibers may have a length that is less than, equal to, or greater than about 0.001 cm to about 10 cm, or about 2 cm to about 8 cm, or about 0.001 cm or less, or about 0.01, 0.1, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 cm, or about 10 cm or more.

[0042] Filter assembly with fire-resistant filter - Patents.com In various embodiments, the present invention provides a filter assembly. The filter assembly includes an embodiment of a fire-resistant filter including a fibrous web or sheet including fire-resistant fibers. The filter assembly also includes a filter frame. The filter frame may be flexible or rigid. The filter frame may provide structural support for the filter assembly. While the fibrous web or sheet including fire-resistant fibers is typically flexible, the filter frame may be a rigid, self-supporting structure that, when combined with a filter including fire-resistant fibers, provides a rigid and self-supporting filter assembly.

[0043] The filter frame may be external to the filter, internal to the filter (e.g., not extending outside or around the edges of the filter), or a combination thereof. The filter frame may include supporting cross members at the front, back, or both sides of the filter formed from a thin material. The filter frame may have a mesh or expanded metal structure with or without a frame structure around the perimeter of the filter frame. The filter frame may have a lattice-like profile when viewed from a major surface and may be flat or textured. For example, FIG. 4 illustrates a filter frame 300 having a lattice-like profile. The frame or mesh structure may be formed from metal, resin, foam, clay, silica, or a combination thereof. The filter frame may be coated or uncoated.

[0044] The filter frame and the filter can be secured to one another. For example, the filter frame can be secured within an interior of the filter, the filter frame can be secured to one or more portions of an exterior of the filter, or a combination thereof. The filter frame can be secured to the filter in any suitable manner, such as using ultrasonic bonds, adhesives, thermal bonds, mechanical attachment mechanisms, or a combination thereof.

[0045] 3 illustrates an embodiment of a filter assembly with a fire-resistant filter. A self-supporting filter assembly or frame is generally rigid so that when a user holds it horizontally from one edge or corner, it maintains substantially the same shape as if it were resting on a flat surface. An embodiment of the filter assembly can be used in place of a baffle in a grease vent hood system.

[0046] The filter assembly 300 is positioned relative to an x-axis 310, a y-axis 320, and a z-axis 330. The filter assembly 300 has two main parts, a filter frame 340 and a filter 350, which include a fibrous web or sheet including fire-resistant fibers. As shown in FIG. 3, the filter frame 340 is disposed on one major side of the filter 350. Although the filter frame 340 does not extend to contact the edge of the filter 350 as shown in FIG. 3, in some cases, the filter frame 340 may extend to contact the edge of the filter 350. In some cases, the filter frame 340 may extend beyond the edge of the filter 350 to overlap a frame in the filter's ventilation hood or with an adjacent filter. In some cases, this overlap can be used to form a loose seal or gasket in a ventilation hood or system. In this case, the edge of the filter 350 may not extend to the second major side of the filter.

[0047] In some embodiments, the filter frame may be flat. In other embodiments, the filter frame may be textured. For example, the filter frame 340 has a plurality of peaks 351 and a plurality of valleys 352. The plurality of peaks 351 and the plurality of valleys extend in two dimensions, such that when a cross section of the filter assembly 300 is taken parallel to the x-axis 310 or parallel to the y-axis 320, each cross section includes the plurality of peaks 351 and the plurality of valleys 352. The height difference between the peaks 351 and the valleys 352, as measured along the z-axis 330, may vary based on the embodiment. In some cases, the height difference may be the same between any selected peak 351 and any selected valley 352. In other examples, the peaks 351 and the valleys 352 may be of various heights. In one example, the height difference between one of the plurality of peaks 351 and one of the plurality of valleys 352 is greater than 0.75 cm. This may be greater than 1 cm, greater than 1.5 cm, greater than 2 cm, greater than 2.5 cm, greater than 3 cm, greater than 3.5 cm, greater than 4 cm, or greater than 5 cm. In some cases, the height difference between one of the peaks 351 and one of the valleys 352 may be less than 10 cm. In some cases, where the height difference between the peaks 351 and valleys 352 varies depending on which peaks 351 and valleys 352 are selected, the height difference may be measured as the maximum distance along the z-axis between any peak 351 and any valley 352.

[0048] The filter can substantially conform to the shape of the filter frame. For example, filter 350 can substantially conform to peaks 351 and valleys 352 of filter frame 340, such that in some cases filter 350 can be secured to one or more of peaks 351 and one or more of valleys 352. Filter 350 can generally follow the curvature of filter frame 340, and in some cases filter 350 can contact the filter frame at peaks 351 and valleys 352.

[0049] The filter frame can be formed of or coated with any suitable material or materials that provide the filter assembly with sufficient structural stability, fire resistance, or combinations thereof. The filter frame may include aluminum, stainless steel, tin, copper, glass, fiberglass, polyimide (PI), polybenzoxazole (PBO), polybenzimidazole (PBI), polybenzothiazole (PBT), polyetherimide (PEI), polyethylene terephthalate polyester (PET), nylon, low density polyethylene (LDPE), high density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), polyethersulfone (PES), acrylonitrile butadiene styrene (ABS), or combinations thereof. The filter frame may have flame retardant properties, may be formed from a flame retardant material, or may include a flame retardant additive or coating.

[0050] The filter frame may block a portion of the filter's surface area available for filtering. However, in various embodiments, the fire-resistant properties of the filter, including the fibrous web or sheet containing fire-resistant fibers, allow the use of the filter frame to provide a desired level of overall fire resistance for the filter assembly over other filter assemblies that use filters with lower levels of fire resistance. For example, the filter frame may block less than about 50% of the filter's surface area, or between about 10% and about 50% of the filter's surface area, or less than about 10%, or less than, equal to, or more than about 15, 20, 25, 30, 32, 34, 36, 38, 40, 42, 44, 45, 46, 47, 48, 49, 49.5, 49.9%, or about 49.99% of the filter's surface area. The filter frame may include greater than 50% open area (e.g., area unobstructed by the filter frame or by other barriers, thereby making the area available for filtering), or about 50% to about 90% open area, or about 50% or more, or less than, equal to, or more than about 51, 52, 53, 54, 55, 56, 58, 60, 62, 64, 66, 68, 70, 75, 80, 85, 86, 87, 88, 89%, or about 90% or more open area.

[0051] The filter assembly, including the filter frame and the filter, can have a wide range of aesthetic variations. For example, they may range in color, texture, surface finish, etc. In some embodiments, the filter may have a different color than the filter frame. In some cases, the color can be selected to reduce the visible effects of use over time, such as those caused by grease buildup in the filter. In other cases, the color can be selected to blend the filter assembly with the surrounding vent hood. The filter may include multi-colored fibers to create a textured appearance. The filter frame may have a coating to change the color and appearance. One example is a metal coating to provide a lightweight resin structure with a metallic appearance. Variations can be manufactured in the materials used for either the filter frame, the filter, or the mounting mechanism between the filter frame and the filter.

[0052] How to Use a Fireproof Filter Various embodiments provide a method of using a fire-resistant filter comprising a fibrous web or sheet comprising fire-resistant fibers. The method may be any suitable method of using an embodiment of a fire-resistant filter. The method may include mounting the filter, or a filter assembly comprising the filter, in an air hood or air duct, or the like, for air to be filtered therethrough. The method may include filtering air through the filter, or a filter assembly comprising the filter. The method may include any one or any combination of the mounting or filtering steps.

[0053] A method for producing a fire-resistant filter. Various embodiments provide a method of manufacturing a fire resistant filter comprising a fibrous web or sheet comprising fire resistant fibers. The method may be any suitable method of forming an embodiment of a fire resistant filter. The method may include forming a fibrous web or sheet comprising fire resistant fibers, including OPAN, FR rayon, or a combination thereof. The method of manufacturing a fire resistant filter may include combining the fibrous web or sheet with other layers, reinforcements (e.g., a filter frame), coatings, etc. The method may include combining the fibrous web or sheet with a filter frame to form an embodiment of a filter assembly described herein. The method may include any one or combination of forming or combining steps. EXAMPLES

[0054] Various embodiments of the present invention may be better understood by reference to the following examples, which are provided by way of illustration and are not intended to limit the invention to the examples described herein.

[0055] [Table 1]

[0056] Example 1. Preparation of nonwoven fabric Representative example airlaid nonwoven webs were prepared comprising a blend of 70% by weight Fiber 1 and 30% by weight bonding fiber. The webs were formed using a conventional airlaid web former (available from Rando Machine Company, Macedon, NY under the trade designation "RANDO WEBBER") targeting a nominal basis weight in the range of 100 grams per square meter (gsm). When formed on the Rando-WEBBER equipment, the collected fibers were supported on a porous belt and then collected by winding onto a 3" core. The thickness of the output web was estimated to be in the range of about 10-20 mm.

[0057] Heat set webs. When formed on a Rando-WEBBER apparatus, the recovered fibers were supported on a porous belt and passed through a heating apparatus that pulled hot air (set at 160°C (320°F)) through the thickness of the recovered fibers from the air side to the belt side (i.e., from top to bottom). The belt speed was 1.82 m / min (6 ft / min). This resulted in sufficient fiber-to-fiber melt bonding that the resulting web became a self-supporting web that could be removed from the belt and subjected to further processing as described below.

[0058] Needle-punched web. The web was needle-punched using a conventional needle-punch machine (available under the trade designation "DILO" from Dilo, Germany) at approximately 15 punches / cm using RB barbed needles, size 15X18x36x3.5 (available from Foster Needle Company, Inc., Manitowoc, WI). 2 The mat was punched through its entire thickness with barbed needles. The needle punched nonwoven web had a thickness of about 10-20 mm (1 / 16 inch).

[0059] A list of the nonwovens prepared is shown in Table 2. The nonwovens prepared with bonding fibers were heat set as described above. The individual nonwovens were needled as described above. Multi-layer webs containing two (or more) nonwovens were combined (laminated) such that the inner surface was in contact with the inner surface of a second nonwoven web. Layer 1 represents the front side of the composite web. The multi-layer webs prepared are shown in Table 3.

[0060] [Table 2]

[0061] [Table 3]

[0062] Figure 5A shows a photograph of layer 2 (polyester fibers 3) of multi-layer web 1. Figure 5B shows a photograph of layer 1 (OPAN fibers 1) of multi-layer web 1.

[0063] Example 2. Testing of web fire resistance properties. The nonwoven and multi-layer webs prepared from Example 1 were tested for fire resistance properties according to the Bunsen Burner Flame Test. A horizontal ring clamp with an 8 cm diameter opening was mounted on a ring stand. An Eisco natural gas Bunsen burner was placed under the ring clamp and the clamp height was adjusted so that the clamp was 6 cm from the top of the burner. A 10 cm by 10 cm cut web sample was placed on the ring clamp. A blue flame was determined to be 10 cm long by measuring from the top of the burner to the flame tip. The lit Bunsen burner was moved under the sample positioned on the ring clamp. The flame was maintained on the sample for 10 seconds. The flame was removed from the sample for 10 seconds and then placed back under the sample / ring clamp for an additional 10 seconds. A web that passes this test remains intact and the blue flame from the burner does not penetrate the sample, meaning that the sample acts as a barrier to the flame and the other side of the sample does not burn or physically degrade during the test. A web that fails the test has the flame penetrate the sample, melt and drip, or continues to burn for more than 3 seconds after the flame is removed. If the web contains a meltable polymer, the material may melt and degrade, but the flame does not penetrate, thereby allowing the web to act as a flame barrier. The meltable polymer may be sacrificed during a fire event.

[0064] The results from the Bunsen burner flame tests on nonwoven fabrics A-G and multilayer webs 1-2 are summarized in Table 4.

[0065] [Table 4]

[0066] Nonwoven G immediately fails due to burning and dripping of the sample. Similarly, Multilayer Web 2 also fails the flame test. In Multilayer Web 1, Nonwoven A acts as a fire barrier, maintaining the shape of the web and preventing any dripping.

[0067] Example 3. Testing Flame Penetration in UL11046 Flame Cans Selected nonwoven and multi-layer webs from Example 1 were tested in a more vigorous flame penetration experiment according to ANSI / UL 1046 Standard, 4th edition, 2010 (Standard for Grease Filters for Exhaust Ducts). Single and multi-layer nonwoven webs were immersed in a bath of oil (Crisco® Frying Oil Blend) until saturated. The loose webs were then clamped to a 20" x 20" metal frame between two perforated metal sheets (Grainger, 22-gauge, 79% open area). The webs were subjected to flame penetration testing using the equipment settings and test method outlined in ANSI / UL 1046. Briefly, the grease-soaked filters were packed into a cylinder and subjected to 4,000 BTU / min from a lit natural gas burner for 3 minutes under a constant 200 fpm air flow. A passing web must remain intact and be easy to remove, and the flames must not penetrate more than 18 inches with any individual flame lasting more than 1.0 second, or cumulative flames totaling more than 20.0 seconds.

[0068] Results from the flame tube tests on nonwovens H, J, and multi-layer web 3 are summarized in Table 5.

[0069] [Table 5]

[0070] All three nonwoven webs in Table 5 pass the flame tube test according to the apparatus and method in ANSI / UL 1046. However, the metal framed assembly (frame + front / rear perforated sheets) immediately fails the test and does not prevent flame penetration. The flame barrier performance of these nonwovens utilizes only their fire resistant properties and construction without traditional baffles.

[0071] The terms and expressions used are used as terms of description rather than limitation, and when using such terms and expressions, there is no intention to exclude the features shown and described or equivalents of portions thereof, and it is understood that various modifications are possible within the scope of the embodiments of the present invention. Thus, although the present invention has been specifically disclosed by specific embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be employed by those skilled in the art, and such modifications and variations are considered to be within the scope of the embodiments of the present invention.

[0072] Exemplary embodiments. The following exemplary embodiments are presented, the numbering of which is not to be construed as indicating any degree of importance.

[0073] A first embodiment is a filter, A filter is provided that includes a fibrous web or sheet that includes fire resistant fibers, the fire resistant fibers including oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof.

[0074] Embodiment 2 provides the filter of embodiment 1, wherein about 60% to about 100% by weight of each of the fire resistant fibers is independently OPAN or FR rayon.

[0075] Embodiment 3 provides the filter of embodiment 1 or 2, wherein the fire resistant fiber comprises FR rayon.

[0076] Embodiment 4 provides the filter of any one of embodiments 1 to 3, wherein the fire-resistant fiber comprises OPAN.

[0077] Embodiment 5 provides the filter of any one of embodiments 1 to 4, wherein the fibrous web or sheet passes a Bunsen burner flame test.

[0078] Embodiment 6 provides a filter according to any one of embodiments 1-5, wherein a 10 cm x 10 cm sample of the fibrous web or sheet, placed 6 cm above a 10 cm long flame from a natural gas Bunsen burner, remains intact and is not penetrated by the flame after 10 seconds of exposure to the flame, followed by 10 seconds of removal of the flame, followed by an additional 10 seconds of exposure to the flame.

[0079] Embodiment 7 provides the filter of any one of embodiments 1 to 6, wherein the fibrous web or sheet is a nonwoven fabric.

[0080] Embodiment 8 provides the filter of any one of embodiments 1 to 7, wherein the fibrous web is bonded.

[0081] Example 9 provides the filter of example 8, wherein the fibrous web comprises a thermoset or molten material.

[0082] Embodiment 10 provides the filter of any one of embodiments 1 to 9, wherein the fire resistant fiber is lipophilic or lipophobic.

[0083] Embodiment 11 provides the filter of any one of embodiments 1-10, wherein the OPAN, FR rayon, or combination thereof is at least about 50% by weight of the fibrous web or sheet.

[0084] Embodiment 12 provides the filter of any one of embodiments 1-11, wherein the OPAN, FR rayon, or combination thereof is at least about 60% by weight of the fibrous web or sheet.

[0085] Embodiment 13 is a fibrous web or sheet having a fiber density of at least 25 g / m 2 The filter according to any one of embodiments 1 to 12 is provided, which comprises OPAN, FR rayon, or a combination thereof.

[0086] Embodiment 14 is a fiber web or sheet having a fiber density of at least 50 g / m 2 The filter according to any one of embodiments 1 to 13 is provided, which comprises OPAN, FR rayon, or a combination thereof.

[0087] Embodiment 15 provides the filter of any one of embodiments 1 to 14, wherein the fire-resistant fiber has a linear mass density of about 0.5 to about 20 denier.

[0088] Embodiment 16 provides the filter of any one of embodiments 1 to 15, wherein the refractory fiber has a linear mass density of about 3 to about 7 denier.

[0089] Embodiment 17 provides the filter of any one of embodiments 1 to 16, wherein the refractory fiber has a length of about 0.001 to about 10 cm.

[0090] Embodiment 18 provides the filter of any one of embodiments 1 to 17, wherein the refractory fiber has a length of about 2 cm to about 8 cm.

[0091] Embodiment 19 provides the filter of any one of embodiments 1-18, wherein the fibrous web or sheet further comprises polyacrylonitrile (PAN), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polypropylene (PP), kapok fiber, poly(lactic acid) (PLA), cotton, nylon, polyester, rayon, wool, or a combination thereof.

[0092] Example 20 provides the filter of any one of Examples 1 to 19, wherein the fibrous web or sheet further comprises a coating, a flame retardant, a fiber, a thermoset material, a melt material, a metal fiber, a glass fiber, a ceramic fiber, an aramid fiber, an adsorbent, an intumescent material, mica, diatomaceous earth, glass bubbles, carbon particles, or a combination thereof.

[0093] In a twenty-first embodiment, the fibrous web or sheet has a fiber density of about 10 to about 400 g / m 2 The filter according to any one of embodiments 1 to 20 is provided, wherein

[0094] In embodiment 22, the fibrous web or sheet has a fiber density of about 80 to about 250 g / m 2 The filter according to any one of embodiments 1 to 21 is provided, wherein

[0095] Embodiment 23 provides a filter according to any one of embodiments 1 to 22, which is pleated, flat, or a combination thereof.

[0096] Embodiment 24 provides the filter of any one of embodiments 1 to 23, comprising a single layer, fibrous web or sheet.

[0097] Embodiment 25 provides a filter according to any one of embodiments 1 to 24, comprising a multi-layer fibrous web or sheet.

[0098] Embodiment 26 provides the filter of any one of embodiments 1 to 25, further comprising one or more additional layers, each independently separate or at least partially blended, each independently being a flame retardant layer, a non-flame retardant layer, a woven layer, a nonwoven layer, a metal layer, an adhesive layer, a coating, a powder, an adsorbent layer, a gradient layer, a sacrificial layer, an oleolytic layer, a resin layer, a scrim layer, or a combination thereof.

[0099] Embodiment 27 provides the filter of embodiment 26, wherein the one or more additional layers each independently comprise a flame retardant, an adhesive, a thermosetting material, a melting material, a fire resistant fiber, a coated fiber, a powder, a metal, a glass, a ceramic, a metal fiber, a glass fiber, an aramid fiber, a ceramic fiber, an adsorbent, an intumescent material, mica, diatomaceous earth, glass bubbles, carbon particles, or a combination thereof.

[0100] Embodiment 28 provides the filter of embodiment 26 or 27, wherein the one or more additional layers are each independently unbonded, adhesively laminated, thermally bonded, ultrasonically bonded, needled, physically attached by fasteners, or a combination thereof.

[0101] Embodiment 29 provides the filter of any one of embodiments 1 to 28, wherein one major surface of the fibrous web or sheet comprises the additional layer and an opposite major surface of the fibrous web or sheet does not comprise the additional layer.

[0102] Embodiment 30 provides the filter of any one of embodiments 1 to 29, wherein both major surfaces of the fibrous web or sheet comprise an additional layer.

[0103] Embodiment 31 provides a filter according to any one of embodiments 1 to 30, wherein the filter can be mounted in an air filter holder, such as in a slot, using a magnet or adhesive, using mechanical fasteners, and for self-supporting filters, a cover screen is used to hold the air filter in place via a filter frame or band, or a combination thereof, which can be temporarily or permanently attached.

[0104] Embodiment 32 is a filter assembly, comprising: A filter according to any one of embodiments 1 to 31, and A filter assembly is provided that includes a filter frame.

[0105] Embodiment 33 provides a filter assembly according to embodiment 32, which is a rigid, self-supporting structure.

[0106]

[0041] Embodiment 34 provides the filter assembly of embodiment 32 or 33, wherein the filter frame comprises aluminum, stainless steel, tin, copper, glass, fiberglass, polyimide (PI), polybenzoxazole (PBO), polybenzimidazole (PBI), polybenzothiazole (PBT), polyetherimide (PEI), polyethylene terephthalate polyester (PET), nylon, low density polyethylene (LDPE), high density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), polyethersulfone (PES), acrylonitrile butadiene styrene (ABS), or a combination thereof.

[0107] Embodiment 35 provides the filter assembly of any one of embodiments 32-34, wherein the filter frame comprises a flame retardant additive.

[0108] Example 36 provides a filter assembly according to any one of Examples 32 to 35, wherein the filter frame is secured to the filter using ultrasonic bonding, adhesive, thermal bonding, mechanical attachment mechanisms, or combinations thereof.

[0109] Embodiment 37 provides a filter assembly according to any one of claims 32 to 36, wherein the filter frame blocks less than about 50% of the surface area of ​​the filter.

[0110] Embodiment 38 provides a filter assembly according to any one of claims 32 to 37, wherein the filter frame blocks between about 10% and less than about 50% of the surface area of ​​the filter.

[0111] Embodiment 39 provides a filter assembly according to any one of embodiments 32-38, having an open area of ​​greater than about 50%.

[0112] Embodiment 40 provides a filter assembly according to any one of embodiments 32-39 having an open area of ​​from greater than about 50% to about 90% or less.

[0113] Embodiment 41 is a self-supporting filter assembly, comprising: A fibrous nonwoven web or sheet comprising fire resistant fibers, the fire resistant fibers comprising oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof, the OPAN, FR rayon, or a combination thereof being at least about 60% by weight of the fibrous web or sheet; and A self-supporting filter assembly is provided that includes a filter frame.

[0114] A forty-second embodiment is a method for using the filter according to any one of the first to thirty-first embodiments, comprising the steps of: Attaching a filter or a filter assembly according to any one of embodiments 32-40 comprising a filter for air to be filtered therethrough.

[0115] A forty-third embodiment is a method for using the filter according to any one of the first to thirty-first embodiments, comprising the steps of: Filtering air through a filter or a filter assembly according to any one of embodiments 32-40 comprising a filter.

[0116] Embodiment 44 is a method for producing a filter according to embodiment 1, comprising the steps of: forming a fibrous web or sheet comprising fire resistant fibers, the fire resistant fibers comprising OPAN, FR rayon, or a combination thereof.

[0117] Embodiment 45 provides a filter, a filter assembly, or a method according to any one or any combination of embodiments 1 to 44, optionally configured such that all recited elements or options are available or selectable therefrom.

Claims

1. a filter comprising a fibrous web or sheet comprising fire-resistant fibers; a filter frame disposed on a major side of the filter; A filter assembly comprising: The fire resistant fiber comprises oxidized polyacrylonitrile (OPAN); The fiber web or sheet has a density of 400 g / m ２ and having an overall density of less than The filter frame has a plurality of peaks and a plurality of valleys extending in two different dimensions.

2. 10. The filter assembly of claim 1, wherein the fibrous web or sheet passes a Bunsen burner flame test.

3. The filter assembly of claim 1 , wherein the fibrous web or sheet is a nonwoven fabric.

4. 1. A self-supporting filter assembly comprising: A filter comprising a fibrous nonwoven web or sheet comprising fire resistant fibers, the fire resistant fibers comprising oxidized polyacrylonitrile (OPAN), flame retardant (FR) rayon, or a combination thereof, the OPAN, FR rayon, or a combination thereof being at least about 60% by weight of the fibrous web or sheet; and a filter frame disposed on a major side of the filter, the filter frame having a plurality of peaks and a plurality of valleys extending in two different dimensions; 1. A self-supporting filter assembly comprising:

5. The filter assembly of claim 1 , wherein the filter substantially conforms to a shape of the filter frame.

Images