Thermally splittable bicomponent fiber filter media

Abstract

A filter medium, manufacturing method, and filter are disclosed. The filter medium includes fibers that can be thermally split to reduce the fiber size of at least a portion of the fibers within the filter medium. This fiber size reduction increases the overall efficiency of such filters in capturing contaminants, particularly contaminants having a size range of about 0.1 to about 10 microns, without compromising other important filter properties. The filter medium includes one or more bicomponent fibers, each having a first component and a second component. The first component includes a thermoplastic elastomeric material and a thermoplastic material and has a higher shrinkage ratio / percentage / rate than the second component, such that application of heat or thermal energy to the fibers causes at least a portion of the first component to separate from the second component.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This disclosure relates generally to filter media having improved performance characteristics, and more particularly to filter media incorporating thermally splittable bicomponent fibers. [Background technology]

[0002] Liquid and gas filters capture many different types of contaminants from air, water, etc. For example, air filters generally include a filter media comprising a fibrous or porous material that removes solid particles such as dust, pollen, mold, and bacteria from the air. The two main types of air filtration devices are surface filters and depth filters. Surface filters, such as membranes or films, act as a barrier to contaminants, capturing them before they enter the media structure. These surface filters typically have submicron pore sizes and narrow pore size distributions. Surface filters tend to have relatively high particle capture efficiencies. However, they also have relatively high pressure drop and low dust-loading capacities. The high pressure drop reduces the airflow through the filter. The low dust-loading capacity significantly shortens the filter's lifespan. Therefore, surface filters have limited application in the air filtration industry. Depth filters are commonly employed in air filtration devices with medium to high efficiency, low pressure drop, and relatively high dust-loading capacity. Depth filters typically employ various types of fibers that can be formed into a web or other nonwoven structure with tortuous paths between the fibers through which gas, such as air, flows. Particulate matter in the gas flowing through the web paths is retained on the upstream side of the web or within the tortuous paths of the web due to the particle size relative to the diameter of the path.

[0003] Traditional residential and commercial air filters, such as HVAC filters, are typically rated by the filter's ability to capture particles between approximately 0.3 and 10 microns. This rating, called the Minimum Efficiency Reporting Value, or MERV, was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). MERV ratings range from 1 to 16, with higher numbers indicating greater efficiency in capturing a particular type of particle. It is also common to compare efficiency values ​​by particle size within the airstream under test. Values ​​of E3, E2, and E1 indicate particle efficiency at 3-10 microns, 1-3 microns, and 0.3-1 microns, respectively. Contaminants come in a wide range of sizes. However, contaminants smaller than 1 micron are the most harmful particles to humans and are relatively difficult to filter. For example, traditional mechanical air filters typically report a MERV rating of approximately 8 to 10 for their fibrous filter media. These filter media typically have fiber sizes that are not small enough to capture submicron particles, such as viruses and other harmful pathogens. Furthermore, amid the current COVID-19 pandemic, ASHRAE has officially begun recommending that certain high-efficiency air filters be given a MERV rating of 13 to effectively protect against airborne infections. Therefore, methods to improve the capture of submicron particles in filter media are essential.

[0004] Current technology for manufacturing fibers designed for use in filters is limited to producing a minimum size of about 1.7 dtex to about 5.6 dtex (e.g., by carding). Due to the difficulty of producing fibers below a certain size, the filtration industry has focused on two different methods to improve the capture of these submicron particles: electrostatic forces and the use of nanoparticles within filter media. Electrostatic filters are formed by electrostatically charging fibers within a fibrous material using tribocharging, corona discharge, hydrocharging, electrostatic fiber spinning, or other known methods. Electrostatic or "electret" filter media improves efficiency without necessarily increasing the amount of force required to force air through the filter media. The "pressure drop" of a filter media refers to the drop in pressure from the upstream side to the downstream side of the filter media. The more difficult it is to force air through the filter media, the greater the pressure drop and the greater the energy required to force air through the filter media. Therefore, it is generally advantageous to reduce or maintain pressure drop while increasing the filter's contaminant capture capacity.

[0005] Electrostatic filters are most effective at capturing submicron particles, reasonably effective at capturing particles between 1 and 3 microns in size, and minimally effective at capturing larger particles between 3 and 10 microns. Electrostatic fibers are commonly used in many filtration applications, such as face masks and high-efficiency filters for filtering viruses and other submicron contaminants. However, one drawback of electrostatic filters is that the electrostatic charge decays over time and with filter use. Therefore, the filter's efficiency decreases relatively quickly, resulting in a shorter lifespan. For example, an electrostatic filter with an initial MERV rating of 13 may lose at least two to three MERV points after the electrostatic force decays. This can compromise the integrity of the filter and partially or completely inhibit its ability to capture submicron particles. Another drawback with certain electrostatically charged filters is that the materials currently used in these filters are limited in the amount of charge (or charge density) that can be generated on the fibers. The lower the electrostatic charge within the filter, the greater the penetration of contaminants. This limitation reduces the filter's overall efficiency in capturing these contaminants.

[0006] Another method for capturing submicron contaminants is to use nanoparticles in combination with fibers. Filtration systems can employ filter media containing relatively large fibers with diameters measured in micrometers and relatively small nanoparticles. The nanoparticles increase the surface area within the filter media for particle capture by reducing the overall fiber size within the filter media. The nanoparticles also tend to collapse together, increasing the packing density within the filter media. It has been shown that even small amounts of nanometer-sized fibers formed into a layer on a microfiber material can improve the filtration properties of the material. While existing filter media incorporating nanoparticles have improved the relative efficiency of these filters, the commercial potential of these filters has been limited for certain applications because the nanoparticles are generally dispersed on the surface of a fibrous material, and this relatively thin layer of nanoparticles on the filter surface provides only limited filtration of particles and has a relatively low dust retention capacity. Summary of the Invention

[0007] While filters incorporating electrostatic forces and / or nanoparticles within the filter media have shown promise, there is room for improvement. Therefore, what is needed are improved filter media for liquid and / or gas filters. It would be particularly desirable to improve the efficiency of such filters in capturing contaminants having a particle size range of about 0.1 to 1 micron (i.e., E1 particles) without compromising the overall cost of the filter or its lifespan, dust holding capacity, or other important filter properties, such as filter pressure drop or air flow rate.

[0008] The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is not intended to identify essential elements of the claimed subject matter or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later.

[0009] Filter media and filters are provided that include bicomponent fibers that can be thermally split to reduce the fiber size of at least some components of the fibers within the filter media. This fiber size reduction increases the overall efficiency of such filters in capturing contaminants without compromising other important properties of the filter. Systems and methods for manufacturing such filter media and filters are also provided. In one embodiment, the filter media comprises one or more bicomponent fibers, each having a first component and a second component, wherein the first component comprises a thermoplastic elastomeric material and a thermoplastic material and has a higher shrinkage percentage than the second component such that upon application of heat or thermal energy to the fibers, at least a portion of the first component separates from the second component.

[0010] In some embodiments, the first component after splitting has a size of less than about 1.5 dtex, or about 0.005 to about 0.05 dtex, or about 0.01 to about 0.02 dtex. The term dtex, as used herein, refers to the mass in grams per 10,000 meters of fiber. The first component may have a maximum dimension of about 1 to 10 microns, or about 3 to 5 microns. Reducing the size of the first component separating from the bicomponent fibers can provide smaller filaments or fibers within the filter media that are difficult, if not impossible, to process with current technology. For example, staple fibers less than 1.5 denier cannot currently be processed through conventional carding processes without significant problems. Splitting the structure in depth increases the efficiency of the filter media, particularly in capturing contaminants in the particle size range of about 0.1 to 1 micron (i.e., E1 particles) and 1 to 3 microns (i.e., E2 particles). In embodiments, the melting point of the first component is about 100° C. to about 200° C., which is lower than the melting point of the second component, which may be higher than about 200° C. The melt flow rates (MFR) of the first and second components are preferably about 10 to 50 g / 10 min. In embodiments, the thermoplastic elastomer material in the first component is less than about 25% by weight of the first component, or about 10 to about 20% by weight of the first component, preferably about 15%. Applicants have found that reducing the total amount of thermoplastic elastomer material in the first component reduces the tackiness of the material in that component, allowing for separation of the first component from the second component during heating.

[0011] Suitable thermoplastic elastomer materials for the first component include styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymer elastomers such as Hytrel® (a plasticizer-free thermoplastic polyester elastomer produced by DuPont Corporation), thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof. In a preferred embodiment, the thermoplastic elastomer material comprises an olefin block copolymer. Suitable thermoplastic materials for the first component include polyolefins, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, CoPET, PLA, PHB, polyamides, and combinations thereof. In a preferred embodiment, the thermoplastic material in the first component comprises PP resin, and the thermoplastic material in the second component comprises CoPET, PET, PBT, PLA, and polyamides.

[0012] Bicomponent fibers can include any suitable shape, such as core / sheath with a concentric core, core / sheath with an eccentric core, side-by-side with a solid or hollow core, side-by-side with a concentric or eccentric hollow core, split pie with a solid or hollow core, striped fibers, conductive fibers, islands-in-the-sea fibers, mixed fibers, or combinations thereof. In certain embodiments, the bicomponent fibers include about 4 to about 32 split pie pieces, preferably about 8 to about 20 split pie pieces. In one exemplary embodiment, the split pie core is hollow and substantially concentric. The second component may comprise any suitable material having a higher melting point than the first component. Suitable materials for the second component include, but are not limited to, polyolefins, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, PA, and combinations thereof. The weight ratio of the first component to the second component can be about 20 / 80 to about 80 / 20. In certain embodiments, the second component has a greater weight percentage than the first component. In an exemplary embodiment, the first component has a weight percentage of about 50%, about 40%, about 30%, or about 20% of the bicomponent fiber.

[0013] The bicomponent fibers may comprise staple fibers or continuous fibers. The fibers may be bare (i.e., zero spin finished) prior to the filter media manufacturing process. The fibers may comprise a spin finish prior to the filter media manufacturing process. In one exemplary embodiment, the bicomponent fibers are staple fibers having a length of about 40 to about 80 mm, or about 60 mm, with less than about 2% conventional spin finish. Applicants have found that applying a spin finish coating to the fibers reduces the tackiness of the elastomer in the first component. In certain embodiments, the thermoplastic and thermoplastic elastomer materials are selected to have similar or substantially the same melt viscosities to improve fiber spinning.

[0014] In some embodiments, the bicomponent fibers are crimped prior to separation of the first and second components. Applicants have found that crimping the fibers improves separation and, therefore, the overall efficiency of the filter media. In one exemplary embodiment, the fibers are crimped at about 6 crimps / inch to about 30 crimps / inch, preferably about 10 to about 20 crimps / inch. In embodiments, the first and second components are heated to a temperature of about 60° C. to about 200° C., preferably about 110° C. to about 160° C. Applicants have found that this temperature range provides sufficient shrinkage of the first component to achieve separation between the first and second components while minimizing tackiness of the elastomer in the first component.

[0015] In some embodiments, the filter media further comprises one or more second fibers that are thermally indivisible or thermally splittable at a higher temperature than the first bicomponent fibers, i.e., the second fibers comprise a single material or multiple materials having substantially the same melting point, MFR, and / or shrinkage ratio / percentage. Suitable materials for the second fibers include, but are not limited to, HDPE / PET, PP / PET, HDPE / PP, PLA / PLA, PP / PLA, and CoPET / PET bicomponent fibers and PE, PP, PET, PLA, and polyamide monocomponent fibers. The second fibers improve adhesion and increase the "loft" of the filter media. Loft, as used herein, is defined as the volume of voids compared to the volume of all solids. The ratio of first fibers to second fibers in the filter media can be from about 80 / 20 to about 20 / 80. In certain embodiments, the second fibers comprise from about 40% to about 60% or about 50% by weight of the filter media.

[0016] In some embodiments, the second fibers comprise biocomponent fibers such as core / sheath, core / sheath with an eccentric core, side-by-side with a solid or hollow core, side-by-side with a concentric or eccentric hollow core, split pie with a solid or hollow core, striped fibers, conductive fibers, islands-in-the-sea fibers, blended fibers, or combinations thereof. In one exemplary embodiment, the second fibers comprise core / sheath fibers with an eccentric core. Applicants have found that the inclusion of second fibers with an eccentric core reduces the total pressure drop of the filter media. In embodiments, the second fiber has a lower linear mass density than the bicomponent fiber. For example, the splittable bicomponent fiber may have a linear mass density of about 1 denier to about 8 denier, or about 5-6 denier, while the second fiber may have a linear mass density of about 1 to about 8 denier, or about 3 denier. In certain embodiments, the fibers in the filter media may be electrostatically charged, for example, to capture contaminants by both mechanical and electrostatic filtration. The electrostatic or electret substrate may be, for example, a high-loft triboelectrically charged filter media produced by carding and needling.

[0017] In another aspect, a filter is provided that includes the filter medium described above. The filter may further include a substantially rigid support layer adhered to the filter medium. The fibrous substrate may include an extruded film that includes one or more openings through which liquid can flow. For example, the openings may be hexagonal, circular, square, or diamond-shaped. The filter may include pleats. For example, the fibrous substrate may include at least one fold to form a pleat in the substrate. In another example, the filter further includes a plurality of pleats extending across a surface of the fibrous substrate. The fibrous substrate may be unpleated.

[0018] In another aspect, a method for producing a filter medium includes providing one or more bicomponent fibers, each having a first component and a second component, and heating the biocomponent fibers such that at least a portion of the first component separates from the second component. The first component includes a thermoplastic elastomeric material and a thermoplastic material. The thermoplastic elastomeric material is less than about 25% by weight of the first component. In one embodiment, the bicomponent fibers are thermally bonded together at a temperature that allows at least a portion of the first component to be separated from the second component. The biocomponent fibers are heated to a temperature of about 60°C to about 200°C, preferably about 110°C to about 160°C. In embodiments, the first component shrinks by at least about 10% or at least about 60% during heating. The specific amount of shrinkage can be controlled by controlling the amount of thermoplastic elastomer in the first component. Increasing the ratio of thermoplastic elastomer material to thermoplastic material in the first component increases the amount of shrinkage of the first component. In another embodiment, the amount of shrinkage of the first component is controlled via the amount of stretch during fiber spinning. Specifically, increasing the amount of stretch stretches the physical bonds of the elastomeric resin, allowing for more shrinkage upon heating.

[0019] The fibers of the substrate can be made by any suitable method, including, but not limited to, meltblown, bicomponent meltblown, spunbond or spunlace, bicomponent spunbond, thermally bonded, carded, air-through-bonded carded, airlaid, wetlaid, extrusion, co-molded, needlepunched, stitched, hydroentangled, etc. In certain embodiments, bare continuous fibers are formed via a process selected from the group consisting of spunbond and meltblown. In other embodiments, staple fibers incorporating the filtration media are formed via carding, airlaid, wetlaid, or similar processes. In one such embodiment, the bicomponent fiber is carded. The method further includes crimping the bicomponent fiber prior to the carding step. The crimp number of the biocomponent fiber is from about 6 to about 30 crimps per inch, preferably from about 10 to about 20 crimps per inch.

[0020] In embodiments, the method further includes blending the first fiber with one or more second fibers. The second fibers can be formed from a single component or two or more components that remain substantially adhered to each other during heating. In embodiments, the second fibers include bicomponent fibers having at least two components that remain substantially adhered to each other during heating. In embodiments, the first and / or second components include a slip additive selected to reduce the interfacial energy between the first and second components, thereby increasing the amount of partitioning that occurs between these components during the heating and bonding process. The enumeration herein of desirable objects met by various embodiments herein is not meant to imply or suggest that any of these objects, individually or collectively, are present as essential features of the most general embodiment herein or its more specific embodiments. [Brief explanation of the drawings]

[0021] [Figure 1A] FIG. 1 is a cross-sectional view of a bicomponent fiber of a filter medium. [Figure 1B] FIG. 1B is an enlarged view of the first component of the bicomponent fiber of FIG. 1A. [Figure 2] FIG. 1 is a cross-sectional view of a bicomponent fiber after fiber spinning. [Figure 3] FIG. 1 is a cross-sectional view of a bicomponent fiber after carding. [Figure 4] FIG. 1 is a cross-sectional view of a bicomponent fiber after thermal bonding. [Figure 5A] FIG. 1 is a schematic representation of multiple biocomponent fibers after extrusion. [Figure 5B] FIG. 1 is a schematic diagram of a biocomponent fiber after cutting and crimping. [Figure 5C] FIG. 1 is a schematic diagram of biocomponent fibers after carding. [Figure 5D] FIG. 1 is a schematic diagram of the biocomponent fiber after thermal bonding. [Figure 6]1 is an optical microscope image of a cross section of a biocomponent fiber described herein. [Figure 7] 1 depicts a series of optical microscope images of fibers described herein after carding and bonding. DETAILED DESCRIPTION OF THE INVENTION

[0022] This specification and the accompanying drawings depict exemplary embodiments and should not be construed as limiting, with the claims defining the scope of this specification, including equivalents. Various mechanical, compositional, structural, and operational changes can be made without departing from the scope of this specification and claims, including equivalents. In some instances, well-known structures and techniques have not been shown or described in detail to avoid obscuring the description. Like numbers in two or more figures represent the same or similar elements. Furthermore, elements and their related aspects described in detail with respect to one embodiment may, whenever possible, be included in other embodiments where they are not specifically shown or described. For example, if an element is described in detail with respect to one embodiment but not with respect to a second embodiment, the element can still be claimed to be included in the second embodiment. Furthermore, the depictions herein are for illustrative purposes and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated components.

[0023] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," as well as the use of the singular form of any word, include plural referents unless expressly and unambiguously limited to one referent. As used herein, the term "include" and its grammatical variations are intended to be open-ended, and the enumeration of items in a list does not exclude other similar items that may be substituted for or added to the listed items. Unless otherwise indicated, all quantitative values ​​are approximate, whether preceded by words such as "about" or "approximately." The materials, methods, and examples described herein are illustrative only and are not intended to be limiting.

[0024] Filter media and filters are provided, such as gas or liquid filters, face masks, CPAP filters, vacuum bags, cabin air filters, HVAC furnace filters, residential air filters, commercial air filters, gas turbine and compressor intake filters, and panel filters. The filter media and filters described herein comprise thermally splittable bicomponent fibers to reduce the fiber size of at least some of the components of the fibers within the filter media. This fiber size reduction increases the specific surface area, thereby improving the overall efficiency of such filters in capturing contaminants, particularly those in the size range of about 0.1 to about 1 micron (i.e., E1 particles), without compromising other important filter properties such as pressure drop and breathability. Each bicomponent fiber has at least a first component and a second component. In certain embodiments, at least a portion of the first component is separated from the second component during carding and / or thermal bonding. The separated first component is substantially smaller in size than the bicomponent fiber. In some embodiments, the size of the bicomponent fiber is about 1.5 to about 18 dtex, or about 1.5 to about 5.6 dtex. The term dtex, as used herein, refers to the mass in grams per 10,000 meters of fiber. The first component may be separated or split from the second component to produce substantially smaller fibers or filaments or segments. After separation or splitting, for example, at least a portion of the first component may have a size of less than about 1.5 dtex, or about 0.005 to about 0.05 dtex, or about 0.01 to about 0.02 dtex. The largest dimension of the first component may be about 1 to 10 microns, or about 3 to 5 microns.

[0025] Bicomponent fibers may include any suitable shape, such as core / sheath with a concentric core, core / sheath with an eccentric core, side-by-side with a solid or hollow core, side-by-side with a concentric or eccentric hollow core, split pie with a solid or hollow core, striped fibers, conductive fibers, islands-in-the-sea fibers, blended fibers, or combinations thereof. In one exemplary embodiment, the bicomponent fiber comprises about 4 to about 32 pieces, preferably about 8 to about 20 pieces, of the split pie. In one exemplary embodiment, the core of the split pie is hollow and substantially concentric.

[0026] The first component comprises a thermoplastic elastomeric material and a thermoplastic material and has a higher shrinkage ratio / percentage / rate than the second component such that application of heat or thermal energy to the fibers causes at least a portion of the first component to separate from the second component. In some embodiments, the melting point of the first component is about 50°C lower than the melting point of the second component. The MFRs of the first and second components are preferably the same. In some embodiments, the MFRs of these components are about 10 to 50 g / 10 min. In embodiments, the thermoplastic elastomer material of the first component is less than about 25% by weight of the first component, or about 10 to about 20% by weight of the first component, preferably about 15% by weight.

[0027] Suitable thermoplastic elastomer materials for the first component include styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymers, polyester elastomers (e.g., Hytrel®), thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof. In a preferred embodiment, the thermoplastic elastomer material comprises an olefin block copolymer, such as Vistamaxx™ 7020BF (propylene ethylene copolymer), manufactured by Exxon. Regarding the selection of polymer blends, miscible resins are blended with comparable materials. For example, PP can be mixed with olefin block copolymer elastomers, polyamide elastomers can be blended with polyamide resins, and polyester elastomer resins can be blended with PET or PBT. In other embodiments, any elastomer can be blended with any thermoplastic polymer resin, as long as it is miscible. For example, PLA can be blended with an olefin block copolymer to further increase shrinkage.

[0028] Suitable thermoplastic materials for the first component include polyolefins, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, PA, CoPET, and combinations thereof. In a preferred embodiment, the thermoplastic material comprises PP. The second component may comprise any suitable material having a higher melting point and / or a comparable melt flow rate (MFR) than the first component. Suitable materials for the second component include, but are not limited to, polyolefins, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, polyamide, and combinations thereof. The weight ratio of the first component to the second component can be about 20 / 80 to about 80 / 20. In certain embodiments, the second component has a greater weight percentage than the first component. In an exemplary embodiment, the first component has a weight percentage of about 50%, about 40%, about 30%, or about 20% of the bicomponent fiber.

[0029] The fibers may be staple or continuous. The fibers may be bare (e.g., zero spin finished) or may include a spin finish. The spin finish may include, but is not limited to, lubricants, emulsifiers, termite repellents, antimicrobial agents, flocculants, and wetting agents. Other organic liquids, such as alcohols or blends of organic liquids, may also be added to the spin finish. The spin finish may be applied, for example, during fiber carding, during melt spinning operations, or during fiber drawing, crimping, and cutting operations. In one exemplary embodiment, the bicomponent fibers are staple fibers having a conventional spin finish of less than about 2% and a length of about 40 to about 80 mm, or about 60 mm. In certain embodiments, the thermoplastic material and the thermoplastic elastomeric material are selected to have substantially the same melt viscosity.

[0030] In embodiments, the bicomponent fibers are crimped prior to separation of the first and second components. In one exemplary embodiment, the fibers are crimped at about 8 crimps / inch to about 30 crimps / inch, preferably about 14 to about 20 crimps / inch. In embodiments, the first and second components are heated to a temperature of about 60°C to about 200°C, preferably about 110°C to about 160°C, and more preferably about 130°C to about 160°C.

[0031] In some embodiments, the filter media further comprises one or more second fibers that are thermally indivisible, i.e., the second fibers comprise a single material or multiple materials having substantially the same melting point, MFR, and / or shrinkage ratio / percentage. In other embodiments, the second fibers are thermally splittable at a higher temperature than the first fibers. In these embodiments, the first and second fibers are thermally bonded at a temperature that allows for thermal splitting of the first fibers without substantial thermal splitting of the second fibers. The second fibers improve the bond and increase the "loft" of the filter media. Loft, as used herein, is defined as the volume of voids compared to the volume of total solids. The ratio of first fibers to second fibers in the filter media can be from about 80 / 20 to about 20 / 80. In certain embodiments, the second fibers comprise from about 40% to about 60% by weight, or about 50% by weight, of the filter media. In embodiments, the second fibers comprise biocomponent fibers such as core / sheath, core / sheath with an eccentric core, side-by-side with a solid or hollow core, side-by-side with a concentric or eccentric hollow core, split pie with a solid or hollow core, striped fibers, conductive fibers, islands-in-the-sea fibers, blended fibers, or combinations thereof. In one exemplary embodiment, the second fibers comprise core / sheath fibers with an eccentric core. Applicants have found that the inclusion of a second sheath / core fiber with an eccentric core reduces the total pressure drop of the filter media.

[0032] The fibers may have a thickness appropriate for the application. In some embodiments, the fibers have at least one dimension ranging from about 1 to about 10,000 micrometers, or from about 1 to about 1,000 micrometers, or from about 10 to 100 micrometers. The thickness of the fibers may be measured in denier, which is a measure of the linear mass density of the fiber. In some embodiments, the fibers may have a linear density of about 1 denier to about 10 denier. The fibers may be configured as a gradient density media, in which the pore size decreases from the upper surface (upstream) to the lower surface (downstream) of the filter, or vice versa, to improve capture efficiency and dust retention capacity. In certain embodiments, the second fiber has a wide range of linear mass densities. For example, the first bicomponent fiber may have a linear mass density of about 1 denier to about 18 denier, or about 3-6 denier, and the second fiber may have a linear mass density of about 1 to about 18 denier, or about 3-6 denier. In certain embodiments, the filter media may include at least two different fiber thicknesses or linear densities to provide at least two different layers of filter within the same filter media. In certain embodiments, the filter media may include three or more separate sections or layers with different denier fiber ranges within each section.

[0033] Referring now to Figure 1, one embodiment of a bicomponent fiber 10 will be described. As shown, fiber 10 is a split-pie bicomponent fiber having a first component 20 and a second component 30. The second component 30 is formed as an annular filament surrounding a hollow central portion 40. The first component 20 preferably includes a plurality of filaments extending into the annular second component 30. While fiber 10 is shown as having eight first component filaments forming a 16-piece pie, it will be understood that bicomponent fiber 10 may include a split pie having from about 4 to about 32 pieces, preferably from about 8 to about 20 pieces. Each filament of the first component 20 may have any suitable cross-sectional shape, such as circular, oval, rectangular, square, triangular, etc. In one embodiment, the filaments have a substantially pie-slice cross-sectional shape, as shown in FIG. 2. Dimensions of such filaments may include a diameter along the major axis of about 0.1 microns to about 10 microns, or about 3 microns to about 5 microns, preferably about 4 microns. The diameter along the minor axis may be about 1 micron to about 10 microns, or about 2 microns to about 4 microns, preferably about 3 microns. The total size of the filaments of the first component is about 0.1 to 1.1 dtex.

[0034] In certain embodiments, the bicomponent fibers discussed herein may be included as part of a filter device that captures or absorbs contaminants, such as a liquid filter, a gas filter for home and commercial air filtration (e.g., HVAC), a surgical mask, or other face covering. The filter device may be a mechanical filter, an absorption filter, a sequestration filter, an ion exchange filter, a reverse osmosis filter, a surface filter, a depth filter, or the like, and can be designed to remove many different types of contaminants from air, water, or otherwise. In one such embodiment, the fibers are incorporated into air filters that remove particles and contaminants from the air, such as HEPA filters (i.e., pleated mechanical air filters), UV light filters, electrostatic filters, washable filters, media filters, spun glass filters, pleated or non-pleated air filters, activated carbon filters, pocket filters, V-bank compact filters, filter sheets, flat cell filters, filter cartridges, etc. Filter media for air filters may include such splittable fibers and may be supported by a support layer or scrim layer or may be included in other layers or materials.

[0035] Traditional residential and commercial air filters, such as HEPA filters or pleated filters, are typically rated by their ability to filter particles between approximately 0.3 and 10 microns. This rating, called the Minimum Efficiency Reporting Value, or MERV, was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). MERV ratings range from 1 to 16, with higher numbers indicating greater efficiency in capturing a particular type of particle. It is also common to compare efficiency values ​​by particle size within the airstream under test. Values ​​of E3, E2, and E1 indicate particle efficiency at 3-10 microns, 1-3 microns, and 0.3-1 microns, respectively. The predicted MERV ratings of the filter media discussed herein vary based on many factors, including the type and size of fibers used in the filter media, the width of the filter media, the number and size of pleats (if present), face velocity, etc. Similarly, the pressure drop of the filter media also varies based on many factors, including those mentioned above.

[0036] In certain embodiments, the substrate is a filter media for a gas filter, such as an HVAC filter. In these embodiments, the thermally splittable fibers increase the filter media's efficiency in capturing contaminants in the E1, E2, and E3 particle sizes by about 5 to 30 points, or by about 10% to about 50%. In these embodiments, the MERV rating of the filter media can be increased simply by providing the thermally splittable fibers. The MERV rating can increase from MERV 6 to MERV 10. The pressure drop through the filter remains substantially the same. Thus, the thermally splittable fibers increase the efficiency of the filter media without compromising pressure drop. In certain embodiments, the filter media comprises nonwoven materials, including substrates, sheets, layers, films, apertured films, meshes, or other media containing fibers. The nonwoven substrates discussed herein may comprise structures of individual fibers or threads that are overlapped, interlocked, or bonded to one another. Nonwovens may include sheet or web structures bonded together by mechanically, thermally, or chemically entangling fibers or filaments (and by perforating films). They may also be substantially flat, porous sheets made directly from separate fibers or molten plastic or plastic films. Examples of suitable nonwoven materials include, but are not limited to, fibers, layers, or webs that are meltblown, spunbonded or spunlaced, heat-bonded, bonded-carded, airlaid, wetlaid, co-molded, needle-punched, stitched, hydroentangled, etc.

[0037] In some embodiments, nonwoven fabrics can be used, for example, as mesh filter press cloths, nonwoven filter pads and other die cut pieces, centrifuge filter bags, liquid filter bags, dust collector bags, bed dryer bags, rotary drum filters, filter belts, leaf filters, furnace filters, roll media, and the like. Contemplated fibers can have many cross-sectional shapes, including, but not limited to, round, kidney bean, dogbone, trilobal, barbell, bowtie, star, Y-shaped, and others. These and / or other conventional shapes can be used with embodiments to achieve desired performance characteristics. The fibers in the filter media remain connected to one another through thermal and chemical bonding, by intertwining with one another, and by the use of a binder, such as an adhesive.

[0038] The bicomponent fibers in the filter media can remain connected to other fibers, such as the second thermally indivisible fibers described above, by thermal bonding, chemical bonding, or intertwining. In some embodiments, the substrate can comprise a "high loft" nonwoven material, including spunbond or air-through bonded carded nonwoven fibers. In air-through bonded carded nonwoven fibers, the loft of the substrate can be controlled by various means known to those skilled in the art. For example, loft can be increased by reducing the compressive force on the filter media during bonding. In another example, high loft nonwoven materials can be produced using thicker fibers, such as fibers greater than 3 denier, e.g., 5 denier or greater, 6 denier or greater (discussed in more detail below). In other embodiments, loft can be increased by using eccentric biocomponent fibers. In other embodiments, loft can be increased by using non-bonded fibers. In certain embodiments, the fibers may be electrostatically charged, for example, so that contaminants are captured by both mechanical and electrostatic filtration. The substrate can be electrostatically charged using tribocharging, corona discharge, electrostatic fiber spinning, hydrocharging, a charging bar, or other known methods. Corona charging is suitable for charging polymer fibers or fiber blends, or woven fabrics. Tribocharging is suitable for charging fibers of different electronegativity. Electrostatic or electret filter media can be high-loft tribocharged filter media produced by carding and needling. Electrostatic fiber spinning combines polymer charging and fiber spinning in a single process. Suitable methods for tribocharging are described in U.S. Pat. No. 9,074,301 and commonly assigned provisional patent application Ser. No. 63 / 410,729, filed Sep. 28, 2022, the entire disclosures of which are incorporated herein by reference. The filter media may include charging additives to modify the triboelectric charging of the fibers and increase the stability and / or duration of triboelectric charging within the filter. This increases the overall filtration efficiency of the filter without compromising other important filter properties, such as filter life, dust holding capacity, pressure drop, or airflow. Suitable charging additives for triboelectric charging are described in commonly assigned Provisional Patent Application No. 63 / 410,731, filed September 28, 2022, the entire disclosure of which is incorporated herein by reference for all purposes.

[0039] In certain embodiments, the fibers may include a silicone-based coating to improve the filter media's efficiency in capturing contaminants, particularly those in the E2 and E3 particle size ranges. The silicone-based coating may include a reactive silicone macroemulsion. The silicone emulsion may include, for example, a dimethyl silicone emulsion, an amino-type silicone emulsion, an organofunctional silicone emulsion, a resin-type silicone emulsion, a film-forming silicone emulsion, and the like. In one embodiment, the reactive silicone macroemulsion includes an amino-functional polydimethylsiloxane and / or polyethylene glycol monotridecyl ether. Suitable silicone coatings are described in commonly assigned U.S. Provisional Patent Application No. 63 / 406,686, filed September 14, 2022, the entire disclosure of which is incorporated herein by reference for all purposes. In some embodiments, the filter media may be scored, pleated, or folded into a pleated filter. The pleats may be formed by various conventional pleating processes, including, but not limited to, bar pleating, rotary pleating, and star gear pleating. The filter includes one or more support layers adhered to the filter media. In some embodiments, a polymer layer, membrane, or film is provided that includes one or more openings for gas or liquid flow therethrough. In other embodiments, the material includes a flexible surface layer for finger bandage pads, face masks, and the like.

[0040] In certain embodiments, the fibers may be contained in or adhered to a thin film or layer containing apertures, holes, or perforations. Apertures can be embossed with shapes (circles, diamonds, hexagons, ellipses, triangles, rectangles, etc.) and then stretched until apertures form in the thinned areas created by the embossing. Such apertured substrates can be formed from many polymers, such as polypropylene, polyethylene, and high-density polyethylene ("HDPE"). The polymer layer may include, for example, an extruded film. Apertured films are commercially available and are sold under the trademark Delnet®. The substrate is provided in a roll, and the nanofibers are deposited onto the substrate in a roll-to-roll process. Contemplated fibers can be made and / or processed by any method including, but not limited to, airlaid or drylaid processes, carding, spinneret, gel spinning, melt spinning, wet spinning, dry spinning, islands-in-the-sea staple or spunbond, split-pie staple or spunbond, and others. Such methods are described in U.S. Patent Nos. 4,406,950, 6,338,814, 6,616,435, 6,861,142, 7,252,493, 7,300,272, 7,309,430, 7,422,071, 7,431,869, 7,504,348, 7,774,077, 9,522,357, 9,993,761, and U.S. Patent Publication No. 2009 / 266,759, the entire disclosures of which are incorporated herein by reference for all purposes.

[0041] In one exemplary embodiment, the filter media is manufactured by forming bicomponent fibers from the first and second components described above. The fiber strands are melted and then extruded or drawn through the spinneret holes of an extruder to form bicomponent shapes, such as split pie, side-by-side, etc. Figure 2 shows a representative bicomponent fiber 10 after fiber spinning, illustrating the first and second components 20, 30. Figure 5A shows a plurality of fibers 50 after extrusion. In one exemplary embodiment, staple fibers are carded. The system may include one carding machine or two carding machines arranged in series with one another. Short fiber lengths (40-80 mm) are processed into a continuous fibrous web through opening, blending, and consolidation. Figure 3 shows a representative fiber 10 after carding, demonstrating slight separation of the first and second components 20, 30. Figure 5C shows multiple fibers 50 after carding, demonstrating that some of the first component 20 has begun to separate from the fiber 50 to form substantially smaller diameter threads or fibers.

[0042] Once the fibrous web is formed by carding, a secondary bonding step can be used to provide integrity and strength to the fibrous web. This bonding step can be accomplished by chemical, thermal, or mechanical methods. In one embodiment, the fibers are thermally bonded with heat, resulting in at least a portion of the first component separating from the second component 20, 30 (see FIGS. 4 and 5D). In an exemplary embodiment, the fibers are heated and bonded in an air-through oven at a temperature of less than about 200° C., preferably about 110-180° C., or about 150° C. In embodiments, the first component shrinks by at least about 10% or at least about 40% during heating.

[0043] In certain embodiments, the fibers are coated with a spin finish and crimped before, during, or after the melt spinning process. Figure 5B shows a plurality of fibers that have been cut and crimped before the carding process. In some embodiments, the first and / or second components of the heat-splittable fiber include a slip additive for easier splitting during heat activation, selected from those including, but not limited to, waxes, low surface energy additives, ceramics, lubricants, and the like.

[0044] In another embodiment, the bare continuous fibers are formed by a process selected from the group consisting of spunbonding and meltblown. In one example, the system may include a spunbonding line, in which molten polymer is spun and the molten filaments are drawn to form filaments. The filament fiber bundles are separated, spread, and then layered on a net to form a web. The fibers are bonded in the form of a sheet by thermal bonding and embossing. The thermoplastic filaments are then split during a heat treatment. In yet another example, the fibers can be formed using a meltblowing die. Examples of suitable meltblown dies that can be used to produce nonwoven materials are described in detail in U.S. Patent Nos. 6,972,104, 8,017,534, and 7,772,456, as well as U.S. Patent Application No. US20200216979A1, the entire disclosures of which are incorporated herein by reference in their entirety for all purposes. [Example]

[0045] Applicant has conducted numerous tests on thermally splittable fibers for use in filter media. In these tests, Applicant has discovered a number of important features of the fibers and methods for manufacturing the fibers that produce significant improvements in the filtration efficiency of filter media containing these fibers.

[0046] First test In a first test, Applicant tested the filtration efficiency of bicomponent filaments or fibers with a hollow center, segmented cross section (16 pi), a mass linear density of 3 denier, and a fiber length of 60 mm. The first component contained a 75:25 mass blend of PP resin and an elastomeric material manufactured by Exxon Corporation under the trademark Vistamaxx™ 7020BF. The second component contained 100% PET for the first sample and 97% PET with 3% slip additive for the second sample. The first component comprised 60% by volume of the fibers, and the second component comprised 40% by volume. The fibers were hand-cut without crimping. Applicant then produced a filter medium containing two different fibers: (1) a 3-denier bicomponent fiber containing thermally indivisible material; and (2) the bicomponent fiber described above. The ratio of the two fibers was 80% indivisible fiber and 20% splittable fiber. Applicant then compared the test results of this filter medium with a standard filter medium containing 100% indivisible 3-denier fiber. The test results are summarized in Table 1 below. [Table 1]

[0047] As shown in Table 1, the splittable fibers reduced pressure drop but did not substantially improve the filtration efficiency of the filter media compared to 100% 3D non-splittable fibers in zones E2 and E3. Applicant believes this occurred for at least one of five reasons: (1) the bicomponent fibers were not crimped; (2) the weight percent of elastomer in the first component was too high, causing the elastomer to adhere to the second component during stretching; (3) the fibers were heated to too high a temperature, which also caused the elastomeric material to adhere to the other splittable fibers; (4) the ratio of thermally non-splittable fibers to splittable fibers (i.e., 80 / 20) was too high; and / or (5) the basis weight of the web using the splittable fibers was lower than the control sample. Applicant also conducted tests of different temperature profiles to determine the optimum temperature for shrinking the splittable fiber. The fibers used in this test were substantially the same as those described above in the first test. This test demonstrated that the first component in the fiber began to shrink significantly around 65-70°C. Furthermore, the elastomeric polymer chips began to soften and stick together around 100°C.

[0048] Applicant then conducted a second test of the filtration efficiency of a filter medium containing bicomponent filaments or fibers with a hollow split-pie cross section (16 pi), a mass linear density of 3 denier, and a fiber length of 60 mm. The first component contained a 75:25 mass blend of PP resin and an elastomeric material manufactured by Exxon Corporation under the trademark Vistamaxx™ 7020BF. The second component contained 100% PET for the first sample and 97% PET with 3% slip additive for the second sample. The first component comprised 60% of the fibers, and the second component comprised 40%. The fibers were crimped at 12 crimps per inch. The fibers were heated to a temperature of 150°C for approximately 20 seconds. Applicant then produced a filter medium containing two different fibers: (1) a 3-denier bicomponent fiber containing thermally indivisible material; and (2) the bicomponent fiber described above. The ratio of the two fibers was 70% indivisible fiber and 30% splittable fiber. Applicant then compared the test results of this filter medium with a standard filter medium containing 100% indivisible 3-denier fiber. The test results are summarized in Table 2 below. [Table 2]

[0049] As shown, the 30% splittable sample demonstrated increased filtration of E2 and E3 particle groups. This increased the media's overall MERV rating from MERV 7 to MERV 9. However, the pressure drop of the media using the sample fiber increased slightly from 0.1598 to 0.1664 in. H2O at 500 CFM / 180 FPM. Applicant conducted another test to evaluate the filtration efficiency of a bicomponent filament or fiber having a hollow center, segmented cross section (16 pi), a mass linear density of 5.6 denier, and a fiber length of 60 mm. The first component comprised an 85:15 blend by weight of PP resin and an elastomeric material manufactured by Exxon Corporation under the trademark Vistamaxx™ 7020BF. The second component comprised 100% PLA. In the first run, the first component comprised 40% of the total fiber cross-sectional volume, and the second component comprised 60%. In the second run, the ratio of the first component to the second component was 50 / 50. The fibers were crimped at 10-20 crimps per inch. The fibers were heated to a temperature of 150°C for approximately 20 seconds.

[0050] Applicant determined that using larger bicomponent fibers (i.e., 5.6 denier filaments) reduced the amount of filament breakage during drawing. Additionally, Applicant found that lower godet temperatures significantly reduced filament sticking. In fact, of the 288 individual filaments produced, none stuck to each other during the manufacturing process. Next, Applicant conducted numerous carding tests using the bicomponent fibers described above to manufacture filter media. The filter media included two different fibers: (1) 3-denier bicomponent fibers containing thermally unsplittable material; and (2) the bicomponent fibers described above. In the first carding test, the 3D fibers included a G8 finish, a special filter finish that enhances filtration efficiency. As shown in Table 3 below, Applicant tested the filtration efficiency of three different filter media: (1) Sample 1 (designated P-S1): 100% thermally unsplittable 3D fibers with a G8 finish; (2) Sample 2 (designated P-S2): 70% thermally unsplittable 3D fibers with a G8 finish and 30% 5.6D 60 / 40 splittable fibers; and (3) Sample 3 (designated P-S3): 70% thermally unsplittable 3D fibers with a G8 finish and 30% 5.6D 50 / 50 splittable fibers. Again, 60 / 40 and 50 / 50 correspond to the volume ratios of the first and second components in the heat splittable fiber. The first data set shows the actual flat sheet results. * The second data set, marked with a, shows the results for flat sheets normalized to 120 gsm. [Table 3]

[0051] These results show that using 50 / 50 splittable fiber (Sample 3) resulted in lower PD (pressure drop) at comparable efficiency compared to the 60 / 40 splittable fiber blend and Sample 1. Applicant conducted a second test of the filtration efficiency of five different filter media combinations, as shown in Table 4 below. Note that G6 and G8 correspond to standard spin finish (G6) and enhanced filtration efficiency spin finish (G8), respectively. (1) Sample 1 (designated S1): 100% thermally unsplittable 3D bicomponent fibers with a G6 spin finish and a thickness of 83 mils; (2) Sample 2 (designated S2): 70% thermally unsplittable 3D bicomponent fibers with a G6 spin finish and a thickness of 30% 5.6D 60 / 40 splittable fibers; and (3) Sample 3 (designated S3): 70% thermally unsplittable 3D bicomponent fibers with a G6 spin finish and a thickness of 30% 5.6D 50 / 50 splittable fibers. Sample 4 (designated S4) was 60% non-splittable 3D bicomponent fiber with a concentric core / sheath with a G6 finish and 40% 5.6D 50 / 50 splittable fiber (60 mil thick). Sample 5 (designated S5) was 60% non-splittable 3D bicomponent fiber with an eccentric core / sheath and 3D bicomponent green fiber with a G8 finish. [Table 4]

[0052] As shown, the two samples with thermally splittable fibers (Samples 2 and 3) had increased efficiency, especially in E3, with essentially the same pressure drop. As shown, the eccentric core / sheath of Sample 5 reduced the total pressure drop of the filter media. Additionally, the G8 spin finish substantially increased the media's efficiency in capturing E3 particle size contaminants compared to the other samples.

[0053] In a preferred embodiment, Applicant produced a 16-segment pie. The first component was PLA and the second component was a blend of PP (85%) and Vistamaxx (15%). Figure 6 is an optical microscope image of the cross section of the fiber. Figure 7 shows a series of optical images of the web surface after carding and bonding. The curling of each piece is due to splitting and shrinkage. In another embodiment, heat-splittable bicomponent fibers can be produced by bicomponent spunbond technology, where the fine threads are continuous. In another embodiment, the filter may also include nanoparticles incorporated into the substrate or filter media. As used herein, the term "nanoparticle" refers to any particle having a dimension of less than 1 micron in at least one axis or dimension. For example, a fiber having a diameter or width of less than a micrometer and a length greater than 1 micrometer is a nanoparticle as used herein. Nanofibers may have a continuous length, or they may have discrete lengths, such as 1 to 100,000 microns, preferably about 100 to 10,000 microns.

[0054] In certain embodiments, the nanoparticles are "depth-dispersed" within the substrate. As used herein, the term "depth-dispersed" means that the nanoparticles are dispersed beyond a first surface of the substrate such that at least a portion of the nanoparticles are disposed between first and second opposing surfaces of the interior structure of the substrate or medium. In certain embodiments, the nanoparticles are dispersed substantially throughout the medium, from the first surface to the opposing second surface. In other embodiments, the nanoparticles are dispersed in a portion of the medium, from the first surface to a location between the first and second surfaces. The nanoparticles can be selected to have different triboelectric properties relative to the first or second fibers to enhance particle removal using the triboelectric effect. In this manner, the nanoparticles formed are formed in an electric field and are less susceptible to chemical contamination that can mitigate the triboelectric effect. Nanoparticles with different adsorption or surface charge properties than the coarse fibers can also be used, for example, in oil or water filtration. This difference in properties can be used to enhance or create a local electric field gradient within the filter media to enhance particle removal. The nanoparticles and the coarse fibers can have different wetting properties. The nanoparticles may comprise any suitable material, such as glass, biosoluble glass, ceramic materials, acrylic, carbon, metals such as alumina, polymers (such as nylon, polyethylene terephthalate, etc.), polyvinyl chloride (PVC), polyolefins, polyacetals, polyesters, cellulose ethers, polyalkylene sulfides, poly(arylene oxides), polysulfones, modified polysulfone polymers and polyvinyl alcohols, polyamides, polystyrenes, polyacrylonitriles, polyvinylidene chloride, polymethyl methacrylate, polyvinylidene fluoride, and any combination thereof.

[0055] In some embodiments, the nanoparticles are bonded to the fibers through mechanical entanglement. This mechanical bond can be supplemented with adhesives or binders. In certain embodiments, the nanoparticles are uncrimped (i.e., do not contain significant wavy, bent, curled, coiled sawtooth, or similar shapes associated with nanoparticles in their relaxed state). In other embodiments, the nanoparticles may have a crimped structure with discrete lengths. For example, when crimped nanofibers with such discrete lengths are attached to a fiber, the nanofibers entangle with each other and with, on, or around the fiber with strong bonds to form the modified fiber. In other embodiments, the bonding of the nanofibers to the microfibers is achieved through electrostatic charge attraction and / or van der Waals force attraction between the fiber and the nanoparticles. A more complete description of filter media incorporating nanoparticles can be found in commonly assigned, co-pending U.S. Provisional Patent Applications Nos. 63 / 328,970, 63 / 328,959, 63 / 328,983, 63 / 328,998, 63 / 329,009, 63 / 329,018, 63 / 329,137, 63 / 329,146, 63 / 329,155, 63 / 329,158, 63 / 329,161, and 63 / 329,162, filed April 8, 2022, the entire disclosures of which are incorporated herein by reference in their entirety for all purposes.

[0056] In other embodiments, absorbent pads and dressings for application to wounds are provided that include one or more of the bicomponent fibers described herein. These biocomponent fibers increase the surface area of ​​the absorbent pad, thereby increasing its liquid absorbency. The absorbent pads and bandages can be used to treat any type of break or opening in epithelial tissue, such as skin. For example, the wound can be an abrasion, scrape, scab, blister, burn, incision, laceration, puncture, or abrasion, and the absorbent material can be applied to the wound bed or healing closed tissue. The absorbent material of the present disclosure can also be used on sores, ulcers, and infected skin. Typical fluids that drain from a wound and enter one or more layers of the absorbent pad include blood and its components, sweat, serous fluid, pus, etc. The material can be used on wounds of any size, shape, or depth, and in clinical settings, etc.

[0057] In one such embodiment, the bandage or wound dressing includes an adhesive layer and an absorbent pad. Additional layers, such as a backing layer, may also be layers of the bandage. In certain embodiments, a wound release layer may be added to the surface of the absorbent pad that contacts the wound. It is understood that other types of backing or release layers may be added, and layers associated with easily removing the pad or bandage from its packaging may be included. Alternatively, a release layer, such as a silicone paper release strip (not shown), may be present on the surface of the adhesive layer, which can be removed by the user before placing the bandage on the skin. A more complete description of bandages or wound dressings suitable for use with the biocomponent fibers described herein can be found in commonly assigned, co-pending U.S. Patent Application No. 16 / 989,209, filed February 21, 2021, the entire disclosure of which is incorporated herein by reference. In one embodiment, the absorbent pad includes a first polymer layer and a second layer thermally bonded to the first layer and including at least one thermally bondable fiber. In embodiments, the thermally bondable fiber includes a biocomponent fiber, as described above. The biocomponent fiber may include any suitable configuration, such as core / sheath with concentric or eccentric cores, side-by-side, split-pie, islands-in-the-sea, hollow bicomponent fiber, hollow split-pie, trilobal bicomponent fiber, mixed fiber, striped fiber, conductive fiber, etc. The bicomponent fiber may have a solid core or a hollow core.

[0058] In embodiments, the bicomponent fiber comprises a first component and a second component. The first component comprises a thermoplastic elastomeric material and a thermoplastic material and has a higher shrinkage percentage than the second component such that upon application of heat or thermal energy to the fiber, at least a portion of the first component separates from the second component. Suitable materials for the first and second components are described above. In embodiments, the thermoplastic elastomeric material of the first component is less than about 25% by weight of the first component, or about 10 to about 20%, preferably about 15%, by weight of the first component. The weight ratio of the first component to the second component can be about 20 / 80 to about 80 / 20. In certain embodiments, the second component has a greater weight percentage than the first component. In an exemplary embodiment, the first component has a weight percentage of about 50%, about 40%, about 30%, or about 20% of the bicomponent fiber. The bicomponent fibers may include staple fibers or continuous fibers. The fibers may be bare (i.e., zero spin finished) prior to the filter media manufacturing process. The fibers may include a spin finish prior to the filter media manufacturing process.

[0059] While the devices, systems, and methods have been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and variations therein may be made by those skilled in the art. Accordingly, the foregoing description should not be construed as limited thereby, but should be construed as including such obvious variations as may be set forth above, and should be construed as limited only by the spirit and scope of the following claims.

[0060] For example, in a first aspect, a first embodiment is a filter medium comprising bicomponent fibers including a first component and a second component. The first component has a lower melting point than the second component. The first component comprises a thermoplastic elastomer material and a thermoplastic material. The thermoplastic elastomer material accounts for less than about 25% by weight of the first component. A second embodiment is the first embodiment, where the first component has a higher shrinkage ratio or percentage or rate than the second component. A third embodiment is any combination of the first two embodiments, wherein the thermoplastic elastomer material is about 10 to about 20% by weight of the first component. A fourth embodiment is a combination of any of the first three embodiments, wherein the thermoplastic elastomer material is about 15% by weight of the first component. A fifth embodiment is a combination of any of the first four embodiments, wherein the first component has substantially the same melt viscosity as the second component.

[0061] A sixth embodiment is any combination of the first five embodiments, wherein the thermoplastic material of the first component comprises a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, CoPET, nylon, PLA, and combinations thereof. A seventh embodiment is any combination of the first six embodiments, wherein the thermoplastic elastomeric material comprises a material selected from the group consisting of styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymer elastomers, thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof. An eighth embodiment is any combination of the first seven embodiments, wherein the bicomponent fiber comprises a split pie. A ninth embodiment is any combination of the first eight embodiments in which the divided pies are concentric. A tenth embodiment is any combination of the first nine embodiments, where the divided pie is eccentric.

[0062] An eleventh embodiment is any combination of the first ten embodiments, wherein the biocomponent fiber has a hollow center portion. A twelfth embodiment is any combination of the first eleven embodiments, with concentric hollow centers. A thirteenth embodiment is any combination of the first twelve embodiments, where the hollow center is eccentric. A fourteenth embodiment is any combination of the first thirteen embodiments, wherein the bicomponent fibers comprise discontinuous staple fibers.

[0063] A fifteenth embodiment is any combination of the first fourteen embodiments, wherein the bicomponent fibers are continuous. A sixteenth embodiment is any combination of the first fifteen embodiments, wherein the first component and the second component are heated to a temperature of from about 110°C to about 180°C. A seventeenth embodiment is any combination of the first sixteen embodiments, wherein the first component and the second component are heated to a temperature of about 130°C to about 150°C. An eighteenth embodiment is any combination of the first seventeen embodiments, wherein the bicomponent fiber has a linear mass density of from about 2 denier to about 16 denier. A nineteenth embodiment is any combination of the first eighteen embodiments, wherein the first component is about 40 to about 60 weight percent of the first and second components. A twentieth embodiment is any combination of the first nineteen embodiments, wherein the first component is about 50% by weight of the first and second components.

[0064] A 21st embodiment is any combination of the first 20 embodiments, wherein the second component is a polymer comprising a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, nylon, PHB, PTFE, and combinations thereof. A twenty-second embodiment is any combination of the first twenty-one embodiments, further comprising a second bicomponent fiber comprising a first component and a second component having substantially different melting points, the lower melting point portion acting as a binder fiber. A twenty-third embodiment is any combination of the first twenty-two embodiments, wherein the second bicomponent fibers comprise from about 30 to about 70 weight percent of the filter media. A twenty-fourth embodiment is any combination of the first twenty-three embodiments, wherein the second biocomponent fiber comprises a core and a sheath. A twenty-fifth embodiment is any combination of the first twenty-four embodiments, in which the core is eccentric with the sheath.

[0065] In another aspect, there is provided an air filter product comprising the filter media of any combination of the first 25 embodiments. In another aspect, a first embodiment is a filter medium comprising bicomponent fibers comprising a first component and a second component. At least a portion of the first component separates from the second component when heated to a threshold temperature. The first component comprises a thermoplastic elastomer material and a thermoplastic material. The thermoplastic elastomer material comprises less than about 25% by weight of the first component. The second embodiment is the first embodiment, in which the threshold temperature is about 110°C to about 180°C. A third embodiment is any combination of the first two embodiments, where the threshold temperature is between about 130°C and about 150°C. A fourth embodiment is a combination of any of the first three embodiments, where the first component has a lower melting point. A fifth embodiment is any combination of the first four embodiments, where the first component has a higher shrinkage ratio / percentage than the second component.

[0066] A sixth embodiment is a combination of any of the first five embodiments, wherein the first component has substantially the same melt viscosity as the second component. A seventh embodiment is any combination of the first six embodiments, further comprising a second biocomponent fiber comprising a first component and a second component, wherein the first component remains substantially adhered to the second component when heated to a threshold temperature. An eighth embodiment is any combination of the first seven embodiments, wherein the second bicomponent fibers comprise from about 30 to about 70 weight percent of the filter media. A ninth embodiment is any combination of the first eight embodiments, wherein the thermoplastic elastomer material is about 10 to about 20 weight percent of the first component. A tenth embodiment is any combination of the first nine embodiments, wherein the thermoplastic elastomer material is 15% by weight of the first component.

[0067] In another aspect, there is provided an air filter product comprising the filter media of any combination of the first ten embodiments. In another aspect, a first embodiment is a method of making a filter medium, the method comprising providing a bicomponent fiber having a first component and a second component, and heating the biocomponent fiber such that at least a portion of the first component separates from the second component. The first component comprises a thermoplastic elastomeric material and a thermoplastic material. The thermoplastic elastomeric material is less than about 25% by weight of the first component. A second embodiment is the first embodiment, further comprising extruding the first component and the second component together to form a bicomponent fiber. A third embodiment is any combination of the first two embodiments, where the first and second components are extruded to form a split pi bicomponent fiber. A fourth embodiment is any combination of the first three embodiments, where the biocomponent fiber is heated to a temperature of from about 110°C to about 180°C. A fifth embodiment is any combination of the first four embodiments, wherein the biocomponent fiber is heated to a temperature of about 130°C to about 150°C.

[0068] A sixth embodiment is any combination of the first five embodiments, further comprising crimping the bicomponent fibers. A seventh embodiment is any combination of the first six embodiments, wherein the crimp number of the biocomponent fiber is from about 8 to about 20 crimps per inch. An eighth embodiment is any combination of the first seven embodiments, further comprising applying a coating to the bicomponent fiber and spin finishing the fiber. A ninth embodiment is any combination of the first eight embodiments, further comprising shrinking the first component by at least about 10% during heating. A tenth embodiment is any combination of the first nine embodiments, further comprising shrinking the first component by at least about 30% during heating.

[0069] An eleventh embodiment is any combination of the first ten embodiments, further comprising carding the bicomponent fibers. A twelfth embodiment is any combination of the first eleven embodiments, further comprising forming the biocomponent fibers by a process selected from the group consisting of spunbond and meltblown. A thirteenth embodiment is any combination of the first twelve embodiments, further comprising blending the first bicomponent fiber with a second bicomponent fiber, the second bicomponent fiber having a first component and a second component that remain substantially adhered to each other during heating. A fourteenth embodiment is any combination of the first thirteen embodiments, wherein the second bicomponent fibers comprise from about 30 to about 70 weight percent of the filter media.

[0070] In another aspect, there is provided an air filter produced from the method of any combination of the above 14 embodiments. In another aspect, a first embodiment is a bicomponent fiber comprising a first component and a second component, the first component having a lower melting point than the second component and comprising a thermoplastic elastomeric material and a thermoplastic material, the thermoplastic elastomeric material being less than about 25% by weight of the first component. The second embodiment is the first embodiment, where the first component has a higher shrinkage ratio / percentage / rate than the second component. A third embodiment is any combination of the first two embodiments, wherein the thermoplastic elastomer material is about 15% by weight of the first component. A fourth embodiment is any combination of the first three embodiments, wherein the thermoplastic material of the first component comprises a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, CoPET, nylon, PLA, and combinations thereof. A fifth embodiment is any combination of the first four embodiments, wherein the thermoplastic elastomeric material comprises a material selected from the group consisting of styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymers, thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof.

[0071] A sixth embodiment is any combination of the first five embodiments, wherein the bicomponent fiber comprises a split pie. A seventh embodiment is any combination of the first six embodiments, wherein the first component is about 40 to about 60% by weight of the first and second components. An eighth embodiment is any combination of the first seven embodiments, wherein the second component is a polymer comprising a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, nylon, PHB, PTFE, and combinations thereof.

[0072] In another aspect, there is provided an absorbent pad for a wound dressing comprising bicomponent fibers of any combination of the above eight embodiments. In another aspect, there is provided a wound dressing comprising a bicomponent fiber of any combination of the above eight embodiments.

Claims

1. a bicomponent fiber comprising a first component and a second component, the first component having a lower melting point than the second component; the first component comprises a thermoplastic elastomer material and a thermoplastic material, and the thermoplastic elastomer material is less than about 25% by weight of the first component; filter medium.

2. 10. The filter media of claim 1, wherein the first component has a higher shrinkage ratio or percentage or rate than the second component.

3. 10. The filter medium of claim 1, wherein the thermoplastic elastomeric material is about 10 to about 20% by weight of the first component.

4. 10. The filter media of claim 1, wherein the thermoplastic elastomeric material is about 15% by weight of the first component.

5. 10. The filter medium of claim 1, wherein the first component has substantially the same melt viscosity as the second component.

6. 2. The filter medium of claim 1, wherein the thermoplastic material of the first component comprises a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, CoPET, nylon, PLA, and combinations thereof.

7. 2. The filter media of claim 1, wherein the thermoplastic elastomeric material comprises a material selected from the group consisting of styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymer elastomers, thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof.

8. The filter media of claim 1 , wherein the bicomponent fibers comprise split pie fibers.

9. 9. The filter media of claim 8, wherein the pie segments are concentric.

10. The filter medium of claim 8 , wherein the pie section is eccentric.

11. 10. The filter medium of claim 9, wherein the biocomponent fibers have a hollow center.

12. 10. The filter media of claim 9, wherein the hollow centers are concentric.

13. 10. The filter medium of claim 9, wherein the hollow center is eccentric.

14. The filter medium of claim 1 , wherein the bicomponent fibers comprise discontinuous staple fibers.

15. 10. The filter medium of claim 1, wherein the bicomponent fibers are continuous.

16. 10. The filter medium of claim 1, wherein the first component and the second component are heated to a temperature of about 110°C to about 180°C.

17. 10. The filter medium of claim 1, wherein the first component and the second component are heated to a temperature of about 130°C to about 150°C.

18. 10. The filter media of claim 1, wherein the bicomponent fibers have a linear mass density of from about 2 denier to about 16 denier.

19. 10. The filter medium of claim 1, wherein the first component is about 40 to about 60% by weight of the first and second components.

20. 10. The filter medium of claim 1, wherein the first component is about 50% by weight of the first and second components.

21. 2. The filter medium of claim 1, wherein the second component is a polymer comprising a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, nylon, PHB, PTFE, and combinations thereof.

22. 10. The filter media of claim 1, further comprising second bicomponent fibers comprising a first component and a second component having substantially different melting points, the lower melting point portion serving as a binder fiber.

23. 23. The filter medium of claim 22, wherein the second bicomponent fibers comprise from about 30 to about 70% by weight of the filter medium.

24. 23. The filter medium of claim 22, wherein the second biocomponent fibers comprise a core and a sheath.

25. 25. The filter medium of claim 24, wherein the core is eccentric with the sheath.

26. An air filter product comprising the filter media of claim 1.

27. a bicomponent fiber comprising a first component and a second component, wherein upon heating to a threshold temperature, at least a portion of the first component separates from the second component; the first component comprises a thermoplastic elastomer material and a thermoplastic material, the thermoplastic elastomer material being less than about 25% by weight of the first component; filter medium.

28. 28. The filter medium of claim 27, wherein the threshold temperature is from about 110°C to about 180°C.

29. 28. The filter medium of claim 27, wherein the threshold temperature is from about 130°C to about 150°C.

30. 28. The filter medium of claim 27, wherein the first component has a lower melting point than the second component.

31. 28. The filter media of claim 27, wherein the first component has a higher shrinkage ratio / percentage than the second component.

32. 28. The filter medium of claim 27, wherein the first component has substantially the same melt viscosity as the second component.

33. 30. The filter medium of claim 27, further comprising a second biocomponent fiber having a first component and a second component, wherein the first component remains substantially adhered to the second component when heated to a threshold temperature.

34. 34. The filter medium of claim 33, wherein the second bicomponent fibers comprise from about 30 to about 70% by weight of the filter medium.

35. 28. The filter medium of claim 27, wherein the thermoplastic elastomeric material is about 10 to about 20% by weight of the first component.

36. 28. The filter medium of claim 27, wherein the thermoplastic elastomer material is 15% by weight of the first component.

37. 1. A method for manufacturing a filter medium, comprising: providing a bicomponent fiber having a first component and a second component, the first component comprising a thermoplastic elastomeric material and a thermoplastic material, the thermoplastic elastomeric material being less than about 25% by weight of the first component; heating the biocomponent fiber such that at least a portion of the first component separates from the second component; A method comprising:

38. 38. The method of claim 37, further comprising extruding the first component and the second component together to form the bicomponent fiber.

39. 39. The method of claim 38, wherein the first component and the second component are extruded to form a split pi bicomponent fiber.

40. 38. The method of claim 37, wherein the biocomponent fiber is heated to a temperature of about 110°C to about 180°C.

41. 38. The method of claim 37, wherein the biocomponent fiber is heated to a temperature of about 130°C to about 150°C.

42. 38. The method of claim 37, further comprising crimping the bicomponent fibers.

43. 43. The method of claim 42, wherein the biocomponent fiber has a crimp number of about 8 to about 20 crimps per inch.

44. 38. The method of claim 37, further comprising applying a coating to the bicomponent fiber and spin finishing the fiber.

45. 38. The method of claim 37, further comprising shrinking the first component by at least about 10% during heating.

46. 38. The method of claim 37, further comprising shrinking the first component by at least about 30% during heating.

47. 38. The method of claim 37, further comprising carding the bicomponent fibers.

48. 38. The method of claim 37, further comprising forming the biocomponent fibers by a process selected from the group consisting of spunbond and meltblown.

49. 38. The method of claim 37, further comprising blending the first bicomponent fiber with a second bicomponent fiber, the second bicomponent fiber having a first component and a second component that remain substantially adhered to each other during heating.

50. 50. The method of claim 49, wherein the second bicomponent fibers comprise from about 30 to about 70% by weight of the filter medium.

51. 38. An air filter produced from the method of claim 37.

52. a first component and a second component, the first component having a lower melting point than the second component; the first component comprises a thermoplastic elastomer material and a thermoplastic material, the thermoplastic elastomer material being less than about 25% by weight of the first component; Bicomponent fiber.

53. 53. The fiber of claim 52, wherein said first component has a higher shrinkage ratio / percentage / rate than said second component.

54. 53. The fiber of claim 52, wherein the thermoplastic elastomeric material is about 15% by weight of the first component.

55. 53. The fiber of claim 52, wherein the thermoplastic material of the first component comprises a material selected from the group consisting of polyolefins, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, CoPET, nylon, PLA, and combinations thereof.

56. 53. The fiber of claim 52, wherein the thermoplastic elastomeric material comprises a material selected from the group consisting of styrene block copolymers (SBS, SIS, SEBS), olefin block polymers, thermoplastic polyolefin elastomers (TPO), thermoplastic polystyrene elastomers (TPS), polyester copolymers, thermoplastic vulcanizates (TPV), polyamide elastomers (PEBAX), thermoplastic polyurethanes (TPU), ionomers, ethylene vinyl acetate (EVA), propylene-based elastomers, propylene-ethylene copolymers, ethylene octane copolymers, and combinations thereof.

57. 53. The fiber of claim 52, wherein the bicomponent fiber comprises a split pie.

58. 53. The fiber of claim 52, wherein the first component is about 40 to about 60% by weight of the first and second components.

59. 53. The fiber of claim 52, wherein the second component is a polymer comprising a material selected from the group consisting of polyolefin, polyethylene (PE), polypropylene (PP), blends of PP and PE, PBT, PET, PLA, nylon, PHB, PTFE, and combinations thereof.

60. 53. An absorbent pad for a wound dressing comprising the bicomponent fiber of claim 52.

61. 53. A wound dressing comprising the bicomponent fiber of claim 52.

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