Skinned fibrous composite

SKINNED FIBROUS COMPOSITE FIELD

0002[001] The present teachings relate generally to a composite material exhibiting sound absorption, structural reinforcement, or both, and more particularly, to a composite material having an in-srtu skinned layer.

BACKGROUND

0004[002] Industry is constantly seeking new and/or improved materials and methods of providing sound and noise reduction in a variety of applications. Materials that exhibit sound absorption characteristics are often employed as a way to provide noise reduction in a wide range of industrial, commercial, and domestic applications. It is often desirable to reduce noises of machinery, engines, and the like. For example, in automotive applications, it may be undesirable for a passenger to hear noises coming from the engine compartment or from other places of the vehicle.

0005[003] In some sound absorption applications, facing layers, such as fabrics or scrims, may be added to the material (e.g., laminated to a bulk layer). The facing may provide additional sound absorption properties or may provide protection to the sound absorption material. The facing may provide an air flow resistivity mismatch between the material (e.g., a bulk layer) and the facing, which may allow for enhancing or tuning acoustic absorption performance. While the addition of one or more facing layers may be useful or beneficial in some applications, there are also times where the addition of a facing material may be too expensive, may be not possible (e.g., due to the desired facing material being unavailable), may add weight, and/or may too greatly increase the complexity of producing the composite material. Complexity may be, for example, potential issues with delamination, fabrication, handling, procuring raw materials, cost or pricing in the market, or a combination thereof.

0006[004] Industry is constantly seeking materials, and the methods for producing materials, having improved noise reduction characteristics in a variety of applications, such as through improved sound absorption materials for vehicles. It is further desirable to have sound absorption materials that do not require a separate facing material attached thereto but stiii provides effective sound absorption, compression resiliency, insulation, puncture resistance, or a combination thereof. It is also desirable to provide a material that has structural stiffness or structural properties. It is also desirable reduce cost, processing steps, materials, or a combination thereof, to create the sound absorption material. SUMMARY

0007[005] The present teachings meet one or more of the above needs by the improved devices and methods described herein. The present teachings provide improved sound absorption by creating a fibrous composite having one or more skin layers, which may be created in-situ. The present teachings contemplate a fibrous composite comprising a nonwoven lofted layer comprising fibers including thermoplastic lower melt bi-component fibers (e.g., as compared to the melting temperature of other fibers within the fiber blend, such as common or staple fibers). The fibrous composite may further include a skin layer formed on at least a portion of a surface of the nonwoven lofted layer. The skin layer may be formed through melting at least a portion of the surface of the nonwoven lofted layer so that bi-component fibers localized near the surface melt and density.

0008[006] Any combination of the following features of the fibrous composite are also within the scope of the teachings herein. The fibrous composite may exhibit sound absorption characteristics. The fibrous composite may be adapted to be used as a sound absorption material. The fibrous composite may include a pressure sensitive adhesive material. The pressure sensitive adhesive material may include a release liner for providing peel-and-stick functionality. The pressure sensitive adhesive material and optional release liner may be located on a surface of the nonwoven lofted layer opposite the skin layer for adhering the fibrous composite to a substrate. The nonwoven lofted layer may be a vertically lapped layer. The skin layer may extend along an entire surface of the nonwoven lofted layer. The fibrous composite may have more than one skin layer. The fibrous composite may have a skin layer on two or more surfaces of the nonwoven lofted layer (e.g., a top surface and a bottom surface). The skin layer may be formed during an in-situ process through a laminator. The skin layer may be smooth. The skin layer may be adapted to serve as a foundation for additional layers of material. The skin may enhance the structural stiffness of the fibrous composite (e.g., without adding fiber weight like adding a facing layer might). The skin layer may enhance the compression resiliency of the fibrous composite. The fibrous composite may include one or more additional nonwoven lofted layers. A skin layer may be sandwiched between two layers (e.g., nonwoven iofted layers). Two or more fibrous composites may be stacked and secured to each other (e.g., by one or more lamination processes). The fibrous composite may have a total thickness of about 2 mm to about 155 mm. One or more skin layers may have an average thickness of about 100 pm or more. One or more skin layers may have a total thickness of about 500 pm to about 1500 pm. [007] The present teachings also contemplate a method of forming the fibrous composite as described herein. The method may include forming a nonwoven lofted layer. The nonwoven lofted layer may comprise fibers including thermoplastic lower melt bi-component fibers (e.g., as compared to the melting temperature of other fibers within the matrix, such as staple fibers or common fibers). The method may further include forming a skin layer on at least a portion of a surface of the lofted layer by melting at least a portion of the surface of the nonwoven lofted layer so that the bi-component fibers localized at or near the surface melt and densify. The step of forming a nonwoven lofted layer may be performed by lapping (e.g., vertical lapping) or air laying the fibers. The forming a skin layer may be an in-situ process performed by laminating the surface of the nonwoven lofted layer. The skin layer may extend along an entire surface of the nonwoven lofted layer. The fibrous composite may have a skin layer on two or more surfaces of the nonwoven lofted layer. The step of forming a skin layer may be performed by a flat bed or heated pinch roll lamination process.

0009[008] The present teachings, therefore, provide a skinned fibrous composite, and method of forming the fibrous composite, which provides air flow resistance while enhancing the structural stiffness of the composite without having to add fiber weight to the core composite. The present teachings further provide an improvement in compression resiliency and stiffness to the composite.

DESCRIPTION OF THE DRAWINGS

0011[009] Fig. 1 is a cross-sectional view of a skinned fibrous composite in accordance with the present teachings.

0012[0010] Fig. 2 is a cross-sectional view of a multi-layered skinned fibrous composite in accordance with the present teachings.

0013[001] ] Fig. 3 is a side view of a skinned fibrous composite in accordance with the present teachings, showing the thickness of the skin layer in accordance with the present teachings.

0014[0012] Fig.4 is a side view of a skinned fibrous composite in accordance with the present teachings, showing the thickness of the skin layer in accordance with the present teachings.

0015[0013] Fig. 5 is a graph showing sound absorption of a skinned fibrous composite in accordance with the present teachings.

0016[0014] Figs. 6 and 7 are graphs showing results of compression or indentation testing on skinned fibrous composites in accordance with the present teachings. DETAILED DESCRIPTION

0017[0015] The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the teachings, its principles, and its practical application. Those skilled in the art may adapt and apply the teachings in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present teachings as set forth are not intended as being exhaustive or limiting of the teachings. The scope of the teachings should, therefore, be determined not with reference to the description herein, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. Other combinations are also possible as will be gleaned from the following claims, which are also hereby incorporated by reference into this written description.

0018[0016] Acoustic materials, such as fibrous composite materials like the materials as discussed herein, may have a wide range of applications, such as where sound absorption, compression resiliency, stiffness, structural properties, insulation, or a combination thereof are desired. For example, and not to serve as limiting, acoustic materials may be used in automotive applications, generator set engine compartments, commercial vehicle engines, in-cab areas, construction equipment, agriculture equipment, architectural applications, flooring, floormat underlayments, and even heating, ventilating and air conditioning (HVAC) applications. Acoustic materials may be suitable for (but not limited to) use as sound attenuation materials in vehicles, attenuating sound originating from outside a cabin of a motor vehicle and propagating toward the inside of the cabin. Acoustic materials may be used for machinery and equipment insulation, motor vehicle insulation, domestic appliance insulation, dishwashers, and commercial wall and ceiling panels. Acoustic materials may be used in the engine cavity of a vehicle, on the inner and outer dash panels and under the carpeting in the cabin, for example. Acoustic materials may be used inside cabs to provide acoustic absorption. Acoustic materials may be used in any application where a lighter weight acoustic material is desired. Acoustic materials may be used as interior decorative trim, especially if the acoustic material has a skin layer or other aesthetic layer. The acoustic sheets may be used in combination with other sound absorption materials. Acoustic materials may also be useful as an acoustic pin board material or as a ceiling tile.

0019[0017] Composite products, such as composite acoustic materials, may be formed, at least in part, from porous limp sheets with relatively high air flow resistances, porous bulk absorbers or spacer materials having air flow resistances substantially smaller than the limp sheets, or both. Methods for producing such composite products include those set out in co- owned international Application No. PCT/AU2005/000239 entitled ThermoformafoSe Acoustic

0020Product" (published as WO/2005/081226), the contents of which are hereby incorporated herein by reference.

0021[0018] In general, materials used for sound absorption (e.g., composite acoustic materials, nonwoven materials, woven materials, the like, or combination thereof) must exhibit air permeability properties. Critical characteristics include air flow resistance (resistance to air flow through the material), tortuosity (the path length of a sound wave within the material), and porosity (void to volume ratio). With fibrous materials, air flow resistance (and air flow resistivity) is an overwhelmingly critical factor controlling sound absorption.

0022[0019] Air flow resistance is measured for a particular material at a particular thickness. The air flow resistance is normalized by dividing the air flow resistance (in Rayls) by the thickness (in meters) to derive the air flow resistivity measured in Rayls/m. ASTM standard C522-87 and ISO standard 9053 refer to the methods for determination of air flow resistance for sound absorption materials. Within the context of the teachings herein, air flow resistance, measured in mks Rayls, will be used to specify the air flow resistance; however other methods and units of measurement are equally valid. Within the context of the described teachings, air flow resistance and air flow resistivity can be assumed to also represent the specific air flow resistance, and specific airflow resistivity, respectively. Random incidence sound absorption may also be tested per SAE J2883 in a small reverberant chamber.

0023[0020] The sound absorption coefficient (SAC) and sound transmission loss (STL) level of an air permeable or porous material, such as a bulk composite, may be improved and tuned by layering materials together and/or by adding one or more skin layers. These layers may have different levels of specific air flow resistance. The building of these types of layers may create a multi-acoustic impedance mismatched profile throughout the thickness of the composite. This mismatched profile amplifies the noise reduction capability (both SAC and STL) of the composite. Surprisingly, the results are a noise reduction and/or sound absorption at a greater level than that of the summation of the performance of the individual layers as standalone units. Therefore, the layers of materials produce a generally synergistic effect to improve sound absorption performance.

0024[0021] The fibrous composite may function to absorb sound to reduce noise. The fibrous composite may include one or more layers (e.g., one or more lofted layers, one or more skin layers, or a combination thereof). The layers may be of different materials. Some layers may be of the same materials. The type of materials forming the layers, order of the layers, number of layers, thickness of layers, or a combination thereof, may be chosen based on the air flow resistive properties of each material, the desired air flow resistive properties of the fibrous composite as a whole, the desired weight, density and/or thickness of the fibrous composite (e.g., based upon the space available where the fibrous composite will be installed), or a combination thereof. For example, some layers may have a lower air flow resistance while other layers may have a higher air flow resistance. The layering of layers having different air flow resistive properties may produce a multi-impedance acoustic mismatched profile through the entire fibrous composite, which provides improved noise reduction capability of the fibrous composite. Therefore, the layers (or skins) may be arranged so that a layer (or skin) of higher specific air flow resistance is joined to, or formed on, or is adjacent to one or more layers of a different specific air flow resistance (e.g., a lower airflow resistance).

0025[0022] Any of the materials described herein may serve as one or more layers of the fibrous composite. Any of the materials described herein may be combined with other materials described herein (e.g., in the same layer or in different layers of the fibrous composite). The fibrous composite may include a plurality of layers, some or all of which serve different functions or provide different properties to the fibrous composite (when compared to other layers of the fibrous composite). The ability to combine layers and skins of materials having different properties may allow the fibrous composite to be customized based on the application to tune the material to have desired properties, airflow resistance, acoustic absorption, structural characteristics, and the like. One or more fibrous composite layers may provide insulation. One or more fibrous composite layers may include one or more adhesive materials (e.g., as part of the fibers of the layer or as a separate element in or on the layer) for binding the fibers together, for binding layers together, or both. One or more fibrous composite layers may support a skin layer, other material layer, or both. One or more fibrous composite layers may provide heat resistance (e.g., if the fibrous composite is located in an area that is exposed to high temperatures). One or more fibrous composite layers may provide stiffness to the fibrous composite. Additional stiffness, structural properties, compression resistance, compression resiliency, or a combination thereof, may be provided by the skin layer (or one or more skin layers in combination with the one or more fibrous composite layers). As described herein, compression can refer to a force applied to the material and that is the same size or larger than the surface of the material (e.g., a fiat piate extending across the entire surface of a fibrous composite). Compression can also refer to and encompass indentation, where a force is applied to only a portion of the surface of the material. For example, indentation can be achieved by a person stepping on a fibrous composite or dropping or setting a tool on a fibrous composite, where the entire surface of the fibrous composite is not experiencing the applied force. Where the word "compression" is used herein, it is contemplated that the word "indentation" is also within the scope of the teachings and claims and can be substituted for

0026"compression". One or more fibrous composite layers may provide flexibility and/or softness to the fibrous composite. One or more fibrous composite layers may attach directly to a wall or surface of a substrate to provide acoustic absorption. The fibrous composite may be attached to a substrate via a pressure sensitive adhesive (or other adhesive) and/or via one or more fasteners, One or more fibrous composite layers may be any material known to exhibit sound absorption characteristics. One or more fibrous composite layers may be at least partially formed as a web of material (e.g., a fibrous web). One or more fibrous composite layers may be formed from nonwoven material, such as short fiber nonwoven materials. One or more fibrous composite layers may be a porous bulk absorber (e.g., a lofted porous bulk absorber formed by a carding and/or lapping process). One or more fibrous composite layers may be formed by air laying. The fibrous composite may be formed into a generally flat sheet. The fibrous composite (e.g., as a sheet) may be capable of being rolled into a roll. The fibrous composite (or one or more of the fibrous composite layers) may be an engineered 3D structure. It is clear from these potential layers that there is great flexibility in creating an acoustic material that meets the specific needs of an end user, customer, installer, and the like.

0027[0023] Acoustic materials for sound absorption may have a relatively high air flow resistance to present acoustic impedance to the sound pressure wave incident upon the material. Air permeability should be managed to ensure predictable and consistent performance. This may be achieved through management of fiber sizes, types, and lengths, among other factors. A homogeneous, short fiber nonwoven textile may be desirable. In some applications, desirable levels of air permeability may be achieved by combining plural nonwoven materials of differing densities together to form a composite product. A combination of materials having low permeability with those having high permeability can be used to achieve locally reactive acoustic behavior. One or more of the acoustic materials (e.g., nonwoven materials) may be short fiber technology-based (SFT-based) materials. The SFT-based materials may be formed using gravity deposition or a process similar to air laying. The SFT-based materials may be densified. A SFT- based textile can be advantageous in terms of reducing cost and providing a significant environmental benefit by reducing or eliminating the amount of waste disposed to iandfiii. One or more fibrous composite layers may be formed by needle-punching, alone or in combination with any of the methods of forming the layer described herein or known in the art.

0028[0024] A fibrous composite layer (e.g., nonwoven material) may be formed to have a thickness and density selected according to the required physical and air permeability properties desired of the finished fibrous composite layer (and/or the fibrous composite as a whole). The fibrous composite layer may be any thickness depending on the application, location of installation, shape, fibers used (and the lofting of the fibrous composite layer), or other factors. The density of the fibrous composite layer may depend, in part, on the specific gravity of any additives incorporated into the material comprising the Iayer (such as nonwoven material), and/or the proportion of the final material that the additives constitute. Bulk density generally is a function of the specific gravity of the fibers and the porosity of the material produced from the fibers, which can be considered to represent the packing density of the fibers.

0029[0025] A iow density fibrous composite material, which may be one or more of the fibrous composite layers, may be designed to have a iow density, with a finished thickness of about 1 ,5 mm or more, about 4 mm or more, about 5 mm or more, about 8 mm or more, or about 8 mm or more. The finished thickness may be about 350 mm or less, about 250 mm or less, about 150 mm or less, about 75 mm or less, or about 50 mm or less. The fibrous composite material, which may be one or more of the fibrous composite layers, may be formed as a relative iy thick, low density nonwoven, with a bulk density of 10 kg/m³ or more, about 15 kg/m³ or more, or about 20 kg/m³ or more. The thick, low density nonwoven may have a bulk density of about 200 kg/m³ or less, about 100 kg/m³ or less, or about 80 kg/m³ or less. The fibrous composite material (e.g., serving as one or more fibrous composite layers) thus formed may have an air flow resistivity of about 400 Rayls/m or more, about 800 Rayis/m or more, or about 100 Rayls/m or more. The fibrous composite material may have an air flow resistivity of about 200,000 Rayls/m or less, about 150,000 Rayls/m or less, or about 100,000 Rayls/m or less. Low density fibrous composite materials may even have an air flow resistivity of up to about 275,000 Rayis/m,

0030[0026] Additional sound absorption may also be provided by a skin Iayer on the fibrous composite layer (e.g., by an in-situ skinning process). A skin layer of the fibrous composite may provide additional air flow resistance (or airflow resistivity) to the fibrous composite. For example, the skin Iayer may have an air flow resistivity of about 100,000 Rayls/m or higher, about 275,000 Rayls/m or higher, 1 ,000,000 Rayls/m or higher, or even 2,000,000 Rayls/m or higher.

0031[0027] Where one or more of the layers of the fibrous composite is a fibrous composite material of a low density material (such as a nonwoven material), the nonwoven material may be used as a porous bulk absorber, in order to form a porous bulk absorber of the desired dimensions, once the nonwoven material is formed, the nonwoven material may be vertically lapped, rotary lapped, cross-lapped, or air laid and then thermally bonded. High density nonwoven materials may also be used for a variety of applications, such as, for example, a porous Simp sheet. The low and high density nonwoven materials may be used together to form a plurality of layers of the fibrous composite or the entire fibrous composite.

0032[0028] The material fibers thai make up a fibrous composite maierial/layer may have a linear mass density from about 0.5 to about 25 denier, about 1 to about 6 denier, or about 1 to about 4 denier. The fibers may be a mix of different denier fibers. For example, a fibrous material may be formed from a mix (e.g., 50/50 mix) of 1.4 denier fibers and 2 denier fibers, in another example, coarser fibers may be used, such as 8 denier fibers mixed with 2 denier fibers. The fibers may have a staple length of about 1.5 millimeters or greater, or even about 70 millimeters or greater or about 100 mm or greater (e.g., for carded fibrous webs). For example, the iengih of the fibers may be between about 30 millimeters and about 85 millimeters, with an average or common length of about 50 or 51 millimeters staple length, or any length typical of those used in fiber carding processes. Short fibers may be used in some other nonwoven processes, such as the formation of air laid fibrous webs. For example, some or all of the fibers may be a powder- like consistency (e.g., with a fiber iengih of about 0.5 millimeters or less, about 2 millimeters or less, or about 3 millimeters or less (e.g., about 0.5 millimeters to about 3 millimeters}). Fibers of differing lengths may be combined to form the acoustic composite layer. The fiber length may vary depending on the application, the acoustic properties desired, dimensions and/or properties of the acoustic material (e.g., density, porosity, desired air flow resistance, thickness, size, shape, and the like of the acoustic layer), or any combination thereof. More effective packing of the shorter fibers may allow pore size to be more readily controlled in order to achieve desirable acoustic characteristics.

0033[0029] In some applications, the use of shorter fibers may have advantages in relation to the performance of the acoustic material The selected air flow resistivity achieved using short fibers may be significantly higher than the air flow resistivity of a conventional nonwoven material comprising substantially only conventional staple fibers having a long length of, for example, from at least about 30 mm and less than about 100 mm. Without being limited by theory, it is believed that this unexpected increase in air flow resistance may be attained as a result of the short fibers being able to pack more efficiently (e.g., more densely) in the nonwoven material than long fibers. The shorter length may reduce the degree of disorder in the packing of the fibers as they are dispersed onto a surface, such as a conveyor, or into a preformed web during production. The more ordered packing of the fibers in the material may in turn lead to an increase in the air flow resistivity. In particular, the improvement in fiber packing may achieve a reduced interstitial space in between fibers of the nonwoven material to create a labyrinthine structure that forms a tortuous path for airflow through the material, thus providing a selected airflow resistance, and/or selected air flow resistivity. Accordingly, it may be possible to produce comparatively lightweight nonwoven materials without unacceptably sacrificing performance.

0034[0030] The fibers forming one or more fibrous composite layers may be natural or synthetic fibers. Suitable natural fibers may include cotton, jute, wool, cellulose, glass, and ceramic fibers. Suitable synthetic fibers may inciude polyester, polypropylene, polyethylene, Nylon, aramid, imide, acryiate fibers, or combination thereof. The fibrous composite layer material may comprise polyester fibers, such as polyethylene terephthalate (PET), and co- polyester/polyester (CoPET/PET) adhesive bi-component fibers. The fibers may be 100% virgin fibers, or may contain fibers regenerated from posioonsumer waste (for example, up to about 90% fibers regenerated from postconsumer waste). The fibers may be a biend of fibers. For example, PET staple fibers and bi-component binder PET fibers may be mixed and used to form one or more layers of the fibrous composite,

0035[0031] One or more layers of the fibrous composite may include a plurality of bi- component fibers. The bi-comppnent fibers may be a thermoplastic lower melt bi-component fiber. The bi-component fibers may have a lower melting temperature than the other fibers within the mixture (e.g., a lower melting temperature than common or staple fibers). The bi-cornponeni fibers may enable the fiber matrix to be mechanically carded, lapped, artd fused in space as a network so that the materiai will have structure and body and can be handled, laminated , fabricated, installed as a cut or molded part, or the like to provide acoustic absorption. The bi- component fibers may inciude a core material and a sheath material around the core material. The sheath materiai may have a lower melting point than the core material. For example, the bi- component fibers may be a polyester sheath material surrounding a polyester core. The sheath material may have a melt temperature of about 250 degrees C or lower, about 200 degrees C or lower, about 180 degrees C or lower, about 150 degrees C or lower, or about 1 10 degrees C or lower. The core material may have a melt temperature greater than the melt temperature of the sheath materiai (e.g., about 256 degrees C). The web of fibrous materiai may be formed, at ieast in part, by heating the material to a temperature to soften the sheath material of at least some of the bi-component fibers. The temperature to which the fibrous web is heated to soften the sheath material of the bi-component may depend upon the physical properties of the sheath materiai. For a polyethylene sheath, the temperature may be about 140 degrees C to about 180 degrees C. For a polypropylene sheath, the temperature may be higher (for example, about 180 degrees C), The bi-component fibers may be formed of short lengths chopped from extruded bi- component fibers. The bi-component fibers may have a sheath-to-core ratio (in cross-sectional area) of about 26% to about 35%, [0032] The fibers may be used to form a thermoformable nonwoven material, which indicates a nonwoven material that may be formed with a broad range of densities and thicknesses and that contains a thermoplastic and/or thermoset binder. The thermoformable nonwoven material may be heated and thermoformed into a specifically shaped thermoformed product.

0036[0033] The fibers of one or more layers of the fibrous composite may be blended or otherwise combined with suitable additives such as other forms of recycled waste, virgin (non- recycled) materials, binders, fillers (e.g., mineral fillers), adhesives, powders, thermoset resins, coloring agents, flame retardants, longer staple fibers, etc., without limitation. One or more Iayers formed may be free of other additives.

0037[0034] The fibers forming one or more layers of the fibrous composite may be formed into a nonwoven web using nonwoven processes including, for example, blending fibers (e.g., blending bi-component fibers, conventional staple fibers, or combination thereof), carding, lapping, air laying, mechanical formation, or combination thereof. The fibers of one or more fibrous composite Iayers may be opened and blended using conventional processes. The fibers may be blended within the structure of the fibrous web. A carded web may be cross-lapped or verticaily lapped, to form a voluminous or lofted nonwoven web. The carded web may be vertically lapped according to processes such as "Struto" or "V-Lap", for example. This construction provides a web with relative high structural integrity in the direction of the thickness of the composite sound absorber, thereby minimizing the probability of the web failing apart during application, or in use. Carding and lapping processes create a nonwoven fiber layer that has good compression resistance through the vertical cross-section and enables the production of a lower mass acoustic treatment, especially with lofting to a higher thickness without adding significant amounts of fiber to the matrix. It is contemplated that a small amount of hollow conjugate fiber (i.e., in a small percentage) may improve lofting capability and resiliency to improve sound absorption. Such an arrangement also provides the ability to achieve a low density web with a relatively low bulk density. An air laid or mechanically formed web may also be produced, though formation of a bulk layer by a lapping process may enable higher thickness at lower weights (or lower densities) as compared to air laying. The web may then be thermally bonded, air bonded, mechanically consolidated, the iike, or combination thereof, to form a cohesive nonwoven insulation or acoustic absorption material.

0038[0035] The fibrous composite may include one or more skin Iayers, The skin layer may be formed in~situ. The one or more skin layers may function to provide additional air flow resistive properties to the fibrous composite. The one or more skin layers may act similarly to a facing layer to become an air flow resistive layer which can enhance the sound absorption of the nonwoven lofted layer (e.g., porous bulk absorber) that may be free of any separate facing layer. The one or more skin layers may act as an engineered solution that may be less costly than those which require separately laminated scrims, fabrics and films but achieve the same, greater, or comparable air flow resistance or air flow resistivity performance. The one or more skin layers may provide structural properties to the fibrous composite (e.g., compression resilience, stiffening, compression resistance, or a combination thereof). The skin layer (and/or the fibrous composite in general) may serve as a foundation upon which another material or layer can be attached. For example, another lofted layer may be attached to the skin layer of a first lofted layer so that the skin is sandwiched between two lofted layers.

0039[0038] The skin layer may be formed on the surface of the fibrous composite (or a layer of the fibrous composite). The skin layer may be formed as an in-situ process by applying heat at or near the surface of the nonwoven lofted layer of the fibrous composite. As the heat is applied, the bi-component fibers localized near the surface of the nonwoven lofted layer may soften and/or melt. The softened bi-component fiber material may flow through the matrix of fibers forming the nonwoven lofted layer. The softened bi-component fibers may act to plug the free volume space of the fiber matrix, particularly at the surface of the material. The softened bi- component fiber material may then density to create the resulting skin layer. The resulting skin layer may be a smooth layer of material that provides some structural characteristics (e.g., stiffness, compression resilience) to the fibrous composite. The resulting skin layer may create an aesthetically pleasing took to the material. The smooth layer may also be used as a foundation for supporting other materials and/or for adhering other materials thereto to provide additional properties. The skin layer may assist in preventing fraying or unraveling of the fibrous composite. The skin layer may be preferred over a facing layer, as it is not a separately attached layer, thereby reducing the likelihood of the layers coming apart. The method of skinning may be performed using a laminator to heat one or more outer surfaces of the nonwoven lofted layer to soften and/or melt the bi-component fibers located at or near the surface of the nonwoven lofted layer. The method may be performed, for example, through conductive heat transfer and pressure via a calender, a flat bed or heated pinch roll lamination process to effectively skin one or more sides of the nonwoven lofted material to create an itvsiiu air flow resistive mechanical layer.

0040[0037] When the fibrous composite is passed through a laminator, for example, the temperature, pressure, and time within the laminator, may be varied depending on the blend of fibers, the level and thickness of skin desired, or other factors. The laminator may be set to a temperature that allows the sheath material of the bi -component fibers to soften and/or melt Therefore, the iaminator may be set to a temperature up to about 250 degrees C (or to any temperature capable of softening and/or melting the sheath material of the bi-component fibers). The line may be slowed depending the blend and level of skin desired, so that time, temperature and pressure may form the skin so the finder melts and flows and forms against the fiat belt pressing on it, thereby creating a skin. One or more surfaces of the fibrous composite may be skinned (e.g., if desired, the top and bottom surface can be skinned at the same time).

0041[0038] The skin may be located on at least a portion of a surface of the nonwoven lofted material. The skin layer may extend over and along an entire surface of the nonwoven lofted material. The fibrous composite may have a skin layer on two or more surfaces of the nonwoven iofted material. For example, opposing sides of the nonwoven lofted material may both have a skin Iayer.

0042[0039] A skin layer may have any thickness that achieves the desired characteristics. The skin Iayer may have an average thickness of about 50 micrometers or thicker, about 100 micrometers or thicker, about 500 micrometer or thicker, or about 700 micrometers or thicker. The skin layer may have an average thickness of about 2500 micrometers or less, about 2000 micrometers or less, about 1500 micrometers or less, or about 1200 micrometers or less. Each skin Iayer within the fibrous composite may have a different average thickness. Thicker skins (e.g., about 500 micrometers or greater, or about 700 micrometers or greater) may be employed where greater robustness is desired. For example, a thicker skin may reduce puncturing of the material, provide compression resistance, withstand greater forces, stiffen the composite, or a combination thereof. Where it is desired to provide a less pronounced skin, a thinner skin may be formed in the composite.

0043[0040] The fibrous composite may include a plurality of layers. For example, the fibrous composite may inciude a nonwoven lofted material layer having a skin layer. A second nonwoven lofted material having a skin layer may be positioned in a stacked relation with the first nonwoven lofted material having a skin Iayer. The fibrous composite, therefore, may include a top layer being a skinned layer, a first nonwoven iofted material, another skin Iayer, and another nonwoven Iofted material (where the skin layer is sandwiched between the two nonwoven iofted materials), it is contemplated that additional layers can also be added. The sandwiched skin layer may act to provide additional structural support to the fibrous composite. The sandwiched skin Iayer, in combination with the other layers, may enhance the acoustic impedance mismatch between the layers to enhance the acoustic absorption and/or air flow resistivity of the material. The layers may be provided in any order. Additional Iayers are also contemplated (e.g., higher density materials, porous Simp sheets, fabrics, scrims, meshes, etc.). The layers may be attached to each other by one or more lamination processes, one or more adhesives, or a combination thereof,

0044[0041] The total thickness of the fibrous composite may depend upon the number and thickness of the individual layers . St is contemplated that the totai thickness may be about 0.5 mm or more, about 1 mm or more, or about 1.5 mm or more. The total thickness may be about 300 mm or less, about 250 mm or less, or about 175 mm or Sess. For example, the thickness may be in the range of about 2 mm to about 155 mm. It is also contemplated that some of the individual layers may be thicker than other layers. The thickness may vary between the same types of layers as well. For exampie, two lofted layers in the fibrous composite may have different thicknesses. The composite may be tuned to provide more general broad band absorption by adjusting the specific air flow resistance and/or the thickness of any or all of the layers.

0045[0042] The fibrous composite layers {e.g., one or more nonwoven lofted layers, one or more skin Iayers, or a combination) may be bonded together to create the finished fibrous composite. One or more layers may be bonded together by elements present in the layers, For example, the binder fibers in the layers may serve to bond the layers together. The outer layers (i.e., the sheath) of bi-component fibers in one or more layers may soften and/or meil upon the application of heat, which may cause the fibers of the individual layers to adhere to each other and/or to adhere to the fibers of other Iayers. Layers (e.g., skin layers) may be formed by one or more lamination processes. Other layers (e.g., a nonwoven lofted layer or skin layer to another nonwoven lofted layer or skin layer) may be joined through one or more lamination processes. One or more adhesives may be used to join two or more layers. The adhesives may be a powder or may be applied in strips, sheets, or as a liquid, for exampie. Preferably, the adhesive does not block the air fiow through the material (e.g., does not plug openings, perforations, pores, or the iike).

0046[0043] The fibrous composite, or parts thereof, may be formed or assembled using a lamination process. For example, the fibrous composite may be constructed by carding and lapping one or more thicker nonwoven layers and applying heat via lamination to form the skin layer on the surface of the nonwoven layers. The one or more nonwoven layers (e.g. , having a skin layer) may be laminated to another nonwoven layer within the nonwoven production and laminating process, or as separate processes. Additional layers can be laminated in the same way.

0047[0044] Acoustic properties of the fibrous composite (and/or its layers) may be impacted by the shape of the fibrous composite. The fibrous composite, or one or more of its Iayers, may be generally flat. The finished fibrous composite may be fabricated into cut-to-print two- dimensional fiat parts for installation into the end user, installer, or customer's assembly. The acoustic material may be formed into any shape. For example, the acoustic material may be molded (e.g., into a three-dimensional shape) to generally match the shape of the area to which it will be installed. The finished fibrous composite may be moided-to~print into a three-dimensional shape for installation into the end user, installer, or customer's assembly. The three-dimensional geometry of a molded product may provide additional acoustic absorption. The three-dimensional shape may provide structural rigidity and an air space. Such a shape may also form partially enclosed cells, such as a honeycomb or egg-carton type structure, that may provide local reactivity and increase fhe acoustical performance of the thermo-formed acoustic maieriai.

0048[0045] An adhesive may be located on the bottom layer (e.g., the layer of the fibrous composite opposite a top skin layer), an opposing (e.g., top) Iayer, one or more intermediate layers (e.g., to join one or more lofted layers), or a combination thereof . The adhesive may allow for adhering the fibrous composite to a desired substrate. The acoustic material may be provided with a pressure sensitive adhesive (PSA), The PSA may be applied from a roil and laminated to the back side of the fibrous composite layer maieriai (e.g., on the side of the acoustic composite layer opposite the top skin layer), which may be performed concurrently with the lamination to form one or more skin layers (e.g., a top skin Iayer). A release liner may carry the PSA. Prior to installation of the acoustic material, the release liner may be removed from the pressure sensitive adhesive to allow the composite sound absorber to be adhered to a panel, substrate, or surface. For some acoustic materials intended to be used as input components, for example on a vehicle production- line, it is desirable that the acoustic material can be installed quickly and easily. To achieve this, for some applications, it may be beneficial to provide a release liner with a high tear strength that is easy to remove.

0049[0046] The PSA may be provided as part of a tape material comprising: a thin flexible substrate; a PSA substance carried on a single side of the substrate, the PSA substance being provided along a length of fhe substrate (e.g., in an intermittent pattern or as a complete layer); and optionally a mesh carried on the single side. The PSA may be coated onto a silicone coated plastic or paper release liner. The PSA may be of the supported design, where the PSA layer may be bonded to a carrier film, and the carrier film may be bonded to fhe fibrous composite layer. A thin flexible substrate may be located on the side of the PSA Iayer opposite the carrier film. The end user may then remove the thin flexible substrate (e.g. , release liner) to install the part to the target surface. The supported construction may be up to 100% coverage, or the PSA may be supplied in an intermittent pattern. The supported construction may include embedded mesh. [0047] The purpose of the substrate of the tape material is to act as a carrier for the PSA substance so that the PSA substance can be applied (adhered) to the sound absorbing material. The substrate further acts as the release liner and can be subsequently removed by peeling it away, leaving the PSA substance exposed on the side where the substrate used to be. The newly exposed face of the PSA substance can be applied to a target surface, for example such as a panel or surface, to adhere the composite sound absorber to the target surface.

0050[0048] The entire side (e.g., about 100%) of the side (i.e., the bottom layer) of the fibrous composite may be coated with the PSA. If provided in an intermittent PSA coating, depending on the size and spacsng of the applied portions of the intermittent PSA coating, the percentage of coated area can be varied. The applied area of the coating can vary between about 10 and about 90%, or more specifically about 30% to about 40%, of the area of the substrate, for example.

0051[0049] The intermittent coating may be applied in strips or in another pattern. This can be achieved by hot-meit coating with a slot die, for example, although it can also be achieved by coating with a patterned roller or a series of solenoid activated narrow slot coating heads, for example, and may also include water and solvent based coatings, in addition to hot-melt coating.

0052[0050] Where the PSA coating is applied in strips, the spacing of the strips may vary depending on the properties of the acoustic material. For example, a lighter acoustic material may need less PSA to hold the material in place. A wider spacing or gap between the strips can facilitate easier removal of the substrate, as a person can more readily find uncoated sections that allow an edge of the substrate to be lifted easily when it is to be peeled away to adhere the sound absorbing material to another surface.

0053[0051] By applying the adhesive in an intermittent pattern, such as longitudinal strips, it is possible to still achieve the coating weight desired for a particular application, while saving a large percentage of the PSA resin by coating only some portions of the total area. Thus, it may be possible to use a reduced amount of PSA substance because the sound absorbing material of certain embodiments is a lightweight and porous article that does not require an all-over coating. Lowering the overall amount of PSA used also has the effect of minimizing the toxic emissions and volatile organic compounds (VOC) contributed by the PSA substance used to adhere the sound absorbing material to a target surface. The described acrylic resin used for the PSA also has relatively Sow VOC content.

0054[0052] The pressure sensitive adhesive substance may be an acrylic resin that is curable under ultraviolet light, such as AcResin type DS3583 available from BASF of Germany. A PSA substance may be applied to substrate in a thickness of about 10 to about ISO microns, for example. The thickness may alternatively be from about 20 to about 100 microns, and possibly from about 30 to about 75 microns, for example.

0055[0053] Other types of PSA substance and application patterns and thicknesses may be used, as weli as PSA substances that can be cured under different conditions, whether as a result of irradiation or another curing method. For example, the PSA substance may comprise a hot- melt synthetic rubber-based adhesive or a UV-curing synthetic rubber-based adhesive.

0056[0054] The finished skinned fibrous composite may be a lighter weight and higher performing fibrous composite (e.g., as compared with a traditional lofted nonwoven material, with or without a separately applied facing layer). The fibrous composite may have a better value proposition (e.g., performance versus cost) than traditional sound absorption materials. The finished fibrous composite comprises a material whose properties can be adjusted via many methods. Adjustment can be made by altering thickness, density, fiber matrix, chemistry, method of bonding, and the like for each layer of the fibrous composite. It is contemplated that the fibrous composite may have any of the following advantages over other materials traditionally used; better non-acoustic properties, such as better temperature resistance, hydrolytic stability, compression resistance, and mold/mildew resistance (versus foams and natural fiber, for example); better compression resistance and performance stability (versus mineral wool, for example); easier fabrication and installation (versus traditional nonwoven materials having a separately formed and installed facing layer or perforated metal panels, for exampie); easier molding and creation of a lower VOG and/or lower toxicity (versus resonated natural fiber and fiberglass type products, for exampie); improved flexibility and/or softness (versus a honeycomb structure, for example); improved ability to mold into a desired shape (versus a honeycomb structure, for example); improved ability to tune more parameters in the absorption matrix, such as fibers, layers, thickness, and bulk density (versus a honeycomb structure, for example); and structural properties, such as by providing a desired stiffness to the material.

0057[0055] The finished skinned fibrous composite may still have sufficient flexibility and robustness to be able to be rolled without cracking or breaking of the one or more skin layers,

0058[0058] The finished skinned fibrous composite may provide improved sound absorption as compared to a fibrous composite without a skinned layer. The sound absorption may be increased by about 1% or more, about 2% or more, about 5 % or more, or about 10% or more. The sound absorption may be increased at particular frequencies. For example, the increase in acoustic performance or acoustic absorption may be observed at about 250 herte or more, about 500 hertz or more, or about 1000 hertz or more. Acoustic absorption may be further influenced by the fibers used. For example, a greater difference between acoustic performance of a skinned fibrous composite and a fibrous composite without a skinned layer may be observed when using fibers of a lower denier (e.g., about 5 denier or less, about 2 denier or less, or about 1 ,5 denier or less).

0059[0057] The finished skinned fibrous composite may provide improved compression resistance. The skin provides increased stiffness, and therefore compression may decrease. Upon an application of compression, the skinned fibrous composite (e.g., when compressed at its skinned side) may exhibit an indentation force deflection value that is higher than the indentation force deflection value of an identical fibrous composite without a skinned layer. The compression resistance of a skinned fibrous composite may be about 50% or greater, about 75% or greater, about 100% or greater, about 125% or greater, about 150% or greater or about 200% or greater than a fibrous composite without a skin layer.

0060[0058] Turning now to the figures, Figure 1 illustrates a cross-sectional view of a skinned fibrous composite 10. The fibrous composite 10 includes a lofted layer 12 (e.g., a fibrous layer formed by vertical lapping or air laying). The lofted layer 12 functions to provide sound absorption, compression resistance, insulation, or a combination thereof. The fibrous composite 10 further includes a skin layer 14, which is formed on a surface of the lofted layer 12. The fibrous composite 10 includes a pressure sensitive adhesive material 18 and a release liner 18 for peel-and~siick functionality to allow the fibrous composite 10 to be adhered to a substrate.

0061[0059] Figure 2 illustrates a cross-sectional view of a skinned fibrous composite 10 having multiple layers. The skinned fibrous composite 10 includes two lofted layers 12 and two skinned layers 14, though more layers of each are also possible. One skinned layer 14 serves as an exterior layer for the skinned fibrous composite 10, The other skinned layer 14 is sandwiched between the two lofted layers, which provides additional structural properties (e.g., compression resiliency and stiffening), as well as additional acoustic properties (e.g. , through the multi-acoustic impedance mismatched profile throughout the thickness of the composite) of the fibrous composite 10. On the opposing side of the fibrous composite 10 is a pressure sensitive adhesive material 18 and a release liner 18 for peel-and-stick functionality to allow the fibrous composite 10 to be adhered to a substrate.

0062[0060] Figures 3 and 4 are photos taken of exemplary skinned fibrous composites, identified as Sample A and Sample B, respectively. Sample A is a 25 mm in-sltu skinned composite with a density of about 1033 g/m². Sample B is a 25 mm in-situ skinned composite with a density of about 1335 g/m²,These images were taken under a calibrated visible light stereomicroscope, allowing for measurement of the skin thickness. As shown, the skin thickness ranges from about 700 pm to about 1200 pm, ihough skins having a thickness of about 100pm or greater is also contemplated and within the scope of the teachings.

0063[0061] ILLUSTRATIVE EXAMPLES

0064[0062] The following examples are provided to illustrate the disclosed fibrous structure and layers thereof, but are not intended to limit the scope thereof.

0065[0063] tiiustrative Example 1

0066[0064] A skinned fibrous composite material, Example 1 , is prepared using a mix of about

00671.4 denier staple PET fibers and about 2 denier bi-component binder PET fibers, where the mix is about 50/50. The fibers have a length of about 50 mm to about 85 mm, though other fiber lengths are expected to provide the same or similar results, and thus, are within the scope of the teachings herein. The fibers are opened, blended, carded, lapped, and thermobonded to produce a 27 mm thick fibrous material having a density of about 1100 g/m². The material is then passed through a lamtnator to melt the binder at the surface of the materia] to produce the skin. For a comparative example, Comparative Exampie 1 , a fsbrous material is prepared with the same fibers and using the same opening, blending, carding, lapping and thermobonding, without forming a skin layer on the material. Testing is performed per SAE J2883 in a small reverberant chamber, and for Example 1, the skinned side faces the source of the sound. The random incidence sound absorption coefficients are provided in Table 1.

0068Table 1.

0069<img file="WO2017192529A1_D0001.tif" /> [0065] The results of the testing are shown in the graph of Figure 5.

0070[0068] illustrative Example 2

0071[0067] A skinned fibrous composite material. Composite 1 , is prepared in the same way as the composite material of Illustrative Example 1 , having a density of 1033 g/m², a thickness of about 26.3 mm, with one skinned surface. A second skinned fibrous composite material, Composite 2, was prepared using the same fiber blend as Composite 1 , but with a density of 1335 g/m² and a thickness of about 27.4 mm. The composites are tested using a modified Indentation Force Deflection (IFD) per ASTM D3S74-17, Test B1. The test is modified so that all final deflection tests are conducted at 50% compression. Composite 1 is pre-flexed to 75-80%, whereas Composite 2 is pre-flexed to 50%. The skinned side is tested and then the composite is flipped over to test the non-skinned side. The testing of a non-skinned side is similar to or the same as a non-skinned fibrous composite material. The indenter (or presser foot) has a diameter of 1.2475 inches (3.16865 cm), and the sample size is a 6 inch (15.24 cm) by 12 inch (30.48 cm) material.

0072[0008] The results of the testing of Composite 1 and Composite 2 are shown in Figures 6 and 7, respectively. The results show a clear difference in the IFD peak stress on the skinned side as compared with the non-skinned side. This therefore shows the effect of a skin layer on the fibrous composite material. The results of the testing of Composite 1 are shown in Table 2, and the results of the testing of Composite 2 are shown in Table 3, The peak stress in Table 2 and Table 3 is at about 50 percent compression.

0073[0069] Table 2.

0074<img file="WO2017192529A1_D0002.tif" /><img file="WO2017192529A1_D0003.tif" /><img file="WO2017192529A1_D0004.tif" />

0075[0071] The compression results show an Increase in compression resistance and improved indentation resistance of a skinned fibrous material as described herein.

0076[0072] While the figures illustrate a lofted layer having a skinned surface, it is contemplated that other fibrous materials can be skinned (e.g., nonwoven materials such as a porous limp sheet), it is also contemplated that the outermost surface does not have to be skinned, instead, for example, the skinned layers can be sandwiched between other layers of the fibrous composite. It is contemplated that the material may be just partially skinned (e.g., so that the skin does not extend over the entire length/width of the surface of the nonwoven material).

0077[0073] Parts by weight as used herein refers to 100 parts by weight of the composition specifically referred to. Any numerical values recited in the above application include all values from the lower value to the upper value in increments of one unit provided thai there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 88, 43 to 51, 30 to 32, etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01, or 0.1 as appropriate. These are only examples of what is specifically intended and ail possible combinations of numerical values between the lowest value, and the highest value enumerated are to be expressly stated in this application in a similar manner. Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", inciusive of at least the specified endpoints. The term "consisting essentially of to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of the elements, ingredients, components or steps. Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps.