Acoustic article

Abstract

Embodiments of the present invention relates to an acoustic article comprising: a melt-blown microfiber, two or more polyester fibers forming a web matrix along with the melt-blown microfiber, wherein grade of a first polyester fiber is different from the grade of a second polyester fiber in the web matrix thereby creating less affinity between these fibers, and one of the two polyester fibers is a recycled polyester fiber; and a first and second scrim layer placed at opposing surface of the web matrix.

Description

ACOUSTIC ARTICLETechnical Field

[0001] The present invention relates to an acoustic article for acoustic insulation. The acoustic articles are provided for reducing noise and automotive and aerospace applications.Background

[0002] Noise, vibration, and hardness (NVH) is one of the most in-demand fields in the automobile world. In today’s world, the NVH departments of automobile companies are mainly focusing on performance, weight, and cost. Research and development are actively finding new ways of testing and evaluating noise levels and predicting the noise path for effective noise treatments. Implementing improvements using conventional technologies tends to increase vehicle weight and therefore reduce fuel economy. There are light weight solutions available, however they come with their own disadvantages such as cost, and manufacturing complexities. Further it is also technically challenging to develop these solutions because measures taken to reduce weight often degrade the performance of the articles in various areas. Therefore, the need of acoustic materials along the noise path becomes very crucial for treatment and extensive assessments have been performed towards optimizing materials for their effective placement to suit performance, weight, and cost.

[0003] Sound absorbing materials or acoustic absorbers play a vital role in the field of automotive NVH and is effectively used inside the vehicle for cabin noise improvement. These materials form a significant portion of the total sound package of any typical vehicle. Sound absorbing materials available in the market can be classified as absorbers which treat noise by absorbing it. Porous sound absorbing materials have evolved into more advanced materials over the years. They are safer, lighter, and more technologically advanced when compared to the other materials. The typical materials used as absorbers are felts, shoddy, polyurethane foam and blown microfiber based (BMF) nonwoven. These materials basically treat the noise by absorbing it across the desired frequency spectrum.

[0004] Blown microfiber (BMF) based non-woven is more technologically advanced and is known for excellent sound absorption property especially at high frequencies. The fine fibers produced using the melt- blown process and combining with the coarse fibers makes it a stable and light -weighted product which can be used for automotive NVH applications.

[0005] Also, with the introduction of electric vehicle (EV) or hybrid-electric vehicle (HEV) new types of noise sources has been introduced, especially from the electric motor, road noise, wind noise and ancillary system noise etc. The automotive industry is focusing more on science for climate and science for circular thereby more emphasis on acoustic materials that has significant attributes on sustainability and green chemistry. This has resulted towards the need for having advanced materials with multi-functional attributes to address challenging needs of present and emerging automotive NVH requirements.

[0006] The acoustic or acoustic articles are subjected to compression during transport or during molding processes. During transport, the acoustic article may need to be compressed and rolled into a roll form so that it can be transported conveniently. In a molding process, the acoustic or acoustic article is combinedwith other layers that may have multi-layered construction and thus subjected to compression. The multilayered construction used can vary based on applications and multi-functional performance requirements. When acoustic article is subjected to compression, its thickness is reduced and when compression forces are relieved the article may not be able to regain same shape and form as before compression as in the case for a blown microfiber (BMF) based absorber. More specifically, the loft or z-direction thickness of the article may not be regained. The acoustic article’s ability to absorb sound increases with mass and its natural thickness or loft. For automotive vehicles, the acoustic article should fill the spaces and any voids of the automotive parts of the vehicle after its installation, for effective noise insulation. Sometimes the acoustic articles need to be compressed for installing into the target position in the vehicle part and thereafter need to recover from compression to fill the voids and spaces in the vehicle part.

[0007] Therefore, there is a need to provide an improved acoustic article that shows good sound absorption property and flexible to conform to the structures of the automotive part. Further, the acoustic article should ideally be compressible and able to quickly recover from the compression and deliver high acoustic performance through improved sound absorption properties. Also aligning to the emerging needs of the automotive industry focusing on science for climate and science for circular, there is a need to provide and incorporate sustainability approach in designing improved acoustic materials.Summary

[0008] Accordingly, the present invention provides an acoustic article comprising: a melt-blown microfiber, two or more polyester fibers forming a web matrix along with the melt-blown microfiber, wherein grade of a first polyester fiber is different from the grade of a second polyester fiber in the web matrix thereby creating less affinity between these fibers, and one of the two polyester fibers is a recycled polyester fiber; and a first and second scrim layer placed on opposing surfaces of the web matrix.

[0009] In further exemplary embodiments, the acoustic article having melt-blown microfiber comprises polypropylene, and weight ratio of a first polyester fiber to a second polyester fiber in the web matrix comprising the melt-blown microfiber is 1:2, wherein the weight percentage of the melt-blown fiber is not more than 53% in the web matrix.Brief Description of Drawings

[0010] The accompanying drawings, which are incorporated herein and constitute a part of this disclosure, illustrate exemplary embodiments of the present disclosure like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure and thus drawings should be considered illustrative. Also, the embodiments shown in the figures are not to be construed as limiting the disclosure, but the possible variants of present disclosure are illustrated herein to highlight the advantages.

[0011] FIG. 1 shows a cross-sectional view of the acoustic article, in accordance to an embodiment of the present invention.

[0012] FIG. 2 shows an acoustic article with a barrier layer or article, in accordance to an embodiment of the present invention.

[0013] FIG. 3 shows an acoustic article with a barrier layer or article on both sides, in accordance to an embodiment of the present invention.

[0014] FIG. 4 shows an exemplary illustration of an acoustic article according to another embodiment.

[0015] FIG. 5 shows an acoustic article according to yet another embodiment.

[0016] FIG. 6 shows a method of manufacture of an acoustic article of present invention according to an embodiment.

[0017] FIGs. 7 and 8 show the Sound absorption coefficient of the acoustic article from 200 Hz to 5000 Hz tested for Sample A and Sample B respectively.

[0018] FIGs. 9 and 10 show the Sound absorption coefficient (SAC) of Sample A and Sample B acoustic articles from 200 Hz to 5000 Hz respectively.

[0019] FIG. 11 shows the Scanning Electron Microscopy (SEM) image of the acoustic article for Sample A and Sample B.

[0020] FIG. 12 shows the Optical Microscopy image of the acoustic article for Sample A and Sample B.

[0021] FIG. 13 shows the loft retention test under static load condition results of the acoustic article compared with a standard melt blown based absorber having only one grade of polyester fiber.

[0022] Fig. 14 shows sound absorption coefficient of the acoustic article Sample B with additional nonwoven porous layer from 200 Hz to 5000 Hz tested with the noise facing the acoustic article using Impedance Tube as per ASTM El 050 standard.Detailed Description

[0023] For the purpose of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Thus, it is to be understood that this invention is not limited to particularly exemplified systems or embodiments that may, of course, vary. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] As used herein, the singular form "a" "an" and "the" include plural references unless the context clearly dictates otherwise. The term "and / or" mean one or all of the listed elements or a combination of any two or more of the listed elements.

[0025] The term "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that the other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.

[0026] When the term "about" is used in describing a value or an endpoint of a range, the disclosure should be understood to include the specific value or end point referred to.

[0027] As used herein the terms "comprises", "comprising", "includes", "including", "containing", "characterized by", "having" or any other variation thereof, are intended to cover a non-exclusive inclusion.

[0028] The term “Melt-blown” means formed by extruding a molten material through a plurality of orifices to form filaments while contacting the filaments with air or other attenuating fluid to attenuate the filaments into fibers, and thereafter collecting a layer of the attenuated fibers.

[0029] The term “Melt-blown fibers” means fibers prepared by the melt-blown process.

[0030] “Microfiber” means a melt-blown fiber having a diameter (as determined using microscopy) of 10 pm or less; “ultrafine microfiber” means a microfiber having a diameter of two pm or less; and “submicron microfiber” means a microfiber having a diameter of one pm or less.

[0031] “Mesofiber” means a melt-blown fiber having a diameter (as determined using microscopy) of greater than 10 pm.

[0032] The term "incident sound wave" refers to a random or normal sound wave within the audible frequency range emitted from a sound source towards an acoustic article.

[0033] As used herein below, a noise source may be, but not limited to, a combustion engine, an electric vehicle, and an automotive / traction / air-bome transmission system or combination of all in case of a hybrid powertrain system.

[0034] The present invention relates to an acoustic article which is used for noise control treatment applications. It functions to control noise through the principal of noise absorption. Effective noise control is received through delivering higher sound absorption across desired frequency range. This is achieved through using a non-woven web-matrix having a blend of microfibers / fme fibers and macros fibers / coarse fibers.

[0035] As shown in FIG. 1, an acoustic article 100 that comprises a melt-blown microfiber 102 and two or more polyester fibers 104 and 106 in combination to form a web matrix 108 which is a non-woven web matrix. The melt-blown fiber 102 may be composed of polypropylene in an embodiment. Some examples of fiber forming materials that may be suitable for melt-blown fiber include, thermoplastic polymers such as polycarbonates, polyesters, polyamides (e.g. nylon), polyurethanes, block copolymers such as styrene- butadiene-styrene and styrene-isoprene-styrene block copolymers, and polyolefins such as polypropylene, polybutylene, and poly(4-methyl-l -pentene), polyphenylene oxide, acrylic polymers, polyvinylchloride or a combination thereof. Melt-blown fibers are those that are prepared by a melt-blowing process, e.g. by extruding a fiber-forming material through a die orifice into a gaseous stream as described in, for example, U.S. Pat. No. 4,215,682 to Kubik et al. Typically, melt-blown fibers are very long in comparison to staple fibers. Unlike polyester or staple fibers, which typically have a specific or identifiable length, melt-blown fibers typically have an indeterminate length. Although melt-blown fibers have sometimes been reported to be discontinuous, the fibers generally are long and entangled sufficiently that it is usually not possible to remove one complete melt-blown fiber from a mass of such fibers or to trace one melt-blown fiber from beginning to end. In addition, the diameter of a solidified melt-blown fiber may differ significantly from (e.g., be much smaller than) the size of a source orifice from which the molten fiber precursor was produced. In an embodiment, the weight percentage of the melt-blown fiber 102 may be more than 50% in the web matrix 108. In another exemplary embodiment, the weight percentage of the melt-blown fibermay be 53% in the web matrix 108. In yet another exemplary embodiment, the weight percentage of the melt-blown fiber is not more than 53% in the web matrix 108.

[0036] In the web matrix 108, a grade of a first polyester fiber 104 may be different from the grade of a second polyester fiber 106. The difference in grades helps to create less affinity or less merging between two types of polyester fibers. This configuration of the web matrix 108 wherein different grades of polyester fibers is selected, helps to create higher loft retention property in the web matrix 108. In other words, the web matrix 108 may comprise 2 or more different grades of polyester staple fibers in which one of the grades is recycled polyester staple fiber. Usage of one grade of virgin polyester staple fibers and blending it with melt-blown (MB) virgin polypropylene fibers in a blown microfiber (BMF) process is known in the art. In another embodiments, there may be more than two polyester fibers in the web matrix, and they can be of different grades to maintain the affinity between polyester fibers. Moreover, if there are more than two polyester fibers present in the web matrix there may be more than one type of polyester fiber with same grades, or multiple types and grades of polyester fibers, and various combinations thereof. In a conventional or typical situation, a non-woven made out of a blown micro fiber (BMF) process have a blend or combination of melt blown fine fiber and coarse or macro fiber made out of polyester staple fiber, the web matrix thus formed in such a situation has only one grade of coarse or macro polyester staple. In an embodiment, one or more polyester fibers in the web matrix 108 may be a recycled polyester fiber. For example, the second polyester fiber 106 may be a recycled polyester fiber. The recycled polyester fiber may include, but not limited to, polyethylene terephthalate (PET), Polybutylene terephthalate (PBT), polyactide (PLA) or thermoplastic polyester, polyhydroxybutyrate (PHB) and polytrimethylene terephthalate (PTT), polycyclohexylenedimethylene terephthalate and blends and copolymers thereof. The polyester may be an aliphatic polyester, aromatic polyester or a combination thereof. In an exemplary embodiment, if any of the polyester fiber in the web matrix 108 is a recycled polyester fiber then it is approximately 14% of weight composition of the web matrix 108. In another exemplary embodiment, the weight ratio of a first polyester fiber to a second polyester fiber in the web matrix 108 comprising the melt- blown microfiber is 1:2 respectively, wherein the first polyester fiber (e.g. the first polyester fiber 104) is a recycled polyester fiber.

[0037] In an embodiment, one of the first polyester fiber and the second polyester fiber may be a staple fiber. For example, the first polyester fiber 104 may be a staple fiber. In another embodiment, one of the polyester fibers may be a multi-lobal polyester staple fiber (MLPS). Multi-lobal fiber(s) refers to fibers or filaments having more than one critical point along the outer surface of the fiber. A critical point is defined as being a change in the absolute value of the slope of a line drawn perpendicular to the surface of the fiber when the fiber is cut perpendicular to the surface of the fiber axis. Multi lobal fibers do not have round cross-sections. Multi-lobal fibers can include fibers with triangular, square, tri-lobal, tetra lobal, penta- lobal and hexa-lobal or more cross-sections. The multi-lobal fibers can be continuous or discontinuous and have a variety of fibers having a variety of cross-section shapes and a variety of deniers per filament. Staple fibers are typically added to a nonwoven web in solidified form as opposed to being melt-blown into the web matrix 108. Regardless of their process of manufacture or composition, staple fibers are typicallymachine cut to a specific predetermined or identifiable length. The staple fibers are typically synthetic polymeric materials. Their composition may be chosen so that they can be melt-bonded to each other and / or to the melt-blown fibers during a typical molding process (such as used to form a shaped respirator body). Or, they can be made of materials with properties (e.g. melting point) such that they do not bond to each other or to the melt-blown fibers during a typical molding process. With respect to staple fibers used herein, the term “thermally bondable” will be generally used to designate staple fibers that have one or more components capable of some degree of melt-bonding to each other or to melt-blown fibers. In an instance, some low melt grade polyester fibers used may act as binder to bond the staple fibers together and may give a three-dimensional shape or stiffness to the fiber matrix. The term “thermally nonbondable” will be generally used to designate staple fibers that do not have any components that are capable of a significant degree of melt-bonding to each other or to the melt-blown fibers used. The staple fibers may be single component fibers or multi-component fibers. The staple fibers may be multi-component fibers, where at least one of the components will soften during heating to allow the staple fibers to be bonded to each other, or to allow the staple fibers to be bonded to melt-blown fibers. The different components may be different types of polymers (e.g. polyester and polypropylene), or may be the same type of polymer but with different melting points. The multi-component fibers may be bicomponent fibers that have a coextensive side-by- side configuration, a coextensive concentric sheath-core configuration, or a coextensive elliptical sheathcore configuration.

[0038] The polyester fiber may have various cross-sectional shapes that be regular or irregular, such as, but not limited to, circular, oval, rectangular, square, hexagon, polygon, octagonal, triangular, or any combination thereof. The polyester fiber may be crimped, substantially straight, twisted, helical, or a combination thereof. Crimped fibers may have a continuous wavy, curly, or jagged profile along their length. Crimping is a process to force the fibers to fold like an accordion. Crimps are introduced to give cohesion to the fiber assembly. This process helps the fibers to hold together during the later manufacturing stages. The polyester fibers may comprise crimped fibers that have about 2 to 6 crimps per cm. In an embodiment, the crimped fibers in the polyester fibers may be 2.18 - 3.5 crimps per cm. The configuration of the polyester fiber may vary based on different parameters. In an embodiment, one of the polyester fibers may be in the denier range of 3D -12D. The denier range of one or more polyester fiber may be in the range of 4D to 7D according to another embodiment. However, the length of the polyester fiber in the web matrix 108 varies in different embodiments. The staple length of a polyester fiber may be about 32 mm to 102 mm. In an embodiment, the length of the polyester fiber in the web matrix 108 may be about 51mm to 76mm. The strength of polyester fiber may also vary, and it determines the ability of fiber to resist stretching or breaking when subjected to tension or stress. The tenacity of the polyester fibers may be about 2 to 7 grams per denier (GPD). In an embodiment, the tenacity of the polyester fibers in the web matrix 108 may be about 2.8 to 4.5 grams per denier (GPD). The weight ratio of the first polyester fiber and the second polyester fiber in the web matrix 108 may be 1:2.

[0039] The web matrix 108 is provided with scrim layers on its opposing sides so that it is sandwiched between the scrim layers. More specifically, a first scrim layer 110 and a second scrim layer 112 may bepresent with the web matrix 108 positioned in between as illustrated in FIG. 1. In other words, the first and second scrim layers 110 and 112 in the form of a sheet or layer are positioned on both sides of the web matrix 108. The first and second scrim layers 110 and 112 may be made of polyethylene terephthalate and polypropylene respectively. The function of the scrim is to protect the fibers within the web matrix 108. The scrim is selected to deliver stability to the article 100. The scrim acts as an interfacing layer during the 3D / 2D molding process for bonding with other layers of acoustic materials forming multi-layered acoustic article. It is desired to have no usage of any additional bonding layer between the acoustic article and other subsequent acoustic layers to maintain the desired acoustic performance. In an embodiment, the flexibility with having polyester scrim one side and polypropylene scrim on the other side of the acoustic article, helps to bond securely with other acoustic layers of similar polymer family either polyester or polypropylene. Further the bonding in such situation happens based on using heat and pressure during 3D / 2D molding process without using any additional bonding agents. The weight of the scrim is selected based on the application requirement and may be about 10 to 100 grams per square meter (GSM). In an embodiment, the weight of the scrim on either side of the web matrix is about 10 to 25 grams per square meter (GSM).

[0040] The acoustic article 100 may be combined with other layers or articles such as an impervious article or a barrier article or porous article to be used as a multi-layered acoustic insulation article. FIG. 2 illustrates the acoustic article 100 with a barrier layer or article 200 to form an article 202. The barrier layer 200 is placed adjacent to a side 204 of the acoustic article 100. The barrier layer 200 impedes transmission of a sound wave by reflecting the sound wave. The barrier layer 200 may be a homogenous, flexible, thermal and acoustic reflective barrier formed using a combination of polymeric resins and inorganic fillers. In one embodiment of the invention, the barrier layer 200 may comprise a polymer such as, for example, ethylene propylene diene M-class rubber (EPDM), ethylene vinyl acetate (EVA), or olefin-based polymers filled with particles having a density higher than the polymer. Suitable filler particles may include any of the materials described above as suitable acoustic barrier materials. Examples of preferred filler particles include calcium carbonate, barium sulfate, and other mineral -based particles with a density greater than about 1 g / cm3. The barrier layer 200 may be formed on heat treatment of at least one of polymeric resins and inorganic fillers placed on a porous layer. In an embodiment the barrier layer 200 may be bonded to the acoustic article 100. As used herein, the term “bonded” includes chemical and mechanical means for acoustically coupling (that is, joining and securing) the barrier article to the acoustic article known in the art.

[0041] In another embodiment, an article 300 comprises the acoustic article 100 positioned on both sides 302 and 304 of the barrier layer 200 as illustrated in FIG. 3. The acoustic article 100 positioned on both sides of the barrier layer 200 may have different thickness in an embodiment. The article 300 may be used in an application that needs to absorb sound incident from both sides of this article and the barrier layer 200 reflects these sound waves. In another embodiment, the acoustic article 100 positioned on both sides 302 and 304 may have same thickness depending on the application needs.

[0042] FIG. 4 is an exemplary illustration of an article 400 according to another embodiment. The acoustic article 400 have a porous layer 402 on one side 404 and a barrier layer (for example, the barrier layer 200) on top of the porous layer 402 to form the article 400. Useful porous layers include, but are not limited to, non-woven fibrous layers, perforated films, particulate beds, and open-celled structures such as open-celled foams, fiberglass, nets, woven fabrics, and combinations thereof. Porous layers are generally permeable, enabling air or some other fluid to freely communicate between opposite sides of the layer. Such layers may also be semi-permeable (permeable along some but not all of the thickness dimension) or impermeable. Non-woven layers can be made from a wide variety of materials, including organic and inorganic materials. If the porous layer is a non-woven fibrous matrix then it acts as an acoustic absorber and includes a plurality of fibers characterized by entanglement or point bonding of the fibers to form a sheet or mat exhibiting a structure of individual fibers filaments which are interlaid, but not in an identifiable manner as in a knitted fabric. The porous layer 402 may be made of, but not limited to, at least one fiber forming polymer. The at least one fiber forming polymer may be, but not limited to, Nylon6, Nylon 66, cotton, polyester, polypropylene and polyolefin-based fiber (such as polypropylene and polyethylene, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyurethane, polybutene, polylactic acid, polyphenylene sulfide, polysulfone, liquid crystalline polymer, polyethylene- co-vinylacetate, polyacrylonitrile, cyclic polyolefin, and copolymers and blends thereof) and shoddy (for example, fabric scraps or shredded rags). The porous layer 402 may be made of multiple fibers having different denier in the range about 2D to 20D. The fibers having different deniers help in achieving the loft retention characteristics of the article 400.

[0043] The porous layer 402 may be bonded to the acoustic article 100 according to an exemplary embodiment. As used herein, the term “bonded” includes chemical and mechanical means for acoustically coupling (that is, joining and securing) the barrier material to the acoustic article 100 known in the art. In an embodiment, a barrier layer for example the barrier layer 200 may be formed over a porous layer (for example, the porous layer 402). The barrier layer 200 may be a homogenous, flexible, thermal and acoustic reflective barrier formed using a combination of polymeric resins and inorganic fillers according to an embodiment. In another embodiment, the barrier layer 200 may be formed by heat treating the at least one of polymeric resins and inorganic fillers placed on the porous layer 402 thereby the porous layer 402 and barrier layer 200 is a single unit or article and are not separate layers bonded to each other.

[0044] FIG. 5 illustrates an acoustic article 500 according to yet another embodiment. The article 500 includes a porous layer (such as the porous layer 402) positioned over the acoustic article 100. The porous layer 402 is already explained in conjunction with FIG. 4. The porous layer 402 may be bonded to the acoustic article 100 using the methodologies known in the art.

[0045] Now referring back to the obtained acoustic article 100, this article is light in weight may be about 180 - 1000 GSM and has superior acoustic performance having a very high sound absorption properties in the entire frequency spectrum from 200Hz to 5000Hz. This light weighted acoustic article has a simplified construction that functions to maximize the overall sound pressure level reduction and enhance the overallsound quality levels for the application. The acoustic article has superior thermal insulation and thermal management properties.

[0046] Furthermore, the acoustic article is suitable for acoustic applications in high temperature prone areas typically in a firewall application of an automobile. The article is also suitable for applications that need to have acoustic materials near to the noise source typically in a firewall of an automobile. The article can take complex shapes and design achieved through compression molding suitable for various applications such as in automobile dash application and meets a flammability standard Federal Motor Vehicles Standard Safety (FMVSS302). Moreover, the acoustic article can be subjected to compression molding to obtain the desired complex shape that is needed for a particular application using compression plates. It is desirable to attain a shape that can conform to a profile or shape of a surface separating the vehicle cabin from engine compartment. Other moldable applications include electric-motor wraps and engine encapsulations.

[0047] The acoustic article (for example, the acoustic article 100) has excellent overall sound absorption coefficient (200 Hz ~ 5000 Hz) using impedance tube as per ASTM E1050 standard tested for Sample A comprising of around 280 GSM with 30mm thickness, (200 Hz: 7% absorption; 500 Hz: 16% absorption; 1000 Hz: 40% absorption; 2000 Hz: 80% absorption; 4000 Hz: 84% absorption; 5000 Hz: 76% absorption). Further the acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient using impedance tube as per ASTM E1050 standard tested for Sample B comprising of around 380 GSM with 38mm thickness. (200 Hz: 8% absorption; 500 Hz: 28% absorption; 1000 Hz: 81% absorption; 2000 Hz: 97% absorption; 4000 Hz: 94% absorption; 5000 Hz: 99% absorption).

[0048] The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient using Reverberation Chamber as per ASTM C423 standard tested for Sample A comprising of around 280 GSM with 30mm thickness, (200 Hz: 25% absorption; 500 Hz: 45% absorption; 1000 Hz: 67% absorption; 2000 Hz: 77% absorption; 4000 Hz: 72% absorption; 5000 Hz: 72% absorption). Further the acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient using Reverberation Chamber as per ASTM C423 standard tested for Sample B comprising of around 380 GSM with 38mm thickness, (200 Hz: 18% absorption; 500 Hz: 70% absorption; 1000 Hz: 100% absorption; 2000 Hz: 96% absorption; 4000 Hz: 83% absorption; 5000 Hz: 83% absorption).

[0049] Further the acoustic article has the presence of melt-blown microfiber and staple polyester fiber in the web matrix. The melt-blown microfiber and the staple polyester fibers are uniformly distributed across the web matrix. The melt-blown microfiber are fine fibers and has a fiber diameter of around 1 pm to 6 pm, while the staple polyester fibers have fiber diameter around 27 pm to 40 pm as observed using Scanning Electron Microscopy (SEM). Further using optical microscope, the presence of black recycled polyester staple fibers along with melt-blown microfiber and the other grade of staple polyester fiber in the web matrix is observed.

[0050] In addition, the acoustic article has good air flow resistance measured as per ASTM C522 standard tested for Sample A comprising of around 280 GSM with 30mm thickness, (380 mks rayls). The acousticarticle has good air flow resistance measured as per ASTM C522 standard tested for Sample B comprising of around 380 GSM with 38mm thickness, (1200 mks rayls).

[0051] Additionally, the acoustic article has excellent loft retention test properties measured under static load condition. When the acoustic article is applied with a static load of 2 kg to the sample size of 30 cm x 30 cm kept under load condition for 7 days, leading to around 40% thickness compression to its original thickness (30 mm), the rebound of thickness (loft gain) immediately after removal of load was about 86.6% of the original thickness for the acoustic article after 7 days. Further after 3 days of observation the thickness gained to 90% of the original thickness. The loft retention property of the acoustic article will help to maintain the sound absorption properties post molding conditions. The higher loft retention property of the acoustic article is due to the incorporation of two different grades of polyester fiber in the web matrix.

[0052] In an embodiment, the acoustic article (for example, the acoustic article 100) is placed in a vehicle cabin or engine compartment. The article is placed in such a way that its surface may touch the body in white surface (biw) or sheet metal. In other situation the acoustic article may touch the body in trim (bit) of the vehicle. Similarly, the acoustic article can be placed in the engine / motor compartment such that its surface touches the body in white of the sheet metal of the vehicle. In other situations, the acoustic article may also be used as wrap insulation or to encapsulate the electric motor of the vehicle. Similarly, the acoustic article may be combined with an impervious layer or barrier materials or porous material to be used as an multi-layered acoustic insulation across vehicle engine compartment (firewall, bonnet etc.) or the cabin compartment (such as, front of dash, floor, headliner, etc). Some of these combinations are already explained in conjunction with FIGs. 2, 3, 4 and 5. Such multi-layered combination comprising of the acoustic article can also be placed on the base of the driver and pillion compartment such that the porous layer touches the sheet metal or base of the vehicle front and rear floor, and the impervious layer or barrier layer faces the cabin of the vehicle. The acoustic article can be used in many applications including, automotive, aerospace, marine, locomotives, building acoustics including concrete slab insulation, appliances, and other potential product application requiring acoustic properties. Further the acoustic article can also be used to form a multi-layered acoustic insulation using combination of an impervious layer or barrier layer or non-woven porous layer.

[0053] Further the acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient using impedance tube as per ASTM El 050 standard tested for Sample B facing the noise source combined with additional non-woven porous layer. (200 Hz: 29% absorption; 500 Hz: 67% absorption; 1000 Hz: 100% absorption; 2000 Hz: 88% absorption; 4000 Hz: 91% absorption; 5000 Hz: 87% absorption). The acoustic article used here was Sample B comprising of 380GSM with 38mm thickness combined with an additional non-woven porous layer comprising of 800GSM with 30mm thickness.Method of Manufacture

[0054] The acoustic article (for example, the acoustic article 100) of present invention also may be formed using a process as shown in FIG. 6. The method initiates with feeding polyester fibers through a feeding unit 600. The polyester fibers from feeding unit 600 goes through a carding process in a carding unit 602. In the carding process, the fibers are converted to uniform strands of fibers and they are made parallel toeach other by removing the neps. This process is done also to remove maximum impurities in the fibers for cleaning them and to achieve proper mixing of the polyester fibers. After carding, the fibers may be fed into a cross-lapping unit 604 where the fibers are arranged vertically and horizontally many times to form a web of cross-laid fibers. These cross-lapped fibers are blown by a fiber blowing unit 606 onto a conveyor belt 608. The fibers may be a mix of two or more polyester fibers (610 and 612) as shown in the FIG. 6. On the conveyor belt 608 a scrim layer 614 is laid on which the polyester fibers fall on. The scrim layer 614 is unwound to from a scrim layer roll 616. As shown in FIG. 6, there is a melt-blown unit 618 having a hopper of an extruder 620 that receives a polymer material that is melted due to heat and friction and the mechanical actions of moving parts within the extruder 620. The melted polymer materials are compressed and homogenized. The high-pressure molten polymer material may flow into a metering pump (now shown in FIG. 6) for uniform delivery of the material into a die assembly 622. The die assembly 622 includes a die 624 that allows the melted polymer material to flow through its channel . The die 624 may have a tapered structure. The melted polymer material reaches the nosepiece of the die 624. The nosepiece is wide, hollow and tapered having orifices or holes that allow the melted polymer to be extruded through these holes to form filament strands which are attenuated by hot air to form fine microfibers. The melt-blown fibers formed are laid over the polyester fibers on the conveyor belt 608. Now there is a mix of melt-blown fiber and polyester fibers on the bottom scrim layer 614. Towards the end of conveyor belt 608, another scrim layer 626 may be laid on the top of the layer of melt-blown fiber and polyester fibers. The scrim layer 626 is unwound from a scrim layer roll 628. The acoustic article 100 formed is taken from the conveyor belt 608 and may be rolled into a roll 630.

[0055] To establish the NVH performance improvements, thermal properties and loft retention properties of the acoustic article, the following tests were carried out:

[0056] Sound absorption coefficient (SAC) — Noise measurements using Impedance Tube as per ASTM El 050 Standard (Normal Incidence)

[0057] FIGs. 7 & 8 show the Sound absorption coefficient of the acoustic article from 200 Hz to 5000 Hz tested for Sample A and Sample B respectively. The acoustic article used here was Sample A comprising of 280 GSM with 30mm thickness and Sample B comprising of 380GSM with 38mm thickness.Key Observations: a) The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient tested for Sample A. (200 Hz: 7% absorption; 500 Hz: 16% absorption; 1000 Hz: 40% absorption; 2000 Hz: 80% absorption; 4000 Hz: 84% absorption; 5000 Hz: 76% absorption) b) The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient tested for Sample B. (200 Hz: 8% absorption; 500 Hz: 28% absorption; 1000 Hz: 81% absorption; 2000 Hz: 97% absorption; 4000 Hz: 94% absorption; 5000 Hz: 99% absorption)The SAC result is represented in Table 1.Table 1 : Sound Absorption Coefficient data

[0058] Sound absorption coefficient (SAC) — Noise measurements using Reverberation Chamber as per ASTM C423 Standard (Random Incidence)

[0059] FIGs. 9 & 10 show the Sound absorption coefficient (SAC) of the acoustic article Sample A and Sample B from 200 Hz to 5000 Hz respectively.

[0060] Sample A used here was around 280 GSM with 30 mm thickness and Sample B used here was around 380 GSM with 38 mm thickness.Key Observations: a) The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient tested for Sample A. (200 Hz: 25% absorption; 500 Hz: 45% absorption; 1000 Hz: 67% absorption; 2000 Hz: 77% absorption; 4000 Hz: 72% absorption; 5000 Hz: 72% absorption) b) The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient tested for Sample B. (200 Hz: 18% absorption; 500 Hz: 70% absorption; 1000 Hz: 100% absorption; 2000 Hz: 96% absorption; 4000 Hz: 83% absorption; 5000 Hz: 83% absorption)The SAC result is represented in Table 2.Table 2: Sound Absorption Coefficient data

[0061] Morphology analysis of the acoustic article was conducted using SEM and Optical microscopy to understand the fiber distribution and presence of fine and coarse fibers across the web matrix.

[0062] The acoustic article was subjected to Scanning Electron Microscopy (SEM) analysis and Optical microscopy analysis.

[0063] FIG. 11 shows the Scanning Electron Microscopy (SEM) image of the acoustic article for Sample A around 280 GSM with 30mm thickness and Sample B around 380 GSM with 38mm thickness. The SEM image clearly shows the presence of melt-blown microfiber and staple polyester fiber. The melt-blown microfiber and the staple polyester fibers are uniformly distributed across the web matrix. The melt-blown microfiber are fine fibers and has a fiber diameter of around 1 pm to 6 pm, while the staple polyester fibers have fiber diameter around 27 pm to 40 pm.

[0064] FIG. 12 shows the Optical Microscopy image of the acoustic article for Sample A around 280 GSM with 30mm thickness and Sample B around 380 GSM with 38mm thickness. The optical imageshows the presence of black recycled polyester staple fibers along with melt-blown microfiber and the other grade of staple polyester fiber in the web matrix.

[0065] Flammability Resistance as per FMVSS302 StandardTest Procedure:

[0066] The test is conducted inside a test chamber where the test specimen is mounted horizontally. The exposed side of the test specimen is subjected to a gas flame from underneath. The burnt distance and the time taken to bum this distance is measured during the test. The result, the burning rate, is expressed in mm / min.

[0067] The acoustic article was found passing the Horizontal Flammability standard as per FMVSS 302 and is represented in Table 3. The acoustic article used here was Sample A around 280 GSM with 30 mm thickness and Sample B around 380 GSM with 38 mm thickness.Table 3: Flammability Test Results

[0068] Thermal Conductivity as per ASTM C518 Standard (Average Temp: 22,5 degree Celsius)

[0069] Thermal Conductivity of the acoustic article was tested at 22.5°C. The acoustic article sample shows a thermal conductivity of 0.032 W / mK for Sample A and 0.031 W / mK for Sample B. The acoustic article used here was Sample A around 280 GSM with 30 mm thickness and Sample B around 380 GSM with 38 mm thickness.

[0070] Hot Odor as per SAE J1351Test Procedure:

[0071] Test specimens were representative of the material or composite being evaluated. Test specimens had a surface area (including all surfaces) of 250 cm2± 25 cm2(0.28 ft2± 0.028 ft2). Test specimens were cut to any dimension compatible to the dimensions of the jar, provided the specimen surface area is maintained at 250 cm2.

[0072] Prior to the test, the specimens were conditioned for 24 hours at 23°C ± 2°C (70 °F ± 2 °F) and 50% RH ± 5% RH.Samples were tested dry and in the presence of moisture. For the dry test, a test specimen was placed in a jar and covered with the lid and ring. For the wet test, 2 cc of distilled water was put directly on the specimen after the specimen has been placed in the jar and cover with the lid and ring. One empty jar was included for control use purposes closed with a lid and ring.

[0073] Jars were placed in an oven preheated to 65°C ± 3°C (149°F ± 5°F) for 1 hour (±5 minutes). This temperature was selected to be representative of automotive applications.

[0074] The jars were removed after one hour of oven heating time. A first panelist positioned his head near the control jar (approximately 15 cm away) and removed the lid. Then, with a cupped hand, the firstpanelist drew the air from the jar to their nose and slowly inhaled. The first panelist immediately repeated the procedure for the first test specimen (dry) and recorded the appropriate rating (as odor scale listed in below). Lids were removed from the jars longer for not longer than 5 seconds. Tests were conducted in an environment free from drafts and contaminant odors. Results of the testing are represented in Table 4. Sample A used here was around 280 GSM with 30 mm thickness and Sample B used here was around 380 GSM with 38 mm thickness.ODOR SCALE -Rating Description1 No noticeable odor2 Slight, but noticeable odor3 Definite odor, but not strong enough to be offensive4 Strong offensive odor5 Very strong offensive odorTable 4 Hot Odor Test ResultsThe acoustic article does not exhibit any objectionable odor.

[0075] Air Flow Resistance as per ASTM C-522

[0076] Air flow resistance of the acoustic article was measured for Sample A around 280 GSM with 30 mm thickness and Sample B around 380 GSM with 38 mm thickness.Results of the testing are represented in Table 5.Table 5: Air Flow Resistance mks rayl

[0077] Loft Retention Test under static load condition

[0078] FIG. 13 shows the loft retention test under static load condition results of the acoustic article- compared with a standard melt blown based absorber having only one grade of polyester fiber. The acoustic article used here was Sample A around 280 GSM with 30 mm thickness and comparative Sample B around 240GSM with 23mm thickness. The static load considered here was 2 kg for a sample size of 30 cm x 30 cm. The initial thickness was measured for the acoustic article Sample A and comparative Sample B. The static load of 2 kg was applied to the sample size of 30 cm x 30 cm and was kept under load condition for 7 days. The thickness under load was measured. After seven days the load was removed, and the thicknessregained was measured. Further the sample was kept at normal condition without any load for 3 days and the thickness regained was measured.Key Observations: a) The acoustic article Sample A exhibits excellent loft retention properties after static load conditions compared to the comparative Sample B. b) The loft retention property of the acoustic article will help to maintain the sound absorption properties post molding conditions. c) The higher loft retention property of the acoustic article sample A is due to the incorporation of two different grades of polyester fiber as compared to the Sample B of standard melt-blown absorber having only one grade of polyester fiber.The Loft retention performance details is shown in Table 6

[0079] Tensile Strength measurement

[0080] Tensile strength evaluation was done for the acoustic article comprising of Sample A around 280 GSM with 30 mm thickness and Sample B around 380 GSM with 38 mm thickness measured across both at machine direction (MD) and cross direction (CD) for a sample size of 250mm x 50mm and with a pull speed of 200mm / min.The result of the tensile strength of Sample A and Sample B is shown in Table 7.Table 7: Tensile strength measurement of acoustic article

[0081] Sound absorption coefficient (SAC) — Noise measurements using Impedance Tube as per ASTM El 050 Standard (Normal Incidence)

[0082] FIG. 14 shows sound absorption coefficient of the acoustic article Sample B with additional nonwoven porous layer from 200 Hz to 5000 Hz tested with the noise facing the acoustic article using Impedance Tube as per ASTM E1050 standard. The acoustic article used here was Sample B comprising of 380GSM with 38mm thickness combined with an additional non-woven porous layer comprising of 800GSM with 30mm thickness.Key Observations: a) The acoustic article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient tested for Sample B combined with additional non-woven porous layer. (200 Hz: 29% absorption; 500 Hz: 67% absorption; 1000 Hz: 100% absorption; 2000 Hz: 88% absorption; 4000 Hz: 91% absorption; 5000 Hz: 87% absorption)The SAC result is represented in Table 8.Table 8: Sound Absorption Coefficient data

[0083] Although, the present invention has been described in considerable detail with reference to certain preferred embodiments and examples thereof, other embodiments and equivalents are possible. Even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with functional and procedural details, the disclosure is illustrative only, and changes may be made in detail, within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms. Thus, various modifications are possible of the presently disclosed system and process without deviating from the intended scope and spirit of the present disclosure. Accordingly, in one embodiment, such modifications of the presently explained disclosure are included in the scope of the present disclosure.

Claims

What is claimed is:

1. An acoustic article, the article comprising: a melt-blown microfiber; two or more polyester fibers forming a web matrix along with the melt-blown microfiber, wherein grade of a first polyester fiber is different from the grade of a second polyester fiber in the web matrix thereby creating less affinity between these fibers, and wherein at least one of the two polyester fibers is a recycled polyester fiber; and a first and a second scrim layer placed at opposing surfaces of the web matrix.

2. The article as claimed in claim 1, wherein the melt-blown microfiber is polypropylene.

3. The article as claimed in claim 1 , wherein weight ratio of a first polyester fiber to a second polyester fiber in the web matrix is 1:2.

4. The article as claimed in claim 1, wherein at least one of the polyester fibers is a multilobal polyester staple fiber (MLPS).

5. The article as claimed in claim 1, wherein the weight percentage of melt-blown microfiber is not more than 53% in the web matrix.

6. The article as claimed in claim 1, wherein denier range of a polyester fiber is about 3D - 12D.

7. The article as claimed in claim 1, wherein denier range of a polyester fiber is about 4D to 7D.

8. The article as claimed in claim 1, wherein the staple length of a polyester fiber is about 51 - 76 mm.

9. The article as claimed in claim 1, wherein tenacity of the one or more polyester fibers is about 2.8 - 4.5 GPD (grams per denier).

10. The article as claimed in claim 1, wherein number of crimps of the one or more polyester fibers is 2.18 - 3.5 nos / cm.

11. The article as claimed in claim 1 , wherein basis weight of the acoustic article is about 180 to 1000 GSM.

12. The article as claimed in claim 1, wherein the first scrim layer is one of polyethylene terephthalate and polypropylene.

13. The article as claimed in claim 1, wherein the second scrim layer is one of polyethylene terephthalate and polypropylene.

14. The article as claimed in claim 1, having an airflow resistance of 300 -to 800 Mks Rayls for a GSM of 280.

15. The article as claimed in claim 1, having an airflow resistance of 350- to 450 Mks Rayls for a GSM of 280.

16. The article as claimed in claim 1, having an air flow resistance of 500- to 2000 Mks Rayls for a GSM of 380.

17. The article as claimed in claim 1, having an airflow resistance of 1200 - to 2000 Mks Rayls for a GSM of 380.

18. The article as claimed in claim 1, having loft retention characteristics where in the % loft retention is at least 85% compared to the original thickness when removed from a static load condition of 2kg / 900cm2 observed for a duration of 7 days.

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