Nonwoven fabric-based technical textile with improved acoustic performance and method of production thereof

Abstract

The present invention relates to an innovative production method that eliminates the need for additional components used to improve acoustic performance in wheel arch liner felts. By virtue of the method according to the present invention, splittable fibers are converted into microfibers during the carding-needling process and conveyed onto a nonwoven fabric, ensuring successful bonding of the two structures. As a result of the method according to the present invention, the resulting nonwoven fabric base comprising additional fibers exhibits superior sound absorption properties without requiring any additional components or patches.

Description

[0001] DESCRIPTION

[0002] NONWOVEN FABRIC-BASED TECHNICAL TEXTILE WITH IMPROVED ACOUSTIC PERFORMANCE AND METHOD OF PRODUCTION THEREOF

[0003] Technical Field

[0004] The present invention relates to a method for producing automotive textiles and to a product obtained thereby. More specifically, the present invention concerns a production method employing splittable fibers to enhance the acoustic property of a wheel arch liner. In accordance with the method of the present invention, in contrast to the state of the art, improvement of the acoustic property is achieved without the addition of any further components on the formed product.

[0005] Background of the Invention

[0006] In the automotive industry, the need for acoustic performance is of great importance for increasing driving comfort and reducing the noise level inside the vehicle. This need plays a vital role, particularly in ensuring quieter operation of vehicles, reducing road and tire noise, and improving the overall acoustic environment inside the vehicle. Textile materials are utilized for this purpose in various forms. One such textile material is the wheel arch liner, which is used to reduce road and tire noise. In the state of the art, wheel arch liners are also referred to as wheel arch covers, wheel outer liners, wheelhouse liners or fender liners. A wheel arch liner may be plastic-based or textile- based. Textile-based wheel arch liners are also referred to as wheel arch liner felts. Textile materials having acoustic properties reduce the noise level inside the vehicle by increasing sound insulation in the region where they are located. Such products are generally made of needle-punched nonwoven fabric materials and shaped by thermoforming. In addition to wheel arch liners, it is known that acoustic textiles are also used in floor carpets, underbody shields, door panels, interior trim, floor coverings, and mats.

[0007] In textile materials used to improve acoustic performance, the structure and density of the fibers play a significant role in sound absorption. Finer and denser fibers provide insulation by more effectively absorbing sound waves. Multilayer structures are employed in textile materials to enhance sound insulation. Layers of varying density and thickness absorb sound waves of different frequencies, thereby providing broader-range insulation. Thermoforming and extrusion coating techniques improve the mechanical and thermal properties of textile materials, thereby enabling superior acoustic performance.

[0008] In the automotive industry, four types of wheel arch liner products are commercially available, the performance of which varies depending on their price.

[0009] • The cheapest known products consist of single molded plastic parts. These products, which have no acoustic properties, are used due to their mechanical performance.

[0010] • Another product group comprises standard wheel arch liner felts incorporating acoustic patches. Such products, formed from thick needle-punched nonwoven fabrics, can be molded by thermoforming and possess optimal acoustic properties; however, their mechanical properties are insufficient.

[0011] • A further product group consists of two-layer products comprising a low basis weight needle-punched nonwoven fabric layer made from recycled synthetic and natural fibers, and a high basis weight felt. In such products, the recyclability of the final product is limited.

[0012] • Another product group is a three-layer structure comprising an extrusion coating layer as the middle layer, and needle-punched nonwoven fabrics as the front and rear layers. By incorporating acoustic-absorbing patches on the three-layer product, a higher acoustic absorption value can be achieved; however, this increases the unit cost of the product.

[0013] In the state of the art, certain patent documents have been encountered.

[0014] Chinese Patent with No. CN100404318C discloses a wheel arch liner product which is designed to reduce noise transmission and absorb noise generated by the movement of the tire on the road surface. The structure comprises at least three layers made of a breathable material.

[0015] U.S. Patent Application with Publication No. US2022144189A1 relates to providing a multilayer needle-punched nonwoven fabric having a sandwich structure for textile wheel arch liners for motor vehicles. The material used in the relevant patent comprises fibers selected from PP / PET, PP / BiCo / PET, PP / BiCo, or PET / BiCo.

[0016] European Patent Application with Publication No. EP4241979A1 concerns a laminated material comprising a nonwoven fabric containing multicomponent fibers. The layers are bonded together by melt bonding, and it is indicated that the material can also be used as a wheel arch liner.

[0017] U.S. Patent Application with Publication No. US2019308667A1 discloses a wheel arch liner product for vehicles. The product described in the relevant patent comprises at least one structural porous fibrous layer extending longitudinally in a curved form with a front end and a rear end. The porous fibrous layer includes grooves and protrusions.

[0018] With the transition to electric vehicles, the need for acoustic materials around the engine will decrease, while the need in wheel and door areas will increase. Tire and road noise, which varies with speed, road surface, and frequency, constitutes a significant portion of the overall vehicle noise. Research relating to acoustically designed wheel arch liners has demonstrated that such noise can be reduced both at its source and within the vehicle. Fiber-based wheel arch liners absorb sound at the source of tire and road noise, thereby playing an effective role in the reduction thereof.

[0019] In the state of the art, it is a common practice to attach additional parts such as patches to three-dimensionally formed wheel arch liners to improve their acoustic properties. The auxiliary parts used to enhance acoustic performance are generally felts, sponges, or foams. In addition, there are applications in which nonwoven fabric parts containing microfibers obtained by the meltblown method are used. In the manufacturing method of the state of the art, a plastic-based or textile-based wheel arch liner is first produced. Thereafter, as described above, felt, sponge, foam, or nonwoven fabric containing microfibers obtained by the meltblown method is attached to specific regions of the three-dimensional wheel arch liner product. This process requires additional equipment and labor and results in time loss. Furthermore, during the product’s service life, the durability of the patches decreases, and separations or various deformations occur in the patches.

[0020] Technical Problems Addressed by the Invention

[0021] The method of the present invention aims to eliminate the practice of attaching patches to different regions of a textile-based wheel arch liner in order to increase its acoustic performance.

[0022] The most significant advantage of the method of the present invention is the utilization of splittable fibers. In the state of the art, there are studies in which splittable fibers have been used for the purpose of sound insulation. However, in the method of the present invention, splittable fibers are used only in certain regions as required, thereby creating a distinction and superiority. Due to the cost of splittable fibers, it is not desired to use them over the entire surface. Therefore, it is of considerable importance to perform production in such a manner that they are used only in predetermined regions.

[0023] In more detail, the method of the present invention provides an advantage in that the splittable fibers can be incorporated directly into certain regions in the form of a single fabric, rather than as a patch. Normally, a nonwoven fabric production line comprises fiber feeding, opening, carding, cross-lapping, and needling units. Although the theoretical concept of introducing a different type of fiber into only a certain region in such a production line may be conceivable, it is not practically applicable.

[0024] The method of the present invention combines the two-step application known in the state of the art into a single process, thereby providing advantages in terms of time, labor, and cost.

[0025] For a better understanding of the method of the present invention, reference will be made to the figures below

[0026] Description of the Figures

[0027] Figure 1 is a flow diagram of the steps of the method of the present invention.

[0028] Figure 2 is a schematic illustration showing the laying of splittable fibers onto a nonwoven fabric base according to the method of the present invention.

[0029] Figure 3 is an illustration showing the nonwoven fabric base comprising an additional fiber area obtained in accordance with the method of the present invention.

[0030] Figure 4 is an illustration showing the layers of the extruder-coated structure obtained in accordance with the method of the present invention.

[0031] Figure 5 is an illustration showing the layers of the structure comprising a backing nonwoven fabric layer obtained in accordance with the method of the present invention. Reference Numerals for Components, Parts, and Flow Aiding in the Description of the Invention

[0032] 1- Splittable fiber tow

[0033] 2- Opening cylinder

[0034] 2a- Card wire

[0035] 3- Microfiber

[0036] 4- Nonwoven fabric base

[0037] 5- Extrusion coating

[0038] 6- Backing nonwoven fabric

[0039] Process Flow Diagram Aiding in the Description of the Invention

[0040] 100- Determining the regions on the nonwoven fabric where splittable fibers will be applied

[0041] 200- Laying splittable fibers onto the predetermined regions of the nonwoven fabric

[0042] 300- Embedding the splittable fibers onto the nonwoven fabric

[0043] Detailed Description of the Invention

[0044] The method of the present invention is aimed at eliminating the need for the use of acoustic patches in automotive wheel arch liners. In line with this primary objective, a method has been developed in which splittable fibers are fed into the system in tow form, converted into fine micro-sized fibers, and subsequently laid onto a nonwoven fabric. The most significant characteristic of the method of the present invention is that the splittable fibers intended to enhance acoustic performance are used not over the entire surface, but only in certain predetermined regions. The method of the present invention enables this by ensuring that the splittable fibers are split within the card-needling system in such a manner as to avoid any agglomeration, clogging, or similar operational issues.

[0045] Although the method of the present invention has been developed for the purpose of improving the acoustic property of wheel arch liners, various adaptations are possible. By “acoustic performance,” particularly the sound absorption property of the product is meant. It is known in the state of the art that splittable fibers have an acoustic effect. By using different types of fibers in place of splittable fibers, different properties can be imparted to the final product. The method may be utilized in the production of an automotive textile other than a wheel arch liner. At present, the enhancement of acoustic performance in wheel arch liners is achieved by reinforcing the nonwoven fabric with additional parts, which has created the need for the method of the present invention. Even in plastic wheel arch liner products, examples exist in which such additional parts are employed.

[0046] When considered as a process, the method of the present invention proceeds in a workflow as shown in Figure 1. Accordingly, the production method of the present invention generally comprises the following steps:

[0047] Determining the regions on the nonwoven fabric where splittable fibers will be applied (100)

[0048] Laying splittable fibers onto the predetermined regions of the nonwoven fabric (200)

[0049] Embedding the splittable fibers onto the nonwoven fabric (300)

[0050] An important aspect of the method of the present invention is that the splittable fibers are laid onto predetermined regions of the nonwoven fabric base (4). At this stage, partial splitting occurs in the splittable fibers, and the fiber diameter begins to decrease. Subsequently, the nonwoven fabric base (4) carrying splittable fibers in certain regions is subjected to a needling process to allow the splittable fibers to penetrate into the nonwoven fabric and to further increase the splitting of the fibers.

[0051] The nonwoven fabric base (4) may be a web which is subjected to fiber feeding, fiber opening, blending, carding, and cross-laying processes, or may be a structure which is additionally subjected to pre-needling following cross-laying. In other words, the nonwoven fabric base (4) may be a pre-needled surface or a web surface not subjected to pre-needling. The processes of fiber feeding, fiber opening, blending, carding, cross-laying, and pre-needling are carried out as known in the prior art, and thus will not be described in further detail herein.

[0052] The steps included in the method of the present invention will be described in detail below.

[0053] Determining the Regions on the Nonwoven Fabric Where Splittable Fibers Will Be Applied (100)

[0054] Different regions or patterns may be determined according to need and preference. At this stage, the region or pattern is not binding; what is important is that the process is performed on certain regions. In the next step, the fibers to be applied onto the nonwoven fabric are specialized and therefore costly fibers. Applying splittable fibers over the entire structure is not preferred as it increases cost. Laying Splittable Fibers onto the Predetermined Regions of the Nonwoven Fabric (200) At this stage, the flow of splittable fibers onto the predetermined regions on the nonwoven fabric base (4) is mechanically controlled, and the fibers are laid onto the fabric by vacuum assistance. The splittable fibers laid on the nonwoven fabric base (4) may have any desired shape or pattern.

[0055] A schematic illustration of the laying of splittable fibers onto predetermined regions according to the method of the present invention is shown in Figure 2. The surface that is illustrated in Figure 2 is a nonwoven fabric base (4) produced by carding and needling techniques. However, it should be noted that only pre-needling is performed during the production of the nonwoven fabric base (4). The nonwoven fabric base (4) processed according to the method of the present invention will subsequently undergo a further needling process. The nonwoven fabric base (4) may be made of different types of fibers, for example, PET, PP, or PET / coPET.

[0056] According to the method of the present invention, splittable fibers are transferred onto the nonwoven fabric base (4). The splittable fibers are fed into the system in tow form and opened to microfibers. The transfer of the microfibers is carried out by a high-speed horizontally positioned cylinder comprising card wires.

[0057] Splittable fibers are fed into the system in the form of a tow. The term “tow” refers to a web strip composed of splittable fibers. The splittable fiber tow (1) is fed to an opening cylinder (2) positioned horizontally. As shown in Figure 2, the opening cylinder (2) comprises card wires (2a) on its outer surface. The fiber within the tow passing over the opening cylinder (2) wrapped with carding wires (2a) tends to split during the process, which may cause clogging and agglomeration. For homogeneous and continuous operation, the selection of carding wires (2a) is important. The carding wires (2a) must be sufficiently aggressive to both split and transfer the fibers simultaneously. Therefore, carding wires (2a) having a working angle between -10° and 50°, preferably between 0° and 30°, and a density of wire points (teeth) on the card clothing surface between 75 and 325 PPSI, preferably not exceeding 250 PPSI, should be used. The working height of the wire teeth should be selected between 0.8 mm and 3.5 mm, preferably not exceeding 3 mm. The carding wires (2a) do not require any finishing; however, they may optionally be sanded or polished.

[0058] In the method of the present invention, the opening cylinder (2) rotates continuously. The flow of the tow may be intermittently stopped according to the predetermined region and pattern. Software control systems may be employed for this purpose. According to the method of the present invention, the splittable fiber tow (1) is opened and split into microfibers (3) by the carding wires (2a) on the opening cylinder (2). The microfibers (3) are conveyed onto the nonwoven fabric by vacuum assistance.

[0059] To improve acoustic insulation properties, the surface area of the fibers within the structure should be increased. For this purpose, splittable fibers such as PP / PET, PA / PET, PET / PLA fibers with or without hollow structure may be used at this stage. The splittable fibers may be used alone or blended with different fibers. For example, in one application, the splittable fibers may be blended with microfibers. In another application, the splittable fibers may be blended with conventional macrofibers.

[0060] At this stage, by using different types of fibers, properties other than acoustic performance can be enhanced, thereby obtaining functional products. For example, a nonwoven fabric exhibiting thermal insulation in certain regions can be obtained when fibers with high heat resistance such as aramid, PAN (polyacrylonitrile), PANOX (oxidized polyacrylonitrile), PBO (poly(p-phenylene-2,6-benzobisoxazole)), PBI (polybenzimidazole), PPS (polyphenylene sulfide), used alone or as a blend, are incorporated.

[0061] Embedding the Splittable Fibers onto the Nonwoven Fabric (300)

[0062] In the method of the present invention, a needling technique is employed to embed the splittable fibers onto the nonwoven fabric. That is, the microfibers (3) laid on the nonwoven fabric base (4) are subjected to a needling process, allowing the microfibrous structure to penetrate into the nonwoven fabric base (4). Thus, an integral structure is obtained. At this stage, the semi-finished nonwoven fabric, onto which microfibers (3) have been laid, undergoes at least one needling operation. The number of needling passes may be increased depending on the properties of the nonwoven fabric. The nonwoven fabric may be needled from the bottom and / or from the top side.

[0063] As previously stated, the nonwoven fabric base (4) referred to in the method of the present invention may be a web, i.e., a surface comprising cross-laid fibers that have not undergone pre-needling. Alternatively, the nonwoven fabric base (4) may have been subjected to a preneedling process.

[0064] The aforementioned nonwoven fabric base (4) comprises conventional macrofibers having a denier range of 1 to 15. The splittable fibers, after passing through the opening cylinder (2) and being converted into microfibers (3), are significantly refined, with fiber diameters ranging between 2 and 12 micrometers. Standard felting needles are reduction needles having a working part with an equilateral triangle cross-section, with 1 to 3 barbs per edge, and a thickness ranging from 12 to 46 gauge. The use of such standard needles in the method of the present invention is ineffective in bonding the two structures (the nonwoven fabric base (4) and the microfibers (3)) together. The technical effect of the needles employed in the needling stage of the present invention is significant. Preferred needles include those having working part cross-sections in the form of conical, equilateral triangular, twisted equilateral triangular, four-edged star, three-edged star, or equilateral triangles with angled edges. The design of these needles from tip to shank may feature a taper conically increasing from the point to the end of the working part, a continuously conical working part up to the shank, or a working part with a parallel conical transition from tip to shank. Needles with a thin working part cross-section are preferred. For this purpose, needles having a gauge range of preferably 36 to 48 and a barb count between 1 and 6 may be used in the method of the present invention. As a result of the needling process, a nonwoven fabric base containing an additional fiber area is obtained.

[0065] In an alternative embodiment of the method of the present invention, the nonwoven fabric base containing the additional fiber area may be subjected to a plate or blank cutting process after needling.

[0066] In another alternative embodiment of the method, the nonwoven fabric base containing the additional fiber area may be rolled and directed to different fields for various applications. Some example applications will be described below.

[0067] A representative illustration of the product obtained as a result of the method of the present invention is shown in Figure 3. As can be seen in Figure 3, the wheel arch liner nonwoven of the present invention comprises microfibers (3) penetrating into the nonwoven fabric base (4). The said nonwoven fabric base (4) may be composed of different types of fibers such as PET, PP, or PET / coPET. The microfibers (3) are formed by opening and splitting the splittable fiber tow. Splittable fibers such as PP / PET, PA / PET, or PET / PLA fibers with or without voids may be used. The splittable fibers may be used alone or blended with different macrofibers or microfibers.

[0068] Example 1 - Extrusion Coating

[0069] After the nonwoven fabric base comprising the additional fiber area obtained as a result of the method of the present invention, is wound into a roll, it is directed to an extrusion coating line. A polymer blend subjected to extrusion is coated onto the back surface of the nonwoven fabric base comprising the additional fiber area. A representative illustration of this is provided in Figure 4. As shown in Figure 4, the surface to which the extrusion coating (5) is applied is the back surface that does not contain microfiber (3) areas. The said polymer blend may comprise polyolefin-based polymers such as polypropylene or polyethylene, thermoplastic elastomers, and inorganic fillers. The inorganic fillers may include calcium carbonate, pumice, talc, dolomite, barite, and / or glass beads.

[0070] The extrusion technique employed is T-die cast extrusion. The polymer blend melt discharged from the T-die is cooled by cooling rollers and conveyor rollers, and, in addition to standard production conditions, controlled proportional stretching is applied in certain regions of the line (such as the T-die drawing region, roller cooling regions, etc.) to obtain an extruded layer with controlled porosity or micro-cracks, thereby improving acoustic properties.

[0071] Accordingly, the wheel arch liner nonwoven obtained by the method of the present invention comprises an extrusion coating (5) layer on a nonwoven fabric base (4) containing microfibers (3) penetrating into the surface. The extrusion coating (5) comprises a polymer containing polyolefins, thermoplastic elastomers, and inorganic fillers.

[0072] Example 2 - Extrusion Coating and Backing Nonwoven Fabric

[0073] In the extruder-coated structure prepared according to Example 1 , a backing nonwoven fabric (6) produced by carding-needling techniques is laminated onto the extrusion coating (5) layer. A representative illustration thereof is provided in Figure 5. The backing nonwoven fabric (6) may be a product manufactured by any nonwoven fabric production method (e.g., spunlace, spunbond, etc.). The bonding process may be performed by lamination. Lamination can be applied as known in the prior art and will not be detailed herein.

[0074] Accordingly, the wheel arch liner nonwoven obtained by the method of the present invention comprises an extrusion coating (5) layer on the nonwoven fabric base (4) containing microfibers (3) penetrating into the surface, and a backing nonwoven fabric (6) laminated on the extrusion coating (5) layer.

[0075] Although the acoustic properties of the splittable fiber are known, it is difficult to split the splittable fibers easily in the carding-needling process. That is, conversion of splittable fibers into microfibers is quite challenging in the prior art. Splittable fibers are bicomponent fibers containing at least two incompatible polymers. When a high force is applied to the fiber, the two polymer structures separate from each other and convert into microfibers. Alternatively, one of the polymers in the fiber can be dissolved in a suitable solvent while the undissolved polymer remains as microfibers within the fiber. Accordingly, commercially, splittable fibers are mostly converted by chemical washing or bonding methods such as water jet treatment. The method of the present invention enables successful processing of splittable fibers in the carding-needling process. The properties of the carding wires (2a) used during the application of splittable fibers onto the designated regions of the nonwoven fabric (200), as well as the properties of the needles used in the needling process for embedding splittable fibers onto the nonwoven fabric (300), are critical in this respect.

[0076] When the acoustic performance of the nonwoven fabric base comprising the additional fiber area obtained as a result of the method of the present invention is evaluated by impedance tube testing, the following results have been achieved. With extrusion coating, a sound absorption coefficient of 0.42 at a frequency of 800 Hz and 0.46 at a frequency of 1000 Hz have been reached. These values are significantly higher than those of commercial acoustic patches containing microfibers produced by meltblown techniques.

[0077] Industrial Applicability

[0078] The method of the present invention can be applied in manufacturing facilities engaged in the production of automotive textiles, technical textiles, and the like. In automotive floor carpets and trunk carpets, acoustic improvement can be achieved, and it can also be used in the field of filtration by virtue of its microfiber content. Although described specifically with respect to wheel arch liner felts or nonwovens, the processability of splittable fibers in the cardingneedling process will inspire applications in different fields. Different desired properties in the final product can be achieved through processes employing microfibers with varying characteristics. Use of heat-resistant fibers may yield nonwoven fabrics exhibiting superior heat resistance in designated regions.

Claims

CLAIMS1. A method which enables an increase in sound absorption coefficient in nonwoven fabric-based automotive textiles, comprising the following steps:Determining the regions on the nonwoven fabric where splittable fibers will be applied (100)Laying splittable fibers onto the predetermined regions of the nonwoven fabric (200)Embedding the splittable fibers onto the nonwoven fabric (300).

2. A method according to claim 1 , characterized in that the step (200) of laying splittable fibers onto predetermined regions of a nonwoven fabric comprises feeding a splittable fiber tow (1) to an opening cylinder (2), splitting said splittable fiber tow(1) into microfibers (3) by the action of carding wires (2a) that is disposed on an outer surface of said opener cylinder (2), and laying the resulting microfibers (3) onto the nonwoven fabric base (4) with the aid of a vacuum.

3. A method according to claim 2, characterized in that the splittable fiber tow (1) is opened and split with the aid of card wires (2a) with a working angle between -10° and 50°, a density between 75 and 325 PPSI, and a tooth height between 0.8 and 3.5 mm, resulting in microfibers (3).

4. A method according to any one of claims 1 to 3, characterized in that said splittable fibers are PP / PET, PA / PET, or PET / PLA.

5. A method according to any one of claims 1 to 3, characterized in that the splittable fibers are blended with microfibers or macrofibers.

6. A method according to claim 1 , characterized in that the step of embedding the splittable fibers onto the nonwoven fabric (300) comprises subjecting the semi-finished nonwoven fabric coated with microfibers (3) to at least one needling process.

7. A method according to claim 6, characterized in that the semi-finished nonwoven fabric coated with microfibers (3) is needled from the bottom and / or top side.

8. A method according to claim 6 or 7, characterized in that it comprises the step of needling the semi-finished nonwoven fabric having microfibers (3) laid thereon with needles having a working part cross-section selected from the group consisting ofconical, equilateral triangular, twisted equilateral triangular, four-edged star, three- edged star, and equilateral triangular with angled edges.A method according to claim 6 or 7, characterized in that it comprises the step of needling the semi-finished nonwoven fabric having microfibers (3) laid thereon with needles having a tip-to-shank design in which the working part tapers with an increasing conical angle from the point toward the end.

9. A method according to claim 6 or 7, characterized in that the semi-finished nonwoven fabric coated with microfibers (3) is needled with needles having either a continuously conical cross-section from tip to shank or having a working part with a parallel conical transition from tip to shank.

10. A method according to claim 6 or 7, characterized in that the semi-finished nonwoven fabric coated with microfibers (3) is needled with needles having a gauge between 36 and 48 and a barb number between 1 and 6.

11. A nonwoven fabric-based automotive textile, characterized by comprising microfibers (3) which is formed by opening and splitting a splittable fiber tow penetrating into the nonwoven fabric base (4).

12. An automotive textile according to claim 12, characterized by comprising an extrusion coating (5) layer which contains polyolefin-based polymers, thermoplastic elastomers, and inorganic additives.

13. An automotive textile according to claim 13, characterized by comprising a backing nonwoven fabric (6) which is laminated on the said extrusion coating (5) layer.

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