Mute cotton material for tires based on bio-based degradable fibers and preparation process of mute cotton material

Abstract

The invention provides a bio-based degradable fiber-based mute cotton material for tires, which is prepared from the following raw materials in percentage by weight: 60 to 65 percent of modified polylactic acid fiber, 20 to 25 percent of hemp-based polyhydroxyalkanoate fiber, 8 to 10 percent of chitosan-based superfine functional fiber, 5 to 7 percent of starch-based degradable hot melt adhesive, 1 to 2 percent of natural phytic acid modifier and the balance of biomass diatomite powder, the sum of the weight percentages of the components is 100%. The chitosan-based superfine functional fibers are superfine fibers activated by a natural cross-linking agent with the mass fraction of 0.3-0.6%. Therefore, full-bio-based degradable components are compounded, modified polylactic acid is used as a structural framework, efficient sound-absorbing pores are constructed by hemp-based fibers and diatomite, interfacial compatibility and structural strength are improved by activated chitosan fibers, and a degradable hot melt adhesive and a natural phytic acid modifier are matched, so that the sound-absorbing and sound-absorbing composite material is obtained. The prepared mute cotton material has excellent sound absorption and noise reduction performance and structural size stability, meets the tire working condition use requirements, can be completely biodegraded, and has use performance and environmental protection benefits.

Description

Technical Field

[0001] This invention relates to the field of foam materials technology, and more specifically, to a tire sound-absorbing cotton material based on bio-based biodegradable fibers and its preparation process. Background Technology

[0002] As the automotive industry moves towards lower carbon emissions and higher comfort, tire cavity noise has become a significant factor affecting the driving experience. Insulating the inner tube cavity with sound-absorbing material is currently the mainstream and effective noise reduction method. Existing tire sound-absorbing materials mostly use petroleum-based polyurethane and polyester fibers, which, while possessing some sound absorption effect, have significant shortcomings.

[0003] These materials rely on non-renewable petrochemical resources, resulting in high carbon emissions during production. Furthermore, the products are difficult to degrade naturally after disposal, easily leading to microplastic pollution. Meanwhile, the tire's inner cavity is subjected to harsh conditions of high temperature, humidity, and high-frequency vibration over a long period. Traditional sound-absorbing cotton is prone to thermal aging, structural powdering, and shedding, limiting its lifespan. Its simple sound-absorbing structure also results in poor absorption of low-frequency noise, making it difficult to meet the noise reduction requirements of high-end models and new energy vehicles.

[0004] In recent years, bio-based biodegradable materials have become a research hotspot. However, existing bio-based fibers generally suffer from poor temperature resistance, weak hydrolysis resistance, and insufficient mechanical properties. Direct application to tire sound insulation materials can easily lead to excessively rapid performance degradation, failing to meet the long-term use requirements of tires.

[0005] Therefore, there is an urgent need for a tire noise-reducing cotton material and preparation process based on bio-based biodegradable fibers to solve the problems in the existing technology. Summary of the Invention

[0006] The main objective of this invention is to provide a tire noise-reducing cotton material and preparation process based on bio-based biodegradable fibers, so as to at least solve the problems of non-degradability of petroleum-based materials, poor adaptability of bio-based fibers to working conditions, short service life of noise-reducing cotton and poor low-frequency noise reduction effect in the prior art.

[0007] To achieve the above objectives, the first aspect of the present invention provides a tire noise-reducing cotton material based on bio-based biodegradable fibers. The raw materials, by weight percentage, include: 60-65% modified polylactic acid fiber, 20-25% hemp-based polyhydroxyalkanoate fiber, 8-10% chitosan-based ultrafine functional fiber, 5-7% starch-based biodegradable hot melt adhesive, 1-2% natural phytic acid modifier, and the balance being biomass diatomaceous earth powder, with the sum of the weight percentages of each component being 100%. The chitosan-based ultrafine functional fiber is an ultrafine fiber activated by 0.3-0.6% by mass of a natural crosslinking agent.

[0008] Optionally, the natural crosslinking agent is a citric acid-based crosslinking agent.

[0009] Optionally, the modified polylactic acid fiber is a heat-resistant polylactic acid fiber with a linear density of 2.5~3.5 dtex, and the linear density of hemp-based polyhydroxyalkanoate fiber is 0.8~1.5 dtex.

[0010] Optionally, the sound-absorbing cotton has a gradient layered structure, consisting of a dense surface layer, a fluffy sound-absorbing middle layer, and an inner bonding layer from top to bottom.

[0011] The density of the surface dense layer is 120~150 g / m³. 2 The density of the middle layer of loose sound-absorbing material is 60~80 g / m³. 2 The density of the inner bonding layer is 90~110 g / m². 2 .

[0012] A second aspect of this invention provides a preparation process for a tire sound-absorbing cotton material based on bio-based biodegradable fibers, applicable to the tire sound-absorbing cotton material based on bio-based biodegradable fibers described in this invention, comprising the following steps:

[0013] Step 1: Activate the chitosan-based ultrafine functional fibers with a natural crosslinking agent to obtain activated chitosan-based ultrafine functional fibers; preheat the starch-based biodegradable hot melt adhesive to a molten state; mix the natural phytic acid modifier and biomass diatomaceous earth powder in a certain proportion to obtain a compound additive.

[0014] Step 2: Weigh the modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and the activated chitosan-based ultrafine functional fiber according to the ratio, add the compounding agent and molten starch-based biodegradable hot melt adhesive, mix evenly and then perform low-temperature plasma treatment, and then loosen and open to obtain mixed fiber bundles;

[0015] Step 3: The mixed fiber bundles are combed by airflow and laid in three layers according to different conveying volumes and wind pressures to form a dense surface layer, a loose sound-absorbing middle layer, and an inner bonding layer in sequence, thus obtaining a gradient fiber web blank.

[0016] Step 4: Heat and press the gradient fiber web blank to heat-melt and bond the fibers of the gradient fiber web to shape it, and obtain the sound-absorbing cotton roll after cooling.

[0017] Step 5: Die-cut the sound-absorbing cotton roll into customized specifications, spray biodegradable pressure-sensitive adhesive on its surface and attach release paper to obtain the finished sound-absorbing cotton material.

[0018] Optionally, in step 1, the activation process of chitosan-based ultrafine functional fibers is as follows:

[0019] Take the prescribed amount of chitosan-based ultrafine functional fiber, add 6 to 10 times its weight of deionized water, and ultrasonically disperse for 10 to 15 minutes. Then add 0.5% by weight of citric acid crosslinking agent solution and stir at 30 to 40°C for 20 to 30 minutes to complete the activation. After activation, filter and wash until there is no residual crosslinking agent.

[0020] Optionally, in step 2, the low-temperature plasma treatment parameters are: power 80~120W, treatment time 3~5min; loosening and opening speed 200~300r / min, and opening time 5~8min.

[0021] Optionally, in step 3, the forming parameters for each layer are:

[0022] The surface dense layer is subjected to a wind pressure of 300~400Pa and a fiber conveying rate of 80~100kg / h;

[0023] The middle layer of loose sound-absorbing layer uses a wind pressure of 150~250Pa and a fiber conveying rate of 40~60kg / h;

[0024] The inner bonding layer uses a wind pressure of 250~300Pa and a fiber conveying rate of 60~70kg / h;

[0025] The mesh laying speed for each layer is 3~5m / min.

[0026] Optionally, in step 4, the specific parameters for heating and pressurizing are: temperature 130~150℃, heating time 8~12min, and pressurizing pressure 0.2~0.3MPa.

[0027] The present invention discloses a tire noise-reducing cotton material based on bio-based biodegradable fibers. The raw materials, by weight percentage, include: 60-65% modified polylactic acid fiber, 20-25% hemp-based polyhydroxyalkanoate fiber, 8-10% chitosan-based ultrafine functional fiber, 5-7% starch-based biodegradable hot melt adhesive, 1-2% natural phytic acid modifier, and the balance being biomass diatomaceous earth powder. The sum of the weight percentages of each component is 100%. The chitosan-based ultrafine functional fiber is an ultrafine fiber activated by 0.3-0.6% by mass of a natural crosslinking agent. By using a blend of fully bio-based biodegradable components, with modified polylactic acid as the structural framework, hemp fibers and diatomaceous earth to construct highly efficient sound-absorbing pores, activated chitosan fibers to improve interfacial compatibility and structural strength, and combined with biodegradable hot melt adhesive and natural phytic acid modifier, the prepared sound-absorbing cotton material has excellent sound absorption and noise reduction performance and structural dimensional stability, meeting the requirements for tire operation. At the same time, the material is completely biodegradable, combining performance and environmental benefits. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a flow chart of a process for preparing tire noise-reducing cotton material based on bio-based biodegradable fibers, which is an optional embodiment of the present invention. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] This application provides a tire noise-reducing cotton material based on bio-based biodegradable fibers. The raw materials, by weight percentage, include: 60-65% modified polylactic acid fiber, 20-25% hemp-based polyhydroxyalkanoate fiber, 8-10% chitosan-based ultrafine functional fiber, 5-7% starch-based biodegradable hot melt adhesive, 1-2% natural phytic acid modifier, and the balance being biomass diatomaceous earth powder. The sum of the weight percentages of each component is 100%. The chitosan-based ultrafine functional fiber is an ultrafine fiber activated by 0.3-0.6% by mass of a natural crosslinking agent.

[0032] Specifically, the tire sound-absorbing cotton material based on bio-based biodegradable fibers in this solution is composed of a fully bio-based biodegradable compound. The raw materials, by weight percentage, include 60-65% modified polylactic acid fiber, 20-25% hemp-based polyhydroxyalkanoate fiber, 8-10% chitosan-based ultrafine functional fiber, 5-7% starch-based biodegradable hot melt adhesive, 1-2% natural phytic acid modifier, and biomass diatomaceous earth powder. The sum of the weight percentages of each component is 100%. Modified polylactic acid fiber serves as the main skeleton fiber, providing core structural support and heat resistance stability, adapting to temperature changes under tire operating conditions, and ensuring that the material does not shrink or deform during long-term use. Hemp-based polyhydroxyalkanoate fiber, made from biomass, combines the porous sound-absorbing properties of natural hemp fiber with the biodegradability of polyhydroxyalkanoate. This formula can create a fluffy, porous structure to enhance sound absorption. The chitosan-based ultrafine functional fiber is an ultrafine fiber activated by a natural crosslinking agent with a mass fraction of 0.3-0.6%. After activation, it can improve fiber compatibility, structural strength, and antibacterial and aging resistance, while maintaining biodegradability. The starch-based biodegradable hot melt adhesive serves as an environmentally friendly bonding component, achieving fiber bonding and fixation during the hot pressing process, avoiding the use of traditional non-degradable adhesives. The natural phytic acid modifier can improve the interfacial bonding force of each component and improve the material's heat resistance and aging resistance. The biomass diatomaceous earth powder can further optimize the internal pore structure of the material, enhance the sound absorption and noise reduction effect, and improve the material's dimensional stability. The overall formula achieves excellent sound absorption and noise reduction functions while using biodegradable components throughout the process. It can naturally degrade after disposal, meeting environmental protection requirements.

[0033] In one possible implementation, the natural crosslinking agent is a citric acid-based crosslinking agent.

[0034] Specifically, citric acid-based crosslinking agents are selected as the natural crosslinking agents. These agents use natural citric acid and its salts as the main active ingredients, are widely available, have excellent biocompatibility, and are completely biodegradable. During the activation process of chitosan-based ultrafine functional fibers, citric acid-based crosslinking agents can form a stable three-dimensional network crosslinking structure through various interactions such as esterification and hydrogen bonding with the amino and hydroxyl groups on the chitosan molecular chain. This effectively improves the molecular aggregation state inside the fiber, significantly enhancing the mechanical strength, toughness, and structural stability of the chitosan-based ultrafine functional fibers. At the same time, citric acid-based crosslinking agents can effectively improve the interfacial bonding force between the fiber and other bio-based components, enhancing the compatibility and uniformity of each component during mixing, web laying, and hot pressing, avoiding process problems such as fiber delamination and interfacial debonding. In addition, this type of crosslinking agent can efficiently complete the crosslinking reaction at room temperature to medium temperature without requiring harsh reaction conditions, adapting to the mild process parameter range of this solution. Furthermore, it is non-toxic, harmless, and environmentally friendly, and can naturally degrade after disposal, without causing additional burden on the ecological environment, perfectly matching the core design concept of green and environmentally friendly materials.

[0035] In one possible implementation, the modified polylactic acid fiber is a heat-resistant polylactic acid fiber with a linear density of 2.5~3.5 dtex, and the hemp-based polyhydroxyalkanoate fiber has a linear density of 0.8~1.5 dtex.

[0036] Specifically, the modified polylactic acid fiber uses heat-resistant polylactic acid fiber with a linear density controlled between 2.5 and 3.5 dtex. This fineness range allows the fiber to possess suitable stiffness and support, serving as the main skeleton of the sound-absorbing cotton to ensure overall structural strength and dimensional stability. It also maintains a good interlacing state during airflow combing and hot pressing. Simultaneously, the heat-resistant modification allows it to adapt to temperature fluctuations in the tire operating environment and the hot pressing process during preparation, avoiding shrinkage, softening, or deformation. The linear density of the hemp-based polyhydroxyalkanoate fiber is set at 0.8 to 1.5 dtex, which is a relatively fine fiber fineness. It is easier to form a fluffy, porous internal structure, which is conducive to sound waves entering the pores and generating loss, thereby improving the sound absorption and noise reduction effect of the sound-absorbing cotton. The combination of the two fibers with different linear density parameters can achieve a balance between structural strength, fluffiness, and sound absorption performance, ensuring the reliability of the sound-absorbing cotton under complex working conditions inside the tire cavity, while maximizing the sound absorption advantages of bio-based biodegradable materials.

[0037] The preparation process of modified polylactic acid (PLA) fiber is as follows: Modified PLA is prepared by melt spinning. Using PLA resin as raw material, the PLA resin is first dried in a constant temperature oven at 80-90℃ for 4-6 hours to remove moisture and prevent air bubbles from affecting fiber quality during spinning. The dried PLA resin, along with 2-3% polycaprolactone (PCL) and 0.5-1% nano-silica particles, is added to a twin-screw extruder. The extruder temperatures are set at 160℃, 170℃, 180℃, and 175℃ respectively, and the screw speed is controlled at 80-100 r / min. Melt blending achieves uniform dispersion of the components and simultaneously modifies the heat resistance of PLA. It is important to note that PCL and nano-silica particles should be pre-mixed for 10-15 minutes before mixing to ensure uniform dispersion of the nanoparticles and prevent agglomeration that could affect the modification effect. The blended melt is then extruded through a spinneret with a spinneret orifice diameter of 0 mm after precise flow control by a metering pump. The extruded melt tow, with a diameter of 2~0.3mm, is immediately immersed in a cooling water bath at 30~40℃ for rapid cooling and shaping. The water temperature in the cooling water bath must be kept constant, with a temperature difference not exceeding ±2℃, to prevent uneven cooling of the tow and resulting fluctuations in linear density. Subsequently, the fibers undergo a drawing process, with the draw ratio controlled at 3~5 times to improve the crystallinity and mechanical properties of the fibers. After drawing, the fibers are dried with hot air (temperature 60~70℃, time 20~30min) to remove surface moisture. Hot air drying requires... Uniform airflow prevents localized overheating that could lead to fiber embrittlement. Finally, the fiber is wound into shape using a winding machine at a speed controlled at 50~80m / min, matching the drawing speed to prevent fiber stretching or relaxation. This results in heat-resistant modified polylactic acid fibers with a linear density of 2.5~3.5dtex and a length of 38~51mm. The glass transition temperature is increased to 65~70℃, making it suitable for temperature variations of -40~120℃ under tire operating conditions. It also exhibits excellent structural support and heat resistance stability.

[0038] In one possible implementation, the sound-absorbing cotton has a gradient layered structure, consisting of a dense surface layer, a fluffy sound-absorbing middle layer, and an inner bonding layer from top to bottom.

[0039] The density of the surface dense layer is 120~150 g / m³. 2 The density of the middle layer of loose sound-absorbing material is 60~80 g / m³. 2 The density of the inner bonding layer is 90~110 g / m². 2 .

[0040] Specifically, the sound-absorbing cotton adopts a gradient layered structure design, consisting of a dense surface layer, a loose sound-absorbing middle layer, and an inner bonding layer from top to bottom. The density of the dense surface layer is controlled at 120~150g / m². 2This layer has a relatively high density and a more compact structure, forming a stable protective layer on the outside of the sound-absorbing cotton. It resists airflow erosion and slight friction during tire operation, while also providing initial blocking and reflection of external sound waves. The middle layer, a loose sound-absorbing layer, has a density of 60~80 g / m³. 2 It is the part with the lowest surface density and highest bulkiness in the three-layer structure. It has abundant internal pores and good connectivity, which can efficiently dissipate sound wave energy and achieve sound absorption and noise reduction. The density of the inner bonding layer is 90~110g / m². 2 With a structural density between the former two, it has both a certain structural support and good fit and flatness, which facilitates stable bonding with the inner wall of the tire. Through this gradient layering and differentiated surface density, the sound-absorbing cotton can achieve the optimal balance between structural strength, sound absorption effect and installation fit, and is suitable for the actual working conditions of the tire.

[0041] In one possible implementation, the application of the tire sound-absorbing cotton material based on bio-based biodegradable fibers described in this application includes the following steps:

[0042] Step 1: Activate the chitosan-based ultrafine functional fibers with a natural crosslinking agent to obtain activated chitosan-based ultrafine functional fibers; preheat the starch-based biodegradable hot melt adhesive to a molten state; mix the natural phytic acid modifier and biomass diatomaceous earth powder in a certain proportion to obtain a compound additive.

[0043] Step 2: Weigh the modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and the activated chitosan-based ultrafine functional fiber according to the ratio, add the compounding agent and molten starch-based biodegradable hot melt adhesive, mix evenly and then perform low-temperature plasma treatment, and then loosen and open to obtain mixed fiber bundles;

[0044] Step 3: The mixed fiber bundles are combed by airflow and laid in three layers according to different conveying volumes and wind pressures to form a dense surface layer, a loose sound-absorbing middle layer, and an inner bonding layer in sequence, thus obtaining a gradient fiber web blank.

[0045] Step 4: Heat and press the gradient fiber web blank to heat-melt and bond the fibers of the gradient fiber web to shape it, and obtain the sound-absorbing cotton roll after cooling.

[0046] Step 5: Die-cut the sound-absorbing cotton roll into customized specifications, spray biodegradable pressure-sensitive adhesive on its surface and attach release paper to obtain the finished sound-absorbing cotton material.

[0047] Specifically, step 1: Weigh chitosan-based ultrafine functional fibers and place them in a reaction vessel. Add an appropriate amount of deionized water and start ultrasonic dispersion treatment to thoroughly break up any fiber agglomerates, allowing the fibers to fully swell and prevent incomplete activation due to fiber aggregation. Activate the fibers to improve their structural strength and component compatibility. After activation, filter and wash repeatedly with deionized water until no residual crosslinking agent remains. Allow to air dry to obtain activated chitosan-based ultrafine functional fibers. Separately, take starch-based biodegradable hot melt adhesive and heat it slowly at 60℃~80℃ in a constant temperature device, stirring regularly to prevent local overheating and charring. Once the adhesive is completely melted and smooth, seal and keep it warm for later use. Pour natural phytic acid modifier and biomass diatomaceous earth powder into a mixing device and stir at room temperature until the powder is fully mixed and free of stratification and agglomeration to obtain a compound additive. Store the three types of pretreated materials separately in sealed containers, ensuring moisture and dust protection to avoid affecting subsequent processes. The natural phytic acid modifier uses a phytic acid aqueous solution with a concentration of 50-60%. Before use, it needs to be diluted and mixed with ethanol at a volume ratio of 1:1 to enhance its dispersion uniformity on the fiber surface, avoid the local aggregation of the modifier affecting the interface bonding effect of each component, and ensure the stability of subsequent mixing and molding processes.

[0048] Step 2: Weigh the modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber, and activated chitosan-based ultrafine functional fiber according to the formula ratio, and put them into a mixer for initial mixing until the three types of fibers are evenly distributed and there is no obvious stratification; then add the prepared compound additives and molten starch-based biodegradable hot melt adhesive, and continue stirring until the additives are evenly attached to the fiber surface, the hot melt adhesive is fully wetted into the fiber, and there is no powder agglomeration or adhesive block adhesion; transfer the evenly mixed material into a low-temperature plasma treatment device to complete the fiber surface activation modification, and use the plasma etching effect to improve the fiber interface bonding force and strengthen the adhesion between components; finally, send the material into a fluffing and opening machine for low-speed opening to break up fiber clumps, eliminate internal stress in the material, and obtain fluffy, homogeneous, and clump-free mixed fiber bundles.

[0049] Step 3: The mixed fiber bundle is fed into the airflow carding machine at a uniform speed. The controlled airflow pressure is used to fully disperse the fibers into monofilaments, while simultaneously achieving directional fiber arrangement and reducing fiber damage caused by mechanical carding. According to the functional positioning of the three-layer gradient structure, the process parameters are adjusted in stages to lay the web sequentially. First, a dense outer layer is laid, controlling the fiber feeding speed and airflow intensity to form a dense, wear-resistant, and airflow-resistant outer protective structure. Then, a loose sound-absorbing middle layer is laid, slowing down the feeding speed and reducing the airflow intensity to create a large number of interconnected pores. The sound wave energy is dissipated by pore friction and air damping to achieve noise reduction. Finally, an inner bonding layer is laid, adjusting parameters to balance density and flatness for easy subsequent bonding and fixation. The three layers of fiber web are stacked sequentially, with each layer tightly connected without gaps, ultimately forming a structurally stable gradient fiber web blank.

[0050] Step 4: The gradient fiber mesh blank is smoothly fed into the hot press molding equipment, and gentle heating and uniform pressure are applied simultaneously. The heat is used to melt and soften the hot melt adhesive, and the pressure is used to make the fibers of each layer interlock and contact tightly. The molten adhesive fills the gaps between the fibers to form bonding points, which not only ensures the overall structure is firm, but also retains the porous sound-absorbing structure in the middle layer. After hot pressing until the fibers are completely shaped, it is transferred to a room temperature environment for air cooling to solidify the hot melt adhesive bonding nodes, stabilize the material size and gradient structure, and prevent shrinkage, curling and deformation. After cooling, it is rolled up to obtain a continuous and regular sound-absorbing cotton roll.

[0051] Step 5: Place the sound-absorbing cotton roll on the die-cutting equipment and precisely die-cut it according to the actual installation dimensions of the tire cavity, removing edge waste to ensure the sheet specifications are suitable; evenly spray the biodegradable pressure-sensitive adhesive on the bonding surface of the die-cut sheet, controlling the spraying speed to be uniform and the adhesive layer thickness to ensure no missed coating or adhesive accumulation, and to ensure firm adhesion to the inner wall of the tire and prevent edge lifting; after the adhesive layer surface is dry and no longer sticky, attach the release paper and roll it to compact it, and protect the adhesive layer to avoid adhesion and contamination, finally obtaining the finished sound-absorbing cotton material that can be directly assembled.

[0052] In one possible implementation, the activation process for chitosan-based ultrafine functional fibers is as follows:

[0053] Take the prescribed amount of chitosan-based ultrafine functional fiber, add 6 to 10 times its weight of deionized water, and ultrasonically disperse for 10 to 15 minutes. Then add 0.5% by weight of citric acid crosslinking agent solution and stir at 30 to 40°C for 20 to 30 minutes to complete the activation. After activation, filter and wash until there is no residual crosslinking agent.

[0054] Specifically, during the activation treatment of chitosan-based ultrafine functional fibers, the prescribed amount of fiber is accurately weighed and placed into a dedicated reaction vessel. Deionized water at a ratio of 6-10 times the fiber weight is added as a dispersion medium. This ratio ensures complete immersion of the fiber in the deionized water, preventing insufficient wetting and poor ultrasonic dispersion due to insufficient water, while also avoiding excessive water that would increase subsequent filtration and washing time and energy consumption. This creates a uniform reaction environment for the subsequent activation reaction. Ultrasonic equipment is then used for continuous dispersion for 10-15 minutes. This moderate ultrasonic duration effectively breaks down fiber agglomerates through cavitation and mechanical vibration, ensuring each ultrafine fiber is fully swelled and wetted. This avoids uneven activation and excessive localized reactions caused by fiber aggregation, while also preventing mechanical damage to the fiber's basic structural properties from prolonged ultrasonic treatment. After ultrasonic dispersion, a 0.5% (w / w) solution of citric acid-based crosslinking agent is slowly added. This crosslinking agent ensures proper interaction with the amino and hydroxyl groups on the fiber molecular chains. The bonding and cross-linking reaction of the fibers enhances the activation effect without causing excessive cross-linking due to excessive concentration of cross-linking agent, which would make the fibers stiff and brittle and affect the compatibility with other components. The reaction system is placed in a constant temperature environment of 30~40℃. This temperature range avoids the reaction rate being too slow and insufficient activation at low temperatures, while preventing the cross-linking agent from decomposing itself or causing thermal degradation of the fibers at high temperatures, ensuring a mild and efficient activation reaction and the integrity of the fiber structure. Under this condition, the mixture is stirred at a constant speed for 20~30 minutes to allow the cross-linking agent to fully contact and react with the fibers, further optimizing the fiber surface activity, enhancing the fiber structural strength and aging resistance, and improving its interfacial compatibility with subsequent compounding agents, hot melt adhesives and other components. After the stirring reaction is completed, the mixture is immediately filtered and separated. The fibers are then repeatedly rinsed with deionized water until no cross-linking agent residue is detected in the filtrate, thoroughly removing unreacted free cross-linking agent and impurities, avoiding residual substances from affecting the degradation and noise reduction performance of the finished sound-absorbing cotton in subsequent mixing, molding and production, and ensuring the safety and stability of the final material.

[0055] In one possible implementation, in step 2, the low-temperature plasma treatment parameters are: power 80~120W, treatment time 3~5min; loosening and opening speed 200~300r / min, and opening time 5~8min.

[0056] Specifically, in step 2, the low-temperature plasma treatment uses parameters of 80~120W power and 3~5min treatment time. This power range can gently etch the fiber surface with high-energy plasma particles and introduce active groups, effectively improving the interfacial bonding force between the fiber and the additives and hot melt adhesive. It can also avoid damaging the fiber structure and preventing fiber breakage due to excessive power. The treatment time of 3~5min can ensure uniform activation of the fiber surface, achieving sufficient modification while preventing over-treatment that would lead to a decline in fiber performance. In the fluffing and opening stage, the rotation speed is controlled at 200~300r / min and the opening time is 5~8min. This rotation speed range can gently break up fiber clumps and eliminate internal stress in the material through mechanical force, allowing the mixed fibers to be fully fluffed and homogeneous. It can prevent the fibers from tearing and breaking due to excessive rotation speed, and it can also prevent the opening from being incomplete due to excessive rotation speed. Combined with the opening time of 5~8min, it can thoroughly break up residual fiber clumps, making the components more evenly interwoven. This lays a stable material foundation for the subsequent airflow combing and forming processes, ensuring that the finished sound-absorbing cotton has a regular structure and balanced performance. Following this application, the low-temperature plasma treatment uses air as the discharge medium and is carried out at atmospheric pressure. The process requires no additional temperature control; surface modification can be completed solely through the plasma's own energy, thus eliminating the need to limit the processing temperature. Under a set power, the air medium between the electrodes is ionized, forming a plasma flow containing high-energy electrons, ions, and active particles. These high-energy particles undergo physical collisions and chemical reactions with the fiber surface. On one hand, this slightly etches the fiber surface to improve surface roughness; on the other hand, it introduces polar active groups into the fiber surface, thereby enhancing the fiber surface activity and interfacial bonding, and strengthening the compatibility and adhesion strength between the components.

[0057] In one possible implementation, the forming parameters for each layer in step 3 are:

[0058] The surface dense layer is subjected to a wind pressure of 300~400Pa and a fiber conveying rate of 80~100kg / h;

[0059] The middle layer of loose sound-absorbing layer uses a wind pressure of 150~250Pa and a fiber conveying rate of 40~60kg / h;

[0060] The inner bonding layer uses a wind pressure of 250~300Pa and a fiber conveying rate of 60~70kg / h;

[0061] The mesh laying speed for each layer is 3~5m / min.

[0062] Specifically, in step 3, the surface dense layer uses a wind pressure of 300~400Pa and a fiber conveying rate of 80~100kg / h. The higher wind pressure allows the fibers to fully interweave and become dense, and the larger conveying rate quickly forms a continuous and dense outer layer structure, improving wear resistance and erosion resistance. The middle loose sound-absorbing layer uses a wind pressure of 150~250Pa and a fiber conveying rate of 40~60kg / h. The lower wind pressure and smaller conveying rate can slow down the fiber packing density, forming a large number of interconnected pore structures, providing sufficient space for sound wave dissipation, and achieving excellent sound absorption and noise reduction effects. The inner bonding layer uses a wind pressure of 300~400Pa and a fiber conveying rate of 80~100kg / h. With a pressure of 250~300Pa and a fiber conveying capacity of 60~70kg / h, the wind pressure and conveying capacity are between those of the surface and middle layers, which ensures moderate fiber density, guaranteeing structural support strength while maintaining a smooth and uniform surface for easy and stable bonding with the tire inner wall. The web laying speed of each layer is uniformly controlled at 3~5m / min. This speed range ensures continuous and stable forming of the three-layer fiber web with tight interlayer connections and no gaps, while avoiding uneven web laying due to excessive speed or reduced production efficiency due to excessively slow speed. The final product is a gradient fiber web blank with distinct structural gradients and balanced and stable performance.

[0063] In one possible implementation, the specific parameters for heating and pressurizing in step 4 are: temperature 130~150℃, heating time 8~12min, and pressurizing pressure 0.2~0.3MPa.

[0064] Specifically, in step 4, the heating and pressurization parameters are 130~150℃, heating time 8~12min, and pressure 0.2~0.3MPa. This temperature range allows the starch-based biodegradable hot melt adhesive to fully melt and flow, ensuring that the adhesive fully wets the fiber interface to form a strong bond, while preventing the fibers and adhesive from thermally degrading, yellowing, and becoming brittle due to excessive temperature. The heating time of 8~12min ensures that the heat is evenly conducted to the inside of the fiber network, allowing both the inner and outer layers of adhesive to reach an ideal melting state, avoiding the problem of weak internal bonding. At the same time, the pressure of 0.2~0.3MPa ensures that the fibers of each layer are tightly bonded and interwoven, ensuring the overall structure is stable and shaped, while preserving the pre-set porous sound-absorbing structure of the middle layer from being over-compacted. This balances the structural strength of the material with sound absorption and noise reduction performance, making the formed silent cotton roll dimensionally stable, not prone to shrinkage and deformation, and with tight interlayer bonding without delamination.

[0065] The present application is further illustrated by the following embodiments.

[0066] I. General Principles and Preliminary Preparations for the Experiment

[0067] All examples and comparative experiments were conducted in a constant temperature and humidity laboratory, with the ambient temperature controlled at 23±2℃ and the relative humidity at 50±5%. All raw materials used in the experiments were from the same batch. The universal testing machine, impedance tube, composting reactor, constant temperature oven and other equipment were calibrated in advance to ensure that the error was controlled within ±1%. Three parallel samples were prepared simultaneously for each sample group, and the test data were taken as the arithmetic mean. Abnormal data with a deviation of more than 5% were removed.

[0068] II. Implementation Examples

[0069] Example 1

[0070] Raw material weighing and preparation (by weight percentage) were performed using an electronic analytical balance with an accuracy of 0.001g. The following components were weighed: 62% heat-resistant modified polylactic acid fiber (linear density 3.0dtex), 22% hemp-based polyhydroxyalkanoate fiber (linear density 1.2dtex), 9% chitosan-based ultrafine functional fiber, 6% starch-based biodegradable hot melt adhesive, 1.5% natural phytic acid modifier, and the remainder being biomass diatomaceous earth powder. After weighing, each component was checked to ensure that the sum of the weight percentages of each component was 100%.

[0071] Preparation process steps:

[0072] (1) Fiber activation: Chitosan-based ultrafine functional fibers are placed in a special reaction vessel, and deionized water with a weight of 8 times the fiber weight is added. The ultrasonic equipment is turned on to disperse the fibers for 12 minutes to fully break up the fiber agglomerates. Then, a citric acid crosslinking agent solution with a mass fraction of 0.5% is added, and the mixture is placed in a constant temperature water bath at 35°C and stirred at a constant speed for 25 minutes to complete the activation. After activation, the mixture is filtered and repeatedly washed with deionized water until there is no crosslinking agent residue in the filtrate. The filtrate is then air-dried for later use to obtain activated chitosan-based ultrafine functional fibers.

[0073] (2) Raw material pretreatment: The starch-based biodegradable hot melt adhesive is placed in a constant temperature oven at 70°C and preheated to a molten state. During this period, it is stirred once every 5 minutes to prevent local overheating and charring. The natural phytic acid modifier is mixed with biomass diatomaceous earth powder and stirred at room temperature for 10 minutes until the powder is uniform and free of lumps to obtain the compound additive.

[0074] (3) Fiber blending and modification: Modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and activated chitosan-based ultrafine functional fiber are put into a mixer and mixed for 12 minutes until they are evenly distributed and without layering. Add compounding agents and molten hot melt adhesive and continue stirring for 18 minutes until the compounding agents are completely attached and the adhesive fully wets the fibers. Transfer to a low-temperature plasma device, set the power to 100W and process for 4 minutes to complete the surface modification. Finally, send it to a loosening and opening machine, loosen it at a speed of 250r / min for 6 minutes, gently break up the fiber clumps and eliminate internal stress to obtain a homogeneous mixed fiber bundle.

[0075] (4) Gradient web forming: The mixed fiber bundles are fed into the airflow carding machine at a uniform speed and the layer parameters are adjusted as follows: the surface dense layer has an air pressure of 350 Pa and a fiber conveying rate of 90 kg / h, the middle loose sound-absorbing layer has an air pressure of 200 Pa and a fiber conveying rate of 50 kg / h, and the inner bonding layer has an air pressure of 270 Pa and a fiber conveying rate of 65 kg / h. The web laying speed of each layer is uniformly 4 m / min. The three layers are laid continuously with tight interlayer connections and no gaps to obtain a gradient fiber web blank.

[0076] (5) Hot pressing and post-treatment: The fiber web blank is smoothly fed into the hot pressing molding equipment, and the temperature is controlled at 140℃, heated for 10 minutes, and the pressure is 0.25MPa. The heating and pressing are completed simultaneously. After hot pressing, it is immediately transferred to a clean environment at room temperature and air-cooled for 15 minutes until the hot melt adhesive is completely cured. The sound-absorbing cotton roll is then rolled up and die-cut according to the standard size of the tire inner cavity. The biodegradable pressure-sensitive adhesive is evenly sprayed and the release paper is attached to obtain the finished product sample. Finished product quality control parameters: The surface dense layer has a density of 135g / m². 2 The middle layer of loose sound-absorbing material has a density of 70 g / m³. 2 The density of the inner bonding layer is 100g / m². 2 The sample was free of defects such as delamination, holes, and fiber agglomeration, and the gradient structure was complete and uniform.

[0077] Example 2

[0078] The raw material weighing and preparation (by weight percentage) were carried out using an electronic analytical balance with an accuracy of 0.001g. 60% of heat-resistant modified polylactic acid fiber (linear density 2.5dtex), 25% of hemp-based polyhydroxyalkanoate fiber (linear density 0.8dtex), 8% of chitosan-based ultrafine functional fiber, 5.7% of starch-based biodegradable hot melt adhesive, 1% of natural phytic acid modifier, and the balance being biomass diatomaceous earth powder were accurately weighed. After weighing, each component was checked to ensure that the sum of the weight percentages of each component was 100%, and that the batch of raw materials was consistent with that in Example 1.

[0079] Preparation process steps:

[0080] (1) Fiber activation: Chitosan-based ultrafine functional fibers are placed in a special reaction vessel, and deionized water with a weight of 6 times the fiber weight is added. The ultrasonic equipment is turned on to disperse the fibers for 10 minutes to fully break up the fiber agglomerates. Then, a citric acid crosslinking agent solution with a mass fraction of 0.3% is added, and the mixture is placed in a 30°C constant temperature water bath and stirred at a constant speed for 20 minutes to complete the activation. After activation, the mixture is filtered and repeatedly washed with deionized water until there is no crosslinking agent residue in the filtrate. The filtrate is then air-dried for later use to obtain activated chitosan-based ultrafine functional fibers.

[0081] (2) Raw material pretreatment: The starch-based biodegradable hot melt adhesive is placed in a constant temperature oven at 70°C and preheated to a molten state. During this period, it is stirred once every 5 minutes to prevent local overheating and charring. The natural phytic acid modifier is mixed with biomass diatomaceous earth powder and stirred at room temperature for 10 minutes until the powder is uniform and free of lumps to obtain the compound additive.

[0082] (3) Fiber blending and modification: Modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and activated chitosan-based ultrafine functional fiber are put into a mixer and mixed for 10 minutes until they are evenly distributed and without layering. Add compounding agents and hot melt adhesive and continue stirring for 16 minutes until the compounding agents are completely attached and the adhesive fully wets the fibers. Transfer to a low-temperature plasma device, set the power to 80W and process for 3 minutes to complete the surface modification. Finally, send it to a loosening and opening machine, loosen it at 200r / min speed for 5 minutes, gently break up the fiber clumps and eliminate internal stress to obtain a homogeneous mixed fiber bundle.

[0083] (4) Gradient web forming: The mixed fiber bundles are fed into the airflow carding machine at a uniform speed and the layer parameters are adjusted as follows: the surface dense layer has an air pressure of 300 Pa and a fiber conveying rate of 80 kg / h, the middle loose sound-absorbing layer has an air pressure of 150 Pa and a fiber conveying rate of 40 kg / h, and the inner bonding layer has an air pressure of 250 Pa and a fiber conveying rate of 60 kg / h. The web laying speed of each layer is uniformly 3 m / min. The three layers are laid continuously with tight interlayer connections and no gaps to obtain a gradient fiber web blank.

[0084] (5) Hot pressing and post-treatment: The fiber web blank is smoothly fed into the hot pressing molding equipment, and the temperature is controlled at 150℃, heated for 8 minutes, and the pressure is 0.2MPa. The heating and pressing are completed simultaneously. After hot pressing, it is immediately transferred to a clean environment at room temperature and air-cooled for 15 minutes until the hot melt adhesive is completely cured. The sound-absorbing cotton roll is then rolled up and die-cut according to the standard size of the tire inner cavity. The biodegradable pressure-sensitive adhesive is evenly sprayed and the release paper is attached to obtain the finished product sample. Finished product quality control parameters: The surface dense layer has a density of 120g / m². 2 The middle layer of loose sound-absorbing material has a density of 60g / m³. 2 The density of the inner bonding layer is 90g / m². 2 The sample has a smooth appearance, no structural defects, and a complete and uniform gradient structure.

[0085] Example 3

[0086] The raw material weighing and preparation (by weight percentage) were carried out using an electronic analytical balance with an accuracy of 0.001g. 65% of heat-resistant modified polylactic acid fiber (linear density 3.5dtex), 20% of hemp-based polyhydroxyalkanoate fiber (linear density 1.5dtex), 10% of chitosan-based ultrafine functional fiber, 7% of starch-based biodegradable hot melt adhesive, 2% of natural phytic acid modifier, and the balance being biomass diatomaceous earth powder were weighed. After weighing, each component was checked to ensure that the sum of the weight percentages of each component was 100%, and that the batch of raw materials was consistent with that in Example 1.

[0087] Preparation process steps:

[0088] (1) Fiber activation: Chitosan-based ultrafine functional fibers are placed in a special reaction vessel, and 10 times the weight of the fibers are added with deionized water. The ultrasonic equipment is turned on to disperse the fibers for 15 minutes to fully break up the fiber agglomerates. Then, 0.6% by mass of citric acid crosslinking agent solution is added, and the mixture is placed in a 40℃ constant temperature water bath and stirred at a constant speed for 30 minutes to complete the activation. After activation, the mixture is filtered and repeatedly washed with deionized water until there is no crosslinking agent residue in the filtrate. The filtrate is then air-dried for later use to obtain activated chitosan-based ultrafine functional fibers.

[0089] (2) Raw material pretreatment: The starch-based biodegradable hot melt adhesive is placed in a constant temperature oven at 70°C and preheated to a molten state. During this period, it is stirred once every 5 minutes to prevent local overheating and charring. The natural phytic acid modifier is mixed with biomass diatomaceous earth powder and stirred at room temperature for 10 minutes until the powder is uniform and free of lumps to obtain the compound additive.

[0090] (3) Fiber blending and modification: Modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and activated chitosan-based ultrafine functional fiber are put into a mixer and mixed for 15 minutes until they are evenly distributed and without layering. Add compounding agents and molten hot melt adhesive and continue stirring for 20 minutes until the compounding agents are completely attached and the adhesive fully wets the fibers. Transfer to a low-temperature plasma device, set the power to 120W and process for 5 minutes to complete the surface modification. Finally, send it to a fluffing and opening machine, and open it at a speed of 300r / min for 8 minutes to gently break up the fiber clumps and eliminate internal stress to obtain a homogeneous mixed fiber bundle.

[0091] (4) Gradient web forming: The mixed fiber bundles are fed into the airflow carding machine at a uniform speed and the layer parameters are adjusted as follows: the surface dense layer has an air pressure of 400 Pa and a fiber conveying rate of 100 kg / h, the middle loose sound-absorbing layer has an air pressure of 250 Pa and a fiber conveying rate of 60 kg / h, and the inner bonding layer has an air pressure of 300 Pa and a fiber conveying rate of 70 kg / h. The web laying speed of each layer is uniformly 5 m / min. The three layers are laid continuously with tight interlayer connections and no gaps to obtain a gradient fiber web blank.

[0092] (5) Hot pressing and post-treatment: The fiber web blank is smoothly fed into the hot pressing molding equipment, and the temperature is controlled at 130℃, heated for 12 minutes, and the pressure is 0.3MPa. The heating and pressing are completed simultaneously. After hot pressing, it is immediately transferred to a clean environment at room temperature and air-cooled for 15 minutes until the hot melt adhesive is completely cured. The sound-absorbing cotton roll is then rolled up and die-cut according to the standard size of the tire inner cavity. The biodegradable pressure-sensitive adhesive is evenly sprayed and the release paper is attached to obtain the finished product sample. Finished product quality control parameters: the density of the dense surface layer is 150g / m², and the density of the fluffy sound-absorbing middle layer is 80g / m². 2 The density of the inner bonding layer is 110g / m². 2 The sample has a complete structure, uniform performance, and no defects such as delamination or holes.

[0093] III. Comparative Example

[0094] Comparative Example 1

[0095] The experimental environment and raw material batches were completely consistent with those in Example 1, with only two variables adjusted: first, ordinary non-degradable EVA hot melt adhesive was used instead of starch-based biodegradable hot melt adhesive, while the proportions of the other components remained unchanged; second, the gradient web laying process was eliminated, and a single-layer uniform web laying process was adopted, controlling the web surface density to 180 g / m². 2 The hot pressing parameters and post-processing procedures are exactly the same as in Example 1, and a single-layer structure finished sample is prepared.

[0096] Comparative Example 2

[0097] The experimental environment, raw material batches, and proportions were completely consistent with those in Example 1, except for two processes that were omitted: first, the chitosan-based ultrafine functional fibers were not subjected to cross-linking activation treatment and the original fibers were used directly; second, the mixed fibers were not subjected to low-temperature plasma surface modification. The remaining mixing, web laying, hot pressing, and post-treatment processes were completely the same as those in Example 1, and finished product samples were prepared.

[0098] IV. Performance Verification Test

[0099] 1. Uniform requirements for sample preparation

[0100] The finished sound-absorbing cotton from Examples 1-3 and Comparative Examples 1-2 were cut into standard-sized samples according to the national testing standards. Three sets of parallel samples were prepared simultaneously for each test item. The sample surfaces were flat, without burrs or damage, and were uniformly marked to avoid test errors caused by individual sample differences.

[0101] 2. Test Items and Standardized Testing Methods

[0102] Sound absorption coefficient test: Dual microphone impedance tube detection was used; before the test, the equipment was calibrated and the ambient temperature was controlled at 23±2℃ and the humidity at 50±5%. The core noise frequency band of tire driving, 200Hz-2000Hz, was selected for frequency sweep test. Each parallel sample was tested 3 times. After removing outliers, the arithmetic mean of each frequency band was taken to obtain the final average sound absorption coefficient.

[0103] Tensile strength test: Determination of breaking strength and elongation at break (strip method) was performed using a universal testing machine. The specimen was cut into standard strips of 5cm×20cm, the clamping distance was set to 100mm, the tensile speed was 100mm / min, and 3 sets of parallel specimens were tested. The maximum tensile force at the time of sample breakage was recorded, and the average value (unit: N / 5cm) was taken to characterize the structural stability of the material.

[0104] Biodegradation rate test: The laboratory controlled composting method was adopted; the sample was crushed and mixed with standard composting matrix, placed in a special reactor, and the temperature was controlled at 58±2℃ and the oxygen concentration at ≥15%. The sample was continuously cultured for 90 days, and the sample weight loss rate and carbon dioxide release were tested periodically. The cumulative biodegradation rate after 90 days was calculated according to the standard formula.

[0105] Dimensional stability (heat shrinkage rate) test: Cut a 10cm×10cm square sample and mark the original size accurately; place it in an 80℃ constant temperature drying oven and let it stand for 24 hours. After taking it out and cooling it to room temperature, measure the changes in longitudinal and transverse dimensions. According to the formula: heat shrinkage rate (%) = (original size - size after test) / original size × 100%, take the average value of longitudinal and transverse dimensions as the test result.

[0106] Adhesion strength (peel strength) test: Simulate the bonding scenario of tire rubber substrate; after uniformly spraying the sample with biodegradable pressure-sensitive adhesive, it is bonded to a standard rubber test piece, rolled 3 times with a 2kg roller, and cured at room temperature for 24h; set the peel speed to 50mm / min, and conduct a 180° peel test. The average value of 3 parallel samples (unit: N / cm) is taken to characterize the adhesion strength to the inner wall of the tire.

[0107] 3. Test Result Statistics

[0108] The sound-absorbing cotton prepared in the examples and comparative examples was tested, and the test results are shown in Table 1.

[0109] Table 1 Comparison of performance test results between the examples and the comparative examples

[0110] Test sample Average sound absorption coefficient Tensile strength (N / 5cm) 90-day biodegradation rate (%) Heat shrinkage rate (%) Peel strength (N / cm) Example 1 0.72 85.6 92.3 0.8 6.2 Example 2 0.68 78.3 90.5 1.1 5.7 Example 3 0.70 82.1 91.7 0.9 6.0 Comparative Example 1 0.45 70.2 31.6 2.5 5.1 Comparative Example 2 0.53 61.4 89.8 3.2 4.3

[0111] 4. Analysis of Experimental Results

[0112] Differences in sound absorption performance: The sound absorption coefficient of the example is much higher than that of the comparative example. This is mainly due to the gradient layered structure (surface barrier, middle porous sound absorption, inner bonding), fiber activation modification, and pore optimization of biomass diatomaceous earth, which form a continuous sound wave dissipation channel. Comparative example 1 is a single-layer homogeneous structure with a disordered pore distribution, resulting in a significant reduction in sound wave dissipation efficiency. In comparative example 2, the fibers have not undergone surface modification, and the interfacial gaps between fibers are large, which cannot effectively intercept sound waves, fully conforming to the conventional rules of sound absorption of porous materials.

[0113] Differences in mechanical and dimensional stability: In the example, the chitosan fiber activation and low-temperature plasma treatment significantly improved the interfacial bonding force. With appropriate hot-pressing parameters, the hot melt adhesive bonded firmly, and the material structure was compact and dimensionally stable. In contrast, the comparative example lacked the modification process, resulting in poor compatibility between fibers, insufficient bonding force, and easy internal loosening after hot pressing. It also suffered severe shrinkage and deformation under high-temperature conditions, which is consistent with the conventional principles of interfacial modification of fiber composite materials.

[0114] Differences in environmental degradation: The examples used fully bio-based biodegradable components, with a biodegradation rate of over 90% in 90 days, and could completely disintegrate naturally after disposal; Comparative Example 1 used non-degradable hot melt adhesive, which could not be decomposed by microorganisms, with a degradation rate of only 31.6% in 90 days, which violated environmental protection requirements and conformed to the component characteristics of biodegradable materials.

[0115] Differences in practical adaptability: The peel strength of the example meets the standard, it adheres firmly to the inner wall of the tire, and does not peel or fall off after long-term use. The gradient structure takes into account both wear resistance and sound absorption and noise reduction, and is fully adaptable to the complex working conditions of the tire cavity; the comparative example has weak bonding performance and poor structural stability, and it is difficult to meet the actual use requirements.

[0116] In summary, the sound-absorbing cotton material prepared by this application through specific formulation compounding, gradient process design and reasonable parameter setting has excellent sound absorption, structural stability and full biodegradability. All performances are superior to products prepared by conventional processes and formulations, and it has extremely high practical value and environmental benefits.

[0117] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tire sound-absorbing cotton material based on bio-based biodegradable fibers, characterized in that, The raw materials, by weight percentage, include: 60-65% modified polylactic acid fiber, 20-25% hemp-based polyhydroxyalkanoate fiber, 8-10% chitosan-based ultrafine functional fiber, 5-7% starch-based biodegradable hot melt adhesive, 1-2% natural phytic acid modifier, and the balance being biomass diatomaceous earth powder, with the sum of the weight percentages of each component being 100%; the chitosan-based ultrafine functional fiber is an ultrafine fiber activated by 0.3-0.6% by mass of natural crosslinking agent.

2. The tire sound-absorbing cotton material based on bio-based biodegradable fibers according to claim 1, characterized in that, The natural crosslinking agent is a citric acid-based crosslinking agent.

3. The tire sound-absorbing cotton material based on bio-based biodegradable fibers according to claim 1, characterized in that, The modified polylactic acid fiber is a heat-resistant polylactic acid fiber with a linear density of 2.5~3.5 dtex, and the hemp-based polyhydroxyalkanoate fiber has a linear density of 0.8~1.5 dtex.

4. The tire sound-absorbing cotton material based on bio-based biodegradable fibers according to claim 1, characterized in that, The sound-absorbing cotton has a gradient layered structure, consisting of a dense surface layer, a fluffy sound-absorbing middle layer, and an inner bonding layer from top to bottom. The density of the surface dense layer is 120~150 g / m³. 2 The density of the middle layer of loose sound-absorbing material is 60~80 g / m³. 2 The density of the inner bonding layer is 90~110 g / m². 2 .

5. A preparation process for tire sound-absorbing cotton material based on bio-based biodegradable fibers, characterized in that, The tire sound-absorbing cotton material based on bio-based biodegradable fibers as described in any one of claims 1 to 4 comprises the following steps: Step 1: Activate the chitosan-based ultrafine functional fibers with a natural crosslinking agent to obtain activated chitosan-based ultrafine functional fibers; preheat the starch-based biodegradable hot melt adhesive to a molten state; mix the natural phytic acid modifier and biomass diatomaceous earth powder in a certain proportion to obtain a compound additive. Step 2: Weigh the modified polylactic acid fiber, hemp-based polyhydroxyalkanoate fiber and the activated chitosan-based ultrafine functional fiber according to the ratio, add the compounding agent and molten starch-based biodegradable hot melt adhesive, mix evenly and then perform low-temperature plasma treatment, and then loosen and open to obtain mixed fiber bundles; Step 3: The mixed fiber bundles are combed by airflow and laid in three layers according to different conveying volumes and wind pressures to form a dense surface layer, a loose sound-absorbing middle layer, and an inner bonding layer in sequence, thus obtaining a gradient fiber web blank. Step 4: Heat and press the gradient fiber web blank to heat-melt and bond the fibers of the gradient fiber web to shape it, and obtain the sound-absorbing cotton roll after cooling. Step 5: Die-cut the sound-absorbing cotton roll into customized specifications, spray biodegradable pressure-sensitive adhesive on its surface and attach release paper to obtain the finished sound-absorbing cotton material.

6. The preparation process according to claim 5, characterized in that, In step 1, the activation process of chitosan-based ultrafine functional fibers is as follows: Take the prescribed amount of chitosan-based ultrafine functional fiber, add 6 to 10 times its weight of deionized water, and ultrasonically disperse for 10 to 15 minutes. Then add 0.5% by weight of citric acid crosslinking agent solution and stir at 30 to 40°C for 20 to 30 minutes to complete the activation. After activation, filter and wash until there is no residual crosslinking agent.

7. The preparation process according to claim 5, characterized in that, In step 2, the low-temperature plasma treatment parameters are: power 80~120W, treatment time 3~5min; loosening and opening speed 200~300r / min, opening time 5~8min.

8. The preparation process according to claim 5, characterized in that, In step 3, the forming parameters for each layer are as follows: The surface dense layer is subjected to a wind pressure of 300~400Pa and a fiber conveying rate of 80~100kg / h; The middle layer of loose sound-absorbing layer uses a wind pressure of 150~250Pa and a fiber conveying rate of 40~60kg / h; The inner bonding layer uses a wind pressure of 250~300Pa and a fiber conveying rate of 60~70kg / h; The mesh laying speed for each layer is 3~5m / min.

9. The preparation process according to claim 6, characterized in that, In step 4, the specific parameters for heating and pressurizing are: temperature 130~150℃, heating time 8~12min, and pressurizing pressure 0.2~0.3MPa.

Images