Preparation process of sound-absorbing light polyurethane foam material and application thereof in automobile seat

Abstract

The application discloses a preparation process of sound-absorbing light polyurethane foam material and application of the sound-absorbing light polyurethane foam material in automobile seats, adopts a composite system of polyester polyol and polyether polyol to provide necessary rigid support and flexible resilience basis for the material, hollow glass microbeads are used as rigid particles and can be uniformly dispersed in a high-porosity polymer skeleton formed by the composite polyol and isocyanate, directly strengthen the fragile cell web, effectively prevent the collapse of the high-porosity structure in the forming process, stabilize the cell form, and the chopped fibers and the cell wall locally reinforced by the microbeads jointly construct a solid and flexible three-dimensional network, so that the material realizes excellent sound absorption and light weight at high porosity, the skeleton structure is significantly reinforced, and thus the inherent contradiction between high porosity and mechanical strength is fundamentally solved, and a more optimal balance of the three performances is realized.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more particularly to a preparation process of a sound-absorbing lightweight polyurethane foam material and its application in automobile seats. Background Technology

[0002] In modern industrial systems, especially in the automotive manufacturing sector, the requirements for material performance are becoming increasingly stringent. Lightweighting, comfort, and acoustic management have become core factors determining product competitiveness. Polyurethane foam materials, with their unique physicochemical properties such as adjustable density, good resilience, and excellent processing performance, occupy a crucial position in numerous industrial applications.

[0003] To achieve efficient sound absorption, polyurethane foam materials need to possess a high porosity and a complex, interconnected pore structure to maximize the propagation path and frictional dissipation of sound waves within the material, thereby effectively converting sound energy into heat energy. Simultaneously, to meet the automotive industry's growing demand for lightweighting, polyurethane foam materials must achieve extremely high porosity to significantly reduce their overall density, thus contributing to vehicle weight reduction and consequently lowering fuel consumption, aligning with the global trend of energy conservation and emission reduction.

[0004] However, meeting the demands for both high-efficiency sound absorption and extreme lightweighting almost inevitably requires polyurethane foam to possess extremely high porosity and an open pore structure. This significantly reduces the proportion of the polymer matrix material constituting the foam's framework in the overall volume, resulting in a sparser supporting structure and a substantial reduction in pore wall thickness. This fundamental structural change directly leads to a significant decrease in the mechanical properties of the foam material, such as compressive strength, resilience, and long-term durability. As components that directly bear the weight of occupants and endure dynamic loads for extended periods, automotive seats require their internal polyurethane foam to not only provide excellent sound absorption and noise reduction to enhance driving comfort but also possess outstanding resistance to compressive deformation, rapid rebound characteristics, and good fatigue resistance to cyclic loads. When existing materials excessively increase porosity in pursuit of ultra-high sound absorption efficiency and ultra-lightweight, although they may exhibit good acoustic performance in the initial stage, their loose internal structure makes them prone to irreversible structural collapse under long-term high-frequency compression and vibration. This leads to a rapid decrease in the foam's support capacity, loss of resilience, and deterioration of sound absorption performance, seriously affecting the comfort and safety of occupants.

[0005] Therefore, how to construct a new type of polyurethane foam material that can effectively decouple the sound absorption and lightweight advantages brought by high open area / high porosity from the inherent conflict of ensuring the macroscopic mechanical properties of the material, so as to achieve a better synergistic balance between sound absorption, lightweight and mechanical strength, has become a key challenge and a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a preparation process for a sound-absorbing lightweight polyurethane foam material and its application in automobile seats.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: a preparation process for a sound-absorbing lightweight polyurethane foam material, comprising the following steps:

[0008] S1: The composite polyol component, catalyst system, foaming agent system, cell stabilizer and acoustic performance modifier are premixed to form component A; the isocyanate component is used as component B; the composite polyol component includes polyether polyol and polyester polyol; the isocyanate component is a prepolymer containing diphenylmethane diisocyanate or pure MDI; the acoustic performance modifier contains hollow glass microspheres and / or chopped fibers;

[0009] S2: Mix component A and component B, and inject the mixed reaction mixture into a mold;

[0010] S3: The reaction mixture foams, expands, gels, and solidifies in the mold, followed by demolding;

[0011] S4: After demolding, the foam is opened, then trimmed, cut and aged.

[0012] In a preferred embodiment of the present invention, the mass ratio of the polyether polyol to the polyester polyol is controlled between 80:20 and 95:5.

[0013] In a preferred embodiment of the present invention, the NCO content of the isocyanate component is controlled between 30% and 33%; its usage is precisely regulated by the NCO index, which is set between 105 and 115.

[0014] In a preferred embodiment of the present invention, the catalyst system comprises an amine catalyst and an organometallic catalyst. The catalyst system includes triethylenediamine and dimethylcyclohexylamine as amine catalysts, and stannous octoate or dibutyltin dilaurate as organometallic catalysts. The total amount of the catalyst accounts for 0.1% to 0.5% of the total mass of the composite polyol components.

[0015] In a preferred embodiment of the present invention, the foaming agent system comprises water and a physical foaming agent; the amount of water in the foaming agent system accounts for 2.0% to 4.0% of the total mass of the composite polyol components; the physical foaming agent is selected from cyclopentane or HFC-245fa, and its addition amount accounts for 0.5% to 2.0% of the total mass of the composite polyol components; the cell stabilizer is polyether-modified polysiloxane, and its amount accounts for 0.8% to 1.5% of the total mass of the composite polyol components.

[0016] In a preferred embodiment of the present invention, the acoustic performance modifier comprises:

[0017] Hollow glass microspheres, with a particle size ranging from 10 to 50 μm and a wall thickness from 1 to 5 μm, are added at a rate of 5% to 15% of the total mass of the composite polyol components; and

[0018] The chopped fiber is selected from either chopped aramid fiber or basalt fiber, wherein the length of the chopped aramid fiber is preferably 1 to 3 mm and the diameter is 10 to 20 μm, and the amount added is 0.5% to 1.5% of the total mass of the composite polyol component.

[0019] In a preferred embodiment of the present invention, the acoustic performance modifier further comprises one of carbon black, graphite, silicate mineral powder, expanded graphite, or surface-treated nano-silica particles, and its addition amount accounts for 1% to 10% of the total mass of the composite polyol component.

[0020] In a preferred embodiment of the present invention, in step S1, component A is premixed uniformly at 20°C to 25°C, and a high-speed shear mixer is used to ensure good dispersion of the solid filler; component B is conditioned to 20°C to 23°C before use.

[0021] In S2, the mixing pressure of the high-pressure mixing head is set between 150 bar and 200 bar, and the mixing speed can reach 6000 rpm to 8000 rpm; the mold is preheated to 50°C to 70°C.

[0022] In S3, the gelation time is 5 to 10 seconds, the rise time is 60 to 120 seconds, and the demolding time is 3 to 6 minutes.

[0023] In step S4, the opening process is achieved by mechanical rolling or vacuum opening, and the opening rate of the foam reaches more than 90% after the opening process; the aging process is carried out at room temperature for 24 to 48 hours; optionally, a post-curing process is carried out in an oven at 80°C to 100°C for 2 to 4 hours.

[0024] In a preferred embodiment of the present invention, in step S2, component A includes component A1 and component A2. Component A1 is mixed with half the mass of component B to obtain component C, and component A2 is mixed with the other half the mass of component B to obtain component D. The acoustic performance modifier in component A1 consists only of chopped fibers, and the acoustic performance modifier in component A2 consists only of hollow glass microspheres. The injection method into the mold is to alternately inject components C and D in layers, with an odd number of layers and the outermost layer consisting entirely of component D.

[0025] To achieve the above objectives, the second technical solution adopted by the present invention is: the application of a sound-absorbing lightweight polyurethane foam material in automobile seats, applied to one or more of the following: the back of the headrest, the two sides of the backrest, and the center of the seat cushion.

[0026] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0027] (1) This invention provides a sound-absorbing lightweight polyurethane foam material, which adopts a composite system of polyester polyol and polyether polyol, providing the material with both necessary rigid support and flexible resilience. The hollow glass microspheres, as rigid particles, can be uniformly dispersed in the high-open-porosity polymer skeleton formed by the composite polyol and isocyanate, directly strengthening the fragile cell walls, effectively preventing the collapse of the high-porosity structure during the molding process, and stabilizing the cell morphology. The short-cut fibers, together with the cell walls locally reinforced by the microspheres, construct a strong yet flexible three-dimensional network. Compared with a sound-absorbing lightweight polyurethane foam material in the prior art, this material achieves excellent sound absorption and lightweighting with high open-porosity, while its skeleton structure is significantly strengthened, thereby fundamentally resolving the inherent contradiction between high porosity and mechanical strength, and achieving a better balance of the three properties.

[0028] (2) In this invention, the hollow glass microspheres in the surface layer optimize the acoustic impedance matching, and the short-cut fibers in the core layer improve the mechanical damping. Compared with the prior art, the hollow microspheres in the surface layer reduce the sound wave reflection by adjusting the surface acoustic impedance, promote the efficient incident sound wave, and the sound wave that enters the material then undergoes severe multiple scattering and viscoelastic dissipation caused by the vibration of the fiber-matrix interface in the porous network reinforced by the core fiber, thereby converting the sound energy into heat energy, and realizing the synergistic improvement of sound absorption performance and structural stiffness in a wide frequency band.

[0029] (3) In this invention, the chopped fibers span multiple pores and are tightly bonded to the pore walls reinforced by microspheres, jointly constructing a multi-level composite reinforcement network from macroscopic to mesoscopic to microscopic. This stable three-dimensional network not only significantly improves the tear and compression resistance of the material through fiber bridging and pull-out effects, effectively suppressing the deformation of the high-open-pore structure under stress, but also the hollow microspheres and functional fillers synergistically optimize the sound energy dissipation efficiency of the pore structure by increasing the sound wave scattering and vibration damping paths.

[0030] (4) In this invention, the outermost D component takes advantage of its smooth and dense surface characteristics to preferentially absorb and attenuate high-frequency sound waves and improve the appearance and wear resistance of the foam. The inner C component provides structural support through the fiber network, effectively handles low-frequency sound waves and disperses stress. Compared with the prior art, the layered structure introduces an acoustic impedance gradient, which causes sound waves to be reflected and scattered multiple times at the interface of layers with different densities and moduli, thereby enhancing the broadband sound absorption efficiency. At the same time, the composite effect of fibers and microspheres improves energy dissipation, so that the foam can achieve a balance between high sound absorption and mechanical durability while maintaining its lightweight properties. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the method steps of a preferred embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] Application Overview:

[0036] When existing sound-absorbing lightweight polyurethane foam materials are used in car seats, high-efficiency sound absorption requires polyurethane foam materials with high open porosity, interconnected pores, and complex channel structures to maximize sound energy dissipation; lightweight requires polyurethane foam materials with extremely high porosity; however, excessively increasing porosity and reducing density may lead to a loose foam structure, resulting in decreased compressive strength, resilience, and durability.

[0037] The applicant discovered that hollow glass microspheres significantly reduce material density while contributing a certain degree of stiffness, while chopped fibers directly enhance the material's strength and toughness. The hollow glass microspheres, acting as rigid support units, are uniformly dispersed within the cell walls, effectively improving the cell walls' resistance to bending and collapse, thus stabilizing the high-porosity structure. The chopped fibers, on the other hand, form a network within the cell, effectively transferring and dispersing stress through fiber pull-out and bridging mechanisms, inhibiting the propagation of microcracks. This combined rigidity and flexibility enhancement mechanism allows the material to maintain extremely high porosity and open-cell ratio for efficient sound absorption and lightweighting, while significantly strengthening the stability, compressive strength, and durability of its cell structure, resolving the contradiction between low density and high strength and resilience. Based on this, the present invention makes design improvements to address the inherent contradiction between high porosity and mechanical strength in existing technologies.

[0038] The preparation process of this invention mainly includes steps such as raw material preparation, mixing and foaming, curing and molding, and post-treatment, such as... Figure 1 As shown, the entire process is meticulously designed to ensure that the final foam product has stable performance and excellent quality.

[0039] The first stage is raw material preparation. All polyol components, catalysts, foaming agents, cell stabilizers, acoustic performance modifiers, and other functional additives are precisely weighed and thoroughly mixed in a premixing vessel according to the preset formula to form component A. During the mixing process, the temperature should be controlled between 20°C and 25°C, and thorough stirring should be carried out to ensure that all components are uniformly dispersed. In particular, for solid fillers such as hollow glass microspheres and chopped fibers, a high-speed shear mixer is required to ensure good suspension and dispersion in the polyol and avoid agglomeration.

[0040] The isocyanate component is stored separately as component B and conditioned to 20°C to 23°C before use. Precise temperature control is crucial for the reaction rate and the quality of the final product, as the polyurethane reaction is temperature-sensitive.

[0041] Next comes the mixing and foaming stage. The premixed components A and B are precisely metered using a metering pump and delivered to a high-pressure mixing head for high-speed mixing. The mixing pressure of the high-pressure mixing head is set between 150 and 200 bar, and the mixing speed can reach 6000 to 8000 rpm. This high-shear mixing ensures that the two reactive liquids achieve uniform mixing in a very short time, laying the foundation for the subsequent rapid foaming reaction.

[0042] The mixed reaction mixture is then injected into a preheated mold via spraying or casting. The mold, made of aluminum alloy or steel, has an internal cavity conforming to the geometry of the car seat. The mold temperature is preheated to 50°C to 70°C. A suitable mold temperature helps promote the foaming reaction while ensuring a uniform, defect-free foam surface. During casting, it is crucial to ensure the material fills the mold cavity evenly, avoiding voids or areas of uneven density.

[0043] The next stage is the curing and molding phase. The reaction mixture injected into the mold rapidly foams and expands under the combined action of the mold temperature and its own exothermic reaction, and completes gel curing within minutes. The gel time is 5 to 10 seconds, the rise time is 60 to 120 seconds, and the demolding time is 3 to 6 minutes.

[0044] During the curing process, the temperature inside the mold rises to 100°C to 130°C due to the exothermic reaction. The mold's precise temperature control system effectively guides the heat to distribute evenly, avoiding structural defects in the foam caused by localized overheating or uneven cooling. Once the foam reaches sufficient hardness and strength, it can be demolded.

[0045] The post-processing stage is crucial for optimizing foam performance. Freshly demolded foam contains a certain proportion of closed cells. To maximize its sound absorption performance, it needs to undergo an opening process. This is achieved through mechanical rolling or vacuum opening. Mechanical rolling involves passing the foam through a set of rollers with specific gaps, applying appropriate pressure to break the closed cells and create an open, interconnected structure. The rolling pressure and number of passes need to be adjusted according to the density and stiffness of the foam.

[0046] Highly active polyether polyols, such as trifunctional polyoxypropylene (POP) ether polyols with a molecular weight range of 3,000 to 5,000 and a functionality of 2.5 to 3.5, mainly provide sufficient primary hydroxyl groups to ensure efficient reaction with isocyanate components and impart good resilience and flexibility to foam.

[0047] The hydroxyl value of the polyether polyol is controlled between 28 and 45 mg KOH / g. Furthermore, to enhance the support and compression set resistance of the foam, a portion of polymeric polyol (POP) or polyester polyol is introduced into the system. For example, polyester polyols with a molecular weight between 2000 and 4000 and a functionality of 2 are used, with a hydroxyl value ranging from 35 to 50 mg KOH / g. This type of polyester polyol, by introducing more ester bonds, helps increase the proportion of hard segments in the polymer, thereby improving the compressive strength and durability of the foam. Its inherent polarity also helps improve the flame retardant properties of the foam. In the composite polyol system, the mass ratio of polyether polyol to polyester polyol is controlled between 80:20 and 95:5 to achieve the optimal balance between softness, support, and sound absorption.

[0048] As another key raw material for the reaction with the polyol component, the isocyanate component is preferably a prepolymer of diphenylmethane diisocyanate or pure MDI. MDI products containing a high proportion of the 2,4'-MDI isomer, or prepolymers obtained by prepolymerizing MDI with a small amount of polyol, are selected. These MDI isomers or prepolymers have lower vapor pressures and moderate reactivity, which helps to extend the workable time of the foaming reaction and ultimately form a foam with a uniform cell structure and good physical properties.

[0049] The NCO content of the isocyanate component is controlled between 30% and 33%, and its usage is precisely controlled by the NCO index (the molar ratio of isocyanate to hydroxyl groups multiplied by 100). In a typical formulation, the NCO index is set between 105 and 115 to ensure the reaction proceeds fully and to avoid excessive free isocyanate residue.

[0050] MDI or its prepolymer containing a high proportion of 2,4'-MDI isomers is selected, with its NCO content strictly limited to a narrow range of 30% to 33%, and its dosage precisely controlled by an NCO index of 105 to 115. The highly reactive 2,4'-MDI isomers effectively promote rapid and orderly cross-linking with the complex polyol system, forming regular rigid segments and providing initial skeletal strength for the material. The specific NCO content ensures that the reaction system has suitable flowability and a suitable reactivity window, while the prepolymer form further improves compatibility with the polyol. An NCO index slightly greater than 100 indicates a slight excess of isocyanate, aiming to fully react the hydroxyl groups of the polyol and maximize the cross-linking density.

[0051] It is possible to construct a three-dimensional network framework that combines high cross-linking density with moderate toughness. This robust framework directly supports and reinforces the high-open-porosity cell structure generated by the foaming agent and stabilized by hollow microspheres and chopped fibers. When subjected to load, the stress can be effectively dispersed through the strong cell walls, thereby fundamentally improving the macroscopic load-bearing capacity and dimensional stability of porous materials at the molecular structure level. Ultimately, it achieves a breakthrough balance in the mechanical strength of lightweight, high-porosity sound-absorbing materials.

[0052] The catalyst system is crucial for controlling the rate and selectivity of polyurethane foaming reactions. This invention employs a balanced combination of amine and organometallic catalysts. Amine catalysts, such as triethylenediamine (TEDA) and dimethylcyclohexylamine (DMCHA), are responsible for promoting the gelation and foaming reactions, respectively. TEDA primarily acts on the reaction between polyols and isocyanates to form the polyurethane backbone; DMCHA mainly catalyzes the reaction between isocyanates and water to produce carbon dioxide gas.

[0053] By precisely adjusting the ratio and total amount of these two catalysts, the gelation and foaming equilibrium points during the foaming process can be effectively controlled, thereby obtaining ideal open-cell ratio and cell structure. Organometallic catalysts, such as stannous octoate or dibutyltin dilaurate, further enhance the gelation reaction rate, especially in the presence of trace amounts of moisture in the system, effectively reducing the occurrence of side reactions. The total amount of catalyst used accounts for 0.1% to 0.5% of the total mass of the composite polyol components.

[0054] A composite catalyst system consisting of triethylenediamine, dimethylcyclohexylamine, and stannous octoate or dibutyltin dilaurate was adopted, and its total amount was precisely controlled between 0.1% and 0.5% of the total mass of the composite polyol components. The amine catalyst and the organometallic catalyst preferentially catalyze the foaming reaction and the gelation reaction, respectively, thereby achieving separate regulation of the foaming rate and the molecular chain growth / crosslinking rate.

[0055] This ensures that the gelation and curing rate of the polymer skeleton is precisely matched during the vaporization of the high proportion of physical foaming agent and the rapid expansion of the cells. This avoids cell collapse or merging due to slow gelation, as well as cell cracking or excessive internal stress caused by excessively rapid gelation. This highly coordinated reaction kinetics ultimately leads to an ideal foam structure with high porosity, uniform pore size, and intact and strong cell walls. This stable and uniform microstructure not only provides an efficient dissipation path for sound waves but also serves as a robust support, allowing the reinforcing effects of hollow glass microspheres and chopped fibers to be fully utilized. This fundamentally and synergistically improves the macroscopic mechanical integrity and durability of the material while maintaining its lightweight and high sound absorption performance.

[0056] Specifically, key parameters such as molecular weight, functionality, and hydroxyl value of polyether polyols and polyester polyols were defined, and their mass ratio was strictly controlled within a narrow range of 80:20 to 95:5. A higher proportion of long-chain flexible polyether polyols constituted the main framework of the material, ensuring that the foam products had excellent flexibility and high resilience, laying the foundation for achieving low density and high open-cell rate. Meanwhile, a small amount of polyester polyols with regular structure and strong polarity served as rigid reinforcing units, which could effectively improve the cohesive strength and hardness of the polymer.

[0057] The flexible long chains of polyether polyols form a continuous phase, ensuring the overall deformation recovery capability of the material and avoiding the brittleness that may be present in pure polyester systems. Meanwhile, the dispersed polyester polyol molecular chains significantly enhance the rigidity and mechanical integrity of the polymer network through stronger intermolecular forces and hydrogen bonding. This combination of rigidity and flexibility results in a foam skeleton with extremely high porosity for optimized sound absorption and lightweight properties, while the cell walls themselves possess higher strength and creep resistance. This directly strengthens the stability of the high-porosity structure at the microscopic level, fundamentally synergistically balancing the inherent contradictions between sound absorption, lightweight, and mechanical properties.

[0058] In this invention, the foaming agent system primarily achieves chemical foaming through the reaction of water with isocyanate to generate carbon dioxide. Simultaneously, a physical foaming agent can be used to adjust the foam density and cell structure. The amount of water used accounts for 2.0% to 4.0% of the total mass of the composite polyol components. Water is not only the main chemical foaming agent, but the urea bond structure generated by its reaction also helps to improve the hardness and thermal stability of the foam.

[0059] The amount of water used is controlled within a moderate range to provide the main foaming power, while a specific physical blowing agent is selected as a supplement, and a corresponding proportion of polyether-modified polysiloxane is matched as a cell stabilizer. The initial effect is that water reacts with isocyanate to generate carbon dioxide, which constitutes the basic gas source, while the physical blowing agent vaporizes under the exothermic reaction, together ensuring the formation of a low-density foam with high porosity; the cell stabilizer, by regulating surface tension, initially prevents cell merging or collapse.

[0060] The stabilizer forms an elastic film at the bubble expansion interface, and its effect matches the polymerization rate regulated by the catalyst, ensuring a dynamic balance between the two key processes of physical blowing agent vaporization and expansion and polymer gel solidification. This synergistic effect promotes the formation of a three-dimensional network structure with uniform pore size, high porosity, and thin, intact intercellular ribs.

[0061] Not only does it maximize the efficiency of sound wave energy dissipation and the lightweight nature of the material, but its complete ribbed walls also serve as a load-bearing skeleton, allowing the reinforcing effect of hollow microspheres and short-cut fibers in the acoustic modulator to adhere firmly and transfer stress efficiently. This fundamentally and synergistically strengthens the integrity and mechanical strength of the material at the microstructural level, achieving an excellent balance between sound absorption, lightweight, and load-bearing performance.

[0062] In a preferred embodiment of the present invention, to further reduce the density of the foam and optimize the cell structure, an appropriate amount of physical foaming agent, such as cyclopentane or HFC-245fa, can be added. These physical foaming agents vaporize under exothermic reaction conditions, playing an auxiliary foaming role and helping to form finer and more uniform cells. The amount of physical foaming agent added is controlled between 0.5% and 2.0% of the total mass of the composite polyol components.

[0063] Cell stabilizers, specifically silicone surfactants, play a crucial role in this invention. They effectively reduce the surface tension at the liquid-phase interface, promote the uniform dispersion and stabilization of bubbles, and prevent premature bubble breakage or coalescence, thereby forming a uniform and fine cell structure. Simultaneously, specific silicone surfactants can assist in cell opening during the later stages of foaming, ensuring the acquisition of sound-absorbing foam with a high open-cell ratio. Preferred cell stabilizers include polyether-modified polysiloxanes, used in amounts ranging from 0.8% to 1.5% of the total mass of the composite polyol components.

[0064] Acoustic performance modifiers are key to achieving excellent sound absorption performance in this invention. This invention significantly improves the sound absorption coefficient of foam by introducing specific types of porous or fibrous fillers, while maximizing the maintenance of its lightweight characteristics. In one specific embodiment, this invention uses hollow glass microspheres as the main acoustic performance modifier. Hollow glass microspheres possess extremely low density, good chemical inertness, and excellent high-temperature resistance.

[0065] Its hollow internal structure significantly increases the sound wave scattering interface within the foam material. Simultaneously, due to its low density, foam with added hollow glass microspheres maintains a lower overall density for the same volume, thus achieving synergistic optimization of lightweighting and sound absorption performance. The preferred hollow glass microspheres have a particle size range of 10 to 50 μm, a wall thickness of 4-6 μm, and are added at 5% to 15% of the total mass of the composite polyol components. Furthermore, to further improve sound wave loss within the material, a small amount of chopped aramid fibers or basalt fibers can be introduced into the system. These fiber materials can form complex microstructures within the foam matrix, increasing the tortuosity of the sound wave propagation path, thereby enhancing the sound absorption effect in the high-frequency range.

[0066] The length of the chopped aramid fibers is preferably 1 to 3 mm, and the diameter is 10 to 20 μm. The addition amount is controlled at 0.5% to 1.5% of the total mass of the composite polyol components. In addition, in order to achieve a specific acoustic frequency response curve, carbon black, graphite, or silicate mineral powder with a specific particle size distribution can be introduced, with the addition amount between 1% and 5% of the total mass of the composite polyol components. These fillers can adjust the acoustic impedance matching inside the foam, thereby optimizing the sound absorption performance in a specific frequency range.

[0067] Other functional additives can be formulated according to the application requirements of automotive seats. For example, to meet the stringent flame retardant standards for automotive interiors, phosphorus-based flame retardants, such as triphosphates or triethyl phosphates, can be added, accounting for 5% to 10% of the total mass of the composite polyol components. Antioxidants and UV absorbers can also be added in appropriate amounts to improve the weather resistance and service life of the foam, preventing yellowing or performance degradation under long-term use or light exposure. The amount of these additives is generally between 0.1% and 0.5% of the total mass of the composite polyol components.

[0068] Hollow glass microspheres with specific particle size and wall thickness serve as the core lightweight reinforcement, while chopped fibers with limited length and diameter form the macroscopic framework. Functional fillers can be further introduced for performance fine-tuning. The hollow microspheres effectively reduce material density while locally reinforcing the cell walls with their rigid shells. The chopped fibers, with their high modulus, construct a diffusely distributed fiber network within the foam. Optional functional fillers can further adjust acoustic impedance or enhance damping.

[0069] Short-cut fibers span multiple cell pores and are tightly bonded to the cell walls, which are locally reinforced by microspheres, together constructing a multi-level composite reinforcement network from macroscopic to mesoscopic to microscopic. This robust three-dimensional network not only significantly improves the material's tear and compression resistance through fiber bridging and pull-out effects, effectively suppressing the deformation of the high-open-pore structure under stress, but also, through the synergistic optimization of the acoustic energy dissipation efficiency of the cell structure by increasing sound wave scattering and vibration damping paths, the hollow microspheres and functional fillers further enhance this efficiency.

[0070] Multi-scale synergy fundamentally solves the structural fragility problem of high-porosity materials, enabling the material to achieve mechanical strength and dimensional stability far exceeding those of conventional foams while possessing excellent sound absorption performance and extremely low density.

[0071] For lightweight foams with low density, lower pressure and one-time rolling can be used. Vacuum opening involves applying negative pressure to the foam in a vacuum chamber, causing the cells to expand and rupture instantaneously. After opening, the foam's open-cell ratio should reach over 90%. Subsequently, the foam is trimmed and cut to obtain the final dimensions and shape that meet the design requirements of automotive seats. Finally, the cut foam undergoes an aging treatment, being left at room temperature for 24 to 48 hours to ensure that residual reactions within the foam are complete and that its physical and mechanical properties and dimensional stability reach their optimal state. In certain special applications, to further improve the physical and mechanical properties of the foam, it can be subjected to a short-term post-curing treatment in an oven at 80°C to 100°C.

[0072] Premixing ensures uniform dispersion of various additives, including acoustic modifiers, in the polyol matrix; high-pressure mixing enables components A and B to achieve sufficient molecular-level collision and reaction initiation in a very short time; mold heating provides a stable environment for controllable curing; and pore opening treatment directly optimizes the permeability of the foam structure.

[0073] The intense shearing action of high-pressure mixing ensures that the chopped fibers and hollow microspheres are evenly distributed in the rapidly foaming polymer melt, avoiding agglomeration and laying the foundation for building a homogeneous reinforced network. At the same time, this mixing method works synergistically with the catalytic system to ensure that the reactants begin to nucleate and foam rapidly and uniformly the moment they are injected into the mold. The thermal field of the mold further guides the orderly gelation and solidification of the polyurethane network, ultimately forming a stable three-dimensional skeleton with microspheres embedded in the cell walls and fibers bridging the cells.

[0074] While ensuring the overall strength of the skeleton, selectively opening some closed pores greatly optimizes the material's ability to resist sound wave flow loss. The entire process chain is interconnected, ultimately transforming all the material science advantages from molecular design to microstructure enhancement into a complete and repeatable synergistic balance of sound absorption, lightweight, and high mechanical strength on a macroscopic scale in the product.

[0075] In S2, component A includes components A1 and A2. Component A1 is mixed with half the mass of component B to obtain component C, and component A2 is mixed with the other half the mass of component B to obtain component D. The acoustic performance modifier in component A1 is only chopped fiber, and the acoustic performance modifier in component A2 is only hollow glass microspheres. The injection method is to inject components C and D alternately in layers, with an odd number of layers and the outermost layer being component D.

[0076] Short-cut fibers contribute to enhancing the mechanical strength and internal damping loss of the foam, while hollow glass microspheres provide the basis for lightweighting and sound wave scattering. The outer layer of component D utilizes the uniform distribution of hollow glass microspheres to achieve a gradual transition in acoustic impedance with the air medium, reducing the loss of sound wave incident reflection. At the same time, the short-cut fibers of the inner layer C induce multiple scattering and viscous dissipation through the fiber-matrix interface. Sound waves are efficiently attenuated along the thickness direction in the gradient porous network, thereby optimizing the broadband sound absorption coefficient while taking into account structural integrity.

[0077] The hollow glass microspheres in component D achieve material lightweighting and basic sound wave scattering, while the chopped fibers in component C provide skeletal reinforcement and damping. As an acoustic matching layer, component D contains hollow glass microspheres that enable a gradual transition of acoustic impedance from air to foam material, effectively reducing sound wave reflection loss at the interface and allowing more sound energy to enter the material interior. Subsequently, the chopped fibers in component C convert sound energy into heat energy through multiple scattering of sound waves and viscous friction at the fiber-matrix interface, thereby synergistically achieving high sound energy dissipation and high sound absorption coefficient over a wide frequency band.

[0078] The hollow glass microspheres in the surface layer optimize acoustic impedance matching, while the short-cut fibers in the core layer enhance mechanical damping. The hollow microspheres in the surface layer reduce sound wave reflection by adjusting the surface acoustic impedance, promoting efficient sound wave incidence. The sound waves entering the material then undergo intense multiple scattering and viscoelastic dissipation caused by fiber-matrix interface vibration in the porous network reinforced by the core fiber, thereby converting sound energy into heat energy. This achieves a synergistic improvement in sound absorption performance and structural stiffness over a wide frequency band.

[0079] The D-component layering enhances the incident sound efficiency, while the C-component layering extends the sound wave propagation path. The dense micropores on the surface of the D-component, formed by hollow glass microspheres, achieve a gradual matching of acoustic impedance with the air medium, effectively reducing the reflection loss of the incident sound wave. Subsequently, the sound wave enters the large pore space formed by chopped fibers in the C-component layer. The extended sound wave propagation path, together with the chopped fibers, significantly enhances the multiple reflections and scattering of the sound wave within the pores, as well as the viscous friction effect with the pore walls and fibers. This efficiently converts sound energy into heat energy, achieving highly efficient sound absorption, especially in the mid-to-low frequency range, across a wide frequency band.

[0080] The sound-absorbing lightweight polyurethane foam material of this invention, through the precise control of its components and process parameters, exhibits significantly superior overall performance compared to traditional polyurethane foam, particularly in sound absorption and lightweighting. Its application in automotive seats, such as as internal filling material for seat back cushions, seat cushions, headrests, and side wing supports, effectively absorbs cabin noise, especially mid-to-high frequency noise, thereby significantly improving ride comfort. Simultaneously, its lightweight nature helps reduce overall vehicle weight and fuel consumption, meeting the stringent energy-saving and environmental protection requirements of the current automotive industry. Its excellent mechanical properties, such as good resilience, resistance to compression set, and durability, ensure that the seat maintains comfortable support and a good appearance even after long-term use.

[0081] Example 1

[0082] The sound-absorbing lightweight polyurethane foam prepared in this embodiment comprises a composite polyol component consisting of 88 parts by mass of a polyether polyol with a molecular weight of 4800 and a functionality of 3 (hydroxyl value 35 mg KOH / g) and 12 parts by mass of a polyester polyol with a molecular weight of 3000 and a functionality of 2 (hydroxyl value 40 mg KOH / g). The isocyanate component is an MDI prepolymer with an NCO content of 32.5%. The catalyst system consists of 0.25 parts by mass of Dabco33-LV, 0.15 parts by mass of DabcoDMCHA, and 0.1 parts by mass of stannous octoate. The blowing agent is 3.0 parts by mass of water and 1.0 part by mass of cyclopentane. The cell stabilizer is 1.2 parts by mass of polyether-modified polysiloxane. The flame retardant is 7.0 parts by mass of TCPP. All components are based on a total mass of 100 parts by mass of the composite polyol component. The NCO index is set to 110.

[0083] The preparation process parameters are as follows: the composite polyol component, catalyst system, foaming agent system, cell stabilizer and acoustic performance modifier are premixed to form component A; the isocyanate component is prepared separately as component B.

[0084] Component A is premixed uniformly at 23°C, while component B is kept at 22°C. Components A and B are mixed using a high-pressure mixing head (180 bar, 7000 rpm) and poured into a mold preheated to 60°C. Specifically, the mixing and pouring process involves mixing components A and B in S2 to obtain components C and D. The difference between components C and D lies in the following: the mass ratio of the catalyst system is 4:6, the mass ratio of the foaming agent is 4.5:5.5, and the mass ratio of the cell stabilizer is 5:7. Component C contains only chopped fibers as the acoustic performance modifier, while component D contains only hollow glass microspheres. The mass ratio of the composite polyol component, isocyanate, and flame retardant is 5:5. Except for the acoustic performance modifier, the concentrations of various components in the other components are consistent. For example, components C and D contain 44 parts by mass of polyether polyol and 6 parts by mass of polyester polyol, respectively. The hollow glass microspheres have a mass ratio of 8.0 parts and a particle size of 40 μm, the short-cut aramid fibers have a mass ratio of 1.0 parts and a length of 2 mm, and the wall thickness of the hollow glass microspheres is 2 μm.

[0085] The injection molding method is a stacked injection, with an odd number of layers, and the outermost layers are all of component D. There are 5 layers in total, with each layer of component C having a consistent mass, and each layer of component D having a consistent mass.

[0086] The gel time was 8 seconds, the rise time was 95 seconds, and the demolding time was 4 minutes. After demolding, the foam was immediately subjected to two roll forming processes to open the holes, and then aged for 48 hours at 25°C and 50% relative humidity.

[0087] Example 2:

[0088] The difference between this embodiment and Embodiment 1 is that the wall thickness of the hollow glass microspheres is 4μm, while the rest are the same.

[0089] Example 3:

[0090] The difference between this embodiment and Embodiment 1 is that the wall thickness of the hollow glass microspheres is 6μm, while the rest are the same.

[0091] Example 4:

[0092] The difference between this embodiment and Embodiment 1 is that the wall thickness of the hollow glass microspheres is 8μm, while the rest are the same.

[0093] Example 5:

[0094] The difference between this embodiment and Embodiment 1 is that the wall thickness of the hollow glass microspheres is 10 μm, while the rest are the same.

[0095] Example 6:

[0096] The difference between this embodiment and embodiment 3 is that the number of layers is 3, while the rest are the same.

[0097] Example 7:

[0098] The difference between this embodiment and embodiment 3 is that the number of layers is 7, while the rest are the same.

[0099] Example 8:

[0100] The difference between this embodiment and embodiment 3 is that the number of layers is 9, while the rest are the same.

[0101] Example 9:

[0102] The difference between this embodiment and embodiment 3 is that the number of layers is 11, while the rest are the same.

[0103] Comparative Example 1:

[0104] Comparative Example 1 provides a polyurethane foam material, the specific preparation method of which is as follows:

[0105] The polyurethane foam prepared in this comparative example comprises 88 parts by mass of a polyether polyol with a molecular weight of 4800 and a functionality of 3 (hydroxyl value 35 mg KOH / g) and 12 parts by mass of a polyester polyol with a molecular weight of 3000 and a functionality of 2 (hydroxyl value 40 mg KOH / g). The isocyanate component is an MDI prepolymer with an NCO content of 32.5%. The catalyst system consists of 0.25 parts by mass of Dabco33-LV, 0.15 parts by mass of DabcoDMCHA, and 0.1 parts by mass of stannous octoate. The blowing agent is 3.0 parts by mass of water and 1.0 part by mass of cyclopentane. The cell stabilizer is 1.2 parts by mass of polyether-modified polysiloxane. The flame retardant is 7.0 parts by mass of TCPP.

[0106] The preparation process parameters are as follows: The composite polyol component, catalyst system, foaming agent system, and cell stabilizer are premixed to form component A; the isocyanate component is prepared separately as component B; component A is premixed uniformly at 23℃, and the temperature of component B is controlled at 22℃. Components A and B are mixed using a high-pressure mixing head (pressure 180 bar, speed 7000 rpm) and poured into a mold preheated to 60℃.

[0107] The gel time was 8 seconds, the rise time was 95 seconds, and the demolding time was 4 minutes. After demolding, the foam was immediately subjected to two roll forming processes to open the holes, and then aged for 48 hours at 25°C and 50% relative humidity.

[0108] Tensile strength and noise attenuation coefficient were tested on samples of equal mass from Examples 1-9 and Comparative Example 1. The standard for tensile strength was GB / T9641, and the standard for noise attenuation coefficient was ISO10534-2. The test data are shown in Table 1.

[0109] Table 1. Tensile strength and noise attenuation coefficient test data for Examples 1-9 and Comparative Example 1.

[0110] Data source Tensile strength (kPa) Noise attenuation factor (NRC) Example 1 150 0.68 Example 2 157 0.72 Example 3 161 0.75 Example 4 158 0.73 Example 5 152 0.70 Example 6 159 0.71 Example 7 166 0.80 Example 8 163 0.76 Example 9 161 0.72 Comparative Example 1 125 0.55

[0111] As shown in Table 1, the tensile strength and noise attenuation coefficient of Examples 1-9 are greater than those of Comparative Example 1, and the mechanical strength and sound absorption of Examples 1-9 are greater than those of Comparative Example 1. This application has advantages.

[0112] In Examples 1-5, as the wall thickness of the hollow glass microspheres gradually increases, both the tensile strength and the noise attenuation coefficient first increase and then decrease. This is because when the wall thickness increases from very thin, the compressive strength of the microspheres significantly improves, allowing them to remain intact during mixing and foaming, and more effectively transfer stress to the polyurethane matrix through the interface, thus playing a reinforcing role and increasing the tensile strength. Simultaneously, the intact microspheres with a certain stiffness act as scatterers, more effectively reflecting and scattering sound waves, improving the attenuation coefficient. However, when the wall thickness continues to increase beyond a critical point, the density of the microspheres increases, and their flexibility decreases. The difference in modulus between the microspheres and the polymer matrix during deformation becomes too large, leading to stress concentration and debonding at the interface, which becomes a structural defect point, reducing the tensile strength. Acoustically, the excessively thick wall causes a large difference in acoustic impedance between the microspheres and air, hindering the coupling of sound waves into the material for dissipation, and reducing the number of acoustic action points per unit mass, resulting in a decrease in overall noise attenuation efficiency. Example 3 is the preferred embodiment.

[0113] In Examples 3 and 6-9, as the number of layers gradually increases, both tensile strength and noise attenuation coefficient first increase and then decrease. This is because, with a moderate increase in the number of layers, the interlocking structure formed at the interface enhances the integrity of the cell network, the directional distribution of chopped fibers at more interfaces improves stress transfer efficiency, and the gradient transition of acoustic impedance is smoother, reducing the reflection loss of sound waves between layers, thereby synergistically improving tensile strength and noise attenuation coefficient. However, when the number of layers is too large, the interlayer interface density increases significantly, introducing a large number of stress concentration points and weakening the overall structural strength. At the same time, too many interfaces can cause sound wave scattering and phase cancellation effects, disrupting the continuity of sound energy transmission, resulting in a simultaneous decline in mechanical and acoustic properties. The preferred embodiment is Example 7.

[0114] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A preparation process for a sound-absorbing lightweight polyurethane foam material, characterized in that, Includes the following steps: S1: The composite polyol component, catalyst system, foaming agent system, cell stabilizer and acoustic performance modifier are premixed to form component A; the isocyanate component is used as component B; the composite polyol component includes polyether polyol and polyester polyol; the isocyanate component is a prepolymer containing diphenylmethane diisocyanate or pure MDI; the acoustic performance modifier contains hollow glass microspheres and / or chopped fibers; S2: Mix component A and component B, and inject the mixed reaction mixture into a mold; S3: The reaction mixture foams, expands, gels, and solidifies in the mold, followed by demolding; S4: After demolding, the foam is opened, then trimmed, cut and aged.

2. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: The mass ratio of the polyether polyol to the polyester polyol is controlled between 80:20 and 95:

5.

3. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: The NCO content of the isocyanate component is controlled between 30% and 33%. Its usage is precisely controlled by the NCO index, which is set between 105 and 115.

4. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: The catalyst system includes amine catalysts and organometallic catalysts. The catalyst system contains triethylenediamine and dimethylcyclohexylamine as amine catalysts, and stannous octoate or dibutyltin dilaurate as organometallic catalysts. The total amount of the catalyst accounts for 0.1% to 0.5% of the total mass of the composite polyol components.

5. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: The foaming agent system comprises water and a physical foaming agent; the amount of water in the foaming agent system accounts for 2.0% to 4.0% of the total mass of the composite polyol components; the physical foaming agent is selected from cyclopentane or HFC-245fa, and its addition amount accounts for 0.5% to 2.0% of the total mass of the composite polyol components; the cell stabilizer is polyether-modified polysiloxane, and its amount accounts for 0.8% to 1.5% of the total mass of the composite polyol components.

6. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: The acoustic performance modifier comprises: Hollow glass microspheres, with a particle size ranging from 10 to 50 μm and a wall thickness from 1 to 5 μm, are added at a rate of 5% to 15% of the total mass of the composite polyol components; and The chopped fiber is selected from either chopped aramid fiber or basalt fiber, wherein the length of the chopped aramid fiber is preferably 1 to 3 mm and the diameter is 10 to 20 μm, and the amount added is 0.5% to 1.5% of the total mass of the composite polyol component.

7. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 6, characterized in that: The acoustic performance modifier also includes one of carbon black, graphite, silicate mineral powder, expanded graphite, or surface-treated nano-silica particles, and its addition amount accounts for 1% to 10% of the total mass of the composite polyol components.

8. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: In S1, component A is premixed uniformly at 20°C to 25°C, and a high-speed shear mixer is used to ensure good dispersion of the solid filler; component B is conditioned to 20°C to 23°C before use. In S2, the mixing pressure of the high-pressure mixing head is set between 150 bar and 200 bar, and the mixing speed can reach 6000 rpm to 8000 rpm; the mold is preheated to 50°C to 70°C. In S3, the gelation time is 5 to 10 seconds, the rise time is 60 to 120 seconds, and the demolding time is 3 to 6 minutes. In step S4, the opening process is achieved by mechanical rolling or vacuum opening, and the opening rate of the foam reaches more than 90% after the opening process; the aging process is carried out at room temperature for 24 to 48 hours; optionally, a post-curing process is carried out in an oven at 80°C to 100°C for 2 to 4 hours.

9. The preparation process of a sound-absorbing lightweight polyurethane foam material according to claim 1, characterized in that: In S2, component A includes component A1 and component A2. Component A1 is mixed with half the mass of component B to obtain component C, and component A2 is mixed with the other half the mass of component B to obtain component D. The acoustic performance modifier in component A1 consists only of chopped fibers, and the acoustic performance modifier in component A2 consists only of hollow glass microspheres. The injection method into the mold is to alternately inject components C and D in layers, with an odd number of layers and the outermost layer consisting entirely of component D.

10. The application of a sound-absorbing lightweight polyurethane foam material in automobile seats, based on the preparation process of the sound-absorbing lightweight polyurethane foam material according to any one of claims 1-9, characterized in that, It can be applied to one or more of the following: the back of the headrest, the two sides of the backrest, and the center of the seat cushion.

Images