Preparation method and application of PET non-woven fabric containing low-temperature viscoelastic filaments

Abstract

The invention discloses a preparation method and application of PET non-woven fabric containing low-temperature viscoelastic filaments, and belongs to the technical field of PET materials.The preparation method comprises the steps that polymer slices are fed into a screw extruder and are subjected to melting, extruding, filtering, metering and spraying out through a spinneret plate, one part of filament tows are cooled and drafted through airflow, and the other part of filament tows are only cooled; the two parts of filament tows are mixed together at the coagulation net curtain and are subjected to lapping, needling and reinforcing to form the non-woven fabric; polymer slices are respectively fed into two screw extruders, the screw extruder A is cooled and drafted by air flow, the extruder B is only cooled, PET filament tows extruded by the two screw extruders are mixed together at a net condensing curtain, and the mixture is subjected to lapping, needling and reinforcing to form non-woven fabric; taking low-temperature viscoelastic continuous filament tows and polyester filament tows, mixing the continuous filament tows and the polyester filament tows together at a coagulation web curtain, and performing lapping, needling and reinforcing to form a non-woven fabric; the PET non-woven fabric containing the low-temperature viscoelastic filaments, which is prepared by the three methods, is prepared into automobile parts by a molding method of mould pressing.

Description

Technical Field

[0001] This invention belongs to the field of PET material technology, specifically relating to a method for preparing and applying PET nonwoven fabric containing low-temperature viscoelastic filaments. Background Technology

[0002] With rapid economic development and improved living standards, the automotive industry has also grown rapidly. People's demands for automotive quality have expanded beyond the vehicle's functionality and appearance to include the aesthetics of the interior, ride comfort, and overall NVH (Noise, Vibration, Harshness) performance. Against this backdrop, flexible textile materials, due to their lightweight, design flexibility, and excellent acoustic and vibration damping properties, are widely used in automotive interior and exterior components, such as wheel arches, trunk liners, underbody protection covers, seat back panels, and carpet systems. These textile-based automotive parts, with their porous structure and inter-fiber friction, can effectively absorb and attenuate sound waves and vibration energy, thereby significantly reducing the impact of noise generated during vehicle operation on the surrounding environment and passengers.

[0003] Currently, the filament nonwoven fabrics used in automotive parts are mostly composites of low-melting-point polymers and conventional polyethylene terephthalate (PET). These materials typically achieve fiber bonding in two ways: one is by using the low-melting-point polymer as the sheath of the PET fibers, forming a core-sheath composite fiber; the other is by mixing the low-melting-point polymer as a separate bonding fiber with conventional PET fibers, then melting the low-melting-point component through hot air or hot rolling processes to form bonding nodes, thereby giving the nonwoven fabric a certain mechanical strength and structural integrity. Commonly used low-melting-point bonding materials include modified copolyesters (such as Co-PET), polybutylene terephthalate (PBT), polypropylene (PP), polyamide 6 (PA6), and polyethylene (PE), whose melting points are generally lower than conventional PET (approximately 255℃), typically between 110℃ and 180℃.

[0004] However, with the rapid development of the automotive industry, especially new energy vehicles, the requirements for the heat resistance of materials are becoming increasingly stringent. For example, existing low-melting-point bonded nonwoven materials face severe challenges in components near heat sources such as the engine compartment, exhaust system, or battery pack, as well as components that require high-temperature coating and drying processes (temperatures can reach 180℃-200℃). Because their heat resistance is limited by the melting point of the bonding material, when the operating temperature exceeds 150℃, the material is prone to significant thermal shrinkage (typically greater than 5%), leading to structural deformation, dimensional instability, and even delamination failure. This not only affects the appearance and assembly of the components but also weakens their acoustic and mechanical properties. Furthermore, the introduction of low-melting-point polymers is often accompanied by a decrease in material rigidity and aging resistance, limiting their application in high-end automotive components.

[0005] Therefore, developing a new type of automotive nonwoven material that retains the excellent mechanical properties and processing characteristics of traditional PET nonwoven fabrics while possessing higher heat resistance and lower heat shrinkage has become a key technical problem that the industry urgently needs to solve. This invention aims to introduce a filament component with specific low-temperature viscoelastic behavior to achieve effective bonding at relatively low temperatures while significantly improving the high-temperature dimensional stability and durability of the finished nonwoven fabric, thereby expanding its application potential in automotive components operating under high-temperature conditions. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this application provides a method for preparing and applying PET nonwoven fabric containing low-temperature viscoelastic filaments. This method solves the technical problems existing in the prior art, such as the heat resistance temperature of filament nonwoven fabric materials being limited by the melting point of the bonding material due to the presence of low-melting-point fibers, and shrinkage exceeding 5% after exceeding 150°C. By using low-temperature viscoelastic PET filaments to replace traditional bonding fibers such as PP, PE, and modified PET, 100% PET nonwoven fabric can be prepared.

[0007] The technical solution adopted in this invention is as follows: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments, using any one of the following three preparation methods: First preparation method: Polyester chips are fed into a spinning device and melted, extruded, filtered, and metered before entering the spinning assembly for spinning. The spinning assembly uses a segmented or side-by-side spinneret to distribute the melt to different spinneret holes, ensuring that the molten material is ejected as two independent filament bundles. 10%-80% of the filament bundles are cooled and stretched by airflow, while 20%-90% of the filament bundles are only cooled. The two filament bundles are mixed together at the condensing screen and then reinforced by web laying and needle punching to become a PET nonwoven fabric containing low-temperature viscoelastic filaments. The second preparation method: Polyester chips are fed into two screw extruders, screw extruder A and screw extruder B, respectively. Screw extruder A extrudes 10%-80% of the filament bundles through air cooling and stretching, while screw extruder B extrudes 20%-90% of the filament bundles through cooling only. The filament bundles extruded by air cooling and stretching and the filament bundles extruded by cooling only are mixed together at the condensing screen, and after being reinforced by web laying and needle punching, they become PET nonwoven fabric containing low-temperature viscoelastic filaments. The third preparation method: 10-80% polyester filament and 20-90% low-temperature viscoelastic filament are mixed in yarn bobbins during unwinding, and then mixed together at the condensing screen. After being reinforced by needle punching, it becomes a PET nonwoven fabric containing low-temperature viscoelastic filament.

[0008] Preferably, in the first preparation method, 10%-80% of the filament bundles are cooled and drawn by airflow. Specifically, an airflow cooling and drawing system is used to cool and draw the filament bundles by airflow, so that they are fully oriented and crystallized to form high-strength and high-heat-resistant PET filaments. The filament bundles sprayed from the spinneret have a single filament linear density of less than 18 dtex after being cooled by airflow.

[0009] Preferably, in the first preparation method, 20%-90% of the filament bundles are only cooled to control their crystallinity. The filament bundles have the property of bonding fibers, thus becoming low-temperature viscoelastic filaments.

[0010] Preferably, in the second preparation method, the screw extruder A extrudes 10%-80% of the filament bundle through airflow cooling and stretching. Specifically, the airflow cooling and stretching system is used to cool and stretch the filament bundle to fully orient and crystallize it, forming high-strength and high-heat-resistant PET filaments.

[0011] Preferably, in the second preparation method, the screw extruder B only extrudes 20%-90% of the filament bundles after cooling, controlling its crystallinity. The filament bundles have the property of bonding fibers, thus becoming low-temperature viscoelastic filaments.

[0012] Preferably, in the third preparation method, the low-temperature viscoelastic filament is a low-orientation, low-stretch continuous filament; the low-orientation, low-stretch continuous filament is one or more of UDY, MOY, and POY.

[0013] Preferably, in the third preparation method, the polyester filament is a highly oriented, highly crystalline, highly tensile, and highly strong filament; the highly oriented, highly crystalline, highly tensile, and highly strong filament is one or more of HOY, FOY, FDY, DTY, ATY, and HMLS.

[0014] Preferably, the pressure used in the airflow cooling stretching is 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized.

[0015] Preferably, the mixing at the condensing screen specifically involves thorough mixing and uniform dispersion via airflow above the condensing screen, followed by deposition onto the moving condensing screen or leather screen to form a uniform long filament fiber web. After web laying and needle punching reinforcement, the web achieves a weight of 200-2000 g / m². 2 It is a non-woven fabric.

[0016] This application also discloses the application of PET nonwoven fabric containing low-temperature viscoelastic filaments prepared by any of the above-mentioned preparation methods in the preparation of molding materials. The PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240°C for 20-180 seconds. During this heating process, steam at 160-240°C and a steam pressure between 5Pa and 20Pa can be introduced, or steam can be left unintroduced. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. The molding material is used to prepare automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

[0017] Explanation of the principle: The low-temperature viscoelastic filament used in this invention initially has an amorphous structure. The amorphous modified polyethylene terephthalate (PET) fiber is in a cis conformation. When heated, the modified PET fiber self-bonds at the intersections with other PET fibers, resulting in crystallization and a transformation to an inverse conformation. Therefore, it can replace adhesive fiber materials such as PP and BICO. After being formed into parts by heating, the low-temperature viscoelastic filament does not exhibit thermal crystallization peaks in the heated filament, meaning that the amorphous region has been completely transformed into a crystalline region. Therefore, it exhibits high temperature resistance and better dimensional stability during the high-temperature heating stage after the nonwoven fabric is formed. After being heated at 180°C for 72 hours, the shrinkage rate of this nonwoven material is less than 1%. Under environmental storage conditions, the strength, toughness, and elasticity of the nonwoven material do not change.

[0018] Beneficial effects: 1. This application discloses a method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments and its application. The PET nonwoven fabric is used to prepare molding materials, which are used in automotive parts, aiming to provide excellent acoustic performance and dimensional stability. 2. The method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments disclosed in this application significantly improves thermal stability, meets the thermal stability requirements of different customers, increases the maximum heat resistance temperature from 105℃ to 150-180℃, and can use 100% recyclable granules to produce fibers. 3. The PET nonwoven fabric containing low-temperature viscoelastic filaments disclosed in this application uses low-temperature viscoelastic PET filaments to replace traditional adhesive fibers such as PP, PE, and modified PET to prepare 100% PET nonwoven fabric; 4. The preparation method and application of PET nonwoven fabric containing low-temperature viscoelastic filaments in this application are applicable to components such as wheel cover linings, luggage compartments, chassis, and front storage boxes compared with traditional methods, and can be fully recycled at the end of the product life cycle; 5. Environmental protection: The entire production process is green and environmentally friendly, with no waste generated. All materials are 100% recyclable. Pure PET fiber is used, and the product can be recycled and spun back into PET fiber, thus achieving the requirements of green environmental protection. 6. Low cost: Simple manufacturing and low cost. By reusing waste components, the cost can be reduced by about 10% to 20%; by using PET to replace adhesive fibers, the cost can be reduced by 14% to 26%. 7. Excellent performance: This application has excellent cold resistance, temperature resistance and aging resistance. The 100% PET material processed has no low melting point polymers and the melting points are all between 250-260℃. Therefore, the processed parts can maintain good dimensional stability under high temperature and thermal shock conditions and are not easily deformed. At high temperatures of 150-200℃, the shrinkage is less than 1%; the modulus and strength of the product are improved by 30-50%. Attached Figure Description

[0019] Figure 1 The diagram shows the structure of the PET filament bundles that are cooled and stretched by airflow and the PET filament bundles that are cooled only, where (a) is the PET filament bundle that is cooled only and (b) is the PET filament bundle that is cooled and stretched by airflow. Figure 2 The images show the molecular structures of PET in the low-temperature viscoelastic filament of this application and normal PET, with the left image showing the molecular structure of normal PET and the right image showing the molecular structure of PET in the low-temperature viscoelastic filament. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments. It should be understood that the following embodiments are only for explanation and illustration of the present invention, but do not limit the present invention to these specific embodiments, and do not limit the scope of the present invention in any way.

[0021] Example 1: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. This example belongs to the polyester filament spinning process and includes the following steps: Melt preparation: Raw polyester chips are fed into a spinning melting device for melting and extrusion, and then enter the spinning system through a melt filter and a melt distributor.

[0022] Spinning and forming: The melt enters the spinning box, is precisely metered by the metering pump, and is then extruded through the spinneret of the spinning assembly to form nascent fibers.

[0023] Cooling and solidification: After the nascent fibers exit the spinneret, they first pass through an air blowing device for cooling and solidification. The spinneret of the spinning assembly adopts a segmented or side-by-side configuration to distribute the melt to different spinneret orifices, ensuring that it exits as two independent filament bundles. 10%-80% of the filament bundles are cooled and drawn by airflow, while 20%-90% are only cooled. Specifically, 50% of the filament bundles in section A are cooled and drawn by airflow. An airflow cooling and drawing system is used for cooling and airflow drawing of the filament bundles, with a pressure of 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized, causing them to fully orient and crystallize, forming high-strength, high-heat-resistant PET filaments. The filament bundles extruded from the spinneret, after being cooled by airflow, form monofilaments with a linear density of less than 18 dtex. Figure 1 As shown in (a), 50% of the fiber bundles in section B are directly passed through a cooling and solidification device for rapid cooling and solidification, controlling their crystallinity to form low-orientation, low-crystallinity filaments. This is a unique viscoelastic state, rather than a completely melted flow, thus becoming the "low-temperature viscoelastic filaments" mentioned above. Figure 1 As shown in (b).

[0024] Fiber properties: Part A has a fiber fineness of 5.5 dtex, a fiber diameter of 25 μm, a fiber strength of 2.8 cn / dtex, and a fiber elongation of 15-30%.

[0025] Part B has a fiber fineness of 10-15 detex, a fiber diameter of 40 μm, a fiber strength of 1-1.5 cn / dtex, and a fiber elongation of >300%.

[0026] Fiber felt specifications: Part A and part B fibers are evenly mixed and laid in a 50:50 ratio. The mixture is then spread and evenly dispersed by airflow above the condensing screen and deposited on the moving condensing screen or leather screen to form a uniform filament fiber web. This web is then needle-punched into PET fiber felt, which is a PET nonwoven fabric containing low-temperature viscoelastic filaments with a surface density of 1000 gsm.

[0027] Compression molding: PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240℃ for 20-180 seconds. During this heating process, steam at 160-240℃ and a pressure between 5Pa and 20Pa can be introduced at 13 bar. The molding time is 45 seconds. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. This molding material is used to manufacture automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

[0028] The molded automotive parts were subjected to tensile performance testing according to standard ISO 527 and bending performance testing according to ISO 178. The test results are shown in Table 1.

[0029] Water absorption performance test method: Immerse it in water containing 0.01% laundry detergent for 24 hours at a depth of 100mm, then remove it and test its water content.

[0030] The molded parts were subjected to a long-term aging process of 1000 hours at 120°C. Tensile and bending properties were tested according to the test standards of ISO 527 and ISO 178. The test results are shown in Table 2.

[0031] Example 2: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. This example belongs to the polyester filament spinning process and includes the following steps: Melt preparation: Raw polyester chips are fed into a spinning melting device for melting and extrusion, and then enter the spinning system through a melt filter and a melt distributor.

[0032] Spinning and forming: The melt enters the spinning box, is precisely metered by the metering pump, and is then extruded through the spinneret of the spinning assembly to form nascent fibers.

[0033] Cooling and solidification: After the nascent fibers exit the spinneret, they first pass through an air blowing device for cooling and solidification. The spinneret of the spinning assembly adopts a segmented or side-by-side configuration to distribute the melt to different spinneret orifices, ensuring that it exits as two independent filament bundles. 10%-80% of the filament bundles are cooled and drawn by airflow, while 20%-90% are only cooled. Specifically, 50% of the filament bundles in section A are cooled and drawn by airflow. An airflow cooling and drawing system is used for cooling and airflow drawing of the filament bundles, with a pressure of 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized, causing them to fully orient and crystallize, forming high-strength, high-heat-resistant PET filaments. The filament bundles extruded from the spinneret, after being cooled by airflow, form monofilaments with a linear density of less than 18 dtex. Figure 1 As shown in (a), 50% of the fiber bundles in section B are directly passed through a cooling and solidification device for rapid cooling and solidification, controlling their crystallinity to form low-orientation, low-crystallinity filaments. This is a unique viscoelastic state, rather than a completely melted flow, thus becoming the "low-temperature viscoelastic filaments" mentioned above. Figure 1 As shown in (b).

[0034] Fiber properties: Part A has a fiber fineness of 5.5 dtex, a fiber diameter of 25 μm, a fiber strength of 2.8 cn / dtex, and a fiber elongation of 15-30%.

[0035] Part B has a fiber fineness of 10-15 detex, a fiber diameter of 40 μm, a fiber strength of 1-1.5 cn / dtex, and a fiber elongation of >300%.

[0036] Fiber felt specifications: Part A and part B fibers are evenly mixed and laid in a 50:50 ratio. The mixture is then spread and evenly dispersed by airflow above the condensing screen and deposited on the moving condensing screen or leather screen to form a uniform filament fiber web. This web is then needle-punched into PET fiber felt, which is a PET nonwoven fabric containing low-temperature viscoelastic filaments with a surface density of 1200 gsm.

[0037] Compression molding: PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240℃ for 20-180 seconds. During this heating process, steam at 160-240℃ and a pressure between 5Pa and 20Pa can be introduced at 13 bar. The molding time is 45 seconds. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. This molding material is used to manufacture automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

[0038] The molded parts were subjected to tensile property testing according to standard ISO 527 and bending property testing according to ISO 178. The test results are shown in Table 1.

[0039] Water absorption performance test method: Immerse it in water containing 0.01% laundry detergent for 24 hours at a depth of 100mm, then remove it and test its water content.

[0040] The molded parts were subjected to a long-term aging process of 1000 hours at 120°C. Tensile and bending properties were tested according to the test standards of ISO 527 and ISO 178. The test results are shown in Table 2.

[0041] Example 3: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. This example belongs to the polyester filament spinning process and includes the following steps: Melt preparation: Raw polyester chips are fed into a spinning melting device for melting and extrusion, and then enter the spinning system through a melt filter and a melt distributor.

[0042] Spinning and forming: The melt enters the spinning box, is precisely metered by the metering pump, and is then extruded through the spinneret of the spinning assembly to form nascent fibers.

[0043] Cooling and solidification: After the nascent fibers exit the spinneret, they first pass through an air blowing device for cooling and solidification. The spinneret of the spinning assembly adopts a segmented or side-by-side configuration to distribute the melt to different spinneret orifices, ensuring that it exits as two independent filament bundles. 10%-80% of the filament bundles are cooled and drawn by airflow, while 20%-90% are only cooled. Specifically, 60% of the filament bundles in section A are cooled and drawn by airflow. An airflow cooling and drawing system is used for cooling and airflow drawing of the filament bundles, with a pressure of 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized, causing them to fully orient and crystallize, forming high-strength, high-heat-resistant PET filaments. The filament bundles extruded from the spinneret, after being cooled by airflow, form monofilaments with a linear density of less than 18 dtex. Figure 1 As shown in (a), 40% of the fiber bundles in section B are directly passed through a cooling and solidification device for rapid cooling and solidification, controlling their crystallinity to form low-orientation, low-crystallinity filaments. This is a unique viscoelastic state, rather than a completely melted flow, thus becoming the "low-temperature viscoelastic filaments" mentioned above. Figure 1 As shown in (b).

[0044] Fiber properties: Part A has a fiber fineness of 5.5 dtex, a fiber diameter of 25 μm, a fiber strength of 2.8 cn / dtex, and a fiber elongation of 15-30%.

[0045] Part B has a fiber fineness of 10-15 detex, a fiber diameter of 40 μm, a fiber strength of 1-1.5 cn / dtex, and a fiber elongation of >300%.

[0046] Fiber felt specifications: Part A and part B fibers are evenly mixed and laid in a ratio of 60:40. The mixture is then spread and evenly dispersed by airflow above the condensing screen and deposited on the moving condensing screen or leather screen to form a uniform filament fiber web. This web is then needle-punched into PET fiber felt, which is a PET nonwoven fabric containing low-temperature viscoelastic filaments with a surface density of 1000 gsm.

[0047] Compression molding: PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240℃ for 20-180 seconds. During this heating process, steam at 160-240℃ and a pressure between 5Pa and 20Pa can be introduced at 13 bar. The molding time is 45 seconds. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. This molding material is used to manufacture automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

[0048] The molded automotive parts were subjected to tensile performance testing according to standard ISO 527 and bending performance testing according to ISO 178. The test results are shown in Table 1.

[0049] Water absorption performance test method: Immerse it in water containing 0.01% laundry detergent for 24 hours at a depth of 100mm, then remove it and test its water content.

[0050] The molded parts were subjected to a long-term aging process of 1000 hours at 120°C. Tensile and bending properties were tested according to the test standards of ISO 527 and ISO 178. The test results are shown in Table 2.

[0051] Example 4: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. This example belongs to the polyester filament spinning process and includes the following steps: Melt preparation: Raw polyester chips are fed into a spinning melting device for melting and extrusion, and then enter the spinning system through a melt filter and a melt distributor.

[0052] Spinning and forming: The melt enters the spinning box, is precisely metered by the metering pump, and is then extruded through the spinneret of the spinning assembly to form nascent fibers.

[0053] Cooling and solidification: After the nascent fibers exit the spinneret, they first pass through an air blowing device for cooling and solidification. The spinneret of the spinning assembly adopts a segmented or side-by-side configuration to distribute the melt to different spinneret orifices, ensuring that it exits as two independent filament bundles. 10%-80% of the filament bundles are cooled and drawn by airflow, while 20%-90% are only cooled. Specifically, 60% of the filament bundles in section A are cooled and drawn by airflow. An airflow cooling and drawing system is used for cooling and airflow drawing of the filament bundles, with a pressure of 0.5-2.8 kg / cm². 2Compressed air is used to stretch the PET filaments that need to be crystallized, causing them to fully orient and crystallize, forming high-strength, high-heat-resistant PET filaments. The filament bundles extruded from the spinneret, after being cooled by airflow, form monofilaments with a linear density of less than 18 dtex. Figure 1 As shown in (a), 40% of the fiber bundles in section B are directly passed through a cooling and solidification device for rapid cooling and solidification, controlling their crystallinity to form low-orientation, low-crystallinity filaments. This is a unique viscoelastic state, rather than a completely melted flow, thus becoming the "low-temperature viscoelastic filaments" mentioned above. Figure 1 As shown in (b).

[0054] Fiber properties: Part A has a fiber fineness of 5.5 dtex, a fiber diameter of 25 μm, a fiber strength of 2.8 cn / dtex, and a fiber elongation of 15-30%.

[0055] Part B has a fiber fineness of 10-15 detex, a fiber diameter of 40 μm, a fiber strength of 1-1.5 cn / dtex, and a fiber elongation of >300%.

[0056] Fiber felt specifications: Part A and part B fibers are uniformly mixed and laid in a ratio of 60:40. The mixture is then spread and fully mixed and evenly dispersed by airflow above the condensing screen, and deposited on the moving condensing screen or leather screen to form a uniform filament fiber web. This web is then needle-punched into PET fiber felt, which is a PET nonwoven fabric containing low-temperature viscoelastic filaments with a surface density of 1200 gsm.

[0057] Compression molding: PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240℃ for 20-180 seconds. During this heating process, steam at 160-240℃ and a pressure between 5Pa and 20Pa can be introduced at 13 bar. The molding time is 45 seconds. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. This molding material is used to manufacture automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

[0058] The molded automotive parts were subjected to tensile performance testing according to standard ISO 527 and bending performance testing according to ISO 178. The test results are shown in Table 1.

[0059] Water absorption performance test method: Immerse it in water containing 0.01% laundry detergent for 24 hours at a depth of 100mm, then remove it and test its water content.

[0060] The molded parts were subjected to a long-term aging process of 1000 hours at 120°C. Tensile and bending properties were tested according to the test standards of ISO 527 and ISO 178. The test results are shown in Table 2.

[0061] Table 1: Performance Test Data .

[0062] Table 2: Performance data after long-term aging at 120℃ for 1000 hours: .

[0063] Example 5: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. Polyester chips are fed into two screw extruders, screw extruder A and screw extruder B, respectively. Screw extruder A extrudes 10%-80% of the filament bundles through airflow cooling and stretching. Specifically, an airflow cooling and stretching system is used to cool and stretch the filament bundles, with a pressure of 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized, causing them to fully orient and crystallize, forming high-strength, high-heat-resistant PET filaments. Screw extruder B only extrudes 20%-90% of the filament bundles after cooling, controlling their crystallinity. The air-cooled and stretched filament bundles are mixed with the air-cooled filament bundles at the condensing screen. Above the condensing screen, airflow is used to fully mix and evenly disperse the filaments, which then deposit on the moving condensing screen or screen to form a uniform filament fiber web. After web-laying and needle punching reinforcement, the final product has a basis weight of 200-2000 g / m². 2 It is a non-woven fabric.

[0064] Example 6: A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments. The method involves mixing 10-80% polyester filaments and 20-90% low-temperature viscoelastic filaments from yarn packages during unwinding. The low-temperature viscoelastic filaments are low-orientation, low-stretch continuous filaments; these low-orientation, low-stretch continuous filaments are one or more of UDY, MOY, and POY. The polyester filaments are high-orientation, high-crystallinity, high-stretch, and high-strength filaments; these high-orientation, high-crystallinity, high-stretch, and high-strength filaments are one or more of HOY, FOY, FDY, DTY, ATY, and HMLS. The mixture is then placed together at a condensing screen, and further mixed and evenly dispersed by airflow above the condensing screen, depositing onto a moving condensing screen or sheet to form a uniform filament fiber web. After web-laying and needle punching reinforcement, the resulting fabric has a basis weight of 200-2000 g / m². 2 It is a non-woven fabric.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing PET nonwoven fabric containing low-temperature viscoelastic filaments, characterized in that, Use any one of the following three preparation methods: First preparation method: Polyester chips are fed into a spinning device and melted, extruded, filtered, and metered before entering the spinning assembly for spinning. The spinning assembly uses a segmented or side-by-side spinneret to distribute the melt to different spinneret holes, ensuring that the molten material is ejected as two independent filament bundles. 10%-80% of the filament bundles are cooled and stretched by airflow, while 20%-90% of the filament bundles are only cooled. The two filament bundles are mixed together at the condensing screen and then reinforced by web laying and needle punching to become a PET nonwoven fabric containing low-temperature viscoelastic filaments. The second preparation method: Polyester chips are fed into two screw extruders, screw extruder A and screw extruder B, respectively. Screw extruder A extrudes 10%-80% of the filament bundles through air cooling and stretching, while screw extruder B extrudes 20%-90% of the filament bundles through cooling only. The filament bundles extruded by air cooling and stretching and the filament bundles extruded by cooling only are mixed together at the condensing screen, and after being reinforced by web laying and needle punching, they become PET nonwoven fabric containing low-temperature viscoelastic filaments. The third preparation method: 10-80% polyester filament and 20-90% low-temperature viscoelastic filament are mixed in yarn bobbins during unwinding, and then mixed together at the condensing screen. After being reinforced by needle punching, it becomes a PET nonwoven fabric containing low-temperature viscoelastic filament.

2. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, In the first preparation method, 10%-80% of the filament bundles are cooled and drawn by airflow. Specifically, the airflow cooling and drawing system is used to cool and draw the filament bundles by airflow, so that they are fully oriented and crystallized to form high-strength and high-heat-resistant PET filaments. The filament bundles sprayed out by the spinneret have a single filament linear density of less than 18 dtex after being cooled by airflow.

3. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, In the first preparation method, 20%-90% of the filament bundles are only cooled to control their crystallinity.

4. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, In the second preparation method, screw extruder A extrudes 10%-80% of the filament bundle through airflow cooling and stretching. Specifically, the airflow cooling and stretching system is used to cool and stretch the filament bundle to fully orient and crystallize it, forming high-strength and high-heat-resistant PET filaments.

5. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, In the second preparation method, screw extruder B only extrudes 20%-90% of the long filament bundles after cooling, thus controlling its crystallinity.

6. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that: In the third preparation method, the low-temperature viscoelastic filament is a low-orientation, low-stretch continuous filament; the low-orientation, low-stretch continuous filament is one or more of UDY, MOY, and POY.

7. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, In the third preparation method, the polyester filament is a highly oriented, highly crystalline, highly tensile, and highly strong filament; the highly oriented, highly crystalline, highly tensile, and highly strong filament is one or more of HOY, FOY, FDY, DTY, ATY, and HMLS.

8. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, The pressure used in the airflow cooling stretching process is 0.5-2.8 kg / cm². 2 Compressed air is used to stretch the PET filaments that need to be crystallized.

9. The method for preparing a PET nonwoven fabric containing low-temperature viscoelastic filaments according to claim 1, characterized in that, The mixing at the condensing screen specifically involves spreading and uniformly dispersing the fibers above the condensing screen using airflow, and depositing them onto the moving condensing screen or leather screen to form a uniform long filament fiber web. After web laying and needle punching reinforcement, the web achieves a weight of 200-2000 g / m². 2 It is a non-woven fabric.

10. The application of a PET nonwoven fabric containing low-temperature viscoelastic filaments prepared by any one of the preparation methods of claims 1-9 in the preparation of molding materials, characterized in that, The PET nonwoven fabric containing low-temperature viscoelastic filaments is transferred to a heating mold for heating at a temperature of 120-240℃ for 20-180 seconds. During this heating process, steam at 160-240℃ and a pressure between 5Pa and 20Pa can be introduced, or steam can be left unintroduced. The PET nonwoven fabric melts and solidifies to obtain a high-temperature resistant, dimensionally stable PET molding material. This molding material is used to manufacture automotive parts, which are one or more of the following: wheel cover liner, trunk, chassis, and front storage box.

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