A pet fiber composite substrate for automobile roof and a method for manufacturing the same

Abstract

This invention relates to the field of automotive headliner substrate technology, specifically to a PET fiber composite substrate for automotive headliners and its preparation method. PU fiberglass sheets used in automotive headliners suffer from poor elongation, heavy weight, and are almost impossible to recycle after disposal. To address these problems, this invention provides a lightweight, recyclable PET fiber composite substrate for automotive headliners that exhibits good elongation and a high thermoforming yield. It is obtained by sequentially bonding hollow coarse denier fibers, ultrafine denier fibers, and low-melting-point fibers through a needle-punching process and hot-pressing. This PET fiber composite substrate is lightweight, recyclable, has good elongation, a high thermoforming yield, and uses widely available raw materials, reducing raw material costs by 10% to 15%. It possesses good market competitiveness in a wide range of applications, covering economy to mid-to-high-end vehicle models.

Description

Technical Field

[0001] This invention relates to the field of automotive headliner substrate technology, specifically to a PET fiber composite substrate for automotive headliners and its preparation method. Background Technology

[0002] As a key component of the interior system, the car headliner not only needs to meet basic functions such as aesthetics, comfort, and sound insulation, but also must consider lightweight and environmental protection requirements. Currently, the mainstream car headliner substrate on the market is mainly polyurethane and fiberglass composite board, namely PU fiberglass board. This type of material has certain rigidity and molding properties, but it has also revealed many shortcomings in practical applications.

[0003] First, PU fiberglass sheets have a higher density, weighing approximately 15% to 30% more than PET substrates of the same thickness. This weight disadvantage becomes increasingly apparent in the context of new energy vehicles pursuing lightweight design to improve driving range. Second, polyurethane is a thermosetting material, and glass fiber is difficult to decompose. The composite material cannot be melted and regenerated, making it almost impossible to recycle the headliner substrate after disposal, which does not meet the increasingly stringent environmental and circular economy requirements of the automotive industry. Third, PU fiberglass sheets have generally poor heat resistance. In summer, the headliner temperature inside a car exposed to direct sunlight can rise above 80°C, at which point the material is prone to slight softening. Long-term use can also lead to aging and warping, affecting its lifespan and interior feel. Furthermore, unreacted monomers or additives often remain in the polyurethane system, resulting in higher odor and volatile organic compound (VOC) content, negatively impacting in-car air quality. Its environmental friendliness and comfort are inferior to PET materials. Finally, the relatively high production and raw material costs of PU fiberglass sheets further limit its overall competitiveness in economy and mid-to-high-end models.

[0004] In contrast, PET fiber has advantages such as recyclability, low odor, low VOC, and good thermoplasticity, gradually becoming an ideal choice for environmentally friendly materials in automotive interiors. However, existing single-form or simply mixed PET fiber substrates often fail to simultaneously meet the requirements of high rigidity, low weight, and good sound absorption performance when used in headliners. For example, using only coarse denier fibers can increase the hardness of the sheet, but the surface is rough and the sound absorption effect is poor; using only fine denier fibers can improve softness and sound insulation, but the structural strength is insufficient and it is prone to deformation. At the same time, PET fibers with different melting points need to be precisely matched during the hot pressing and shaping process, otherwise over-melting or insufficient bonding can easily occur, leading to delamination, uneven thickness, or poor dimensional stability.

[0005] Therefore, there is an urgent need to develop a composite substrate based on a combination of multiple PET fibers, which can ensure lightweight and recyclability while taking into account rigidity, sound absorption performance and molding process stability, so as to replace the existing PU fiberglass board and meet the application needs of automotive roofs. Summary of the Invention

[0006] The existing technology has the following problems: PU fiberglass boards used in automotive headliners have poor elongation, are heavy, and are almost impossible to recycle after being scrapped. To address these problems, this invention provides a lightweight, recyclable PET fiber composite substrate for automotive headliners that has good elongation and a high thermoforming pass rate. It is obtained by sequentially bonding hollow coarse denier fibers, ultrafine denier fibers, and low-melting-point fibers through a needle-punching process and hot-pressing. The hollow coarse denier fibers and ultrafine denier fibers are both PET fibers, and the low-melting-point fiber is a 4080 low-melting-point fiber. The fineness of the hollow coarse denier fiber is 10D-15D, the hollowness is 30%-43%, and the melting point range is 220±10℃; The fineness of the ultrafine denier fiber is 2.5D-3.0D, and the melting point range is 255±5℃; The fineness of the low-melting-point fiber is 4D-5D, and the melting point range of the low-melting-point fiber is 110-140℃. The PET fiber composite substrate, by weight percentage, is composed of the following raw materials: Hollow coarse denier fiber 50-70%; 15-20% ultrafine denier fiber; Low melting point fiber allowance.

[0007] Preferably, the fineness of the hollow coarse denier fiber is 14D.

[0008] Preferably, the fineness of the ultrafine denier fiber is 2.5D.

[0009] Preferably, the fineness of the low-melting-point fiber is 4D.

[0010] Preferably, the PET fiber composite substrate is composed of the following raw materials by weight percentage: Hollow coarse denier fiber 65%; 20% ultrafine denier fiber; Low melting point fiber allowance.

[0011] Preferably, the hot pressing and shaping temperature is 180-210℃.

[0012] Preferably, the preparation method of the PET fiber composite substrate for automotive roofs includes the following steps: (1) Feeding: Weigh according to the formula and feed all fibers into the large warehouse cotton blender for initial and uniform mixing; (2) Fiber opening: The high-speed nail plate tears the fiber block into a single filament state, eliminates clumps, and ensures uniform combing. The first coarse opening is usually 300-600 rpm, and the fine opening is 600-1000 rpm. (3) Vibration mixing: The fan conveys the fibers, so that the three types of fibers are completely and evenly distributed, which improves the strength and reduces the shrinkage rate; (4) Carding: Through the high-speed operation of the cylinder, doffer, and cover plate, the fibers are individually carded and laid out in parallel to form a uniform thin fiber web; (5) Cross-laying: Fold the thin fiber web horizontally and cross it to form a fluffy fiber web; (6) Pre-needle punching: High-speed puncturing of the loose fiber web to obtain a compact fabric with a needle punching density of 30-80 needles / cm 2 The puncture depth is 6-9 mm, and the puncture frequency is 300-500 rpm; (7) Main needle punching: The compacted fabric is needle punched to increase the puncture density and frequency, resulting in a three-dimensional entangled needle-punched composite fiber fabric with a needle punching density of 200-400 needles / cm. 2 The puncture depth is 6-9mm, and the puncture frequency is 700-1200 rpm; (8) Hot pressing and shaping: The needle-punched composite fiber cloth is hot-pressed and bonded using a double-roller hot press. The hot pressing temperature is 180~210℃ and the hot pressing time is 12-15s. The low melting point fiber skin is melted and bonded to obtain a rigid board. (9) Post-processing: The rigid sheet material is naturally cooled to room temperature, and after being cut and tested for broken needles, it is rolled / cut into finished base material as required.

[0013] Compared with existing PU fiberglass boards, the present invention has the following advantages: (1) This invention uses hollow coarse denier PET fibers with a fineness of not less than 10D and a hollowness ratio between 30% and 43% as a three-dimensional skeleton. The hollow structure inside effectively reduces the apparent density of the material itself. After this porous skeleton is combined with ultrafine denier PET fibers and 4080 low melting point fibers, the weight of the substrate can be reduced by 15% to 30% compared with traditional PU fiberglass boards at the same thickness, which directly contributes to improving the driving range of new energy vehicles.

[0014] (2) The main component of the substrate of the present invention is PET fiber, and the 4080 low melting point fiber used is a core-sheath structure. The core layer is also made of PET material, which makes the substrate as a whole thermoplastic material with melt recycling capability. After the car is scrapped, the product can be remade into other PET products through melt granulation process, realizing closed-loop recycling from the headliner substrate to the new product, effectively reducing the environmental burden caused by the scrapping of car interior parts.

[0015] (3) The present invention comprises a high-rigidity three-dimensional network composed of hollow coarse denier PET fibers, which is then densified by filling with ultra-fine denier PET fibers, and then reinforced by physical entanglement formed by needle punching and chemical bonding generated by thermal fusion of 4080 low melting point fiber skin. This increases the heat resistance temperature of the substrate to above 120°C, exhibiting creep resistance without softening, sagging, or warping in high-temperature environments, with dimensional shrinkage rate controlled within 0.5%, and tensile strength increased by 40% compared to the prior art.

[0016] (4) The ultra-fine denier PET fibers with a fineness of only 2.5D to 3.0D in this invention can fully fill the gaps between the coarse denier skeletons, significantly increasing the frictional loss path of sound waves inside the material, thereby improving sound insulation and sound absorption performance. At the same time, the presence of a large number of fine fibers makes the surface of the board smoother and avoids the problems of see-through and fuzzing caused by coarse fibers, thus meeting the comprehensive requirements of car roof in terms of appearance and interior quietness and comfort.

[0017] (5) This invention completely eliminates polyurethane and various solvent-based adhesives used in traditional processes. It utilizes the sheath of 4080 low-melting-point fiber to achieve fiber-to-fiber bonding under hot-press conditions through directional melting. No additional volatile organic compounds are generated during the production process or in the finished product. The finished product has a low odor level, VOC content can be reduced by 60%, and it does not contain formaldehyde or heavy metals, meeting the stringent requirements of the EU RoHS directive and the domestic GB / T 27630 passenger car interior air quality standard.

[0018] (6) This invention precisely matches the thermodynamic properties of each component, setting the melting point of the 4080 low-melting-point fiber sheath in the range of 110 to 140°C, while the conventional PET fiber, which serves as the skeleton, remains at a higher melting point. This ensures that within the hot-pressing temperature range of 180 to 210°C, only the bonding component sheath melts, while the skeleton and core fiber morphology remain intact. This design effectively avoids defects such as yellowing and brittleness of the board caused by excessive melting, or delamination and uneven thickness caused by insufficient bonding. It has good process adaptability, and the thermoforming qualification rate is significantly higher than that of traditional PU fiberglass boards.

[0019] (7) The process route of the present invention eliminates the traditional PU foaming and lengthy curing and maintenance process, and the overall production efficiency can be increased by 30%. The substrate is a thermoplastic composite material, and the scraps and trimming waste in the molding process can be directly recycled and reused. Moreover, the finished board can be directly molded into complex curved surfaces by secondary heating in the subsequent ceiling manufacturing, which greatly facilitates the diversified design of the ceiling.

[0020] (8) The raw materials of the substrate obtained by the present invention are widely available and relatively stable in price, eliminating the need for expensive polyurethane raw materials and glass fiber, thus reducing raw material costs by 10% to 15%. At the same time, the energy consumption of the production process is reduced by about 20%, and the environmental compliance cost advantage brought by the recyclable characteristics of the materials makes the composite substrate of the present invention have significant market competitiveness in a wide range of applications covering economy to mid-to-high-end models. Detailed Implementation

[0021] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0022] The raw materials used in the following embodiments of the present invention are all commercially available products. The hollow coarse denier fiber has a fineness of 14D and was purchased from Changshu Lida Chemical Fiber Raw Material Co., Ltd., model YZK602. The ultrafine denier fiber has a fineness of 2.5D and was purchased from Jiaxing Fuda Chemical Fiber Factory Co., Ltd., model FD2.5D. The low-melting-point fiber has a fineness of 4D, specifically 4080 low-melting-point fiber, and was purchased from Yangzhou Fuwei Composite Materials Co., Ltd., model BL102-01.

[0023] The solid PET fibers with a fineness of 10D used in the comparative examples of this invention were purchased from Changshu Lida Chemical Fiber Raw Materials Co., Ltd., and the model number was YZK310. The solid PET fibers with a fineness of 14D were also purchased from Changshu Lida Chemical Fiber Raw Materials Co., Ltd., and the model number was YZK600. The ultrafine denier fibers with a fineness of 1.5D were purchased from Jiaxing Fuda Chemical Fiber Factory Co., Ltd., and the model number was FD1.5D.

[0024] Example 1 A PET fiber composite substrate for automotive roofs is obtained by sequentially combining hollow coarse denier fibers, ultrafine denier fibers, and low melting point fibers through a needle punching process and hot pressing. Both the hollow coarse denier fibers and the ultrafine denier fibers are PET fibers. The fineness of the hollow coarse denier fiber is 14D; The fineness of the ultrafine denier fiber is 2.5D; The low-melting-point fiber is 4080 low-melting-point fiber with a fineness of 4D. The PET fiber composite substrate, by weight percentage, is composed of the following raw materials: Hollow coarse denier fiber 65%; 20% ultrafine denier fiber; Low melting point fiber allowance.

[0025] The preparation method of PET fiber composite substrate is as follows: (1) Feeding: Weigh according to the formula and feed all fibers into the large warehouse cotton blender for initial and uniform mixing; (2) Fiber opening: The high-speed nail plate tears the fiber block into a single filament state, eliminates clumps, and ensures uniform combing. The first coarse opening is usually 600 rpm, and the fine opening is 1000 rpm. (3) Vibration mixing: The fan conveys the fibers, so that the three types of fibers are completely and evenly distributed, which improves the strength and reduces the shrinkage rate; (4) Carding: Through the high-speed operation of the cylinder, doffer, and cover plate, the fibers are individually carded and laid out in parallel to form a uniform thin fiber web; (5) Cross-laying: Fold the thin fiber web horizontally and cross it to form a fluffy fiber web; (6) Pre-needle punching: High-speed puncturing is performed on the loose fiber web to obtain a compact fabric with a needle punching density of 50 needles / cm. 2 The puncture depth was 7 mm, and the puncture frequency was 450 rpm. (7) Main needle punching: The compacted fabric is needle punched to increase the puncture density and frequency, resulting in a three-dimensional entangled needle-punched composite fiber fabric with a needle punch density of 200 needles / cm. 2 The puncture depth was 6mm and the puncture frequency was 750rpm; (8) Hot pressing and shaping: The needle-punched composite fiber cloth is hot-pressed and bonded using a double-roller hot press. The hot pressing temperature is 180℃ and the hot pressing time is 15s. The low melting point fiber skin is melted and bonded to obtain a rigid board. (9) Post-processing: The rigid sheet material is naturally cooled to room temperature, and after being cut and tested for broken needles, it is cut into pieces as needed to obtain the finished substrate.

[0026] Example 2 is the same as Example 1, except that the proportions of the three fibers are different. The PET fiber composite substrate in Example 2, by weight percentage, consists of the following raw materials: Hollow coarse denier fiber 50%; 35% ultrafine denier fiber; Low melting point fiber allowance.

[0027] Example 3 is the same as Example 1, except that the proportions of the three fibers are different. The PET fiber composite substrate in Example 3, by weight percentage, consists of the following raw materials: Hollow coarse denier fiber 70%; 15% ultrafine denier fiber; Low melting point fiber allowance.

[0028] Comparative Example 1 is the same as Example 1, except that the type of coarse denier fiber is different. In Comparative Example 1, solid PET fibers with a fineness of 10D are used instead of hollow coarse denier fibers with a fineness of 14D in Example 1.

[0029] Comparative Example 2 is the same as Example 1, except that the type of coarse denier fiber is different. In Comparative Example 2, solid PET fibers with a fineness of 14D are used instead of the hollow coarse denier fibers with a fineness of 14D in Example 1.

[0030] Comparative Example 3 is the same as Example 1, except that Comparative Example 3 uses conventional polyester staple fiber with a fineness of 4D to replace the low melting point fiber in Example 1.

[0031] Comparative Example 4 is the same as Example 1, except that the hot pressing temperature in Comparative Example 4 is 170°C.

[0032] Comparative Example 5 is a standard commercially available PU fiberglass board for automotive headliners with a thickness of 3mm, purchased from Jiangsu Changhai Composite Materials Co., Ltd., model EMC100.

[0033] Comparative Example 6 is the same as Example 1, except that Comparative Example 6 uses ultrafine denier fibers with a fineness of 1.5D instead of ultrafine denier fibers with a fineness of 2.5D in Example 1.

[0034] Performance testing The fiber substrates for automotive headliners obtained in the above embodiments and comparative examples of the present invention were subjected to relevant performance tests, and the test results are shown in Table 1.

[0035] The testing method is as follows: Tensile strength: The test standard is GB / T 24218.3-2010.

[0036] Compression rebound rate: The test standard is GB / T 24218.4-2022.

[0037] Thermal conductivity: The test standard is GB / T 10295-2008.

[0038] Average sound absorption coefficient: The test standard is GB / T 20247-2006.

[0039] Elongation: The test standard is GB / T 24218.3-2010.

[0040] Table 1 .

[0041] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, 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 PET fiber composite substrate for automotive headliners, characterized in that, It is obtained by sequentially needle punching and hot pressing composite of hollow coarse denier fiber, ultrafine denier fiber and low melting point fiber. The hollow coarse denier fiber and ultrafine denier fiber are both PET fiber, and the low melting point fiber is 4080 low melting point fiber. The fineness of the hollow coarse denier fiber is 10D-15D, the hollowness is 30%-43%, and the melting point range is 220±10℃; The fineness of the ultrafine denier fiber is 2.5D-3.0D, and the melting point range is 255±5℃; The fineness of the low-melting-point fiber is 4D-5D, and the melting point range of the low-melting-point fiber is 110-140℃. The PET fiber composite substrate, by weight percentage, is composed of the following raw materials: Hollow coarse denier fiber 50-70%; 15-20% ultrafine denier fiber; Low melting point fiber allowance.

2. The PET fiber composite substrate for automotive headliners according to claim 1, characterized in that, The fineness of the hollow coarse denier fiber is 14D.

3. The PET fiber composite substrate for automotive headliners according to claim 1, characterized in that, The fineness of the ultrafine denier fiber is 2.5D.

4. The PET fiber composite substrate for automotive headliners according to claim 1, characterized in that, The fineness of the low-melting-point fiber is 4D.

5. A PET fiber composite substrate for automotive headliners according to claim 1, characterized in that, PET fiber composite substrate, by weight percentage, is composed of the following raw materials: Hollow coarse denier fiber 65%; 20% ultrafine denier fiber; Low melting point fiber allowance.

6. A PET fiber composite substrate for automotive headliners according to claim 1, characterized in that, The hot pressing and shaping temperature is 180-210℃.

7. A PET fiber composite substrate for automotive headliners according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Feeding: Weigh according to the formula and feed all fibers into the large warehouse cotton blender for initial and uniform mixing; (2) Fiber opening: The high-speed nail plate tears the fiber block into a monofilament state. The first coarse opening is usually 300-600 rpm, and the fine opening is 600-1000 rpm. The distance between the feeding roller and the opening roller is 5-10 mm. (3) Vibration mixing: The fan conveys the fibers so that the three types of fibers are completely and evenly distributed; (4) Carding: Through the high-speed operation of the cylinder, doffer, and cover plate, the fibers are individually carded and laid out in parallel to form a uniform thin fiber web; (5) Cross-laying: Fold the thin fiber web horizontally and cross it to form a fluffy fiber web; (6) Pre-needle punching: High-speed puncturing of the loose fiber web to obtain a compact fabric; (7) Main needle punching: The tight fabric is needle punched to increase the puncture density and frequency, and a needle-punched composite fiber fabric is obtained; (8) Hot pressing and shaping: The needle-punched composite fiber cloth is hot-pressed to obtain a rigid board; (9) Post-processing: The rigid sheet material is naturally cooled to room temperature, and after being cut and tested for broken needles, it is rolled / cut into finished products as required.