High-temperature-resistant dimensionally stable pet material and preparation method and application thereof

Abstract

The application discloses a kind of high-temperature-resistant dimensionally stable PET material and its preparation method and application, belong to PET material technical field, modified polyethylene terephthalate PET fiber is made by melt spinning, mixed fiber is prepared by mixing modified PET fiber and PET fiber, mixed fiber is put into opener and is opened, and secondary mixing is carried out, the mixed fiber after secondary mixing is carded, and form sparse and smooth fiber web, fiber web is sent into needle punch machine and carries out needle punching process, finally obtain hot melt mat blank, hot melt mat blank is transferred to hot mould and heated, PET fiber is melted and solidified into shape, obtain high-temperature-resistant dimensionally stable PET material, product can be recycled and spun into PET fiber again, entire production process is green and environment-friendly, without any waste material generation, all materials can be 100% recycled and utilized, with good thermal stability at 150 DEG C-180 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of PET material technology, specifically relating to a high-temperature resistant, dimensionally stable PET material, its preparation method, and its application. Background Technology

[0002] With rapid economic development and improved living standards, the automotive industry has also grown rapidly. People's demands for car quality extend beyond just the car's functionality and appearance; they also include the aesthetics of the interior. Traditionally, components such as wheel arches, trunks, and chassis are typically made of plastic. However, with the widespread application of flexible textile materials, fiber felt is now widely used in automotive parts. Textile-based automotive components possess noise absorption and shock absorption properties, thereby reducing the impact of noise on the environment and passengers during vehicle operation.

[0003] Currently, the felt materials used in automotive parts are made from PP / PET, PET / BICO, PET / PP / BICO, and other fiber felts produced through needle punching. Because PP fibers are used as a binder, the material is not recyclable, generating a large amount of waste during the molding process. Furthermore, this material has insufficient thermal stability, with a maximum heat resistance temperature between 95-110℃, indicating poor heat resistance. Replacing PP fibers with traditional methods using high-melting-point Bico (180℃) or low-melting-point Bico (110℃) fibers results in even worse thermal stability, with the molded product's heat resistance temperature between 70-90℃, failing to meet the requirements of automotive OEMs and incurring higher costs. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this application provides a high-temperature resistant, dimensionally stable PET material, its preparation method, and its application. This solves the problems of existing technologies that use PP fibers as adhesives, resulting in non-recyclable materials, generating large amounts of waste during molding, and insufficient thermal stability (maximum heat resistance temperature between 95-110℃). Traditional methods using high-melting-point or low-melting-point Bico fibers exhibit even worse thermal stability, with molded products having a heat resistance temperature between 70-90℃, making it difficult to meet the requirements of automotive OEMs and incurring high costs. This invention provides a 100% PET material solution using modified PET fiber materials to replace traditional PP and Bico adhesive fibers.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a high-temperature resistant, dimensionally stable PET material includes the following steps:

[0007] S1: Modified polyethylene terephthalate (PET) fibers are produced by melt spinning;

[0008] S2, Preparation of normally spun polyethylene terephthalate (PET) fibers: PET material with an intrinsic viscosity of 0.6-1.0 dL / g is dried at 180℃ for 5 hours under nitrogen protection until the moisture content is ≤50ppm; a water-repellent agent of ≤5wt% is added, and the material is melted in stages using a screw extruder. The melting temperatures are 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The melt is filtered through a 15-25μm filter and then fed to a spinneret with a spinneret orifice diameter of 0.1-0.35mm. A side-blowing system operates at 20- The melt stream is cooled at 35℃ and an air velocity of 0.4-3m / s to form nascent fibers. These nascent fibers are then subjected to multi-stage stretching: first-stage stretching at 60-90℃ to a stretch of 2-4 times; second-stage stretching at 120-160℃ to a stretch of 3-6 times, yielding PET fibers. These fibers are then relaxed at 180-220℃ for 10-60 seconds, reducing the boiling water shrinkage rate to less than 7%. Finally, the PET fibers are cut into 38-100mm short fibers. The PET fibers have a breaking strength of 1.5-4cN / dtex and a breaking elongation of 15-100%.

[0009] S3, Raw material mixing: Mix 10-100% of modified polyethylene terephthalate (PET) fiber and 0-90% of PET fiber by mass percentage to obtain mixed fiber;

[0010] S4: Place the mixed fibers into a pre-opening machine for opening and then perform a secondary mixing;

[0011] S5, the mixed fibers after secondary mixing are combed: the mixed fibers after secondary mixing are pre-combed to initially decompose the fiber bundles and remove 5-10mm impurities, and then the main combing is carried out to make the fiber single fibrillation exceed 90%, the removal rate of short fibers <12.7mm is greater than 80%, and then a sparse and flat fiber web is formed.

[0012] S6: After the fiber web is cross-laid, it is fed into a needle punching machine for needle punching to finally obtain needle punched fiber felt blank.

[0013] S7: Transfer the needle-punched fiber felt blank to a hot mold and heat it. The mold temperature is 160-240℃ and the heating time is 40s-120s. The needle-punched fiber felt melts and solidifies to form a high-temperature resistant and dimensionally stable PET material molded part.

[0014] Preferably, in step S1, modified polyethylene terephthalate (PET) fibers are produced by melt spinning, and the specific steps are as follows:

[0015] Step 1: Dry PET material with an intrinsic viscosity of 0.6-1.0 dL / g at 170-180℃ for 4-8 hours under nitrogen protection until the moisture content is ≤50ppm; add ≤5wt% water-repellent agent, and melt it in stages through a screw extruder. The melting temperature is 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The temperature of the spinning box is 245-320℃. The melt is filtered through a 15-25μm filter screen and then fed to a spinneret with a spinneret orifice diameter of 0.1-0.35mm to obtain PET fiber filaments.

[0016] The second step is to cool and solidify the filaments: the PET fiber filaments obtained in the first step are blown in a ring or by side air at a temperature of 20-35℃ and a humidity of 70-80%, with a wind speed of 0.4-3m / s to cool the melt stream and obtain nascent fibers.

[0017] The third step is storage: the ambient temperature for storing nascent fibers is 10-25℃, and the storage time is 4-48 hours, controlling the crystallinity increase to ≤1.5% and the internal stress release rate to ≥80%; the relative humidity for storing nascent fibers is 55-75%, maintaining the fiber moisture content at 0.1-0.5% to avoid hydrolysis or deformation; nascent fibers are stored in a light-proof environment, and the storage time and intrinsic viscosity IV of the nascent fibers meet the following conditions: storage time ≤100 hours, and the intrinsic viscosity IV is guaranteed to be 0.03-0.06 Dl / g lower than the intrinsic viscosity of the raw material to obtain nascent filaments;

[0018] Step 4, Bundling: The stored nascent filaments are bundled using mechanical bundling rollers at a linear speed of 80-400 m / min, with an inter-roller pressure of 0.1-1 MPa and a fiber bundle density of 0.25-1.0 g / cm³. 3 The fiber orientation angle deviation within the bundle is ≤20°. After bundling, the fibers are treated with a low-temperature hot roller at 60-100℃ or hot air at a wind speed of 1-5m / s for 5-30 seconds, and the shrinkage rate is controlled at 1-5%.

[0019] Step 5, drawing: After the nascent filaments are mechanically bundled, they enter the drawing process. During the drawing process, the drawing power is reduced so that the drawing ratio is less than 3.

[0020] Step 6, heat setting and crimping: The drawn nascent filaments enter the relaxation heat setting and crimping mechanism. The relaxation heat setting temperature is less than 100℃ and the time is 10-60s to obtain modified PET fibers. The modified PET fibers after setting are crimped, with 3-20 crimps per 25mm. To ensure stable crimping, the crimping process should be carried out at the glass transition temperature of 70-120℃.

[0021] Step 7, Cutting and Packaging: Finally, the modified PET fiber is cut into short fibers of 38-100mm, with a fiber breaking strength of 0.5-4cN / dtex and a breaking elongation of 200-700%, to obtain low-strength and high-elongation modified polyethylene terephthalate PET fiber.

[0022] Preferably, in the first step, excessively high or low spinning temperature will lead to abnormal fibers during forming. The production requirement is that the spinning temperature fluctuation range is ≤±2℃. In the third step, the pre-orientation degree of the initially formed nascent fiber is uneven, and it needs to be stored and balanced to balance stress relaxation and structural stability. The purpose of storage is to reduce or eliminate internal stress, ensure uniform diffusion of oil during winding, and improve the tensile properties of the fiber.

[0023] Preferably, the PET material is one or more of PET chips, recycled PET particles, and PET bottle flakes; after the PET material is dried, a water-repellent agent of ≤5wt% is added to meet the water-repellent requirements of the parts.

[0024] Preferably, in step S3, the modified polyethylene terephthalate (PET) fiber and the PET fiber are mixed by airflow mixing, a packing machine, or a cotton blending curtain.

[0025] Preferably, in step S4, the pre-opening machine initially loosens large pieces of fiber raw material, reducing the burden on subsequent opening equipment and initially removing large particles of impurities. Then, the fiber bundles are further decomposed in the blending box or fine opening equipment to fully remove fine impurities, which are short fibers and dust.

[0026] Preferably, in step S7, after the needle-punched fiber felt blank is transferred to a hot mold and heated, steam at 160-240°C is introduced. First, hot steam at 5Pa-20Pa is introduced for 2-5 seconds to remove the cold air from the mold, and then steam heating is performed for 40-120 seconds.

[0027] This application also discloses a high-temperature resistant, dimensionally stable PET material prepared by any of the above-mentioned methods. The high-temperature resistant, dimensionally stable PET material is composed of two types of fibers: mutually entangled, self-adhesive modified polyethylene terephthalate fibers and normally spun polyethylene terephthalate fibers. The normally spun polyethylene terephthalate fibers have a fineness between 4D and 20D and a length of 38mm to 100mm. The modified polyethylene terephthalate fibers have a fineness between 4D and 250D and a length of 38mm to 100mm. The high-temperature resistant, dimensionally stable PET material is a nonwoven material with a heat resistance temperature of 150-180℃ and a dimensional shrinkage rate of less than 1%.

[0028] Application of a high-temperature resistant, dimensionally stable PET material in nonwoven fabrics.

[0029] Preferably, the nonwoven fabric is an automotive part, such as a car underbody protection plate, a car wheel cover, a trunk, a compressor enclosure, or a car front storage box.

[0030] Explanation of the principle: This invention uses modified polyethylene terephthalate (PET) fiber as the bonding fiber, replacing the traditional PET two-component BICO (core layer with a melting point of 256°C, and sheath layer with a melting point of 110°C or 180°C) and polypropylene (PP) fibers. This is because traditional BICO does not meet the heat resistance requirements, and PP cannot meet the goal of overall material recyclability. The modified PET fiber initially has an amorphous structure. The amorphous modified PET fiber is in a cis conformation. When heated, this modified PET fiber interacts with the PET fiber... The intersecting parts self-adhede, resulting in crystallization and a transformation to the trans conformation, thus allowing it to replace PP and BICO adhesive fiber materials. After being heated to form parts, the modified polyethylene terephthalate fiber does not exhibit thermal crystallization peaks in the heated region, meaning that the amorphous areas have all been transformed into crystalline regions. Therefore, it exhibits higher temperature resistance and better dimensional stability during the high-temperature heating stage after the nonwoven fabric is formed. After being heated at 180℃ for 72 hours, the shrinkage rate of this nonwoven material is less than 1%, and its strength, toughness, and elasticity remain unchanged when stored under environmental conditions.

[0031] Beneficial effects:

[0032] 1. This application discloses a high-temperature resistant, dimensionally stable PET material and its preparation method and application. It uses a modified PET fiber to replace the traditional PP-PET, PP-BICO-PET, BICO-PET and other adhesive fibers as a homogeneous material solution, which significantly improves thermal stability and meets the thermal stability requirements of different customers. The maximum heat resistance temperature is increased from 95℃ to 150-180℃, and the fiber can be produced using 100% recyclable granules.

[0033] 2. The dimensionally stable, high-temperature resistant PET felt disclosed in this application has a basis weight of 300 g / m². 2 –2000g / m 2 It is suitable for automotive wheel covers, trunks, chassis and other components, and can be fully recycled at the end of the product life cycle. It has excellent water repellency. When a sample (10cm*10cm) is placed in a beaker of water and stored at 60℃±2℃ for 24 hours, the weight gain is less than 50% (target value is less than 165%). Subsequently, the sample is dried at 23℃ for 24 hours. After the water evaporates, the residual weight gain is less than 0.5% (target value is less than 15%).

[0034] 3. The high-temperature resistant and dimensionally stable PET material disclosed in this application has good mechanical properties. In terms of tensile and bending properties, it is comparable to traditional materials, but it has a significant advantage in tear strength. Its maximum tear force is more than 50% higher than that of traditional materials.

[0035] 4. This application discloses a high-temperature resistant, dimensionally stable PET material, its preparation method, and its application. Compared with traditional methods, this method significantly improves thermal stability and can use 100% recyclable granules to produce fibers, thereby achieving cost savings and environmental protection goals.

[0036] 5. Environmental protection: Made with pure PET fiber, the product is recyclable and can be spun back into PET fiber. The entire production process is green and environmentally friendly, with no waste generated and all materials are 100% recyclable.

[0037] 6. Low cost: Simple manufacturing and low cost. By reusing waste parts, the cost can be reduced by about 10% to 20%; by using heat-resistant and dimensionally stable PET materials instead of adhesive fibers, the cost can be reduced by 14% to 26%.

[0038] 7. Excellent performance: It has excellent cold resistance, temperature resistance and aging resistance; it has good thermal stability at high temperatures of 150℃-180℃. Attached Figure Description

[0039] Figure 1 The thermal properties curve of polyethylene terephthalate fiber spun normally according to this application is shown.

[0040] Figure 2 This is a graph showing the thermal properties of the modified polyethylene terephthalate fiber described in this application.

[0041] Figure 3 The modified polyethylene terephthalate fiber amorphous PET of this application is in cis conformation.

[0042] Figure 4 The image shows the trans conformation of the amorphous PET modified with polyethylene terephthalate fibers in this application.

[0043] Figure 5 These are schematic diagrams of the molecular structures of normal PET and modified PET. Detailed Implementation

[0044] 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.

[0045] Example 1

[0046] A method for preparing a high-temperature resistant, dimensionally stable PET material includes the following steps:

[0047] Step 1: Dry PET material with an intrinsic viscosity of 0.6-1.0 dL / g at 170-180℃ for 4-8 hours under nitrogen protection until the moisture content is ≤50ppm; add ≤5wt% water-repellent agent, and melt it in stages through a screw extruder. The melting temperature is 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The temperature of the spinning box is 245-320℃. The melt is filtered through a 15-25μm filter screen and then fed to a spinneret with a spinneret orifice diameter of 0.1-0.35mm to obtain PET fiber filaments. In the first step, excessively high or low spinning temperatures will lead to abnormal filaments during forming. The production requirement is that the spinning temperature fluctuation range is ≤±2℃. In the third step, the pre-orientation degree of the initially formed nascent fibers is uneven. They need to be stored and balanced to balance stress relaxation and structural stability. The purpose of storage is to reduce or eliminate internal stress, ensure uniform diffusion of the oil agent during winding, and improve the tensile properties of the fibers.

[0048] The second step is to cool and solidify the filaments: the PET fiber filaments obtained in the first step are blown in a ring or by side air at a temperature of 20-35℃ and a humidity of 70-80%, with a wind speed of 0.4-3m / s to cool the melt stream and obtain nascent fibers.

[0049] The third step is storage: the ambient temperature for storing nascent fibers is 10-25℃, and the storage time is 4-48 hours, controlling the crystallinity increase to ≤1.5% and the internal stress release rate to ≥80%; the relative humidity for storing nascent fibers is 55-75%, maintaining the fiber moisture content at 0.1-0.5% to avoid hydrolysis or deformation; nascent fibers are stored in a light-proof environment, and the storage time and intrinsic viscosity IV of the nascent fibers meet the following conditions: storage time ≤100 hours, and the intrinsic viscosity IV is guaranteed to be 0.03-0.06 Dl / g lower than the intrinsic viscosity of the raw material to obtain nascent filaments;

[0050] Step 4, Bundling: The stored nascent filaments are bundled using mechanical bundling rollers at a linear speed of 80-400 m / min, with an inter-roller pressure of 0.1-1 MPa and a fiber bundle density of 0.25-1.0 g / cm³. 3 The fiber orientation angle deviation within the bundle is ≤20°. After bundling, the fibers are treated with a low-temperature hot roller at 60-100℃ or hot air at a wind speed of 1-5m / s for 5-30 seconds, and the shrinkage rate is controlled at 1-5%.

[0051] Step 5, drawing: After the nascent filaments are mechanically bundled, they enter the drawing process. During the drawing process, the drawing power is reduced so that the drawing ratio is less than 3.

[0052] Step 6, heat setting and crimping: The drawn nascent filaments enter the relaxation heat setting and crimping mechanism. The relaxation heat setting temperature is less than 100℃ and the time is 10-60s to obtain modified PET fibers. The modified PET fibers after setting are crimped, with 3-20 crimps per 25mm. To ensure stable crimping, the crimping process should be carried out at the glass transition temperature of 70-120℃.

[0053] Step 7, Cutting and Packaging: Finally, the modified PET fiber is cut into short fibers of 38-100mm. The fibers have a breaking strength ≥0.5cN / dtex and less than 4cN / dtex, and a breaking elongation >200% and less than 700%, thus obtaining low-strength and high-elongation modified polyethylene terephthalate PET fiber.

[0054] Step 8, Preparation of polyethylene terephthalate (PET) fibers by normal spinning: PET material with an intrinsic viscosity of 0.6-1.0 dL / g is dried at 180℃ for 5 hours under nitrogen protection until the moisture content is ≤50ppm; a water-repellent agent of ≤5wt% is added, and the material is melted in stages using a screw extruder. The melting temperatures are 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The melt is filtered through a 15-25μm filter and then fed to a spinneret with a spinneret orifice diameter of 0.1-0.35mm. The side-blowing system operates at 20-35℃. The melt stream is cooled by an air velocity of 4-3 m / s to form nascent fibers. These nascent fibers are then subjected to multi-stage stretching: first-stage stretching at 60-90℃ for 2-4 times the original length; second-stage stretching at 120-160℃ for 3-6 times the original length, yielding PET fibers. These fibers are then relaxed at 180-220℃ for 10-60 seconds, reducing the boiling water shrinkage rate to less than 7%. Finally, the PET fibers are cut into 38-100 mm short fibers. The PET fiber tensile strength is ≥1.5 cN / dtex and <4 cN / dtex, and the elongation at break is >25% and <100%.

[0055] Step 9, Raw material mixing: Mix 10-100% of modified polyethylene terephthalate (PET) fiber and 0-90% of PET fiber by weight to obtain mixed fiber; the mixing method of modified PET fiber and PET fiber is air mixing, opening machine or cotton blending curtain;

[0056] Step 10: Place the mixed fibers into a pre-opening machine for opening and secondary mixing; the pre-opening machine initially loosens large pieces of fiber raw materials to reduce the burden on subsequent opening equipment and initially removes large particles of impurities. Then, it enters the blending box or fine opening equipment to further decompose the fiber bundles and fully remove fine impurities, which are short fibers and dust.

[0057] Step 11: Card the mixed fibers after secondary mixing: First, pre-card the mixed fibers after secondary mixing to initially break down the fiber bundles and remove 5-10mm impurities. Then, perform main carding to make the fiber single fibrillation exceed 90% and the removal rate of short fibers <12.7mm greater than 80%, thus forming a sparse and flat fiber web.

[0058] Step 12: After the fiber web has undergone the cross-laying process, it is fed into the needle punching machine for needle punching to finally obtain the needle punched fiber felt blank.

[0059] Step 13: Transfer the needle-punched fiber felt blank to a hot mold and heat it. The mold temperature is 160-240℃ and the heating time is 40s-120s. The needle-punched fiber felt melts and solidifies to form a high-temperature resistant and dimensionally stable PET material.

[0060] The raw materials for the PET are one or more of PET chips, recycled PET particles, and PET bottle flakes; after the PET material is dried, a water-repellent agent of ≤5wt% is added to meet the water-repellent requirements of the parts.

[0061] After transferring the needle-punched fiber felt blank into a hot mold and heating it, steam is introduced. First, hot steam of 5 Bar-15 Bar is introduced for 2-5 seconds to remove the cold air from the mold, and then steam heating is carried out for 40-120 seconds.

[0062] The modified polyethylene terephthalate (PET) fiber of this application is produced by adjusting the spinning process. Modified PET fiber can also be obtained through chemical modification methods such as adding additives to alter the molecular structure and adding side chains.

[0063] High-temperature resistant, dimensionally stable PET material is a nonwoven material composed of two types of fibers: entangled, self-adhesive modified polyethylene terephthalate (PET) fibers and normally spun PET fibers. The normally spun PET fibers have a fineness between 4D and 20D and a length of 38mm to 100mm. The thermal performance curve is shown below. Figure 1 As shown, the thermal property curves of the modified polyethylene terephthalate fiber are as follows: Figure 2 As shown in the DSC diagram, there are two crystallization peaks: one occurring during the cooling stage and the other during the first heating stage. Compared to normally spun polyethylene terephthalate (PET) fibers, the modified PET exhibits a crystallization peak during the first heating stage, primarily representing the extended chain crystalline form. PET materials containing this extended chain crystalline form, after compression molding, possess unique comprehensive properties such as better heat resistance, dimensional stability, and higher heat resistance temperatures. During the thermoforming process, nonwoven materials undergo self-adhesion at fiber intersections.

[0064] Modified polyethylene terephthalate (PET) fibers initially possess an amorphous structure. The amorphous modified PET fibers are in a cis conformation, such as... Figure 3 As shown, when heated, the modified polyethylene terephthalate fibers self-adhere at the intersections with each other, resulting in crystallization and a transformation to the trans conformation, as shown in the diagram. Figure 4 As shown, this material can therefore replace adhesive fiber materials such as PP and BICO. No thermal crystallization peak is found in the second thermal heating DSC curve, indicating high temperature resistance and better dimensional stability during the high-temperature heating stage after the nonwoven fabric is formed. After being heated at 180℃ for 72 hours, the shrinkage rate of this nonwoven material is less than 1%, and its strength, toughness, and elasticity remain unchanged when stored under environmental conditions.

[0065] Example 2

[0066] The application of a high-temperature resistant, dimensionally stable PET material prepared in Example 1 in automotive wheel arches is described. This material replaces traditional adhesive fibers. Sample 1 consists of conventional PET and modified PET in a 50%:50% ratio, with a basis weight of 1400 gsm, and was pressed into an automotive wheel arch part. Sample 2 consists of conventional PET and modified PET in a 60%:40% ratio, with a basis weight of 1400 gsm, and was also pressed into an automotive wheel arch part. Tensile, bending, tear, and heat resistance tests were conducted according to standard testing methods. The experimental results are as follows:

[0067] According to the ISO 527-3 test standard, the results of tensile strength and tensile modulus are as follows:

[0068]

[0069]

[0070] According to the ISO 178 test standard, the results for flexural strength and flexural modulus are as follows:

[0071]

[0072]

[0073] According to the tear test standards of the car manufacturers, the tear force results are as follows:

[0074]

[0075]

[0076] The comprehensive mechanical properties show that the material of the present invention has good performance in both tension and bending, especially in terms of tearing. The tearing force of traditional materials can only reach about 60N, while the material of the present invention has a very obvious advantage.

[0077] According to the requirements of a certain OEM, the water repellency performance of the sample was tested. The sample (10cm*10cm) was placed in a beaker containing water and stored at 60℃±2℃ for 24 hours. The weight gain was measured to be less than 50% (target value is less than 165%). Subsequently, the sample was dried at 23℃ for 24 hours. After the water evaporated, the residual weight gain was less than 0.5% (target value is less than 15%). Compared with traditional materials, which are difficult to meet the water repellency requirements, the water repellency performance of the material of this invention is greatly improved, and it fully meets the customer's requirements.

[0078]

[0079] Shrinkage and heat resistance were tested at different temperatures. The experimental results are as follows:

[0080] 105℃ / 72 hours: Shrinkage rate of the sample after heating at 105℃ for 72 hours, shrinkage rate: 0% to -0.5%;

[0081] 150℃ / 72 hours: The shrinkage rate of the sample after heating at 150℃ for 72 hours, shrinkage rate: 0% to -1%.

[0082] Example 3

[0083] The application of a high-temperature resistant, dimensionally stable PET material prepared in Example 1 in a luggage storage box. This method uses a high-temperature resistant, dimensionally stable PET material to replace traditional adhesive fibers. The ratio of conventional PET to modified PET is 50%:50%, and the basis weight is 1400 gsm. The shrinkage rate at different temperatures and times was tested. The experimental results are as follows:

[0084] 105℃ / 2 hours: The shrinkage rate of the sample after heating at 105℃ for 2 hours, shrinkage rate: 0% to -0.25%;

[0085] 150℃ / 2 hours: The shrinkage rate of the sample after heating at 150℃ for 2 hours, shrinkage rate: 0% to -0.25%.

[0086] Example 4

[0087] The application of a high-temperature resistant, dimensionally stable PET material prepared in Example 1 in compressor encapsulation. This method uses a high-temperature resistant, dimensionally stable PET material to replace traditional adhesive fibers. The ratio of conventional PET to modified PET is 50%:50%, with a basis weight of 1400 gsm. The flexural properties under different pressures and times were tested. The experimental results are as follows:

[0088] Pressure 6 Bar, pre-steaming for 5 s + pressure holding for 30 s: The sample performed well: maximum bending load (N): average 7.964, bending strength (MPa): 2.8;

[0089] Pressure 10 Bar, pre-steaming for 5 s + pressure holding for 30 s: The sample performed well: maximum bending load (N): average 6.664, bending strength (MPa): 2.3;

[0090] Pressure 15 Bar, pre-steaming for 5 seconds + pressure holding for 30 seconds: The sample performed well. Maximum load (N): average 9.817; flexural strength (MPa): 3.6.

[0091] The experimental data above demonstrates that using high-temperature resistant, dimensionally stable PET material to replace traditional adhesive fibers exhibits significant advantages in tear resistance, water repellency, and temperature resistance. It also offers notable advantages in cost reduction and environmental friendliness.

[0092] 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 a high-temperature resistant, dimensionally stable PET material, characterized in that, Includes the following steps: S1 is produced by melt spinning of modified polyethylene terephthalate (PET) fibers, the specific steps of which are as follows: Step 1: Dry PET material with an intrinsic viscosity of 0.6-1.0 dL / g at 170-180℃ for 4-8 hours under nitrogen protection until the moisture content is ≤50 ppm; add ≤5 wt% water-repellent agent, and melt it in stages through a screw extruder. The melting temperature is 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The temperature of the spinning box is 245-320℃. After filtering through a 15-25μm filter screen, the melt is conveyed to the spinneret with a spinneret orifice diameter of 0.1-0.35mm to obtain PET fiber filaments. The second step is to cool and solidify the filaments: the PET fiber filaments obtained in the first step are blown in a ring or by side air at a temperature of 20-35℃ and a humidity of 70-80%, with a wind speed of 0.4-3 m / s to cool the fine stream of melt and obtain nascent fibers. The third step is storage: the ambient temperature for storing nascent fibers is 10-25℃, and the storage time is 4-48 hours, controlling the crystallinity increase to ≤1.5% and the internal stress release rate to ≥80%; the relative humidity for storing nascent fibers is 55-75%, maintaining the fiber moisture content at 0.1-0.5% to avoid hydrolysis or deformation; nascent fibers are stored in a light-proof environment, and the storage time and intrinsic viscosity IV of the nascent fibers meet the following conditions: storage time ≤100 hours, and the intrinsic viscosity IV is guaranteed to be 0.03-0.06 Dl / g lower than the intrinsic viscosity of the raw material to obtain nascent filaments; Step 4, Bundling: The stored nascent filaments are bundled using mechanical bundling rollers at a linear speed of 80-400 m / min, with an inter-roller pressure of 0.1-1 MPa and a fiber bundle density of 0.25-1.0 g / cm³. 3 The fiber orientation angle deviation within the bundle is ≤20°. After bundling, the fibers are treated with a low-temperature hot roller at 60-100℃ or hot air at a wind speed of 1-5 m / s for 5-30 seconds, and the shrinkage rate is controlled at 1-5%. Step 5, drawing: After the nascent filaments are mechanically bundled, they enter the drawing process. During the drawing process, the drawing power is reduced so that the drawing ratio is less than 3. Step 6, heat setting and crimping: The drawn nascent filaments enter the relaxation heat setting and crimping mechanism. The relaxation heat setting temperature is less than 100℃ and the time is 10-60s to obtain modified PET fibers. The modified PET fibers after setting are crimped, with 3-20 crimps per 25mm. To ensure stable crimping, the crimping process should be carried out at the glass transition temperature of 70-120℃. Step 7, Cutting and Packaging: Finally, the modified PET fiber is cut into short fibers of 38-100mm, with a fiber breaking strength of 0.5-4cN / dtex and a breaking elongation of 200-700%, to obtain low-strength and high-elongation modified polyethylene terephthalate PET fiber. S2, Preparation of polyethylene terephthalate (PET) fibers from normal spinning: PET material with an intrinsic viscosity of 0.6-1.0 dL / g is dried at 180℃ for 5 hours under nitrogen protection until the moisture content is ≤50 ppm; a water-repellent agent of ≤5 wt% is added, and the material is melted in stages using a screw extruder. The melting temperatures are 260-280℃ in the feeding zone, 275-295℃ in the compression zone, and 275-310℃ in the metering zone. The melt is filtered through a 15-25μm filter and then fed to a spinneret with a spinneret orifice diameter of 0.1-0.35mm. A side-blowing system cools the melt stream at 20-35℃ and a wind speed of 0.4-3 m / s to form nascent fibers. The nascent fibers are then subjected to multi-stage stretching: primary stretching (2-4 times stretch at 60-90℃), secondary stretching (3-6 times stretch at 120-160℃) to obtain PET fibers. After relaxation treatment at 180-220℃ for 10-60 seconds, the boiling water shrinkage rate of PET fibers decreased to less than 7%; finally, the PET fibers were cut into short fibers of 38-100mm, with a tensile strength of 1.5-4 cN / dtex and a breaking elongation of 15-100%. S3, Raw material mixing: Mix 10-100% of modified polyethylene terephthalate (PET) fiber and 0-90% of PET fiber by mass percentage to obtain mixed fiber; S4: Place the mixed fibers into a pre-opening machine for opening and then perform a secondary mixing; S5, the mixed fibers after secondary mixing are combed: First, the mixed fibers after secondary mixing are pre-combed to initially decompose the fiber bundles and remove 5-10mm impurities. Then, the main combing is carried out to make the fiber single fibrillation exceed 90%, the removal rate of short fibers <12.7mm is greater than 80%, and then a sparse and flat fiber web is formed. S6: After the fiber web is cross-laid, it is fed into a needle punching machine for needle punching to finally obtain needle punched fiber felt blank. S7: Transfer the needle-punched fiber felt blank to a hot mold and heat it. The mold temperature is 160-240℃ and the heating time is 40s-120s. The needle-punched fiber felt melts and solidifies to form a high-temperature resistant and dimensionally stable PET material molded part.

2. The method for preparing a high-temperature resistant, dimensionally stable PET material according to claim 1, characterized in that, In the first step, excessively high or low spinning temperatures can lead to abnormal fibers during forming. Production requires a spinning temperature fluctuation range of ≤±2℃. In the third step, the pre-orientation of the initially formed nascent fibers is uneven, requiring storage for balancing to relax stress and improve structural stability. The purpose of storage is to reduce or eliminate internal stress, ensure uniform diffusion of the oil agent during winding, and improve the tensile properties of the fibers.

3. The method for preparing a high-temperature resistant, dimensionally stable PET material according to claim 1, characterized in that, The PET material is one or more of PET chips, recycled PET particles, and PET bottle flakes; after the PET material is dried, a water-repellent agent of ≤5 wt% is added to meet the water-repellent requirements of the parts.

4. The method for preparing a high-temperature resistant, dimensionally stable PET material according to claim 1, characterized in that, The modified polyethylene terephthalate (PET) fiber and the PET fiber in S3 are mixed by airflow mixing, a packing machine, or a cotton blending curtain.

5. The method for preparing a high-temperature resistant, dimensionally stable PET material according to claim 1, characterized in that, When the pre-opening machine in S4 opens the fiber raw material, it initially loosens the large pieces of fiber raw material, reduces the burden on subsequent opening equipment, and initially removes large particle impurities. Then it enters the blending box or fine opening equipment to further decompose the fiber bundles and fully remove fine impurities, which are short fibers and dust.

6. The method for preparing a high-temperature resistant, dimensionally stable PET material according to claim 1, characterized in that, In step S7, after transferring the needle-punched fiber felt blank into a hot mold and heating it, steam at 160-240°C is introduced. First, hot steam at 5Pa-20Pa is introduced for 2-5 seconds to remove the cold air from the mold, and then steam heating is carried out for 40-120 seconds.

7. A high-temperature resistant, dimensionally stable PET material prepared by any one of the preparation methods described in claims 1-6, characterized in that, The high-temperature resistant, dimensionally stable PET material is composed of two types of fibers: entangled, self-adhesive modified polyethylene terephthalate (PET) fibers and normally spun PET fibers. The normally spun PET fibers have a fineness between 4D and 20D and a length of 38mm to 100mm, while the modified PET fibers have a fineness between 4D and 250D and a length of 38mm to 100mm. The high-temperature resistant, dimensionally stable PET material is a non-woven material with a heat resistance temperature of 150-180℃ and a dimensional shrinkage rate of less than 1%.

8. The application of a high-temperature resistant, dimensionally stable PET material prepared by any one of the preparation methods of claims 1-6 in nonwoven fabrics.

9. The application according to claim 8, characterized in that, The nonwoven fabric is an automotive part, such as a car underbody protection plate, wheel cover liner, trunk, or compressor enclosure.

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