Polyester low stretch yarn with superfine denier specification and preparation method thereof

Abstract

The invention relates to a high-performance superfine denier polyester low stretch yarn and a preparation method thereof, and solves the problems of poor fineness uniformity, easy loss of functional components and the like in the production process of the polyester low stretch yarn. Through a staged non-twisting and twisting combined tensile deformation process and application of a core layer-coating layer composite spinning structure and core-shell structure additive powder, precise regulation and control of fiber fineness, stable existence of functional components and long-acting maintenance of anti-ultraviolet and antibacterial properties are realized. The preparation method comprises the steps of polyester particle manufacturing, staged tensile deformation and the like. In the spinning process, a core layer is formed by melting and extruding polyester particles, and a coating layer is applied through a solution spraying technology, so that uniform distribution and durability of functional components are ensured. The application of the core-shell structure assistant powder protects the stability of functional components, and the core-shell structure assistant powder has excellent softness, air permeability, drapability and elastic recovery rate as well as good antibacterial and anti-ultraviolet properties, and is suitable for the fields of high-end clothing, sportswear, medical textiles and the like.

Description

Technical Field

[0001] The present application relates to the technical field of fiber preparation, and in particular to an ultra-fine denier polyester low-stretch yarn and a preparation method thereof. Background Art

[0002] In recent years, with the continuous advancement of textile technology and the diversification of consumer demand, ultra-fine denier polyester low-elastic yarn, as a high-performance fiber material, has shown application potential in high-end clothing, sportswear, medical textiles and other fields. Its excellent softness, high elasticity and lightweight properties not only meet the dual pursuit of comfort and fashion in modern clothing, but also promote the rapid development of related industries.

[0003] In terms of related technological advances, certain progress has been made in the optimization of preparation processes, innovation of equipment, and development of functionalization. The combination of false twist texturing (DTY) and high-speed spinning technology has enabled the production of ultrafine denier fibers. Improvements in raw material selection and processing precision can enhance the uniformity of fiber structure and the stability of performance. In terms of equipment innovation, modular take-up roller design and multi-hole spinneret design can be used to improve production efficiency and fiber forming quality. Furthermore, functionalization is also a current hot topic. Companies have successfully endowed ultrafine denier polyester low-stretch yarn with diverse functions such as antistatic and antibacterial properties through blending, modification, or finishing techniques, further broadening its application areas.

[0004] However, despite some progress, the production of ultrafine denier polyester low-stretch yarn still faces numerous technical bottlenecks. Insufficient fiber uniformity is one of the most pressing issues to be addressed. Fineness fluctuations and end breakages, which can occur during high-speed spinning, affect product uniformity and subsequent weaving efficiency. Furthermore, functional requirements are not fully met. Existing functional fibers, such as those with antistatic properties and moisture absorption and quick-drying properties, lack stability, especially after repeated washing, and their performance degrades.

[0005] In response to the above problems, this technical solution is intended to be developed from multiple angles, including process optimization, functional integration, and equipment improvement, aiming to achieve improved uniformity in the fineness of ultra-fine denier polyester low-stretch yarn, enhanced functional durability, and reduced production costs, thereby solving the current technical bottlenecks and promoting the upgrading of ultra-fine denier polyester low-stretch yarn technology towards high performance and greenness, in line with the future textile industry's demand trend for high-value-added products. Summary of the Invention

[0006] The purpose of this application is to solve the problems of poor fineness uniformity and easy loss of functional components in ultrafine denier polyester low-stretch yarns through a staged stretching deformation process combining twisting with no twisting and a core-cladding layer composite spinning structure, thereby achieving precise control of fiber fineness. At the same time, core-shell structure auxiliary powders can be used to achieve long-term and stable anti-ultraviolet and antibacterial properties, taking into account both environmental protection and high added value of products. The purpose of this application is achieved through the following technical solutions. The preparation method of ultrafine denier polyester low-stretch yarns of this application includes: Polyester pellets are made by mixing raw material components and then melt-extruding and granulating them into polyester pellets. The raw material components include polyester chips, anti-ultraviolet agents, and antioxidants. Adding the polyester particles into a melt spinning machine to obtain fiber precursors by melt spinning; Perform the first stretching deformation, and use the false twisting machine to heat, stretch, cool and shape the original yarn for the first time. No twisting operation is performed during the first stretching deformation process; The second twisting and deformation is carried out, and the raw yarn is heated, twisted, cooled and shaped for the second time through the false twisting machine. The yarn that has undergone the second stretching and deformation is oiled and wound to obtain the preliminary polyester stretch yarn; The preliminary polyester stretch yarn is heated at a temperature within a range of 120-150° C. for more than 2 hours, and then cooled to obtain the polyester low-stretch yarn; The fiber fineness of the fiber precursor is within the range of 0.6-1 dtex, and the fiber fineness of the fiber after the first stretching deformation is controlled within the range of 0.3-0.5 dtex.

[0007] In one embodiment, fiber precursors including a core layer and a cladding layer are formed during the melt spinning process, specifically including forming the core layer by melt extrusion spinning of polyester particles in a spinneret, and forming the cladding layer on the surface of the core layer by solution spraying around the core layer ejection hole.

[0008] In one embodiment, the method further includes a step of cooling the gas at the ejection location.

[0009] In one embodiment, an auxiliary powder is further added to the raw material components, and the auxiliary powder has a core-shell structure, including a functional core and a coating shell.

[0010] In one embodiment, the material of the functional core is silver nanoparticles, rare earth compound nanoparticles or metal oxide nanoparticles.

[0011] In one embodiment, the temperature during the first stretching deformation process is in the range of 200°C-240°C, and the temperature during the second twisting deformation process is in the range of 160°C-200°C.

[0012] In one embodiment, functional powder is added to the coating solution.

[0013] The present application further provides an ultra-fine denier polyester low-stretch yarn, which is obtained by the aforementioned preparation method of the ultra-fine denier polyester low-stretch yarn, and the fiber fineness of the polyester low-stretch yarn is controlled within the range of 0.4-0.6 dtex.

[0014] In one embodiment, the polyester low-elastic yarn includes a core layer and a covering layer, the covering layer material includes a polyurethane polymer, and the thickness of the covering layer is within the range of 0.2-0.6 of the diameter of the core layer.

[0015] In one embodiment, the core layer and the coating layer include auxiliary powder, and the content of the auxiliary powder in the coating layer is greater than the content of the auxiliary powder in the core layer.

[0016] Compared with the prior art, this application has the following beneficial effects: This application solves the problem of poor fineness uniformity in ultrafine denier polyester low-stretch yarns through a staged stretching and texturing process that combines twisting with no twisting. During the first stretching and texturing process, no twisting is performed, avoiding fiber structure disorder and fineness fluctuations caused by twisting. This allows the fibers to achieve a relatively uniform fineness range after the initial stretching. The second twisting and texturing process allows for further adjustment of fiber fineness while imparting good elasticity and curl to the fibers, thereby ensuring fineness uniformity and quality stability in the final product.

[0017] Secondly, the design of a core-cladding composite spinning structure effectively solves the problem of functional component loss. During the melt spinning process, the core layer is formed by melt extrusion spinning of polyester pellets, while the cladding layer is formed on the core layer surface by solution spraying. This structure not only ensures the functional components are stably contained in the core layer, preventing loss of functional components due to the external environment, but also further enhances the durability and stability of the fiber through the protective effect of the cladding layer.

[0018] In addition, the present application also achieves long-term stability of anti-ultraviolet and antibacterial properties by adding core-shell structure auxiliary powder. The functional core material of the auxiliary powder has excellent antibacterial and anti-ultraviolet properties, while the coating shell protects the functional core and prevents its loss. It not only improves the utilization and stability of the functional components, but also enables the fiber to maintain good functional properties after multiple washing and use. It not only makes the preparation method of ultra-fine denier polyester low-elastic yarn of this application more environmentally friendly and efficient, but also provides a strong guarantee for its wide application in high-end clothing, sportswear, medical textiles and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is a schematic flow chart of a method for preparing ultra-fine denier polyester low-stretch yarn in one embodiment of the present application; Figure 2 It is a schematic flow chart of a method for preparing ultra-fine denier polyester low-stretch yarn in another embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. It will be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some, rather than all, structures related to the present application are shown in the accompanying drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0021] As used herein, the terms "comprise," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0022] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] With the continuous advancement of textile technology and the increasing demand of consumers for textile quality, ultra-fine denier polyester low-stretch yarn, as a high-performance fiber material, has attracted much attention due to its unique physical properties and broad application prospects. It not only has excellent softness, breathability and drape, but also can show good elasticity and recovery while maintaining high strength. It is an ideal material for making high-end clothing, sportswear, medical textiles, etc. However, in the production process of traditional ultra-fine denier polyester low-stretch yarn, it often faces problems such as poor uniformity of fineness and easy loss of functional components, which not only affects the quality and stability of the product, but also limits its application in a wider range of fields. In order to solve these problems, the present application proposes a new ultra-fine denier polyester low-stretch yarn and a preparation method thereof. Through the application of a staged stretching deformation process combining twisting and untwisting, a core-coating composite spinning structure and a core-shell structure auxiliary powder, the precise control of fiber fineness, the stable presence of functional components and the long-term maintenance of anti-ultraviolet and antibacterial properties are achieved. Next, the specific technical content of this ultra-fine denier polyester low-stretch yarn and its preparation method will be introduced in detail. Please refer to Figures 1 to 2 The method for preparing ultrafine denier polyester low-stretch yarn in a preferred embodiment of the present application includes: preparing polyester pellets, mixing raw material components and melt-extruding and granulating them to form polyester pellets, the raw material components including polyester polyester chips, an anti-ultraviolet agent, and an antioxidant; adding the polyester pellets to a melt spinning machine to obtain fiber precursors by melt spinning; performing a first stretching deformation, heating, stretching, and cooling the precursors for a first time through a false twisting machine, without twisting during the first stretching deformation process; performing a second twisting deformation, heating, twisting, and cooling the precursors for a second time through a false twisting machine, oiling and winding the yarns that have undergone the second stretching deformation to obtain preliminary polyester stretch yarn; heating the preliminary polyester stretch yarn, controlling the heating temperature within the range of 120-150°C for a heating time of more than 2 hours, and cooling after heating to obtain the polyester low-stretch yarn; wherein the fiber fineness of the fiber precursor is within the range of 0.6-1 dtex, and the fiber fineness of the fiber after the first stretching deformation is controlled within the range of 0.3-0.5 dtex.

[0024] The first step of the method of the present application is to prepare polyester pellets, which specifically includes uniformly mixing polyester polyester chips, anti-ultraviolet agents, and antioxidants, wherein the intrinsic viscosity of the polyester polyester chips can be selected within the range of 0.65-0.72 dL / g, the anti-ultraviolet agent can be a benzotriazole compound, and the addition amount is selected within the range of 0.5%-1.2wt%, and the antioxidant can be a hindered phenol, and the addition amount is selected within the range of 0.3%-0.8wt%, and the pellets are granulated at 240-260°C through a twin-screw melt extruder.

[0025] The particles are fed into a melt spinning machine, melted at 270-285°C, and then extruded through a porous spinneret to form fiber precursors. The aperture of the porous spinneret is selected in the range of 0.15-0.25mm, and the fineness of the fiber precursor is selected in the range of 0.6-1dtex. The precursor is heat-stretched at 200-240°C using a false twisting machine, and the stretching ratio is selected in the range of 1.8-2.2 times. Then, it is quickly cooled to below 50°C with nitrogen to set the shape, and the fineness is reduced to 0.3-0.5dtex. No twisting force is applied at this stage to avoid distortion of the fiber structure. Then, twist deformation is applied to the fiber at 160-200°C, and the twist degree is 800-1200. T / m, a spiral curled structure is formed by combining secondary stretching and water cooling. The stretch ratio in this step is selected to be less than 1.2 times or no stretching is performed. After oiling, it is wound into a preliminary stretch yarn. The preliminary stretch yarn is placed in a 120-150℃ hot box for a relaxation heat treatment for ≥2 hours to eliminate internal stress through molecular chain rearrangement. Finally, it is cooled to obtain an ultra-fine denier polyester low-stretch yarn with a fineness of 0.4-0.6 dtex.

[0026] This application utilizes a staged stretching and texturing process, specifically including an initial, high-temperature, twist-free stretch (200-240°C) and a secondary, low-temperature, twist-free stretch (160-200°C). The initial stretch reduces the risk of fiber breakage through high-temperature softening, and combined with high-ratio stretching, reduces the fineness from 0.6-1dtex to 0.3-0.5dtex. The secondary stretch involves twisting and shaping at low temperatures to avoid excessive shrinkage, ultimately stabilizing the fineness at 0.4-0.6dtex with a fluctuation rate of ≤±3%. The initial, twist-free stretch ensures consistent fiber orientation, while the secondary twist imparts a spiral curl structure, increasing the elastic recovery rate to over 88% and reducing the lint rate to below 0.5%. Through collaborative process-material innovation, while ensuring the homogenization of ultrafine denier fibers (CV value <3%), the directional enhancement and long-term stability of antibacterial and anti-UV functions are achieved.

[0027] In addition to UV inhibitors and antioxidants, other additives can also be included to enhance the overall performance of polyester low-stretch yarn. Specifically, antioxidants include hindered phenols and phosphites, two highly effective ingredients that effectively capture and neutralize free radicals, thereby preventing oxidative degradation of the nylon material during processing and use. Their addition level is controlled between 0.001wt% and 1wt% based on the weight of the polyester used. UV absorbers include organic aromatic compounds such as benzotriazoles and benzophenones, as well as inorganic pigments such as carbon black, zinc oxide, and titanium dioxide. These ingredients absorb or reflect UV energy, effectively preventing UV radiation-induced degradation of the nylon material. Similarly, their addition level is strictly controlled within the range of 0.001wt% to 1wt%. Light stabilizers include a variety of highly effective ingredients such as copper halides, hindered amines, phenols, benzophenones, and triazoles, further enhancing light stability and preventing photodegradation. Their addition level is also strictly controlled between 0.001wt% and 1wt%. The antistatic agent contains a variety of high-efficiency ingredients such as fatty alcohol phosphate, fatty alcohol oxyalkylene ether phosphate, fatty alcohol potassium phosphate, sodium lauryl sulfate, stearic acid glycerol monoester, lauryl oxyethylene ether phosphate potassium salt and polyethylene glycol. It can effectively prevent static electricity accumulation by reducing the surface resistance of nylon materials, ensuring the safety and stability of the material in specific application scenarios. Its addition amount is also controlled between 0.001wt% and 1wt%. By carefully selecting and precisely controlling the type and addition amount of additives, the antioxidant properties, UV resistance, light stability and antistatic properties have been improved.

[0028] In the melt spinning process, composite fiber precursors with both a core layer and a coating layer can be further formed. In the internal channel of the spinneret, high-quality polyester particles are melt-extruded through a controlled heating and melting mechanism to form the core layer of the fiber. When the core layer material is about to pass through the ejection hole of the spinneret, a coating layer composed of a specific solution is applied around the ejection hole of the core layer. The solution mainly includes polyurethane and may also include functional powders (such as antibacterial agents, anti-ultraviolet agents, etc.). By regulating the spraying speed and amount, it is ensured that the coating layer can fit evenly and tightly to the surface of the core layer.

[0029] The traditional method of forming the core layer through melt extrusion within the spinneret is integrated with a solution spraying technique that directly forms the coating layer through the outer layer. This not only allows for a high degree of customization of the coating layer composition (such as adjusting the ratio of polyurethane and the type and content of functional powders), but also ensures the simultaneous formation of the core and coating layers during the spinning process, greatly improving production efficiency and fiber structural uniformity. By precisely controlling the content of additives (such as antimicrobial agents and anti-UV agents) in the coating layer, it exhibits a different composition and distribution relative to the core layer (for example, the coating / core additive ratio can be optimized to 3:1 or even higher). At the same time, the core layer provides a long-term protective mechanism, effectively extending the functional durability of the fiber and achieving a perfect balance between immediate and long-term protection.

[0030] Polyurethane is used as the coating material, and its excellent adhesion and elasticity are tightly combined with the polyester core layer through a special interpenetrating network technology at the melt-solution interface. This combination can enhance the internal structural stability of the fiber and improve the peel strength between the coating and the core layer, ensuring that the structural integrity is maintained even under extreme conditions (such as high-intensity stretching, repeated bending, etc.). The peel strength can stably reach or exceed 8N / mm, effectively avoiding the occurrence of delamination problems, thereby improving the overall durability and application reliability of the fiber.

[0031] During the fiber manufacturing process, a gas cooling step is introduced at the ejection point during the spinning and forming steps to further optimize the fiber's performance. During the spinning stage, high-purity nitrogen is used for rapid and uniform cooling. Nitrogen has stable chemical properties, high heat conduction efficiency, and is not prone to chemical reactions with fiber materials. At the same time, to ensure the uniformity and stability of the fiber's internal structure, the fiber surface is quickly cooled after spinning through nitrogen cooling technology, effectively suppressing premature crystallization of the surface layer. This allows the fiber's core and cladding layers to maintain a more consistent rate during the crystallization process, thereby ensuring that the difference in crystallinity between the two is controlled within a range of less than 5%. This not only improves the overall uniformity of the fiber, but also improves the fiber's flexibility, making it 20% more flexible than fibers that do not use this technology.

[0032] The long heat relaxation setting process allows the molecular chains within the fiber to fully relax at a relatively low temperature, effectively eliminating the internal stress generated during the spinning process. After ≥2 hours of heat relaxation setting, the fiber's boiling water shrinkage is controlled to an extremely low level of ≤2.5%, which is better than the industry standard (the boiling water shrinkage of conventional products is generally ≥4%). Therefore, fibers produced using this technology can exhibit better dimensional retention during subsequent processing and use, reducing the risk of performance degradation or failure due to dimensional changes. The introduction of gas dynamic cooling and heat relaxation setting technology not only improves the fiber's flexibility and uniformity by regulating its crystallinity, but also enhances its dimensional stability by effectively eliminating internal stress.

[0033] In the raw material components for fiber preparation, core-shell structure auxiliary agent powder is further incorporated. The powder consists of a functional core and a coating shell to form a functional particle composite system. The core of the core-shell structure auxiliary agent powder is composed of silver nanoparticles, rare earth compound nanoparticles or metal oxide nanoparticles. These functional cores give the fiber antibacterial and special physical properties respectively. The coating shell can be made of polyacrylate material or alumina material. When alumina material is used, it is prepared by the sol-gel method. The core-shell structure auxiliary agent powder has good processing adaptability and can achieve selective melting under specific conditions.

[0034] These functional materials possess special functions. For example, during the melt spinning process, silver nanoparticles, as antimicrobial ingredients, are effectively dispersed in the fibers, providing antimicrobial properties. When coated silver nanoparticles are added, the antimicrobial rate remains relatively high even after 50 washes. The core-shell structure design not only protects the stability of the functional ingredients during fiber processing but also improves the utilization rate of additives. During high-temperature extrusion, the polyacrylate shell effectively isolates the functional core from direct contact with the external environment, preventing oxidative degradation of functional ingredients (such as silver nanoparticles and rare earth compounds). This increases the utilization rate of additives by over 30% compared to traditional methods, reducing production costs while further enhancing the functionality and durability of the fibers.

[0035] Specifically, the functional core material is silver nanoparticles, rare earth compound nanoparticles, or metal oxide nanoparticles. Silver nanoparticles are highly favored as antimicrobial materials due to their unique antimicrobial mechanism and high antimicrobial properties. They can effectively inhibit the growth and reproduction of bacteria, imparting long-lasting antimicrobial properties to fibers. Rare earth compound nanoparticles can impart specific optical, magnetic, or catalytic properties to fibers, thereby broadening their application areas. Metal oxide nanoparticles, such as titanium dioxide (TiO2) and zinc oxide (ZnO), are commonly used in fiber preparation to enhance their UV resistance and self-cleaning capabilities due to their excellent UV shielding properties and photocatalytic activity.

[0036] Silver nanoparticles (AgNPs) have a particle size of 20-50nm, are spherical / polyhedral, and are coated with sodium citrate (concentration 0.1%-0.5%) on the surface. The addition amount is selected in the range of 0.2%-0.8wt% (based on the total mass of the core-shell additive). The sodium citrate coating enhances dispersibility and prevents agglomeration during melt spinning. The core-shell structure shell (polyacrylate) partially melts at 270-285℃, releasing AgNPs. The antibacterial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is ≥80%, and the Ag⁺ sustained-release period exceeds 360 days. An addition amount of 0.5wt% can achieve the effect of 1.5wt% silver-based antibacterial agents in traditional processes, reducing costs by 50%. The shell barrier reduces direct contact of silver ions with the skin, and cytotoxicity (MTT method) is reduced to undetectable levels.

[0037] Rare earth metal compounds can be selected from lanthanide rare earth metal elements, with the content controlled in the range of 50ppm to 10%. Lanthanide rare earth metal compounds specifically refer to those rare earth elements that exist in the form of salts or complexes. Specifically, these compounds may include but are not limited to inorganic salts such as oxides, chlorides, nitrates, sulfates, and complexes formed with hydrated ions, organic ligands, etc. By precisely controlling the content of lanthanide rare earth metal elements, the performance of the compound can be optimized in different application scenarios. Rare earth compound nanoparticles can be selected from cerium oxide (CeO2), with a particle size of 30-80nm, cubic crystal form, Ce³+ / Ce 4 + mixed valence (ratio 1:2); yttrium-doped europium oxide (Y / Eu:CeO2): particle size 40-100nm, Eu doping amount 1%-3%, addition amount: 0.5%-1.5wt%, Ce³+ / Ce 4 Valence state conversion provides free radical capture, while Eu doping enhances UV absorption (absorption in the 300-400nm band increases by 40%). The fiber maintains a UPF value >50, maintaining a UPF >40 after 50 washes, outperforming traditional benzotriazole UV inhibitors (UPF <30 after 30 washes). Synergistically acting with hindered phenolic antioxidants, the fiber retains ≥88% of its breaking strength after 1000 hours of UV aging.

[0038] Metal oxide nanoparticles can be selected from zinc oxide (ZnO): particle size 50-150nm, rod-shaped structure, aspect ratio 3:1-5:1; titanium dioxide (TiO2): rutile type, particle size 20-60nm, surface silane modified (KH-570), addition amount: 1.0%-2.0wt%, ZnO rod-shaped structure enhances ultraviolet scattering (reflectivity increased by 25%), TiO2 surface silane modification improves the interfacial bonding strength with the polyester matrix, ZnO and TiO2 synergistically cover the entire UV-A / B / C band, and the UPF value reaches 60+; TiO2 decomposes organic matter on the fiber surface under sunlight, the water contact angle is <30° (super hydrophilic), the stain attachment rate is reduced by 70%, ZnO has no crystal transformation during melt spinning, and its functional stability is better than ordinary nano ZnO (easy to agglomerate and inactivate).

[0039] In addition, synergistic effects can be achieved through components, such as AgNPs and CeO2 compounding: Ag⁺ antibacterial and CeO2 anti-ultraviolet / anti-oxidation synergistically, ZnO and TiO2 compounding: UV reflection and scattering complement each other. Fibers also achieve antibacterial (Log 6 The product boasts antibacterial properties (UV protection factor (UPF) > 50), antioxidant properties (free radical scavenging rate > 90%), and self-cleaning properties (COD removal rate ≥ 60%). The melting point differences between the components can be controlled through a core-shell structure to avoid phase separation during high-temperature processing (SEM shows dispersion uniformity CV < 5%). A further technical solution utilizes a multi-layered core-shell structure, with silver nanoparticles as the core, coated with a rare earth compound, and the outermost layer coated with polyacrylate. Furthermore, when using multiple functional powders, the proportion of the powder formed by the silver nanoparticles is selected to be within the range of 50-70%.

[0040] During the thermoplastic processing of the material, the first stretching deformation process is controlled within the temperature range of 200°C to 240°C, ensuring that the material is in the appropriate range between its glass transition temperature (Tg) and melting temperature (Tm), allowing the material to have good ductility and plasticity while maintaining a certain strength. By stretching within this temperature range, the molecular chains can be effectively induced to orient along the stretching direction, enhancing the directional strength and toughness of the material. Subsequently, the second twisting deformation process is carried out within the temperature range of 160°C to 200°C to prevent the material from over-softening or melting due to excessive temperature, thereby maintaining its sufficient structural stability and processing operability. Within this temperature range, the material still has a certain fluidity, allowing the fibers or threads to be smoothly entangled and form a tight structure during the twisting process, while avoiding fiber breakage or loose structure caused by excessive temperature.

[0041] By controlling the temperature during the stretching and twisting process, the molecular orientation and internal structure of the material can be optimized, thereby improving its tensile strength, wear resistance, and fatigue resistance. Processing within an appropriate temperature range ensures that the material maintains stable physical and chemical properties during processing, reducing quality fluctuations caused by temperature changes. Reasonable temperature settings help shorten processing cycles and improve production efficiency. By optimizing processing parameters, energy consumption and production costs can be reduced. Stretching and twisting at appropriate temperatures can make the product surface smoother and more delicate, improving the overall aesthetics and feel of the product.

[0042] Specifically, functional powder is added to the coating solution. The functional powder needs to have good compatibility with the coating material and be able to give the coating specific functional properties, such as enhancing wear resistance, improving thermal conductivity, increasing electromagnetic shielding effect or imparting antibacterial properties. In order to achieve this goal, the functional powder is first pretreated, including surface modification, particle size control and necessary drying treatment to ensure that it can be evenly dispersed in the coating solution to avoid the occurrence of agglomeration. Subsequently, the functional powder is slowly added to the coating solution in a certain proportion, and efficient dispersing equipment, such as an ultrasonic disperser or a high-speed shear mixer, is used to promote the uniform distribution of the functional powder in the solution to form a stable and functionalized coating solution. By adding functional powder to the coating solution, the comprehensive performance of the coating, such as wear resistance, thermal conductivity, electromagnetic shielding effect or antibacterial properties, can be improved to meet the needs of specific application scenarios.

[0043] This application further provides an ultra-fine denier polyester low-stretch yarn, obtained by the aforementioned method for preparing ultra-fine denier polyester low-stretch yarn. The fiber fineness of the polyester low-stretch yarn is controlled within the range of 0.4-0.6 dtex. This ultra-fine denier polyester low-stretch yarn possesses the excellent abrasion resistance, wrinkle resistance, and UV resistance inherent to polyester fiber. Furthermore, due to its unique ultra-fine denier properties, it exhibits a more delicate feel, higher softness, and improved breathability. During the preparation process, fiber fineness is ensured by precisely controlling key parameters such as spinning speed, spinning temperature, and draw ratio. Raw materials are also screened and processed to ensure the quality and performance of the polyester low-stretch yarn.

[0044] Because the fiber fineness is strictly controlled within the range of 0.4-0.6 dtex, the polyester low-stretch yarn has a more delicate feel and higher softness. The ultrafine denier fibers are arranged more tightly and the gaps between the fibers are smaller. This structure makes the polyester low-stretch yarn have good breathability and can keep the skin dry and comfortable. The polyester fiber itself has excellent wear resistance and wrinkle resistance, and the ultrafine denier polyester low-stretch yarn further enhances these properties, making the textiles made from it more durable and easy to care for.

[0045] Specifically, the polyester low-stretch yarn includes a core layer and a coating layer. The coating layer material includes a polyurethane polymer, and the thickness of the coating layer is within the range of 0.2-0.6 of the core layer diameter. The polyurethane polymer selected as the coating layer material has excellent elasticity, wear resistance, and weather resistance. The polyurethane polymer has good compatibility and adhesion with the polyester core layer, ensuring the stability and durability of the coating layer. In terms of thickness design, the thickness of the coating layer is precisely controlled within the range of 0.2-0.6 times the core layer diameter. This ensures that the coating layer can fully exert its functionality, such as providing additional elasticity, wear resistance, and comfort, while avoiding the overall performance of the fiber or increased cost caused by an excessively thick coating layer. At the same time, by controlling the thickness of the coating layer, the feel and appearance of the polyester low-stretch yarn can also be fine-tuned to meet different application scenarios and the personalized needs of consumers. The polyurethane polymer coating significantly enhances the elasticity, wear resistance and weather resistance of polyester low-stretch yarn, so that the fiber has a wider application potential while maintaining basic mechanical properties. The presence of the coating makes the polyester low-stretch yarn feel softer and more delicate.

[0046] Specifically, the core layer and the coating layer include additive powders, with the coating layer containing a greater amount of additive powder than the core layer. The selection of additive powders encompasses a variety of types, including but not limited to UV inhibitors, antimicrobial agents, antistatic agents, and additives that enhance feel and gloss. The distribution and content of these additive powders differ between the core and coating layers. The additive powders in the core layer primarily enhance the fiber's basic mechanical properties and stability, such as increasing its strength and abrasion resistance, while the additive powders in the coating layer focus more on improving the fiber's surface properties and functionality, such as enhancing UV resistance and antimicrobial properties, and improving its feel and gloss. This differentiated distribution of additive powders in the core and coating layers achieves comprehensive optimization of the polyester low-stretch yarn's performance. The additive powders in the core layer ensure the fiber's basic mechanical properties and stability, while the additive powders in the coating layer enhance the fiber's surface properties and functionality. This allows the polyester low-stretch yarn to maintain high strength and abrasion resistance while possessing broader application potential. By precisely controlling the content and type of auxiliary powder, the performance of polyester low-stretch yarn can be precisely controlled to meet the personalized needs of different application scenarios and consumers. Specific embodiments

[0047] Some specific implementation methods will be further introduced below to further explain the technical solution of this application in detail.

[0048] Example 1

[0049] Polyester pellets were prepared using the following raw material composition: 97.5 wt% polyester chips (intrinsic viscosity 0.68 dL / g), 1.0 wt% UV inhibitor (benzotriazole UV-326), and 0.5 wt% antioxidant (hindered phenol Irganox 1010). The twin-screw extruder temperature zones were: 240°C for the feed section, 255°C for the melt section, and 260°C for the homogenization section. The screw speed was 250 rpm, and the pellet size was 2.5 mm × 3.0 mm.

[0050] The spinneret core layer had a 72-hole ring array with a diameter of 0.20 mm. The cladding layer had 80 μm holes in an outer ring of 48 holes, with a spacing of 0.4 mm between the core and cladding layers. Spinning parameters included a core layer melt temperature of 280°C, a cladding layer solution (TPU-85A aqueous dispersion + 5 wt% ZnO nanorods) preheated to 60°C, an extrusion speed of 1000 m / min for the core layer, and a fiber fineness of 0.8 dtex.

[0051] First untwisted stretching: Hot roll temperature: 225°C (three temperature zones: 220°C / 230°C / 220°C), draw ratio: 2.0x, post-stretch fineness: 0.4 dtex, nitrogen cooling: flow rate: 25 m / s, outlet temperature: 45°C. Second twisting texturing: Hot air temperature: 180°C, twist density: 1000 T / m (false twist disc speed: 8000 rpm), false twist machine configuration: friction disc material: ceramic, diameter: 60 mm, pitch: 1.2 mm, twist tension: 0.08 cN / dtex, overfeed ratio: +3%.

[0052] The film was placed in a hot box at a temperature of 135°C ± 1°C for 2.5 hours. The film was then cooled in a gradient process: first stage: 100°C / 15 minutes, second stage: 60°C / 15 minutes, and third stage: air cooling at room temperature. The oiling process consisted of a polyether-modified silicone oil (60%), an antistatic agent (20%), and an emulsifier (20%). The oiling rate was 0.6wt%, the oil roller temperature was 50°C, and the winding speed was 1200m / min.

[0053] Example 2

[0054] Based on Example 1, 1.0 wt% core-shell additive (AgNPs@polyacrylate, core-shell mass ratio 1:2) was added, the silver core particle size was 30 nm, sodium citrate coating (0.3 wt%) was used, the shell thickness was 80 nm, the emulsion polymerization temperature was 75°C, and the reaction time was 4 hours. The remaining parameters were the same as in Example 1.

[0055] Example 3

[0056] On the basis of Example 1, a functionalized coating layer spraying was further added: coating layer solution: water-based polyurethane (TPU-85A, solid content 20%), functional powder: AgNPs (3wt%) + ZnO nanorods (6wt%) + TiO2 (2wt%), dispersion process: high-pressure homogenization (120MPa, 3 cycles) + ultrasonic treatment (40kHz, 30 minutes), spraying pressure: 0.4MPa, coating layer thickness: 0.4 times the core layer diameter (core layer diameter 12μm→coating layer 4.8μm).

[0057] Comparative Example 1 The polyester raw material is added to a mixer for mixing, and after being evenly mixed, it is added to a hot melt spinning machine for spinning, and then cooled, oiled and wound to obtain polyester pre-oriented filaments, which are then spun into polyester pre-oriented filaments. The above polyester pre-oriented filaments are subjected to a texturing process on a texturing machine, the polyester pre-oriented filaments are subjected to a roller and heated in a first hot box at a temperature of 180-220°C, and then the heated polyester pre-oriented filaments are false-twisted, and then oiled and wound to obtain polyester high-elastic yarns. The above polyester high-elastic yarns are placed in a sealed container for heating, and the container temperature is heated from room temperature to 100-160°C in half an hour, and this temperature is maintained for at least 1 hour, and then the temperature is reduced to below 100°C, the DTY is taken out, and naturally cooled to room temperature to obtain polyester low-elastic yarns.

[0058] The polyester low-stretch yarn obtained in Examples 1 to 3 and Comparative Example 1 was tested for breaking strength, crimp shrinkage, boiling water shrinkage, and dry heat shrinkage. According to GB / T14344-2008 "Test method for tensile properties of chemical fiber filaments", the breaking strength of the test specimens was tested at a tensile speed of 500 mm / min, a clamping distance of 500 mm, and a pre-tension of 0.20 cN / dtex. -1 According to GB / T6506-2001 "Test method for shrinkage performance of synthetic textured yarn", the curl shrinkage rate and dry heat shrinkage rate of the sample were tested, and the yarn was shaken 11 times, and the drying temperature was 120°C and the drying time was 10 minutes. According to GB / T6505-2008 "Test method for thermal shrinkage of chemical fiber filaments", the boiling water shrinkage rate of the sample was tested, and the boiling time was 30 minutes. The specific test results are shown in Table 1.

[0059] Table 1 Performance data of polyester low-stretch yarn obtained in various examples

[0060] The above experimental results show that the ultra-fine denier polyester low-stretch yarn obtained by the technical solution of this application has better breaking strength, crimp shrinkage, dry heat shrinkage, and boiling water shrinkage. Compared with the technical solution of single-stretch deformation (Comparative Example 1), all these properties are improved. After adding the auxiliary powder (Example 2), all properties are improved to a certain extent, but the improvement is not significant. The polyester low-stretch yarn with a further coating layer has a significant improvement in breaking strength, crimp shrinkage, dry heat shrinkage, and boiling water shrinkage. In addition, the antibacterial rate of Examples 2 and 3 is 85.7%.

[0061] As can be seen from the foregoing, this application provides a high-performance ultrafine denier polyester low-stretch yarn and its preparation method, aiming to address the problems of poor fineness uniformity and easy loss of functional components in the traditional ultrafine denier polyester low-stretch yarn production process. Through the use of a staged stretching and deformation process combining twisting with and without twisting, a core-cladding composite spinning structure, and a core-shell structured auxiliary powder, this application achieves precise control of fiber fineness, stable presence of functional components, and long-term maintenance of anti-UV and antibacterial properties.

[0062] The preparation method involves first preparing polyester pellets containing polyester chips, an anti-UV agent, and an antioxidant, and then obtaining fiber precursors through melt spinning. Subsequently, the fibers are stretched and deformed in stages using a false twisting machine. The first high-temperature stretching without twisting reduces the risk of fiber breakage and achieves an initial reduction in fineness. The second low-temperature twisting stretching imparts a helical curl structure to the fibers and stabilizes fineness. Furthermore, gas cooling and heat relaxation techniques are introduced to further optimize fiber properties.

[0063] During the spinning process, a core-cladding structure is employed. The core is formed by melt-extrusion of polyester particles, while the cladding, which contains polyurethane and functional powders (such as antimicrobial and UV inhibitors), is applied to the core surface via solution spraying technology. This ensures the uniform distribution and durability of the functional ingredients. By controlling the content and type of additive powders in the cladding, comprehensive optimization of fiber performance is achieved. Another major innovation is the use of core-shell additive powders, which consist of a functional core (such as silver nanoparticles, rare earth compound nanoparticles, or metal oxide nanoparticles) and a coating shell (such as polyacrylate or aluminum oxide). This not only protects the stability of the functional ingredients during fiber processing but also improves the utilization rate of the additives.

[0064] The resulting ultrafine denier polyester low-stretch yarn has a fiber fineness within the range of 0.4-0.6 dtex and exhibits excellent softness, breathability, drape, and elastic recovery, while also exhibiting good antibacterial and UV resistance. This invention not only improves the quality and stability of ultrafine denier polyester low-stretch yarn but also broadens its application areas, making it an ideal material for high-end clothing, sportswear, medical textiles, and other applications.

[0065] The above is only a specific implementation of the present application. Any other improvements made based on the concept of the present application are considered to be within the scope of protection of the present application.

Claims

1. A method for preparing ultra-fine denier polyester low-stretch yarn, characterized in that: include: Polyester pellets are made by mixing raw material components and then melt-extruding and granulating them into polyester pellets. The raw material components include polyester chips, anti-ultraviolet agents, and antioxidants. Adding the polyester particles into a melt spinning machine to obtain fiber precursors by melt spinning; Perform the first stretching deformation, and use the false twisting machine to heat, stretch, cool and shape the original yarn for the first time. No twisting operation is performed during the first stretching deformation process; The second twisting and deformation is carried out, and the raw yarn is heated, twisted, cooled and shaped for the second time through the false twisting machine. The yarn that has undergone the second stretching and deformation is oiled and wound to obtain the preliminary polyester stretch yarn; The preliminary polyester stretch yarn is heated at a temperature within a range of 120-150° C. for more than 2 hours, and then cooled to obtain the polyester low-stretch yarn; The fiber fineness of the fiber precursor is within the range of 0.6-1 dtex, and the fiber fineness of the fiber after the first stretching deformation is controlled within the range of 0.3-0.5 dtex.

2. The method for preparing ultra-fine denier polyester low-elastic yarn according to claim 1, characterized in that: In the melt spinning process, fiber precursors including a core layer and a cladding layer are formed, specifically by using polyester particles to melt-extrusion-spin in a spinneret to form the core layer, and using a solution spraying method around the core layer ejection hole to form the cladding layer on the core layer surface.

3. The method for preparing ultra-fine denier polyester low-stretch yarn according to claim 2, characterized in that: The method also includes the step of cooling the gas at the ejection location.

4. The method for preparing ultra-fine denier polyester low-stretch yarn according to any one of claims 1 to 3, characterized in that: Auxiliary powder is also added to the raw material components. The auxiliary powder has a core-shell structure, including a functional core and a coating shell.

5. The method for preparing ultra-fine denier polyester low-stretch yarn according to claim 4, characterized in that: The material of the functional core is silver nanoparticles, rare earth compound nanoparticles or metal oxide nanoparticles.

6. The method for preparing ultra-fine denier polyester low-stretch yarn according to claim 1, characterized in that: The temperature during the first stretching deformation process is in the range of 200° C. to 240° C., and the temperature during the second twisting deformation process is in the range of 160° C. to 200° C.

7. The method for preparing ultra-fine denier polyester low-stretch yarn according to claim 2, characterized in that: Functional powder is added to the coating solution.

8. A superfine denier polyester low-elastic yarn, characterized in that: The polyester low-stretch yarn is obtained by the preparation method of any one of claims 1 to 7, wherein the fiber fineness of the polyester low-stretch yarn is controlled within the range of 0.4-0.6 dtex.

9. The ultra-fine denier polyester low-elastic yarn according to claim 8, characterized in that: The polyester low-elastic yarn includes a core layer and a covering layer. The covering layer material includes a polyurethane polymer. The thickness of the covering layer is within the range of 0.2-0.6 of the diameter of the core layer.

10. The ultra-fine denier polyester low-elastic yarn according to claim 9, characterized in that: The core layer and the coating layer include auxiliary powder, and the content of the auxiliary powder in the coating layer is greater than the content of the auxiliary powder in the core layer.

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