Cationic dyeable high-elastic hollow fiber and preparation method thereof

Abstract

The embodiment of the invention provides a cationic dyeable high-elastic hollow fiber and a preparation method thereof. The preparation method comprises the following steps: carrying out copolymerization modification on ethylene glycol terephthalate, 5-sulfoisophthalic acid sodium salt and 1, 4-cyclohexane glycol, simultaneously extruding a modified melt and a common polyester melt through a round hole and a C-shaped hole which are eccentrically parallel to each other, and carrying out side blowing cooling and after-treatment to directly form filaments. According to the method, the inherent crystallization and shrinkage difference of two components is utilized, and permanent three-dimensional curling is generated in the spinning forming process, so that high elasticity is obtained in one step, the damage to a hollow structure caused by a post-elasticizing process is thoroughly avoided, and the light weight and warm keeping characteristics of the fiber are completely maintained. Meanwhile, sulfonate groups in the modified components enable the fibers to have dyeability of cationic dyes, the fibers are combined with the dyeability of disperse dyes of common components, a uniform double-color effect can be achieved on a single fiber, the processing applicability is high, and the diversified requirements of high-end textiles are met.

Description

Technical Field

[0001] This invention relates to the field of chemical fiber manufacturing technology, and in particular to a cationic dyeable high-elasticity hollow fiber and its preparation method. Background Technology

[0002] Hollow fibers, especially hollow polyester fibers, possess excellent warmth retention and lightweight properties due to the effective heat insulation provided by the trapped air layer within them. They have become an indispensable raw material in high-end thermal comforters, down jacket fillings, outdoor jacket linings, and various lightweight thermal garments. With the increasing demands of the consumer market for multifunctional, comfortable, and aesthetically pleasing textiles, developing hollow fibers that combine excellent warmth retention, good elasticity, and rich dyeing options has become an important research direction in the field of textile materials.

[0003] Currently, the conventional hollow fiber production process in the industry mainly involves extruding polyester (PET) melt through specially shaped spinnerets, utilizing the melt's own "Ballas effect" to expand and bond, forming a hollow structure, and then hot-stretching it into fully drawn yarn (FDY). However, conventional hollow FDY fibers obtained through this method do not inherently possess elasticity. To impart elasticity, additional texturing machines are required for complex post-processing, using high-temperature heating chambers and high-speed mechanical friction from false twisters to cause the filaments to curl and deform. This post-processing is a common technical route in the field for obtaining elastic hollow yarns.

[0004] The aforementioned method of imparting elasticity to hollow FDY using a texturing machine has significant drawbacks. First, under the high-speed rotational friction of the false twister disc and the high temperature of the hot box, the fiber, especially its fragile hollow tube wall, is subjected to enormous shear force and thermal stress, which can easily lead to tube wall rupture, compression deformation, or collapse of the hollow structure, resulting in a significant reduction in the fiber's core advantage—warmth retention. Second, this drastic post-processing process can easily cause uneven damage to the fiber structure, leading to poor uniformity in subsequent dyeing. Furthermore, in terms of dyeing style, conventional polyester fibers can only be dyed with disperse dyes, resulting in a limited color range. To achieve a two-color effect, the industry typically requires blending hollow fibers with cationic dyeable fibers on a texturing machine. This process is not only complex and costly, but also imposes more processing limitations on blending (e.g., often limited to coarser specifications) and further exacerbates the damage to the hollow structure. Therefore, how to directly prepare hollow fibers with both high elasticity and cationic dyeability in a one-step process without damaging the hollow structure has become a pressing problem to be solved in existing technologies. Summary of the Invention

[0005] In view of the above problems, a cationic dyeable high-elasticity hollow fiber and its preparation method are proposed to overcome or at least partially solve the above problems. Specifically: A method for preparing cationic dyeable high-elasticity hollow fibers includes: S1. Using purified terephthalic acid and ethylene glycol as raw materials, sodium isophthalate-5-sulfonate accounting for 1% to 3% of the molar amount of purified terephthalic acid and 1,4-cyclohexanediol accounting for 5% to 10% of the molar amount of purified terephthalic acid are introduced as comonomers during the polymerization process, and modified polyethylene terephthalate melt is obtained through esterification reaction and polycondensation reaction; S2. Modified polyethylene terephthalate melt and unmodified polyethylene terephthalate melt are transported to metering pump through melt distribution pipe after passing through melt pump, booster pump and melt cooler. S3. After being metered by a metering pump, the modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt are transported to the spinning assembly and extruded through a spinneret composed of eccentrically arranged round holes and C-shaped holes. The two melts bond together at the spinneret outlet to form a composite melt stream. In this process, the modified polyethylene terephthalate melt is extruded from a round hole, while the unmodified polyethylene terephthalate melt is extruded from a C-shaped hole; the mass ratio of the extruded amount of the modified polyethylene terephthalate melt to the unmodified polyethylene terephthalate melt is 40:60 or 50:50. S4. The composite melt stream is cooled by side blowing from one side of the round hole, and the cooled composite melt stream is oiled, stretched, networked and wound to obtain cationic dyeable high elastic hollow fiber.

[0006] Optionally, step S1 specifically includes: Purified terephthalic acid, ethylene glycol, and 1,4-cyclohexanediol are mixed to form a slurry. A catalyst and stabilizer are added to the slurry, and an esterification reaction is carried out under pressure at 250°C to 260°C. The molar ratio of purified terephthalic acid to ethylene glycol is 1:1.2 to 1:2.0, and the pressure is atmospheric pressure to 0.3 MPa. When the amount of distilled water reaches more than 90% of the theoretical value, add sodium isophthalic acid-5-sulfonate to the reaction system and maintain stirring for 25 to 30 minutes. The pressure was then reduced to below 500 Pa absolute pressure, and the first stage of polycondensation reaction was carried out at 260°C to 270°C for 30 to 50 minutes. The pressure is further reduced to below 100 Pa absolute pressure, while the temperature is raised to 275°C to 285°C to carry out the second stage of polycondensation reaction for 50 to 90 minutes, thereby obtaining modified polyethylene terephthalate melt.

[0007] Optionally, the catalyst is any one of antimony trioxide, antimony glycolate, or antimony acetate, and the amount of catalyst added is 0.01%-0.05% of the mass of purified terephthalic acid.

[0008] Optionally, the stabilizer is any one of triphenyl phosphate, trimethyl phosphate or trimethyl phosphite, and the amount of stabilizer added is 0.01%-0.05% of the mass of purified terephthalic acid.

[0009] Optionally, the opening width of the C-shaped hole is 0.15-0.25mm, the outer diameter is 0.45-0.5mm, and the inner diameter is 0.3-0.35mm; the diameter of the round hole is 0.25-0.3mm, and the shortest distance between the round hole and the C-shaped hole is 0.07-0.08mm.

[0010] Optionally, the height of the windless zone of the spinneret is 50-70mm.

[0011] Optionally, in step S4, the pressure of the side-blowing air is 50-60 Pa and the temperature is 25-30 °C.

[0012] Optionally, in step S4, The height of the oil rack during the oiling process is 900-1200mm; The stretching process uses two-stage hot rollers for hot stretching, with the temperature of the first hot roller being 60-80℃ and the temperature of the second hot roller being 120-140℃, and the stretching ratio being 2-3 times. The spinning speed in the winding process is 2500-2800 m / min.

[0013] Optionally, the spinning temperature of the modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt before extrusion is 260-280℃, and the initial pressure of the spinneret is 8-12 MPa.

[0014] A cationic dyeable high-elasticity hollow fiber is prepared by any of the methods described above.

[0015] This invention provides a cationic dyeable high-elasticity hollow fiber and its preparation method. The fiber is modified by copolymerizing polyethylene terephthalate with sodium isophthalate-5-sulfonate and 1,4-cyclohexanediol. The modified melt and ordinary polyester melt are simultaneously extruded through eccentrically arranged circular and C-shaped orifices, cooled by side blowing, and directly filamentized after post-treatment. This method utilizes the inherent crystallization and shrinkage differences between the two components to spontaneously generate permanent three-dimensional crimp during the spinning process, thereby achieving high elasticity in one step. This completely avoids the damage to the hollow structure caused by the post-texturing process, fully preserving the fiber's lightweight and warm-retaining properties. Simultaneously, the sulfonate groups in the modified components endow the fiber with cationic dyeability. Combined with the disperse dyeability of the ordinary components, a uniform two-color effect can be achieved on a single fiber, and the fiber has strong processing applicability, meeting the diverse needs of high-end textiles. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for preparing cationic dyeable high-elasticity hollow fibers according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an eccentric combination of a circular hole and a C-shaped hole provided in an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of a spinneret provided in an embodiment of the present invention; Figure 4 This is a cross-sectional view of modified PET and PET extruded side by side from a spinneret according to an embodiment of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 This invention provides a method for preparing cationic dyeable high-elasticity hollow fibers, which may specifically include the following steps: S1. Using purified terephthalic acid and ethylene glycol as raw materials, sodium isophthalate-5-sulfonate (1% to 3% of the molar amount of purified terephthalic acid) and 1,4-cyclohexanediol (5% to 10% of the molar amount of purified terephthalic acid) are introduced as comonomers during the polymerization process. Modified polyethylene terephthalate melt is obtained through esterification and polycondensation reactions.

[0020] In an embodiment of the present invention, step S1 may specifically include: Purified terephthalic acid, ethylene glycol, and 1,4-cyclohexanediol are mixed to form a slurry. A catalyst and stabilizer are added to the slurry, and an esterification reaction is carried out under pressure at 250°C to 260°C. The molar ratio of purified terephthalic acid to ethylene glycol is 1:1.2 to 1:2.0, and the pressure is atmospheric pressure to 0.3 MPa. When the amount of distilled water reaches more than 90% of the theoretical value, add sodium isophthalic acid-5-sulfonate to the reaction system and maintain stirring for 25 to 30 minutes. The pressure was then reduced to below 500 Pa absolute pressure, and the first stage of polycondensation reaction was carried out at 260°C to 270°C for 30 to 50 minutes. The pressure is further reduced to below 100 Pa absolute pressure, while the temperature is raised to 275°C to 285°C to carry out the second stage of polycondensation reaction for 50 to 90 minutes, thereby obtaining modified polyethylene terephthalate melt.

[0021] In practical applications, firstly, PTA and EG can be added to a polymerization reactor equipped with a stirrer, heating device, and fractionation device at a molar ratio of purified terephthalic acid (PTA) to ethylene glycol (EG) of 1:1.2 to 1:2.0. Simultaneously, 1,4-cyclohexanediol (CHDM) is added as a comonomer at 5% to 10% of the molar weight of PTA. As an alicyclic diol, CHDM's rigid cyclic structure can effectively insert into and break the originally regular benzene ring sequence in the PET backbone, thereby significantly impairing its crystallinity.

[0022] Subsequently, a catalyst was added to accelerate the reaction, and a stabilizer was added to suppress thermal degradation and side reactions at high temperatures. Under a slightly positive nitrogen atmosphere ranging from atmospheric pressure to 0.3 MPa, the mixture was gradually heated to 250°C to 260°C for esterification. This pressurized environment facilitated the reflux of EG, promoted the dissolution of PTA and the esterification reaction, and prevented premature distillation of low-boiling-point components. During the reaction, water generated during esterification was continuously distilled off. By monitoring the amount of distilled water, when the measured value reached more than 90% of the theoretically calculated value (based on the amount of water generated during complete esterification), the esterification reaction was considered essentially complete. At this point, the system had formed a mixture mainly composed of diethyl terephthalate and its copolymer oligomer with CHDM.

[0023] Next, the sulfonate monomer is introduced. After confirming the esterification endpoint, sodium isophthalic acid-5-sulfonate (SIPM) at 1% to 3% of the molar amount of PTA is added uniformly to the reaction system. The system temperature is maintained, and stirring is continued for 25 to 30 minutes. The purpose of this operation is to ensure that SIPM is fully dispersed and initially participates in the end-group reaction. It can be understood that the introduction of SIPM has a dual effect: firstly, the meta-benzene ring and sulfonic acid groups in its molecular structure further disrupt the regularity of the PET chain, synergistically reducing the crystallinity and melting point of the polymer with CHDM; secondly, the sulfonate anion it carries (-SO3) - This introduces strongly polar sites into the polymer chain, which can firmly bind to the positively charged groups in cationic dyes through ionic bonds, thus fundamentally endowing the modified PET component with dyeability for cationic dyes. Adding SIPM too early may cause decomposition or side reactions during the high-temperature esterification stage; therefore, it is added after esterification is complete.

[0024] Finally, a phased polycondensation reaction is carried out to construct the polymer chain. After esterification and SIPM dispersion, a vacuum procedure is initiated for polycondensation. The first stage (low vacuum stage) of polycondensation is performed: the pressure of the reaction system is steadily reduced to below 500 Pa, the temperature is controlled at 260°C to 270°C, and the reaction lasts for 30 to 50 minutes. In this stage, under reduced pressure, oligomers undergo condensation by removing EG, and the molecular weight begins to increase significantly. Subsequently, the second stage (high vacuum stage) of polycondensation begins: the absolute pressure of the system is further reduced to below 100 Pa, while the reaction temperature is slowly increased to 275°C to 285°C, and the reaction continues for 50 to 90 minutes under these conditions. The high vacuum efficiently removes the reaction byproduct EG, greatly shifting the polycondensation equilibrium towards the formation of high molecular weight polymers. It is understandable that too low a temperature or insufficient time will result in a melt viscosity (intrinsic viscosity) that does not meet spinning requirements; too high a temperature or too long a time can easily cause thermal oxidative degradation and excessive end-capping, affecting melt quality and spinnability. Through this two-stage polycondensation, a modified PET melt with suitable intrinsic viscosity and controllable molecular weight distribution is finally obtained. Due to the copolymerization of CHDM and SIPM, the melting point, crystallinity, and melt viscosity of this melt are significantly lower than those of conventional PET, while ensuring that it retains its chemical nature of being dyeable with cationic dyes.

[0025] In a preferred embodiment of the present invention, the catalyst is any one of antimony trioxide, antimony glycolate, or antimony acetate, and the amount of catalyst added is 0.01%-0.05% of the mass of purified terephthalic acid. The stabilizer is any one of triphenyl phosphate, trimethyl phosphate, or trimethyl phosphite, and the amount of stabilizer added is 0.01%-0.05% of the mass of purified terephthalic acid.

[0026] It is understandable that antimony-based catalysts can significantly reduce the activation energy of esterification and polycondensation reactions, accelerating the formation of ester bonds between terephthalic acid (PTA) and ethylene glycol (EG) and 1,4-cyclohexanediol (CHDM), as well as the reaction rate of subsequent oligomer polycondensation to form polymer chains. Stabilizers can inhibit or delay the thermal oxidative degradation and thermal degradation of polymers in the high-temperature molten state. During polymerization processes lasting several hours at temperatures as high as 285°C, PET macromolecular chains may break, and end groups may oxidize, leading to a decrease in molecular weight, fluctuations in melt viscosity, yellowing, and the formation of gel particles. These all severely impair subsequent spinnability and fiber quality. The selected phosphate or phosphite stabilizers can effectively stabilize the melt by capturing free radicals, passivating metal ions with catalytic degradation effects (such as antimony ions from the catalyst), or reacting with unstable end groups of the polymer.

[0027] S2. Modified polyethylene terephthalate melt and unmodified polyethylene terephthalate melt are transported to metering pump through melt distribution pipe after passing through melt pump, booster pump and melt cooler.

[0028] Specifically, after preparing the modified polyethylene terephthalate melt, it and the unmodified polyethylene terephthalate melt can be separately drawn out via melt pumps. These melt pumps ensure a constant, non-pulsating volumetric flow rate of melt output from the polymerization reactor outlet. The speed of the melt pumps can be set according to the required base flow rate.

[0029] Next, the melt enters the booster pump. The booster pump is similar to the melt pump in structure and principle, but its functional focus is different. Its main task is to pressurize the melt to overcome the resistance drop generated by the melt flowing in the subsequent pipelines (including melt coolers and distribution pipes), and to ensure that the melt still has sufficient pressure when it reaches the spinning position to meet the stable pressure conditions required by the metering pump inlet.

[0030] Subsequently, the pressurized, high-temperature melt enters the melt cooler. The melt cooler can employ a shell-and-tube heat exchange structure, with the melt flowing through the tubes and the cooling medium (such as biphenyl-diphenyl ether heat transfer medium) flowing through the shell. Its purpose is to cool and regulate the melt. Understandably, the melt temperature exiting the polymerization reactor is relatively high (e.g., modified melt approximately 275-285°C, and conventional melt may be even higher), while the temperature directly used for spinning typically needs to be appropriately reduced to the range of 260-280°C. Through the regulation of the melt cooler, the melt temperature can be adjusted to a suitable range for spinning viscosity, preventing thermal degradation of the melt while it remains in the tubes due to excessive temperature. Simultaneously, it ensures that the melt temperature entering each spinning station is uniform, thereby further guaranteeing fiber evenness.

[0031] The cooled and pressure-stabilized melt is delivered to the metering pump at the corresponding spinning position through the melt distribution pipe. The melt distribution pipe can be a branched pipe network system, starting from the main pipe at the outlet of the booster pump, and distributing the melt to the spinning position through manifolds and branch pipes.

[0032] S3. After being metered by a metering pump, the modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt are transported to the spinning assembly and extruded through a spinneret composed of eccentrically arranged round holes and C-shaped holes. The two melts bond together at the spinneret outlet to form a composite melt stream. In this process, the modified polyethylene terephthalate melt is extruded from a round hole, while the unmodified polyethylene terephthalate melt is extruded from a C-shaped hole; the mass ratio of the extruded amount of the modified polyethylene terephthalate melt to the unmodified polyethylene terephthalate melt is 40:60 or 50:50.

[0033] In a preferred embodiment of the invention, the opening width of the C-shaped hole is 0.15-0.25 mm, the outer diameter is 0.45-0.5 mm, and the inner diameter is 0.3-0.35 mm; the diameter of the circular hole is 0.25-0.3 mm, and the shortest distance between the circular hole and the C-shaped hole is 0.07-0.08 mm. The height of the windless zone of the spinneret is 50-70 mm.

[0034] In a preferred embodiment of the present invention, the spinning temperature of the modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt before extrusion is 260-280°C, and the initial pressure of the spinneret is 8-12 MPa.

[0035] In practical applications, modified PET melt and conventional PET melt (i.e., unmodified polyethylene terephthalate melt) are metered by a metering pump and then conveyed to the spinning assembly. The core of this spinning assembly is the spinneret, which is machined with several sets of spinneret micro-orifice units. Each set of units consists of a round orifice and a C-shaped orifice arranged eccentrically side-by-side in a tightly packed manner. (Refer to...) Figure 2 and Figure 3 During the extrusion process, the modified PET melt is extruded through round orifices, while the conventional PET melt is extruded through C-shaped orifices. At the instant the two melts leave their respective micropores, due to their high-temperature viscous flow state and extremely close orifice spacing, they adhere to each other at their interface, fusing into a composite melt stream. (Refer to...) Figure 4 The extrusion rates of the two melts are controlled by metering pumps upstream of each, with a mass ratio of 40:60 or 50:50. It can be understood that if the modified component accounts for too low a percentage (<40%), the shrinkage force it provides is insufficient, leading to a decrease in the crimp elasticity of the final fiber; if the percentage is too high (>50%), it will excessively compress the hollow cavity space formed by the C-shaped holes, resulting in a decrease in hollowness, and may also affect spinning stability due to a relative lack of supporting components (conventional PET).

[0036] In embodiments of the invention, the opening width of the C-shaped orifice (i.e., the size of the C-shaped notch) is 0.15-0.25 mm, the outer diameter is 0.45-0.5 mm, and the inner diameter is 0.3-0.35 mm. These dimensions determine the wall thickness and cavity size of the hollow tubular preform formed by extruding conventional PET melt. A parallel circular orifice, with a diameter of 0.25-0.3 mm, is used for extruding modified PET melt. It is understood that the eccentric design of the C-shaped and circular orifices results in an asymmetrical distribution of the two polymers on the composite cross-section, providing a clear directionality for subsequent uneven stress release and three-dimensional curling caused by shrinkage differences, thereby maximizing the filament curling performance.

[0037] The height of the windless zone from the spinneret surface to the initial contact point of the cooling air is set to 50-70mm. This distance provides the necessary time and space for the melt stream to undergo natural rheological expansion (Ballers effect) and initial morphological stabilization without the interference of forced cooling, which allows the hollow structure to form smoothly and the two components to bond well.

[0038] In one or more embodiments of the present invention, the spinning temperature of both melts is maintained at 260-280°C before entering the spinneret. The initial spinneret pressure (i.e., the pressure of the melt at the spinneret inlet) is maintained at 8-12 MPa. This pressure range ensures that the melt can overcome the enormous resistance of the microporous channels and be stably extruded with sufficient speed and shear force to form a uniform fine stream.

[0039] S4. The composite melt stream is cooled by side blowing from one side of the round hole, and the cooled composite melt stream is oiled, stretched, networked and wound to obtain cationic dyeable high elastic hollow fiber.

[0040] In step S4, the pressure of the side-blowing air is 50-60 Pa, and the temperature is 25-30℃. The height of the oiling rack in the oiling process is 900-1200 mm; the stretching process uses two-stage hot rollers for hot stretching, where the temperature of the first hot roller is 60-80℃, the temperature of the second hot roller is 120-140℃, and the stretching ratio is 2-3 times; the spinning speed in the winding process is 2500-2800 m / min.

[0041] Specifically, after the composite melt stream leaves the spinneret, it immediately enters the curing and post-processing stage: First, the composite melt stream is cooled by side-blowing air, with the cooling air blowing from the circular orifice (i.e., the side from which the modified PET component is extruded) towards the composite stream. This is understandable because modified PET has a low melting point and slow crystallization; intensified cooling from one side first can more quickly "freeze" the morphology of the melt on that side, allowing its molecular chains to maintain a higher entropy random state during extrusion to a greater extent, thus preserving greater potential for thermal shrinkage in subsequent processes. Conventional PET side cooling is relatively slower, which is more conducive to the fuller orientation and crystallization of its molecular chains, providing a rigid framework for the fiber. The side-blowing air pressure is controlled at 50-60 Pa and the temperature at 25-30℃. Insufficient pressure or excessive temperature will lead to inadequate cooling, slow filament solidification, and easy adhesion or deformation; excessive pressure or excessive temperature may lead to excessively rapid cooling, excessive temperature difference between the skin and core layers, generating internal stress, and even causing filament vibration, affecting yarn uniformity. The cooling air can be filtered and its temperature and humidity regulated to maintain a stable state.

[0042] After cooling and curing, the filaments immediately enter the oiling process. A specialized spinning oil is evenly applied to the fiber surface through the oil nozzle. The oiling rack height (the distance from the spinneret surface to the center of the upper oil nozzle) is set to 900-1200mm to ensure that the filaments are fully cooled and cured before contacting the oil, preventing deformation of incompletely cured filaments due to the impact of the oil. The main function of the oil is to impart smoothness, bundled properties, and antistatic properties to the fibers, providing necessary lubrication and protection for subsequent high-speed stretching and winding.

[0043] Furthermore, this embodiment of the invention can employ a two-stage hot roller process for thermal stretching. The filament first contacts the first hot roller, whose surface temperature is controlled at 60-80°C. At this temperature, the fiber (especially the conventional PET component) is heated above its glass transition temperature, enhancing the mobility of the macromolecular chain segments. Orientation occurs under the tension generated by the difference in roller speeds, and the fiber strength begins to increase, but crystallization is not yet complete. Subsequently, the filament enters the second hot roller, where the setting temperature significantly increases to 120-140°C. At this high temperature, the molecular chains that have undergone preliminary orientation, especially the molecular chains of the conventional PET component, gain sufficient energy for rearrangement and crystallization, thereby "freezing" the orientation structure generated by stretching, achieving setting, and obtaining the final mechanical properties and dimensional stability. The stretching ratio (i.e., the ratio of the surface linear velocity of the second hot roller to that of the first hot roller) throughout the process is 2-3 times. This ratio range ensures that the fiber obtains the necessary orientation and strength, while avoiding the collapse of the hollow structure due to overstretching or the loss of shrinkage and resilience of the modified component due to overstretching.

[0044] After stretching and setting, the filaments pass through a networker. Here, the filaments are blown by a high-speed airflow, causing the monofilaments to entangle and bind together, forming periodic network nodes. This networking process significantly improves the bundle cohesion of the fiber, reduces fuzz in subsequent textile processing, and increases the fiber's fluffiness.

[0045] Finally, the fibers, after being processed by the spinning process, are wound onto a bobbin at a high speed of 2500-2800 m / min to produce fully drawn yarn (FDY). This high-speed winding ensures production efficiency and stable fiber tension. Through the continuous and coordinated action of the above S4 step, the eccentric composite melt stream of "modified PET / conventional PET" formed in the S3 step is asymmetrically cooled and solidified in its initial form. Then, through hot stretching, it achieves high strength while storing internal stress caused by the difference in shrinkage between the two components. Ultimately, when the external force is removed (after winding) and during subsequent dyeing and finishing heating, this internal stress is released, resulting in high macroscopic crimp elasticity of the fiber, while its hollow structure is completely preserved, and it possesses the cationic dyeability brought about by chemical modification.

[0046] This invention also provides a cationic dyeable high-elasticity hollow fiber, prepared by any of the methods described above.

[0047] This invention provides a cationic dyeable high-elasticity hollow fiber and its preparation method. The fiber is modified by copolymerizing polyethylene terephthalate with sodium isophthalate-5-sulfonate and 1,4-cyclohexanediol. The modified melt and ordinary polyester melt are simultaneously extruded through eccentrically arranged circular and C-shaped orifices, cooled by side blowing, and directly filamentized after post-treatment. This method utilizes the inherent crystallization and shrinkage differences between the two components to spontaneously generate permanent three-dimensional crimp during the spinning process, thereby achieving high elasticity in one step. This completely avoids the damage to the hollow structure caused by the post-texturing process, fully preserving the fiber's lightweight and warm-retaining properties. Simultaneously, the sulfonate groups in the modified components endow the fiber with cationic dyeability. Combined with the disperse dyeability of the ordinary components, a uniform two-color effect can be achieved on a single fiber, and the fiber has strong processing applicability, meeting the diverse needs of high-end textiles. The above is the overall concept of the present invention. For ease of understanding, the present invention also provides the following embodiments:

[0048] 1. Raw material preparation and modified PET polymerization In a continuous polymerization unit, purified terephthalic acid (PTA) and ethylene glycol (EG) were used as the basic raw materials, with a PTA to EG molar ratio of 1:1.5. 1,4-cyclohexanediol (CHDM) at 8% of the molar weight of PTA was added to the reaction system as a comonomer, along with antimony glycolate at 0.03% of the PTA mass as a catalyst and triphenyl phosphate at 0.02% of the PTA mass as a stabilizer. The mixture was heated to 255°C under nitrogen pressure of 0.2 MPa for esterification. The esterification reaction was completed when the distillate water reached 92% of the theoretical value. Subsequently, sodium isophthalate-5-sulfonate (SIPM) at 2% of the molar weight of PTA was added to the system, and the mixture was stirred thoroughly for 28 minutes. The system then enters the polycondensation stage: first, it reacts for 40 minutes at an absolute pressure of 400 Pa and a temperature of 265°C; then, in the high vacuum stage, the absolute pressure is reduced to below 80 Pa and the temperature is raised to 280°C, and the reaction continues for 70 minutes, finally obtaining a modified polyethylene terephthalate (modified PET) melt with an intrinsic viscosity of 0.62 dL / g.

[0049] 2. Melt conveying and metering The modified PET melt obtained above and the conventionally produced unmodified PET melt (intrinsic viscosity 0.68 dL / g) are transported separately. Both melts are first stably output by their respective melt pumps, then pressurized to approximately 10 MPa by booster pumps, and subsequently enter melt coolers where the temperatures are precisely adjusted to 268℃ (modified PET) and 272℃ (conventional PET). The temperature-adjusted melts are then evenly distributed to each spinning station through precisely designed melt distribution pipes and enter their respective independent metering pumps.

[0050] 3. Parallel composite spinning and cooling setting At the spinning station, modified PET melt and conventional PET melt are precisely metered by a metering pump, controlling their mass output ratio to be 40:60. The two melts are fed to a specially designed spinning assembly whose spinneret is machined with a combination of eccentrically arranged circular and C-shaped micro-orifices. The circular orifices have a diameter of 0.28 mm, the C-shaped orifices have an opening width of 0.20 mm, an outer diameter of 0.48 mm, an inner diameter of 0.35 mm, and a minimum distance of 0.075 mm between the two orifices. The modified PET melt is extruded from the circular orifices, and the conventional PET melt is extruded from the C-shaped orifices, immediately bonding together at the outlet to form a single composite melt stream. The initial pressure on the spinneret is 10 MPa. Subsequently, the composite stream is cooled by side-blowing air from one side of the circular orifices at a cooling air pressure of 55 Pa and a temperature of 28°C, with a windless zone height of 60 mm below the spinneret.

[0051] 4. Post-processing and winding After cooling and curing, the filaments are oiled at a height of 1100 mm above the spinneret. The filaments then undergo hot stretching via two stages of hot rollers: the first roller reaches 70°C, and the second roller (setting roller) reaches 130°C, with the stretch ratio controlled at 2.5 times. After stretching and setting, the filaments are fed into a network structure by a spinning device, and finally wound at a spinning speed of 2650 m / min to produce the cationic dyeable high-elastic hollow fiber product.

[0052] The above provides a detailed description of a cationic dyeable high-elastic hollow fiber and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing cationic dyeable high-elasticity hollow fibers, characterized in that, The method includes: S1. Using purified terephthalic acid and ethylene glycol as raw materials, sodium isophthalate-5-sulfonate accounting for 1% to 3% of the molar amount of the purified terephthalic acid and 1,4-cyclohexanediol accounting for 5% to 10% of the molar amount of the purified terephthalic acid are introduced as comonomers during the polymerization process, and modified polyethylene terephthalate melt is obtained through esterification reaction and polycondensation reaction; S2. The modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt are transported to the metering pump through the melt distribution pipe after passing through the melt pump, the booster pump, and the melt cooler. S3. After being metered by the metering pump, the modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt are transported to the spinning assembly and extruded through a spinneret composed of eccentrically arranged round holes and C-shaped holes. The two melts bond together at the spinneret outlet to form a composite melt stream. The modified polyethylene terephthalate melt is extruded from the circular orifice, and the unmodified polyethylene terephthalate melt is extruded from the C-shaped orifice; the mass ratio of the extruded amount of the modified polyethylene terephthalate melt to the unmodified polyethylene terephthalate melt is 40:60 or 50:

50. S4. The composite melt stream is cooled by side blowing from one side of the circular hole, and the cooled composite melt stream is oiled, stretched, networked and wound to obtain cationic dyeable high elastic hollow fiber.

2. The method according to claim 1, characterized in that, Step S1 specifically includes: The purified terephthalic acid, ethylene glycol, and 1,4-cyclohexanediol are mixed to form a slurry. A catalyst and a stabilizer are added to the slurry, and an esterification reaction is carried out under pressure at 250°C to 260°C. The molar ratio of the purified terephthalic acid to ethylene glycol is 1:1.2 to 1:2.0, and the pressure conditions are atmospheric pressure to 0.3 MPa. When the amount of distilled water reaches more than 90% of the theoretical value, add the sodium isophthalic acid-5-sulfonate to the reaction system and maintain stirring for 25 to 30 minutes. The pressure was then reduced to below 500 Pa absolute pressure, and the first stage of polycondensation reaction was carried out at 260°C to 270°C for 30 to 50 minutes. The pressure is further reduced to below 100 Pa absolute pressure, while the temperature is raised to 275°C to 285°C to carry out the second stage of polycondensation reaction for 50 to 90 minutes, thereby obtaining modified polyethylene terephthalate melt.

3. The method according to claim 2, characterized in that, The catalyst is any one of antimony trioxide, antimony glycolate, or antimony acetate, and the amount of catalyst added is 0.01%-0.05% of the mass of the purified terephthalic acid.

4. The method according to claim 3, characterized in that, The stabilizer is any one of triphenyl phosphate, trimethyl phosphate, or trimethyl phosphite, and the amount of stabilizer added is 0.01%-0.05% of the mass of the purified terephthalic acid.

5. The method according to claim 4, characterized in that, The opening width of the C-shaped hole is 0.15-0.25mm, the outer diameter is 0.45-0.5mm, and the inner diameter is 0.3-0.35mm; the diameter of the round hole is 0.25-0.3mm, and the shortest distance between the round hole and the C-shaped hole is 0.07-0.08mm.

6. The method according to claim 5, characterized in that, The height of the windless zone of the spinneret is 50-70mm.

7. The method according to claim 6, characterized in that, In step S4, the pressure of the side-blowing air is 50-60 Pa and the temperature is 25-30 °C.

8. The method according to claim 7, characterized in that, In step S4, The height of the oil rack during the oiling process is 900-1200mm; The stretching process uses two-stage hot rollers for hot stretching, with the temperature of the first hot roller being 60-80℃ and the temperature of the second hot roller being 120-140℃, and the stretching ratio being 2-3 times. The spinning speed in the winding process is 2500-2800 m / min.

9. The method according to claim 8, characterized in that, The modified polyethylene terephthalate melt and the unmodified polyethylene terephthalate melt are spun at a temperature of 260-280°C before extrusion, and the initial pressure of the spinneret is 8-12 MPa.

10. A cationic dyeable high-elasticity hollow fiber, characterized in that, The fiber is prepared by any one of claims 1 to 9.

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