Process for preparing island-in-the-sea type sea-island composite polyester fiber

Abstract

The application provides a preparation process of island-determining type sea-island composite polyester fiber, which comprises the following steps: preparation of a color functional composite master batch melt, preparation of a main component melt, preparation of a secondary component melt, double-component composite spinning forming and POY post-processing. The master batch melt has multiple functions and the appearance color and luster of the master batch melt are ensured by compounding different colors and different functional master batches and controlling the compounding ratio. The dyeing post-processing process of the sea-island composite ultrafine fiber fabric is omitted, the environment is protected, different functional effects are given to the sea-island composite ultrafine fiber, and the different functional island-determining type sea-island composite ultrafine fiber fabric produced by the preparation process has the composite functions of elegant color vision, soft hand feeling, bacteriostasis, environmental protection, waterproof, breathable, warm-keeping, super adsorption capacity and the like.

Description

Technical Field

[0001] This invention relates to the field of functional polyester fiber production technology, specifically to a process for preparing island-type sea-island composite polyester fiber. Background Technology

[0002] Island-island composite microfiber is a type of microfiber produced through composite spinning technology. It has advantages such as soft hand feel and good drape, and is widely used in high-end artificial leather, ultra-high density fabrics, and high-performance wiping cloths. Among them, fixed-island composite fiber, due to its fixed number of islands and continuous and uniform distribution of island phases along the fiber length, has stable product quality and has gradually become the mainstream technology route in the island fiber field. With the increasing global awareness of animal protection and increasingly stringent environmental protection requirements, the use of natural leather has been decreasing year by year. Fixed-island microfiber synthetic leather is becoming an important alternative to natural leather, and its demand continues to grow in the fields of footwear, automotive interiors, bags, and furniture.

[0003] However, existing island-type composite microfibers still face many technical challenges in their production. First, there are significant shortcomings in color imparting. Currently, the vast majority of microfibers produced using the island-type method are white, requiring downstream customers to add a dyeing process to obtain the desired color. This post-dyeing process not only increases production costs but also results in poor color fastness, particularly in abrasion and wash fastness. Second, the products have limited functionality. Most existing island-type composite microfiber products only address the issue of ultrafineness, lacking additional functions such as flame retardancy, antibacterial properties, and antistatic properties. While some functional island fibers achieve functionality through finishing processes, these methods suffer from significant drawbacks such as high pollution and poor functional durability. Third, the production equipment is complex, and spinning is difficult. When colorants and multiple functional auxiliaries are introduced simultaneously in the traditional island-type spinning process, the melt rheology changes significantly. Fluctuations in the amount of functional components added directly affect spinning stability, easily causing problems such as breakage, fuzz, and uneven component distribution. In view of this, the applicant proposes a process for preparing island-type sea-island composite polyester fibers to improve the above-mentioned problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a process for preparing island-type sea-island composite polyester fibers, aiming to solve the issues of insufficient color impartation, limited product functionality, complex production equipment, and high spinning difficulty in the preparation of existing island-type sea-island composite microfibers.

[0005] This invention provides a process for preparing island-type sea-island composite polyester fibers, comprising the following steps:

[0006] S1. Preparation of colored functional composite masterbatch melt: The composite masterbatch containing different color components and different functional components is sent to the drying tower to dry and remove water, thereby reducing the moisture content of the composite masterbatch. The dried composite masterbatch is then extruded and melted in the first screw extruder to form colored functional composite masterbatch melt, which is then metered and delivered by the injection pump and enters the melt distribution pipeline through the injection valve.

[0007] S2. Preparation of main component melt: The polyester PET melt is pressurized and transported by a booster pump and cooled by a melt cooler. It then enters the melt distribution pipe through the melt valve and is mixed evenly with the colored functional composite masterbatch melt in the dynamic mixer. Finally, it enters the main box to form the main component melt.

[0008] S3. Preparation of subcomponent melt: COPET alkali sheets are fed into a double crystallization drying tower to remove moisture, and then fed into the second screw extruder to be extruded and melted to form a melt. After being filtered to remove impurities, the melt enters the sub-box to form subcomponent melt.

[0009] S4. Two-component composite spinning: The main component melt in the main chamber is metered by the main metering pump and enters the main cavity of the distribution plate of the composite spinning assembly. The secondary component melt in the secondary chamber is metered by the secondary metering pump and enters the secondary cavity of the distribution plate of the composite spinning assembly. The two component melts are guided by five distribution plates and then extruded in the spinneret holes to form a melt stream. The melt stream is cooled and solidified in the ring blower to form a nascent filament. After being oiled by the oil nozzle, the nascent filament enters the network device to homogenize the oil agent. After the tension is adjusted by the guide plate, it is wound in the winding head to form a colored functional island-type composite polyester fiber POY.

[0010] S5. Post-processing of POY: The colored functional island-type composite polyester fiber POY is stretched and deformed by the texturing machine's first roller, upper heating box, cooling plate, false twister, and second roller. It is then combined with another component, high-shrinkage FDY, which has passed through the zero roller and guide into the second roller and enters the lower heating box for shaping. After that, it is wound and formed in the winding roller by passing through the texturing machine's network device, third roller, and upper oil roller to produce the colored functional island-type composite polyester DTY.

[0011] Preferably, the composite masterbatch in step S1 has a viscosity of 0.3-0.4 dL / g and a melting point of 230-240℃. The composite masterbatch comprises, by mass percentage, 50% carrier resin polypropylene (PP), 10% dispersant, 25%-30% organic pigment, and 10%-15% functional additives. The drying time of the composite masterbatch is 10-12 hours, the drying temperature is 120-130℃, and the addition ratio of the composite masterbatch is 10%-15%.

[0012] Preferably, the composite masterbatch is dried by crystallization followed by drying, wherein the composite masterbatch is first crystallized in the upper part of the drying tower and then enters the drying tower for drying.

[0013] The temperature distribution of the first screw extruder is a gradient cooling setting of 270-290℃ in the front section and 265-275℃ in the rear section;

[0014] The injection pump has two heating zones, with the first zone having a temperature of 280-290℃ and the second zone having a temperature of 285-295℃.

[0015] Preferably, the viscosity of the polyester PET melt in step S2 is 0.610-0.615 dL / g, the outlet melt temperature of the melt cooler is 270-273℃, and the rotation speed of the dynamic mixer is 45-50 rpm.

[0016] Preferably, the viscosity of the COPET alkali sheet in step S3 is 0.58-0.59 dL / g, the crystallization temperature is 140-150℃, the drying temperature is 100-120℃, and the drying time is 20-30 hours;

[0017] The screw in the second screw extruder is a bimetallic screw, and the temperature is set to 250-265℃.

[0018] The filter element has a filter accuracy of 15μm.

[0019] Preferably, in step S4, the temperature of the main housing is 280-290°C, and the temperature of the auxiliary housing is 260-270°C. The temperatures of the main housing and the auxiliary housing are adjusted according to the viscosity difference between the main component melt and the auxiliary component melt to make their flow viscosities similar.

[0020] Preferably, the composite spinning assembly in step S4 consists of five distribution plates and one spinneret. The fifth distribution plate has 24-36 holes, each hole having 37 needle-shaped tubes. The main component melt and the secondary component melt pass through the main cavity and secondary cavity of the first to fourth distribution plates, respectively. The main component colored functional PET melt coming out of the main cavity of the fourth distribution plate flows through the needle-shaped tubes in the fifth distribution plate. The secondary component COPET melt coming out of the secondary cavity of the fourth distribution plate flows around the needle-shaped tubes of the fifth distribution plate, forming a sea-island structure where COPET surrounds and divides PET. The main component melt and the secondary component melt are compoundly extruded in the holes of the sixth spinneret to form a composite ultrafine fiber with a fixed island structure.

[0021] Preferably, in step S4, the ratio of the discharge volume of the main metering pump to that of the auxiliary metering pump is between 4:1 and 5:1, and the switches of the auxiliary metering pump and the main metering pump are interlocked.

[0022] Preferably, in step S4, the pressure of the main component of the composite spinning assembly is 130-170 bar, and the initial pressure of the sub-component assembly is 80-150 bar.

[0023] Preferably, in step S5, the speed of the first roller of the texturing machine is 350-370 m / min, the speed of the second roller is 600-650 m / min, the processing draw ratio of the colored functional island-type composite polyester fiber POY is 1.7-1.8 times, and the high-shrinkage FDY is 20D-30D / 24F-48F grade with a boiling water shrinkage rate of 40%-50%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention combines masterbatches of different colors and functions, controlling their compounding ratio to ensure both the appearance and color of the masterbatch melt and its functional diversity. It eliminates the need for post-dyeing processing of island-island composite microfiber fabrics, offering environmental benefits while imparting different functional effects to the island-island composite microfiber. It also reduces the viscosity difference between the main and secondary component melts by precisely controlling the conveying temperature, screw temperature, and chamber temperature of the main and secondary component melts, minimizing viscosity drop and improving spinning stability. Furthermore, it employs low-temperature, long-term drying of COPET alkali sheets to achieve a moisture content below 20 PPM, reducing the number of strands and yarn breaks during spinning. By controlling the number of needle tubes in the composite component needle plate and positioning the concentricity of the needle tubes, guide holes, and spinnerets, island-shaped composite microfibers with clear and stable island phase structures are obtained. By controlling the ratio of COPET sub-component melt to PET main component melt, controlling the start-up sequence of the spinning metering pump, and interlocking the switching of the main and sub-component melt metering pumps, the number of island cross-section anomalies is significantly reduced. By adjusting the metal sand filtration accuracy of the composite component, the initial pressure of the main and sub-component melt components is reduced, extending the component cycle by up to 15 days and reducing production costs. By controlling the addition ratio of colored functional masterbatch, the internal island phase structure of the fiber is improved, and the fiber opening rate of the subsequent fiber fabrication process is increased.

[0026] The island-type composite microfiber fabrics with different functions produced by the preparation process of this invention have a variety of composite functions such as elegant color visuals, soft hand feel, antibacterial and environmental protection, waterproof, breathable and warm, and super adsorption capacity. They are suitable for high-end imitation suede, artificial leather, high-end automotive interiors, filter materials, and cleaning materials. The products have high added value and have broad market prospects and good economic benefits. Attached Figure Description

[0027] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the invention and, together with the specification, further serve to explain the principles of the invention and enable those skilled in the art to practice and use the invention.

[0028] Figure 1 Flowchart of the process for producing colored functional island-type composite polyester POY fibers;

[0029] Figure 2 Process flow diagram for colored functional island-type composite polyester DTY fiber;

[0030] Figure 3 This is a schematic diagram of the structure of the first distribution plate in the composite spinning assembly.

[0031] Figure 4 This is a schematic diagram of the second distribution plate in the composite spinning assembly.

[0032] Figure 5 This is a schematic diagram of the third distribution plate in a composite spinning assembly.

[0033] Figure 6 This is a schematic diagram of the fourth distribution plate in the composite spinning assembly.

[0034] Figure 7 This is a schematic diagram of the fifth distribution plate in the composite spinning assembly.

[0035] Figure 8 This is a schematic diagram of the sixth spinneret in a composite spinning assembly.

[0036] [Figure Labels]

[0037] 1. COPET alkali flakes; 2. Double crystallization drying tower; 3. Second screw extruder; 4. Filter; 5. Composite masterbatch; 6. Drying tower; 7. First screw extruder; 8. Injection pump; 9. Injection valve; 10. Polyester PET melt; 11. Booster pump; 12. Melt cooler; 13. Melt valve; 14. Melt distribution pipe; 15. Dynamic mixer; 16. Secondary housing; 17. Main housing; 18. Composite spinning assembly; 19. Ring blower; 20. Oil nozzle; 21. Networker; 22. Guide spool; 23. Winding head; 24. First roller; 25. Upper heating box; 26. Cooling plate; 27. False twister; 28. Second roller; 29. ​​Zero roller; 30. Guide spool; 31. Lower heating box; 32. Texturing machine networker; 33. Third roller; 34. Upper oil roller; 35. Winding roller.

[0038] As shown in the figure, specific structures and devices are marked in the figure to clearly illustrate the structure of the embodiments of the present invention. However, this is only for illustrative purposes and is not intended to limit the present invention to this specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Example: Please refer to Figures 1-2 This embodiment provides a process for preparing island-type sea-island composite polyester fiber, including the following steps:

[0041] S1. Preparation of Colored Functional Composite Masterbatch Melt: Composite masterbatch 5, containing different color components and different functional components, is fed into drying tower 6 to remove water and reduce the moisture content of the composite masterbatch. The dried composite masterbatch 5 is then fed into the first screw extruder 7 for extrusion and melting to form colored functional composite masterbatch melt. It is then metered and delivered by injection pump 8 and enters melt distribution pipe 14 through injection valve 9. The functional components in the composite masterbatch 5, which contain different color components and different functional components, include, but are not limited to, organic pigments, antibacterial agents, antistatic agents, and light stabilizers. The drying treatment of composite masterbatch 5 in step S1 is a key step, the purpose of which is to reduce the moisture content of the masterbatch and avoid melt bubbles and fiber defects caused by moisture vaporization during subsequent melt extrusion.

[0042] S2. Preparation of the main component melt: The polyester PET melt 10 is pressurized and transported by the booster pump 11 and cooled by the melt cooler 12 to form a semi-glossy PET melt. This melt then enters the melt distribution pipe 14 through the melt valve 13, where it is mixed evenly with the colored functional composite masterbatch melt in the dynamic mixer 15. Finally, it enters the main housing 17 to form the main component melt. In step S2, the dynamic mixer 15 ensures that the colored functional composite masterbatch melt and the semi-glossy PET melt are thoroughly mixed evenly, guaranteeing a uniform distribution of color and functional components within the main component melt.

[0043] S3. Preparation of Sub-component Melt: COPET alkali sheet 1 is fed into a double crystallization drying tower 2 to remove moisture, and then fed into a second screw extruder 3 for extrusion and melting to form a melt. After being filtered through a filter 4 to remove impurities, it enters the sub-box 16 to form the sub-component melt. COPET alkali sheet 1 is an alkali-soluble copolyester chip. In step S3, COPET alkali sheet 1 serves as the sea component, which can be removed by alkali dissolution in the subsequent fiber opening process, leaving the island component to form ultrafine fibers.

[0044] S4. Two-component composite spinning: The main component melt in the main housing 17 is metered by the main metering pump and enters the main cavity of the distribution plate of the composite spinning assembly 18. The secondary component melt in the secondary housing 16 is metered by the secondary metering pump and enters the secondary cavity of the distribution plate of the composite spinning assembly 18. The two component melts are guided by five distribution plates and then extruded in the spinneret holes to form a melt stream. The melt stream is cooled and solidified in the ring blower 19 to form a nascent filament. The nascent filament is oiled by the oil nozzle 20 and then enters the networker 21 to homogenize the oil. After the tension is adjusted by the guide disc 22, it is wound in the winding head 23 to form a colored functional island-type composite polyester fiber (POY). In step S4, the composite spinning assembly 18 is the core component for realizing the island structure. Through the guidance and distribution of the distribution plates, the main component melt (island phase) and the secondary component melt (sea phase) form a specific cross-sectional structure in the spinneret holes.

[0045] S5. Post-processing of POY: The colored functional island-type composite polyester fiber POY undergoes stretching and deformation through the texturing machine's first roller 24, upper heating box 25, cooling plate 26, false twister 27, and second roller 28. It is then combined with another component, high-shrinkage FDY, which has passed through the zero roller 29 and guide 30 into the second roller 28. After setting in the lower heating box 31, it passes through the texturing machine's mesher 32, third roller 33, and upper oil roller 34 before being wound in the winding roller 35 to produce the colored functional island-type composite polyester DTY. In step S5, the high-shrinkage FDY and POY are combined and set in the heating box. The shrinkage of the high-shrinkage FDY causes the composite yarn to form a three-dimensional curl, giving the product a unique feel and appearance.

[0046] By adopting the above technical solution, coloring and function are integrated by mixing the colored functional composite masterbatch 5 with PET semi-glossy melt in the dynamic mixer 15, eliminating the need for the downstream fabric dyeing process. This has significant environmental benefits and cost advantages. Through the bicomponent composite spinning of the main and secondary component melts, an island-type island structure is formed, laying the foundation for subsequent fiber opening to obtain ultrafine fibers. The entire process is coherent and controllable, making it suitable for large-scale production.

[0047] In this embodiment, the viscosity of the composite masterbatch 5 is 0.3-0.4 dL / g and the melting point is 230-240℃. This viscosity range is lower than that of the semi-glossy PET melt (0.610-0.615 dL / g), which is beneficial for thorough mixing with the PET melt in the dynamic mixer 15. By controlling the viscosity and melting point range of the composite masterbatch 5, it can be made to have good miscibility with the PET melt.

[0048] In this embodiment, the composite masterbatch 5 comprises, by mass percentage, 50% carrier resin (polypropylene PP), 10% dispersant, 25%-30% organic pigment, and 10%-15% functional additives. The carrier resin (polypropylene PP) serves to support and disperse the components. The dispersant helps the organic pigment and functional additives to disperse evenly in the carrier resin. The organic pigment provides the color required by the fiber and can be selected from carbon black, titanium dioxide, organic red, organic blue, etc. The functional additives include, but are not limited to, antibacterial agents such as silver-based antibacterial agents, zinc-based antibacterial agents, antistatic agents, cooling agents such as menthol compounds, and light stabilizers. Through a reasonable masterbatch composition ratio, a synergistic effect of color and function is achieved.

[0049] In this embodiment, the drying time of composite masterbatch 5 is 10-12 hours and the drying temperature is 120-130℃, which can reduce the moisture content of composite masterbatch to below 20ppm.

[0050] In this embodiment, the composite masterbatch 5 is dried by crystallization followed by drying. The composite masterbatch 5 crystallizes first in the upper part of the drying tower 6 and then enters the drying tower 6 for drying. The crystallization followed by drying method is achieved by the baffle valve at the upper part of the drying tower 6. The composite masterbatch 5 enters the upper 1 / 3 of the drying tower 6 and completes the crystallization process above the baffle valve to prevent the masterbatch particles from sticking together and clumping at high temperature. After crystallization is completed, the baffle valve is opened to allow the masterbatch to fall into the lower part of the drying tower 6 for drying. This method effectively solves the problem of composite masterbatches of different colors and functions easily clumping and sticking together in the drying tower, ensuring the drying quality of the masterbatch and the stability of subsequent spinning.

[0051] In this embodiment, the addition ratio of composite masterbatch 5 is 10%-15%, meaning that composite masterbatch 5 accounts for 10%-15% of the total mass of the main component melt. A high proportion of colored functional composite masterbatch can increase the visual impact of the fiber's appearance, while significantly enhancing the comprehensive functions of the fiber fabric, such as antibacterial properties, cooling sensation, and antistatic properties. However, if the addition ratio is too high, the component pressure will rise rapidly during composite spinning, leading to increased filament drift and a higher breakage rate. Therefore, it needs to be controlled within a reasonable range of 10%-15% to ensure the fiber's appearance, color, and functionality while avoiding spinning instability caused by an excessively high addition ratio. In one specific embodiment, the addition ratio of composite masterbatch 5 is 13%.

[0052] In this embodiment, the temperature distribution of the first screw extruder 7 is a gradient cooling setting of 270-290℃ in the front section and 265-275℃ in the rear section. The screw extruder adopts a gradient cooling setting of high temperature in the front section and low temperature in the rear section, for example, the temperature distribution is 280℃ / 275℃ / 270℃ / 270℃ / 270℃. Since the viscosity and melting point of the color functional composite masterbatch 5 are lower than those of PET, the composite masterbatch 5 has already melted in the first and second zones of the screw, and the latter three zones maintain a lower temperature, which can prevent the mechanical friction heating of the screw from heating too quickly, resulting in excessive thermal degradation of the melt viscosity.

[0053] In this embodiment, the injection pump 8 is equipped with two heating zones. The temperature of the first zone is 280-290℃, and the temperature of the second zone is 285-295℃. The setting of two heating zones is more uniform than heating with a single zone. This can prevent blockage caused by uneven heating when different functional masterbatches melt and pass through the injection pump 8. Through the gradient cooling setting of the first screw extruder 7 and the dual-zone heating design of the injection pump 8, the thermal degradation of the melt and the blockage of the injection pump are effectively prevented, ensuring the continuous stability of the spinning process.

[0054] In this embodiment, the viscosity of the polyester PET melt 10 in step S2 is 0.610-0.615 dL / g. This viscosity range is lower than that of conventional PET melt (usually 0.640-0.650 dL / g). The purpose is to reduce the viscosity difference between the semi-glossy main melt and the colored functional composite masterbatch melt (viscosity 0.3-0.4 dL / g), thereby improving the mixing uniformity of the two in the dynamic mixer.

[0055] In this embodiment, the outlet melt temperature of the melt cooler 12 is 270-273°C, which is lower than the conventional 275-280°C. Lowering the melt temperature can reduce the thermal degradation of the melt during the transportation process and maintain the stability of the melt viscosity. By reducing the PET melt viscosity and the outlet temperature of the melt cooler 12, the thermal degradation during the melt transportation process is reduced, making the viscosity of the semi-glossy main melt and the color functional composite masterbatch melt closer.

[0056] In this embodiment, the rotation speed of the dynamic mixer 15 is 45-50 rpm, which is higher than the conventional 30-40 rpm. The higher rotation speed means a stronger shear mixing effect, which makes the distribution of color and functional components in the main component melt more uniform. By increasing the rotation speed of the dynamic mixer 15, the mixing effect is enhanced, ensuring the uniform distribution of color and functional components in the main component melt, which provides a guarantee for obtaining fibers with uniform color and function in subsequent spinning.

[0057] In this embodiment, COPET alkali sheet 1 is used as a marine component, and its quality directly affects the spinning stability and subsequent fiber opening effect. The viscosity of COPET alkali sheet 1 is 0.58-0.59 dL / g, and the crystallization temperature is 140-150℃, which allows COPET alkali sheet 1 to fully crystallize and prevents sticking during subsequent drying. The drying temperature is 100-120℃, which is lower than the conventional 130-140℃. The drying time is 20-30 hours, which is significantly longer than the conventional 12-15 hours. This low-temperature long-time drying strategy can reduce the moisture content of COPET alkali sheet to less than 20ppm, and in one specific embodiment, it can reach 15ppm, effectively reducing the phenomenon of yarn breakage and filament drift during the spinning process.

[0058] In this embodiment, the screw in the second screw extruder 3 is a bimetallic screw, which has better wear resistance and corrosion resistance than ordinary screws. The temperature is set to 250-265℃, for example, a gradient temperature setting of 250℃ / 255℃ / 260℃ / 260℃ / 265℃, which reduces the melting temperature of each zone of the screw and avoids excessive thermal degradation of COPET.

[0059] In this embodiment, the filter element of filter 4 has a filter precision of 15μm, which effectively filters impurities in the melt, reduces spinning head breakage caused by impurity blockage, and helps to extend the service life of the spinning assembly. By improving the filter element precision, the impact of impurities on the spinning assembly is reduced, and the spinning assembly cycle can be extended to more than 10 days, significantly reducing production costs.

[0060] In this embodiment, the temperature of the main housing 17 is 280-290℃, and the temperature of the auxiliary housing 16 is 260-270℃. The temperatures of the main housing 17 and the auxiliary housing 16 are adjusted according to the viscosity difference between the main component melt and the auxiliary component melt to make their flow viscosities similar. The main housing 17 contains the main component PET melt, and the auxiliary housing 16 contains the auxiliary component COPET melt. The two melts have different chemical compositions and rheological properties, requiring differentiated temperature control to ensure they have similar flow viscosities during composite spinning. The temperature of the main housing 17 is controlled at 280-290℃, specifically 283℃ in one embodiment, and the temperature of the auxiliary housing 16 is controlled at 260-270℃, specifically 265℃ in one embodiment. The temperature of the main housing 17 is higher than that of the auxiliary housing 16 because the melting temperature of the PET melt is higher. For COPET melt, the temperature of the secondary chamber 16 should not be too high to avoid thermal degradation of the COPET melt. By precisely controlling the temperature of the primary and secondary chambers, the difference in flow viscosity between the two component melts during composite spinning is minimized, thereby obtaining a bicomponent melt with consistent flowability, ensuring the uniformity and stability of the island structure. Through differentiated temperature control of the primary and secondary chambers, the primary and secondary component melts have similar flow viscosities during composite spinning, reducing uneven component distribution and abnormal island structure caused by viscosity differences, and improving the stability of the spinning process and the consistency of product quality.

[0061] In this embodiment, as Figures 3-8As shown, the composite spinning assembly 18 consists of five distribution plates and one spinneret. The fifth distribution plate has 24-36 holes, each with 37 needle-shaped tubes. The main component melt and the secondary component melt pass through the main cavity and secondary cavity of the first to fourth distribution plates, respectively. The main component colored functional PET melt coming out of the main cavity of the fourth distribution plate flows through the needle-shaped tubes in the fifth distribution plate. The secondary component COPET melt coming out of the secondary cavity of the fourth distribution plate flows around the needle-shaped tubes of the fifth distribution plate, forming a sea-island structure where COPET surrounds and divides PET. The main component melt and the secondary component melt are extruded together in the holes of the sixth spinneret to form a composite ultrafine fiber with a fixed island structure. The composite spinning assembly 18 is the core component for realizing the fixed island structure. The composite spinning assembly 18 consists of five distribution plates and one spinneret stacked sequentially. The main and secondary component melts enter the main and secondary cavities of the distribution plates, respectively. After being guided and distributed by the first four distribution plates, the final cross-sectional structure is formed at the fifth distribution plate. The fifth distribution plate is a key design element: it has 24-36 holes, specifically 24 holes in one embodiment, with 37 needle-like tubes in each hole. The main component, colored functional PET melt, flows out from the main cavity of the fourth distribution plate and then flows through the fifth distribution plate. Thirty-seven needle-shaped tubes are used. After the secondary component COPET melt flows out from the secondary cavity of the fourth distribution plate, it flows through the space around the needle-shaped tubes of the fifth distribution plate. The arrangement of the needle-shaped tubes divides the main component melt into multiple fine streams. Each stream is surrounded by the secondary component COPET melt, forming a typical island-enclosed structure. Subsequently, the main and secondary component melts are extruded together in the holes of the sixth spinneret to form a composite ultrafine fiber with a fixed island cross-section structure. The concentricity positioning of the needle-shaped tubes, guide holes, and spinneret holes is the key to ensuring the uniformity of the fixed island structure. Concentricity deviation will lead to uneven distribution of island phases and affect the subsequent fiber opening effect.

[0062] In this embodiment, the ratio of the discharge volume of the main metering pump to that of the auxiliary metering pump is between 4:1 and 5:1. The auxiliary metering pump and the main metering pump are interlocked. The auxiliary metering pump is set to a high-speed-normal switching mode, with the initial speed of the auxiliary metering pump increased to three times the process speed and automatically reduced to the process speed within 10 seconds. The discharge volume ratio of the main metering pump and the auxiliary metering pump directly determines the ratio of island phase to marine phase in the island structure. The mass ratio of the discharge volume of the main metering pump to that of the auxiliary metering pump is controlled between 4:1 and 5:1. In a specific embodiment, it is 80%:20% (i.e., 4:1). Controlling the melt ratio of the main and auxiliary components within a certain range can make the obtained island phase fixed and clear, reduce the probability of island adhesion, missing islands, and reverse islands in the fiber cross-section, and increase the fiber opening rate in subsequent processes of the fiber fabric. By interlocking the main and auxiliary metering pumps, the spinning assembly is initially empty when the spinning assembly is replaced or started. It needs to be filled with melt before normal spinning can begin. Due to the long transport path of the COPET melt, if the main and auxiliary metering pumps start simultaneously, the COPET melt will reach the spinneret later than the PET melt, leading to problems such as island-to-island adhesion and unclear island structure in the initial spinning process. By setting the auxiliary metering pump to a high-speed-normal switching mode, the auxiliary metering pump speed is increased to three times the process speed at startup, allowing the assembly to be quickly filled with COPET melt. The auxiliary pump speed automatically decreases to the process speed within 10 seconds, achieving the effect of extruding the main PET melt from the spinneret simultaneously. This reduces island-to-island adhesion, results in a clear island structure, significantly reduces the number of island cross-section anomalies, and improves the product yield.

[0063] In this embodiment, the pressure of the main component of the composite spinning assembly 18 is 130-170 bar, and the initial pressure of the secondary component is 80-150 bar. The pressure of the composite spinning assembly is a crucial parameter affecting spinning stability and the assembly's service life. The pressure of the main component assembly is controlled within the range of 130-170 bar, with 140 bar in one specific embodiment. The initial pressure of the sub-component assembly is controlled within the range of 80-150 bar, with 85 bar in one specific embodiment. By adjusting the metal sand filtration precision of the composite assembly, the initial pressure of the main and sub-component melt assemblies is reduced, thus slowing down the assembly's pressure rise rate. In traditional processes, due to the high impurity content of the sub-component COPET melt, the initial pressure of the assembly is usually above 120 bar, resulting in a rapid pressure rise rate and a service life of only 5-6 days. This application, by optimizing the filtration precision and melt quality, reduces the initial pressure of the sub-component assembly to below 100 bar, significantly slowing down the assembly's pressure rise rate and extending the service life from 5 days to 15 days. This extended service life can significantly reduce production energy consumption and assembly replacement frequency for producing island-type microfibers with different colors and composite functions, thereby improving product quality consistency.

[0064] In this embodiment, the speed of roller 24 of the texturing machine is 350-370 m / min, and the speed of roller 28 is 600-650 m / min. The draw ratio of the colored functional island-type composite polyester fiber POY is 1.7-1.8 times. The POY is fed into the upper heating box 25 for heating through roller 24 of the texturing machine, then cooled by the cooling plate 26, twisted by the false twister 27, and output through roller 28 to complete the stretching deformation process. The speed of roller 24 is controlled at 350-370 m / min, and in one specific embodiment, it is 360 m / min. The speed of roller 28 is controlled at 600-650 m / min, and in one specific embodiment, it is 630 m / min. The draw ratio (i.e., the ratio of the speed of the second roller at 28 to the speed of the first roller at 24) is controlled between 1.7 and 1.8 times, and in one specific implementation it is 1.75 times. Increasing the draw ratio can increase the processing tension, which facilitates the subsequent twisting operation with high shrinkage FDY, making the composite yarn less prone to separation and the yarn path stable.

[0065] In this embodiment, the high-shrinkage FDY is of 20D-30D / 24F-48F grade, with a boiling water shrinkage rate of 40%-50%. In a specific embodiment, it is of 30D / 24F grade, with a boiling water shrinkage rate of 42%. The high-shrinkage FDY passes through the zero roller 29 and the guide yarn 30 into the second roller 28, where it is twisted with POY. Then, they enter the lower heating box 31 together for setting. During the heat setting process, the high-shrinkage FDY shrinks, causing the composite yarn to form a three-dimensional curl, giving the product a unique feel and appearance. After setting, the yarn passes through the texturing machine networker 32, the third roller 33, and the upper oil roller 34, and is finally wound into shape in the winding roller 35 to obtain a colored functional island-type composite polyester fiber DTY product. By selecting high-shrinkage FDY of appropriate specifications and shrinkage rates for use, the final product has a unique feel, appearance, and excellent physical properties.

[0066] In a preferred embodiment of this invention, the colored functional island-type sea-island composite polyester fiber obtained through the above-described preparation process has a cross-sectional structure of island-type sea-island structure. The island phases are fixed, clear, and uniformly distributed. The fiber possesses both a colored appearance and functional properties. Functional types include, but are not limited to, extra black, iridescent, antibacterial, and cooling properties. After the fiber fabric undergoes a fiber-opening treatment, the sea-island component (COPET) is removed by alkali dissolution, and the island components form ultrafine fibers. The fabric has advantages such as a soft hand feel, good drape, and strong adsorption capacity. The fiber fabric produced by the process of this invention can control the cross-sectional anomaly rate to below 0.6%, the fiber-opening rate to above 99.5%, and the product quality rate to 98.5%-99.3%. The obtained colored functional island-type sea-island composite polyester fiber combines a colored appearance with multiple functional properties, eliminating the need for downstream fabric dyeing processes, thus offering environmental benefits and cost advantages. The fiber's island phase structure is stable and clear, with a high fiber-opening rate and controllable product quality, indicating broad market prospects and good economic benefits.

[0067] In summary, the present invention provides a process for preparing island-type composite polyester fibers. By combining different colors with masterbatches of different functions, coloring and functionality are integrated. By precisely controlling the viscosity difference and temperature parameters of the main and secondary component melts, spinning stability is improved. Low-temperature long-term drying of COPET alkali-soluble chips reduces moisture content and yarn breakage. By optimizing the composite component structure and metering pump interlocking control, a clear and stable island-type island structure is obtained. By adjusting the filtration precision, the initial pressure of the component is reduced, extending the component's service life. The produced island-type composite microfiber fabrics with different functions have elegant color visuals, soft hand feel, antibacterial and environmentally friendly properties, waterproof, breathable and warm properties, and super adsorption capacity, making them suitable for high-end imitation suede, artificial leather, high-end automotive interiors, filter materials, and cleaning materials.

[0068] All technical features in this embodiment can be freely combined according to actual needs.

[0069] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

Claims

1. A process for preparing island-type sea-island composite polyester fiber, characterized in that, Includes the following steps: S1. Preparation of colored functional composite masterbatch melt: The composite masterbatch (5) containing different color components and different functional components is sent to the drying tower (6) to dry and remove water, thereby reducing the moisture content of the composite masterbatch. The dried composite masterbatch (5) is then extruded and melted in the first screw extruder (7) to form colored functional composite masterbatch melt. It is then metered and transported by the injection pump (8) and enters the melt distribution pipeline (14) through the injection valve (9). S2. Preparation of main component melt: The polyester PET melt (10) is pressurized and transported by the booster pump (11) and cooled by the melt cooler (12). Then, it enters the melt distribution pipe (14) through the melt valve (13) and enters the dynamic mixer (15) together with the colored functional composite masterbatch melt to mix evenly. Then, it enters the main box (17) to form the main component melt. S3. Preparation of subcomponent melt: COPET alkali sheet (1) is sent into a double crystallization drying tower (2) to remove moisture, and then sent into a second screw extruder (3) to be extruded and melted to form a melt. After being filtered by a filter (4) to remove impurities, it enters the sub-box (16) to form subcomponent melt. S4, Bicomponent Composite Spinning: The main component melt in the main box (17) is metered by the main metering pump and enters the main cavity of the distribution plate of the composite spinning assembly (18). The secondary component melt in the secondary box (16) is metered by the secondary metering pump and enters the secondary cavity of the distribution plate of the composite spinning assembly (18). The two component melts are respectively guided by five distribution plates and then extruded in the spinneret holes to form a melt stream. The melt stream is cooled and solidified in the ring blower (19) to form a nascent filament. After the nascent filament is oiled by the oil nozzle (20), it enters the networker (21) to homogenize the oil agent. After the tension is adjusted by the guide disc (22), it is wound in the winding head (23) to form a colored functional island-type composite polyester fiber POY. S5. Post-processing of POY: The colored functional island-type composite polyester fiber POY is stretched and deformed by the texturing machine first roller (24), upper heating box (25), cooling plate (26), false twister (27), and second roller (28). It is then combined with another component, high shrinkage FDY, which enters the second roller (28) through the zero roller (29) and guide (30) and enters the lower heating box (31) to complete the shaping. After that, it passes through the texturing machine networker (32), third roller (33), and upper oil roller (34) and is wound in the winding roller (35) to prepare colored functional island-type composite polyester DTY.

2. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, The composite masterbatch (5) in step S1 has a viscosity of 0.3-0.4 dL / g and a melting point of 230-240℃. The composite masterbatch (5) includes, by mass percentage, 50% carrier resin polypropylene (PP), 10% dispersant, 25%-30% organic pigment, and 10%-15% functional additives. The drying time of the composite masterbatch (5) is 10-12 hours and the drying temperature is 120-130℃. The addition ratio of the composite masterbatch (5) is 10%-15%.

3. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, The composite masterbatch (5) is dried by crystallization followed by drying. The composite masterbatch (5) is first crystallized in the upper part of the drying tower (6) and then dried in the drying tower (6). The temperature distribution of the first screw extruder (7) is a gradient cooling setting of 270-290℃ in the front section and 265-275℃ in the rear section; The injection pump (8) is equipped with two heating zones, with the temperature of zone one being 280-290℃ and the temperature of zone two being 285-295℃.

4. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, The viscosity of the polyester PET melt (10) in step S2 is 0.610-0.615 dL / g, the outlet melt temperature of the melt cooler (12) is 270-273℃, and the rotation speed of the dynamic mixer (15) is 45-50 rpm.

5. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, The viscosity of the COPET alkaline sheet (1) mentioned in step S3 is 0.58-0.59 dL / g, the crystallization temperature is 140-150℃, the drying temperature is 100-120℃, and the drying time is 20-30 hours; The screw in the second screw extruder (3) is a bimetallic screw, and the temperature is set to 250-265℃; The filter element of the filter (4) has a filter element precision of 15μm.

6. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, In step S4, the temperature of the main box (17) is 280-290℃, and the temperature of the auxiliary box (16) is 260-270℃. The temperatures of the main box (17) and the auxiliary box (16) are adjusted according to the viscosity difference between the main component melt and the auxiliary component melt so that their flow viscosities are close.

7. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, The composite spinning assembly (18) in step S4 consists of five distribution plates and one spinneret. The fifth distribution plate has 24-36 holes, each with 37 needle tubes. The main component melt and the secondary component melt pass through the main cavity and secondary cavity of the first to fourth distribution plates respectively. The main component colored functional PET melt coming out of the main cavity of the fourth distribution plate flows through the needle tubes in the fifth distribution plate. The secondary component COPET melt coming out of the secondary cavity of the fourth distribution plate flows through the periphery of the needle tubes of the fifth distribution plate, forming a sea-island structure of COPET surrounding and dividing PET. The main component melt and the secondary component melt are compositely extruded in the holes of the sixth spinneret to form a composite ultrafine fiber with a fixed island structure.

8. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, In step S4, the ratio of the discharge volume of the main metering pump to that of the auxiliary metering pump is between 4:1 and 5:1, and the auxiliary metering pump and the main metering pump are interlocked.

9. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, In step S4, the pressure of the main component of the composite spinning assembly (18) is 130-170 bar, and the initial pressure of the secondary component is 80-150 bar.

10. The process for preparing island-type sea-island composite polyester fiber according to claim 1, characterized in that, In step S5, the speed of the first roller (24) of the texturing machine is 350-370 m / min, the speed of the second roller (28) is 600-650 m / min, the processing draw ratio of the colored functional island-type composite polyester fiber POY is 1.7-1.8 times, and the high shrinkage FDY is of 20D-30D / 24F-48F grade with a boiling water shrinkage rate of 40%-50%.

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