Multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber and preparation method thereof

Abstract

The application belongs to the technical field of new functional fibers, and discloses a multi-layer composite structure melt spinning and fiber opening coupled superfine fiber and a preparation method thereof, the superfine fiber being obtained after a composite fiber with a periodic and alternating stacked lamellar structure is opened; in the cross-section direction of the composite fiber, a plurality of first polymer layers and a plurality of second polymer layers are alternately arranged; the preparation method comprises the following steps: firstly, two polymer materials which can be melt spun and are incompatible with each other are melt extruded respectively, the melt of each polymer material passes through a confluence module, and then enters a segmentation module and a spinning nozzle module in sequence, and the polymer material is solidified to form a primary fiber after passing through the spinning nozzle module, and finally, the primary fiber is opened to obtain the multi-layer composite structure melt spinning and fiber opening coupled superfine fiber; wherein, the number of the segmentation module is 5-10, and the first and second segmentation partitions in the adjacent two segmentation modules are perpendicular. The application realizes the superfine fiber preparation with controllable fiber fineness, layer structure, continuous production and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of novel functional fiber technology, and relates to a multi-layer composite structure melt spinning and fiber opening coupling ultrafine fiber and its preparation method. Background Technology

[0002] Currently, various technical routes have been developed for the preparation of microfibers, mainly including direct melt spinning, meltblowing, electrospinning, phase separation, solution spinning, and island-island composite spinning. However, these methods all have varying degrees of technical bottlenecks, making it difficult to simultaneously meet the industrialization requirements of "large-scale production, low pollution, high purity, and controllable diameter." Specifically: Direct melt spinning forms fibers by extruding and solidifying polymer melts. While it offers advantages such as high yield and solvent-free operation, it is limited by spinneret size and melt viscosity, making fibers prone to breakage during stretching and resulting in a low yield. Meltblowing is simple and has high yield, but the fiber diameter distribution is wide and the structural controllability is poor. Electrospinning can produce nanoscale fibers, but its yield is low, its continuity is poor, and its equipment maintenance is complex, making industrialization difficult. Phase separation and solution spinning produce fibers with adjustable pore structures, but they present unresolved issues such as solvent recovery and environmental pollution. Island-island composite spinning forms an island structure by co-spinning "island" and "sea" components, and then dissolves and removes the "sea" component to obtain ultrafine fibers. This method can achieve a certain degree of continuous production, but the "sea-island" components must be strictly matched, limiting the selection of raw materials. It also requires the design of complex multi-component spinning spinnerets, and subsequent selective dissolution of the "sea phase" is necessary. The process is cumbersome, costly, and it is difficult to guarantee the uniformity of fiber diameter.

[0003] Reference 1 (Electrospun nanofibers, process, merits, challenges, and usefulness: A review[J]. Journal of Engineered Fibers and Fabrics, 2025, 20.DOI: 10.1177 / 15589250251359274.) summarizes the preparation methods of nanofibers, including single-needle, multi-needle, needle-free, and solution electrospinning. However, it points out that electrospinning still has problems such as difficulty in scaling up production, insufficient product reproducibility, organic solvent toxicity, needle clogging, and unstable fiber mechanical properties.

[0004] Reference 2 (Structure, performance, and technical applications of melt-blown materials: A review[J]. Composites Part B: Engineering, 2026, 321:113705. DOI: 10.1016 / j.compositesb.2026.113705.) reviews the technology for preparing ultrafine meltblown fibers by high-speed hot air stretching of polymer melt, but points out that meltblown materials still have problems such as precise control of fiber microstructure, long-term stability, and difficulties in large-scale manufacturing of multifunctional materials.

[0005] The patent application with publication number CN118653255A uses polyvinyl alcohol as the marine phase and polypropylene as the island phase for island-island bicomponent melt spinning, and then uses water or organic solvent to dissolve and remove the marine phase to obtain a polypropylene ultrafine fiber membrane. However, it requires a special island-island composite spinning assembly and consumes sacrificial marine phase material. Subsequent dissolution, washing and drying treatments are also required.

[0006] The patent application with publication number CN118547385A prepares ultrafine fibers through online polymerization and high-speed hot air meltblowing. However, the fiber forming is affected by melt viscosity, flow rate and hot air conditions, which can easily lead to problems such as uneven diameter distribution and limited fiber length.

[0007] In summary, existing microfiber preparation technologies suffer from numerous problems, including material incompatibility, inability to precisely control the structure, lack of continuous production capability, high cost, and severe environmental pollution, making it difficult to meet the dual demands of high performance and industrialized production. Therefore, there is an urgent need to develop a multi-layered composite structure microfiber coupled with melt spinning and fiber opening, along with its preparation method, to overcome existing technological bottlenecks and achieve efficient, green, and controllable microfiber production. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and to provide a multi-layer composite structure of melt spinning and fiber opening coupled ultrafine fiber and its preparation method.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing multilayer composite structure melt spinning and fiber opening coupled ultrafine fibers involves firstly melting and extruding two incompatible melt-spinning polymer materials separately. The melts of each material pass through a confluence module and then sequentially enter a segmentation module and a spinning module. After passing through the spinning module, the melts solidify to form nascent fibers, i.e., composite fibers with a periodically alternating stacked layered structure. Finally, the nascent fibers are opened to obtain multilayer composite structure melt spinning and fiber opening coupled ultrafine fibers.

[0011] The segmentation module includes a metal body II and two irregularly shaped hollow cavity flow channels II that penetrate the interior of the metal body II. The two irregularly shaped hollow cavity flow channels II are separated by a partition. The two types of melt from the confluence module flow into one irregularly shaped hollow cavity flow channel II respectively. The inlets and outlets of the two irregularly shaped hollow cavity flow channels II are located on the same plane, and the planes containing the inlets and outlets are parallel to each other. The inlets and outlets are rectangles of the same size. The partition includes a first segmentation partition, a second segmentation partition, a first guide partition, a second guide partition, a third guide partition, and a fourth guide partition. The first segmentation partition is perpendicular to the plane containing the inlet, and the second segmentation partition is perpendicular to the plane containing the outlet. The inlet is located on the plane, and the first and second partitions are perpendicular to each other; one irregular hollow cavity flow channel II is formed by the first partition, the first drainage partition, the third drainage partition and the wall of metal body II, and another irregular hollow cavity flow channel II is formed by the second partition, the second drainage partition, the fourth drainage partition and the wall of metal body II; a three-dimensional rectangular coordinate system is constructed with the thickness direction of the first partition as the x-axis, the width direction as the y-axis and the length direction as the z-axis. In the irregular hollow cavity flow channel II, from the inlet to the outlet, the distance in the x-axis direction is constant and the distance in the y-axis direction gradually decreases, and then the distance in the y-axis direction is constant and the distance in the x-axis direction gradually increases;

[0012] The number of segmentation modules is 5 to 10, and the first segmentation partition in each segmentation module is perpendicular to the second segmentation partition in the adjacent segmentation module.

[0013] After passing through the confluence module, the melt enters the segmentation module and the spinneret module, which are assembled according to the "partition cross method". Under the synergistic action of each module, the spinning melt completes the process of "segmentation" - "extrusion" - "stretching" - "stacking" - "setting", forming a composite fiber with a periodically alternating stacked layered structure. In the segmentation module, the two melts that have been "segmented" enter the fluid channel and are "extruded". "Extrusion" is a process in which the fluid channel gradually narrows, and the width of the melt is "extended" to the width of the outlet, while the height is "extended" to the height of the outlet, while the arrangement remains unchanged. The melt after "extrusion" and "stretching" is bound in the channel of the segmentation module. Then the two melts "stacking" along the flow channel. The "stacking" melt then enters a new segmentation module. This process is equivalent to doubling the number of layers. Then the process of "segmentation" - "extrusion" - "stretching" - "stacking" - "setting" is repeated, and finally a multi-layered structure is formed. Then, a mechanical peeling process is used, including winding and stretching, directional friction, and shear disturbance, to separate multi-layered fibers along the interlayer interface, so as to continuously and controllably prepare ultrafine fibers in the range of 0.1~5 μm.

[0014] As a preferred technical solution:

[0015] As described above, in the preparation method of a multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber, the melting temperature difference between the two polymer materials does not exceed 50°C. This range ensures that the two polymers can maintain a stable molten state within the same processing temperature range. If the temperature difference is too large, it is not conducive to the integrity of the interlayer interface. The melt index difference does not exceed 5 g / 10 min. If the difference is too large, it is not conducive to the uniformity of the layer thickness. The melt viscosity ratio is 0.5~1.5. This range ensures the shear force balance of the two melts at the interlayer interface, so as to ensure the flow stability of the melt in the spinning assembly and the integrity of the interlayer interface.

[0016] The method for preparing multilayer composite structure melt spinning and fiber opening coupled ultrafine fibers, as described above, uses polymer materials selected from polypropylene (PP), polyamide (PA), polyester (PET, PBT), polycarbonate (PC), polyethylene (PE), polymethyl methacrylate (PMMA), polystyrene (PS), polyurethane (PU), and their composite systems. By selecting a suitable material system, fiber breaking strength, elongation at break, and layer thickness uniformity can be balanced, enabling the continuous preparation of high-performance ultrafine fibers.

[0017] The method for preparing multilayer composite structure melt spinning and fiber opening coupled ultrafine fibers, as described above, employs two twin-screw extruders for melt extrusion, with extrusion rates of 1-5 kg / h for each. Both twin-screw extruders are divided into a feeding section, a melting section, and an extrusion section, with temperature settings of 90-140℃, 210-270℃, and 230-280℃, respectively. The optimal extrusion temperature is determined by the melting and thermal decomposition temperatures of different polymers. Excessive temperature exceeding the thermal decomposition temperature leads to polymer decomposition, while excessively low temperature increases melt viscosity, reduces fluidity, and causes screw blockage and ring-forming resistance. The melting section temperature must be higher than the polymer's melting temperature to ensure complete plasticization and the formation of a homogeneous melt (e.g., 265-275℃ for PET melting section, 270-280℃ for polyamide 66 melting section). The extrusion section temperature matches the melt conveying requirements and must be lower than the thermal decomposition temperature to inhibit polymer thermal degradation.

[0018] To prevent the melt from cooling too quickly, heating tape and thermocouples are wrapped around the busbar module, splitting module and spinneret module for heating and temperature measurement. The heating temperature is 180~280℃ to maintain the flowability of the interlayer interface and the integrity of the fiber structure.

[0019] The method for preparing ultrafine fibers with a multilayer composite structure coupled by melt spinning and fiber opening, as described above, employs a mechanical peeling process for fiber opening. The mechanical peeling method includes at least one of winding stretching, directional friction, and shear disturbance, to achieve fiber separation along the interlayer interface, resulting in ultrafine fibers with uniform central thickness and complete structure, while maintaining the continuity and uniformity of the layered composite structure, providing a reliable technical guarantee for continuous and high-precision preparation. These three mechanical peeling methods can be used individually or in combination. In the front stage, multilayer co-extrusion and layer multiplication channels are used to construct composite fibers with a periodically alternating layered structure with a dissociable interface. In the back stage, the composite fibers are placed in a continuous and controllable mechanical load field, causing the interface to preferentially initiate and propagate cracking, thereby orderly separating a multilayer composite precursor yarn into multiple ultrafine unit fibers.

[0020] Winding and stretching refers to the process where nascent fibers are sequentially wound around a front drafting roller and a rear drafting roller. The linear velocity of the rear drafting roller is higher than that of the front drafting roller, causing the fibers to be subjected to continuous axial stretching. The drafting ratio is 2 to 3 times, and the winding linear speed is 800 to 1200 m / min. During the stretching process, the two polymers generate interfacial stress due to their different elastic moduli and deformation capabilities. The interlayer interface cracks first and then extends along the fiber axis, thereby causing the composite fiber to separate into ultrafine fibers.

[0021] Directional friction refers to the continuous contact of nascent fibers with the surface of a friction element along their length extension direction at a set wrap angle, causing tangential friction between the fibers and the friction element during operation. The tangential friction and local compression between the fibers and the contact surface promote fiber opening. The friction element can be a friction roller, a ceramic guide, or a surface roughening guide. The number of friction elements is 1 to 3, and the wrap angle of the fiber on a single friction element is 90° to 180°. The friction is mainly applied to the surface and edge of the fiber, causing microcracks to form at the interlayer interface and gradually peeling off.

[0022] Shear disturbance refers to the process by which nascent fibers are subjected to localized shearing, bending, and slight torsion during operation as they pass through a pair of differential rollers or staggered guide rollers. The linear velocity ratio of the differential rollers (the ratio of the linear velocity of the next roller to that of the previous roller) is 1.03 to 1.10, and the guide deflection angle between the staggered guide rollers is 5° to 15°. Shear disturbance causes uneven deformation of the interlayer interface, promotes the further propagation of existing interface cracks, and ultimately achieves the separation of layered composite fibers.

[0023] As described above, in the method for preparing ultrafine fibers with a multi-layer composite structure that is coupled by melt spinning and fiber opening, a busbar module is used to connect two screw extruders, and a splitting module is used to connect the busbar module and the spinneret module. The busbar module, splitting module, and spinneret module are all assembled with bolts and screws.

[0024] The method for preparing a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber as described above includes a busbar module comprising a metal body I and two irregularly shaped hollow cavity flow channels I that penetrate the interior of the metal body I. The inlets of the two irregularly shaped hollow cavity flow channels I are located on different planes, and the outlets are symmetrically arranged on the same plane, and the inlets and any outlets are not on the same plane.

[0025] The inlets of the two irregularly shaped hollow cavity flow channels I are circular and the outlets are rectangular.

[0026] The axis of symmetry between the outlets of the two irregularly shaped hollow cavity flow channels I in the merge module is perpendicular to the axis of symmetry between the inlets of the two irregularly shaped hollow cavity flow channels II in the adjacent segmented module.

[0027] The preparation method of ultrafine fiber with multi-layer composite structure melt spinning and fiber opening coupling as described above, the spinneret module includes a metal body Ⅲ and a special-shaped hollow cavity flow channel Ⅲ that runs through the interior of the metal body Ⅲ. The shape of the special-shaped hollow cavity flow channel Ⅲ is a regular square truncated pyramid, with the large end being the feed port and the small end being the spinneret.

[0028] The vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 25~150mm.

[0029] The present invention also provides a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber, which is obtained by opening a composite fiber with a periodically alternating stacked layer structure; before fiber opening, it is a multi-layer composite filament with two polymers arranged in a periodic alternation; after fiber opening, each ultrafine fiber corresponds to a single polymer layer in the original composite fiber and extends continuously along the fiber axis, and its thickness is close to the original single layer thickness.

[0030] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total number of stacked layers of 64 to 2048; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0031] In composite fibers with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 0.1~5μm, and the coefficient of variation of the thickness of all layers is ≤5%.

[0032] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer.

[0033] The two phases A and B of the busbar module form a two-layer structure. Each additional segmentation module doubles the number of layers, resulting in 2 layers. n+1Layers (n represents the number of segmentation modules). This invention prepares ultrafine fibers by splitting a single filament to obtain each layer of independent fibers. In practice, the more layers there are, the smaller the center thickness of the final single-layer fiber. In this invention, the total number of stacked layers is 64~2048, which can controllably obtain a center thickness of 0.1~5μm for the single-layer fiber.

[0034] As a preferred technical solution:

[0035] The multi-layer composite structure of melt spinning and fiber opening coupled ultrafine fiber, as described above, has a breaking strength of 3.2~6.5 cN / dtex and a breaking elongation of 19.6~108.7%. The fiber after fiber opening still maintains a certain load-bearing capacity and elongation capacity, which is at a relatively good level for melt-spun ultrafine fiber.

[0036] Compared with existing technologies, the advantages of the microfibers of this invention are mainly reflected in the following aspects: ① They adopt melt co-extrusion and mechanical fiber opening, without using electrospinning solvents, and do not require selective dissolution to remove the "sea" components like island fibers, which facilitates continuous production and reduces chemical waste; ② The fiber thickness is adjusted by the layer multiplication factor, component ratio, and draw ratio, without relying on processing extremely small spinnerets, which can reduce the risk of micropore blockage; ③ The flat strip-shaped cross-section formed after fiber opening has a large specific surface area and coverage area, which is beneficial to improving the effects of filtration, adsorption, wiping, wetting, and composite material interface bonding; ④ They can be collected in the form of continuous filaments, which is convenient for subsequent winding, weaving, braiding, or directional laying.

[0037] The principle of this invention is as follows:

[0038] The stability of the layered structure of microfibers and the feasibility of subsequent fiber opening stem from the synergistic matching of the thermodynamics and processing properties of the two-component polymers. Thermodynamically, selecting incompatible polymers ensures that molecular chains do not diffuse or permeate during melt blending and cooling, forming a clearly defined interlayer interface that provides a natural dissociation path for fiber opening. In terms of processing properties, by controlling the melt temperature difference to ≤50℃, the melt index difference to ≤5g / 10min, and the melt viscosity ratio to 0.5~1.5, the two melts are kept flowing synchronously in the segmented module channels—avoiding "shear segregation" (low-viscosity melt enveloping high-viscosity melt) or "flow rate imbalance" (layer thickness distortion) caused by viscosity differences, thus ensuring the morphological uniformity of the layered structure from the source.

[0039] The periodic arrangement of layered composite melts is mainly achieved through the "segmentation-stacking" flow channel design of the segmentation module, the core of which is based on the flow distribution and shape maintenance mechanism in fluid mechanics. Initially, the two-component melt forms a two-layer structure through the confluence module and then enters the segmentation module: First, the melt is uniformly split along its width through the segmentation flow channel, utilizing the balance between the shear force of the flow channel wall and the viscosity of the melt itself to ensure consistent flow rate and thickness for each melt component; second, the split melt bundles are re-stacking vertically within the segmentation flow channel, multiplying the total number of layers (after n multiplications, the number of layers is 2). n+1 Ultimately, a periodic layered structure with uniform layer thickness (coefficient of variation ≤ 5%) is formed, laying the foundation for the uniformity of the center thickness of the ultrafine fibers after fiber opening.

[0040] The interlayer interface between two incompatible polymers is dominated by physical adsorption, which is much lower than the intermolecular forces (such as hydrogen bonds and van der Waals forces) within a single component. This results in the fracture toughness of the A / B interface being lower than the bulk fracture toughness of layers A and B. Under axial stretching, repeated bending, directional friction, or differential shearing, the two polymers undergo inconsistent deformation due to differences in elastic modulus, yield strain, Poisson's shrinkage, crystal orientation, and cooling shrinkage behavior. This leads to the formation of normal peel stress and tangential shear stress at the A / B interface. These interfacial stresses first cause stress concentration at the free edges of the layered structure, at locations of layer thickness fluctuations, or at local interfacial defects, inducing interfacial crack initiation. When the energy release rate of the interfacial cracks generated by mechanical action reaches or exceeds the critical fracture energy of the A / B interface, while the stress within the single-layer polymer is still lower than its bulk fracture strength, the crack preferentially propagates along the continuous A / B interface towards the fiber axis, without penetrating the polymer layer itself. As multiple A / B interfaces peel off sequentially, the original periodically alternating layered composite fibers separate into multiple continuous ultrafine fibers composed of polymer A or polymer B. The thickness of each ultrafine fiber is basically the same as the thickness of the corresponding polymer layer before fiber opening, and finally ultrafine fibers with a central thickness consistent with the original layer thickness (0.1~5μm) are obtained.

[0041] In summary, this invention achieves continuous and controllable preparation of ultrafine fibers through the synergistic effect of the aforementioned core technologies: first, ensuring interlayer dissociability through material interface design; second, precisely constructing layered periodic structures using segmentation modules; and third, utilizing mechanical force to directionally amplify interfacial stress. This synergistic mechanism effectively overcomes the core technological bottlenecks of traditional processes in terms of preparation efficiency, product uniformity, and environmental friendliness.

[0042] Beneficial effects:

[0043] (1) In the process of melt spinning, the present invention introduces a multi-layer composite fluid structure to realize the periodic layered distribution within the fiber cross section, and uses the difference in physical properties of the interlayer interface to induce separation or decoupling, thereby obtaining ultrafine fibers with controllable central thickness and uniform structure, which meets the requirements of material compatibility, high precision and controllability.

[0044] (2) The present invention adopts mechanical fiber opening process to directionally peel off along the interlayer interface, decompose the multilayer composite fiber into ultrafine fiber unit, take into account both structural integrity and fiber precision, avoid the problems of high fiber breakage rate and wide diameter distribution in traditional methods, and realize efficient and repeatable ultrafine fiber preparation.

[0045] (3) This invention achieves continuous adjustment of the central layer thickness in the range of 0.1~5μm by synergistic control of the layer multiplication number and the drawing process. Combined with the continuous process of high-speed spinning (1000m / min) of melt spinning, it improves production efficiency and realizes the preparation technology of ultrafine fiber with controllable fiber fineness and layer structure, continuous production and environmental friendliness. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the preparation process of a multilayer composite structure ultrafine fiber with melt spinning and fiber opening coupling according to the present invention;

[0047] Figure 2 The diagram shows the left view, internal flow channel structure, and melt changes of the spinning apparatus for preparing multi-layered fibers according to the present invention; in the diagram, a is the left view of the spinning apparatus for preparing multi-layered fibers, and b is a schematic diagram of the changes of the melt as it passes through the confluence module and two dividing modules in sequence.

[0048] Figure 3 This is a right view of the spinning apparatus of the present invention for preparing multilayer structured fibers;

[0049] Figure 4 This is a partial cross-sectional schematic diagram of the segmentation module of the present invention;

[0050] Figure 5 This is a microscope image of the ultrafine fibers obtained in Example 2 of the present invention;

[0051] Figure 6 This is a microscope image of the ultrafine fibers obtained in Example 4 of the present invention;

[0052] Figure 7 This is a microscope image of the ultrafine fibers obtained in Example 7 of the present invention;

[0053] Figure 8 This is a microscope image of the ultrafine fibers obtained in Example 9 of the present invention;

[0054] In the diagram, 1-flow confluence module, 11-metal body I, 2-segmentation module, 21-metal body II, 22-irregular hollow cavity flow channel II, 23-first segmentation partition, 24-second segmentation partition, 25-first flow guide partition, 26-second flow guide partition, 27-third flow guide partition, 28-fourth flow guide partition, 3-spinneret module, 31-metal body III, 32-irregular hollow cavity flow channel III, 41-twin-screw extruder A, 42-twin-screw extruder B, 5-hot roller stretching device, 6-winding and stretching device, 7-high-speed winding machine. Detailed Implementation

[0055] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0056] The manufacturers and brands mentioned in the following embodiments are merely examples. The core of this invention lies in the technical solution itself, and it is not intended to limit specific manufacturers or brands. Products from other manufacturers and brands that meet the technical requirements and performance indicators specified in this invention can also meet the application requirements of this invention and are all feasible choices.

[0057] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0058] Thickness variation coefficient: First, the diameter of the fiber sample was obtained according to GB / T 36422-2018 "Determination of Microstructure and Diameter of Chemical Fibers by Scanning Electron Microscopy". Then, the thickness variation coefficient was calculated by the formula: Thickness variation coefficient CV = s / t̄ × 100%, where s is the standard deviation of the thickness of the center layer of each fiber layer and t̄ is the average thickness of the center layer of each fiber layer. During the test, liquid nitrogen brittle fracture was selected to obtain a cross-section perpendicular to the fiber axis. A scanning electron microscope (GeminiSEM 560) was used to image the fiber single layer center thickness with a fixed accelerating voltage of 5~10kV and a fixed working distance (no specific standard, 8~12mm) to obtain a clear interface.

[0059] Breaking strength of microfiber: The breaking strength and elongation at break of the samples were determined using a fiber strength tester (model XL-2).

[0060] Melting temperature: The melting temperature of the sample was determined using a differential scanning calorimeter (manufacturer: Netzsch, Germany, model: DSC 204 F1).

[0061] Melt flow index: The melt flow index of the sample was determined using a melt flow index tester (model XRZ400). The load used in the test was 2.16 kg. The test temperature was adjusted according to the test object. The test temperature was 230℃ when the sample material was PE, PP, PMMA, PS, or PU, and 260℃ when the sample material was PET, PBT, PA6, PA66, or PC.

[0062] Spinning apparatus for preparing multilayer composite structure melt spinning coupled with fiber opening of ultrafine fibers, such as... Figures 2-4 As shown, it includes a busbar module 1, a spinneret module 3, and a segmentation module 2 located between the busbar module 1 and the spinneret module 3;

[0063] like Figure 2 As shown, the manifold module 1 is used to connect twin-screw extruder A and twin-screw extruder B. Both twin-screw extruder A and twin-screw extruder B are divided into a feeding section, a melting section and an extrusion section.

[0064] The bus module 1 includes a metal body I 11 and two irregularly shaped hollow cavity flow channels I that are disposed inside the metal body I 11;

[0065] The inlets of the two irregularly shaped hollow cavity flow channels I are located on different planes, while the outlets are symmetrically arranged on the same plane, and the inlets and any of the outlets are not on the same plane; the inlets of the two irregularly shaped hollow cavity flow channels I are circles of the same size, and the outlets are rectangles of the same size;

[0066] The axis of symmetry between the outlets of the two irregularly shaped hollow cavity flow channels I in the merging module 1 is perpendicular to the axis of symmetry between the inlets of the two irregularly shaped hollow cavity flow channels II 22 in the adjacent segmented module 2.

[0067] like Figure 2 , 4 As shown, the dividing module 2 is used to connect the confluence module 1 and the spinneret module 3, including a metal body II 21 and two irregularly shaped hollow cavity flow channels II 22 that penetrate the interior of the metal body II 21. The two irregularly shaped hollow cavity flow channels II 22 are separated by a partition.

[0068] The inlets of the two irregular hollow cavity flow channels II 22 are located on the same plane, the outlets are located on the same plane, and the planes where the inlets and outlets are located are parallel to each other. The inlets and outlets are rectangles of the same size.

[0069] The baffle includes a first dividing baffle 23, a second dividing baffle 24, a first diversion baffle 25, a second diversion baffle 26, a third diversion baffle 27, and a fourth diversion baffle 28; the first dividing baffle 23 is perpendicular to the plane where the feed inlet is located, the second dividing baffle 24 is perpendicular to the plane where the discharge outlet is located, and the first dividing baffle 23 and the second dividing baffle 24 are perpendicular to each other;

[0070] One irregular hollow cavity flow channel II 22 is formed by the first dividing baffle 23, the first drainage baffle 25, the third drainage baffle 27 and the wall of the metal body II 21; the other irregular hollow cavity flow channel II 22 is formed by the second dividing baffle 24, the second drainage baffle 26, the fourth drainage baffle 28 and the wall of the metal body II 21.

[0071] A three-dimensional rectangular coordinate system is constructed with the thickness direction of the first partition plate as the x-axis, the width direction as the y-axis, and the length direction as the z-axis. In the irregular hollow cavity flow channel II 22, from the inlet to the outlet, the distance in the x-axis direction remains unchanged and the distance in the y-axis direction gradually decreases. Then, the distance in the y-axis direction remains unchanged and the distance in the x-axis direction gradually increases.

[0072] The number of segmentation modules 2 is 5 to 10, and the first segmentation partition 23 in each segmentation module 2 is perpendicular to the second segmentation partition 24 in the adjacent segmentation module 2;

[0073] The spinneret module 3 includes a metal body Ⅲ 31 and a hollow cavity flow channel Ⅲ 32 that runs through the interior of the metal body Ⅲ 31. The hollow cavity flow channel Ⅲ 32 is shaped like a regular square truncated pyramid, with the large end being the feed inlet and the small end being the spinneret outlet.

[0074] In the spinneret module 3, the vertical distance between the feed inlet and the spinneret nozzle of the irregular hollow cavity flow channel Ⅲ 32 is 25~150mm;

[0075] The merging module 1, the dividing module 2, and the spinneret module 3 are all assembled using bolts and screws.

[0076] Example 1

[0077] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0078] (1) Preparation of raw materials;

[0079] Polymer material A: PA6, melting temperature 215℃, thermal decomposition temperature 375℃, melt index 4g / 10min;

[0080] Polymer material B: PET, melting temperature 255℃, thermal decomposition temperature 380℃, melt index 6g / 10min;

[0081] In the spinning device for preparing multi-layer composite structure melt spinning and fiber opening coupling ultrafine fibers, the number of dividing modules is 9; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 100mm;

[0082] (2) For example Figure 1 As shown, polymer materials A and B were first dried in a vacuum oven at 90℃ for 8 hours, with the moisture content controlled to be ≤0.1%. Then, polymer material A was melt-extruded using a twin-screw extruder A 41, and polymer material B was melt-extruded using a twin-screw extruder B 42. After passing through the manifold module, the two melts sequentially entered the segmentation module 2 and the spinneret module, and solidified after passing through the spinneret module to form nascent fibers. The melt viscosity ratio of polymer materials A and B was 0.75; the extrusion rate was 3 kg / h for both. Heating tapes and thermocouples were wrapped around the manifold module, segmentation module, and spinneret module for heating and temperature measurement, with a heating temperature of 260℃.

[0083] The feed section temperature of twin-screw extruder A is 115℃, the melting section temperature is 230℃, and the extrusion section temperature is 240℃.

[0084] The feed section temperature of twin-screw extruder B is 125℃, the melt section temperature is 265℃, and the extrusion section temperature is 275℃.

[0085] (3) such as Figure 1 As shown, the nascent fiber is introduced into the hot roller drawing device 5 for drawing, and then the drawn nascent fiber is opened by the winding and stretching process. Then, the winding operation is completed by the equal pitch high-speed winding machine 7 with a speed of 4500 r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0086] Process parameters of the hot roll drawing device: First-stage roll temperature is 80℃, first-stage roll speed is 200m / min; second-stage roll temperature is 140℃, second-stage roll speed is 250m / min; third-stage roll temperature is 140℃, third-stage roll speed is 400m / min.

[0087] Winding and stretching refers to the nascent fiber sequentially passing around the front and rear drafting rollers of the winding and stretching device 6. The linear speed of the rear drafting roller is higher than that of the front drafting roller, so that the fiber is subjected to continuous axial stretching. The linear speed of the front drafting roller is 400 m / min, the drafting ratio is 2.5 times, and the winding linear speed is 900 m / min.

[0088] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0089] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 1024 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0090] The composite fiber with a periodically alternating stacked layered structure has a single-layer center thickness of 0.23 μm and a thickness variation coefficient of 4.73% for all layers.

[0091] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0092] The microfiber has a breaking strength of 3.97 cN / dtex and a breaking elongation of 19.7%.

[0093] Example 2

[0094] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0095] (1) Preparation of raw materials;

[0096] Polymer material A: PS, melting temperature 105℃, thermal decomposition temperature 330℃, melt index 2g / 10min;

[0097] Polymer material B: PMMA, melting temperature 115℃, thermal decomposition temperature 290℃, melt index 5g / 10min;

[0098] In the spinning device for preparing multi-layer composite structure melt spinning and fiber opening coupled ultrafine fibers, the number of dividing modules is 10; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0099] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 1.5. The extrusion rate is 5 kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 255℃.

[0100] The feed section temperature of twin-screw extruder A is 95℃, the melting section temperature is 210℃, and the extrusion section temperature is 240℃.

[0101] The feed section temperature of twin-screw extruder B is 95℃, the melt section temperature is 235℃, and the extrusion section temperature is 255℃.

[0102] (3) The nascent fibers are introduced into the hot roller drawing device for drawing, and then the drawn nascent fibers are opened using a directional friction process. Subsequently, the winding operation is completed by a high-speed winding machine with a constant pitch of 4000 r / min, which produces a multi-layer composite structure melt spinning coupled with fiber opening ultrafine fiber (its microscope image is shown in Figure 1). Figure 5 (as shown)

[0103] Process parameters of the hot roll drawing device: First-stage roll temperature is 70℃, first-stage roll speed is 400m / min; second-stage roll temperature is 120℃, second-stage roll speed is 500m / min; third-stage roll temperature is 120℃, third-stage roll speed is 1000m / min.

[0104] Directional friction refers to the continuous contact of nascent fibers with the surface of a friction element along their length extension direction at a set wrap angle, causing tangential friction between the fibers and the friction element during operation. The tangential friction and local compression between the fibers and the contact surface promote fiber opening. The friction element is a ceramic guide. There is only one friction element, and the wrap angle of the fiber on a single friction element is 90°.

[0105] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0106] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 2048 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0107] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 0.1 μm, and the coefficient of variation of the thickness of all layers is 4.15%.

[0108] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0109] The microfiber has a breaking strength of 5.02 cN / dtex and a breaking elongation of 42.6%.

[0110] Example 3

[0111] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0112] (1) Preparation of raw materials;

[0113] Polymer material A: PP, melting temperature 165℃, thermal decomposition temperature 350℃, melt index 3g / 10min;

[0114] Polymer material B: PE, melting temperature 130℃, thermal decomposition temperature 340℃, melt index 5g / 10min;

[0115] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 6; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 25mm;

[0116] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 1.2. The extrusion rate is 1 kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 180℃.

[0117] The feed section temperature of twin-screw extruder A is 90℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0118] The feed section temperature of twin-screw extruder B is 100℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0119] (3) The nascent fiber is introduced into the hot roller drawing device for drawing, and then the drawn nascent fiber is opened by the shear disturbance process. Then the winding operation is completed by the equal pitch high-speed winding machine with a speed of 4500r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0120] Process parameters of the hot roll drawing device: First-stage roll temperature is 50℃, first-stage roll speed is 300m / min; second-stage roll temperature is 100℃, second-stage roll speed is 450m / min; third-stage roll temperature is 100℃, third-stage roll speed is 900m / min.

[0121] Shear disturbance refers to the local shearing, bending, and slight twisting of nascent fibers as they pass through a pair of differential rollers; the linear velocity ratio of the differential rollers is 1.06.

[0122] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0123] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 128 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0124] The composite fiber with a periodically alternating stacked layered structure has a single-layer center thickness of 1.83 μm and a thickness variation coefficient of 4.82% for all layers.

[0125] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0126] The microfiber has a breaking strength of 4.2 cN / dtex and a breaking elongation of 39.6%.

[0127] Example 4

[0128] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0129] (1) Preparation of raw materials;

[0130] Polymer material A: PA66, melting temperature 260℃, thermal decomposition temperature 380℃, melt index 6g / 10min;

[0131] Polymer material B: PET, melting temperature 255℃, thermal decomposition temperature 380℃, melt index 6g / 10min;

[0132] In the spinning device for preparing multi-layer composite structure melt spinning and fiber opening coupling ultrafine fibers, the number of dividing modules is 8; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 100mm.

[0133] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.9. The extrusion rate is 5 kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 260℃.

[0134] The feed section temperature of twin-screw extruder A is 140℃, the melting section temperature is 270℃, and the extrusion section temperature is 280℃.

[0135] The feed section temperature of twin-screw extruder B is 125℃, the melt section temperature is 265℃, and the extrusion section temperature is 275℃.

[0136] (3) The nascent fibers are introduced into the hot roller drawing device for drawing, and then the drawn nascent fibers are opened by the winding and stretching process. Then, the winding operation is completed by the constant pitch high-speed winding machine with a speed of 4500 r / min, that is, the multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber (its microscope image is shown in the figure). Figure 6 (as shown)

[0137] The process parameters of the hot roll drawing device are as follows: the temperature of the first-stage roll is 90℃ and the speed of the first-stage roll is 200m / min; the temperature of the second-stage roll is 150℃ and the speed of the second-stage roll is 250m / min; the temperature of the third-stage roll is 150℃ and the speed of the third-stage roll is 400m / min.

[0138] Winding stretching refers to the process where nascent fibers sequentially pass around the front and rear drafting rollers. The linear speed of the rear drafting roller is higher than that of the front drafting roller, causing the fiber to be subjected to continuous axial stretching. The linear speed of the front drafting roller is 400 m / min, the drafting ratio is 3, and the winding linear speed is 1200 m / min.

[0139] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0140] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 512 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0141] The composite fiber with a periodically alternating stacked layered structure has a single-layer center thickness of 0.92 μm and a thickness variation coefficient of 4.27% for all layers.

[0142] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0143] The microfiber has a breaking strength of 6.1 cN / dtex and a breaking elongation of 19.6%.

[0144] Example 5

[0145] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0146] (1) Preparation of raw materials;

[0147] Polymer material A: PP, melting temperature 165℃, thermal decomposition temperature 350℃, melt index 3g / 10min;

[0148] Polymer material B: PA6, melting temperature 215℃, thermal decomposition temperature 375℃, melt index 4g / 10min;

[0149] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 7; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0150] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.8. The extrusion rate is 2.5 kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 200℃.

[0151] The feed section temperature of twin-screw extruder A is 105℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0152] The feed section temperature of twin-screw extruder B is 115℃, the melting section temperature is 230℃, and the extrusion section temperature is 240℃.

[0153] (3) The nascent fiber is introduced into the hot roller drawing device for drawing, and then the drawn nascent fiber is opened by the winding and stretching process. Then, the winding operation is completed by the equal pitch high-speed winding machine with a speed of 4500r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0154] Process parameters of the hot roll drawing device: First-stage roll temperature is 80℃, first-stage roll speed is 200m / min; second-stage roll temperature is 140℃, second-stage roll speed is 250m / min; third-stage roll temperature is 140℃, third-stage roll speed is 400m / min.

[0155] Winding stretching refers to the process where nascent fibers sequentially pass around the front and rear drafting rollers. The linear speed of the rear drafting roller is higher than that of the front drafting roller, causing the fiber to be subjected to continuous axial stretching. The linear speed of the front drafting roller is 400 m / min, the drafting ratio is 3, and the winding linear speed is 1200 m / min.

[0156] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0157] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 256 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0158] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 1.2 μm, and the coefficient of variation of the thickness of all layers is 4.61%.

[0159] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0160] The microfiber has a breaking strength of 6.5 cN / dtex and a breaking elongation of 37%.

[0161] Example 6

[0162] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0163] (1) Preparation of raw materials;

[0164] Polymer material A: PP, melting temperature 165℃, thermal decomposition temperature 350℃, melt index 3g / 10min;

[0165] Polymer material B: PU, melting temperature 180℃, thermal decomposition temperature 280℃, melt index 6g / 10min;

[0166] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 7; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0167] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.86. The extrusion rate is 5kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 250℃.

[0168] The feed section temperature of twin-screw extruder A is 105℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0169] The feed section temperature of twin-screw extruder B is 125℃, the melting section temperature is 210℃, and the extrusion section temperature is 240℃.

[0170] (3) The nascent fiber is introduced into the hot roller drawing device for drawing, and then the drawn nascent fiber is opened by the shear disturbance process. Then the winding operation is completed by the equal pitch high-speed winding machine with a speed of 4500r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0171] Process parameters of the hot roll drawing device: First-stage roll temperature 70℃, first-stage roll speed 400m / min; second-stage roll temperature 120℃, second-stage roll speed 600m / min; third-stage roll temperature 120℃, third-stage roll speed 900m / min;

[0172] Shear disturbance refers to the local shearing, bending, and slight twisting of the nascent fiber as it passes through the staggered guide rollers; the deflection angle between the staggered guide rollers is 5°.

[0173] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0174] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 256 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0175] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 0.6 μm, and the coefficient of variation of the thickness of all layers is 4.48%.

[0176] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0177] The microfiber has a breaking strength of 4.5 cN / dtex and a breaking elongation of 108.7%.

[0178] Example 7

[0179] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0180] (1) Preparation of raw materials;

[0181] Polymer material A: PP, melting temperature 165℃, thermal decomposition temperature 350℃, melt index 3g / 10min;

[0182] Polymer material B: PMMA, melting temperature 115℃, thermal decomposition temperature 290℃, melt index 5g / 10min;

[0183] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 8; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0184] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.8. The extrusion rate is 3kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 245℃.

[0185] The feed section temperature of twin-screw extruder A is 105℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0186] The feed section temperature of twin-screw extruder B is 95℃, the melt section temperature is 235℃, and the extrusion section temperature is 255℃.

[0187] (3) The nascent fibers are introduced into the hot roller drawing device for drawing, and then the drawn nascent fibers are opened by the winding and stretching process. Then, the winding operation is completed by the constant pitch high-speed winding machine with a speed of 4500 r / min, that is, the multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber (its microscope image is shown in the figure). Figure 7 (as shown)

[0188] The process parameters of the hot roll drawing device are as follows: the temperature of the first-stage roll is 70℃ and the speed of the first-stage roll is 200m / min; the temperature of the second-stage roll is 120℃ and the speed of the second-stage roll is 250m / min; the temperature of the third-stage roll is 120℃ and the speed of the third-stage roll is 400m / min.

[0189] Winding stretching refers to the process where nascent fibers sequentially pass around the front and rear drafting rollers. The linear speed of the rear drafting roller is higher than that of the front drafting roller, causing the fibers to be subjected to continuous axial stretching. The linear speed of the front drafting roller is 400 m / min, the drafting ratio is 2.5, and the winding linear speed is 1200 m / min.

[0190] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0191] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 512 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0192] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 0.95 μm, and the coefficient of variation of the thickness of all layers is 4.39%.

[0193] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0194] The microfiber has a breaking strength of 5.7 cN / dtex and a breaking elongation of 42%.

[0195] Example 8

[0196] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0197] (1) Preparation of raw materials;

[0198] Polymer material A: PS, melting temperature 105℃, thermal decomposition temperature 330℃, melt index 2g / 10min;

[0199] Polymer material B: PE, melting temperature 130℃, thermal decomposition temperature 340℃, melt index 5g / 10min;

[0200] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 5; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0201] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.9. The extrusion rate is 2kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 240℃.

[0202] The feed section temperature of twin-screw extruder A is 95℃, the melt section temperature is 240℃, and the extrusion section temperature is 250℃.

[0203] The feed section temperature of twin-screw extruder B is 100℃, the melting section temperature is 210℃, and the extrusion section temperature is 230℃.

[0204] (3) The nascent fiber is introduced into the hot roller drawing device for drawing, and then the drawn nascent fiber is opened by the winding and stretching process. Then the winding operation is completed by the equal pitch high-speed winding machine with a speed of 5000r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0205] The process parameters of the hot roll drawing device are as follows: the temperature of the first-stage roll is 70℃ and the speed of the first-stage roll is 300m / min; the temperature of the second-stage roll is 120℃ and the speed of the second-stage roll is 360m / min; the temperature of the third-stage roll is 120℃ and the speed of the third-stage roll is 450m / min.

[0206] Winding stretching refers to the process where nascent fibers sequentially pass around the front and rear drafting rollers. The linear speed of the rear drafting roller is higher than that of the front drafting roller, causing the fiber to be subjected to continuous axial stretching. The linear speed of the front drafting roller is 450 m / min, the drafting ratio is 2, and the winding linear speed is 800 m / min.

[0207] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0208] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 64 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0209] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 5 μm, and the coefficient of variation of the thickness of all layers is 4.87%.

[0210] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0211] The microfiber has a breaking strength of 3.2 cN / dtex and a breaking elongation of 68.5%.

[0212] Example 9

[0213] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0214] (1) Preparation of raw materials;

[0215] Polymer material A: PC, melting temperature 145℃, thermal decomposition temperature 340℃, melt index 2.5g / 10min;

[0216] Polymer material B: PMMA, melting temperature 115℃, thermal decomposition temperature 290℃, melt index 7g / 10min;

[0217] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 6; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 50mm;

[0218] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 0.5. The extrusion rate is 2kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 245℃.

[0219] The feed section temperature of twin-screw extruder A is 135℃, the melting section temperature is 240℃, and the extrusion section temperature is 250℃.

[0220] The feed section temperature of twin-screw extruder B is 95℃, the melt section temperature is 265℃, and the extrusion section temperature is 275℃.

[0221] (3) The nascent fibers are introduced into the hot roller drawing device for drawing, and then the drawn nascent fibers are opened using a directional friction process. Then, the winding operation is completed by a high-speed winding machine with a constant pitch of 4500 r / min, which produces a multi-layer composite structure melt spinning coupled with fiber opening ultrafine fiber (its microscope image is shown in Figure 1). Figure 8 (as shown)

[0222] Process parameters of the hot roll drawing device: First-stage roll temperature is 80℃, first-stage roll speed is 300m / min; second-stage roll temperature is 140℃, second-stage roll speed is 450m / min; third-stage roll temperature is 140℃, third-stage roll speed is 900m / min.

[0223] Directional friction refers to the continuous contact of nascent fibers with the surface of a friction element along the length extension direction at a set wrap angle, so that the fibers generate tangential friction with the friction element during operation. The tangential friction and local compression between the fibers and the contact surface promote fiber opening. The friction element is a friction roller. There are two friction elements, and the wrap angle of the fiber on a single friction element is 90°.

[0224] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0225] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 128 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0226] In the composite fiber with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 1.5 μm, and the coefficient of variation of the thickness of all layers is 4.65%.

[0227] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0228] The microfiber has a breaking strength of 5.8 cN / dtex and a breaking elongation of 45%.

[0229] Example 10

[0230] A method for preparing ultrafine fibers with a multilayer composite structure through melt spinning and fiber opening coupling, using the above-mentioned spinning apparatus, includes the following specific steps:

[0231] (1) Preparation of raw materials;

[0232] Polymer material A: PA66, melting temperature 260℃, thermal decomposition temperature 380℃, melt index 6g / 10min;

[0233] Polymer material B: PBT, melting temperature 225℃, thermal decomposition temperature 350℃, melt index 8g / 10min;

[0234] In the spinning device for preparing ultrafine fibers with multi-layer composite structure melt spinning and fiber opening coupling, the number of dividing modules is 8; the feed inlet size of the spinneret module is 8mm×8mm, the spinneret is rectangular with a long side dimension of 2mm and a short side dimension of 1mm; the vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 150mm;

[0235] (2) First, polymer material A and polymer material B are dried in a vacuum oven at 90℃ for 8 hours, and the moisture content is controlled to be ≤0.1%. Then, polymer material A is melt-extruded using a twin-screw extruder A, and polymer material B is melt-extruded using a twin-screw extruder B. After passing through the confluence module, the two melts enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, they are solidified to form nascent fibers. The melt viscosity ratio of polymer material A and polymer material B is 1.06. The extrusion rate is 3kg / h. Heating tape and thermocouples are wrapped around the confluence module, segmentation module and spinneret module for heating and temperature measurement. The heating temperature is 280℃.

[0236] The feed section temperature of twin-screw extruder A is 130℃, the melting section temperature is 270℃, and the extrusion section temperature is 280℃.

[0237] The feed section temperature of twin-screw extruder B is 125℃, the melt section temperature is 245℃, and the extrusion section temperature is 255℃.

[0238] (3) The nascent fiber is introduced into the hot roller drawing device for drawing, and then the drawn nascent fiber is opened by the shear disturbance process. Then the winding operation is completed by the equal pitch high-speed winding machine with a speed of 4500r / min, which is a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber.

[0239] The process parameters of the hot roll drawing device are as follows: the temperature of the first-stage roll is 90℃ and the speed of the first-stage roll is 400m / min; the temperature of the second-stage roll is 150℃ and the speed of the second-stage roll is 600m / min; the temperature of the third-stage roll is 150℃ and the speed of the third-stage roll is 1200m / min.

[0240] Shear disturbance refers to the local shearing, bending and slight twisting of the nascent fiber as it passes through the staggered guide rollers; the deflection angle between the staggered guide rollers is 10°.

[0241] The resulting multilayer composite structure melt spinning and fiber opening coupled ultrafine fiber is obtained by opening the composite fiber with a periodically alternating stacked layered structure.

[0242] The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total of 512 stacked layers; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle;

[0243] The composite fiber with a periodically alternating stacked layered structure has a single-layer center thickness of 0.98 μm and a thickness variation coefficient of 4.54% for all layers.

[0244] Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer;

[0245] The microfiber has a breaking strength of 5.1 cN / dtex and a breaking elongation of 27.8%.

Claims

1. A method for preparing ultrafine fibers with a multilayer composite structure, characterized by melt spinning and fiber opening coupling: First, two melt-spinnable and incompatible polymer materials are melt-extruded separately. After passing through the confluence module, the melts of each material enter the segmentation module and the spinneret module in sequence. After passing through the spinneret module, the melts solidify to form nascent fibers. Finally, the nascent fibers are opened to obtain multi-layer composite structure melt-spinned and opened ultrafine fibers. The segmentation module includes a metal body II and two irregularly shaped hollow cavity flow channels II that penetrate the interior of the metal body II. The two irregularly shaped hollow cavity flow channels II are separated by a partition. The inlets and outlets of the two irregularly shaped hollow cavity flow channels II are located on the same plane, and the planes containing the inlets and outlets are parallel to each other. The inlets and outlets are rectangles of the same size. The partition includes a first segmentation partition, a second segmentation partition, a first guide partition, a second guide partition, a third guide partition, and a fourth guide partition. The first segmentation partition is perpendicular to the plane containing the inlet, and the second segmentation partition is perpendicular to the plane containing the outlet. The first segmentation partition is perpendicular to the plane containing the inlet. The second partition plates are perpendicular to each other; one irregular hollow cavity flow channel II is formed by the first partition plate, the first diversion partition plate, the third diversion partition plate and the wall of metal body II, and the other irregular hollow cavity flow channel II is formed by the second partition plate, the second diversion partition plate, the fourth diversion partition plate and the wall of metal body II; a three-dimensional rectangular coordinate system is constructed with the thickness direction of the first partition plate as the x-axis, the width direction as the y-axis and the length direction as the z-axis. In the irregular hollow cavity flow channel II, from the inlet to the outlet, the distance in the x-axis direction is constant at first and the distance in the y-axis direction gradually decreases, and then the distance in the y-axis direction is constant and the distance in the x-axis direction gradually increases. The number of segmentation modules is 5 to 10, and the first segmentation partition in each segmentation module is perpendicular to the second segmentation partition in the adjacent segmentation module.

2. The method for preparing ultrafine fibers with multilayer composite structure, coupled by melt spinning and fiber opening, according to claim 1, is characterized in that, The melting temperatures of the two polymer materials differ by no more than 50°C, the melt indexes differ by no more than 5 g / 10 min, and the melt viscosity ratio is 0.5~1.

5.

3. The method for preparing ultrafine fibers with multilayer composite structure melt spinning and fiber opening coupling according to claim 2, characterized in that, The polymer materials are selected from polypropylene, polyamide, polyester, polycarbonate, polyethylene, polymethyl methacrylate, polystyrene, polyurethane, and their composite systems.

4. The method for preparing ultrafine fibers with multilayer composite structure melt spinning and fiber opening coupling according to claim 3, characterized in that, Twin-screw extruders are used for melt extrusion at an extrusion rate of 1~5 kg / h. Both twin-screw extruders are divided into a feeding section, a melting section, and an extrusion section, with the temperature settings for the three sections being 90~140℃, 210~270℃, and 230~280℃, respectively. Heating tape and thermocouples are wrapped around the busbar module, splitting module and spinneret module for heating and temperature measurement, with a heating temperature of 180~280℃.

5. The method for preparing a multi-layer composite structure melt spinning and fiber opening coupled ultrafine fiber according to claim 1, characterized in that, The fiber is opened using a mechanical stripping process, and the mechanical stripping method is at least one of winding and stretching, directional friction and shear disturbance; Winding stretching refers to the process where nascent fibers pass sequentially around the front and rear drafting rollers. The linear speed of the rear drafting roller is higher than that of the front drafting roller, causing the fibers to be subjected to continuous axial stretching. The drafting ratio is 2 to 3 times, and the winding linear speed is 800 to 1200 m / min. Directional friction refers to the continuous contact of nascent fibers with the surface of a friction element along their length extension direction at a set wrap angle, causing tangential friction between the fibers and the friction element during operation. The tangential friction and local compression between the fibers and the contact surface promote fiber opening. The friction element can be a friction roller, a ceramic guide, or a surface roughening guide. The number of friction elements is 1 to 3, and the wrap angle of the fiber on a single friction element is 90° to 180°. Shear disturbance refers to the local shearing, bending and slight twisting of nascent fibers as they pass through a pair of differential rollers or staggered guide rollers; the linear speed ratio of the differential rollers is 1.03~1.10, and the guide deflection angle between the staggered guide rollers is 5°~15°.

6. The method for preparing ultrafine fibers with multilayer composite structure, coupled by melt spinning and fiber opening, according to claim 1, is characterized in that, The manifold module is used to connect two screw extruders, and the splitting module is used to connect the manifold module and the spinneret module. The manifold module, splitting module, and spinneret module are all assembled with bolts and screws.

7. The method for preparing ultrafine fibers with multilayer composite structure, coupled by melt spinning and fiber opening, according to claim 1, is characterized in that, The bus module includes a metal body I and two irregularly shaped hollow cavity flow channels I that are disposed inside the metal body I. The inlets of the two irregularly shaped hollow cavity flow channels I are located on different planes, and the outlets are symmetrically arranged on the same plane, and the inlets and any outlets are not on the same plane. The inlets of the two irregularly shaped hollow cavity flow channels I are circular and the outlets are rectangular. The axis of symmetry between the outlets of the two irregularly shaped hollow cavity flow channels I in the merge module is perpendicular to the axis of symmetry between the inlets of the two irregularly shaped hollow cavity flow channels II in the adjacent segmented module.

8. The method for preparing ultrafine fibers with multilayer composite structure melt spinning and fiber opening coupling according to claim 1, characterized in that, The spinneret module includes a metal body Ⅲ and a hollow cavity flow channel Ⅲ that runs through the interior of the metal body Ⅲ. The hollow cavity flow channel Ⅲ is shaped like a regular square truncated pyramid, with the large end being the feed inlet and the small end being the spinneret outlet. The vertical distance between the feed inlet and the spinneret in the irregular hollow cavity flow channel III of the spinneret module is 25~150mm.

9. A multi-layer composite structure of melt spinning and fiber opening coupled ultrafine fiber, characterized in that: It is obtained by opening composite fibers with a periodically alternating stacked layered structure; The composite fiber with a periodically alternating stacked layered structure is composed of a first polymer layer and a second polymer layer extending along the fiber axis, with a total number of stacked layers of 64 to 2048; in the cross-sectional direction of the composite fiber, multiple first polymer layers and multiple second polymer layers are arranged alternately, and the first polymer layer and the adjacent second polymer layer form a repeating cycle; In composite fibers with a periodically alternating stacked layered structure, the thickness of a single layer at the center is 0.1~5μm, and the coefficient of variation of the thickness of all layers is ≤5%. Each microfiber is a flat-shaped fiber formed by separating a single continuous polymer layer.

10. The multi-layer composite structure melt-spun and fiber-opening coupled ultrafine fiber according to claim 9, characterized in that, The tensile strength of the microfiber is 3.2~6.5 cN / dtex, and the elongation at break is 19.6~108.7%.

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