Second-order cross fiber and method for manufacturing the same

Abstract

This invention relates to second-order cross-shaped fibers and their preparation method. The fiber is formed from a polymer and has a multi-level cross-shaped cross-shaped structure in its cross-section, including a primary cross-shaped trunk structure formed with the center of the cross-section as the origin, and secondary cross-shaped branch structures disposed at the four ends of the primary cross-shaped trunk structure. The size of the secondary cross-shaped branch structures is smaller than or equal to that of the primary cross-shaped trunk structure. Through this structural design, the fiber has a hierarchical structural distribution and forms a capillary channel structure on the fiber surface. The preparation method includes melt extrusion, air blowing cooling, and drawing steps, wherein a multi-stage air blowing cooling process is adopted, consisting of a slow cooling zone, a ring blowing zone, and a forward blowing zone arranged sequentially. Through the combination of the above structure and process, it is beneficial to improve the fiber's ability to maintain its cross-sectional structure and improve its moisture absorption and wicking properties, while also enabling the fiber to form a differentiated stiffness distribution in the radial direction.

Description

Technical Field

[0001] This invention relates to the field of textile fiber preparation technology, and in particular to a second-order cross fiber and its preparation method. Background Technology

[0002] In the field of chemical fibers, the cross-sectional structure of fibers not only affects their mechanical properties, but also directly relates to the feel, comfort, and moisture-wicking properties of fabrics.

[0003] In existing technologies, conventional synthetic fibers mostly adopt a circular or near-circular cross-sectional structure. While these fibers have a uniform structure and stable mechanical properties, their smooth surface and lack of effective grooves make it difficult to form continuous capillary channels, resulting in poor moisture absorption and wicking performance. Furthermore, their overall stiffness distribution is relatively uniform, making it difficult to balance a soft feel with supportive properties.

[0004] To address these issues, various irregularly shaped fiber structures, such as triangular cross-sections and multi-blade structures, have been proposed in the prior art. However, these structures typically focus on optimizing a single performance characteristic, such as improving moisture absorption and wicking capacity or adjusting gloss effects, while lacking effective control over structural stiffness distribution. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a second-order cross-shaped fiber and its preparation method. By designing the fiber cross-section structure, a multi-level cross-shaped structure is formed, resulting in a hierarchical structure distribution in the fiber's radial direction. The internal structure provides support, while the external structure adjusts the surface morphology, giving the fiber both structural stability and surface softness. Simultaneously, the fiber grooves formed by the multi-level structure facilitate liquid conduction on the fiber surface, thereby improving the fiber's moisture absorption and wicking properties.

[0006] According to a first aspect of the invention, a second-order cross-shaped fiber is provided, wherein the fiber is formed of a polymer; The cross-section of the fiber has a multi-level cross-shaped structure, which includes: A primary cross-shaped trunk structure is formed with the center of the cross section as the origin; secondary cross-shaped branch structures are respectively set at the four ends of the primary cross-shaped trunk structure; the size of the secondary cross-shaped branch structures is less than or equal to that of the primary cross-shaped trunk structure.

[0007] In some embodiments, for each of the secondary cross branch structures, among its four extension directions, one pair of opposing extension directions are the same as and collinear with the corresponding direction of the primary cross trunk structure, and another pair of opposing extension directions are the same as and parallel to another pair of directions of the primary cross trunk structure.

[0008] In some embodiments, the ratio of the leaf length of the primary cross-shaped trunk structure to the leaf length of the secondary cross-shaped branch structure is 1 to 4; the ratio of the leaf width of the primary cross-shaped trunk structure to the leaf width of the secondary cross-shaped branch structure is 1 to 2.

[0009] In some embodiments, the relative radial anisotropy of the second-order cross fiber satisfies: 45%≤(R3-R4) / R3≤85%; where R3 is the circumcircle radius of the second-order cross fiber and R4 is the incircle radius of the second-order cross fiber.

[0010] In some embodiments, the monofilament fineness of the second-order cross-fiber is 0.8-5.6 dtex; the polymer is polyester.

[0011] According to a second aspect of the present invention, a method for preparing the above-mentioned second-order cross fiber is provided, comprising: 1) drying polymer raw materials; 2) melt extrusion and forming nascent fibers with a fractal cross structure through a spinneret; 3) after the nascent fibers are extruded from the spinneret, they enter a cooling zone for cooling; and 4) obtaining finished fibers by oiling, winding and stretching.

[0012] In some embodiments, the blowing cooling zone includes, in sequence along the fiber spinning direction: a slow cooling zone, in which no blowing occurs; a first blowing zone, in which the blowing method is circumferential blowing; and a second blowing zone, in which the blowing method is longitudinal blowing.

[0013] In some embodiments, the length of the slow cooling zone does not exceed 80 mm, the length of the first air blowing zone is 50-270 mm, and the length of the second air blowing zone is 50-300 mm.

[0014] In some embodiments, the air pressure in the first air blowing zone is 20-100 Pa and the air temperature is 25-80°C; the air pressure in the second air blowing zone is 20-80 Pa and the air temperature is 25-60°C.

[0015] According to a third aspect of the invention, a textile is provided that uses the second-order cross-fibers described in any of the preceding claims.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: 1. By constructing a multi-level cross-sectional shape consisting of a primary cross-shaped trunk structure and a secondary cross-shaped branch structure, the fiber achieves a differentiated stiffness distribution in the radial direction. The primary cross-shaped trunk structure provides the main mechanical support, giving the fiber high structural stiffness; the secondary cross-shaped branch structures are smaller in size and distributed on the outer region of the fiber, thereby reducing surface stiffness and maintaining good flexibility on the fiber exterior.

[0017] 2. By setting a secondary cross-branch structure at the end of the primary cross-shaped trunk structure, a complex contour composed of secondary cross-branch structures is formed on the outer periphery of the fiber, which acts as a groove, increases the surface roughness and capillary effect, thereby promoting the directional transport of liquid and improving the moisture absorption and perspiration performance of the fiber.

[0018] 3. To address the issue of collapse or deformation of multi-level fractal structures during spinning, a multi-stage air-blowing cooling process is employed. This process consists of a "slow cooling zone – annular blowing zone – forward blowing zone," with a forward blowing airflow downstream along the fiber spinning direction. The annular blowing zone provides uniform radial cooling, allowing the nascent fiber to rapidly increase melt viscosity under high air pressure and suitable temperature, thus achieving rapid shaping of the irregular cross-section. The forward blowing zone's airflow direction is essentially consistent with the fiber's running direction, significantly reducing lateral airflow disturbance and ensuring more uniform stress on the fiber during cooling. This reduces the displacement, collapse, and distortion of fine structures such as secondary cross branches.

[0019] 4. By rationally designing the dimensional proportions (such as leaf length ratio and leaf width ratio) and relative radial irregularity of the second-order cross structure, a good balance is achieved between the fiber's structural stiffness, softness, and moisture absorption and wicking performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the second-order cross-fiber cross section of the present invention; Figure 2 This is a diagram illustrating the air blowing method; Figure 3 This is a microscope image of the second-order cross-fiber cross section of the present invention; Figure 4 This is a schematic diagram of the air-blowing cooling area of ​​the present invention; Figure 5 This is a schematic diagram of dynamic contact angle test results for some embodiments and comparative examples of the present invention. Detailed Implementation

[0021] Embodiments of the invention will now be described more fully with reference to the accompanying drawings, in which embodiments of the invention are illustrated. However, the invention may be practiced in many different forms, and should not be construed as limited to the embodiments set forth herein.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “this” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that, when used herein, the term “comprising” specifies the presence of the stated features, integrals, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof.

[0023] Unless otherwise defined, the terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms used herein shall be interpreted as having the same meaning as they have in the context of this specification and in the relevant field, and shall not be interpreted in an idealized or overly formal sense, unless specifically defined herein.

[0024] To address the issue that existing technologies for this type of structure typically focus on optimizing a single performance, such as improving moisture absorption and wicking capacity or adjusting gloss effects, while lacking effective control over structural stiffness distribution.

[0025] This invention provides a second-order cross-shaped fiber with a special cross-sectional shape. The cross-sectional structure of the second-order cross-shaped fiber can be understood as a recursively generated multi-level structure, which uses a basic cross structure as the initial structure and forms smaller branch structures at the ends of the basic cross structure, thereby constituting a second-order cross shape.

[0026] Specifically, the fiber cross-section extends from its geometric center in four directions (up, down, left, and right) to form a primary cross-shaped backbone structure. This primary cross-shaped backbone structure constitutes the main skeleton of the fiber cross-section and provides the positioning basis for the subsequent generation of secondary structures. At the four ends of the primary cross-shaped backbone structure, secondary cross-shaped branch structures with dimensions smaller than those of the primary cross-shaped backbone structure are respectively set.

[0027] Each of the secondary cross-branch structures comprises four extending directions. One pair of opposing extending directions is the same as and collinear with the corresponding direction of the primary cross-trunk structure; another pair of opposing extending directions is the same as and parallel to another pair of directions of the primary cross-trunk structure. Thus, the primary cross-trunk structure and the secondary cross-branch structures maintain consistency in their directional system and form a symmetrical and continuous second-order cross-section structure in spatial distribution.

[0028] Through the above structural design, the fiber cross-section differs from simple cross-sections such as circles, triangles, or ordinary crosses, instead forming an irregular cross-section with multi-level branching characteristics. On the one hand, the primary cross-shaped trunk structure provides internal support for the fiber; on the other hand, the secondary cross-shaped branching structure increases the complexity of the fiber's outer contour, creating capillary channels on the fiber surface that facilitate liquid spreading and conduction. This results in the fiber possessing both "rigid inside and flexible outside" mechanical properties and good moisture absorption and wicking performance.

[0029] In this invention, leaf length refers to the radial distance from the center of the cross structure to the corresponding end; leaf width refers to the width of the cross structure when it is spread laterally in the corresponding direction, that is, the dimension perpendicular to the leaf length direction. For a primary cross trunk structure, its leaf length and leaf width are denoted as the large leaf length and the large leaf width, respectively; for a secondary cross branch structure, its leaf length and leaf width are denoted as the small leaf length and the small leaf width, respectively.

[0030] Preferably, the ratio of the leaf length of the primary cross-branch structure to the leaf length of the secondary cross-branch structure is 1 to 4; the ratio of the leaf width of the primary cross-branch structure to the leaf width of the secondary cross-branch structure is 1 to 2. These proportional relationships define the relative dimensional relationship between the primary cross-branch structure and the secondary cross-branch structure, achieving a better balance between internal support, external softness, and moisture-wicking properties of the fiber.

[0031] like Figure 1 As shown, the relative radial anisotropy of the second-order cross fiber satisfies: 45% ≤ (R3 - R4) / R3 ≤ 85%. Where: R3 is the circumcircle radius of the fiber cross-section; R4 is the incircle radius of the fiber cross-section. The circumcircle is the smallest circle that completely encloses the outer contour of the fiber cross-section, and its center coincides with the geometric center of the fiber cross-section. The circumcircle radius R3 is the maximum distance from the center of this circle to the outermost edge of the fiber cross-section. The incircle is the largest circle with the geometric center of the fiber cross-section as its center that completely lies within the outer contour of the fiber cross-section. The incircle radius R4 is the minimum distance from the geometric center to the boundary of the fiber cross-section.

[0032] When the relative radial anisotropy is small, the fiber cross-section tends to be circular, and the surface structure features are not obvious, which is not conducive to the formation of capillary channels. When the relative radial anisotropy is too large, the external protrusions of the fiber are too prominent, and deformation is likely to occur during spinning, drawing, or subsequent processing. Therefore, controlling the relative radial anisotropy within the above range is beneficial to balancing the stability of the fiber cross-sectional structure and its moisture absorption and wicking properties.

[0033] In this invention, the preferred monofilament fineness of the second-order cross-fiber is 0.8–5.6 dtex. When the monofilament fineness is less than 0.8 dtex, the fiber's bending resilience decreases, easily affecting the fabric's elasticity. Furthermore, excessively fine fibers are prone to insufficient color development or pilling during dyeing and subsequent processing. When the monofilament fineness is greater than 5.6 dtex, the fiber's bending stiffness increases, making the hand feel stiffer and reducing wicking performance. Therefore, the above-mentioned monofilament fineness range is beneficial for balancing fiber hand feel, elasticity, and moisture-wicking properties.

[0034] The present invention also provides a method for preparing the above-mentioned second-order cross-shaped fiber, comprising: drying the polymer raw material; melting and extruding the dried polymer raw material and forming a nascent fiber with a second-order cross-section structure through a spinneret; cooling the nascent fiber in a blowing cooling zone; and obtaining the finished fiber after oiling, winding and stretching.

[0035] The blowing cooling zone, along the fiber spinning direction, sequentially includes a slow cooling zone, a first blowing zone, and a second blowing zone. The slow cooling zone does not experience blowing; the first blowing zone uses a circular blowing method; and the second blowing zone uses a forward blowing method. Figure 2 As shown, a represents side-blowing air, b represents circumferential airflow, and c represents forward-blowing airflow.

[0036] The slow cooling zone is used to gradually cool the nascent fibers after they leave the spinneret, preventing instability in the cross-sectional structure due to sudden cooling. The first air blowing zone uses a circumferential air blowing method, which allows the fibers to achieve more uniform cooling in the circumferential direction, thereby increasing the melt viscosity and stabilizing the initial formation of the second-order cross-section structure. The second air blowing zone uses a forward air blowing method, with the airflow direction basically consistent with the fiber running direction, which can reduce the disturbance of the transverse airflow on the fiber cross-section and make the fiber more uniformly stressed during the cooling process.

[0037] For the second-order cross structure described in this invention, the outer secondary cross branch structure is relatively small and is easily affected by lateral airflow during cooling, leading to displacement, collapse, or distortion. By adopting a forward airflow method in the rear section, lateral disturbance can be reduced, the holding capacity of the secondary cross branch structure can be improved, thereby enhancing the forming stability of the complex cross-section structure.

[0038] Preferably, the length of the slow cooling zone does not exceed 80 mm; the length of the first air blowing zone is 50–270 mm; the length of the second air blowing zone is 50–300 mm; and the air pressure in the first air blowing zone is 20–100 Pa, and the air temperature is 25–80℃; the air pressure in the second air blowing zone is 20–80 Pa, and the air temperature is 25–60℃. By setting these parameters, gradient control of "rapid shaping + uniform cooling" is achieved, thereby improving the stability of complex cross-sectional structures.

[0039] The fibers described in this invention can be prepared using conventional spinnable polymers, including but not limited to polyester polymers, polyamide polymers, and other thermoplastic polymers suitable for melt spinning or solution spinning. The type of material is not a particular limitation of this invention. In actual production, considering the wide availability of raw materials, mature spinning processes, stable mechanical properties, and a good foundation for industrial application, the polymer is preferably a polyester polymer, and more preferably polyethylene terephthalate (PET).

[0040] Example The present invention will be further illustrated below through specific embodiments. It should be noted that, unless otherwise specified, the methods used in this embodiment are conventional methods in the art.

[0041] (1) Moisture absorption and perspiration performance test The dynamic contact angles of fibers with different cross-sectional shapes were tested using an optical contact angle meter.

[0042] The moisture wicking capacity of fibers is evaluated by the moisture wicking rating: A: less than 70, B: 70-75, C: 75-80, D: 80-85, E: greater than 85 (advance contact angle °).

[0043] (2) Section parameters The fiber cross-section was observed using a Keyence (China) Co., Ltd. VHX-X1F ultra-depth-of-field optical microscope. Based on the captured images, [the following is a description of the process, not a direct translation]: Figure 1 The positional parameters shown are measured, including: The circumcircle radius of the fiber cross section is R3; the incircle radius of the fiber cross section is R4; the length of the "large cross" blade is R2, and the length of the "small cross" blade is R1. The width of the "large cross" blade is W2, and the width of the "small cross" blade is W1.

[0044] Because there will be shape deviations between the designed fiber and the actual spun fiber, the corresponding dimensions will differ during actual measurement, such as... Figure 3 As shown (3) Stiffness Stiffness calculation formula:

[0045] Where W is the leaf width and R is the leaf length. The ratio of internal to external stiffness can be calculated using this formula: .

[0046] Internal stiffness ratio A (5-25), B (1-5, 25-80), C (0-1, 80 and above).

[0047] Example 1 Polyethylene terephthalate (PET) chips with an intrinsic viscosity of 0.68±0.010 dL / g and a corresponding melt flow rate of 9.6 g / 10 min (260 ℃ / 2.16 kg) were selected as the spinning raw material (supplier: Suzhou Hengli Petrochemical Co., Ltd., China).

[0048] Place the PET chips in a dryer and dry them at 90℃ for 2 hours, 110℃ for 2 hours, 130℃ for 2 hours, and then at 160℃ for 4-6 hours to complete the pre-crystallization and drying of the PET chips.

[0049] The PET chips are conveyed by a screw and heated and melted in zones 1-6, then discharged at a speed of 18.48 cm. 3 A pump feed rate of / min flows into the spinning assembly, and after extrusion through the spinneret, it undergoes air cooling, successively passing through a slow cooling zone, an annular blowing zone (first blowing zone), and a forward blowing zone (second blowing zone), such as... Figure 4 As shown.

[0050] The cooled nascent fibers are treated with spinning oil and then wound at a spinning speed of 2800 m / min to obtain pre-oriented POY yarn. After a post-drawing process, fibers of the target specification are obtained. Specific spinning process parameters are shown in Tables 1 and 2.

[0051] Table 1:

[0052] Comparative Examples 1-3 The specific process of air blowing and cooling was adjusted, and the spinning was carried out in accordance with the method of Example 1. The specific air blowing process and spinning results are shown in Table 2.

[0053] Table 2

[0054] As shown in Table 2, the multi-stage blowing process described in this invention can improve the retention of the fiber cross-sectional structure and enable the fiber to achieve a higher degree of irregularity. For fine denier fibers with high irregularity and small monofilament fineness, as well as complex multi-level cross-section fibers with fractal characteristics, traditional single blowing methods cannot simultaneously meet the requirements of "rapid shaping" and "uniform slow cooling": if the blowing intensity is too high, it is easy to cause deformation of the fine cross-sectional structure; if the blowing intensity is insufficient, it is difficult to stabilize the irregular cross-sectional shape in time.

[0055] This invention employs a multi-stage blowing process to progressively cool and control the nascent fibers. The initial blowing stage increases melt viscosity and initially stabilizes the irregular cross-section, while the subsequent blowing stage further cools and sets the fiber. In particular, when the second stage uses a forward blowing method along the fiber spinning direction, it reduces the disturbance of fine structures such as the secondary cross-branch structure by the transverse airflow, further reducing the degree of fiber cross-section deformation and making the irregularity value more stable.

[0056] Examples 2-7 By changing the spinneret structure, fiber samples with the cross-sectional parameters shown in Table 3 were obtained. All other spinning processes and weaving methods were performed according to Example 1. The moisture absorption and wicking properties and the ratio of internal to external stiffness of the obtained fibers were tested, and the results are listed in Table 3.

[0057] Comparative Examples 4-8 By changing the spinneret, fiber samples with the cross-sectional parameters shown in Table 3 were obtained, while the remaining process conditions remained the same as in Example 1. The moisture absorption and wicking properties and the ratio of internal to external stiffness of the obtained fibers were tested, and the results are listed in Table 3.

[0058] Table 3

[0059] In this invention, the monofilament fineness of the second-order cross-fiber is 0.8–5.6 dtex. When the monofilament fineness is less than 0.8 dtex, the bending resilience is significantly reduced, and the fiber easily loses its elasticity; moreover, excessively fine fibers have poor color development during dyeing and are prone to producing fuzz during processing. When the monofilament fineness is greater than 5.6 dtex, the bending stiffness is too high, the fiber feels stiff, and the wicking effect is poor. As shown in Comparative Example 8, the sample with a larger monofilament fineness has reduced moisture wicking performance. Therefore, controlling the monofilament fineness within the above range is beneficial for achieving a balance between resilience, feel, and wicking performance.

[0060] The ratio of leaf length of the primary cross-branch structure to leaf length of the secondary cross-branch structure (R2:R1) is 1–4; the ratio of leaf width of the primary cross-branch structure to leaf width of the secondary cross-branch structure (W2:W1) is 1–2. These dimensional ratios collectively define the relative dimensional relationship between the primary cross-branch structure and the secondary cross-branch structure, enabling the fiber to achieve a good balance between internal support, external softness, and moisture-wicking properties.

[0061] When the leaf length ratio is too small, as shown in Comparative Example 6, the secondary cross-branching structure is too large relative to the primary cross-trunk structure, and the proportion of the outer branching structure of the fiber is too high, which easily weakens the supporting role of the primary cross-trunk structure and makes the fiber stiffness ratio between the inner and outer sides unsatisfactory; at the same time, it is difficult to form an effective multi-level capillary channel, resulting in a decrease in moisture absorption and perspiration performance.

[0062] When the ratio of leaf length to stem length is too large, as shown in Comparative Example 7, the secondary cross-branch structure is too small relative to the primary cross-stem structure, resulting in insufficient refinement of the fiber surface, weakened capillary action, and reduced ability of liquid to spread and conduct on the fiber surface. At the same time, the insufficient external flexible area is also not conducive to forming a reasonable difference in internal and external stiffness.

[0063] Therefore, controlling R2:R1 within the range of 1 to 4 is beneficial to balancing structural support and surface function.

[0064] By rationally controlling the leaf width ratio, the width relationship between the primary cross trunk structure and the secondary cross branch structure can be adjusted, thereby taking into account the structural strength, external softness, and moisture absorption and perspiration performance of the fiber.

[0065] When the leaf width ratio is too small, as shown in Comparative Example 6, the secondary cross-branch structure is too wide relative to the primary cross-trunk structure, which easily makes the outer structure stiffer, weakens the softness of the fiber surface, and is not conducive to the formation of suitable capillary channels, resulting in poor moisture absorption and perspiration performance and poor internal and external stiffness ratio.

[0066] When the leaf width ratio is too large, as shown in Comparative Example 7, the secondary cross branch structure is too narrow relative to the primary cross trunk structure, the outer structure is not strong enough, and it is easy to deform during spinning, drawing or subsequent processing. In addition, the surface has insufficient effective moisture-wicking structure, so its moisture absorption and perspiration performance and the ratio of internal and external stiffness are also poor.

[0067] Therefore, controlling the W2:W1 ratio within the range of 1 to 2 is beneficial for achieving a balance between structural stability, softness, and moisture-wicking performance.

[0068] For the moisture-wicking performance test, the specific test results are as follows: Figure 5 As shown. Among them, the second-order cross-shaped fiber of Example 1 has the lowest advancing contact angle (77.0°), exhibiting the best water spreading ability and surface hydrophilicity; this value is significantly lower than that of the circular cross-section fiber (80.6°) and the triangular cross-section fiber (85.4°). Circular and triangular cross-section fibers, due to their smooth surfaces and lack of capillary grooves, exhibit poor wetting properties. The second-order cross-shaped fiber, through its multi-grooved surface structure, increases surface roughness and capillary effect, thereby promoting the directional transport of liquids.

[0069] In summary, this invention achieves structural hierarchy and functional synergy of fibers in the radial direction by constructing a second-order cross-section morphology composed of a primary cross-shaped trunk structure and a secondary cross-shaped branch structure. On the one hand, the primary cross-shaped trunk structure provides stable internal support, giving the fiber good mechanical properties; on the other hand, the secondary cross-shaped branch structure refines the fiber's outer contour, forming multi-level capillary channels on the fiber surface, thereby improving the spread and conduction of liquids and achieving excellent moisture absorption and wicking performance.

[0070] Furthermore, this invention combines a multi-stage blowing process and a forward blowing method to achieve gradient control of the cooling process of fibers with complex cross-sections, effectively reducing transverse airflow disturbance, improving the ability to retain fine structures such as secondary cross branches, thereby ensuring the stable forming of highly irregular structures and improving the stability of subsequent drawing and winding processes.

[0071] Therefore, the present invention has made improvements in cross-sectional structure design and forming process, which improves the structural stability and moisture absorption and wicking performance of the resulting fibers.

[0072] The embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions disclosed herein based on the above description.

[0073] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

[0074] This invention is a research result of a National Science and Technology Major Project, Project No. 2025ZD1606405.

Claims

1. A second-order cross-fiber, characterized in that, The fibers are formed from polymers; The cross-section of the fiber has a multi-level cross-shaped structure, wherein: A primary cross-shaped trunk structure is formed with the center of the cross section as the origin; A secondary cross-branch structure is provided at each of the four ends of the primary cross-shaped trunk structure. The size of the secondary cross branch structure is less than or equal to that of the primary cross trunk structure.

2. The second-order cross-fiber according to claim 1, characterized in that, For each of the secondary cross-branch structures, among its four extension directions, one pair of opposite extension directions are the same as and collinear with the corresponding direction of the primary cross-trunk structure, and the other pair of opposite extension directions are the same as and parallel to another pair of directions of the primary cross-trunk structure.

3. The second-order cross-fiber according to claim 1, characterized in that, The ratio of the leaf length of the primary cross-shaped trunk structure to the leaf length of the secondary cross-shaped branch structure is 1 to 4. The ratio of the leaf width of the primary cross-shaped trunk structure to the leaf width of the secondary cross-shaped branch structure is 1 to 2.

4. The second-order cross-fiber according to claim 1, characterized in that, The relative radial anisotropy of the second-order cross fibers satisfies: 45%≤(R3-R4) / R3≤85%; Wherein, R3 is the circumcircle radius of the second-order cross fiber, and R4 is the incircle radius of the second-order cross fiber.

5. The second-order cross-fiber according to claim 1, characterized in that, The single filament fineness of the second-order cross-fiber is 0.8-5.6 dtex; The polymer is polyester.

6. A method for preparing the second-order cross-fiber according to any one of claims 1-5, characterized in that, include: 1) Dry the polymer raw materials; 2) The nascent fibers with a fractal cross structure are formed by melt extrusion and spinneret. 3) After the nascent fibers are extruded from the spinneret, they enter the air-cooling zone for cooling; 4) The finished fiber is obtained by oiling, winding and stretching.

7. The method for preparing second-order cross-fibers according to claim 6, characterized in that, The air-blowing cooling zone includes, sequentially along the fiber spinning direction, the following: The slow-cooling zone will not be exposed to drafts. The first air blowing zone uses a circular air blowing method. The second air-blowing area uses a forward airflow method.

8. The method for preparing second-order cross-fibers according to claim 7, characterized in that, The length of the slow cooling zone shall not exceed 80mm. The length of the first air blowing zone is 50-270mm. The length of the second air blowing zone is 50-300mm.

9. The method for preparing second-order cross-fibers according to claim 7, characterized in that, The wind pressure in the first air blowing zone is 20-100 Pa, and the wind temperature is 25-80℃; The air pressure in the second air blowing zone is 20-80 Pa, and the air temperature is 25-60℃.

10. A textile comprising the second-order cross-fiber as described in any one of claims 1-5.

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