Sheath-core composite fiber, method for producing the same, and fabric

Abstract

This invention relates to the field of spinning technology, specifically to a core-sheath composite fiber, its preparation method, and the fabric thereof. A core-sheath composite fiber is characterized by comprising: a sheath layer made of a fiber-forming polymer and uniformly dispersed with reflective nanoparticles, wherein the reflective nanoparticles are at least one selected from TiO2, ZnO, Al2O3, SiO2, BaSO4, and CaCO3; and a core layer made of a fiber-forming polymer and uniformly dispersed with high-entropy lanthanum chromate nanoparticles; the sheath layer encapsulates the core layer, and the refractive index of the core layer is greater than that of the sheath layer. This core-sheath composite fiber not only improves the blocking effect on near-infrared light but also enhances the fiber's mechanical properties and spinning stability.

Description

Technical Field

[0001] This invention relates to the field of spinning technology, specifically to a core-sheath composite fiber, its preparation method, and its fabric. Background Technology

[0002] Near-infrared light constitutes a large proportion of solar radiation. It not only causes fabrics and human skin surfaces to heat up, but also poses potential risks of thermal damage and photoaging to skin tissue. Current technologies use nanoparticles that reflect near-infrared light dispersed within the fabric fibers to block near-infrared light from reaching the skin tissue. However, the effectiveness of existing technologies in blocking near-infrared light is limited, and the mechanical properties and spinning stability of the fibers are reduced. Summary of the Invention

[0003] The purpose of this invention is to improve the above-mentioned defects in the prior art to a certain extent, and to provide a core-sheath composite fiber and a fabric made from the core-sheath composite fiber. Compared with the fibers and fabrics in the prior art, it can not only improve the blocking effect of near-infrared light, but also improve the mechanical properties and spinning stability of the fiber.

[0004] Through continuous observation, analysis, and experimentation, the applicant aims to identify the reasons for the limited effectiveness of fibers in blocking near-infrared light and the resulting decline in the mechanical properties and spinning stability of the fibers in the prior art. The applicant discovered that existing technologies block near-infrared light by reflecting it, preventing the reflected light from penetrating and irradiating skin tissue. Existing technologies achieve near-infrared light reflection by dispersing nanoparticles with near-infrared light-reflecting properties within the fiber; however, the reflectivity of these nanoparticles is limited. Therefore, to achieve a higher reflectivity, a larger amount of these nanoparticles is required, which in turn easily leads to a decrease in the mechanical properties and spinning stability of the fiber. Conversely, to avoid a decline in the mechanical properties and spinning stability, a smaller amount of nanoparticles is needed, resulting in less reflected near-infrared light and a decrease in near-infrared light blocking performance.

[0005] The aforementioned defects in the background technology were first discovered by the applicant. Based on this, and in order to improve upon the defects in the background technology and achieve the purpose of this invention, the applicant adopts the following technical solution to solve the problem: A core-sheath composite fiber includes: a sheath layer made of a fiber-forming polymer and uniformly dispersed with reflective nanoparticles, wherein the reflective nanoparticles are at least one selected from TiO2, ZnO, Al2O3, SiO2, BaSO4, and CaCO3; a core layer made of a fiber-forming polymer and uniformly dispersed with high-entropy lanthanum chromate nanoparticles; wherein the sheath layer encapsulates the core layer, and the refractive index of the core layer is greater than that of the sheath layer.

[0006] Furthermore, the cross-section of the skin layer is circular.

[0007] Furthermore, the core layer has a triangular cross-section.

[0008] Furthermore, the fiber-forming polymer of the skin layer is at least one of polyester, polyamide, polyimide, polypropylene, polyethylene, and polylactic acid; the fiber-forming polymer of the core layer is at least one of polyester, polyamide, polyimide, polypropylene, polyethylene, and polylactic acid.

[0009] Furthermore, the weight of the reflective nanoparticles is 0.5-5 wt% of the weight of the skin layer, and the particle size of the reflective nanoparticles is 100-800 nm; the weight of the high-entropy lanthanum chromate nanoparticles is 6-18 wt% of the weight of the core layer, and the particle size of the high-entropy lanthanum chromate nanoparticles is 20-300 nm.

[0010] Furthermore, the high-entropy lanthanum chromate nanoparticles are perovskite-type high-entropy oxide nanoparticles; the high-entropy lanthanum chromate nanoparticles have LaCrO3 as the main crystal lattice, and at least four heterometals are introduced at their A-sites (La) to form a high-entropy structure; the heterometal elements are at least four of Y, Nd, Gd, Sr, Sm, Ce, Pr, Ca, and Ba.

[0011] Furthermore, the mass ratio of the sheath to the core layer is 30:70-80:20; the thickness of the sheath layer is 5-60% of the radius of the sheath-core composite fiber; and the ratio of the side length of the triangle in the core layer to the diameter of the sheath layer is 1:10-9:10.

[0012] A method for preparing a core-sheath composite fiber, used to prepare the core-sheath composite fiber described in any one of the above claims, characterized by comprising the following steps: S1: A chromium source, a lanthanum source, four or more heterogeneous metal precursors and chelating ligands are added to a compound solvent and mixed uniformly. The mixture is then subjected to high humidity and negative pressure suction under stirring to obtain a lanthanum chromate-based high-entropy composite gel. The lanthanum chromate-based high-entropy composite gel is subjected to a first ball milling to obtain a first gel. S2: The first gel obtained in S1 is dried and then subjected to graded calcination under a protective gas atmosphere to obtain single-crystal high-entropy lanthanum chromate-based powder; the single-crystal high-entropy lanthanum chromate-based powder is subjected to a second ball milling to obtain high-entropy lanthanum chromate nanoparticles. S3: The high-entropy lanthanum chromate nanoparticles obtained in S2 are mixed with the fiber-forming polymer masterbatch of the core layer according to a preset mass ratio and then fed into a twin-screw extruder. The second composite masterbatch is obtained through high-temperature melting, extrusion molding, cooling and shaping, and pelletizing processes. The first composite masterbatch is obtained by mixing the reflective nanoparticles with the fiber-forming polymer masterbatch of the skin layer according to a preset mass ratio and then feeding the mixture into a twin-screw extruder. The first composite masterbatch is obtained through high-temperature melting, extrusion molding, cooling and shaping, and pelletizing processes. S4: After thoroughly drying the second composite masterbatch and the first composite masterbatch obtained in S3, add them to the two feed hoppers of a high-speed melt spinning machine for spinning and drawing. The first composite masterbatch is used as the sheath layer and the second composite masterbatch is used as the core layer to obtain the sheath-core type composite fiber.

[0013] Furthermore, In step S1: four heterogeneous metal precursors are used, and the molar ratio of the chromium source, lanthanum source, and the four heterogeneous metal precursors is 1:0.2:0.2:0.2:0.2:0.2. The molar ratio of the chromium source to the chelating ligand is 1:0.02-0.07. The chelating ligand is at least one of citric acid, acetic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid. The humidity of the high-humidity negative pressure suction environment is 90-99%, and the negative pressure is 0.1-3 MPa. The humidity environment is constructed by a mixed liquid airflow of 65% deionized water and 35% ethanol. The first ball milling is a dry milling of small-diameter zirconium balls, with a milling speed of 300-400 rpm and a milling time of 0.2-4 hours. In S2: the protective gas is high-purity nitrogen, the initial heating rate is controlled at 1-3℃ / min, the subsequent heating rate is controlled at 10-20℃ / min, and the holding time is 5-30min; the second ball mill is a dry milling of large-diameter zirconium balls, the ball milling speed is 200-500 rpm, and the ball milling time is 2-6 hours. In S3: the melt temperature of the twin-screw extrusion is 150-330℃, it is cooled and shaped in a water bath, and pelletized using a pelletizer; In step S4: the first composite masterbatch is introduced into the sheath flow channel of the spinning assembly; the second composite masterbatch is introduced into the core flow channel of the spinning assembly; the spinning assembly includes a sheath discharge channel and a core discharge channel; the spinning process is carried out at a temperature of 250-320℃, a spinning speed of 500-4500 m / min, and a draw ratio of 1-4 times.

[0014] A fabric characterized in that it comprises a core-sheath composite fiber as described in any of the preceding claims.

[0015] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects: The first technical solution involves a core-sheath composite fiber with a core-sheath composite structure, comprising a sheath layer and a core layer, with the sheath layer enclosing the core layer. The sheath layer is made of a fiber-forming polymer, with reflective nanoparticles uniformly dispersed within it. These reflective nanoparticles allow the sheath layer to generate Mie scattering and reflective properties, blocking near-infrared light. The core layer is also made of a fiber-forming polymer, with high-entropy lanthanum chromate nanoparticles uniformly dispersed within it. When sunlight shines on the surface of the core-sheath composite fiber, the reflective nanoparticles in the sheath layer perform Mie scattering and reflection of near-infrared light. Near-infrared light that is not scattered or reflected enters the core-sheath composite fiber and is absorbed by the high-entropy lanthanum chromate nanoparticles within the core layer. This technical solution, through the combined effect of reflection and absorption, compared to existing technologies that only use reflection, can improve the blocking effect of near-infrared light to a certain extent.

[0016] When unabsorbed near-infrared light propagates from the core layer to the skin layer, at the interface between the core and skin layers, some of the near-infrared light is reflected and remains in the core layer, while some is refracted and propagates from the core layer to the skin layer. In this technical solution, the refractive index of the core layer is greater than that of the skin layer. Therefore, when near-infrared light propagates from the core layer to the skin layer, total internal reflection occurs at the interface between the core and skin layers when the incident angle of the near-infrared light is greater than or equal to the critical angle for total internal reflection. All the near-infrared light undergoing total internal reflection remains in the core layer and does not refract into the skin layer. This allows the near-infrared light to be better absorbed by the high-entropy lanthanum chromate nanoparticles, further improving the blocking effect of the core-skin composite fiber on near-infrared light.

[0017] The second technical solution is that the cross-section of the sheath is circular. The sheath gives the outer surface of the core-sheath composite fiber roundness and processability. When the core-sheath composite fiber has high blocking of near-infrared light, it also has high mechanical properties and spinning stability.

[0018] The third technical solution involves a triangular cross-section of the core layer, forming an asymmetric light propagation interface. This increases the total internal reflection and multipath propagation of near-infrared light at the boundary between the core and the cortex, allowing the near-infrared light to be better absorbed by high-entropy lanthanum chromate.

[0019] The fourth technical solution is that the fiber-forming polymers in the sheath and core layers of this solution can give the sheath-core composite fiber a better near-infrared light blocking effect and higher mechanical properties.

[0020] The fifth technical solution involves a cortex containing reflective nanoparticles at a weight of 0.5-5 wt% and a particle size of 100-800 nm. The core layer contains high-entropy lanthanum chromate nanoparticles at a weight of 6-18 wt% and a particle size of 20-300 nm. This solution, by ensuring a relatively high content and size of high-entropy lanthanum chromate nanoparticles in the core layer, and a relatively low content and size of high-reflectivity nanoparticles in the cortex, not only improves the blocking of near-infrared light but also facilitates a refractive index greater than that of the cortex. Furthermore, by encapsulating the core layer with the cortex, the cortex-core composite fiber exhibits higher mechanical properties and spinning stability.

[0021] The sixth technical solution involves high-entropy lanthanum chromate, which exhibits high absorption and blocking effect for near-infrared light with wavelengths of 0.7–2.5 μm, and also possesses tunability for visible light. This tunability is achieved by adjusting the composition, ratio, and crystal structure of different metal elements within the high-entropy lanthanum chromate material system, altering its selective absorption in the 400–700 nm visible light band. This allows the core-sheath composite fiber to exhibit differentiated absorption and reflection of visible light at different wavelengths, thus presenting different colors. Compared to existing technologies that significantly impact fiber color when improving sunlight blocking, this technical solution offers superior color performance.

[0022] The seventh technical solution involves adjusting the mass ratio of the sheath to the core layer, the thickness of the sheath, and the dimensions of the core layer with a triangular cross-section. This allows for the regulation of the solar reflection, near-infrared absorption, total internal reflection at the interface, and mechanical properties of the sheath-core composite fiber. A higher sheath ratio enhances the reflectivity, mechanical properties, and spinning stability of the sheath-core composite fiber. A higher core ratio improves the optical path control of the core layer and the absorption of near-infrared light by the high-entropy lanthanum chromate nanoparticles.

[0023] The eighth technical solution is to prepare high-entropy lanthanum chromate nanoparticles with high absorption of near-infrared light, as well as core-sheath composite fibers with high blocking of near-infrared light.

[0024] The ninth technical solution improves the high blocking effect of core-sheath composite fibers on near-infrared light by further limiting the preparation conditions.

[0025] The tenth technical solution is that the fabric prepared using the above-mentioned core-sheath composite fiber, compared with the fabric of the prior art, can improve the high blocking effect of near-infrared light by having high reflectivity and high absorption of the near-infrared light in sunlight. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments are briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the core-sheath type composite fiber in Example 1.

[0028] Key reference numerals: 1. Core-sheath composite fiber; 2. Sheath; 3. Core. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0031] Unless otherwise expressly defined, in the claims, description, and accompanying drawings of this invention, the use of directional terms such as "center," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," and "counterclockwise" to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of this invention.

[0032] Unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" used in the claims, description and drawings of this invention should be interpreted broadly to refer to any connection in which there is no displacement or relative rotation relationship between the two parties, including non-removable fixed connection, detachable fixed connection, integral connection and fixed connection by other means or components.

[0033] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0034] Example 1 See Figure 1 A core-sheath composite fiber 1 has a core-sheath composite structure, comprising a sheath layer 2 and a core layer 3, with the sheath layer 2 encapsulating the core layer 3. The fiber-forming polymer of the sheath layer 2 is polyester, and the uniformly dispersed reflective nanoparticles in the polyester of the sheath layer 2 are TiO2 nanoparticles with an average particle size of 200 nm, the weight of which is 5 wt% of the weight of the sheath layer. The fiber-forming polymer of the core layer 3 is polyester, and the uniformly dispersed high-entropy lanthanum chromate nanoparticles in the polyester of the core layer 3 are La0.2Y0.2Nd0.2Gd0.2Sr0.2CrO3 high-entropy lanthanum chromate nanoparticles with an average particle size of 120 nm, the weight of which is 10 wt% of the weight of the sheath layer. The refractive index of the core layer 3 is greater than that of the sheath layer 2. The core-sheath composite fiber has a nearly circular sheath cross-section with an outer diameter of 16.0 μm. The core layer is a rounded triangle with a side length of 7.0 μm, and the ratio of the core layer side length to the diameter of the circumcircle of the core-sheath composite fiber is 0.44. The sheath and core layers are continuously distributed along the fiber axis, and the core-sheath interface is stably bonded. The core-sheath composite fiber has a fineness of 75 dtex, a breaking strength of 2.35 cN / dtex, and a breaking elongation of 38%. UV-Vis-NIR spectroscopy testing shows that the core-sheath composite fiber has an average reflectance of 66.5% and a near-infrared blocking rate of 90.8% in the 0.7-2.5 μm near-infrared band. After 1000 cycles of bending, rubbing, or washing, the near-infrared blocking rate is retained at 98.6%, and the breaking strength is retained at 98.1%.

[0035] The preparation method of the core-sheath type composite fiber in this embodiment is as follows: S1. Chromium nitrate, lanthanum nitrate, yttrium nitrate, neodymium nitrate, gadolinium nitrate, and strontium nitrate were added to a compound solvent of deionized water and ethanol in a molar ratio of Cr:La:Y:Nd:Gd:Sr of 1:0.2:0.2:0.2:0.2, with a volume ratio of deionized water to ethanol of 65:35. Citric acid was then added as a chelating ligand, with a molar ratio of chromium source to citric acid of 1:0.05. The mixture was stirred thoroughly at 350 rpm for 4 hours at room temperature. A humidifier consisting of a mixture of 65% deionized water and 35% ethanol was introduced into the reaction system, while a negative pressure was applied to maintain a humidity of 95% and a negative pressure of 1.0 MPa. The reaction was carried out under stirring for 40 minutes to obtain a lanthanum chromate-based high-entropy composite gel. The obtained lanthanum chromate-based high-entropy composite gel was transferred to a ball mill for the first ball milling. Small-diameter zirconium balls were used for dry milling, and the mass ratio of gel to zirconium balls was controlled at 1:80. The ball milling speed was 350 rpm and the ball milling time was 2 hours to obtain the first gel.

[0036] S2. The first gel was thoroughly dried in a vacuum oven at 80℃ for 6 hours. Subsequently, it was subjected to staged calcination under a high-purity nitrogen atmosphere. The initial heating rate was 2℃ / min, reaching 450℃ and holding for 30 minutes to remove solvents, ligands, and organic residues from the first gel. The subsequent heating rate was 15℃ / min, reaching 900℃ and holding for 20 minutes to promote the formation of the perovskite-type high-entropy lanthanum chromate crystal phase, yielding single-crystal high-entropy lanthanum chromate-based powder. After cooling the calcined single-crystal high-entropy lanthanum chromate-based powder to room temperature, it was transferred to a ball mill for a second ball milling. Large-diameter zirconium balls were used for dry milling, controlling the powder-to-zirconium ball mass ratio at 1:120, the milling speed at 400 rpm, and the milling time at 4 hours, yielding La0.2Y0.2Nd0.2Gd0.2Sr0.2CrO3 high-entropy lanthanum chromate nanoparticles. The obtained high-entropy lanthanum chromate nanoparticles have a perovskite oxide structure with an average particle size of 120 nm and a particle size distribution in the range of 20-300 nm.

[0037] S3. The obtained high-entropy lanthanum chromate nanoparticles were dried under vacuum at 100°C for 6 hours, followed by surface treatment with KH570 silane coupling agent, the amount of which was 1.0 wt% of the mass of the high-entropy lanthanum chromate nanoparticles. The surface-treated high-entropy lanthanum chromate nanoparticles were premixed with the core layer fiber-forming polymer masterbatch (polyester masterbatch in this example) at a mass ratio of 10:90, and then added to a twin-screw extruder for melt blending and granulation. The temperatures of the twin-screw extruder were 250°C in zone 1, 265°C in zone 2, 280°C in zone 3, 290°C in zone 4, 300°C in zone 5, 305°C in zone 6, and 305°C in the die head, with a screw speed of 180 rpm. The extruded melt strip was cooled and solidified in a 25°C water bath and then pelletized using a pelletizer to obtain the second composite masterbatch (polyester / high-entropy lanthanum chromate composite masterbatch in this example).

[0038] TiO2 nanoparticles with an average particle size of 200 nm were dried under vacuum at 120 °C for 8 hours. They were then premixed with a skin-forming polymer masterbatch (polyester masterbatch in this example) at a mass ratio of 5:95, and fed into a twin-screw extruder for melt blending and granulation. The twin-screw extruder temperatures were 250 °C in zone 1, 265 °C in zone 2, 280 °C in zone 3, 290 °C in zone 4, 300 °C in zone 5, 305 °C in zone 6, and 305 °C at the die head. The screw speed was 180 rpm. The extruded melt strip was cooled and solidified in a 25 °C water bath and then pelletized using a pelletizer to obtain the first composite masterbatch (polyester / TiO2 composite masterbatch in this example).

[0039] S4. The first and second composite masterbatches are vacuum dried in a rotary drum oven. The drying process is as follows: the first stage heats the masterbatch from room temperature to 80°C over 30 minutes; the second stage heats it from 80°C to 120°C over 30 minutes; and the third stage heats it to 150°C over 1 hour, for a total drying time of 20 hours. The dried first composite masterbatch is loaded into screw assembly A and introduced into the sheath flow channel of the outer / inner rounded corner triangular sheath-core spinneret assembly; the dried second composite masterbatch is loaded into screw assembly B and introduced into the core flow channel. The mass ratio of sheath to core is controlled at 60:40, and the ratio of sheath melt viscosity to core melt viscosity is 1.5:1. The spinning temperature is 280-310°C, the spinning speed is 3000 m / min, the draw ratio is 2.5, the cooling air temperature is 25°C, and the cooling air velocity is 0.5 m / s. The core layer is continuously formed along the fiber axis by the sheath layer under the coating effect, forming a rounded triangular irregular core layer, thus obtaining a sheath-core type composite fiber with an outer circle and inner triangle sheath-core composite structure.

[0040] Example 2 A core-sheath composite fiber has a core-sheath composite structure, comprising a sheath layer and a core layer, with the sheath layer encapsulating the core layer. The fiber-forming polymer of the sheath layer is polyester, and the polyester in the sheath layer contains uniformly dispersed reflective nanoparticles: BaSO4 nanoparticles with an average particle size of 300 nm and ZnO nanoparticles with an average particle size of 100 nm. The weight of the BaSO4 nanoparticles is 3 wt% of the weight of the sheath layer, and the weight of the ZnO nanoparticles is 2 wt% of the weight of the sheath layer. The fiber-forming polymer of the core layer is polyester, and the polyester in the core layer contains uniformly dispersed high-entropy lanthanum chromate nanoparticles: La0.2Sm0.2Ce0.2Pr0.2Ca0.2CrO3 high-entropy lanthanum chromate nanoparticles with an average particle size of 150 nm. The weight of the high-entropy lanthanum chromate nanoparticles is 14 wt% of the weight of the sheath layer. The refractive index of the core layer is greater than that of the sheath layer. The core-sheath composite fiber has a nearly circular sheath cross-section with an outer diameter of 18.0 μm. The core layer is a rounded triangle with a side length of 8.5 μm, and the ratio of the core layer side length to the diameter of the circumcircle of the core-sheath composite fiber is 0.47. The sheath and core layers are continuously distributed along the fiber axis, and the core-sheath interface is stably bonded. The core-sheath composite fiber has a fineness of 110 dtex, a breaking strength of 2.12 cN / dtex, and a breaking elongation of 32%. UV-Vis-NIR spectroscopy testing shows that the core-sheath composite fiber has an average reflectance of 70.2% and a near-infrared blocking rate of 93.6% in the 0.7-2.5 μm near-infrared band. After 1000 cycles of bending, friction, or washing, the near-infrared blocking rate is retained at 98.3%, and the breaking strength is retained at 97.8%.

[0041] The preparation method of the core-sheath type composite fiber in this embodiment is as follows: S1. Chromium nitrate, lanthanum nitrate, samarium nitrate, cerium nitrate, praseodymium nitrate, and calcium nitrate were added to a compound solvent of deionized water and ethanol in a molar ratio of Cr:La:Sm:Ce:Pr:Ca of 1:0.2:0.2:0.2:0.2, with a volume ratio of deionized water to ethanol of 65:35. Ethylenediaminetetraacetic acid (EDTA) was then added as a chelating ligand, with a molar ratio of chromium source to ETA of 1:0.06. The mixture was stirred thoroughly at 380 rpm for 5 hours at room temperature. A humidifier consisting of a mixture of 65% deionized water and 35% ethanol was introduced into the reaction system, while a negative pressure was applied to maintain a humidity of 96% and a negative pressure of 1.5 MPa. The reaction was carried out under stirring for 50 minutes to obtain a lanthanum chromate-based high-entropy composite gel. The obtained lanthanum chromate-based high-entropy composite gel was transferred to a ball mill for the first ball milling. Small-diameter zirconium balls were used for dry milling, and the mass ratio of gel to zirconium balls was controlled at 1:100. The ball milling speed was 380 rpm and the ball milling time was 3 hours to obtain the first gel.

[0042] S2. The first gel was thoroughly dried in a vacuum oven at 90°C for 5 hours. Subsequently, it was subjected to staged calcination under a high-purity nitrogen atmosphere. The initial heating rate was 2°C / min, reaching 450°C and holding for 30 minutes to remove solvents, ligands, and organic residues from the gel. The subsequent heating rate was 12°C / min, reaching 950°C and holding for 25 minutes to promote the formation of the high-entropy lanthanum chromate-based perovskite crystal phase, yielding single-crystal high-entropy lanthanum chromate-based powder. After cooling the calcined single-crystal high-entropy lanthanum chromate-based powder to room temperature, it was transferred to a ball mill for a second ball milling. Large-diameter zirconium balls were used for dry milling, controlling the powder-to-zirconium ball mass ratio at 1:150, the milling speed at 450 rpm, and the milling time at 5 hours, yielding La0.2Sm0.2Ce0.2Pr0.2Ca0.2CrO3 high-entropy lanthanum chromate nanoparticles. The obtained high-entropy lanthanum chromate nanoparticles have a perovskite oxide structure with an average particle size of 150 nm and a particle size distribution in the range of 20-300 nm.

[0043] S3. The obtained high-entropy lanthanum chromate nanoparticles were dried under vacuum at 110℃ for 6 hours, followed by surface treatment with KH560 silane coupling agent. The amount of silane coupling agent was 1.5 wt% of the mass of the high-entropy lanthanum chromate-based nanoparticles. The surface-treated high-entropy lanthanum chromate nanoparticles were premixed with the core layer fiber-forming polymer masterbatch (polyester masterbatch in this example) at a mass ratio of 14:86, and then added to a twin-screw extruder for melt blending and granulation. The temperatures of the twin-screw extruder were 250℃ in zone 1, 265℃ in zone 2, 280℃ in zone 3, 290℃ in zone 4, 305℃ in zone 5, 310℃ in zone 6, and 310℃ at the die head. The screw speed was 200 rpm. The extruded melt strip was cooled and solidified in a 25℃ water bath and then pelletized using a pelletizer to obtain the second composite masterbatch (polyester / high-entropy lanthanum chromate composite masterbatch in this example).

[0044] BaSO4 nanoparticles with an average particle size of 300 nm and ZnO nanoparticles with an average particle size of 100 nm were dried separately under vacuum at 120°C for 8 hours. Then, the BaSO4 nanoparticles, ZnO nanoparticles, and a skin-forming polymer masterbatch (polyester masterbatch in this example) were premixed at a mass ratio of 3:2:95 and fed into a twin-screw extruder for melt blending and granulation. The twin-screw extruder had the following temperatures: Zone 1: 250°C, Zone 2: 265°C, Zone 3: 280°C, Zone 4: 290°C, Zone 5: 305°C, Zone 6: 310°C, Die Head: 310°C, and Screw Speed: 200 rpm. The extruded melt strip was cooled and solidified in a 25°C water bath and then pelletized using a pelletizer to obtain the first composite masterbatch (polyester / BaSO4 / ZnO composite masterbatch in this example).

[0045] S4. The first and second composite masterbatches are vacuum dried in a rotary drum oven. The drying process is as follows: the first stage heats the masterbatch from room temperature to 80°C over 30 minutes; the second stage heats it from 80°C to 120°C over 30 minutes; and the third stage heats it to 150°C over 1 hour, for a total drying time of 20 hours. The dried first composite masterbatch is loaded into screw assembly A and introduced into the sheath flow channel of the outer circular / inner triangular sheath-core spinneret assembly; the dried second composite masterbatch is loaded into screw assembly B and introduced into the core flow channel. The mass ratio of sheath to core is controlled at 50:50, and the ratio of sheath melt viscosity to core melt viscosity is 1.2:1. The spinning temperature is 280-315°C, the spinning speed is 2800 m / min, the draw ratio is 2.2, the cooling air temperature is 22°C, and the cooling air velocity is 0.6 m / s. The core layer is continuously formed along the fiber axis by the sheath layer under the coating effect, forming a rounded triangular irregular core layer, thus obtaining a sheath-core type composite fiber with an outer circle and inner triangle sheath-core composite structure.

[0046] A fabric made from the aforementioned core-sheath composite fiber through weaving and other processes.

[0047] The core-sheath composite fiber in the above embodiments has a core-sheath composite structure, including a sheath layer and a core layer, with the sheath layer enclosing the core layer. The sheath layer is made of a fiber-forming polymer, in which reflective nanoparticles are uniformly dispersed. The reflective nanoparticles in the above embodiments allow the sheath layer to generate Mie scattering and reflective properties, blocking near-infrared light. The core layer is also made of a fiber-forming polymer, in which high-entropy lanthanum chromate nanoparticles are uniformly dispersed. When sunlight shines on the surface of the core-sheath composite fiber, the reflective nanoparticles in the sheath layer perform Mie scattering and reflection of near-infrared light. Near-infrared light that is not scattered or reflected enters the core-sheath composite fiber and is absorbed by the high-entropy lanthanum chromate nanoparticles in the core layer. The above embodiments, through the combined effect of reflection and absorption, compared to existing technologies that only use reflection, can improve the blocking effect of near-infrared light to a certain extent.

[0048] When unabsorbed near-infrared light propagates from the core layer to the skin layer, at the interface between the core and skin layers, some of the near-infrared light is reflected and remains in the core layer, while some is refracted and propagates from the core layer to the skin layer. In the above embodiment, the refractive index of the core layer is greater than that of the skin layer. Therefore, when near-infrared light propagates from the core layer to the skin layer, at the interface between the core and skin layers, total internal reflection occurs when the incident angle of the near-infrared light is greater than the critical angle for total internal reflection. All the near-infrared light that undergoes total internal reflection remains in the core layer and does not refract into the skin layer. This allows the near-infrared light to be better absorbed by the high-entropy lanthanum chromate nanoparticles, further improving the blocking effect of the core-skin composite fiber on near-infrared light.

[0049] In the above embodiments, the cross-section of the sheath is circular. The sheath gives the outer surface of the core-sheath composite fiber roundness and processability. When the core-sheath composite fiber has high blocking of near-infrared light, it also has high mechanical properties and spinning stability.

[0050] In the above embodiments, the cross-section of the core layer is triangular, forming an asymmetric light propagation interface, which increases the total internal reflection and multipath propagation of near-infrared light at the boundary between the core layer and the skin layer, allowing the near-infrared light to be better absorbed by high-entropy lanthanum chromate.

[0051] The fiber-forming polymers of the sheath and core layers in the above embodiments enable the sheath-core composite fiber to have good near-infrared light blocking effect and high mechanical properties.

[0052] In the above embodiments, the reflective nanoparticles in the outer layer weigh 0.5-5 wt% of the outer layer weight and have a particle size of 100-800 nm. The high-entropy lanthanum chromate nanoparticles in the core layer weigh 6-18 wt% of the core layer weight and have a particle size of 20-300 nm. By ensuring a relatively high content and particle size of high-entropy lanthanum chromate nanoparticles in the core layer and a relatively low content and particle size of high-reflectivity nanoparticles in the outer layer, the blocking of near-infrared light can be improved, and it is also beneficial to form a core layer with a higher refractive index than the outer layer. Furthermore, by encapsulating the core layer with the outer layer, the core-sheath composite fiber possesses higher mechanical properties and spinning stability.

[0053] The high-entropy lanthanum chromate in the above embodiments exhibits high absorption and high blocking effect for near-infrared light with wavelengths of 0.7–2.5 μm, and also possesses tunability for visible light. This tunability is achieved by adjusting the composition, ratio, and crystal structure of different metal elements within the high-entropy lanthanum chromate material system, thereby altering its selective absorption in the 400–700 nm visible light band. This allows the core-sheath composite fiber to exhibit differentiated absorption and reflection of visible light at different wavelengths, resulting in different colors. Compared to existing technologies that significantly affect fiber color when improving sunlight blocking, the above embodiments provide superior color performance.

[0054] The above embodiments allow for the adjustment of the solar reflection, near-infrared absorption, interfacial total internal reflection, and mechanical properties of the core-sheath composite fiber by controlling the mass ratio of the sheath to the core, the thickness of the sheath, and the dimensions of the core with a triangular cross-section. A higher sheath ratio improves the reflectivity, mechanical properties, and spinning stability of the core-sheath composite fiber. A higher core ratio enhances the optical path control of the core and the absorption of near-infrared light by the high-entropy lanthanum chromate nanoparticles.

[0055] In the above embodiments, high-entropy lanthanum chromate nanoparticles with high absorption of near-infrared light and core-sheath composite fibers with high blocking of near-infrared light can be prepared.

[0056] In the above embodiments, the high blocking effect of the core-sheath composite fiber on near-infrared light is improved by further limiting the preparation conditions.

[0057] In the above embodiments, the fabric prepared using the above-mentioned core-sheath composite fiber, compared with the fabric of the prior art, can improve the high blocking effect of near-infrared light by having high reflectivity and high absorption of the near-infrared light in sunlight.

[0058] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be made by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common general knowledge, ordinary technical knowledge in the art, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A core-sheath composite fiber characterized by, include: The skin layer is made of a fiber-forming polymer and uniformly dispersed with reflective nanoparticles, wherein the reflective nanoparticles are at least one of TiO2, ZnO, Al2O3, SiO2, BaSO4, and CaCO3; The core layer is made of a fiber-forming polymer and uniformly dispersed with high-entropy lanthanum chromate nanoparticles. The skin layer encloses the core layer, and the refractive index of the core layer is greater than that of the skin layer.

2. The sheath-core type composite fiber according to Claim 1, wherein the sheath component is a polyester resin. The cross-section of the skin layer is circular.

3. The sheath-core type composite fiber according to Claim 2, wherein the sheath is composed of a polymer having a glass transition temperature of 40°C or higher and 80°C or lower. The core layer has a triangular cross-section.

4. The core-sheath composite fiber as described in claim 3, characterized in that, The fiber-forming polymer of the outer layer is at least one of polyester, polyamide, polyimide, polypropylene, polyethylene, and polylactic acid; the fiber-forming polymer of the core layer is at least one of polyester, polyamide, polyimide, polypropylene, polyethylene, and polylactic acid.

5. The core-sheath composite fiber as described in claim 4, characterized in that, The weight of the reflective nanoparticles is 0.5-5 wt% of the weight of the skin layer, and the particle size of the reflective nanoparticles is 100-800 nm; the weight of the high-entropy lanthanum chromate nanoparticles is 6-18 wt% of the weight of the core layer, and the particle size of the high-entropy lanthanum chromate nanoparticles is 20-300 nm.

6. The core-sheath composite fiber as described in claim 5, characterized in that, The high-entropy lanthanum chromate nanoparticles are perovskite-type high-entropy oxide nanoparticles; the high-entropy lanthanum chromate nanoparticles have LaCrO3 as the main crystal lattice, and at least four heterometals are introduced at their A sites (La) to form a high-entropy structure; the heterometal elements are at least four of Y, Nd, Gd, Sr, Sm, Ce, Pr, Ca, and Ba.

7. The core-sheath composite fiber as described in claim 6, characterized in that, The mass ratio of the sheath to the core is 30:70-80:20; the thickness of the sheath is 5-60% of the radius of the sheath-core composite fiber; and the ratio of the side length of the triangle in the core to the diameter of the sheath is 1:10-9:

10.

8. A method for preparing a core-sheath composite fiber, used to prepare the core-sheath composite fiber according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: A chromium source, a lanthanum source, four or more heterogeneous metal precursors and chelating ligands are added to a compound solvent and mixed uniformly. The mixture is then subjected to high humidity and negative pressure suction under stirring to obtain a lanthanum chromate-based high-entropy composite gel. The lanthanum chromate-based high-entropy composite gel is subjected to a first ball milling to obtain a first gel. S2: The first gel obtained in S1 is dried and then subjected to graded calcination under a protective gas atmosphere to obtain single-crystal high-entropy lanthanum chromate-based powder; the single-crystal high-entropy lanthanum chromate-based powder is subjected to a second ball milling to obtain high-entropy lanthanum chromate nanoparticles. S3: The high-entropy lanthanum chromate nanoparticles obtained in S2 are mixed with the fiber-forming polymer masterbatch of the core layer according to a preset mass ratio and then fed into a twin-screw extruder. The second composite masterbatch is obtained through high-temperature melting, extrusion molding, cooling and shaping, and pelletizing processes. The first composite masterbatch is obtained by mixing the reflective nanoparticles with the fiber-forming polymer masterbatch of the skin layer according to a preset mass ratio and then feeding the mixture into a twin-screw extruder. The first composite masterbatch is obtained through high-temperature melting, extrusion molding, cooling and shaping, and pelletizing processes. S4: After thoroughly drying the second composite masterbatch and the first composite masterbatch obtained in S3, add them to the two feed hoppers of a high-speed melt spinning machine for spinning and drawing. The first composite masterbatch is used as the sheath layer and the second composite masterbatch is used as the core layer to obtain the sheath-core type composite fiber.

9. The method for preparing a core-sheath composite fiber as described in claim 8, characterized in that, In step S1: four heterogeneous metal precursors are used. The molar ratio of the chromium source, lanthanum source, and the four heterogeneous metal precursors is 1:0.2:0.2:0.2:0.2:0.

2. The molar ratio of the chromium source to the chelating ligand is 1:0.02-0.

07. The chelating ligand is at least one of citric acid, acetic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid. The humidity of the high-humidity negative pressure suction environment is 90-99%, and the negative pressure is 0.1-3 MPa. The humidity environment is constructed by a mixed liquid gas flow of 65% deionized water and 35% ethanol. The first ball milling is a dry milling of small-diameter zirconium balls at a milling speed of 300-400 rpm for a milling time of 0.2-4 hours. In step S2: the protective gas is high-purity nitrogen, and the initial heating rate is... The temperature is controlled at 1-3℃ / min, the subsequent heating rate is controlled at 10-20℃ / min, and the holding time is 5-30min; the second ball mill is a dry milling of large-diameter zirconium balls, the ball milling speed is 200-500 rpm, and the ball milling time is 2-6 hours; in S3: the melting temperature of the twin-screw extrusion is 150-330℃, it is cooled and shaped in a water bath, and pelletized using a pelletizer; in S4: the first composite masterbatch is introduced into the skin layer channel of the spinning assembly; the second composite masterbatch is introduced into the core layer channel of the spinning assembly; the spinning assembly includes a skin layer discharge channel and a core layer discharge channel; the temperature in the spinning process is 250-320℃, the spinning speed is 500-4500 m / min, and the draw ratio is 1-4 times.

10. A fabric characterized in that, It includes a core-sheath composite fiber as described in any one of claims 1 to 7.

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