Preparation method of composite fiber and fabric with sunlight barrier property

Abstract

The invention provides a preparation method of a composite fiber and a fabric with sunlight barrier performance. The preparation method of the composite fiber comprises the following steps: S10, respectively preparing a skin layer melt and a core layer melt; the skin layer melt comprises a thermoplastic polymer matrix and titanium dioxide particles; the core layer melt comprises a thermoplastic polymer matrix, titanium dioxide particles and cesium tungsten bronze nanoparticles; s20, the skin layer melt and the core layer melt are introduced into a composite spinning assembly, the skin layer melt is controlled to wrap the core layer melt to form skin-core type composite fluid, and the skin-core type composite fluid is extruded through a spinneret plate with triangular holes; and S30, carrying out cross air blowing cooling, drafting and winding on the extruded fluid to obtain the sheath-core type composite fiber with a triangular cross section outer contour. The composite fiber can keep good spinnability and hand feeling, can block sunlight and heat at the same time, and provides better wearing comfort.

Description

Technical Field

[0001] This invention relates to the field of composite fiber technology, specifically to a method for preparing composite fibers and fabrics with sunlight blocking properties. Background Technology

[0002] As consumers increasingly demand functionality in summer outdoor clothing, sun protection and cooling sensation have become crucial indicators for summer fabrics. The energy distribution in sunlight primarily consists of ultraviolet (approximately 5%), visible light (approximately 45%), and infrared (approximately 50%). Ultraviolet radiation mainly causes sunburn and aging, while near-infrared radiation is the primary source of heat, causing a burning sensation after penetrating clothing. Currently, the fibers used in clothing, while maintaining good spinnability and hand feel, struggle to simultaneously provide adequate light and heat insulation. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects or problems in the prior art and to provide a method for preparing composite fibers and fabrics with sunlight blocking properties. The composite fibers can block sunlight and heat while maintaining good spinnability and hand feel, thus providing better wearing comfort.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: Technical Solution 1: A method for preparing a composite fiber with solar light blocking properties, comprising the following steps: S10: preparing a skin melt and a core melt separately; the skin melt comprises a thermoplastic polymer matrix and titanium dioxide particles; the core melt comprises a thermoplastic polymer matrix, titanium dioxide particles, and cesium tungsten bronze nanoparticles; S20: introducing the skin melt and the core melt into a composite spinning assembly, controlling the skin melt to wrap the core melt to form a skin-core composite fluid, and extruding it through a spinneret with triangular holes; S30: subjecting the extruded fluid to side-blowing cooling, stretching, and winding to obtain a skin-core composite fiber with a triangular cross-sectional outer contour.

[0005] Technical Solution 2 based on Technical Solution 1: In step S10, the preparation process of the core layer melt includes: drying nano-titanium dioxide powder and cesium tungsten bronze powder at 110°C to 120°C; placing the dried powder, dispersant, and thermoplastic polymer chips into a high-speed mixer and mixing them at a speed of 500 rpm to 1000 rpm; extruding and granulating the mixed material through a twin-screw extruder to obtain a core layer functional masterbatch, and then melting the core layer functional masterbatch to obtain the core layer melt.

[0006] Technical Solution 3 based on Technical Solution 1: In step S10: the thermoplastic polymer matrix used in the skin melt is polyester with an intrinsic viscosity of 0.64 dL / g to 0.66 dL / g; the thermoplastic polymer matrix used in the core melt is polyester with an intrinsic viscosity of 0.58 dL / g to 0.62 dL / g.

[0007] Technical Solution 4 based on Technical Solution 1: In steps S10 and S20: In the core melt, the mass fraction of titanium dioxide particles is 5% to 10%, and the mass fraction of cesium tungsten bronze nanoparticles is 1% to 4%; In the skin melt, the mass fraction of titanium dioxide particles is 2.0% to 2.5%; The extrusion mass ratio of the skin melt to the core melt is 30:70 to 70:30.

[0008] Technical Solution 5 based on Technical Solution 4: The titanium dioxide particles in the skin melt are anatase type with a particle size D50 of 0.3μm to 0.4μm; the titanium dioxide particles and cesium tungsten bronze nanoparticles in the core melt both have a particle size D50 of 20nm to 50nm.

[0009] Technical Solution Six based on Technical Solution One: The core-sheath composite fiber obtained in step S30 has a cross-sectional anisotropy of 1.1 to 1.4; the anisotropy is defined as the ratio of the circumcircle radius to the incircle radius of the outer contour of the cross-section.

[0010] Technical solution seven based on technical solution six: In step S30, the wind speed of the side-blowing cooling is 0.4 m / s to 0.6 m / s.

[0011] Technical Solution 8: A method for preparing a fabric with sunlight blocking properties, comprising the following steps: S100: using a core-sheath type composite fiber prepared by a composite fiber preparation method based on any one of Technical Solutions 1 to 7 as raw material yarn; S200: weaving the raw material yarn into a greige fabric using a circular knitting machine, and then performing degreasing, dyeing, and hot air stretching and setting on the greige fabric.

[0012] Technical solution nine based on technical solution eight: In step S100, the circular knitting machine is a 36-needle circular knitting machine, and the knitting structure is a cotton-wool double-sided structure.

[0013] Technical solution ten based on technical solution eight: In step S200, the process conditions for hot air stretching and finishing are: setting temperature 150℃ to 170℃, and fabric overfeed rate 20% to 35%.

[0014] 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: Technical Solution 1 provides a method for preparing composite fibers with solar radiation blocking properties. This method improves upon the problem of severe heat accumulation in existing technologies caused by simply adding near-infrared absorbers, which results in the fiber itself simply adding a triangular cross-section core-sheath composite fiber. In existing technologies, powders such as cesium tungsten bronze are typically added to fibers to block heat from sunlight. The principle of cesium tungsten bronze in blocking heat is that it absorbs near-infrared rays and converts light energy into heat energy. When this powder is distributed in ordinary circular fibers, the circular cross-section easily allows light to refract into the fiber's interior, leading to a large accumulation of heat inside the fiber and raising its temperature. This not only fails to produce a cooling sensation but also conducts heat to the human body. The fiber prepared by this invention has a triangular outer contour, and the triangular cross-section has flat or slightly convex sides. These sides can directly reflect some of the sunlight hitting the fiber surface back to the external environment, reducing the total amount of light entering the fiber and being absorbed by the cesium tungsten bronze, thereby reducing heat generation at the source. Simultaneously, compared to circular fibers of the same thickness, triangular fibers have a larger surface area, increasing the heat dissipation area in contact with the air. Even if the powder in the core layer absorbs light and generates some heat, the larger heat dissipation area can accelerate the dissipation of heat to the surrounding air. This mechanism, which first reduces heat generation through shape reflection and then accelerates heat dissipation by increasing the area, avoids excessive heating of the fiber due to heat absorption. Furthermore, the core-sheath composite structure used in this solution improves the problem of high-content functional powders being difficult to spin. To achieve sufficient heat insulation, a high concentration of cesium tungsten bronze and titanium dioxide needs to be added to the fiber. If single-component spinning is performed directly, excessive solid powder will lead to poor melt flowability, easily clogging the spinneret, making it difficult to form a regular triangular cross-section, and the exposed hard particles will make the fiber feel rough and easily wear down weaving equipment. This solution places the high-concentration powder in the core layer and encapsulates it using a lower-powder-content sheath. The sheath provides good flowability, helping to support and maintain the triangular cross-sectional shape, while encapsulating the rough particles inside, ensuring the smoothness of the fiber surface. Titanium dioxide in the outer layer is mainly used to scatter ultraviolet rays, while cesium tungsten bronze in the core layer is mainly used to absorb near-infrared rays. Together, they achieve full-spectrum blocking of sunlight.

[0015] In technical solution two, the problems of nanoparticle agglomeration and fiber breakage caused by limiting the core layer melt preparation process are improved. This solution first involves high-temperature drying of the powder to remove moisture, ensuring the purity of the melt. Then, a high-speed mixer is used for high-shear mixing, utilizing physical mechanical force to break up the agglomeration forces between powder particles, resulting in a monodisperse distribution of nanoparticles. Finally, the powder is pre-formed into a high-concentration functional masterbatch using a twin-screw extruder, followed by secondary melt spinning. This masterbatch process ensures more uniform dispersion of the functional powder in the final core layer melt, avoiding stress concentration and component blockage caused by localized particle aggregation, ensuring the stability of the fiber's mechanical properties, and also guaranteeing the consistency of the overall fiber's thermal insulation performance.

[0016] In technical solution three, by limiting the intrinsic viscosity of the polymer matrix in both the skin and core layers, a balance between the forming effect of the irregular cross-section and the fiber strength is ensured. Since the core melt is filled with a large number of solid inorganic particles, the viscosity and frictional resistance of the melt are significantly increased, leading to poor flowability. This solution selects a polyester with a lower intrinsic viscosity as the core layer matrix, utilizing its better initial flowability to offset the viscosity increase caused by the addition of powder. This allows the core layer melt to flow smoothly and fill the sharp corners of the triangular micro-orifices in the spinneret, ensuring that the core layer can form a full triangular profile. Simultaneously, a polyester with a higher intrinsic viscosity is selected for the skin layer; high-viscosity polymers have better mechanical strength and film-forming properties. This viscosity matching—high on the outside and low on the inside—utilizes the high strength of the skin layer to protect the overall fiber structure and prevent fiber breakage during drawing, while the low viscosity of the core layer ensures accurate processing of the complex triangular cross-section shape, preventing cross-sectional distortion caused by lag in core layer flow.

[0017] In technical solution four, by limiting the content ratio and extrusion mass ratio of each component, the requirements for heat insulation performance, appearance extension, and spinnability are balanced. Although cesium tungsten bronze has good heat insulation effect, it has a dark blue tint. If the content is too high, the fiber color will be too dark, limiting the application of the fabric in light-colored clothing, and too much heat absorber will cause the fiber to heat up too quickly; if the content is too low, it cannot effectively block near-infrared rays. This solution controls the content of cesium tungsten bronze within a specific range, ensuring sufficient near-infrared blocking rate while avoiding an excessively dark fiber color. The high content of titanium dioxide in the core layer helps block ultraviolet rays, while the lower content of titanium dioxide in the sheath mainly plays a role in matting, making the fiber appearance closer to the feel of natural cotton. At the same time, the extrusion ratio of the sheath and core layer is controlled between 30:70 and 70:30, ensuring that the core layer has enough volume to accommodate the functional powder, and also ensuring that the sheath layer has enough thickness to completely cover the core layer, avoiding the functional powder from piercing the surface due to an excessively thin sheath layer, causing the fiber surface to be rough.

[0018] In technical solution five, by limiting the crystal form and particle size of the particles, the optical properties of particles at different scales are utilized to achieve layered functional control. The skin layer uses micron-sized anatase titanium dioxide. Particles of this size mainly undergo Mie scattering, effectively scattering visible light, reducing the gloss of the fiber surface, achieving excellent extinction effect, and initially reflecting some ultraviolet rays. The core layer uses nano-sized titanium dioxide and cesium tungsten bronze. The size of the nanoparticles is much smaller than the wavelength of visible light, thus having high transmittance for visible light and not significantly affecting the transparency and color of the fiber, but having a strong absorption and shielding effect on ultraviolet and near-infrared rays. The combination of the two achieves excellent heat insulation and sun protection functions while maintaining the good appearance and color of the fiber. In addition, controlling the high filling amount of particles in the core layer at the nanoscale can significantly reduce the frictional resistance when the melt flows through the micropores of the spinneret, reduce the frequency of spinneret clogging, and extend the service life of the spinning assembly.

[0019] In technical solution six, the irregularity of the fiber cross-section is further limited to ensure a good balance between optical reflection and heat dissipation. If the irregularity is too small, the fiber cross-section approaches a circle, and the sides are too smooth, making it unable to effectively reflect incident light back along its original path. Instead, light is easily refracted into the interior. If the irregularity is too large, deep grooves will form on the fiber surface, causing light to be reflected multiple times within the grooves and eventually absorbed, leading to heat accumulation. This solution controls the irregularity between 1.1 and 1.4, resulting in a rounded triangular shape for the fiber cross-section. This shape provides sufficiently straight sides for specular reflection, blocking sunlight, while avoiding the absorption of light due to overly sharp or concave shapes, thus achieving excellent passive cooling.

[0020] In technical solution seven, the shaping accuracy of the fiber-formed irregular structure is ensured by limiting the side-blowing cooling air velocity. If the cooling air velocity is too low, the melt cools slowly, and under the action of surface tension, the originally extruded triangular cross-section will gradually blunt and shrink into a circle, resulting in a reduction in the reflective area. If the cooling air velocity is too high, the strong airflow impact will cause the filaments to vibrate, resulting in uneven fiber evenness. This solution uses an air velocity of 0.4 m / s to 0.6 m / s, which allows the extruded melt to cool and solidify rapidly after leaving the spinneret, quickly fixing the cross-sectional shape in the set triangular state. This effectively counteracts the deformation caused by surface tension, ensuring that the finished fiber has the designed irregularity, thereby stably performing the function of physical reflection and heat insulation.

[0021] Technical solution eight provides a method for preparing a fabric with solar radiation blocking properties. Because the heat-insulating fabric is woven with the above-mentioned composite fibers, it has excellent effects in blocking ultraviolet and infrared rays and can provide good wearing comfort.

[0022] In technical solution nine, a high-density circular knitting machine with 36 needles is used for weaving, which significantly increases the number of loops per unit area, making the fabric structure more compact. Combined with a cotton-wool double-sided weave (i.e., double rib weave), this structure is composed of two rib weaves arranged alternately on both sides, eliminating the perforation common in single-sided fabrics. This forms a tight optical barrier, forcing incident light to hit the heat-insulating fiber structure and preventing it from leaking through the yarn gaps, thus ensuring the fiber's inherent heat-insulating function is fully utilized.

[0023] In technical solution ten, a higher overfeed rate is set, allowing the fabric to enter the drying oven in a relaxed state along the warp direction. Under the action of high-temperature hot air, the internal stress of the fibers is released, causing the yarns to shrink and curl, resulting in a looser fabric structure and a moderate increase in thickness. This loose structure stores a large amount of stagnant air within the fabric. Stagnant air is a poor conductor of heat, forming a thermal insulation barrier. Combined with the fiber's own light-blocking and heat-insulating functions, this further restricts the transfer of external heat to the interior. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a cross-sectional schematic diagram of the composite fiber prepared by the method of preparing composite fiber according to an embodiment of the present invention. Detailed Implementation

[0026] 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.

[0027] 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."

[0028] This invention relates to a method for preparing a composite fiber with solar light blocking properties, which mainly includes the following steps: S10: Prepare a skin melt and a core melt separately; the skin melt comprises a thermoplastic polymer matrix and titanium dioxide particles; the core melt comprises a thermoplastic polymer matrix, titanium dioxide particles, and cesium tungsten bronze nanoparticles; S20: The skin melt and the core melt are introduced into the composite spinning assembly, and the skin melt is controlled to wrap the core melt to form a skin-core composite fluid, which is then extruded through a spinneret with triangular holes. S30: The extruded fluid is cooled by side blowing, stretched and wound to obtain a core-sheath composite fiber with a triangular cross-sectional outer contour.

[0029] The following is a detailed explanation of each step.

[0030] First, step S10 will be described in detail. Step S10 mainly involves the independent preparation of the skin melt and the core melt. In this step, both the skin melt and the core melt use polyester chips as the thermoplastic polymer matrix, but their intrinsic viscosities are set differently. Specifically, the thermoplastic polymer matrix used in the skin melt has an intrinsic viscosity range of 0.64 dL / g to 0.66 dL / g. This viscosity range is chosen to impart sufficient mechanical strength and film stability to the fiber surface. The thermoplastic polymer matrix used in the core melt has an intrinsic viscosity range of 0.58 dL / g to 0.62 dL / g. The lower intrinsic viscosity setting helps maintain suitable rheological properties of the melt when filled with a high content of inorganic powder, ensuring that the melt can fully fill the fine parts of the triangular cross-section.

[0031] For the core layer melt, a functional masterbatch method is employed to ensure the uniform dispersion of nanoparticles in the polymer matrix. This process includes drying the raw materials, mixing and dispersing, and extrusion granulation. First, nano-titanium dioxide powder and cesium tungsten bronze powder are placed in a drying device for dehydration treatment. The drying temperature is set between 110°C and 120°C to remove adsorbed water from the powder surface. Subsequently, the dried powder, dispersant, and the aforementioned low-viscosity thermoplastic polymer chips are fed into a high-speed mixer for physical mixing. The high-speed mixer speed is set between 500 rpm and 1000 rpm, and the shearing action at this speed ensures that the components reach a premixed state. The mixed material is then melt-blended and extruded using a twin-screw extruder to obtain the core layer functional masterbatch. This masterbatch is then remelted to form the core layer melt. Regarding component content, the core layer melt contains 5% to 10% titanium dioxide particles and 1% to 4% cesium tungsten bronze nanoparticles by mass. In addition, the titanium dioxide particles and cesium tungsten bronze nanoparticles selected in the core melt have a particle size D50 controlled within the range of 20 nm to 50 nm.

[0032] For the skin melt, the preparation process involves melt-mixing the aforementioned high-viscosity thermoplastic polymer matrix with titanium dioxide particles. The mass fraction of titanium dioxide particles in the skin melt is set to 2.0% to 2.5%. Regarding particle selection, the titanium dioxide particles in the skin melt are anatase type, with a particle size D50 ranging from 0.3 μm to 0.4 μm. Through the above parameter control and preparation process, skin melt and core melt that meet the rheological matching requirements of composite spinning were obtained, respectively.

[0033] Next, step S20 will be described in detail. Step S20 mainly involves the formation and extrusion molding of the core-sheath composite fluid. In this step, the sheath melt and core melt, precisely metered by a metering pump, are introduced into the composite spinning box respectively. To balance the functional load-bearing capacity of the core layer and the protective shielding effect of the sheath layer, the extrusion mass ratio of the sheath melt to the core melt is controlled within the range of 30:70 to 70:30. This ratio range ensures that the core layer has sufficient volume to accommodate the set concentration of functional powder, while ensuring that the sheath layer has sufficient thickness to completely cover the core layer, thereby preventing the high-hardness inorganic particles inside the core layer from piercing the fiber surface, ensuring the smoothness of the fiber surface and the smoothness of subsequent weaving processes.

[0034] Inside the composite spinning assembly, the skin melt and core melt converge via a distribution plate. During this process, the skin melt flows through the outer channel and uniformly surrounds the core melt flowing through the inner channel, forming a structurally stable skin-core composite fluid. This composite fluid is then extruded through a spinneret mounted at the bottom of the assembly. The spinneret has triangular micropores distributed on it, the geometry of which directly defines the cross-sectional profile of the extruded stream. At the moment the melt flows through the spinneret orifice, it is sheared and shaped by the orifice walls, forming a primary flow with a triangular outer profile. The core layer, rich in titanium dioxide and cesium tungsten bronze, is located in the central region of the triangular cross-section and extends towards the corners, while the fully matte skin layer forms a continuous triangular closed shell on the outermost layer, laying the structural foundation for the fiber's subsequent optical reflection and heat dissipation properties.

[0035] Next, step S30 will be described in detail. Step S30 mainly involves the cooling and solidification of the extruded fluid, the orientation and shaping of the fiber structure, and winding and collection. The core-sheath composite fluid extruded by the spinneret immediately enters the side-blowing cooling device for heat exchange. To ensure that the triangular cross-section formed by the nascent fibers in the molten state can be quickly fixed and to prevent the cross-section from becoming blunt or shrinking back to a circle due to surface tension, the wind speed range of the side-blowing cooling is set to 0.4 m / s to 0.6 m / s. Under this wind speed condition, the molten fine stream can obtain a suitable cooling rate, which ensures the uniformity of polymer crystallization and solidification, and avoids the phenomenon of filament shaking or unevenness caused by excessive wind speed.

[0036] After cooling and curing, the filaments then enter the drawing process. Through the stretching action of the drawing rollers, the macromolecular chains within the fiber are oriented along the fiber axis, thereby imparting the necessary mechanical properties to the fiber. The drawn fiber is finally wound into a cylinder using a winding device. The core-sheath composite fiber prepared by the above process exhibits a specific triangular geometric feature in its cross-sectional outer contour. Specifically, the anisotropy of the fiber cross-section is controlled within the range of 1.1 to 1.4, where the anisotropy is defined as the ratio of the circumcircle radius to the incircle radius of the fiber's cross-section. (Refer to...) Figure 1 The fiber cross-section of this irregularity range is a rounded triangle. This geometry provides flat or slightly convex sides to enhance the specular reflection effect of light, while avoiding the light trapping effect caused by excessively deep groove structures. This achieves synergistic optimization of physical reflection and chemical absorption in thermal insulation performance.

[0037] This embodiment relates to a method for preparing composite fibers with solar radiation blocking properties. This method improves upon the problem in existing technologies where simply adding near-infrared absorbers leads to severe heat accumulation within the fiber itself by preparing core-sheath composite fibers with triangular cross-sections. In existing technologies, powders such as cesium tungsten bronze are typically added to fibers to block heat from sunlight. The principle of cesium tungsten bronze in blocking heat is that it absorbs near-infrared rays and converts light energy into heat energy. When this powder is distributed in ordinary circular fibers, the circular cross-section easily allows light to refract into the fiber's interior, causing a large amount of heat to accumulate inside the fiber, raising its temperature. This not only fails to produce a cooling sensation but also conducts heat to the human body. The fiber prepared by this invention has a triangular outer contour, and the triangular cross-section has flat or slightly convex sides. These sides can directly reflect some of the sunlight hitting the fiber surface back to the external environment, reducing the total amount of light entering the fiber and being absorbed by the cesium tungsten bronze, thereby reducing heat generation at the source. Simultaneously, compared to circular fibers of the same thickness, triangular fibers have a larger surface area, increasing the heat dissipation area in contact with the air. Even if the powder in the core layer absorbs light and generates some heat, the larger heat dissipation area can accelerate the dissipation of heat to the surrounding air. This mechanism, which first reduces heat generation through shape reflection and then accelerates heat dissipation by increasing the area, avoids excessive heating of the fiber due to heat absorption. Furthermore, the core-sheath composite structure used in this solution improves the problem of high-content functional powders being difficult to spin. To achieve sufficient heat insulation, a high concentration of cesium tungsten bronze and titanium dioxide needs to be added to the fiber. If single-component spinning is performed directly, excessive solid powder will lead to poor melt flowability, easily clogging the spinneret, making it difficult to form a regular triangular cross-section, and the exposed hard particles will make the fiber feel rough and easily wear down weaving equipment. This solution places the high-concentration powder in the core layer and encapsulates it using a lower-powder-content sheath. The sheath provides good flowability, helping to support and maintain the triangular cross-sectional shape, while encapsulating the rough particles inside, ensuring the smoothness of the fiber surface. Titanium dioxide in the outer layer is mainly used to scatter ultraviolet rays, while cesium tungsten bronze in the core layer is mainly used to absorb near-infrared rays. Together, they achieve full-spectrum blocking of sunlight.

[0038] Furthermore, embodiments of the present invention also relate to a method for preparing heat-insulating fabric, which mainly includes the following steps: S100: Core-sheath type composite fiber prepared by the above-mentioned composite fiber preparation method is used as raw material yarn; S200: The raw yarn is woven into a greige fabric using a circular knitting machine, and the greige fabric is then degreased, dyed, and subjected to hot air stretching and setting.

[0039] Specifically, in step S200, during the weaving process, the aforementioned raw yarn is fed into a circular knitting machine for weaving. To obtain a high-density fabric structure that blocks light penetration, the circular knitting machine is set to a gauge of 36 gauges (36G). The weaving structure is set to a cotton-wool double-sided weave (also known as a double rib weave), which eliminates the perforations present in single-sided knitted fabrics through the interlacing of positive and negative loops, thereby constructing a physical shielding layer.

[0040] After weaving, the greige fabric immediately enters the dyeing and finishing process. First, a degreasing treatment is performed to remove oil and impurities adhering during spinning and weaving, ensuring the cleanliness of the fiber surface and the uniformity of subsequent dyeing. Then, dyeing is carried out to impart the desired color to the fabric. After dyeing, the fabric undergoes hot-air strut setting to stabilize its dimensions and optimize its hand feel. The process conditions for this hot-air strut setting are set as follows: the setting temperature is controlled within a range of 150℃ to 170℃, a temperature range sufficient to eliminate internal stress within the fibers without causing polymer melting or degradation. Simultaneously, overfeed control is used for fabric feeding, with an overfeed rate set at 20% to 35%. This overfeed rate ensures the fabric enters the drying chamber in a relaxed state along the warp, causing the yarns to shrink and curl under heat, thereby increasing the fabric's bulk and thickness, forming a still air layer within the fabric, and thus improving its thermal insulation properties.

[0041] To better illustrate the technical solution of the present invention, detailed descriptions will be provided below through specific embodiments and comparative examples. These embodiments and comparative examples are intended to demonstrate the feasibility and superiority of the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0042] To ensure the accuracy and reproducibility of the experimental results, all major raw materials used in this section were purchased from commercial sources, with specific specifications or models as follows: Polyester chips for the leather layer: Fully matte polyethylene terephthalate (PET) chips with an intrinsic viscosity of 0.65 dL / g, a titanium dioxide content of 2.2%, and a particle size D50 of 0.35 μm (anatase type), purchased from Sinopec Yizheng Chemical Fiber Co., Ltd.

[0043] The core layer uses polyester chips: semi-dull polyethylene terephthalate (PET) chips with an intrinsic viscosity of 0.60 dL / g, purchased from Sinopec Yizheng Chemical Fiber Co., Ltd.

[0044] Nano titanium dioxide powder: rutile type, particle size D50 of 30 nm, purity ≥99.9%, purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0045] Nano-cesium tungsten bronze powder: chemical formula Cs0.33WO3, particle size D50 is 30 nm, purity ≥99.9%, purchased from Shanghai Huzheng Nanotechnology Co., Ltd.

[0046] Dispersant: Calcium stearate, industrial grade, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0047] Degreasing agent: TF-105F, purchased from Chuanhua Zhilian Co., Ltd.

[0048] Example 1 This embodiment provides a dark-colored heat-insulating fabric and its preparation method, the specific steps of which are as follows: Preparation of core layer functional masterbatch: Nano-titanium dioxide powder and nano-cesium tungsten bronze powder were placed in a vacuum oven and dried at 115℃ for 8 hours to remove moisture. The dried powder (titanium dioxide to cesium tungsten bronze mass ratio of 2:1), dispersant (0.2%), and core layer polyester chips were placed in a high-speed mixer and mixed at 800 rpm for 8 minutes. Subsequently, the mixture was extruded and granulated using a twin-screw extruder within a temperature range of 260-280℃ to obtain the core layer functional masterbatch.

[0049] Preparation of spinning melt: Core layer melt: The core layer functional masterbatch is melted, wherein the mass fraction of titanium dioxide is 8% and the mass fraction of cesium tungsten bronze is 4%, and the matrix is ​​polyester chips used for the core layer. Skin layer melt: The skin layer polyester chips are directly melted.

[0050] Composite spinning: The sheath melt and core melt are introduced into the composite spinning box, and the sheath-core mass ratio is controlled at 50:50. Extrusion is performed using a spinneret with triangular holes, and the spinning temperature is controlled at 285℃.

[0051] Forming and winding: The extruded fluid is cooled by side-blowing air (wind speed 0.5 m / s, temperature 20℃) and drawn on a drawing roller assembly (drawing ratio 2.0). The hot roller temperature is 160℃, and finally, it is wound at a speed of 2600 m / min to obtain a triangular core-sheath composite fiber with a specification of 75D / 36F. Microscopic observation shows that the cross-section of the fiber is a rounded triangle with an anisotropy of approximately 1.3.

[0052] Fabric preparation: The above-mentioned fibers are used as raw yarns and woven into cotton-wool double-sided fabric using a 36-needle circular knitting machine with a weight of 155 g / m².

[0053] Dyeing and finishing process: The grease is degreased (90℃×30min), dyed (disperse dark blue dye, 125℃×45min) and hot air stretching and setting (160℃, overfeed rate 30%), and finally the dark heat insulation fabric is obtained.

[0054] Example 2 This embodiment provides a light-colored heat-insulating fabric and its preparation method.

[0055] The only difference from Example 1 is the formulation of the core melt; all other spinning, weaving, and dyeing and finishing process parameters remain the same.

[0056] The specific formula was adjusted as follows: in the core layer melt, the mass fraction of titanium dioxide was 8%, and the mass fraction of cesium tungsten bronze was 2%. Disperse light gray dye was used in the dyeing process to finally obtain a light-colored heat-insulating fabric.

[0057] Comparative Example 1 This comparative example provides a light-colored, ordinary circular cross-section fabric to compare the performance differences of fabrics without near-infrared absorbers and with circular cross-sections.

[0058] The difference from Example 2 is as follows: Core layer formulation: The core layer melt contains only 10% titanium dioxide and no cesium tungsten bronze nanoparticles.

[0059] Spinneret shape: A conventional circular orifice spinneret is used, and the resulting fiber cross-section is circular (irregularity is 1.0).

[0060] The remaining core-sheath ratio, matrix material, weaving and dyeing processes (light color) are the same as in Example 2.

[0061] Comparative Example 2 This comparative example provides a dark-colored circular cross-section fabric to compare the effect of cross-sectional shape on thermal insulation performance under the same chemical formulation.

[0062] The difference from Example 1 is as follows: Spinneret shape: A conventional circular spinneret is used, resulting in fibers with a circular cross-section.

[0063] Formulation consistency: The core melt formulation is completely consistent with that of Example 1.

[0064] The remaining core-sheath ratio, matrix material, weaving and dyeing processes are the same as in Example 1.

[0065] To verify the performance of the composite fiber prepared according to the present invention, the samples obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were tested according to the following items and standards: Ultraviolet blocking performance: The test was conducted in accordance with the national standard GB / T 18830-2009 "Evaluation of Ultraviolet Protection Performance of Textiles", and the UPF value and UVA transmittance were recorded to calculate the ultraviolet blocking rate.

[0066] Solar and near-infrared blocking performance: Using a UV-Vis-NIR spectrophotometer with an integrating sphere (Shimadzu UV-3600), the transmittance (T) and reflectance (R) of the fabric in the 280nm-2500nm wavelength range were measured in accordance with the spectral testing section of the national standard GB / T 18319-2019 "Test Methods for Photothermal Storage Performance of Textiles".

[0067] Near-infrared blocking rate: The average blocking rate (100% - average transmittance) of the 780nm-2500nm band is taken.

[0068] Solar light blocking rate: The weighted average blocking rate of the entire wavelength range of 280nm-2500nm is taken.

[0069] Heat shading rate (thermal insulation performance): A simulated solar irradiation temperature rise test was conducted according to the test principle of national standard GB / T 35263-2017. At an ambient temperature of 25℃, a simulated solar light source (light intensity 500 W / m²) was used to vertically irradiate the fabric surface, with a temperature sensor placed below the fabric to monitor temperature changes. After 15 minutes of irradiation to reach equilibrium, the temperature below the fabric was recorded. Heat shading rate calculation: Taking the equilibrium temperature of the blank control (without fabric coverage) as T0 and the equilibrium temperature under the sample as T1, the heat shading rate = (T0-T1) / T0*100%.

[0070] The test results are shown in the table below:

[0071] The test results above show that Example 1 and Comparative Example 2 used the exact same core layer chemical formula, both containing 8% titanium dioxide and 4% cesium tungsten bronze, and both were dark-colored fabrics. The only variable was the cross-sectional shape of the fiber. Test data shows that Comparative Example 2, with a circular cross-section, had a heat-shielding rate of 48.0%, while Example 1, with a triangular cross-section, achieved a heat-shielding rate of 56.0%. Under the same chemical composition, the heat-shielding performance of Example 1 was 8 percentage points higher than that of Comparative Example 2. This result indicates that in the circular cross-section fiber of Comparative Example 2, incident light easily enters the fiber interior through refraction, is absorbed by the high concentration of cesium tungsten bronze, and is converted into heat energy, leading to a heat accumulation effect in the fiber body, thus limiting further improvement in the heat-shielding rate. Conversely, the triangular cross-section fiber in Example 1 has a flat and slightly convex side structure, which enhances the specular reflection and scattering effect on incident sunlight, causing some light to be reflected back to the external environment upon contact with the fiber surface, reducing the amount of light entering the fiber interior and being converted into heat energy. Furthermore, the near-infrared blocking rate of Comparative Example 1 was only 74.1%, significantly lower than the 93.4% of Example 2. This indicates that titanium dioxide alone cannot effectively block highly penetrating near-infrared rays. The addition of cesium tungsten bronze significantly improved the fabric's shielding capability against heat source wavelengths.

[0072] 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 obtained 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 knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method for preparing a composite fiber with solar light blocking properties, characterized in that, Includes the following steps: S10: Prepare a skin melt and a core melt separately; the skin melt comprises a thermoplastic polymer matrix and titanium dioxide particles; the core melt comprises a thermoplastic polymer matrix, titanium dioxide particles, and cesium tungsten bronze nanoparticles; S20: The skin melt and the core melt are introduced into the composite spinning assembly, and the skin melt is controlled to wrap the core melt to form a skin-core composite fluid, which is then extruded through a spinneret with triangular holes. S30: The extruded fluid is cooled by side blowing, stretched and wound to obtain a core-sheath composite fiber with a triangular cross-sectional outer contour.

2. The method for preparing a composite fiber with solar light blocking properties as described in claim 1, characterized in that, In step S10, the preparation process of the core layer melt includes: Nano-titanium dioxide powder and cesium tungsten bronze powder are dried at 110°C to 120°C; The dried powder, dispersant, and thermoplastic polymer chips are placed in a high-speed mixer and mixed at a speed of 500 rpm to 1000 rpm. The mixed materials are extruded and granulated using a twin-screw extruder to obtain core layer functional masterbatch, which is then melted to obtain core layer melt.

3. The method for preparing a composite fiber with solar light blocking properties as described in claim 1, characterized in that, In step S10: The skin melt uses a thermoplastic polymer matrix of polyester with an intrinsic viscosity of 0.64 dL / g to 0.66 dL / g; The core melt uses a thermoplastic polymer matrix of polyester with an intrinsic viscosity of 0.58 dL / g to 0.62 dL / g.

4. The method for preparing a composite fiber with solar light blocking properties as described in claim 1, characterized in that, In steps S10 and S20: In the core melt, the mass fraction of titanium dioxide particles is 5% to 10%, and the mass fraction of cesium tungsten bronze nanoparticles is 1% to 4%. In the skin melt, the mass fraction of titanium dioxide particles is 2.0% to 2.5%; The extrusion mass ratio of the skin melt to the core melt is 30:70 to 70:

30.

5. The method for preparing a composite fiber with solar light blocking properties as described in claim 4, characterized in that, The titanium dioxide particles in the skin melt are anatase type with a particle size D50 of 0.3 μm to 0.4 μm; The particle size D50 of the titanium dioxide particles and cesium tungsten bronze nanoparticles in the core melt is 20 nm to 50 nm.

6. The method for preparing a composite fiber with solar light blocking properties as described in claim 1, characterized in that, in The core-sheath composite fiber obtained in step S30 has a cross-sectional anisotropy of 1.1 to 1.4; the anisotropy is defined as the ratio of the circumcircle radius to the incircle radius of the outer contour of the cross-section.

7. The method for preparing a composite fiber with solar light blocking properties as described in claim 6, characterized in that, In step S30, the wind speed of the side-blowing cooling is 0.4 m / s to 0.6 m / s.

8. A method for preparing a fabric with sunlight blocking properties, characterized in that, Includes the following steps: S100: Core-sheath type composite fiber prepared by the method of preparing composite fiber according to any one of claims 1 to 7 is used as raw material yarn; S200: The raw yarn is woven into a greige fabric using a circular knitting machine, and the greige fabric is then degreased, dyed, and subjected to hot air stretching and setting.

9. The method for preparing a fabric with sunlight blocking properties as described in claim 8, characterized in that, In step S100, the circular knitting machine is a 36-gauge circular knitting machine, and the knitting structure is a cotton-wool double-sided structure.

10. The method for preparing a fabric with sunlight blocking properties as described in claim 8, characterized in that, In step S200, the process conditions for hot air stretching and finishing are: setting temperature 150°C to 170°C, and fabric overfeed rate 20% to 35%.

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