Lofted thermal polyester staple fiber and method of making same

Abstract

This invention relates to a fluffy and warm polyester staple fiber and its preparation method, belonging to the field of functional fiber technology. The preparation method of this invention includes the following steps: S1, under the action of a catalyst, a first recycled polyester and a propylene oxide-terminated polydimethylsiloxane are reactively melt-blended and extruded to obtain a sheath material; S2, a second recycled polyester and a chain extender are reactively melt-blended and extruded to obtain a modified recycled polyester; S3, the modified recycled polyester and a third recycled polyester are mixed to obtain a core material; S4, the sheath material and the core material are spun using a sheath-core composite spinning technology to obtain a fluffy and warm polyester staple fiber. This method uses low-value waste polyester as raw material, constructs a dedicated raw material system through reactive melt-blending and extrusion technology, and combines it with a sheath-core composite spinning technology to prepare a polyester staple fiber that possesses high fluffiness, excellent warmth retention, good resilience, and wet-state warmth retention stability.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber technology, and in particular relates to a fluffy and warm polyester staple fiber and its preparation method. Background Technology

[0002] With the increasing demand for lightweight and efficient insulation products in outdoor sports and home bedding, traditional natural down, while offering excellent warmth, is limited by resource availability and its ability to retain warmth in wet conditions significantly diminishes, making it unsuitable for complex all-weather usage scenarios. Synthetic fiber wadding, with its advantages of low cost, washability, and odorlessness, is seeing a steady increase in its application in the insulation materials field. Among these, conventional three-dimensional crimped hollow polyester staple fiber possesses excellent water resistance and compression resistance, but its thermal conductivity is relatively high. Relying solely on the hollow fiber structure combined with mechanical crimping to improve loft, its overall insulation performance still lags significantly behind down. For example, patent application CN 114592246 A discloses a process for preparing three-dimensional crimped hollow polyester staple fiber, which uses asymmetric cooling to form three-dimensional hollow fibers. However, the radial asymmetric stress distribution of the fibers has relatively small differences, resulting in poor crimping performance.

[0003] Meanwhile, the global stockpile of waste polyester continues to accumulate, making the closed-loop high-value utilization of low-value waste polyester a crucial measure for the textile industry to achieve its dual-carbon goals. Currently, the physical recycling and melting regeneration process using bottle flakes as raw material is mature and can produce recycled fibers with stable quality. However, low-polymerization-degree waste films and other foam-grade recycled materials generally suffer from intrinsic viscosity ≤0.55 dL / g and a wide molecular weight distribution index, which significantly reduces the strength of the recycled melt. This leads to problems such as capillary breakage, fuzzy fibers, and frequent spinning end breakage during the spinning process, making it difficult to stably produce fine denier short fibers. This has long constrained the high-value and efficient utilization of this type of low-value waste polyester through spinning.

[0004] Therefore, how to develop high-loft, high-efficiency, and warm polyester staple fibers from low-value waste polyester materials is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a fluffy and warm polyester staple fiber and its preparation method. This method uses low-value waste polyester as raw material, constructs a dedicated raw material system through reactive melt blending extrusion technology, and combines it with a core-sheath composite spinning technology to prepare polyester staple fibers that possess high bulkiness, excellent warmth retention, good resilience, and wet-state warmth retention stability. This achieves high-value spinning utilization of low-value recycled polyester, while simultaneously solving the problems of low melt strength, easy breakage during spinning, and insufficient warmth retention and bulkiness of traditional recycled polyester.

[0006] The first objective of this invention is to provide a method for preparing fluffy and warm polyester staple fiber, comprising the following steps: S1. Under the action of a catalyst, the first recycled polyester and the epoxy propylene oxide-terminated polydimethylsiloxane are reactively melt-blended and extruded to obtain the skin material. S2, the second recycled polyester and the chain extender are reacted and melt-blended and extruded to obtain the modified recycled polyester; S3. Mix the modified recycled polyester described in S2 with the third recycled polyester to obtain the core material; S4. Using a core-sheath composite spinning technology, the sheath material described in S1 and the core material described in S3 are spun to obtain the fluffy and warm polyester staple fiber.

[0007] In one embodiment of the present invention, in S1, the catalyst is tetrabutyl titanate, and the amount added is 80ppm-150ppm of the skin material. When the amount added is less than 80ppm, the catalytic efficiency is insufficient, which needs to be compensated by extending the residence time or increasing the processing temperature. However, this will exacerbate the thermal degradation of recycled polyester and form a vicious cycle. When the amount added is more than 150ppm, it will cause the b value of recycled polyester to increase and yellowing, affecting the fiber color. It may also cause gelation and crosslinking problems, resulting in the clogging of the spinning components. And / or, the intrinsic viscosity of the first recycled polyester is 0.6 dL / g-0.7 dL / g, the source is bottle flakes, and the chemical structure is polyethylene terephthalate; when its intrinsic viscosity is higher than 0.7 dL / g, the required extrusion temperature is higher, which will result in a large difference from the core layer extrusion temperature, affecting the spinning stability; when it is lower than 0.6 dL / g, the sheath layer is difficult to form a highly oriented structure, the stress difference between the sheath and the core layer is reduced, which is not conducive to fiber crimping and forming; And / or, the molecular weight of the epoxypropoxypropyl-terminated polydimethylsiloxane is 4500 g / mol-5500 g / mol, and the addition amount is 1 wt%-3 wt% of the skin material; when the addition amount is less than 1 wt%, the effect of reducing fiber surface energy is not significant, the capillary water absorption rate is high in the wet state, and the wet bulkiness and heat retention rate are significantly reduced, which cannot meet the wet heat retention requirements; when the addition amount is greater than 3 wt%, the compatibility between polydimethylsiloxane and polyester bulk is limited, and excessive unreacted free siloxane segments accumulate in the melt, which will affect the stable extrusion of the melt.

[0008] In one embodiment of the present invention, in S1, the reactive melt blending conditions of the skin material are as follows: temperature is 255℃-275℃, and time is 3min-8min.

[0009] In one embodiment of the present invention, in S2, the intrinsic viscosity of the second recycled polyester is 0.38 dL / g-0.5 dL / g, the source is polyester film, and the chemical structure is polyethylene terephthalate. When its intrinsic viscosity is below 0.38 dL / g, the molecular chain length is insufficient, and it is difficult to form a sufficient topological entanglement structure after chain extension. The melt strength is low, which easily leads to breakage and filament drift problems during the spinning stage. When it is above 0.5 dL / g, the melt viscosity after chain extension is easy to get out of control, the difficulty of blending and dispersing with the third recycled polyester increases, and the core modulus is high and the shrinkage rate is low, which will weaken the asymmetric curling driving force of the core and skin. And / or, the chain extender is a styrene-glycidyl methacrylate copolymer, and the addition amount is 0.3wt%-1wt% of the second recycled polyester; when the addition amount is less than 0.3wt%, the insufficient epoxy group content will lead to a low degree of chain extension, which is difficult to effectively compensate for the melt strength defects of the low intrinsic viscosity recycled polyester, and the spinning process is still prone to breakage and fuzzing problems; when the addition amount is greater than 1wt%, the excessive epoxy group will cause excessive branching or even cross-linking of the molecular chain, resulting in excessively high melt viscosity and gel formation, which can easily lead to clogging of the spinning components.

[0010] In one embodiment of the present invention, in S2, the reactive melt blending conditions of the modified recycled polyester are as follows: temperature is 250℃-270℃, and time is 3min-5min.

[0011] In one embodiment of the present invention, in S3, the intrinsic viscosity of the third recycled polyester is 0.38 dL / g-0.5 dL / g, and the source is polyester film; when its intrinsic viscosity is below 0.38 dL / g, the melt strength of the core matrix is ​​too low, and even if it is blended with modified recycled polyester, it is difficult to achieve stable spinning; when it is above 0.5 dL / g, the difference in shrinkage modulus between the skin layer and the core layer will be reduced, and the three-dimensional helical crimping effect of the fiber will be reduced; And / or, the amount of modified recycled polyester added to the core material is 10wt%-25wt%.

[0012] In one embodiment of the present invention, in S4, the mass ratio of the skin material to the core material is (45-65):(35-55), and the geometric eccentricity e is 0.18-0.32; e = (D−d) / (D+d); where D is the distance from the center of the core layer to the farthest point of the outer circle of the fiber skin layer, and d is the distance from the center of the core layer to the closest point of the outer circle of the fiber skin layer; when the skin layer ratio is less than 45%, i.e., the core layer ratio is greater than 55%, the insufficient skin layer coating thickness easily causes the core layer to be exposed, and the hydrophobic modification and high orientation shrinkage effect of the skin layer cannot be effectively exerted. This leads to a significant deterioration in the fiber's wet-state warmth retention and crimp stability. When e is less than 0.18, the geometric centers of the sheath and core tend to coincide, resulting in insufficient cross-sectional asymmetry. During the relaxation heat setting stage, the difference between the high orientation shrinkage of the sheath and the low shrinkage of the core cannot form an effective internal bending moment, and the driving force for three-dimensional spiral crimping is weak. Consequently, the fiber's bulkiness and warmth retention cannot meet the design specifications. When e is greater than 0.32, excessive eccentricity will cause the sheath thickness distribution to be extremely uneven, with the thinnest point forming a mechanically weak point. This can easily lead to stress concentration, sheath rupture, or even core exposure during spinning, drawing, and subsequent carding processes.

[0013] In one embodiment of the present invention, in S4, the specific steps of the spinning are as follows: first, the fibers are melt-extruded by a screw, then melt-spun using a core-type composite spinneret, followed by pre-stretching, main stretching, relaxation heat setting, cooling, and cutting.

[0014] In one embodiment of the present invention, during the melt extrusion process, the extrusion temperature of the skin material is 285℃-300℃, and the extrusion temperature of the core material is 260℃-275℃; And / or, the melt spinning temperature is 270℃-290℃, and the speed is 800m / min-1500m / min; And / or, the pre-stretching temperature is 70℃-90℃, and the stretching ratio is 1.5 times-2.0 times; And / or, the temperature of the main draw is 95℃-100℃, and the draw ratio is 3.5 times-5 times; And / or, the relaxation heat setting temperature is 120℃-140℃, and the time is 5min-10min; And / or, the length of the cut fiber is 30mm-50mm.

[0015] A second objective of this invention is to provide a fluffy, warm polyester staple fiber prepared by the method described above.

[0016] In one embodiment of the present invention, the linear density of the fluffy and warm polyester staple fiber is 3.0 dtex-8.0 dtex, and the number of crimps is 25 / 25mm-30 / 25mm.

[0017] The technical solution of the present invention has the following advantages compared with the prior art: (1) The preparation method of the present invention involves reactive melt blending of high intrinsic viscosity recycled polyester with epoxypropoxypropyl-terminated polydimethylsiloxane. The epoxy groups open the ring and react with the polyester end groups to form a copolymer structure. This structure can weaken the regularity of the molecular chain, reduce the crystallization rate and crystallinity, so that the skin layer forms a highly oriented, low crystallinity microstructure and generates large internal stress during the spinning quenching and stretching process. The low intrinsic viscosity recycled polyester is reactively melt blended with a chain extender to obtain a modified recycled polyester, which is then blended with the low intrinsic viscosity recycled polyester to prepare the core layer material. The molecular chain topological entanglement structure is used to improve the melt strength and filamentation stability. At the same time, the branched topological structure can suppress the stretching orientation, so that the core layer maintains a low orientation, high entropy elastic state and small internal stress.

[0018] (2) The preparation method described in this invention achieves geometrical misalignment between the skin and core layers through a skin-core composite spinneret. During the subsequent relaxation heat setting process, the highly oriented chain segments of the skin layer undergo significant shrinkage, while the core layer has limited shrinkage due to its low molecular chain orientation. The difference in modulus and shrinkage rate between the two generates an internal bending moment, driving the fiber to form a permanent three-dimensional helical crimp. In addition, the epoxypropoxypropyl-terminated polydimethylsiloxane introduced into the skin layer can reduce the fiber surface energy and impart hydrophobic properties, effectively improving the fiber's fluffiness and warmth retention performance in a wet state. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0020] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0023] In this invention, unless otherwise stated, the recycled polyester used in the embodiments of this invention needs to be pre-crushed and ground to a powder size of 40 mesh before use.

[0024] In this invention, unless otherwise stated, the recycled polyester used in the embodiments of this invention is sourced from Jiangsu Peipu Polymer Technology Co., Ltd., and its chemical structure is polyethylene terephthalate.

[0025] In this invention, unless otherwise stated, the recycled polyester used in the embodiments of this invention is purchased from Yichang Shengteng New Materials Co., Ltd., and its chemical structure is polyethylene terephthalate.

[0026] In this invention, unless otherwise stated, the epoxypropoxypropyl-terminated polydimethylsiloxane used in the embodiments of this invention was purchased from Zhengzhou Gaike Technology Co., Ltd., model B3003, with a molecular weight of approximately 5000 g / mol.

[0027] In this invention, unless otherwise stated, the styrene-glycidyl methacrylate copolymer used in the embodiments of this invention was purchased from BASF, model ADR4468.

[0028] Example 1

[0029] The fluffy and warm polyester staple fiber and its preparation method in this embodiment specifically include the following steps: S1. Using tetrabutyl titanate as a catalyst, recycled polyester (from bottle flakes with an intrinsic viscosity of 0.65 dL / g) and epoxy-propylene-terminated polydimethylsiloxane were reactively melt-blended and extruded at a temperature of 265℃ for 5 minutes. After water cooling, the mixture was pelletized to obtain the skin material. The amount of tetrabutyl titanate added was 115 ppm of the total mass of the skin material, and the amount of epoxy-propylene-propylene-terminated polydimethylsiloxane added was 2 wt% of the total mass of the skin material. S2. Recycled polyester with an intrinsic viscosity of 0.44 dL / g and styrene-glycidyl methacrylate copolymer were premixed in a high-speed mixer, then subjected to reactive melt blending extrusion via a twin-screw extruder at a controlled temperature of 260℃ for 5 minutes. After water cooling, the mixture was pelletized to obtain modified recycled polyester. The amount of styrene-glycidyl methacrylate copolymer added was 0.7 wt% of the recycled polyester. S3. Modified recycled polyester is mixed with recycled polyester from the polyester film source, with an intrinsic viscosity of 0.44 dL / g, to obtain the core layer material; wherein, the amount of modified recycled polyester added to the core layer material is 17 wt%. S4. The sheath material and core material are dried separately to a moisture content of less than 50 ppm, and then fed into the sheath and core screws of the composite spinning machine, respectively. The screw extrusion temperature of the sheath material is 292℃, and the screw extrusion temperature of the core material is 270℃. After the two components are melt-extruded by their respective screws, they are melt-spun through a sheath-core type composite spinneret at a temperature of 280℃ and a speed of 1150 m / min. The nascent fibers obtained by melt spinning are bundled and then pre-stretched in an 80℃ water bath with a stretch ratio of 1.8 times, and then main-stretched under superheated steam at 98℃ with a stretch ratio of 4.2 times. Subsequently, they are relaxed and heat-set at 130℃ for 8 minutes to obtain a crimped structure. Finally, they are cooled and cut to a length of 38 mm to obtain fluffy and warm polyester staple fiber. The mass ratio of the sheath material to the core material is 55:45, and the geometric eccentricity e is 0.25.

[0030] Example 2

[0031] The fluffy and warm polyester staple fiber and its preparation method in this embodiment specifically include the following steps: S1. Using tetrabutyl titanate as a catalyst, recycled polyester (from bottle flakes with an intrinsic viscosity of 0.6 dL / g) is reactively melt-blended and extruded with epoxy-propylene-terminated polydimethylsiloxane at a controlled temperature of 255℃ for 8 minutes. After water cooling, the mixture is pelletized to obtain the skin material. The amount of tetrabutyl titanate added is 80 ppm of the total mass of the skin material, and the amount of epoxy-propylene-terminated polydimethylsiloxane added is 1 wt% of the total mass of the skin material. S2. Recycled polyester with an intrinsic viscosity of 0.38 dL / g and styrene-glycidyl methacrylate copolymer were premixed in a high-speed mixer, then subjected to reactive melt blending extrusion via a twin-screw extruder at a controlled temperature of 250℃ for 5 minutes. After water cooling, the mixture was pelletized to obtain modified recycled polyester. The amount of styrene-glycidyl methacrylate copolymer added was 0.3 wt% of the recycled polyester. S3. Modified recycled polyester is mixed with recycled polyester from the polyester film source, with an intrinsic viscosity of 0.38 dL / g, to obtain the core layer material; wherein, the amount of modified recycled polyester added to the core layer material is 10 wt%. S4. The sheath material and core material are dried separately until the moisture content is less than 50 ppm, and then fed into the sheath and core screws of the composite spinning machine, respectively. The screw extrusion temperature of the sheath material is 285℃, and the screw extrusion temperature of the core material is 260℃. After the two components are melt-extruded by their respective screws, they are melt-spun through a sheath-core type composite spinneret at a temperature of 270℃ and a speed of 800 m / min. The nascent fibers obtained by melt spinning are bundled and then pre-stretched in a 70℃ water bath with a stretch ratio of 1.5 times, and then main-stretched under 95℃ superheated steam with a stretch ratio of 3.5 times. Subsequently, they are relaxed and heat-set at 120℃ for 10 min to obtain a crimped structure. Finally, they are cooled and cut to a length of 30 mm to obtain fluffy and warm polyester staple fiber. The mass ratio of the sheath material to the core material is 45:55, and the geometric eccentricity e is 0.18.

[0032] Example 3

[0033] The fluffy and warm polyester staple fiber and its preparation method in this embodiment specifically include the following steps: S1. Using tetrabutyl titanate as a catalyst, recycled polyester (from bottle flakes with an intrinsic viscosity of 0.7 dL / g) is reactively melt-blended and extruded with epoxy-propylene-terminated polydimethylsiloxane at a controlled temperature of 275℃ for 3 minutes. After water cooling, the mixture is pelletized to obtain the skin material. The amount of tetrabutyl titanate added is 150 ppm of the total mass of the skin material, and the amount of epoxy-propylene-terminated polydimethylsiloxane added is 3 wt% of the total mass of the skin material. S2. Recycled polyester with an intrinsic viscosity of 0.5 dL / g and styrene-glycidyl methacrylate copolymer were premixed in a high-speed mixer, then subjected to reactive melt blending extrusion via a twin-screw extruder at a controlled temperature of 270℃ for 3 minutes. After water cooling, the mixture was pelletized to obtain modified recycled polyester. The amount of styrene-glycidyl methacrylate copolymer added was 1 wt% of the recycled polyester. S3. Modified recycled polyester is mixed with recycled polyester from the polyester film source, with an intrinsic viscosity of 0.5 dL / g, to obtain the core layer material; wherein the amount of modified recycled polyester added to the core layer material is 25 wt%. S4. The sheath material and core material are dried separately to a moisture content of less than 50 ppm, and then fed into the sheath and core screws of the composite spinning machine, respectively. The screw extrusion temperature of the sheath material is 300℃, and the screw extrusion temperature of the core material is 275℃. After the two components are melt-extruded by their respective screws, they are melt-spun through a sheath-core type composite spinneret at a temperature of 290℃ and a speed of 1500 m / min. The nascent fibers obtained by melt spinning are bundled and then pre-stretched in a 90℃ water bath with a stretch ratio of 2.0 times, and then main-stretched under 100℃ superheated steam with a stretch ratio of 5 times. Subsequently, they are relaxed and heat-set at 140℃ for 5 minutes to obtain a crimped structure. Finally, they are cooled and cut to a length of 50 mm to obtain fluffy and warm polyester staple fiber. The mass ratio of the sheath material to the core material is 65:35, and the geometric eccentricity e is 0.32.

[0034] Comparative Example 1

[0035] The process is basically the same as in Example 1, except that the recycled polyester from bottle flakes with an intrinsic viscosity of 0.65 dL / g in S1 is replaced with recycled polyester from polyester film with an intrinsic viscosity of 0.44 dL / g.

[0036] Comparative Example 2

[0037] The process is basically the same as in Example 1, except that the recycled polyester from the polyester film source with an intrinsic viscosity of 0.44 dL / g in S2 and S3 is replaced with recycled polyester from the bottle flake source with an intrinsic viscosity of 0.65 dL / g.

[0038] Comparative Example 3

[0039] The basic structure is the same as in Example 1, except that the epoxypropoxypropyl-terminated polydimethylsiloxane in S1 is replaced with hydroxyl-terminated polydimethylsiloxane (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with a molecular weight of approximately 5000 g / mol).

[0040] Comparative Example 4

[0041] The process is basically the same as in Example 1, except that in S1, reactive melt blending extrusion is not performed using epoxypropoxypropyl-terminated polydimethylsiloxane.

[0042] Comparative Example 5

[0043] The basic formula is the same as in Example 1, except that the styrene-glycidyl methacrylate copolymer in S2 is replaced with polycarbodiimide (purchased from Shanghai Lai'an Industrial Co., Ltd., brand name HYDROSTAB®5).

[0044] Comparative Example 6

[0045] The process is basically the same as in Example 1, except that in S2, the styrene-glycidyl methacrylate copolymer is not used for reactive melt blending extrusion.

[0046] Test Example 1

[0047] Performance tests were conducted on the polyester staple fibers prepared in the examples and comparative examples: (1) Linear density: The test shall be conducted in accordance with the standard of Method A (weighing method of mid-section of bundle fiber) in GB / T 14335-2008 Test method for linear density of short chemical fiber; (2) Number of curls: Tested according to the standard of GB / T 14338-2022 Test method for the curl performance of chemical fiber short fiber; (3) Compression resilience: The compression resilience test shall be conducted in accordance with the standard in Appendix B of GB / T 35261-2017 tires; (4) Thermal insulation rate and heat transfer coefficient: The test shall be conducted in accordance with the standard GB / T 35762-2017 Test method for heat transfer performance of textiles, plate method; Table 1 shows the final measured parameters: Table 1

[0048] As can be seen from Table 1, the polyester staple fiber in the embodiment has full three-dimensional crimp, excellent compression resilience, balanced dry and wet heat retention performance, and a lower heat transfer coefficient. Its overall fluffy and warming effect is significantly better than that of the other comparative examples.

[0049] Comparing Example 1 and Comparative Example 1, it can be seen that the fiber crimp number, resilience, and heat retention effect of Comparative Example 1 are significantly worse. This is because after the skin layer is made of low-viscosity recycled polyester, the modulus and shrinkage difference between the skin and the core are greatly reduced, which makes it impossible to form a sufficient crimp driving force, and the fluffiness and still air storage capacity decrease simultaneously.

[0050] Comparing Example 1 and Comparative Example 2, it can be seen that the fiber crimping effect, resilience and heat retention performance of Comparative Example 2 are significantly reduced. This is because after using high-viscosity recycled polyester in the core layer, the difference between the core-sheath shrinkage and modulus is weakened, the asymmetric internal bending moment is insufficient, and it is difficult to form a stable three-dimensional spiral crimp.

[0051] Comparing Example 1 and Comparative Example 3, it can be seen that the fiber crimp, wet-state heat retention stability and resilience of Comparative Example 3 all declined significantly. This is because hydroxyl-terminated polydimethylsiloxane cannot be effectively copolymerized with polyester, so it cannot control the crystal orientation of the skin layer, nor can it provide a stable hydrophobic effect, resulting in a significant reduction in wet fluffiness and heat retention.

[0052] Comparing Example 1 and Comparative Example 4, it can be seen that the fiber crimping quantity, fluffiness and resilience, and wet insulation capacity of Comparative Example 4 are significantly deteriorated. This is because the lack of siloxane modification results in higher crystallinity of the skin layer, loss of hydrophobicity, smaller difference in shrinkage between the skin and core, and simultaneous deterioration of crimping and wet insulation.

[0053] Comparing Example 1 and Comparative Example 5, it can be seen that the fiber crimping effect, compression resilience and heat retention performance of Comparative Example 5 are not as good as those of Example 1. This is because the alternative chain extender cannot form a branched entanglement structure to suppress the core orientation, the difference between the core and the skin shrinkage is insufficient, and the three-dimensional crimping and fluffy heat retention are difficult to meet the standards.

[0054] Comparing Example 1 and Comparative Example 6, it can be seen that the fiber crimping, resilience and heat retention properties of Comparative Example 6 are significantly reduced. This is because the core layer is not extended, resulting in insufficient melt strength, poor spinning stability, easy orientation of linear chains, and too small difference between core and sheath shrinkage, which greatly weakens the crimping and fluffy heat retention effect.

[0055] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing fluffy and warm polyester staple fiber, characterized in that, Includes the following steps: S1. Under the action of a catalyst, the first recycled polyester and the epoxy propylene oxide-terminated polydimethylsiloxane are reactively melt-blended and extruded to obtain the skin material. S2, the second recycled polyester and the chain extender are reacted and melt-blended and extruded to obtain the modified recycled polyester; S3. Mix the modified recycled polyester described in S2 with the third recycled polyester to obtain the core material; S4. Using a core-sheath composite spinning technology, the sheath material described in S1 and the core material described in S3 are spun to obtain the fluffy and warm polyester staple fiber.

2. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S1, the catalyst is tetrabutyl titanate, and the amount added is 80ppm-150ppm of the skin material; And / or, the intrinsic viscosity of the first recycled polyester is 0.6 dL / g-0.7 dL / g, the source is bottle flakes, and the chemical structure is polyethylene terephthalate; And / or, the molecular weight of the epoxypropoxypropyl-terminated polydimethylsiloxane is 4500 g / mol-5500 g / mol, and the amount added is 1 wt%-3 wt% of the skin material.

3. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S1, the reactive melt blending conditions of the skin material are as follows: temperature 255℃-275℃, time 3min-8min.

4. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S2, the intrinsic viscosity of the second recycled polyester is 0.38 dL / g-0.5 dL / g, the source is polyester film, and the chemical structure is polyethylene terephthalate; And / or, the chain extender is a styrene-glycidyl methacrylate copolymer, and the amount added is 0.3wt%-1wt% of the second recycled polyester.

5. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S2, the reactive melt blending conditions of the modified recycled polyester are as follows: temperature 250℃-270℃, time 3min-5min.

6. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S3, the intrinsic viscosity of the third recycled polyester is 0.38 dL / g-0.5 dL / g, and its source is polyester film; And / or, the amount of modified recycled polyester added to the core material is 10wt%-25wt%.

7. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S4, the mass ratio of the skin material to the core material is (45-65):(35-55), and the geometric eccentricity e is 0.18-0.

32.

8. The method for preparing fluffy and warm polyester staple fiber according to claim 1, characterized in that, In S4, the specific steps of the spinning process are as follows: first, the fibers are melt-extruded by a screw, then melt-spun using a composite spinneret with a scabbard core, followed by pre-stretching, main stretching, relaxation heat setting, cooling, and cutting.

9. The method for preparing fluffy and warm polyester staple fiber according to claim 8, characterized in that, During the melt extrusion process, the extrusion temperature of the skin material is 285℃-300℃, and the extrusion temperature of the core material is 260℃-275℃. And / or, the melt spinning temperature is 270℃-290℃, and the speed is 800m / min-1500m / min; And / or, the pre-stretching temperature is 70℃-90℃, and the stretching ratio is 1.5 times-2.0 times; And / or, the temperature of the main draw is 95℃-100℃, and the draw ratio is 3.5 times-5 times; And / or, the relaxation heat setting temperature is 120℃-140℃, and the time is 5min-10min; And / or, the length of the cut fiber is 30mm-50mm.

10. Fluffy and warm polyester staple fiber prepared by the method of any one of claims 1-9.

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