Ultrafine denier shaped polyester staple fiber and method of making same

Abstract

This invention provides an ultrafine denier profiled polyester staple fiber and its preparation method. The method includes steps such as raw material pretreatment, melt spinning, nascent fiber treatment, heat setting and crimping, oiling, and cutting. The polyester chips used possess high intrinsic viscosity and melting point. Under six-zone temperature control, a high-pore-density spinneret, and a high draw ratio, ultrafine, profiled, and hollow polyester staple fibers are obtained. The resulting polyester staple fibers exhibit good breaking strength, resilience, and a low-defect structure, significantly improving fiber bulkiness, flexibility, and structural consistency. This method overcomes the environmental and process limitations of traditional island-of-the-sea fiber alkaline stripping methods and is suitable for high-end fillings, imitation plush materials, and nonwoven materials.

Description

Technical Field

[0001] This invention relates to the technical field of functional fibers, and in particular to an ultrafine denier profiled polyester staple fiber and its preparation method. Background Technology

[0002] Today, polyester staple fiber is widely used in apparel, home textile filling, and industrial applications due to its excellent strength, toughness, and abrasion resistance. The research and development and production of functional and differentiated polyester staple fibers are also becoming increasingly mature. Ultrafine denier fiber, as a typical representative of differentiated polyester staple fiber, typically has a linear density of less than 0.5 denier and a diameter of only 5-8 micrometers, equivalent to 1 / 20th the thickness of a human hair. Its extremely fine diameter gives it a soft touch and silk-like luster, and the dense arrangement of fibers forms a microporous structure, significantly improving warmth and breathability. It is used for filling lightweight, warm clothing and in high-end home textiles. Furthermore, the morphology of ultrafine denier staple fiber makes it easy to disperse and blend. In nonwoven processes, it can form a uniform network structure, enhancing bulk and resilience, and is widely used in faux fur, toy filling, and medical and hygiene products.

[0003] In terms of cross-sectional morphology, ultrafine denier polyester staple fibers can be shaped into multi-lobed, hollow, or irregular structures through composite spinning technology. For example, a four-leaf clover cross-section can enhance capillary effect by increasing the specific surface area, thus achieving rapid sweat wicking. A hollow structure further reduces fiber density, resulting in a fluffy and lightweight feel. By constructing nanoscale grooves and micropores on the fiber surface, a soft silk luster is achieved through diffuse reflection, while also enhancing fiber cohesion and anti-pilling properties. Chinese invention patent application CN117535820A discloses a moisture-wicking ultrafine polyester fiber. By adding abundant reduced graphene and polyether structural fragments to the modifier molecular structure, the antistatic properties and moisture-wicking breathability of the polyester fiber can be significantly improved. Chinese invention patent application CN115961366A discloses a method for preparing non-fluorescent ultrafine polyester staple fiber, with fiber length reaching 9.5~12.5mm and fineness reaching 0.5~0.7D; and by adding an antistatic smoothing agent to the oiling agent sprayed on the nascent fiber, the smoothness and cohesion of the ultrafine polyester staple fiber are increased.

[0004] However, due to limitations in production equipment and processes, traditional ultrafine denier polyester staple fiber production can only be achieved through island-of-sea composite spinning. The removal of the sea component typically requires alkali treatment, which introduces environmental pressure. If melt spinning is used directly, traditional spinnerets struggle to meet the fiber fineness requirements, and the process settings present significant challenges. Temperature, ring blowing, and winding speed can all lead to excessively high fiber defect content and poor bulkiness, ultimately affecting subsequent applications. Therefore, how to produce high-quality, stable ultrafine denier polyester fibers using environmentally friendly methods under existing process conditions, and further enhance their functionality, has become a crucial research direction in ultrafine denier fiber production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an ultrafine denier profiled polyester staple fiber and its preparation method.

[0006] A method for preparing ultrafine denier profiled polyester staple fiber includes the following steps:

[0007] S1 raw material pretreatment: Drying the polyester chips;

[0008] S2 Melt Spinning: The dried polyester chips are melted sequentially through zones one to six in a screw extruder. The temperature range of zones one to six is ​​280–305℃. Melt spinning is then performed through a spinneret. The spinning box temperature is 285–295℃, the pump feed rate is 700–840 g / min, the pressure difference between the inlet and outlet air of the annular blower is 580–730 Pa, and the winding speed is 1050–1150 m / min, to obtain ultra-fine denier profiled polyester nascent yarn.

[0009] S3 nascent yarn treatment: The ultra-fine denier profiled polyester nascent yarn is sequentially bundled, first-stage oil bath drawing, and second-stage drawing; the first-stage oil bath drawing temperature is controlled at 65-70℃, and the second-stage drawing temperature is 100-120℃.

[0010] S4 Heat Setting and Crimping: The stretched fibers are subjected to tension heat setting and crimping treatments in sequence;

[0011] S5 Oiling and Cutting: An oiling agent is applied to the surface of the crimped fiber. The fiber is then relaxed, heat-set, dried, and cut to obtain ultra-fine denier profiled polyester staple fiber.

[0012] This invention systematically optimizes the entire process of polyester fiber production, from raw material drying to short fiber forming, through clearly defined staged control (S1 to S5). Particularly in the melt spinning and post-processing stages, it integrates coordinated control of multiple key parameters, significantly improving fiber forming stability and shape retention. By setting segmented temperature control (280–305℃) in screw zones one to six and the spinning box temperature (285–295℃), multi-stage heat-fluid coupling control of the polyester melt is achieved from initial melting, homogenization, and stable flow to the outlet. This effectively prevents localized overheating degradation or uneven crystallinity, ensuring rheological stability and die-formed consistency during the spinning process. Furthermore, by coordinating the ring blower pressure difference (580–730 Pa) with high-precision winding speed (1050–1150 m / min), this invention stabilizes the fiber shrinkage trajectory during melt solidification, thereby reducing fiber deviation, adhesion, and cross-sectional deformation. The present invention also uses primary (65-70℃) and secondary (100-120℃) stretching to fully stretch and oriented crystallize the polymer chain segments, thereby improving the fiber's breaking strength and resilience and preventing the cross-section from shrinking and rounding.

[0013] Compared with traditional methods of preparing microfibers through island-island methods or chemical stripping, this invention is the first to achieve stable and continuous production through physical processes without relying on stripping or alkali treatment, significantly reducing environmental burden and improving the versatility of production lines.

[0014] Furthermore, in the S1 raw material pretreatment step, the polyester chips are high-viscosity polyester chips with an intrinsic viscosity of 0.68–0.75 dL / g and a melting point of 257–268°C.

[0015] The high intrinsic viscosity (0.68–0.75 dL / g) indicates that the polyester has a longer molecular chain and a higher molecular weight. This molecular structure provides stronger rheological stability and resistance to degradation during high-temperature screw extrusion (zones 1 to 6 are set at 280–305°C). This allows the melt to maintain a consistent filamentation state when forming fine denier profiled fibers through precision spinnerets (such as hollow 4400-hole or cross-shaped 4000-hole spinnerets), avoiding fiber breakage, uneven thickness, or cross-sectional distortion caused by low-viscosity melts.

[0016] Secondly, under the dynamic balance of spinning pump feed rate (700–840 g / min), high winding speed (1050–1150 m / min), and ring blow pressure difference (580–730 Pa), the segmental strength and thermal stability of high-viscosity polyester enable it to withstand the stress caused by high draw ratios (3.38–3.91 times) without breaking or necking, thus significantly improving the breaking strength and crimp recovery force of the final fiber. This characteristic is fundamental to the practical application of ultrafine denier fibers—achieving a synergy between "fineness" and "strength," rather than sacrificing strength for a reduction in denier.

[0017] A sufficient thermal safety window exists between the high melting point range (257–268℃) and the set heat setting temperature range (165–175℃), allowing the fiber to maintain its directional solidification in its molten state during the setting process, rather than undergoing excessive softening or shrinkage. This has a significant advantage in maintaining the cross-sectional morphology stability of complex irregular cross-sections (such as trilobal and hollow cross structures), and can significantly improve the ratio of irregularity and hollowness that retain their morphology after curling and cutting.

[0018] Furthermore, in the S2 melt spinning step, the temperature of the screw extruder is 280℃~290℃ in zone one, 285℃~295℃ in zone two, 290℃~300℃ in zone three, 295℃~305℃ in zone four, 290℃~300℃ in zone five, 285℃~295℃ in zone six, and the temperature of the spinning box is 285~295℃.

[0019] With high-viscosity polyester chips as raw material, the stepwise increase of temperature in each zone (e.g., 280–290℃ in zone 1 and up to 305℃ in zone 4) can effectively promote the dissolution of polyester crystal regions, the stretching of chain segments, and the balance of the thermal flow field. This ensures that the melt has a stable viscoelastic window from initial melting, plasticization, and steady flow to the extrusion stage, overcoming the problems of melt degradation, entrainment of air bubbles, or dead zones in flow zones in traditional integrated heating or designs with excessive temperature differences, and significantly improving spinning consistency.

[0020] Secondly, the spinnerets of fine denier profiled fibers typically have complex geometries (such as trefoil, cross, or hollow structures), requiring extremely high melt shear stability and pressure distribution uniformity. By employing the aforementioned six-segment temperature control strategy, a continuous and progressive melt viscosity gradient and shear rate field along the barrel direction can be constructed. This, in conjunction with the spinneret flow field design, significantly improves the stability of the profiled fiber cross-sectional morphology and reduces the incidence of melt flow deviation and local distortion.

[0021] Furthermore, during melt spinning, the chamber temperature is controlled between 285–295°C, which facilitates controllable heat exchange between the melt at the spinning outlet and the ring blower cooling system. Combined with the pump supply (700–840 g / min) and the ring blower pressure difference (580–730 Pa), this temperature range setting allows the fiber to maintain ideal elongation flow and tension stability before cooling and setting, avoiding initial defects such as fuzz and off-center fibers, improving fiber winding uniformity, and providing a high-quality precursor for subsequent drafting and crimping processes.

[0022] Furthermore, in the S2 melt spinning step, the spinneret is selected from one of 4000 holes, 4800 holes, hollow 4400 holes, and cross 4000 holes.

[0023] By selecting spinnerets with unique structures (such as hollow 4400-hole spinnerets, cross-shaped 4000-hole spinnerets, etc.), the fiber cross-section can be designed and controlled, effectively forming various irregular cross-sections (such as trefoil, cross, hollow ellipse, etc.). Compared with conventional round-hole spinnerets, this solution significantly improves the fiber's irregularity (≥85%) and hollowness (≥16%), thereby improving the fiber's bulkiness, moisture absorption, and luster, creatively balancing structural function and processing efficiency.

[0024] Furthermore, in the S3 nascent silk processing step, the draw ratio is controlled between 3.38 and 3.91.

[0025] After polyester melt cools and solidifies, it has an amorphous shape. To obtain high-strength, high-resilience fibers, axial tension must be applied to the molecular chains through a drawing process to achieve chain segment rearrangement and partial crystallization. If the drawing ratio is too low, the chain segments cannot be stretched sufficiently, resulting in poor fiber mechanical properties; if the ratio is too high, it is prone to breakage or necking, affecting the yield.

[0026] The selected draw ratio range of 3.38 to 3.91 times in this invention falls within the stable processing window for polyester materials, where maximum molecular chain orientation can be achieved without chain breakage at temperatures between 65 and 120°C (corresponding to the primary oil bath and secondary draw temperatures). This effectively improves fiber breaking strength and elongation at break without sacrificing the fine denier target. Furthermore, ultrafine denier fibers, due to their low linear density and small fiber diameter, typically face problems such as high breakage rate and low tensile strength. Sufficient draw within this range ensures that the fiber possesses a sufficiently ordered chain structure and strength support even in its fine denier state, guaranteeing its stress adaptability during subsequent crimping, heat setting, and oiling / cutting processes, significantly reducing fiber breakage and uneven crimping.

[0027] Furthermore, the drawing ratio, along with the primary oil bath temperature (65–70℃) and the secondary drawing temperature (100–7120℃), forms a dual synergistic system of "temperature-stress," which not only promotes segment tension-induced crystallization but also provides a structural pre-set basis for morphology fixation during the tensile heat setting process. This serves as a pre-support mechanism for constructing irregular hollow + curled structures.

[0028] Furthermore, in the S4 heat setting and curling steps, the main curling pressure is controlled at 0.36–0.42 MPa, the back pressure is controlled at 0.18–0.22 MPa, and the linear speed of the curling process is 190–210 m / min.

[0029] The precise control of the main and back pressure during crimping within a reasonable range, combined with a linear velocity of 190–210 m / min, ensures that the fibers form a consistent crimp structure with strong resilience. This setting avoids the problems of poor fiber loft and easy clumping caused by uneven crimping in traditional processes, significantly improving the elastic recovery rate and down-like feel of the finished product.

[0030] Furthermore, in the S4 heat setting and curling step, the heat setting temperature is controlled at 165-175°C.

[0031] Controlling the heat setting temperature within the range of 165–175°C, which is above the glass transition temperature of polyester but below the melting temperature, helps to lock the fiber crimp state and eliminate residual stretching stress, effectively improving crimp stability and dimensional retention, and ensuring the uniformity of short fibers during nonwoven web laying or spinning.

[0032] Furthermore, in the S5 oiling and cutting step, the silicone oil component in the applied oil accounts for 7% to 8% of the total mass of the oil.

[0033] By controlling the silicone oil concentration between 7% and 8%, the fiber is ensured to have good surface lubricity and antistatic properties, reducing fiber breakage and entanglement rates, and effectively improving fiber conveying and opening efficiency. Compared with traditional low-silicone-oil formulations, this invention improves process continuity and post-processing adaptability while ensuring environmental friendliness.

[0034] An ultrafine denier shaped polyester staple fiber prepared by the above-mentioned method of preparing ultrafine denier shaped polyester staple fiber, wherein the ultrafine denier shaped polyester staple fiber has an eccentricity ≥85%, a hollow fiber hollowness ≥16%, a fiber linear density of 0.33~0.77dtex, and a compressive elasticity ≥70%.

[0035] Furthermore, the fiber has a breaking strength of 4.0–5.2 cN / dtex, a breaking elongation of 30%–45%, a fiber length of 12 mm–52 mm, an extra-long fiber content of 0–5 mg / 100 g, a defect content of 2–30 mg / 100 g, a crimp number of 9–14 per 25 mm, and a crimp rate of 9%–17%.

[0036] The finished fiber exhibits an irregularity of ≥85%, a hollowness of ≥16%, a linear density of 0.33–0.77 dtex, and a compressive elasticity of ≥70%. These structural indicators demonstrate that this invention achieves a multi-functional fusion structure of "ultrafine + irregular shape + hollow," enhancing both tactile feel and lightweight properties while ensuring synergistic optimization of functional properties such as fluffiness, moisture absorption, and thermal insulation. This is significantly different from traditional single round or coarse denier polyester staple fibers. The fiber breaking strength reaches 5.2 cN / dtex, the breaking elongation reaches 45%, and the content of ultra-long fibers is controlled within 0–5 mg / 100g, the defect content within 2–30 mg / 100g, and the crimp number and crimp rate remain within an excellent range. These data comprehensively reflect the finished fiber quality control capabilities and excellent machinability, fully demonstrating the technological maturity and advancement of the preparation system in terms of high consistency and high-precision mass production.

[0037] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0038] (1) The polyester short fiber obtained by the present invention has a deformability of ≥85% and a hollowness of ≥16%, and maintains a linear density (0.33~0.77 dtex) in the ultra-fine denier range, breaking through the density limitation of traditional circular fiber structure. The fiber has both lightweight, flexible and functional cross-sectional characteristics, giving the material better bulkiness, moisture absorption and thermal conductivity.

[0039] (2) By setting up six independent temperature control zones (280~305℃) + spinning box temperature zone (285~295℃), the present invention precisely controls the viscoelasticity and homogenization of polyester melt at each stage; and matches the irregular plate structure with 4000~4800 spinneret holes and high winding speed (1050–1150 m / min) to achieve continuous high consistency spinning and significantly reduce defects caused by filament deviation, fuzz and melt shear instability.

[0040] (3) The present invention uses a high draw ratio of 3.38 to 3.91 times in combination with a first-stage oil bath (65 to 70°C) and a second-stage draw temperature zone (100 to 120°C) to form a stress-temperature synergistic orientation mechanism, so that the molecular chains are arranged in an orderly manner, the breaking strength is increased to 5.2 cN / dtex, the breaking elongation reaches 45%, and the fiber maintains good tensile and resilience properties in subsequent crimping and web laying.

[0041] (4) This invention controls the main pressure (0.36-0.42 MPa), back pressure (0.18-0.22 MPa) and crimping speed (190-210 m / min) by matching and controlling the main pressure (0.36-0.42 MPa), back pressure (0.18-0.22 MPa), and crimping speed (190-210 m / min), and fixes the crimping shape by setting temperature (165-175℃). The fiber compression elasticity is generally higher than 70%, and it has a stable crimping structure of 9-14 crimps / 25mm. It is suitable for imitation wool and down substitute products with high loft requirements.

[0042] (5) Compared with the traditional island composite spinning + alkali treatment stripping method relied on by ultrafine denier fibers, the present invention is based entirely on melt spinning - physical crimping - heat setting process, which does not require alkali washing, stripping and recycling, making the process greener and more environmentally friendly, avoiding the discharge of alkaline wastewater, and improving industrial adaptability and promotion value. Attached Figure Description

[0043] Figure 1 An optical microscope image of the cross-section of an ultrafine denier profiled polyester staple fiber prepared in Example 1.

[0044] Figure 2 An optical microscope image of the cross-section of an ultrafine denier profiled polyester staple fiber prepared in Example 2.

[0045] Figure 3 An optical microscope image of the cross-section of an ultrafine denier profiled polyester staple fiber prepared in Example 3. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the embodiments.

[0047] Example 1

[0048] An ultrafine denier profiled polyester staple fiber and its preparation method are described below:

[0049] S1 raw material pretreatment: The polyester chips are first dried at 80℃ for 2 hours, and then vacuum dried at 120℃ for 10 hours to complete the raw material pretreatment.

[0050] Polyester chips: The manufacturer is Zhejiang Hengyi Petrochemical Co., Ltd. The intrinsic viscosity of the polyester chips is 0.72 dL / g and the melting point is 265℃.

[0051] S2 Melt Spinning: The dried polyester chips are fed into a screw extruder for melting. The temperature settings for each section of the extruder are as follows:

[0052] The temperature in Zone 1 is 285℃, the temperature in Zone 2 is 290℃, the temperature in Zone 3 is 295℃, the temperature in Zone 4 is 300℃, the temperature in Zone 5 is 295℃, and the temperature in Zone 6 is 290℃.

[0053] The spinning box temperature is set to 290℃;

[0054] The spinneret used has a circular structure with 4000 holes;

[0055] The pump supply rate is 783 g / min;

[0056] The pressure difference between the air inlet and outlet of the annular blower is 700 Pa;

[0057] The winding speed is 1100 m / min;

[0058] This step yields ultra-fine denier profiled polyester nascent yarn.

[0059] S3 nascent yarn treatment: The ultra-fine denier profiled polyester nascent yarn is sequentially bundled, subjected to primary oil bath drawing, and secondary drawing; the primary oil bath temperature is set to 68℃, the secondary drawing temperature is 110℃, and the drawing ratio is 3.61 times.

[0060] S4 Heat Setting and Crimping: The stretched fibers are subjected to tension heat setting and crimping treatment in sequence; the heat setting temperature is 170℃, the crimping main pressure is 0.36 MPa, the back pressure is 0.18 MPa, and the crimping linear speed is 200 m / min.

[0061] S5 Oiling and Cutting: Apply an oil containing 7 wt.% silicone oil to the crimped fiber for lubrication and antistatic treatment, followed by relaxation heat setting, drying and cutting to obtain ultrafine denier profiled polyester staple fiber with a length of 12 mm.

[0062] The difference between Examples 2-12 and Example 1 is that the process parameters in each process step are set differently, as shown in Tables 1 to 4 below.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067] Table 3

[0068]

[0069] Table 4

[0070]

[0071] Comparative Example 1

[0072] The short fibers were prepared according to the method for preparing non-fluorescent ultrafine polyester staple fibers disclosed in CN115961366A, as detailed below:

[0073] Step 1: Drying

[0074] The polyester raw material was placed in a vacuum drying oven and dried at a temperature of 160°C, a vacuum degree of 0.08 MPa, and a drying time of 5 hours. The moisture content after drying was 145 ppm.

[0075] Step 2: Melt spinning

[0076] The dried polyester raw material chips were fed into a screw extruder and melted at 288°C. The metering pump feed rate was 3900 g / min, and the spinning speed was set to 3000 m / min. The polyester raw material chips used were 0.6 dL / g with a melting point of 260°C.

[0077] Step 3: Cooling and Shaping

[0078] It adopts air blowing cooling technology with an air temperature of 20℃, a side blowing air velocity of 0.45 m / s, and a relative humidity of 60%.

[0079] Step 4: Wind into the bucket

[0080] The yarn bundle is wound and concentrated using compressed air traction and then fed into the yarn holding drum.

[0081] Step 5: Drawing Process

[0082] The drawing speed was 600 m / min, the drawing ratio was 1.55, and the heating chamber temperature was 160℃.

[0083] Step Six: Curling

[0084] The speed of the winding machine is 4.0 m / s, the main pressure of the winding wheel is 0.35 MPa, and the back pressure is 0.08 MPa.

[0085] Step 7: Apply oil

[0086] The oil spraying process was performed using an oil mist sprayer, with an oil application rate of 0.5%. The oil composition was: 10 wt% silicone oil and 8 wt%...

[0087] Emulsifier, 1 wt% penetrant, the remainder is deionized water.

[0088] Step 8: Heat setting

[0089] The heat setting temperature is 171℃, and the time is 13 minutes.

[0090] Step 9: Cut and package.

[0091] Comparative Example 2

[0092] The difference from Example 1 is that the spinneret is a circular 1800-hole spinneret, and other process parameters are adjusted appropriately according to the fiber production situation.

[0093] Comparative Examples 3-6

[0094] The differences between Comparative Examples 3-6 and Example 1 are shown in Table 5 below.

[0095] Table 5

[0096]

[0097] Detection methods

[0098] The fibers obtained in Examples 1, 2, and 3 were photographed using an optical microscope as shown in the image. Figure 1 , 2 Cross-sectional view of 3.

[0099] The following tests were performed on the ultrafine denier profiled polyester staple fibers prepared in Examples 1-12 and Comparative Examples 1-2:

[0100] 1. Linear density: Measured in accordance with GB / T 14335-2008 standard.

[0101] 2. Cut length and extra-long fiber content: measured in accordance with GB / T 14336-2008 standard.

[0102] 3. Breaking strength and elongation at break: measured in accordance with GB / T 14337-2022 standard, with a tensile speed of 30 mm / min.

[0103] 4. Defect content: Determined in accordance with GB / T 14339-2008 standard.

[0104] 5. Curl count and curl rate: determined in accordance with GB / T 14338-2022 standard.

[0105] 6. Deformity: Measured according to FZ / T 50002-2013 standard.

[0106] 7. Fluffiness: Tested according to FZ / T 50009.4-2019 standard.

[0107] The test results are shown in Table 6 below.

[0108] Table 6

[0109]

[0110] This invention introduces a synergistic parameter control mechanism in key aspects such as fiber raw materials, melt spinning temperature control, spinneret structure, drawing process, crimping treatment, and heat setting. This mechanism significantly improves fiber forming stability, fine denier structure control, and cross-sectional irregularity retention. Test results verify that the invention effectively constructs a synergistic structural system integrating fine denier, irregular shape, and crimp elasticity, significantly improving the fiber's mechanical properties, dimensional uniformity, and fluffy feel.

[0111] Compared with comparative samples that use traditional single-zone temperature control, low-hole spinnerets, or unoptimized heat setting and crimping parameters, the fibers produced by this invention have significant advantages in appearance uniformity, structural integrity, and usability, fully demonstrating the remarkable effect of the technical solution described in this invention in improving the overall performance of products and achieving industrial stability.

[0112] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine denier profiled polyester staple fibers, characterized in that, Includes the following steps: S1 raw material pretreatment: Drying the polyester chips; S2 Melt Spinning: The dried polyester chips are melted sequentially through zones one to six in a screw extruder. The temperature range of zones one to six is ​​280–305℃. Melt spinning is then performed through a spinneret. The spinning box temperature is 285–295℃, the pump supply is 700–840 g / min, the pressure difference between the inlet and outlet air of the annular blower is 580–730 Pa, and the winding speed is 1050–1150 m / min, to obtain ultra-fine denier profiled polyester nascent yarn. S3 nascent yarn treatment: The ultra-fine denier profiled polyester nascent yarn is sequentially bundled, first-stage oil bath drawing, and second-stage drawing; the first-stage oil bath drawing temperature is controlled at 65-70℃, and the second-stage drawing temperature is 100-120℃. S4 Heat Setting and Crimping: The stretched fibers are subjected to tension heat setting and crimping treatments in sequence; S5 Oiling and Cutting: An oiling agent is applied to the surface of the crimped fiber. The fiber is then relaxed, heat-set, dried and cut to obtain ultra-fine denier profiled polyester staple fiber. In the S1 raw material pretreatment step, the polyester chips are high-viscosity polyester chips with an intrinsic viscosity of 0.68 to 0.75 dL / g and a melting point of 257 to 268°C. In the S2 melt spinning step, the temperature of the screw extruder is 280℃~290℃ in zone one, 285℃~295℃ in zone two, 290℃~300℃ in zone three, 295℃~305℃ in zone four, 290℃~300℃ in zone five, and 285℃~295℃ in zone six. In the S2 melt spinning step, the spinneret is selected from one of 4000 holes, 4800 holes, hollow 4400 holes, and cross 4000 holes; In the S3 nascent yarn processing step, the total draw ratio of the primary oil bath draw and the secondary draw is controlled at 3.38 to 3.91 times; In the S4 heat setting and curling steps, the main curling pressure is controlled at 0.36–0.42 MPa, the back pressure is controlled at 0.18–0.22 MPa, and the linear speed of the curling process is 190–210 m / min. In the S4 heat setting and curling step, the heat setting temperature is controlled at 165-175℃. In the S5 oiling and cutting step, the silicone oil component in the applied oil accounts for 7% to 8% of the total mass of the oil.

2. An ultrafine denier shaped polyester staple fiber prepared by the method for preparing ultrafine denier shaped polyester staple fiber according to claim 1, characterized in that, The ultrafine denier shaped polyester staple fiber has a shape degree ≥85%, a hollow fiber hollow rate ≥16%, a fiber linear density of 0.33~0.77dtex, and a compressive elasticity ≥70%.

3. The ultrafine denier profiled polyester staple fiber according to claim 2, characterized in that, The fiber has a breaking strength of 4.0–5.2 cN / dtex, a breaking elongation of 30%–45%, a fiber length of 12 mm–52 mm, an extra-long fiber content of 0–5 mg / 100 g, a defect content of 2–30 mg / 100 g, a crimp number of 9–14 per 25 mm, and a crimp rate of 9%–17%.

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