Staple polyester fiber for sewing thread and method of making same

Abstract

The application discloses polyester staple fiber for sewing thread and a preparation method thereof. The polyester staple fiber has the following aggregation morphology: the number of crimps is 8-20 per 25 mm, the ratio of the crimp degree to the number of crimps CI / CN is 0.70-1.25, the crimp morphology of the single fiber has the morphology characteristics that the crimp wave peak width is large, and the wave peak arrangement is loose and not close, the crimp wave peak includes a type of wave peak and b type of wave peak, the width w of the a type of wave peak is 2.6-6.0 mm, the width w of the b type of wave peak is 0-2.5 mm, the proportion of the a type of wave peak is 70-100%, and the rest is the b type of wave peak; the mass index of the above fiber meets the physical performance mass index of the existing product, and simultaneously has the characteristics of high carding passability and high fiber strength utilization rate; the fiber can improve the spinnability before the production of the polyester sewing thread, and simultaneously improve the fiber strength utilization rate, and the strength utilization coefficient is increased by 5.0-17.6% compared with the previous one.

Description

Technical Field

[0001] This invention relates to a polyester staple fiber and its preparation method, and more particularly to a polyester staple fiber for sewing thread and its preparation method. Background Technology

[0002] Polyester staple fiber is a widely used textile material used to replace natural fibers such as cotton, wool, silk, and linen. It imitates natural fibers in many ways, including in terms of thickness, fineness, length, cross-sectional shape, and internal chemical properties. Natural fibers often have irregular cross-sections, resulting in a non-straight fiber shape with a certain degree of curvature or loops. Polyester staple fiber is made by stretching, setting, crimping, and cutting straight, smooth filaments. The crimping process is designed to mimic the curvature of natural fibers to improve spinning performance.

[0003] Polyester staple fiber used in spinning employs two-dimensional mechanical extrusion crimping, resulting in crimps with regular or irregular serrated shapes. The crimping performance is directly related to spinning performance and yarn strength. Polyester sewing thread is produced from polyester staple fiber through processes such as opening and cleaning, carding, drawing, roving, spinning, and post-processing. The semi-finished polyester staple fiber yarn has a twisted fiber structure; through "twist," friction forces the fibers together in various shapes to form a yarn with a certain strength. When the yarn is stretched, the tensile stress generates lateral pressure between the fibers along the axial direction. This lateral pressure creates friction between the fibers, allowing the yarn to withstand a certain force before breaking. The ratio of force to yarn fineness is the yarn's breaking strength. The breaking strength of staple fiber yarn depends on the properties of the staple fibers that make up the yarn and the spinning technology. According to the national standard GB / T14464-2008, the performance indicators of polyester staple fiber include fineness, breaking strength, breaking elongation, crimp, crimp number, oil content, and resistivity. In our research, we found that for the same type of polyester staple fiber, the fiber fineness, breaking strength, breaking elongation, crimp and crimp number tested according to the national standard GB / T 14464-2008 are basically consistent and all are excellent products. However, there are significant differences in spinnability in the pre-spinning opening and carding processes. This manifests as the fibers being prone to tangling and hitting the hands, clogging the air duct, and tangling with the cylinder and doffer. In terms of yarn quality, the yarn spun from high-strength fibers has low strength, that is, the utilization rate of fiber strength is low.

[0004] Industry experts generally believe that reducing the crimp number and crimp degree of polyester staple fibers can improve the opening and carding throughput during the spinning process and enhance the spinnability of the pre-spinning stage. However, increasing yarn strength requires either increasing the cohesion or strength of the polyester staple fibers. Given that the strength of the polyester staple fibers cannot be improved without altering the oiling agent, increasing the crimp number and crimp degree is typically used to enhance the cohesion. In other words, improving the opening and carding throughput during the spinning process and increasing yarn strength require addressing the inherent contradiction in crimp performance.

[0005] With the continuous development of the domestic sewing thread industry, users' understanding of sewing thread production technology is deepening, and they are placing increasingly higher and more numerous demands on the quality and variety of polyester staple fiber products for sewing thread. Among these, the need to improve the spinnability of polyester staple fiber and increase yarn strength is particularly urgent. Improving the spinnability of staple fiber is beneficial for spinning enterprises to increase production speed, improve production stability, and reduce costs. Improving fiber strength utilization is beneficial for spinning enterprises to produce high-strength yarns, and also for fiber raw material manufacturers to reduce the draft ratio to improve production stability while ensuring the quality of sewing thread products for downstream users (for fiber manufacturers, increasing the stretch ratio in post-drafting is usually used to increase fiber strength; to ensure high breaking strength of polyester staple fiber for sewing thread, a very high draft ratio is used, resulting in more yarn breakage and roller wrapping during production, further making it difficult to control the defect content in the product). Therefore, developing a polyester staple fiber for sewing thread with good spinnability and high fiber strength utilization has become a common need of both the spinning industry and the polyester staple fiber production industry.

[0006] CN101379236B describes a method for manufacturing polyester fibers for air-laid nonwoven fabrics. The main objective of this invention is to provide polyester fibers for air-laid nonwoven fabrics that can produce air-laid nonwoven fabrics with excellent web-forming properties, particularly excellent spinnability of the screen, good texture uniformity, and a fluffy texture. The polyester fibers for air-laid nonwoven fabrics have a fineness of 10.0 dtex or less, a fiber length of 8.0 mm or more, a crimp count of 8.5 crimps / 25 mm or more, a crimp rate / crimp count of 0.65 or less, and a crimp elasticity of 70% or more. The fiber-forming resin is a polyester in which at least 80 mol% of the total repeating units are alkyl terephthalate repeating units. The invention is characterized by subjecting unstretched yarn drawn at a spinning speed of 1500 m / min or less to a low-ratio stretch of 0.60 to 1.20 times at a temperature 10°C or higher than the glass transition temperature of the polyester, while simultaneously performing a fixed-length heat treatment. This invention is an air-laid web forming process, applied to air-laid nonwoven fabrics. It does not require the strength of the web, and its requirements for the quality and performance of the fiber raw materials and the quality control of the final product are different from those of this invention.

[0007] CN202080015681.2 discloses a polyester fiber with curls, a method for manufacturing the same, a pile fabric containing the fiber, and a method for manufacturing the pile fabric. This invention relates to a polyester fiber with curls, the curl shape of which changes through a 10-minute dry heat treatment at 150°C. It provides a polyester fiber with good carding machine passability, and a method for manufacturing a pile fabric with a natural fur-like curl on the vertical surface layer of the pile fabric after a low-temperature polishing treatment at 90°C to 160°C. The invention also describes a method for manufacturing a pile fabric using the polyester fiber. Before the dry heat treatment, the fiber has a primary curl count of 5 to 30 curls per 25mm, and after the dry heat treatment, it has a secondary curl count of 0 to 1 curl per 25mm. Figure 1 and attached Figure 2 The figures illustrate primary and secondary crimping, and also illustrate the appearance evaluation criteria for pile fabrics. As shown in the figures, the primary crimping described in this invention is the two-dimensional serrated crimping characteristic of conventional polyester staple fibers, while the secondary crimping after dry heat treatment is a three-dimensional spiral crimping. Its characteristic is good carding performance. However, the morphological requirements and functions of the two-dimensional crimping are not mentioned.

[0008] 201710112617.6 A method for producing pure polyester colored yarn is disclosed, comprising the following steps: colorless polyester staple fiber and colorful differentiated polyester staple fiber are respectively processed through opening and cleaning processes and carding to produce colorless polyester sliver and colorful differentiated polyester staple fiber sliver; three colorless polyester staple fiber slivers and three colorful differentiated polyester staple fiber slivers are processed through three drawing processes to produce mixed slivers; two mixed slivers are simultaneously fed into a roving frame and processed into mixed roving through a roving process; two mixed rovings are fed into a spinning frame by Sirospinning and processed into pure polyester colored yarn through a spinning process.

[0009] CN101501258A describes a weft elastic interlining and its manufacturing method. This invention relates to an elastic interlining that does not impair smoothness and has a weft elongation of 8% or more. It uses polyester or cellulose long fibers with a twist coefficient (K) of 2000-15000 as warp yarns and substantially untwisted polyester or cellulose long fibers as weft yarns. The monofilaments of the warp fibers are bundled together to create a circular cross-sectional shape. Furthermore, by increasing the bending stiffness of the warp yarns relative to the weft yarns, the weft yarns of the fabric can be easily imparted with a crimp rate. As shown in the accompanying drawings, the weft yarns of this invention are straight filaments, and their crimp rate is a bend formed after weaving due to the presence of the warp yarns. Summary of the Invention

[0010] Purpose of the invention: The present invention aims to provide a polyester staple fiber for sewing thread that simultaneously possesses high carding permeability and high fiber strength utilization rate; another purpose of the present invention is to provide a method for preparing polyester staple fiber for sewing thread that can improve the spinnability of polyester sewing thread before production, that is, improve the carding permeability and operational stability of the pre-spinning blending, opening and cleaning, and carding processes, while improving the fiber strength utilization rate.

[0011] Technical Solution: The polyester staple fiber for sewing thread described in this invention has the following aggregation morphology: 8-20 crimps / 25mm, and the ratio of crimp degree to crimp number (CI / CN) is between 0.70 and 1.25; each fiber has a morphological characteristic of large crimp peak width and loose peak arrangement, wherein the crimp peaks include type a peaks and type b peaks, the width w of type a peaks is 2.6-6.0mm, and the width w of type b peaks is 0-2.5mm; type a peaks account for 70-100%, and the remainder are type b peaks.

[0012] Preferably, the polyester staple fiber for sewing thread has the following aggregation morphology: 9.8-15 crimps / 25mm, and the ratio of crimp degree to crimp number CI / CN is in the range of 0.84 to 0.91.

[0013] Preferably, the polyester staple fiber for sewing thread has the following aggregation morphology: the width w of the type a crest in the single fiber is 3.0-5.0 mm.

[0014] The method for preparing the polyester staple fiber for sewing thread includes the following steps:

[0015] PTA as a dicarboxylic acid and EG as a diol are used for esterification reaction. Inorganic particle additives are added, and polyester is obtained by polycondensation under the catalysis of a catalyst. The polyester staple fiber is spun using a polyester staple fiber spinning process. The spun raw yarn is bundled, pre-tensioned, and then subjected to primary water bath drawing followed by humidification and heating, then secondary drawing, setting, crimping, and cutting to produce the final product. The resulting fiber is then tested and characterized. The polyester staple fiber for sewing thread prepared by this invention has mechanical extrusion two-dimensional crimping, forming it in one step during the fiber production process without any dry heat treatment. The polyester staple fibers for sewing thread prepared by this invention have different "aggregation morphologies". The "aggregation morphology" controlled by the production process has special requirements for fiber crimp morphology, crimp number, and crimp degree. The crimp morphology is characterized by a large crimp peak width and a loose and non-dense crimp peak arrangement. At the same time, it requires a crimp number of 8-20 / 25mm, a crimp degree of 8-20%, and a crimp degree to crimp number ratio CI / CN ranging from 0.70 to 1.25. By controlling the crimp morphology, the contradictory needs of improving the spinnability of polyester sewing thread before production and simultaneously improving the utilization rate of fiber strength are met.

[0016] Preferably, the inorganic particles are at least one of kaolin, calcium carbonate, barium sulfate, titanium dioxide, or silicon dioxide.

[0017] Preferably, the catalyst is an antimony-based catalyst, a titanium-based catalyst, a composite catalyst of antimony and titanium, an aluminum-based catalyst, or a germanium-based catalyst.

[0018] Preferably, in the post-processing curling process, the curling density is controlled to be 0.7-1.0 kiloden denier, the main curling pressure is 0.2-0.6 MPa, and the back pressure is 0.15-0.4 MPa.

[0019] Preferably, the curling temperature in the post-processing curling process is 60-110℃, and the curling speed is 220-380m / min.

[0020] Preferably, the primary water bath stretching is followed by heating to a temperature of 95-110°C.

[0021] Preferably, the drawing temperature of the first-stage water bath drawing is 50-60℃ and the drawing ratio is 2.6-3.5; the drawing temperature of the second-stage drawing is 160-200℃ and the drawing ratio is 1.10-1.30.

[0022] The improved spinnability of fibers in this invention is characterized by the waste rate and sliver cohesion during the carding and combing process at the same machine speed. A higher waste rate indicates greater damage to the fibers during the opening and combing process, resulting in poorer carding throughput; conversely, a lower waste rate indicates better throughput. Within a certain range, a lower sliver cohesion indicates higher fiber parallelism and straightness within the sliver, further improving carding throughput. The fiber strength utilization rate is the ratio of sewing thread yarn strength to fiber strength. A higher ratio indicates that higher-strength sewing thread can be produced using lower-strength fibers, and sewing thread with the same strength fibers has higher strength. Since polyester fiber production typically increases fiber strength by increasing the draw ratio, lower fiber strength is beneficial for fiber production, improving the stability of the fiber production process, enhancing fiber quality, and reducing costs.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The polyester short fiber for sewing thread described in the present invention has high combing passability and high fiber strength utilization rate; the strength utilization coefficient of the polyester short fiber for sewing thread prepared by the present invention can be increased by 5.0 to 17.6% compared with the same period last year; (2) The preparation method can effectively improve the spinnability of polyester sewing thread before production, that is, improve the combing passability and operation stability of the pre-spinning blending, opening and cleaning, and carding processes, while improving the fiber strength utilization rate, while the fineness, breaking strength, elongation, dry heat shrinkage rate, oil agent, oil content, ultra-long fiber content, double-length fiber content, defects and other indicators of the fiber can basically be maintained at the original level. Attached Figure Description

[0024] Figure 1 This is a physical characteristic diagram of type a wave peaks;

[0025] Figure 2 This is a physical characteristic diagram of type b wave peaks;

[0026] Figure 3 This is a single fiber morphology diagram of Example 1;

[0027] Figure 4 This is a single fiber morphology diagram from Example 2;

[0028] Figure 5 This is a single fiber morphology diagram of Example 3;

[0029] Figure 6 This is a single fiber morphology diagram of Example 4;

[0030] Figure 7 This is a single fiber morphology diagram of Example 5;

[0031] Figure 8 This is a single fiber morphology diagram of Example 6;

[0032] Figure 9 This is a single fiber morphology diagram from Example 7;

[0033] Figure 10 This is a single fiber morphology diagram of Comparative Example 1;

[0034] Figure 11 This is a single fiber morphology diagram of Comparative Example 2;

[0035] Figure 12 This is a single fiber morphology diagram of Comparative Example 3;

[0036] Figure 13 This is a single fiber morphology diagram of Comparative Example 4;

[0037] Figure 14 This is a single fiber morphology diagram of Comparative Example 5. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0039] Example 1

[0040] A type of polyester staple fiber for sewing thread has a crimp count of 12.6 crimps / 25mm, a crimp degree of 10.6%, a CI / CN ratio of 0.84, and a 90% proportion of type a crimp peaks.

[0041] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0042] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.85 million denier, the coil pressure at 0.35 / 0.15 MPa, the coil temperature at 80℃, and the coil speed at 260 m / min. The resulting fibers have the following properties: Figure 3 The aggregated morphology shown has broad and loose crimp peaks, with a crimp count of 12.6 crimps / 25mm and a crimp degree of 10.63%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.55, and the yarn strength reaches 3.65 cN / dt. In comparison, control sample 1, produced on the same production line, has a crimp density of 0.650,000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 80℃, and a crimp speed of 260 m / min. Its crimp peaks are small and dense, with 0% of type a crimp peaks. It has a higher crimp count and crimp degree, poorer pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.50.

[0043] Example 2

[0044] A type of polyester staple fiber for sewing thread has a crimp count of 11.7 crimps / 25mm, a crimp degree of 9.9%, a CI / CN ratio of 0.85, and a 100% proportion of type a crimp peaks.

[0045] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0046] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalyst catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. After humidification and heating in a steam heating box, secondary drawing is performed in a third drawing machine. The yarns are then set in a tension heat setter, coiled in a stacking machine, a steam preheating box, and a coiling machine, and finally cut by a cooling conveyor, a traction machine, and a cutting machine. The final product is packaged. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.9000 denier, the coil pressure at 0.30 / 0.15 MPa, the coil temperature at 80℃, and the coil speed at 280 m / min. The resulting fibers have the following properties: Figure 4 The aggregated morphology shown has wide and loose crimp peaks, with a crimp count of 11.7 crimps / 25mm and a crimp degree of 9.9%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.57, and the yarn strength reaches 3.47cN / dt. In comparison, control sample 2, produced on the same production line, has a crimp density of 0.65000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 85℃, and a crimp speed of 280m / min. Its crimp peaks are small and dense, with type A crimps accounting for 15%. It has a higher crimp count and crimp degree, poorer pre-spinning combing performance, is prone to clogging the conveyor duct, and has lower yarn strength, with a fiber strength utilization coefficient of only 0.53.

[0047] Example 3

[0048] A type of polyester staple fiber for sewing thread has a crimp count of 14.1 crimps / 25mm, a crimp degree of 12.8%, a CI / CN ratio of 0.91, and a 95% proportion of type a crimp peaks.

[0049] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0050] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalyst catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.85 million denier, the coil pressure at 0.35 / 0.25 MPa, the coil temperature at 80℃, and the coil speed at 280 m / min. The resulting fibers have the following properties: Figure 5 The aggregated morphology shown has broad and loose crimp peaks, with a crimp count of 14.1 crimps / 25mm and a crimp degree of 12.8%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.59, and the yarn strength reaches 3.74cN / dt. In comparison, Comparative Example 3, produced on the same production line, has a crimp density of 0.60000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 85℃, and a crimp speed of 260 m / min. Its crimp peaks are small and dense, with type a crimps accounting for 30%. It has a higher crimp count and crimp degree, poorer pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.53.

[0051] Example 4

[0052] A type of polyester staple fiber for sewing thread has a crimp count of 14.9 crimps / 25mm, a crimp degree of 13.4%, a CI / CN ratio of 0.90, and a 95% proportion of type a crimp peaks.

[0053] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0054] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalyst catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.82 million denier, the coil pressure at 0.35 / 0.15 MPa, the coil temperature at 80℃, and the coil speed at 260 m / min. The resulting fibers have the following properties: Figure 6 The aggregated morphology shown has broad and loose crimp peaks, with a crimp count of 14.9 crimps / 25mm and a crimp degree of 13.8%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.58, and the yarn strength reaches 3.71cN / dt. In comparison, control sample 3, produced on the same production line, has a crimp density of 0.60000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 85℃, and a crimp speed of 260m / min. Its crimp peaks are small and dense, with type A crimps accounting for 30%. It has a higher crimp count and crimp degree, poorer pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.53.

[0055] Example 5

[0056] A type of polyester staple fiber for sewing thread has a crimp count of 13.3 crimps / 25mm, a crimp degree of 11.8%, a CI / CN ratio of 0.89, and a 100% proportion of type a crimp peaks.

[0057] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0058] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for bright polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.85 million denier, the coil pressure at 0.30 / 0.25 MPa, the coil temperature at 80℃, and the coil speed at 260 m / min. The resulting fibers have the following properties: Figure 7 The aggregated morphology shown has broad and loose crimp peaks, with a crimp count of 13.3 crimps / 25mm and a crimp degree of 11.8%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.57, and the yarn strength reaches 3.72cN / dt. In comparison, Comparative Example 4, produced on the same production line, has a crimp density of 0.65000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 80℃, and a crimp speed of 280 m / min. Comparative Example 4 has fine and dense crimp peaks, a higher crimp count and crimp degree, and a 10% proportion of type a crimp peaks. It exhibits poor pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.51.

[0059] Example 6

[0060] A type of polyester staple fiber for sewing thread has a crimp count of 9.8 crimps / 25mm, a crimp degree of 8.9%, a CI / CN ratio of 0.91, and a 98% proportion of type a crimp peaks.

[0061] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0062] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalyst catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.92 million denier, the coil pressure at 0.30 / 0.20 MPa, the coil temperature at 75℃, and the coil speed at 260 m / min. The resulting fibers have the following properties: Figure 8 The aggregated morphology shown has wide and loose crimp peaks, with a crimp count of 9.8 crimps / 25mm and a crimp degree of 8.9%, exhibiting good pre-spinning spinnability. The fiber strength utilization coefficient reaches 0.60, and the yarn strength reaches 3.75cN / dt. In comparison, Comparative Example 4, produced on the same production line, has a crimp density of 0.650,000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 80℃, a crimp speed of 280m / min, and a crimp peak ratio of 10% for type a. The crimp peaks are small and dense, with a higher crimp count and crimp degree, poorer pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.51.

[0063] Example 7

[0064] A type of polyester staple fiber for sewing thread has a crimp count of 18.5 crimps / 25mm, a crimp degree of 14.9%, a CI / CN ratio of 1.24, and a 70% proportion of type a crimp peaks.

[0065] The preparation method of the above-mentioned polyester staple fiber for sewing thread includes the following steps:

[0066] PTA is used as a dicarboxylic acid and EG as a diol for esterification. Before esterification, nano-inorganic particle additives are added, and polyester is obtained through polycondensation under catalyst catalysis. This polyester is then spun using a polyester staple fiber spinning process. The spun yarns are bundled and sequentially passed through a yarn guide machine for pre-tensioning, an oil bath, a first drawing machine, a drawing bath, and a second drawing machine for primary drawing. The yarns are then humidified and heated in a steam heating box, followed by secondary drawing in a third drawing machine. After setting in a tension heat setter, the yarns are coiled using a yarn stacking machine, a steam preheating box, and a coiling machine. Finally, they are cut by a cooling conveyor, a traction machine, a cutting machine, and packaged by a packaging machine. The polymerization and spinning processes are based on existing production methods for glossy polyester staple fibers, as is the post-drawing process. The coil density is controlled at 0.75 million denier, the coil pressure at 0.40 / 0.30 MPa, the coil temperature at 80℃, and the coil speed at 260 m / min. The resulting fibers have the following properties: Figure 9 The aggregated morphology shown has some large and loose crimp peaks, with type a peaks accounting for 70%, a crimp count of 18.5 / 25mm, and a crimp degree of 14.9%. It exhibits good pre-spinning spinnability, a fiber strength utilization coefficient of 0.54, and a yarn strength of 3.56 cN / dt. In comparison, Comparative Example 5, produced on the same production line, has a crimp density of 0.650,000 denier, a crimp pressure of 0.45 / 0.40 MPa, a crimp temperature of 80℃, and a crimp speed of 260 m / min. Its crimp peaks are small and dense, with type a peaks accounting for 50%. It has poor pre-spinning combing performance, lower yarn strength, and a fiber strength utilization coefficient of only 0.51.

[0067] Comparative Example 1

[0068] A type of polyester staple fiber for sewing thread, with a crimp count of 24 / 25mm, a crimp degree of 18.0%, and a CI / CN ratio of 0.75. For example... Figure 10 As shown, this fiber is mainly composed of fine, small curls with sharp crests. It easily tangles and beats the hands when handling cotton, and has poor opening and combing performance.

[0069] Comparative Example 2

[0070] A type of polyester staple fiber for sewing thread, with 21 crimps / 25mm, a crimp degree of 19.1%, and a CI / CN ratio of 0.91. Figure 11 As shown, this fiber has strong adhesion and sticks together badly when shaken, making it difficult to separate. It easily gets tangled, clogs hands, and blocks the conveyor duct.

[0071] Comparative Example 3

[0072] A type of polyester staple fiber for sewing thread has a crimp count of 18.6 crimps / 25mm, a crimp degree of 13.0%, and a CI / CN ratio of 0.70. For example... Figure 12As shown, a small portion of the fiber has a wide, broad crimp, while the majority is composed of small, tightly packed crimps. This results in low yarn strength and a low fiber strength utilization coefficient after carding.

[0073] Comparative Example 4

[0074] A type of polyester staple fiber for sewing thread has a crimp count of 19.1 crimps / 25mm, a crimp degree of 13.4%, and a CI / CN ratio of 0.70. For example... Figure 13 As shown, a small portion of the fiber has a wide, broad crimp, while the majority is composed of small, tightly packed crimps. This results in low yarn strength and a low fiber strength utilization coefficient after carding.

[0075] Comparative Example 5

[0076] A type of polyester staple fiber for sewing thread has a crimp count of 21.6 crimps / 25mm, a crimp degree of 15.0%, and a CI / CN ratio of 1.44. For example... Figure 14 As shown, 50% of the fiber has a wide, broad crimp, while the other 50% consists of small, tightly packed crimps. This can be achieved through carding, but the yarn strength is relatively low, and the fiber strength utilization coefficient is also low.

[0077] Spinning process description: All samples were processed on the same equipment and using the same spinning process.

[0078] (1) Spinning process flow:

[0079] Polyester staple fiber → cleaning and carding process → drawing process → roving process → spinning process

[0080] (2) Main spinning processes

[0081] The Trützschler combing and carding machine (TC5-1 type) controls the test temperature at 22℃~24℃ and the humidity at 60%RH~68%RH during the combing and carding process; the output sliver weight is 4.4ktex, the cotton box pressure is 210pa~235pa, and the cotton layer thickness ICFD is about 0.95mm.

[0082] The Trützschler TD8 drawing frame controls the drawing process at a temperature of 22℃~24℃ and a humidity of 58%RH~65%RH. It employs two drawing passes, with 8 slivers drawn in each pass, and a drawing speed of 400m / min.

[0083] The Tianjin Jiacheng DSro-01 digital roving frame has a test temperature of 26℃~28℃, a humidity of 60%RH~62%RH, a sliver weight of 420tex, and a spindle speed controlled at 500r / min during the roving process.

[0084] The Tianjin Jiacheng DSSP-01 digital sample spinning frame controls the spinning process temperature at 28℃~30℃ and the humidity at 55%RH~63%RH. The twist coefficient is controlled at 340~360, and the spinning speed is controlled at around 11000r / min.

[0085] Yarn performance testing and analysis instruments and methods:

[0086] Under standard temperature and humidity conditions, the yarn is left to acclimate for 24 hours.

[0087] The yarn linear density was tested using a YG086 yarn length measuring machine, and the average value was calculated after multiple measurements.

[0088] The tensile strength and elongation of a single yarn were tested using a YG063T fully automatic single yarn tensile strength tester. The tension coefficient was set to 0.5 cN / tex and the stretching speed to 500 mm / min.

[0089] Fiber testing regulations:

[0090] (1) Sampling regulations

[0091] Sampling shall be performed in accordance with GB / T 14334.

[0092] (2) Fracture strength, elongation at break, strength at 10% constant elongation, coefficient of variation of fracture strength

[0093] Comply with GB / T 14337.

[0094] (3) Linear density deviation rate Q / SH3070 02.21.3—2018

[0095] Perform according to Method A (Weighing Method of Middle Section of Fiber Bundle) in GB / T 14335.

[0096] (4) Length deviation rate, extra-long fiber rate, and double-length fiber content

[0097] Implement in accordance with GB / T 14336.

[0098] (5) Defect content

[0099] Implement in accordance with GB / T 14339.

[0100] (6) Number of curls, curl rate

[0101] The sampling and counting rules have been modified based on the provisions of GB / T 14338.

[0102] (7) Dry heat shrinkage rate at 180℃

[0103] Implement according to FZ / T 50004.

[0104] (8) Specific resistance

[0105] Perform in accordance with GB / T 14342.

[0106] (9) Oil content

[0107] Comply with GB / T 6504.

[0108] Aggregation Morphology: The crimping performance involved in this invention is characterized by the concept of "fiber aggregation morphology" through a combination of concrete and numerical methods. Waves are used to vividly express the overall characteristics of the crimping morphology, and various characteristic peaks of the crimping waves are extracted as local features for identification, judgment, and classification. Improvements are made to address the shortcomings of the current national standard's crimping performance testing methods by automatically quantifying the aggregation morphology. The quantification of "fiber aggregation morphology" utilizes the XQ-1A fiber tensile strength tester. Based on the GB-T14337-2008 test method for the crimping performance of short chemical fibers, improvements are made to the sampling and counting processes. The test samples consist of 10 neatly formed bundles of filaments and 10 loose, fluffy filaments. The crimp count is automatically performed, counting all small bends with indistinct crimps. The crimp degree is calculated by the instrument based on the fiber length under light and heavy loads according to a built-in formula. Light and heavy loads are set according to national standard requirements. The visualization of "fiber aggregation morphology" was achieved by using an XQ-1A fiber tensile strength meter to extract the crimped morphology of individual fibers. Five neatly formed bundles of fibers and five loosely formed filaments were taken, and after applying a tension of 1 cN to each fiber, images of individual fibers were acquired. The crimped images of individual fibers were then merged using image processing technology to obtain the visualization of "fiber aggregation morphology".

[0109] In the embodiments of this application, the white lines in the accompanying figures represent the morphology of a single short fiber randomly selected from neatly arranged bundles of filaments and loosely arranged filaments. Images were acquired after the fibers were kept straight under the same pre-tension and magnified to the same degree. All fiber patterns were only cropped, not scaled, and the size and degree of curl can be compared proportionally.

[0110] The fiber performance results are listed in Table 1, the combing and carding yarn performance is listed in Table 2, and the fine yarn spinning performance is listed in Table 3.

[0111] Table 1 Fiber Properties

[0112]

[0113]

[0114] Table 2 Performance of Carded Yarn

[0115]

[0116] Table 3. Spinning performance of fine yarn

[0117]

Claims

1. A polyester staple fiber for sewing thread, characterized in that, It has the following aggregation morphology: 8-20 crimps / 25mm, and the ratio of crimp degree to crimp number (CI / CN) is between 0.70 and 1.25; the crimp peaks of its single fiber include type a peaks and type b peaks, wherein the width w of type a peaks is 2.6-6.0mm and the width w of type b peaks is 0-2.5mm; type a peaks account for 70-100%, and the remainder are type b peaks.

2. The polyester staple fiber for sewing thread according to claim 1, characterized in that, It exhibits the following aggregation morphology: 9.8-15 curls / 25mm, and the ratio of curl degree to curl number (CI / CN) ranges from 0.84 to 0.

91.

3. The polyester staple fiber for sewing thread according to claim 1, characterized in that, It has the following aggregation morphology: the width w of the type a peak in the single fiber is 3.0-5.0 mm.

4. A method for preparing polyester staple fiber for sewing thread as described in claim 1, characterized in that, Includes the following steps: PTA was used as a dicarboxylic acid and EG as a diol for esterification reaction. Inorganic particle additives were added, and polyester was obtained by polycondensation under the catalysis of a catalyst. The polyester staple fiber was spun, and the spun yarn was bundled. The bundled yarn was pre-tensioned, and after primary water bath stretching, it was humidified and heated, followed by secondary stretching, then shaping, crimping, and cutting to form the final product. The resulting fiber was then tested and characterized by a combination of figurative and numerical methods.

5. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The inorganic particles are at least one of kaolin, calcium carbonate, barium sulfate, titanium dioxide, or silicon dioxide.

6. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The catalyst is an antimony-based catalyst, a titanium-based catalyst, a composite catalyst of antimony and titanium, an aluminum-based catalyst, or a germanium-based catalyst.

7. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, In the post-processing curling process, the curling density is controlled at 0.7-1.0 kiloden denier, the main curling pressure is 0.2-0.6 MPa, and the back pressure is 0.15-0.4 MPa.

8. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The curling temperature in the post-processing curling process is 60-110℃, and the curling speed is 220-380m / min.

9. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The first-stage water bath stretching is followed by heating to a temperature of 95-110℃.

10. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The drawing temperature of the first-stage water bath drawing is 50-60℃, and the drawing ratio is 2.6-3.

5.

11. The method for preparing polyester staple fiber for sewing thread according to claim 4, characterized in that, The secondary drawing temperature is 160-200℃, and the drawing ratio is 1.10-1.30.

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