Methods for preparing back-blown rectifier heating cylinder, hot stretching device, and polyester FDY yarn

Abstract

This invention belongs to the field of filament preparation technology, and relates to a counter-blown rectifier heating cylinder, a hot stretching device, and a method for preparing polyester FDY filament. The counter-blown rectifier heating cylinder includes an outer cylinder, an inner cylinder, and a C-shaped groove. The hot stretching device consists of the aforementioned hot stretching device and a stretching roller, positioned in front of the counter-blown rectifier heating cylinder along the filament bundle running direction. The method for preparing polyester FDY filament includes a hot stretching process, which utilizes the aforementioned hot stretching device. This invention aims to develop a novel hot stretching device that can uniformly heat various types of filaments, reduce filament wear, achieve precise heating control, and improve filament quality and production efficiency in the chemical fiber textile industry.

Description

Technical Field

[0001] This invention belongs to the field of filament preparation technology, and relates to a method for preparing polyester FDY filament, including a blown rectifier heating cylinder, a hot stretching device, and a method for preparing filament. Background Technology

[0002] In the field of chemical fiber textiles, the hot stretching process is a key step affecting the quality and performance of filaments such as polyester FDY yarn. The main purpose of hot stretching is to rearrange the molecular structure of the filaments by heating and stretching them, thereby improving the strength, orientation, and other mechanical properties of the filaments and meeting the quality requirements of different textiles.

[0003] Currently, the heating device commonly used in the hot stretching process is the hot roller. The basic principle of the hot roller heating method is to heat the filament by winding it around the hot roller. Generally, the first hot roller winds the filament five and a half times, and the second hot roller winds it five and a half times for thicker filaments and six and a half times for thinner filaments, depending on the filament thickness. Moreover, the thicker the filament, the higher the temperature of the hot roller. However, this heating method has many drawbacks.

[0004] For porous yarns, due to their structural characteristics, multiple monofilaments are bundled together, resulting in monofilament stacking. During the heating process with the hot roller, heat is first transferred from the outer layer to the inner layer, causing a difference in the amount of heat received by the inner and outer monofilaments, resulting in uneven heating of the entire yarn bundle. This uneven heating affects the overall performance of the yarn, such as causing fluctuations in the yarn's strength and elongation, thus affecting the quality stability of the textile.

[0005] For irregularly shaped yarns, due to their irregular cross-sectional shape, there are heating dead zones during the heating process. The special cross-section of irregularly shaped yarns makes it difficult for heat to be effectively transferred in certain areas, resulting in different temperatures in these areas compared to other parts, and thus preventing uniform heating of the yarn. The existence of heating dead zones will affect the local properties of irregularly shaped yarns, thereby affecting the overall quality and processing performance of the yarn.

[0006] Furthermore, in the hot roller heating method, the filaments are in direct contact with the hot rollers, generating significant friction during winding and operation. This friction not only increases energy consumption but can also lead to filament wear and breakage, affecting the continuity and stability of production. Simultaneously, limited by the structure of the hot rollers and the heating method, it is difficult to achieve flexible and precise heating control for filaments of different specifications and characteristics, failing to meet diverse production needs. For example, the patent with authorization announcement number CN114355851B proposes a method to reduce uneven heating by detecting the heating current of the hot rollers, but this is essentially still a contact heating method (using three heating rollers and one stretching roller for hot stretching). While this method can improve the temperature uniformity at various points on the surface of the hot rollers, it cannot solve the problems of uneven heating of the inner and outer layers of filaments and uneven tension caused by friction when porous filaments and irregularly shaped filaments come into contact with the hot rollers.

[0007] Therefore, developing a heating device that can uniformly heat various types of filaments and solve the problems of uneven heating and easy wear of filaments in existing hot roller heating methods is of great practical significance for improving the quality and production efficiency of filaments in the chemical fiber textile industry. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and to provide a method for preparing a blown rectifier heating cylinder, a hot stretching device, and polyester FDY yarn.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A counter-blown rectifier heating cylinder includes an outer cylinder, an inner cylinder, a C-shaped groove, a spherical pressure stabilizing chamber, and a compressed air pipe;

[0011] Both the outer cylinder and the inner cylinder are closed cylinders at both ends. The inner cylinder is located inside the outer cylinder and the two are coaxial. The bottom of the inner cylinder is in contact with the bottom of the outer cylinder. The height of the inner cylinder is less than the height of the outer cylinder. The outer diameter of the inner cylinder is less than the inner diameter of the outer cylinder. The inner cylinder has uniformly distributed flow-rectifying holes on its wall. The top of the outer cylinder has a hot air inlet.

[0012] Both the C-shaped groove and the spherical pressure stabilizing chamber are located inside the inner cylinder; the C-shaped groove is arranged vertically, with its opening facing away from the spherical pressure stabilizing chamber and a compressed air outlet at the bottom of the groove, which is connected to the spherical pressure stabilizing chamber; one end of the compressed air pipe is connected to the spherical pressure stabilizing chamber, and the other end passes through the inner cylinder and the outer cylinder in sequence;

[0013] The top of the outer cylinder is provided with an upper filament inlet, and the top of the inner cylinder is provided with a lower filament inlet. A vertically arranged guide tube is provided between the top of the outer cylinder and the top of the inner cylinder. The upper filament inlet, the lower filament inlet, the guide tube, and the C-shaped groove correspond one-to-one. The two ends of the guide tube are connected to their corresponding upper filament inlets and lower filament inlets, respectively. The upper filament inlet, the lower filament inlet, and the guide tube are all located directly above the groove space of their corresponding C-shaped groove.

[0014] As a preferred technical solution:

[0015] As described above, the height of the counter-blown rectifier heating cylinder is 160-180mm, the height of the outer cylinder is 19-21mm greater than the height of the inner cylinder, the outer diameter of the inner cylinder is 220-230mm, the inner diameter of the outer cylinder is 23-27mm greater than the outer diameter of the inner cylinder, and the wall thickness of the inner cylinder is 3-5mm.

[0016] As described above, in a counter-blown rectifier heating cylinder, the hot air inlet is coaxial with the outer cylinder.

[0017] The counter-blowing rectifier heating cylinder described above also includes a hot air pipe, which is located outside the outer cylinder and communicates with the hot air inlet.

[0018] In the counter-blown rectifier heating cylinder described above, the vertical central axis of the spherical pressure stabilizing chamber coincides with the central axis of the inner cylinder.

[0019] As described above, the counter-blown rectifier heating cylinder has 20-24 C-shaped grooves, all of which are evenly distributed around the vertical central axis of the spherical pressure stabilizing chamber.

[0020] As described above, in a counter-blown rectifier heating cylinder, each C-shaped groove has 8-10 compressed air outlets, arranged vertically with spacing between them. The distance between two adjacent compressed air outlets is 10-12% of the length of the C-shaped groove. The length of the C-shaped groove is 12-15% of the height of the inner cylinder. The cross-section of the C-shaped groove is an arc with a central angle greater than or equal to 250° and less than or equal to 270°. The distance between the C-shaped groove and the top of the inner cylinder is 38-40% of the height of the inner cylinder. The distance between the C-shaped groove and the cylinder wall of the inner cylinder is 15-18% of the inner diameter of the inner cylinder.

[0021] As described above, in a counter-blown rectifier heating cylinder, the central axis of the compressed air tube coincides with the vertical central axis of the spherical pressure stabilizing chamber, and the compressed air tube passes through the hot air inlet with a gap between them.

[0022] The present invention also provides a hot stretching device, comprising a counter-blowing rectifier heating cylinder as described in any of the preceding claims and a stretching roller. Along the direction of the filament bundle running, the stretching roller is located in front of the counter-blowing rectifier heating cylinder. The filament first passes through the counter-blowing rectifier heating cylinder and is then stretched by a stretching roller. Compared with the hot roller heating method, this method can significantly reduce the contact between the filament and each roller.

[0023] The present invention also provides a method for preparing polyester FDY yarn, including a hot stretching process, wherein the hot stretching is performed using a hot stretching device as described above.

[0024] As a preferred technical solution:

[0025] The preparation method of polyester FDY yarn as described above has the following process flow: metering pump metering → component distribution extrusion (spinneret holes are distributed in concentric circles) → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching → second comb guide → main networker → winding and forming.

[0026] The spinning process parameters include: spinning temperature 294-296℃, cooling air pressure 18-21Pa, oil rack height 600-750mm, and oil content 1.03-1.25%;

[0027] The winding process parameters include: hot stretching speed 3680-4350m / min, hot stretching temperature 110-120℃, winding speed 3600-4200m / min, pre-network pressure 0.07-0.09bar, and main network pressure 0.35-0.45bar.

[0028] The specifications of polyester FDY yarn are 33-111 dtex / 72-288f, and the cross-sectional shape of the monofilament is circular, straight, cross-shaped or I-shaped; the tensile strength of polyester FDY yarn is 3.55-4.32 cN / dtex, the tensile strength uniformity CV value is 2.07-3.12%, the tensile elongation at break is 22.1-40.6%, the tensile elongation uniformity CV value is 3.3-5.6%, and the yarn evenness CV value is 0.72-1.4%.

[0029] Beneficial effects:

[0030] (1) The blow-forming heating cylinder uses compressed air to disperse the filament bundle, creating gaps between the filaments so that hot air can enter and heat the filaments. Compared with the uneven heating caused by the heat being transferred from the outer layer filament to the inner layer filament during traditional hot roller heating, this invention can achieve efficient and uniform heating, effectively reducing fluctuations in filament strength, elongation and other indicators, and improving the quality stability of polyester FDY filament.

[0031] (2) The non-contact counter-blowing rectifier heating method is adopted, which avoids direct contact between the filament and the hot roller, reduces the problem of filament wear and breakage caused by friction, and ensures the continuity and stability of production.

[0032] (3) A spherical pressure stabilizing chamber is set in the blow-rectifier heating cylinder, which can make the heating air blown to the yarn uniform and stable, further improve the heating effect, and optimize the performance index of polyester FDY yarn.

[0033] (4) The hot stretching device and preparation method of the present invention can be applied to polyester FDY yarn of various specifications, or even shaped yarn, to meet different production needs. Attached Figure Description

[0034] Figures 1-3 This is a schematic diagram of the counter-blown rectifier heating cylinder. Figure 1 This is a top view. Figure 2 This is a side view. Figure 3 This is an exploded view;

[0035] Figure 4 A schematic diagram showing the connection relationship between the spherical pressure stabilizing chamber, the compressed air pipe, and the C-shaped groove;

[0036] Among them, 6.1-C-shaped groove, 6.2-compressed air pipe, 6.3-hot air pipe, 6.5-spherical pressure stabilizing chamber, 6.6-outer cylinder, 6.7-inner cylinder, 6.8-guide wire tube. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0039] Intrinsic viscosity: According to GB / T 14190-2017 Test method for fiber grade polyester chips, the capillary viscometer method was used to determine the outflow time of solvent and PET solution with a concentration of 0.005 g / mL at 25℃. The intrinsic viscosity was calculated based on the measured outflow time and the solution concentration of the sample.

[0040] Fracture strength, fracture strength uniformity CV value, elongation at break, and elongation at break CV value: tested using a Swiss Uster-Ⅳ tensile strength tester according to GB / T 14344-2022.

[0041] Unevenness coefficient (CV): Tested using a Swiss USTER-IV evenness tester according to GB / T 8960-2015.

[0042] A thermal stretching device, comprising a counter-blown rectifier heating cylinder and a stretching roller;

[0043] like Figures 1-3 As shown, the counter-blowing rectifier heating cylinder includes an outer cylinder 6.6, an inner cylinder 6.7, a C-shaped groove 6.1, a spherical pressure stabilizing chamber 6.5, a compressed air pipe 6.2, and a hot air pipe 6.3;

[0044] Both the outer cylinder 6.6 and the inner cylinder 6.7 are closed cylinders at both ends. The inner cylinder 6.7 is located inside the outer cylinder 6.6 and the two are coaxial. The bottom of the inner cylinder 6.7 is in contact with the bottom of the outer cylinder 6.6. The height of the inner cylinder 6.7 is less than the height of the outer cylinder 6.6. The outer diameter of the inner cylinder 6.7 is less than the inner diameter of the outer cylinder 6.6. The inner cylinder 6.7 has uniformly distributed flow-rectifying holes on its wall. The top of the outer cylinder 6.6 has a hot air inlet, which is coaxial with the outer cylinder 6.6.

[0045] Both the C-shaped grooves 6.1 and the spherical pressure-stabilizing chambers 6.5 are located inside the inner cylinder 6.7, and the vertical central axis of the spherical pressure-stabilizing chambers 6.5 coincides with the central axis of the inner cylinder 6.7; the number of C-shaped grooves 6.1 is 20-24, such as... Figure 4As shown, the cross-section of the C-shaped groove 6.1 is a superior arc, and all the C-shaped grooves 6.1 are evenly distributed around the vertical central axis of the spherical pressure regulating chamber 6.5; the C-shaped grooves 6.1 are arranged vertically, with their openings facing away from the spherical pressure regulating chamber 6.5, and the bottom of the grooves is provided with compressed air outlets, which are connected to the spherical pressure regulating chamber 6.5. The compressed air outlets on each C-shaped groove 6.1 are arranged at intervals along the vertical direction; as shown... Figure 2 As shown, one end of the compressed air pipe 6.2 is connected to the spherical pressure stabilizing chamber 6.5, and the other end passes through the inner cylinder 6.7 and the outer cylinder 6.6 in sequence; the central axis of the compressed air pipe 6.2 coincides with the vertical central axis of the spherical pressure stabilizing chamber 6.5, and the compressed air pipe 6.2 passes through the hot air inlet with a gap between it and the hot air inlet;

[0046] like Figure 3 As shown, the top of the outer cylinder 6.6 is provided with an upper filament inlet, the top of the inner cylinder 6.7 is provided with a lower filament inlet, and a vertically arranged guide tube 6.8 is provided between the top of the outer cylinder 6.6 and the top of the inner cylinder 6.7. The upper filament inlet, the lower filament inlet, the guide tube 6.8, and the C-shaped groove 6.1 correspond one-to-one. The two ends of the guide tube 6.8 are connected to their corresponding upper filament inlets and lower filament inlets, respectively. The upper filament inlet, the lower filament inlet, and the guide tube 6.8 are all located directly above the groove space of their corresponding C-shaped groove 6.1.

[0047] like Figure 2 and Figure 3 As shown, the hot air duct 6.3 is located outside the outer cylinder 6.6 and is connected to the hot air inlet;

[0048] Along the direction of filament travel, the stretching roller is located in front of the counter-blowing rectifier heating cylinder;

[0049] When using this device for hot stretching, the filament bundle enters from the upper filament bundle inlet at the top of the outer cylinder 6.6, passes through the corresponding guide tube 6.8, and exits from the lower filament bundle inlet at the top of the inner cylinder 6.7, entering the area above the corresponding C-shaped groove 6.1. At this time, hot air enters the device through the hot air pipe 6.3 and the hot air inlet in sequence; part of the hot air enters the space between the inner cylinder 6.7 and the outer cylinder 6.6, and the other part of the hot air heats the compressed air entering the spherical pressure stabilizing chamber 6.5 from the compressed air pipe 6.2; the heated compressed air is blown out from the compressed air outlet at the bottom of the C-shaped groove 6.1, and the blown compressed air disperses the filament bundle, creating gaps between the filaments; while the hot air entering the space between the inner cylinder 6.7 and the outer cylinder 6.6 enters the interior of the inner cylinder 6.7 through the evenly distributed rectifier holes on the cylinder wall of the inner cylinder 6.7. This hot air can enter the gaps between the filaments, and together with the hot compressed air blown out from the compressed air outlet, achieves uniform heating of the filament bundle.

[0050] Example 1

[0051] A method for preparing polyester FDY yarn, the specific steps of which are as follows:

[0052] (1) Preparation of polyester melt;

[0053] The process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt (intrinsic viscosity is 0.64 dL / g);

[0054] The relevant process parameters are as follows: slurry level 70%, PTA mass in slurry accounts for 70% of the total mass of PTA and EG; first esterification temperature 263℃, first esterification pressure 55kPa, second esterification temperature 265℃, second esterification pressure 15kPa, prepolymerization upper chamber temperature 273℃, prepolymerization upper chamber pressure 12kPa, prepolymerization lower chamber temperature 275℃, prepolymerization lower chamber pressure 1kPa, final polymerization inlet temperature 278℃, final polymerization outlet temperature 281℃, final polymerization vacuum degree 140Pa;

[0055] (2) Preparation of polyester FDY yarn;

[0056] The process flow is as follows: polyester melt → booster pump → metering pump → component distribution extrusion (spinnerets are distributed in concentric circles) → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching (using a hot stretching device as described above) → second comb guide → main networker → winding.

[0057] The spinning process parameters are as follows: spinning temperature 296℃, no-wind zone height 20mm, cooling air temperature 21℃, cooling air humidity 86%, cooling air pressure 18Pa, oil rack height 750mm, and oil content 1.25%.

[0058] Dimensional parameters of the hot stretching device: Inner cylinder height is 160mm, outer cylinder height is 19mm greater than inner cylinder height, inner cylinder outer diameter is 220mm, outer cylinder inner diameter is 27mm greater than inner cylinder outer diameter, inner cylinder wall thickness is 3mm, number of C-grooves is 20, C-groove length is 12% of inner cylinder height, number of compressed air outlets on each C-groove is 8, distance between two adjacent compressed air outlets on each C-groove is 12% of C-groove length, central angle of the dominant arc cross-section of the C-groove is 250°, distance between the C-groove and the top of the inner cylinder is 38% of inner cylinder height, distance between the C-groove and the inner cylinder wall is 18% of inner cylinder inner diameter;

[0059] The winding process parameters are: hot stretching speed 3680 m / min, hot stretching temperature 110℃, winding speed 3600 m / min, pre-network pressure 0.07 bar, and main network pressure 0.35 bar.

[0060] The final polyester FDY yarn has a specification of 111 dtex / 288f and a single filament cross-sectional shape of I-shape. The tensile strength of the polyester FDY yarn is 3.85 cN / dtex, the tensile strength unevenness CV value is 2.07%, the tensile elongation is 26.8%, the tensile elongation unevenness CV value is 4.5%, and the yarn evenness CV value is 0.81%.

[0061] Example 2

[0062] A method for preparing polyester FDY yarn, the specific steps of which are as follows:

[0063] (1) Preparation of polyester melt;

[0064] The process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt (intrinsic viscosity is 0.65 dL / g);

[0065] The relevant process parameters are as follows: slurry level 70%, PTA mass in slurry accounts for 70% of the total mass of PTA and EG; first esterification temperature 262℃, first esterification pressure 60kPa, second esterification temperature 263℃, second esterification pressure 17kPa, prepolymerization upper chamber temperature 272.5℃, prepolymerization upper chamber pressure 11kPa, prepolymerization lower chamber temperature 274℃, prepolymerization lower chamber pressure 1.2kPa, final polymerization inlet temperature 277℃, final polymerization outlet temperature 280℃, final polymerization vacuum degree 148Pa;

[0066] (2) Preparation of polyester FDY yarn;

[0067] The process flow is as follows: polyester melt → booster pump → metering pump → component distribution extrusion (spinnerets are distributed in concentric circles) → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching (using a hot stretching device as described above) → second comb guide → main networker → winding.

[0068] The spinning process parameters are as follows: spinning temperature 295℃, no-wind zone height 25mm, cooling air temperature 20℃, cooling air humidity 83%, cooling air pressure 19Pa, oil rack height 700mm, and oil content 1.2%.

[0069] Dimensional parameters of the hot stretching device: Inner cylinder height is 170mm, outer cylinder height is 20mm greater than inner cylinder height, inner cylinder outer diameter is 225mm, outer cylinder inner diameter is 26mm greater than inner cylinder outer diameter, inner cylinder wall thickness is 4mm, number of C-grooves is 20, C-groove length is 13% of inner cylinder height, number of compressed air outlets on each C-groove is 9, distance between two adjacent compressed air outlets on each C-groove is 11.5% of C-groove length, central angle of the C-groove's major arc cross-section is 260°, distance between the C-groove and the top of the inner cylinder is 39% of inner cylinder height, distance between the C-groove and the inner cylinder wall is 17% of inner cylinder inner diameter;

[0070] The winding process parameters are: hot stretching speed 4000m / min, hot stretching temperature 112℃, winding speed 3700m / min, pre-network pressure 0.08bar, and main network pressure 0.39bar.

[0071] The final polyester FDY yarn has a specification of 83 dtex / 144f and a cross-shaped monofilament cross section. The tensile strength of the polyester FDY yarn is 4.01 cN / dtex, the tensile strength uniformity CV value is 2.13%, the tensile elongation is 28.6%, the tensile elongation uniformity CV value is 4.2%, and the yarn evenness CV value is 0.79%.

[0072] Example 3

[0073] A method for preparing polyester FDY yarn, the specific steps of which are as follows:

[0074] (1) Preparation of polyester melt;

[0075] The process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt (intrinsic viscosity is 0.66 dL / g);

[0076] The relevant process parameters are as follows: slurry level 70%, PTA mass in slurry accounts for 70% of the total mass of PTA and EG; first esterification temperature 261℃, first esterification pressure 62kPa, second esterification temperature 262.5℃, second esterification pressure 18kPa, prepolymerization upper chamber temperature 272℃, prepolymerization upper chamber pressure 10kPa, prepolymerization lower chamber temperature 274℃, prepolymerization lower chamber pressure 1.35kPa, final polymerization inlet temperature 276.5℃, final polymerization outlet temperature 279℃, final polymerization vacuum degree 150Pa;

[0077] (2) Preparation of polyester FDY yarn;

[0078] The process flow is as follows: polyester melt → booster pump → metering pump → component distribution extrusion (spinnerets are distributed in concentric circles) → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching (using a hot stretching device as described above) → second comb guide → main networker → winding.

[0079] The spinning process parameters are as follows: spinning temperature 295℃, no-wind zone height 30mm, cooling air temperature 19℃, cooling air humidity 81%, cooling air pressure 20Pa, oil rack height 650mm, and oil content 1.1%.

[0080] Dimensional parameters of the hot stretching device: Inner cylinder height is 175mm, outer cylinder height is 20.5mm greater than inner cylinder height, inner cylinder outer diameter is 225mm, outer cylinder inner diameter is 25mm greater than inner cylinder outer diameter, inner cylinder wall thickness is 4mm, number of C-grooves is 24, C-groove length is 14% of inner cylinder height, number of compressed air outlets on each C-groove is 9, distance between two adjacent compressed air outlets on each C-groove is 11% of C-groove length, central angle of the dominant arc cross-section of the C-groove is 265°, distance between the C-groove and the top of the inner cylinder is 39.5% of inner cylinder height, distance between the C-groove and the inner cylinder wall is 16% of inner cylinder inner diameter;

[0081] The winding process parameters are: hot stretching speed 4200 m / min, hot stretching temperature 115℃, winding speed 4000 m / min, pre-network pressure 0.085 bar, and main network pressure 0.41 bar.

[0082] The final polyester FDY yarn has a specification of 51 dtex / 72f and a single filament cross-sectional shape of I-beam. The tensile strength of the polyester FDY yarn is 4.16 cN / dtex, the tensile strength unevenness CV value is 2.41%, the tensile elongation is 31.2%, the tensile elongation unevenness CV value is 4%, and the yarn evenness CV value is 0.78%.

[0083] Example 4

[0084] A method for preparing polyester FDY yarn, the specific steps of which are as follows:

[0085] (1) Preparation of polyester melt;

[0086] The process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt (intrinsic viscosity is 0.67 dL / g);

[0087] The relevant process parameters are as follows: slurry level 70%, PTA mass in slurry accounts for 70% of the total mass of PTA and EG; first esterification temperature 258℃, first esterification pressure 65kPa, second esterification temperature 260℃, second esterification pressure 20kPa, prepolymerization upper chamber temperature 271℃, prepolymerization upper chamber pressure 9.5kPa, prepolymerization lower chamber temperature 273℃, prepolymerization lower chamber pressure 1.5kPa, final polymerization inlet temperature 275℃, final polymerization outlet temperature 278℃, final polymerization vacuum degree 155Pa;

[0088] (2) Preparation of polyester FDY yarn;

[0089] The process flow is as follows: polyester melt → booster pump → metering pump → component distribution extrusion (spinnerets are distributed in concentric circles) → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching (using a hot stretching device as described above) → second comb guide → main networker → winding.

[0090] The spinning process parameters are as follows: spinning temperature 294℃, windless zone height 40mm, cooling air temperature 18℃, cooling air humidity 80%, cooling air pressure 21Pa, oil rack height 600mm, and oil content 1.03%.

[0091] Dimensional parameters of the hot stretching device: Inner cylinder height is 180mm, outer cylinder height is 21mm greater than inner cylinder height, inner cylinder outer diameter is 230mm, outer cylinder inner diameter is 23mm greater than inner cylinder outer diameter, inner cylinder wall thickness is 5mm, number of C-grooves is 24, C-groove length is 15% of inner cylinder height, number of compressed air outlets on each C-groove is 10, spacing between two adjacent compressed air outlets on each C-groove is 10% of C-groove length, central angle of the dominant arc cross-section of the C-groove is 270°, distance between the C-groove and the top of the inner cylinder is 40% of inner cylinder height, distance between the C-groove and the inner cylinder wall is 15% of inner cylinder inner diameter;

[0092] The winding process parameters are: hot stretching speed 4350 m / min, hot stretching temperature 120℃, winding speed 4200 m / min, pre-network pressure 0.09 bar, and main network pressure 0.45 bar.

[0093] The final polyester FDY yarn has a specification of 33dtex / 72f and a circular cross-sectional shape. The tensile strength of the polyester FDY yarn is 4.32cN / dtex, the tensile strength uniformity CV value is 2.65%, the tensile elongation is 34.3%, the tensile elongation uniformity CV value is 3.3%, and the yarn evenness CV value is 0.72%.

[0094] Example 5

[0095] A method for preparing polyester FDY yarn differs from Example 1 only in that the central angle of the superior arc cross-section of the C-shaped groove is 240°.

[0096] The final polyester FDY yarn has a breaking strength of 3.55 cN / dtex, a breaking strength uniformity CV value of 3.12%, a breaking elongation of 22.1%, a breaking elongation uniformity CV value of 5.6%, and a yarn evenness CV value of 1.31%.

[0097] Compared to Example 1, the polyester FDY yarn obtained in Example 5 showed decreased breaking strength and elongation at break, while increased values ​​for unevenness in breaking strength (CV), unevenness in elongation at break (CV), and unevenness in yarn evenness (CV). This is because the central angle of the C-groove's superior arc cross-section in Example 5 is relatively small, easily creating radial obstruction to the outflow of heating air, thus generating eddies, leading to overheating and uneven heating of the yarn. Specifically, the porous linear yarn has a large number of filaments, and the eddies worsen the cohesion between the filaments, exacerbating uneven heating during the drawing process. Simultaneously, the smaller central angle reduces the efficiency of hot air exhaust, causing hot air to accumulate within the C-groove, resulting in overheating of the yarn, uneven drawing, and ultimately an increased value for unevenness in yarn evenness (CV). In addition, excessive heating can cause thermal degradation of polymer chains, which reduces the molecular weight and directly weakens the fiber's breaking strength, resulting in reduced breaking strength and increased breaking strength unevenness CV value. Furthermore, excessive heating can make the filaments brittle and easy to break, thereby causing a decrease in elongation and an increase in elongation unevenness CV value.

[0098] Example 6

[0099] A method for preparing polyester FDY yarn differs from Example 4 only in that the central angle of the superior arc cross-section of the C-shaped groove is 280°.

[0100] The final polyester FDY yarn has a breaking strength of 3.91 cN / dtex, a breaking strength unevenness CV value of 3.12%, a breaking elongation of 40.6%, a breaking elongation unevenness CV value of 4.8%, and a yarn evenness CV value of 1.4%.

[0101] Compared to Example 4, Example 6 showed a decrease in the breaking strength of the polyester FDY yarn, while the values ​​of breaking strength unevenness (CV), breaking elongation, breaking elongation unevenness (CV), and evenness unevenness (CV) increased. This is because the central angle of the C-groove's superior arc cross-section in Example 6 was larger, leading to faster loss of heating air and insufficient fiber heating. Insufficient heating resulted in lower fiber crystallinity and orientation, and a looser molecular chain arrangement, leading to a decrease in breaking strength and exacerbating fluctuations in breaking strength, thus increasing the breaking strength unevenness (CV). Furthermore, insufficient heating caused uneven stress between the yarn sheath and core during stretching, further increasing the evenness unevenness (CV). Additionally, insufficient heating significantly increased the plastic deformation of the yarn during stretching, manifested as an increase in breaking elongation; however, excessively high breaking elongation exacerbated tension fluctuations during stretching, resulting in a larger breaking elongation unevenness (CV).

[0102] Comparative Example 1

[0103] A method for preparing polyester FDY yarn differs from Example 1 only in that the hot stretching uses 3 heating rollers and 1 stretching roller.

[0104] The final polyester FDY yarn has a breaking strength of 2.95 cN / dtex, a breaking strength unevenness CV value of 4.32%, a breaking elongation unevenness CV value of 7.6%, and a yarn evenness CV value of 1.71%.

[0105] Compared to Example 1, the polyester FDY yarn obtained in Comparative Example 1 showed a significant decrease in breaking strength, and a significant increase in the CV values ​​for breaking strength unevenness, breaking elongation unevenness, and evenness. This is because in Comparative Example 1, when hot-stretching was performed using three heating rollers and one stretching roller, the yarn needed to frequently contact the three heating rollers. Given the large number of monofilaments in this polyester FDY yarn, the friction between the outer monofilaments and the yarn path was relatively high. The oil on the yarn surface adhered to and degraded on the heating roller surface, forming dirt. When the yarn reached the dirt area, insufficient heating occurred; simultaneously, the heating rate of the outer monofilaments was faster than that of the inner monofilaments, leading to uneven heating between the inner and outer monofilaments, and consequently, uneven stretching. These factors combined to ultimately reduce the breaking strength, while significantly increasing the CV values ​​for breaking strength unevenness, breaking elongation unevenness, and evenness.

Claims

1. A counter-blown rectifier heating cylinder, characterized in that, It includes an outer cylinder (6.6), an inner cylinder (6.7), a C-shaped groove (6.1), a spherical pressure stabilizing chamber (6.5), and a compressed air pipe (6.2); Both the outer cylinder (6.6) and the inner cylinder (6.7) are closed cylinders at both ends. The inner cylinder (6.7) is located inside the outer cylinder (6.6) and the two are coaxial. The bottom of the inner cylinder (6.7) is in contact with the bottom of the outer cylinder (6.6). The height of the inner cylinder (6.7) is less than the height of the outer cylinder (6.6). The outer diameter of the inner cylinder (6.7) is less than the inner diameter of the outer cylinder (6.6). The inner cylinder (6.7) has uniformly distributed flow-rectifying holes on its wall. The top of the outer cylinder (6.6) has a hot air inlet, which is coaxial with the outer cylinder (6.6). Both the C-shaped groove (6.1) and the spherical pressure stabilizing chamber (6.5) are located inside the inner cylinder (6.7); the vertical central axis of the spherical pressure stabilizing chamber (6.5) coincides with the central axis of the inner cylinder (6.7); the C-shaped groove (6.1) is arranged vertically, with its opening facing away from the spherical pressure stabilizing chamber (6.5) and a compressed air outlet at the bottom of the groove, which is connected to the spherical pressure stabilizing chamber (6.5); one end of the compressed air pipe (6.2) is connected to the spherical pressure stabilizing chamber (6.5), and the other end passes through the inner cylinder (6.7) and the outer cylinder (6.6) in sequence; the central axis of the compressed air pipe (6.2) coincides with the vertical central axis of the spherical pressure stabilizing chamber (6.5), and the compressed air pipe (6.2) passes through the hot air inlet with a gap between it and the hot air inlet; The top of the outer cylinder (6.6) is provided with an upper filament inlet, and the top of the inner cylinder (6.7) is provided with a lower filament inlet. A vertically arranged guide tube (6.8) is provided between the top of the outer cylinder (6.6) and the top of the inner cylinder (6.7). The upper filament inlet, the lower filament inlet, the guide tube (6.8), and the C-shaped groove (6.1) correspond one-to-one. The two ends of the guide tube (6.8) are connected to their corresponding upper filament inlets and lower filament inlets, respectively. The upper filament inlet, the lower filament inlet, and the guide tube (6.8) are all located directly above the groove space of their corresponding C-shaped groove (6.1).

2. The counter-blown rectifier heating cylinder according to claim 1, characterized in that, The height of the inner cylinder (6.7) is 160-180mm, the height of the outer cylinder (6.6) is 19-21mm greater than the height of the inner cylinder (6.7), the outer diameter of the inner cylinder (6.7) is 220-230mm, the inner diameter of the outer cylinder (6.6) is 23-27mm greater than the outer diameter of the inner cylinder (6.7), and the wall thickness of the inner cylinder (6.7) is 3-5mm.

3. The counter-blown rectifier heating cylinder according to claim 1, characterized in that, It also includes a hot air duct (6.3), which is located outside the outer cylinder (6.6) and connected to the hot air inlet.

4. The counter-blown rectifier heating cylinder according to claim 1, characterized in that, The number of C-shaped grooves (6.1) is 20-24, and all C-shaped grooves (6.1) are evenly distributed around the vertical central axis of the spherical stabilizing chamber (6.5).

5. A counter-blown rectifier heating cylinder according to claim 4, characterized in that, Each C-shaped groove (6.1) has 8-10 compressed air outlets, arranged vertically with spacing between them. The spacing between two adjacent compressed air outlets is 10-12% of the length of the C-shaped groove (6.1). The length of the C-shaped groove (6.1) is 12-15% of the height of the inner cylinder (6.7). The cross-section of the C-shaped groove (6.1) is an arc with a central angle greater than or equal to 250° and less than or equal to 270°. The distance between the top of the C-shaped groove (6.1) and the inner cylinder (6.7) is 38-40% of the height of the inner cylinder (6.7). The distance between the C-shaped groove (6.1) and the cylinder wall of the inner cylinder (6.7) is 15-18% of the inner diameter of the inner cylinder (6.7).

6. A thermal stretching device, characterized in that, It consists of a counter-blown rectifier heating cylinder as described in any one of claims 1-5 and a stretching roller, wherein the stretching roller is located in front of the counter-blown rectifier heating cylinder along the filament running direction.

7. A method for preparing polyester FDY yarn, comprising a hot stretching step, characterized in that, The hot stretching is performed using a hot stretching device as described in claim 6.

8. The method for preparing polyester FDY yarn according to claim 7, characterized in that, The process flow is as follows: metering pump metering → component distribution extrusion → cooling → oiling → guide hook → diamond guide → pre-network → first comb guide → hot stretching → second comb guide → main networker → winding and forming. The spinning process parameters include: spinning temperature 294-296℃, cooling air pressure 18-21Pa, oil rack height 600-750mm, and oil content 1.03-1.25%; The winding process parameters include: hot stretching speed 3680-4350m / min, hot stretching temperature 110-120℃, winding speed 3600-4200m / min, pre-network pressure 0.07-0.09bar, and main network pressure 0.35-0.45bar. The specifications of polyester FDY yarn are 33-111 dtex / 72-288f, and the cross-sectional shape of the monofilament is circular, straight, cross-shaped or I-shaped; the tensile strength of polyester FDY yarn is 3.55-4.32 cN / dtex, the tensile strength uniformity CV value is 2.07-3.12%, the tensile elongation at break is 22.1-40.6%, the tensile elongation uniformity CV value is 3.3-5.6%, and the yarn evenness CV value is 0.72-1.4%.

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