PTT / PA6 Composite Filament and Its Preparation Method

Abstract

The present application discloses a PTT / PA6 composite filament and a preparation method thereof. The preparation method comprises the following steps: S10: drying the PTT raw material chips and the PA6 raw material chips respectively; S20: the PTT dry chips and the PA6 dry chips respectively enter a screw extruder, and after being conveyed, extruded, melted and filtered, a PTT melt and a PA6 melt are obtained; S30: the PTT melt and the PA6 melt respectively enter a composite spinning box to obtain a PTT / PA6 composite melt stream; S40: the PTT / PA6 composite melt stream is cooled and solidified by side blowing to obtain a nascent fiber; S50: the nascent fiber passes through an oil nozzle, a godet hook, a pre-network, a first godet wheel and a second godet wheel and then is wound and formed to obtain a PTT / PA6 pre-oriented filament. The PTT / PA6 composite filament has good elasticity and can meet the differentiated needs of the market.

Description

Technical Field

[0001] The present invention generally relates to the field of spinning, specifically to the field of melt spinning technology, and particularly to a PTT / PA6 composite filament and a preparation method thereof. Background Art

[0002] PTT is polytrimethylene terephthalate, and its fibers have excellent softness and elastic recovery, and also have excellent wrinkle resistance and dimensional stability. At present, PA6 fiber fabrics are very popular and have a good hand feeling, but the dimensional stability of the fabrics is poor. Therefore, these two fibers have good complementarity.

[0003] Patent CN200810107245.9 discloses a preparation method of PTT polyester chips and antistatic PTT polyester fibers. By adding an antistatic agent in the polymerization stage, PTT fibers with good antistatic effect and excellent wearing performance are obtained.

[0004] Patent CN111676528A discloses a preparation method of melt direct spinning polyester-polyamide composite superfine fibers. By improving the matching of the polyester melt direct spinning process and the polyamide melt process, the production energy consumption is reduced, the production efficiency is improved, and the stability of the product quality is improved.

[0005] However, there are few reports on the preparation method of PTT / PA6 composite filaments at present. Summary of the Invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a PTT / PA6 composite filament with good elasticity and dimensional stability and a preparation method thereof.

[0007] In a first aspect, a preparation method of a PTT / PA6 composite filament according to the present invention includes the following steps:

[0008] S10: Drying the PTT raw material chips and the PA6 raw material chips respectively to obtain PTT dry chips and PA6 dry chips;

[0009] S20: The PTT dry chips and the PA6 dry chips enter a screw extruder respectively, and after being conveyed, extruded, melted, and filtered, PTT melt and PA6 melt are obtained. Among them,

[0010] The temperatures of each zone of the screw where the PTT dry chips are located increase sequentially from low to high, the temperature is 245-260°C, and the screw pressure is 10-12 MPa.

[0011] The temperatures of each zone of the screw where the PA6 dry chips are located increase sequentially from low to high, the temperature is 250-265°C, and the screw pressure is 12-14 MPa;

[0012] S30: The PTT melt and the PA6 melt respectively enter the composite spinning box to obtain a PTT / PA6 composite melt stream. Among them, the mass ratio of the PTT melt to the PA6 melt is (75 - 85):(15 - 25);

[0013] S40: The PTT / PA6 composite melt stream is cooled and solidified by side blowing to obtain a nascent fiber;

[0014] S50: The nascent fiber passes through an oil nozzle, a godet hook, a pre-network, a first godet wheel, and a second godet wheel and then is wound and formed to obtain a PTT / PA6 pre-oriented yarn.

[0015] In a second aspect, the PTT / PA6 composite filament of the present invention is prepared by the preparation method of the above-mentioned PTT / PA6 composite filament.

[0016] According to the technical solution provided by the embodiments of the present application, the raw materials are sequentially subjected to slice drying, screw melting, melt compounding, side blowing cooling, and winding and forming to obtain a PTT / PA6 pre-oriented yarn. The PTT / PA6 composite filament can utilize the advantage of good dimensional stability of PTT fibers to make up for the disadvantage of poor dimensional stability of PA6 fibers, forming an advantage to make up for the disadvantage. Moreover, the PTT / PA6 composite filament has good elasticity and can meet the differentiated needs of the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present application will become more apparent:

[0018] Figure 1 It is a process flow schematic diagram of the preparation method of the PTT / PA6 composite filament according to the embodiment of the present invention;

[0019] Figure 2 It is a structural schematic diagram of the PTT slice drying system of the preparation method of the PTT / PA6 composite filament according to the embodiment of the present invention;

[0020] Figure 3 It is a structural schematic diagram of the PA6 slice drying system of the preparation method of the PTT / PA6 composite filament according to the embodiment of the present invention;

[0021] Figure 4 It is a structural schematic diagram of the screw extruder where PTT is located in the preparation method of the PTT / PA6 composite filament according to the embodiment of the present invention;

[0022] Figure 5 It is a structural schematic diagram of the screw extruder where PA6 is located in the preparation method of the PTT / PA6 composite filament according to the embodiment of the present invention;

[0023] Figure 6Schematic structural diagram of the composite spinning box for the preparation method of PTT / PA6 composite filaments according to an embodiment of the present invention;

[0024] Figure 7 Schematic cross-sectional view of the PTT / PA6 composite filaments according to an embodiment of the present invention. Detailed implementation manners

[0025] The following further elaborates the present application in conjunction with the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. Additionally, it should be noted that for ease of description, only parts related to the invention are shown in the drawings.

[0026] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will elaborate on the present application in detail with reference to the drawings and embodiments.

[0027] Please refer to Figures 1 to 6 , the preparation method of the PTT / PA6 composite filaments of the present invention includes the following steps:

[0028] S10: Dry the PTT raw material chips and PA6 raw material chips respectively to obtain PTT dry chips and PA6 dry chips. Drying the PTT raw material chips and PA6 raw material chips can remove the moisture therein, reduce the molecular weight, and reduce the possibility of hydrolysis of the chips. It can also improve the crystallinity and softening point of the PTT chips and PA6 chips, making the PTT dry chips and PA6 dry chips not easily break and generate powder during transportation, and at the same time avoiding the "knotting" phenomenon caused by premature softening and bonding of the PTT dry chips and PA6 dry chips in the screw extruder.

[0029] S20: The PTT dry chips and PA6 dry chips respectively enter the screw extruder, and after being transported, extruded, melted, and filtered, PTT melt and PA6 melt are obtained. Among them, the temperatures of each zone of the screw where the PTT dry chips are located increase sequentially from low to high, the temperature is 245 - 260 °C, and the screw pressure is 10 - 12 MPa. The temperatures of each zone of the screw where the PA6 dry chips are located increase sequentially from low to high, the temperature is 250 - 265 °C, and the screw pressure is 12 - 14 MPa. Feed the PTT dry chips and PA6 dry chips into the screw extruder, send them to the heating zone by the rotating screw, and then send them forward to the metering pump after extrusion and melting. The metering pump controls and ensures the stable inflow of the PTT melt and PA6 melt into the subsequent composite spinning box, which can ensure the preparation efficiency. To reduce the residence time of the PTT melt and PA6 melt in the screw extruder, a filter straight pipe can be added for filtration.

[0030] S30: The PTT melt and the PA6 melt enter the composite spinning box respectively to obtain a PTT / PA6 composite melt stream. Among them, the mass ratio of the PTT melt to the PA6 melt is (75 - 85):(15 - 25). The PTT melt and the PA6 melt can be fed into the composite spinning box through metering pumps to ensure the stable flow rates of the PTT melt and the PA6 melt. The PTT melt and the PA6 melt are spun through the composite spinning box.

[0031] S40: The PTT / PA6 composite melt stream is cooled and solidified by side blowing to obtain a nascent fiber. The side blowing can be generated by a side blowing device, and the side blowing cools and solidifies the PTT / PA6 composite melt stream to obtain a nascent fiber.

[0032] S50: The nascent fiber is wound and formed after passing through an oil nozzle, a godet hook, a pre-network, a first godet wheel, and a second godet wheel to obtain a PTT / PA6 pre-oriented yarn.

[0033] Furthermore, in step S10, the moisture content of the PTT dry chips ≤ 30 ppm, and the moisture content of the PA6 dry chips ≤ 60 ppm.

[0034] Furthermore, in step S10, the viscosity of the PTT raw material chips is 0.9 - 1.0 dL / g, the melting point is 220 - 225 °C, the drying temperature is 128 - 140 °C, the drying time is 6 - 8 h, the dew point of the dry air for drying ≤ -70 °C, and the intake air volume of the dry air is 200 - 250 m 3 / h; the viscosity of the PA6 raw material chips is 2.6 - 2.8 dL / g, the melting point is 223 - 230 °C, the drying temperature is 80 - 100 °C, the drying time is 20 - 22 h, the dew point of the dry air for drying ≤ -70 °C, and the intake air volume of the dry air is 200 - 250 m 3 / h.

[0035] Furthermore, step S30 includes: S31: The PTT melt enters the main body of the composite spinning box, and the PA6 melt enters the auxiliary body of the composite spinning box; S32: After being metered by their respective metering pumps, the PTT melt and the PA6 melt are fed into the composite component in the main body, where the composite component is provided with independent PTT melt channels and PA6 melt channels; S33: After passing through a filter layer, a distribution plate, and a spinneret plate respectively, the PTT melt and the PA6 melt converge at the outlet of the spinneret holes to form a PTT / PA6 composite melt stream.

[0036] Furthermore, in step S32, the heat medium temperature of the main body is 260 °C, and the heat medium temperature of the auxiliary body is 265 °C.

[0037] Further, in step S32, the composite component is provided with a concentric circular sand cavity and an annular sand cavity. The annular sand cavity surrounds the circular sand cavity. The PTT melt flows in the annular sand cavity, and the pressure in the annular sand cavity is 12 - 14 MPa. The PA6 melt flows in the circular sand cavity, and the pressure in the circular sand cavity is 8 - 10 MPa. The PTT melt and the PA6 melt flow out of the composite component simultaneously. The cross-section of the PTT / PA6 composite filament is orange-petal-shaped.

[0038] Further, in step S40, the temperature of the side blowing is 20 - 22 °C, the relative humidity is 80 - 85%, and the wind speed is 0.4 - 0.52 m / s. This ensures the cooling and solidification effect of the side blowing on the PTT / PA6 composite melt stream.

[0039] Further, in step S50, after the as-spun fiber is oiled on the oil nozzle, the oil content is 0.4 - 0.6%, and the pre-network pressure is 0.1 MPa.

[0040] Further, in step S50, the speed of the first godet is 3000 r / min, the speed of the second godet is 3020 r / min, and the winding speed of the as-spun fiber is 3000 r / min.

[0041] To further understand the present application, the PTT / PA6 composite filament and its preparation method provided by the present application will be specifically described below in conjunction with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given. It is only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0042] For those not specified in the embodiments in terms of specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0043] Example 1

[0044] The present invention provides a method for preparing a PTT / PA6 composite filament, comprising the following steps:

[0045] S10. Chip Drying: The PTT raw material chips are first fed into the high-level silo through a negative pressure suction feeding system, then sent to the drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 30 ppm. Finally, the dry chips enter the screw extruder. The PA6 raw material chips are fed into the high-level silo through a negative pressure suction feeding system, then sent to the drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 60 ppm. Finally, the dry chips enter the screw extruder. The viscosity of the PTT raw material chips is 0.92 dL / g, and the melting point is 223 °C; the drying temperature is 130 °C, and the drying time is 6 h. The viscosity of the PA6 raw material chips is 2.62 dL / g, and the melting point is 225 °C; the drying temperature is 80 °C, and the drying time is 20 h; the dew point of the dry air for drying ≤ -70 °C, and the intake volume of the dry air is 200 m 3 / h.

[0046] S20. Screw Melting: The PTT dry chips and PA6 dry chips respectively enter the screw extruder, and after being transported, extruded, melted, and filtered, they are spun. To reduce the residence time of the melt, a filter straight pipe is added if necessary. The temperatures of each zone of the PTT screw increase gradually from low to high, which are 245 / 248 / 252 / 254 / 256 / 258 °C in sequence, and the screw pressure is controlled at 10 - 12 MPa; the temperatures of each zone of the PA6 screw increase gradually from low to high, which are 250 / 254 / 258 / 260 / 262 / 264 °C in sequence, and the screw pressure is controlled at 12 - 14 MPa.

[0047] S30. Composite Box and Components: The PTT melt and PA6 melt respectively enter the main box and the sub-box of the composite spinning box, and then are sent to the composite components in the main box after being metered by their respective metering pumps. The composite components are provided with independent channels respectively. The PTT melt and PA6 melt converge at the outlet of the spinneret holes after passing through the filter layer, distribution plate, and spinneret plate, forming a composite melt stream. The main and sub-chambers have their own independent heat medium circulation heating systems, and there is a heat preservation board separating the main and sub-boxes. The heat medium temperature of the main box is controlled at 260 °C, and the heat medium temperature of the sub-box is controlled at 265 °C. The composite components adopt a concentric circle double sand cavity. The outer circle has a large capacity for the PTT to flow through, and the inner circle has a small capacity for the PA6 to flow through, while ensuring that both flow out of the sand cavity at the same time. The pressure of the PTT component is 12 - 14 MPa, and the pressure of the PA6 component is 8 - 10 MPa.

[0048] S40. Side Blowing Cooling: The composite melt stream is cooled and solidified by side blowing to form nascent fibers. A large amount of monomers will precipitate from both the PTT and PA6 melts. To ensure uniform cross-section and good filament formation, a monomer suction system is added. The side blowing temperature is 21 °C, the relative humidity is 80%, and the wind speed is 0.5 m / s.

[0049] S50. Winding and forming: The nascent fiber is wound and formed after passing through an oil nozzle, a wire guide hook, a pre-network, a first godet wheel, and a second godet wheel to obtain PTT / PA6 pre-oriented yarn. The oil content is 0.45%, the pre-network pressure is 0.1 MPa, the speed of the first godet wheel is 3000 r / min, the speed of the second godet wheel is 3020 r / min, and the winding speed is 3000 r / min.

[0050] In this embodiment, the mass ratio of PTT to PA6 is 80:20, and the specification of the PTT / PA6 composite filament is 150 d / 72 f. Refer to Figure 7 , the cross-section of the PTT / PA6 composite filament is in the shape of orange segments, where the black part is PTT and the white part is PA6.

[0051] Example 2

[0052] The present invention provides a method for preparing a PTT / PA6 composite filament, comprising the following steps:

[0053] S10. Chip drying: The PTT raw material chips are first fed into a high-level silo through a negative pressure feeding system, then sent to a drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 30 ppm. Finally, the dry chips enter a screw extruder. The PA6 raw material chips are fed into a high-level silo through a negative pressure feeding system, then sent to a drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 60 ppm. Finally, the dry chips enter a screw extruder. The viscosity of the PTT raw material chips is 0.93 dL / g, and the melting point is 224 °C; the drying temperature is 130 °C, and the drying time is 6 h. The viscosity of the PA6 raw material chips is 2.64 dL / g, and the melting point is 226 °C; the drying temperature is 90 °C, and the drying time is 20 h; the dew point of the dried dry air ≤ -70 °C, and the intake air volume of the dry air is 200 m 3 / h.

[0054] S20. Screw melting: The PTT dry chips and the PA6 dry chips enter the screw extruder respectively, and are spun after being transported, extruded, melted, and filtered. To reduce the residence time of the melt, a filter straight pipe is added if necessary. The temperatures of each zone of the PTT screw increase from low to high in sequence, which are 246 / 249 / 253 / 255 / 257 / 259 °C, and the screw pressure is controlled at 10 - 12 MPa; the temperatures of each zone of the PA6 screw increase from low to high in sequence, which are 252 / 255 / 258 / 261 / 263 / 265 °C, and the screw pressure is controlled at 12 - 14 MPa.

[0055] S30, Composite Box and Components: The PTT melt and the PA6 melt enter the main box and the auxiliary box of the composite spinning box respectively, and then are sent into the composite component in the main box after being metered by their respective metering pumps. The composite component is provided with independent channels. The PTT melt and the PA6 melt converge at the outlet of the spinneret holes after passing through the filter layer, the distribution plate and the spinneret plate, forming a composite melt stream. The main and auxiliary cavities have their own independent heat medium circulation heating systems, and there is a heat preservation plate separating the main and auxiliary boxes. The heat medium temperature of the main box is controlled at 260 °C, and the heat medium temperature of the auxiliary box is controlled at 265 °C. The composite component adopts a concentric circle double sand cavity. The outer circle has a large capacity for PTT to flow through, and the inner circle has a small capacity for PA6 to flow through, while ensuring that both flow out of the sand cavity at the same time. The pressure of the PTT component is 12 - 14 MPa, and the pressure of the PA6 component is 8 - 10 MPa.

[0056] S40, Side Blowing Cooling: The composite melt stream is cooled and solidified by side blowing to form a nascent fiber. A large amount of monomers will precipitate from both the PTT and PA6 melts. To ensure a uniform cross-section and good filament formation, a monomer suction system is added. The side blowing temperature is 21 °C, the relative humidity is 80%, and the wind speed is 0.52 m / s.

[0057] S50, Winding and Shaping: The nascent fiber is wound and shaped after passing through the oil nozzle, the wire guide hook, the pre-network, the first godet wheel and the second godet wheel, obtaining PTT / PA6 pre-oriented yarn. The oil content is 0.48%, the pre-network pressure is 0.1 MPa, the speed of the first godet wheel is 3000 r / min, the speed of the second godet wheel is 3020 r / min, and the winding speed is 3000 r / min.

[0058] In this embodiment, the mass ratio of PTT to PA6 is 75:25, and the specification of the PTT / PA6 composite filament is 250 d / 144 f.

[0059] Example 3

[0060] The present invention provides a method for preparing PTT / PA6 composite filament, comprising the following steps:

[0061] S10, Chip Drying: The PTT raw material chips are first fed into the high-level silo through a negative pressure feeding system, then sent to the drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 30 ppm. Finally, the dry chips enter the screw extruder. The PA6 raw material chips are fed into the high-level silo through a negative pressure feeding system, then sent to the drying tower through a rotary valve, and then dried with hot dry air to obtain dry chips with a moisture content ≤ 60 ppm. Finally, the dry chips enter the screw extruder. The viscosity of the PTT raw material chips is 0.91 dL / g, and the melting point is 222 °C; the drying temperature is 128 °C, and the drying time is 6 h. The viscosity of the PA6 raw material chips is 2.61 dL / g, and the melting point is 223 °C; the drying temperature is 80 °C, and the drying time is 20 h; the dew point of the dry air for drying ≤ -70 °C, and the intake volume of the dry air is 200 m 3 / h.

[0062] S20, Screw Melting: The PTT dry chips and PA6 dry chips enter the screw extruder respectively, and after conveying, extrusion, melting, and filtration, they are spun. To reduce the residence time of the melt, a filter straight-through pipe is added if necessary. The temperatures of each zone of the PTT screw increase from low to high in sequence, which are 245 / 248 / 252 / 254 / 256 / 258 °C, and the screw pressure is controlled at 10 - 12 MPa; the temperatures of each zone of the PA6 screw increase from low to high in sequence, which are 250 / 253 / 255 / 260 / 262 / 263 °C, and the screw pressure is controlled at 12 - 14 MPa.

[0063] S30, Composite Box and Components: The PTT melt and PA6 melt enter the main box and the sub-box of the composite spinning box respectively, and then are sent to the composite components in the main box after being metered by their respective metering pumps. The composite components are provided with independent channels. The PTT melt and PA6 melt converge at the outlet of the spinneret holes after passing through the filter layer, distribution plate, and spinneret plate to form a composite melt stream. The main and sub-cavities have their own independent heat medium circulation heating systems, and there is a heat preservation board separating the main and sub-boxes. The heat medium temperature of the main box is controlled at 260 °C, and the heat medium temperature of the sub-box is controlled at 265 °C. The composite components adopt a concentric circle double sand cavity. The outer circle has a large capacity for PTT to flow through, and the inner circle has a small capacity for PA6 to flow through, while ensuring that both flow out of the sand cavity at the same time. The pressure of the PTT component is 12 - 14 MPa, and the pressure of the PA6 component is 8 - 10 MPa.

[0064] S40, Side Blowing Cooling: The composite melt stream is cooled and solidified by side blowing to form nascent fibers. A large amount of monomers will precipitate from both the PTT and PA6 melts. To ensure uniform cross-section and good filament winding, a monomer suction system is added. The side blowing temperature is 20 °C, the relative humidity is 80%, and the wind speed is 0.48 m / s.

[0065] S50. Winding and forming: The nascent fiber is wound and formed after passing through an oil nozzle, a godet, a pre-network, a first godet, and a second godet to obtain PTT / PA6 pre-oriented yarn. The oil content is 0.42%, the pre-network pressure is 0.1 MPa, the speed of the first godet is 3000 r / min, the speed of the second godet is 3020 r / min, and the winding speed is 3000 r / min.

[0066] In this embodiment, the mass ratio of PTT to PA6 is 85:15, and the specification of the PTT / PA6 composite filament is 75d / 36f.

[0067] Table 1 shows the performance indexes of the PTT / PA6 composite filament obtained in the embodiment of the present invention.

[0068]

[0069] The breaking elongation and breaking strength are tested by using the test method for tensile properties of chemical fiber filaments GB / T 14344-2022.

[0070] The crimp shrinkage rate, crimp modulus, and crimp stability are tested by using the test method for crimp properties of synthetic fiber textured yarns GB / T 6506-2017.

[0071] The process parameters for making the PTT / PA6 composite filament into DTY are as follows: the machine speed is 700 m / min, the first hot box is 178°C ± 1, the second hot box is 160°C ± 1, the D / Y ratio is 1.5 times, and the draw ratio is 1.6 times.

[0072] As can be seen from Table 1, the PTT / PA6 composite filament prepared by the preparation method of the present invention has good elasticity. PTT belongs to the polyester category, has regular structure, and relatively good dimensional stability.

[0073] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A method for preparing PTT / PA6 composite filaments, characterized in that, it comprises the following steps: S10: Dry the PTT raw material chips and PA6 raw material chips respectively to obtain PTT dry chips and PA6 dry chips, wherein the moisture content of the PTT dry chips ≤ 30 ppm, and the moisture content of the PA6 dry chips ≤ 60 ppm; S20: The PTT dry chips and PA6 dry chips respectively enter the screw extruder, and after being transported, extruded, melted, and filtered, PTT melt and PA6 melt are obtained, wherein, the temperatures of each zone of the screw where the PTT dry chips are located increase sequentially from low to high, the temperature is 245 - 260 °C, and the screw pressure is 10 - 12 MPa, the temperatures of each zone of the screw where the PA6 dry chips are located increase sequentially from low to high, the temperature is 250 - 265 °C, and the screw pressure is 12 - 14 MPa; S30: The PTT melt and PA6 melt respectively enter the composite spinning box to obtain PTT / PA6 composite melt filaments, wherein the mass ratio of the PTT melt to the PA6 melt is (75 - 85):(15 - 25); S40: The PTT / PA6 composite melt filaments are cooled and solidified by side blowing to obtain nascent fibers; S50: The nascent fibers pass through an oil nozzle, a godet hook, a pre-network, a first godet wheel and a second godet wheel and then are wound and formed to obtain PTT / PA6 pre-oriented filaments. The cross-section of the PTT / PA6 composite filaments is orange petal-shaped, Step S30 includes: S31: The PTT melt enters the main box of the composite spinning box, and the PA6 melt enters the sub-box of the composite spinning box; S32: After being metered by their respective metering pumps, the PTT melt and PA6 melt are sent into the composite component in the main box. The composite component is provided with independent PTT melt channels and PA6 melt channels. The composite component is provided with concentric circular sand cavities and annular sand cavities. The annular sand cavity surrounds the circular sand cavity. The PTT melt flows in the annular sand cavity, and the pressure in the annular sand cavity is 12 - 14 MPa. The PA6 melt flows in the circular sand cavity, and the pressure in the circular sand cavity is 8 - 10 Mpa. The PTT melt and PA6 melt flow out of the composite component simultaneously; S33: The PTT melt and PA6 melt respectively pass through a filter layer, a distribution plate, and a spinneret plate, and then converge at the outlet of the spinneret holes to form PTT / PA6 composite melt filaments.

2. The method for preparing PTT / PA6 composite filaments according to claim 1, characterized in that, in step S10, The viscosity of the PTT raw material chips is 0.9 - 1.0 dL / g, the melting point is 220 - 225 °C, the drying temperature is 128 - 140 °C, the drying time is 6 - 8 h, the dew point of the dry air for drying is ≤ -70 °C, and the intake air volume of the dry air is 200 - 250 m 3 / h; The viscosity of the PA6 raw material chips is 2.6 - 2.8 dL / g, the melting point is 223 - 230 °C, the drying temperature is 80 - 100 °C, the drying time is 20 - 22 h, the dry air dew point for drying is ≤ -70 °C, and the dry air intake is 200 - 250 m 3 / h.

3. The method for preparing PTT / PA6 composite filaments according to claim 1, characterized in that, in step S32, the heat medium temperature of the main box is 260 °C, and the heat medium temperature of the sub-box is 265 °C.

4. The method for preparing PTT / PA6 composite filaments according to claim 1, characterized in that, in step S40, the temperature of the side blowing is 20 - 22 °C, the relative humidity is 80 - 85%, and the wind speed is 0.4 - 0.52 m / s.

5. The method for preparing PTT / PA6 composite filaments according to claim 1, characterized in that, in step S50, after the nascent fibers are oiled by the oil nozzle, the oil content is 0.4 - 0.6%, and the pre-network pressure is 0.1 MPa.

6. The preparation method of the PTT / PA6 composite filament according to claim 1, characterized in that, in step S50, the speed of the first godet is 3000 r / min, the speed of the second godet is 3020 r / min, and the winding speed of the nascent fiber is 3000 r / min.

7. A PTT / PA6 composite filament prepared by the preparation method according to any one of claims 1 to 6.

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