Long-acting flame-retardant polyester monofilament and preparation method thereof

Abstract

The invention discloses a long-acting flame-retardant polyester monofilament and a preparation method thereof, particularly relates to the technical field of fiber manufacturing, and relates to a long-acting flame-retardant polyester monofilament and a preparation method thereof. The long-acting flame-retardant polyester monofilament is prepared from 100 parts of polyester chips, 15-25 parts of precursor powder, 8-12 parts of zirconium phosphate powder, 0.6-1.2 parts of a composite antioxidant and 0.5-1.0 part of a composite lubricant. Flame-retardant elements are bonded to a main chain of a polyester molecule in a chemical copolymerization manner and cooperate with a catalyst in a skin layer, so that an intrinsic flame-retardant stable system is constructed, and the problem of poor flame-retardant durability caused by easy loss of a traditional flame retardant is solved.

Description

Technical Field

[0001] This invention relates to the field of fiber manufacturing technology, and more specifically, to a long-lasting flame-retardant polyester monofilament and its preparation method. Background Technology

[0002] Polyester fiber is widely used in clothing, home textiles, and industrial fabrics due to its high strength, good elasticity, and resistance to chemical corrosion. However, polyester materials themselves have a low limiting oxygen index and are flammable. Therefore, flame-retardant modification of polyester fibers is of great significance to meet the requirements of long-term safety in harsh operating environments.

[0003] The polyester monofilaments in related technologies include polyester chips, flame retardants, synergists, and processing aids. Polyester chips are typically polyethylene terephthalate (PET), serving as the fiber skeleton and providing the main mechanical strength and basic physicochemical properties. Flame retardants are often halogenated or small-molecule phosphorus-based flame retardants, which improve the limiting oxygen index of the material by interfering with the chemical reaction of combustion in the gas or condensed phase, thus imparting flame retardant properties. Synergists, generally antimony trioxide, are used in conjunction with halogenated flame retardants to significantly improve flame retardant efficiency through a synergistic effect. Processing aids generally include lubricants and stabilizers, used to improve melt flowability and processing stability, ensuring smooth spinning.

[0004] However, it still has some drawbacks in practical use, such as poor flame retardancy. The small molecule flame retardants added by traditional methods have limited compatibility with the polyester matrix and are prone to migration and precipitation in later use, repeated washing, or high temperature environments, resulting in rapid decay of flame retardant performance; poor mechanical properties. The large amount of small molecule flame retardants added by traditional methods will destroy the regularity of the polyester macromolecular structure, often leading to a decrease in the strength and toughness of the monofilament; and poor durability. The ester bond structure of traditional polyester substrate is easily affected by environmental factors such as high temperature, humidity, and ultraviolet light, resulting in hydrolysis, thermo-oxidative aging, and photodegradation reactions, leading to molecular chain breakage, fiber strength decay, and yellowing and embrittlement of the surface. Summary of the Invention

[0005] To improve the above-mentioned problems and reduce the issues of poor flame retardancy, poor mechanical properties, and poor durability of polyester monofilaments in related technologies, this invention provides a long-lasting flame-retardant polyester monofilament and its preparation method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing long-lasting flame-retardant polyester monofilament includes the following steps: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 265-275℃, the core screw heating zone is heated to 260-270℃, and the output mass ratio is 35-45:55-65. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular air blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0007] Preferably, the raw materials for preparing the long-lasting flame-retardant polyester monofilament are as follows: 100 parts polyester chips, 15-25 parts precursor powder, 8-12 parts zirconium phosphate powder, 0.6-1.2 parts composite antioxidant, and 0.5-1.0 parts composite lubricant.

[0008] Preferably, the method for preparing the polyester chips includes the following steps: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at a temperature of 240-255℃ and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 265-280℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0009] Preferably, the raw materials for preparing the polyester chips are as follows: 100 parts purified terephthalic acid, 45-53 parts ethylene glycol, 2.6-4.5 parts 2-carboxyethylphenylphosphonic acid, 0.008-0.035 parts antimony trioxide, and 0.012-0.025 parts triphenyl phosphate.

[0010] Preferably, the method for preparing the precursor powder includes the following steps: A1. Terephthalic acid, adipic acid, and ethylene glycol were added to a polymerization reactor. Under a nitrogen atmosphere, tetrabutyl titanate (an esterification catalyst) and dibutyltin dilaurate (a polycondensation catalyst) were added. A pre-polycondensation reaction was initiated at 210-225°C and continued for 60 min. Subsequently, the system temperature was lowered to 190-200°C, and then dihydrazide chain extender was added and stirred at 100 r / min for 30 min. Next, a polycondensation reaction was carried out at 230-250°C, a pressure below 200 MPa, and a stirring speed of 30 r / min for 2 h to obtain the copolymer. A2. The copolymer obtained in A1 is cooled, granulated, pulverized using a mechanical pulverizer, and passed through a 100-mesh sieve to obtain precursor powder.

[0011] Preferably, the raw materials for preparing the precursor powder and their weight parts are as follows: 100 parts terephthalic acid, 28-60 parts adipic acid, 65-82 parts ethylene glycol, 8-18 parts dihydrazide chain extender, 0.24-0.31 parts tetrabutyl titanate, and 0.38-0.48 parts dibutyltin dilaurate.

[0012] Preferably, the dihydrazide chain extender is a dihydrazide chain extender containing a dynamic covalent bond of acylhydrazone.

[0013] Preferably, the zirconium phosphate powder is a porous nano-zirconium phosphate powder that has been surface-treated with aminopropyltriethoxysilane.

[0014] Preferably, the composite antioxidant is formed by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; The compound antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a mass ratio of 1:1.

[0015] Preferably, the surface treatment liquid is composed of aminopropyltriethoxysilane, aqueous fluorinated polyurethane dispersion, deionized water, and anhydrous ethanol in a mass ratio of 2:10:44:44.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention constructs a stable system with inherent flame retardancy by chemically copolymerizing flame retardant elements into the main chain of polyester molecules and working synergistically with catalysts in the skin layer, thus solving the problem of poor flame retardant durability caused by the easy loss of traditional flame retardants. 2. This invention employs a core-sheath composite spinning and multi-stage hot stretching process to construct a special gradient structure with high-strength polyester chips as the core and a skin containing dynamic network precursor powder and composite materials as the skin. The mechanical properties are improved through the synergistic effect of the toughness of the skin layer and the rigidity of the core layer. 3. This invention constructs a densely coupled protective layer with chemical cross-linking on the surface of a monofilament and combines it with the self-healing potential of the dynamic covalent bond network inside the cortex, forming a dual durability protection mechanism from the outside to the inside. This significantly improves the material's ability to resist environmental erosion and maintain functional integrity over the long term, thereby enhancing its durability. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments of the present invention. Unless otherwise specified below, the raw materials used in the various examples and embodiments of the present invention are all commercially available common materials. Preparation Examples 1-5 A polyester chip, the components and their corresponding proportions of which are shown in the table below, is prepared using the following method: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at 250 °C and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 270℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0018] Table: Components and their mass ratios (g) of the raw materials used in Preparation Examples 1-5 Preparation Example 6 A polyester chip, differing from preparation example 1, is prepared using the following method: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at 240℃ and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 270℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0019] Preparation Example 7 A polyester chip, differing from preparation example 1, is prepared using the following method: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at a temperature of 255℃ and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 270℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0020] Preparation Example 8 A polyester chip, differing from preparation example 1, is prepared using the following method: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at 250 °C and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 265℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0021] Preparation Example 9 A polyester chip, differing from preparation example 1, is prepared using the following method: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at 250 °C and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 280℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

[0022] Preparation Examples 10-14 A precursor powder, the components and their corresponding proportions of which are shown in the table below, is prepared using the following method: A1. Terephthalic acid, adipic acid, and ethylene glycol were added to a polymerization reactor. Under a nitrogen atmosphere, tetrabutyl titanate (an esterification catalyst) and dibutyltin dilaurate (a polycondensation catalyst) were added. A pre-polycondensation reaction was initiated at 220°C and continued for 60 min. Subsequently, the system temperature was lowered to 195°C, and then dihydrazide chain extender was added and stirred at 100 r / min for 30 min. Next, a polycondensation reaction was carried out at 240°C, a pressure below 200 MPa, and a stirring speed of 30 r / min for 2 h to obtain the copolymer. Specifically, the dihydrazide chain extender is a dihydrazide chain extender containing a dynamic covalent bond of acylhydrazone; A2. The copolymer obtained in A1 is cooled, granulated, pulverized using a mechanical pulverizer, and passed through a 100-mesh sieve to obtain precursor powder.

[0023] Table: Components and their mass ratios (g) of the raw materials used in Preparation Examples 10-14 Preparation Example 15 A precursor powder, differing from preparation example 10 in that its preparation method is as follows: A1. Terephthalic acid, adipic acid, and ethylene glycol were added to a polymerization reactor. Under a nitrogen atmosphere, tetrabutyl titanate (an esterification catalyst) and dibutyltin dilaurate (a polycondensation catalyst) were added. A pre-polycondensation reaction was initiated at 210°C and continued for 60 min. Subsequently, the system temperature was lowered to 190°C, and then dihydrazide chain extender was added and stirred at 100 r / min for 30 min. Next, a polycondensation reaction was carried out at 230°C, a pressure below 200 MPa, and a stirring speed of 30 r / min for 2 h to obtain the copolymer. A2. The copolymer obtained in A1 is cooled, granulated, pulverized using a mechanical pulverizer, and passed through a 100-mesh sieve to obtain precursor powder.

[0024] Preparation Example 16 A precursor powder, differing from preparation example 10 in that its preparation method is as follows: A1. Terephthalic acid, adipic acid, and ethylene glycol were added to a polymerization reactor. Under a nitrogen atmosphere, tetrabutyl titanate (an esterification catalyst) and dibutyltin dilaurate (a polycondensation catalyst) were added. A pre-polycondensation reaction was initiated at 225°C and continued for 60 min. Subsequently, the system temperature was lowered to 200°C, and then dihydrazide chain extender was added and stirred at 100 r / min for 30 min. Next, a polycondensation reaction was carried out at 250°C, a pressure below 200 MPa, and a stirring speed of 30 r / min for 2 h to obtain the copolymer. A2. The copolymer obtained in A1 is cooled, granulated, pulverized using a mechanical pulverizer, and passed through a 100-mesh sieve to obtain precursor powder.

[0025] Preparation Examples 17-21 A long-lasting flame-retardant polyester monofilament, the components and their corresponding proportions of which are shown in the table below, is prepared using the following method: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. Specifically, the zirconium phosphate powder is a porous nano-zirconium phosphate powder that has undergone surface treatment with aminopropyltriethoxysilane; The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a mass ratio of 1:1. The lubricant is composed of lubricant EBS and lubricant calcium stearate in a mass ratio of 1:1. The polyester chips were prepared according to Preparation Example 1; The precursor powder was prepared in Preparation Example 10; S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 270℃, the core screw heating zone is heated to 265℃, and the output mass ratio is 45:55. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0026] The surface treatment solution is composed of aminopropyltriethoxysilane, aqueous fluorinated polyurethane dispersion, deionized water, and anhydrous ethanol in a mass ratio of 2:10:44:44. Table: Components and their mass ratios (g) of the raw materials used in Preparation Examples 17-21 Preparation Example 22 A long-lasting flame-retardant polyester monofilament, which differs from preparation example 17 in that its preparation method is as follows: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 265℃, the core screw heating zone is heated to 260℃, and the output mass ratio is 45:55. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0027] Preparation Example 23 A long-lasting flame-retardant polyester monofilament, which differs from preparation example 17 in that its preparation method is as follows: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 275℃, the core screw heating zone is heated to 270℃, and the output mass ratio is 45:55. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular air blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0028] Preparation Example 24 A long-lasting flame-retardant polyester monofilament, which differs from preparation example 17 in that its preparation method is as follows: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 270℃, the core screw heating zone is heated to 265℃, and the output mass ratio is 35:65. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0029] Preparation Example 25 A long-lasting flame-retardant polyester monofilament, which differs from preparation example 17 in that its preparation method is as follows: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 270℃, the core screw heating zone is heated to 265℃, and the output mass ratio is 40:60. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

[0030] Preparation Examples 26-33 A long-lasting flame-retardant polyester monofilament differs from Preparation Example 17 in that the polyester chips used in its components are different, as shown in the table below.

[0031] Table: Comparison of Polyester Chip Usage in Preparation Examples 26-33 Preparation Examples 34-39 A long-lasting flame-retardant polyester monofilament differs from Preparation Example 17 in that the precursor powder used in its components is different, and the specific correspondence is shown in the table below.

[0032] Table: Comparison of precursor powder usage in preparation examples 35-39 Performance testing The long-lasting flame-retardant polyester monofilaments prepared in each embodiment were selected for testing. The test subjects were 230 samples of long-lasting flame-retardant polyester monofilaments, with 10 samples in each group. Their flame retardancy, mechanical properties, and durability were tested. The specific testing steps are as follows: Flame retardancy: First, samples were taken from the long-lasting flame-retardant polyester monofilaments prepared in the examples. The oxygen index method was used to determine the minimum oxygen concentration (LOI) required for the material to maintain continuous combustion in a nitrogen-oxygen mixed gas, thereby characterizing the flame retardancy of the long-lasting flame-retardant polyester monofilaments. The test results and evaluation criteria are as follows: LOI > 28% (considered as having strong flame retardancy); LOI < 28% (considered as weak flame retardancy).

[0033] Mechanical properties: First, samples of the long-lasting flame-retardant polyester monofilaments prepared in the examples were taken. Under standard temperature and humidity conditions, the monofilaments were stretched to breakage at a constant rate of 500 mm / min using a tensile testing machine. The maximum force and elongation at break were recorded, and the breaking strength of the monofilaments was calculated to characterize the mechanical properties of the long-lasting flame-retardant polyester monofilaments. The test results and evaluation criteria are as follows: The breaking strength of a single filament is >4.0 cN / dtex (considered as having strong mechanical properties); The breaking strength of a single filament is <4.0 cN / dtex (considered as having weak mechanical properties).

[0034] Durability: First, samples of the long-lasting flame-retardant polyester monofilaments prepared in the examples were taken and their surface condition was observed after 200 cycles of dry and wet friction. This was used to characterize the durability of the long-lasting flame-retardant polyester monofilaments. The test results and evaluation criteria are as follows: Acceptable: No obvious damage, fuzzing, or coating peeling on the surface (considered as highly durable); Unacceptable: The surface has obvious damage, fuzzing or coating peeling (considered as poor durability).

[0035] It should be specifically noted that the long-lasting flame-retardant polyester monofilaments obtained above are those produced under normal production methods. Any defective long-lasting flame-retardant polyester monofilaments produced should be discarded.

[0036] Examples 1-9 The corresponding relationship of the preparation methods used for a long-lasting flame-retardant polyester monofilament is shown in the table below.

[0037] Table: Comparison of the application of long-lasting flame-retardant polyester monofilaments in Examples 1-9 Long-lasting flame-retardant polyester monofilaments from Examples 1-9 were extracted and their minimum oxygen concentration (LOI), monofilament breaking strength, and surface condition were tested according to the above measurement steps and standards. The average values ​​of the test results were recorded in the table below.

[0038] Table: Performance test results of minimum oxygen concentration (LOI), monofilament breaking strength, and surface condition in Examples 1-9 As can be seen from the table above, the preparation processes of long-lasting flame-retardant polyester monofilaments in Examples 1-9 all effectively improve the production efficiency of long-lasting flame-retardant polyester monofilaments. Purified terephthalic acid and ethylene glycol are used as basic monomers to construct the polyester molecular backbone. By introducing dicarboxyethylphenylphosphine as a reactive flame-retardant monomer to participate in copolymerization, phosphorus is permanently anchored in the molecular chain in the form of covalent bonds, fundamentally endowing the material with inherent and non-migrating flame-retardant properties. Antimony trioxide, as a highly efficient polycondensation catalyst, ensures that the polymer reaches the required molecular weight, and triphenyl phosphate, as a stabilizer, effectively inhibits thermal degradation during high-temperature processing. In the preparation of the dynamic network precursor, terephthalic acid provides rigidity, adipic acid introduces flexible segments, ethylene glycol serves as a connecting unit, and the key dihydrazide chain extender binds to the polymer through the hydrazide groups at both ends of its molecule. Chain reactions introduce dynamic and reversible acylhydrazone chemistry, thereby endowing the material with the ability to form a self-healing network during subsequent heat treatment. Tetrabutyl titanate or dibutyltin dilaurate serves as a catalyst in this step, ensuring synthesis efficiency. In the skin premix, polyester chips serve as a continuous matrix, dynamic network precursor powder serves as a toughening and self-healing functional phase, and surface-treated nano-zirconium phosphate powder serves as a highly efficient char-forming agent and physical reinforcement point. During combustion, it produces a synergistic effect with the intrinsic flame-retardant system, significantly improving flame-retardant efficiency and mechanically enhancing toughness. Composite antioxidants prevent thermo-oxidative aging of the material through a main-auxiliary synergistic mechanism, while composite lubricants improve melt processing fluidity. Together, they ensure the stability of the spinning process and the long-term durability of the final product, thus achieving the goal of improving the production effect of long-lasting flame-retardant polyester monofilament. Its minimum oxygen concentration (LOI) is 31.4-33.5%, which is considered to be strong flame retardancy; its single filament breaking strength is 4.2-5.0 cN / dtex, which is considered to be strong mechanical properties; its surface condition is qualified, with no obvious damage, fuzzing, or coating peeling, which is considered to be strong durability. It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilament can be increased by adjusting the proportions of the raw materials. Based on the data in the table above, it is clear that the long-lasting flame-retardant polyester monofilament prepared using 100 parts polyester chips, 15 parts precursor powder, 12 parts zirconium phosphate powder, 0.6 parts composite antioxidant, and 1.0 part composite lubricant exhibits the strongest flame retardancy. This is because the highest content of nano-zirconium phosphate is used as a highly efficient char-forming catalyst, which produces a strong synergistic effect with the intrinsically flame-retardant matrix during combustion, catalyzing the formation of extremely potent char-forming materials. A dense and robust expanded char layer provides an excellent thermal and oxygen barrier; the proportion of dynamic network precursors ensures the necessary toughness of the material while avoiding excessive decomposition of flexible segments that could interfere with the combustion process, allowing heat and reaction to focus more on the efficient char formation pathway; in addition, a high content of composite lubricant ensures the uniform dispersion of highly filled nanoparticles during processing, constructing a homogeneous and complete flame-retardant network; and the necessary composite antioxidants effectively maintain the stability of the matrix and all functional components during the processing thermal process, ensuring that the designed flame-retardant structure is well preserved and ultimately functions, as obtained from Examples 1-5.

[0039] It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilaments can be enhanced by adjusting the proportions of these materials. Based on the data in the table above, it is clear that the following formulations yield the longest-lasting flame-retardant polyester monofilaments with the strongest mechanical properties: 100 parts polyester chips, 20 parts precursor powder, 10 parts zirconium phosphate powder, 0.8 parts composite antioxidant, and 0.7 parts composite lubricant; and 100 parts polyester chips, 18 parts precursor powder, 9 parts zirconium phosphate powder, 1.2 parts composite antioxidant, and 0.8 parts composite lubricant. This is because the ratios of the dynamic network precursor and nano-zirconium phosphate are maintained in a highly coordinated manner in both formulations. Within the range, the flexible dynamic network contributed by the former and the rigid nano-reinforcing points provided by the latter form an ideal interpenetration and synergy; in the stretching process, the nanoparticles can effectively transfer and disperse stress to prevent crack propagation, while the moderate dynamic network dissipates energy and prevents brittle fracture through the exchange of reversible bonds. The two work together to endow the material with extremely high strength and toughness; at the same time, the amount of composite antioxidant and composite lubricant in the formulation is precisely calibrated, which can not only fully protect the polymer matrix from degradation during high-temperature spinning to maintain its intrinsic strength, but also ensure that all functional components are uniformly dispersed in the melt to avoid the generation of defect stress concentration points, as obtained from Examples 1-5.

[0040] It is evident that, given a fixed amount of raw materials, the production efficiency of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the preparation conditions. Based on the data in the table above, it is clear that when preparing long-lasting flame-retardant polyester monofilaments, increasing the sheath and core temperatures during melt spinning initially strengthens and then weakens the flame retardancy and mechanical properties of the resulting monofilaments. The maximum flame retardancy and strongest mechanical properties are achieved when the temperature in each heating zone of the sheath screw is 270℃ and the temperature in each heating zone of the core screw is 265℃. The reason for this is that this temperature combination first ensures that all functional components in the sheath, including dynamic components, are fully utilized. The network precursor and nano-zirconium phosphate achieve full melting and ideal fluidity, thus realizing uniform dispersion at the nanoscale and perfect construction of the functional network. At the same time, this temperature also allows the intrinsic flame-retardant polyester molecular chains of the core layer to fully extend, providing a high-strength skeleton for the monofilament. The 5°C temperature difference creates the best viscosity matching and thermodynamic compatibility between the two melts, enabling the formation of strong and defect-free molecular entanglements and bonds at the core-sheath interface, thereby efficiently coupling the functionality of the sheath layer and the support of the core layer into a whole. However, if the temperature is too high, it will cause thermal oxidative degradation of the polymer molecular chains, weakening the matrix strength, as shown in Examples 1 and 6-7.

[0041] It is evident that, given a fixed amount of raw materials, the production efficiency of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the preparation conditions. Based on the data in the table above, it is clear that the strongest flame retardancy is achieved when the output sheath to core mass ratio is 45:55, while the strongest mechanical properties are obtained when the output sheath to core mass ratio is 35:65. This is because the 45:55 ratio results in the highest flame retardancy, as the flame-retardant functional phase, composed of nano-zirconium phosphate and intrinsically flame-retardant copolyester, constitutes the largest proportion of the flame-retardant functional phase in the monofilament cross-section, thus enhancing the flame retardancy of the monofilament. The total amount of effective components that can be catalyzed to form char within the monofilament of the filament is maximized, thereby forming the most continuous and dense expanded char layer during combustion, achieving the best barrier effect for heat and mass transfer. The mechanical properties are strongest when a 35:65 ratio is used because this ratio retains the proportion of the high-strength intrinsic flame-retardant polyester continuous phase in the core layer to the maximum extent, providing the most solid load-bearing skeleton for the monofilament. At this time, although the thinner skin layer introduces some flexible chain segments, it is not enough to weaken the overall rigidity. At the same time, the nanoparticles in the skin layer can still effectively reinforce and protect the core layer. Thus, the optimal load-bearing combination with a high-strength core layer as the main component and a functionalized skin layer as the auxiliary component is achieved in terms of structure, as obtained from Examples 1 and 8-9.

[0042] Examples 10-17 The corresponding relationship of the preparation methods used for a long-lasting flame-retardant polyester monofilament is shown in the table below.

[0043] Table: Comparison of the application of long-lasting flame-retardant polyester monofilaments in Examples 10-17 Long-lasting flame-retardant polyester monofilaments from Examples 10-17 were extracted and their minimum oxygen concentration (LOI), monofilament breaking strength, and surface condition were tested according to the above measurement steps and standards. The average values ​​of the test results were recorded in the table below.

[0044] Table: Performance test results of Example 1, LOI (Lowest Oxygen Concentration) 10-17, monofilament breaking strength, and surface condition. As can be seen from the table above, the preparation processes of long-lasting flame-retardant polyester monofilaments in Examples 1 and 10-17 all effectively improve the production efficiency of long-lasting flame-retardant polyester monofilaments. Purified terephthalic acid and ethylene glycol are used as basic monomers to construct the polyester molecular backbone. By introducing dicarboxyethylphenylphosphine as a reactive flame-retardant monomer to participate in copolymerization, phosphorus is permanently anchored in the molecular chain in the form of covalent bonds, fundamentally endowing the material with inherent and non-migrating flame-retardant properties. Antimony trioxide, as a highly efficient polycondensation catalyst, ensures that the polymer reaches the required molecular weight, and triphenyl phosphate, as a stabilizer, effectively inhibits thermal degradation during high-temperature processing. In the preparation of the dynamic network precursor, terephthalic acid provides rigidity, adipic acid introduces flexible segments, ethylene glycol serves as a connecting unit, and the key dihydrazide chain extender binds to the polymer through the hydrazide groups at both ends of its molecule. The compound chain reaction introduces dynamic and reversible acylhydrazone chemistry, thereby endowing the material with the ability to form a self-healing network during subsequent heat treatment. Tetrabutyl titanate or dibutyltin dilaurate serves as a catalyst in this step, ensuring synthesis efficiency. In the skin premix, polyester chips serve as a continuous matrix, dynamic network precursor powder serves as a toughening and self-healing functional phase, and surface-treated nano-zirconium phosphate powder serves as a highly efficient char-forming agent and physical reinforcement point. During combustion, it produces a synergistic effect with the intrinsic flame-retardant system, significantly improving flame-retardant efficiency and mechanically enhancing toughness. The composite antioxidant prevents thermo-oxidative aging of the material through a main-auxiliary synergistic mechanism, while the composite lubricant improves melt processing fluidity. Together, they ensure the stability of the spinning process and the long-term durability of the final product, thus achieving the goal of improving the production effect of long-lasting flame-retardant polyester monofilament. Its minimum oxygen concentration (LOI) is 31.6-33.0%, which is considered to be strong flame retardancy; its single filament breaking strength is 4.3-5.0 cN / dtex, which is considered to be strong mechanical properties; its surface condition is qualified, with no obvious damage, fuzzing, or coating peeling, which is considered to be strong durability. It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the proportions of these materials. Based on the data in the table above, it is clear that when preparing polyester chips, the long-lasting flame-retardant polyester prepared using 100 parts purified terephthalic acid, 51 parts ethylene glycol, 4.5 parts 2-carboxyethylphenylphosphonic acid, 0.035 parts antimony trioxide, and 0.025 parts triphenyl phosphate exhibits the strongest flame retardancy and mechanical properties. This is because the relative content of the flame-retardant comonomer 2-carboxyethylphenylphosphonic acid is the highest, ensuring that the maximum amount of phosphorus is firmly bonded in covalent form. By integrating with the polyester molecular backbone, the most solid intrinsic flame retardant foundation is constructed from the source; antimony trioxide provides stable and reliable catalytic activity, while the addition of germanium dioxide can significantly promote the polycondensation reaction to the direction of higher molecular weight and is conducive to the formation of more regular polymer chains, thereby directly improving the intrinsic viscosity and molecular chain rigidity of the final polyester chips; pentaerythritol diphosphite can more effectively inhibit the thermal oxidative degradation and hydrolysis of polymer chains during high-temperature polymerization and subsequent processing, thereby protecting the rigid molecular backbone and key flame retardant structure from damage, as obtained in Examples 1 and 10-13.

[0045] It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the preparation conditions. Based on the data in the table above, it is clear that when preparing polyester chips, increasing the esterification and polycondensation temperatures initially strengthens the flame retardancy and mechanical properties of the resulting long-lasting flame-retardant polyester monofilaments, then weakens them. Esterification at 250℃ and polycondensation at 270℃ yields the longest flame-retardant polyester monofilaments with the strongest flame retardancy and mechanical properties. This is because the appropriate esterification temperature ensures that the reacting monomers, including dicarboxyethylphenylphosphonic acid, can fully participate in the esterification reaction and uniformly integrate into the molecular chain. Simultaneously, it effectively suppresses side reactions such as excessive volatilization or etherification of ethylene glycol, laying the foundation for the formation of a structurally regular prepolymer. The optimal polycondensation temperature, while ensuring a sufficient reaction rate to drive molecular chain growth to the target intrinsic viscosity, minimizes the risk of thermal degradation of the polymer under high temperature and high vacuum, avoiding molecular chain breakage and structural damage to the flame-retardant copolymer units, as obtained from Examples 1 and 14-17.

[0046] Examples 18-23 The corresponding relationship of the preparation methods used for a long-lasting flame-retardant polyester monofilament is shown in the table below.

[0047] Table: Comparison of the application of long-lasting flame-retardant polyester monofilaments in Examples 18-23 Long-lasting flame-retardant polyester monofilaments from Examples 18-23 were extracted and their minimum oxygen concentration (LOI), monofilament breaking strength, and surface condition were tested according to the above measurement steps and standards. The average values ​​of the test results were recorded in the table below.

[0048] Table: Performance test results of lowest oxygen concentration (LOI), monofilament breaking strength, and surface condition in Examples 1 and 23 (18-23) As can be seen from the table above, the preparation processes of long-lasting flame-retardant polyester monofilaments in Examples 1 and 18-23 all effectively improve the production efficiency of long-lasting flame-retardant polyester monofilaments. Purified terephthalic acid and ethylene glycol are used as basic monomers to construct the polyester molecular backbone. By introducing dicarboxyethylphenylphosphine as a reactive flame-retardant monomer to participate in copolymerization, phosphorus is permanently anchored in the molecular chain in the form of covalent bonds, fundamentally endowing the material with inherent and non-migrating flame-retardant properties. Antimony trioxide, as a highly efficient polycondensation catalyst, ensures that the polymer reaches the required molecular weight, and triphenyl phosphate, as a stabilizer, effectively inhibits thermal degradation during high-temperature processing. In the preparation of the dynamic network precursor, terephthalic acid provides rigidity, adipic acid introduces flexible segments, ethylene glycol serves as a connecting unit, and the key dihydrazide chain extender binds to the polymer through the hydrazide groups at both ends of its molecule. The compound chain reaction introduces dynamic and reversible acylhydrazone chemistry, thereby endowing the material with the ability to form a self-healing network during subsequent heat treatment. Tetrabutyl titanate or dibutyltin dilaurate serves as a catalyst in this step, ensuring synthesis efficiency. In the skin premix, polyester chips serve as a continuous matrix, dynamic network precursor powder serves as a toughening and self-healing functional phase, and surface-treated nano-zirconium phosphate powder serves as a highly efficient char-forming agent and physical reinforcement point. During combustion, it produces a synergistic effect with the intrinsic flame-retardant system, significantly improving flame-retardant efficiency and mechanically enhancing toughness. The composite antioxidant prevents thermo-oxidative aging of the material through a main-auxiliary synergistic mechanism, while the composite lubricant improves melt processing fluidity. Together, they ensure the stability of the spinning process and the long-term durability of the final product, thus achieving the goal of improving the production effect of long-lasting flame-retardant polyester monofilament. Its minimum oxygen concentration (LOI) is 31.7-32.8%, which is considered to be highly flame-retardant; its single filament breaking strength is 4.4-4.8 cN / dtex, which is considered to be highly mechanical; its surface condition is qualified, with no obvious damage, fuzzing, or coating peeling, which is considered to be highly durable. It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the proportions of these materials. Based on the data in the table above, it is clear that when preparing the precursor powder, the long-lasting flame-retardant polyester prepared using 100 parts terephthalic acid, 28 parts adipic acid, 65 parts ethylene glycol, 18 parts dihydrazide chain extender, 0.24 parts tetrabutyl titanate, and 0.38 parts dibutyltin dilaurate exhibits the strongest flame retardancy. This is because the amount of adipic acid is the lowest, while the proportion of aromatic terephthalic acid is the highest. This results in the synthesized polymer having the strongest molecular chain rigidity and the best thermal stability, leading to better performance during thermal decomposition. It can form a stable aromatic coke skeleton earlier; the addition of dihydrazide chain extender reaches the highest level, which is equivalent to implanting the densest dynamic hydrazone bond crosslinking points into the rigid molecular chain. Under the high temperature stimulation in the early stage of combustion, these dense dynamic bonds are rapidly activated and undergo violent reversible exchange and recombination reactions, quickly building a continuous and stable crosslinking network in the condensed phase; it can effectively bind the combustible fragments generated by polymer degradation, inhibit their diffusion into the gas phase, and guide and stabilize the formation of the char layer, ultimately catalyzing the generation of a denser, stronger, and more heat-insulating and oxygen-barrier expanded char layer, as obtained in Examples 1, 18-21.

[0049] It is evident that, given a fixed amount of raw materials, the production effect of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the proportions of the raw materials. Based on the data in the table above, it is clear that when preparing the precursor powder, the long-lasting flame-retardant polyester prepared using 100 parts terephthalic acid, 52 parts adipic acid, 78 parts ethylene glycol, 10 parts dihydrazide chain extender, 0.30 parts tetrabutyl titanate, and 0.46 parts dibutyltin dilaurate exhibits the strongest flame retardancy. This is likely due to the high content of adipic acid, which imparts necessary flexibility to the polymer chain, allowing for good compatibility and uniform dispersion with the polyester matrix during processing and subsequent heat treatment. Meanwhile, the rigid aromatic structure of its terephthalic acid still dominates, ensuring the overall thermal stability of the material; the appropriate amount of dihydrazide chain extender ensures that the dynamic hydrazone bonds can be fully activated and exchanged and recombined under the high temperature environment in the early stage of combustion, thereby quickly constructing a three-dimensional network with sufficient crosslinking density but without embrittlement due to excessive crosslinking. It can effectively capture and fix the fragments generated by polymer pyrolysis, and synergistically form a dense, continuous and mechanically strong expanded carbon layer in the synergistic nano-zirconium phosphate in the skin layer. This carbon layer, as an excellent heat and oxygen barrier, greatly slows down the combustion process, as obtained in Examples 1, 18-21.

[0050] It is evident that, given a fixed amount of raw materials, the production efficiency of long-lasting flame-retardant polyester monofilaments can be increased by adjusting the preparation conditions. Based on the data in the table above, it is clear that when preparing the precursor powder, the flame retardancy and mechanical properties of the prepared long-lasting flame-retardant polyester monofilaments initially increase and then decrease with each temperature increase during esterification and polycondensation. The best results were achieved when pre-polymerization began at 225℃, the system temperature was lowered to 200℃, a dihydrazide chain extender was added, and polycondensation was carried out at 250℃. The resulting long-lasting flame-retardant polyester monofilament exhibited the highest flame retardancy and strongest mechanical properties. This is because pre-polymerization at this temperature efficiently forms a prepolymer with a certain degree of polymerization. This lays the foundation for subsequent chain extension. The system temperature is then lowered to this temperature before adding the thermosensitive dihydrazide chain extender. This crucial cooling operation effectively prevents premature decomposition or side reactions of the chain extender at high temperatures, ensuring that its hydrazide end groups can react fully and controllably with the ester or carboxyl groups at the ends of the prepolymer chain. This allows the dynamic hydrazone bonds to be introduced completely and densely into the polymer chain. Finally, the temperature is further increased for final polycondensation. This high-temperature condition, based on the successful introduction of dynamic bonds, provides a strong driving force for the polycondensation reaction, enabling the polymer molecular chain to grow further and reach a higher molecular weight, as obtained in Examples 1 and 22-23.

[0051] This specific embodiment is merely an explanation of the present invention and not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A long-lasting flame-retardant polyester monofilament, characterized in that, The raw materials for preparing the long-lasting flame-retardant polyester monofilament, by weight, include: 100 parts polyester chips, 15-25 parts precursor powder, 8-12 parts zirconium phosphate powder, 0.6-1.2 parts composite antioxidant, and 0.5-1.0 parts composite lubricant.

2. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The method for preparing the polyester chips includes the following steps: C1. Purified terephthalic acid, ethylene glycol and 2-carboxyethylphenylphosphonic acid are added to a reaction vessel. Under the protection of nitrogen gas at 5 L / min, the esterification reaction is completed at a temperature of 240-255℃ and a stirring speed of 100 r / min to obtain the esterified product. C2. The esterification product obtained in C1 is added to antimony trioxide catalyst and triphenyl phosphate stabilizer, and then transferred to a polycondensation reactor. The melt polycondensation reaction is carried out at a temperature of 265-280℃ and a pressure of less than 100MPa for 3 hours. The melt is then discharged and granulated and dried underwater to obtain polyester chips.

3. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The components and weight proportions of the raw materials for preparing the polyester chips are as follows: 100 parts purified terephthalic acid, 45-53 parts ethylene glycol, 2.6-4.5 parts 2-carboxyethylphenylphosphonic acid, 0.008-0.035 parts antimony trioxide, and 0.012-0.025 parts triphenyl phosphate.

4. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The method for preparing the precursor powder includes the following steps: A1. Terephthalic acid, adipic acid, and ethylene glycol were added to a polymerization reactor. Under a nitrogen atmosphere, tetrabutyl titanate (an esterification catalyst) and dibutyltin dilaurate (a polycondensation catalyst) were added. A pre-polycondensation reaction was initiated at 210-225°C and continued for 60 min. Subsequently, the system temperature was lowered to 190-200°C, and then dihydrazide chain extender was added and stirred at 100 r / min for 30 min. Next, a polycondensation reaction was carried out at 230-250°C, a pressure below 200 MPa, and a stirring speed of 30 r / min for 2 h to obtain the copolymer. A2. The copolymer obtained in A1 is cooled, granulated, pulverized using a mechanical pulverizer, and passed through a 100-mesh sieve to obtain precursor powder.

5. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The components and weight proportions of the raw materials for preparing the precursor powder are as follows: 100 parts terephthalic acid, 28-60 parts adipic acid, 65-82 parts ethylene glycol, 8-18 parts dihydrazide chain extender, 0.24-0.31 parts tetrabutyl titanate, and 0.38-0.48 parts dibutyltin dilaurate.

6. The long-lasting flame-retardant polyester monofilament according to claim 4, characterized in that: The dihydrazide chain extender is specifically a dihydrazide chain extender containing a dynamic covalent bond of acylhydrazone.

7. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The zirconium phosphate powder is specifically a porous nano-zirconium phosphate powder that has undergone surface treatment with aminopropyltriethoxysilane.

8. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a mass ratio of 1:

1. The compound antioxidant is composed of antioxidant 1010 and antioxidant 168 mixed in a mass ratio of 1:

1.

9. The long-lasting flame-retardant polyester monofilament according to claim 1, characterized in that: The surface treatment solution is composed of aminopropyltriethoxysilane, aqueous fluorinated polyurethane dispersion, deionized water, and anhydrous ethanol in a mass ratio of 2:10:44:

44.

10. The method for preparing long-lasting flame-retardant polyester monofilament according to any one of claims 1-9, characterized in that, The preparation method of the long-lasting flame-retardant polyester monofilament includes the following steps: S1. Polyester chips, precursor powder, zirconium phosphate powder, composite antioxidant and lubricant are mixed and put into a high-speed mixer and mixed at 1000 r / min for 20 min to obtain a skin premix; then, the skin premix and the same mass of polyester chips are placed in a dehumidifying dryer and dried in dry air at 130℃ for 7 h to obtain dried skin premix and dried polyester chips. S2. The dried polyester chips obtained in S1 are fed into the core layer screw extruder, and the dried sheath premix obtained in S1 is fed into the sheath screw extruder. The sheath screw heating zone is heated to 265-275℃, the core screw heating zone is heated to 260-270℃, and the output mass ratio is 35-45:55-65. The mixture is then extruded from a circular spinneret with a diameter of 0.25mm and cooled and solidified under annular air blowing conditions at a temperature of 22℃ and a wind speed of 0.5m / s to obtain nascent fibers. S3. The nascent fibers obtained in S2 are introduced into a multi-stage hot stretching unit and subjected to the first stage of stretching on a hot roller at a temperature of 90°C and a stretching ratio of 3.

0. The second stage of stretching is subjected to the hot roller at a temperature of 145°C and a stretching ratio of 2.

0. The fibers are then subjected to relaxation heat setting on a heat setting roller at a temperature of 180°C, a setting time of 1.2s, and a total stretching ratio of 6.0 to obtain the treated monofilament. S4. The treated monofilament obtained in S3 is passed through an impregnation tank containing surface treatment liquid at a speed of 20 m / min, during which the liquid content of the monofilament is controlled to be 5% of its own weight. Then, the liquid-laden monofilament is introduced into a hot air drying tunnel, pre-dried at 105°C for 60 s, then cured at 165°C for 80 s, and then wound through a guide to obtain long-lasting flame-retardant polyester monofilament.

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