Polyamide 5X industrial yarn, method for producing the same, and its use

Abstract

To provide a polyamide 56 industrial yarn having both excellent heat resistance and mechanical properties and a manufacturing method thereof.SOLUTION: In a polyamide 56 industrial yarn, a raw material for manufacturing the polyamide 56 industrial yarn includes at least a high-viscosity polyamide 56 resin; the high-viscosity polyamide 56 resin has a relative viscosity in a 96%-sulfuric acid of 2.7-4.5, an oligomer content of 0.2-1.0 wt.%, a number-average molecular weight of 18,000-40,000, a molecular-weight distribution of 0.8-1.8, a water content of 200-800 ppm, and an amino content of 20-50 mmol / kg; the polyamide 56 industrial yarn includes a thermal stabilizer; the thermal stabilizer includes one of copper acetate, potassium iodide, copper chloride, cuprous iodide, copper oxide, cuprous oxide, and combinations of these; and the thermal stabilizer is added at an amount of 10-2800 ppm based on a total weight of manufacturing materials.SELECTED DRAWING: None

Description

【Technical Field】 【0001】 The present invention relates to the technical field of polyamide materials, and provides polyamide 5X industrial yarn, a manufacturing method thereof, and its use. 【Background Art】 【0002】 Industrial yarn can be manufactured by two processes, one process being a direct melt spinning process and the other being an indirect chip spinning process by solid phase sticking. Today, some of polyamide 66 and polyethylene terephthalate are sometimes manufactured by the direct melt spinning method. However, polyamide 6 contains 8-10% by weight of monomers that need to be removed through a monomer removal process, and thus cannot currently be manufactured by the direct melt spinning process. 【0003】 Dacron·Chinlon industrial yarns have properties such as high strength, low elongation, dimensional stability, fatigue resistance, and aging resistance. Therefore, they are widely used in fields such as tire cords, canvases, conveyor belts, airbags, parachutes, ropes, safety belts, industrial filter cloths, and tents. Various application fields impose relatively high requirements on the heat resistance of industrial yarn materials. Currently, this is mainly achieved by adding and blending a heat stabilizer masterbatch. However, the heat stabilizer masterbatch is expensive. Furthermore, the spinning manufacturer needs to equip an online masterbatch device during spinning, which increases the equipment investment. Also, it is necessary to address the compatibility between the heat stabilizer masterbatch and the base material. If the masterbatch is not added uniformly, the filaments break during spinning, which reduces the manufacturing yield of industrial yarn and even affects the mechanical properties of the fibers. 【0004】 CN 110055602A discloses high-strength polyamide 56 industrial yarn and a method for manufacturing the same. Conventional polyamide 56 chips are used in spinning, and the polyamide 56 chips are not heat-resistant, resulting in industrial yarns with poor heat resistance, suitable for sewing threads, tire cords, airbag threads, etc. Release cloth, water cloth It cannot be used in fields requiring high heat resistance. It employs a high-speed winding process with a winding speed exceeding 4000 m / min. Due to the high winding speed, the residence time of fibers on different hot rollers is relatively short, meaning that the high-temperature curing time of the fibers is shortened. Furthermore, by employing a process with a low elongation ratio, fibers with low crystallinity, low orientation, low strength, and poor dimensional stability are produced. [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 The first object of the present invention is to provide a polyamide 5X industrial yarn having both excellent heat resistance and mechanical properties. The polyamide 5X industrial yarn has a heat resistance tensile strength retention rate of 90% or more after treatment at 180°C for 4 hours, a heat resistance tensile strength retention rate of 90% or more after treatment at 230°C for 30 minutes, and / or a dry heat shrinkage rate of 8.0% or less. Polyamide 5X comprises one of polyamide 56, polyamide 510, polyamide 512, polyamide 513, or polyamide 514. Preferably, it is polyamide 56 or polyamide 510. 【0006】 According to the present invention, the quality of polyamide 5X, particularly polyamide 56 resin, is optimized by adjusting its viscosity, oligomer content, molecular weight and molecular weight distribution, and water content. Secondly, the spinning process of polyamide 5X industrial yarn is optimized to improve its crystallinity and degree of orientation, increase the set temperature and winding overfeed ratio, and reduce subsequent stress relaxation. Thus, the present invention provides polyamide 56 industrial yarn having excellent mechanical properties and dimensional stability, having a breaking strength of 6.5 cN / dtex or more; no more than two filament breaks every 24 hours; a production yield of 90% or more; a boiling water shrinkage rate of 8.0% or less; a fineness of 100 to 3500 dtex; an elongation at break of 26% or less; a crystallinity of 70% or more; and / or a degree of orientation of 80% or more. 【0007】 During the spinning process of polyamide fibers, it is necessary to control the moisture content of the resin, and it is generally required to be within the equilibrium moisture content range. If the moisture content of the resin is too low during spinning, a melt tackifying reaction occurs during melting, reducing the amino content and worsening the fluidity of the molten material. This is undesirable for subsequent stretching and can cause filament breakage and a decrease in fiber strength. If the moisture content is too high, a melt degradation reaction occurs during melting, increasing the amino content, making filament breakage more likely, and ultimately leading to a decrease in manufacturing yield. When the moisture content of polyamide 56 resin is controlled within the range of 300 to 800 ppm during spinning, the de-oiled polyamide 56 industrial yarn has a relative viscosity of 2.7 to 4.5, and the absolute difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin is 0.12 or less; the de-oiled yarn has an amino content of 20 to 50 mmol / kg, and the absolute difference between the amino content of the de-oiled yarn and the amino content of the raw material resin is 5 or less. By reducing the fluctuation range in terms of viscosity and amino acid content of the de-oiled yarn, the melt uniformity of polyamide 56 is improved, filament breakage is reduced, spinnability is improved, and the production yield of the prepared polyamide 56 industrial yarn can be increased to over 90%. 【0008】 A second object of the present invention is to provide a method for producing polyamide 5X industrial yarn, and in particular polyamide 56 industrial yarn. 【0009】 A third object of the present invention is to use polyamide 5X industrial yarn, particularly polyamide 56 industrial yarn, for sewing threads, tire cords, airbag threads, Release cloth, water cloth, The objective is to provide applications in the fields of canvas, safety belts, ropes, fishing nets, industrial filter cloths, conveyor belts, parachutes, tents, bags, and suitcases. [Means for solving the problem] 【0010】 To achieve the above objective, the present invention provides the following solutions. 【0011】 [Polyamide 5X Industrial Yarn] Taking polyamide 56 industrial yarn as an example, the copper ion content in the polyamide 56 industrial yarn according to the present invention is 10 to 1000 ppm, preferably 30 to 500 ppm, more preferably 50 to 200 ppm, the heat tensile strength retention rate of the polyamide 56 industrial yarn after treatment at 180°C for 4 hours is 90% or more, preferably 94% or more, more preferably 98% or more, and / or the heat tensile strength retention rate after treatment at 230°C for 30 minutes is 90% or more, preferably 93% or more, more preferably 96% or more, and / or the dry heat shrinkage rate of the polyamide 56 industrial yarn is 8.0% or less, preferably 6.0% or less, more preferably 4.0% or less. 【0012】 Polyamide 56 industrial yarn contains a heat stabilizer; preferably, the heat stabilizer comprises one of the following: copper acetate, potassium iodide, copper chloride, cuprous iodide, copper oxide, cuprous oxide, or a combination thereof; preferably, the heat stabilizer is added in an amount of 10 to 2800 ppm, and preferably 10 to 2500 ppm, based on the total weight of the raw materials used in production. 【0013】 Preferably, the heat stabilizer is a composition of copper acetate and potassium iodide, with a molar ratio of copper acetate to potassium iodide of 1:1 to 15, preferably 1:2 to 10, and more preferably 1:6 to 8, and preferably 100 to 500 ppm of copper acetate and 500 to 2500 ppm of potassium iodide. 【0014】 The polyamide 56 industrial yarn has a tensile strength of 6.5 cN / dtex or higher, preferably 7.0 cN / dtex or higher, and more preferably 8.0 cN / dtex or higher. 【0015】 The de-oiled polyamide 56 industrial yarn has a relative viscosity of 2.7 to 4.5, and the absolute value of the difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin is 0.12 or less, preferably 0.10 or less, and more preferably 0.08 or less. 【0016】 The de-oiled polyamide 56 industrial yarn has an amino acid content of 20 to 50 mmol / kg, and the absolute difference between the amino acid content of the de-oiled yarn and the amino acid content of the raw material resin is 5 or less, preferably 3 or less, and more preferably 2 or less. 【0017】 The filaments of the polyamide 56 industrial yarn break no more than twice every 24 hours, preferably no more than once every 24 hours, and more preferably zero times every 24 hours, and the production yield of the polyamide 56 industrial yarn is 90% or more, preferably 93% or more, and even more preferably 96% or more. 【0018】 Polyamide 56 industrial yarn has a boiling water shrinkage rate of 8.0% or less, preferably 7.0% or less, more preferably 6.0% or less, and / or polyamide 56 industrial yarn has a fineness of 100 to 3,500 dtex, preferably 200 to 2,500 dtex, more preferably 300 to 1,800 dtex, polyamide 56 industrial yarn has an elongation at break of 26% or less, preferably 22% or less, and / or polyamide 56 industrial yarn has a crystallinity of 70% or more, preferably 72% or more, more preferably 74% or more, and / or polyamide 56 industrial yarn has an orientation of 80% or more, preferably 82% or more, more preferably 84% or more. 【0019】 The raw materials for the production of polyamide 56 industrial yarn include at least 1,5-pentanediamine and adipic acid; or polyamide 56 obtained by polymerizing 1,5-pentanediamine and adipic acid as monomers. 【0020】 1,5-pentanediamine is prepared from bio-based raw materials by a fermentation process or an enzymatic conversion process. Preferably, 1,5-pentanediamine is prepared from bio-based raw materials by a fermentation process or an enzymatic conversion process. For example, the method for producing 1,5-pentanediamine disclosed in CN109536542A is employed. 【0021】 [Method for manufacturing polyamide 5X industrial yarn] Taking polyamide 56 industrial yarn as an example, this method includes the following steps: Here, polyamide 56 industrial yarn can be prepared by two processes, namely, a direct melt spinning process or a tip spinning process; (1) 1,5 - pentanediamine and adipic acid are polymerized to obtain a high - viscosity polyamide 56 melt, which is conveyed to a spinning beam by a melt booster pump and spun directly or using polyamide 56 chips, that is, first, a low - viscosity polyamide 56 resin is prepared, then a high - viscosity polyamide 56 resin is obtained by solid - phase adhesion imparting, and this high - viscosity polyamide 56 resin is heated to a molten state to form a spinning polyamide 5X melt; Here, in solid - phase adhesion imparting, the low - viscosity polyamide 56 resin is thickened by drying at a high temperature, preferably solid - phase adhesion imparting is carried out at a temperature of 120 - 180°C, preferably 150 - 160°C, and the drying time is 10 - 50 hours, preferably 15 - 30 hours. In solid - phase adhesion imparting, moisture is removed by drying at a high temperature, and the polycondensation reaction is continued to obtain a high - viscosity resin; (2) The polyamide 56 melt is drawn to form a spun yarn precursor; and (3) The spun yarn precursor is processed to obtain a polyamide 56 industrial yarn. 【0022】 Here, the heat stabilizer is added during the polymerization of 1,5 - pentanediamine and adipic acid in step (1), or is injected online in the form of a heat stabilizer masterbatch before cutting the polymer melt into pellets, or is blended in the form of a heat stabilizer masterbatch during spinning. 【0023】 When the polyamide 5X industrial yarn is a polyamide 510 industrial yarn, 1,5 - pentanediamine and sebacic acid can be polymerized. 【0024】 In some embodiments of the present invention, the content of copper ions in the heat stabilizer masterbatch is 0.5 - 10 wt%, preferably 0.8 - 5 wt%, and more preferably 1.2 - 3 wt%. 【0025】 In some embodiments of the present invention, the heat stabilizer masterbatch is added in an amount of 0.3 - 5.0 wt%, preferably 0.5 - 3.0 wt%, and more preferably 0.8 - 2.0 wt%. 【0026】 In some embodiments of the present invention, the substrate for the heat stabilizer masterbatch is any of polyamide 6, polyamide 56, polyamide 66, polyamide 510, polyamide 610, polybutylene terephthalate, or a combination thereof; preferably polyamide 6, polyamide 56 and / or polyamide 510; and more preferably polyamide 6 and / or polyamide 56. 【0027】 In some embodiments of the present invention, a method for producing a heat stabilizer masterbatch includes the following steps: (1) Dry the substrate under vacuum or in an inert gas, then pulverize it into a powder; (2) The powder obtained in step (1) is mixed with a heat stabilizer and other additives, and the mixture is pelletized. Specifically, twin-screw molten extrusion can be used for pelletization. Preferably, the processing temperature of each zone of the twin-screw extruder is 180 to 285°C, the screw rotation speed is 25 to 350 r / min, the vacuum level is -0.1 MPa or less, and the filter screen is in the range of 80 to 200 mesh. Preferably, the base material is polyamide 56, the processing temperature of each zone of the twin-screw extruder is 260 to 275°C, the screw rotation speed is 50 to 350 r / min, the vacuum level is -0.1 MPa or less, and the filter screen is in the range of 100 to 150 mesh. The heat stabilizer is added in an amount of 0.5 to 20% by weight relative to the base material. 【0028】 In some embodiments of the present invention, the heat stabilizer is a composition of copper acetate and potassium iodide, where the molar ratio of copper acetate to potassium iodide is 1:1 to 15, preferably 1:2 to 10, and more preferably 1:5 to 8. In some embodiments of the present invention, the heat stabilizer is cuprous iodide. Other additives include at least an antioxidant and / or a lubricant. 【0029】 According to the present invention, polyamide 56 industrial yarn achieves better heat resistance and mechanical properties by adding the above-mentioned heat stabilizer during polymerization. The inventors posit that the reasons for this are as follows: First, since the polyamide 56 molten material has good fluidity, the heat stabilizer can be uniformly distributed in the polyamide 56 resin, and it has good compatibility with the polyamide 56 resin. Second, polyamide 56 has a structure with an odd-even carbon arrangement and a high proportion of amide bonds, and some amide bonds on different molecular chains are not bonded. After adding a heat stabilizer containing copper ions, the copper ions can perform a good complexing function between amide bonds, so the bonds between polyamide 56 molecular chains become closer, the intermolecular forces become relatively large, and therefore the mechanical properties of the prepared industrial yarn increase. 【0030】 In some embodiments of the present invention, other additives may also be added during the spinning of polyamide 56 industrial yarn, the other additives including any one of the following: matting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent whitening agents, and antistatic agents, or a combination thereof; preferably, the other additives are added in an amount of 0 to 5% by weight based on the total weight of the raw materials for production. 【0031】 Examples of antioxidants include, but are not limited to, one, two, or a combination of commercially available antioxidants 1010, 1098, 168, and sodium hypophosphite. Examples of lubricants include, but are not limited to, commercially available P861 / 3.5, PTS HOB 7119, and commercially available ET132, ET141, and wax OP. 【0032】 In step (1), the polymerization of polyamide 56 specifically includes the following steps: (1-1) A solution of polyamide 56 salt is obtained by homogeneously mixing 1,5-pentanediamine, adipic acid, and water under an inert gas or vacuum; where the molar ratio of 1,5-pentanediamine to adipic acid is (0.95-1.2):1; the inert gas includes nitrogen, argon, or helium, or a combination thereof; In some embodiments of the present invention, the concentration of the polyamide 56 salt solution is 40% to 85%; 【0033】 (1-2) Heat the polyamide 56 salt solution, increase the pressure in the reaction system to 0.3-2.5 MPa, degas, maintain the pressure, then reduce the pressure in the reaction system to 0-0.2 MPa, and evacuate to a vacuum of -(0.01-0.1) MPa (gauge pressure) to obtain molten polyamide 56; Here, preferably, the temperature of the reaction system at the pressure-maintaining end is 230-275°C; and / or preferably, the temperature of the reaction system at the depressurization end is 240-285°C; and / or preferably, the temperature at the exhaust end is 265-295°C. 【0034】 In some embodiments of the present invention, in step (1), the low viscosity polyamide 56 resin in 96% sulfuric acid has a relative viscosity of 2.0 to 2.7, preferably 2.2 to 2.6, and more preferably 2.4 to 2.5. 【0035】 In some embodiments of the present invention, in step (1), the high viscosity polyamide 56 resin in 96% sulfuric acid has a relative viscosity of 2.7 to 4.5, preferably 3.2 to 4.0, and more preferably 3.4 to 3.6; and / or the high viscosity polyamide 56 resin has an oligomer content of 0.2 to 1.0 wt%, and preferably 0.4 to 0.6 wt%; and / or the high viscosity polyamide 56 resin has a number average molecular weight distribution of 18,000 to 40,000, and preferably 25,000 to 30,000, and / or preferably 0.8 to 1.8. and preferably having a molecular weight distribution of 1.2 to 1.5; and / or in some embodiments of the present invention, the high viscosity polyamide 56 resin has a water content of 200 to 800 ppm, preferably 300 to 750 ppm, more preferably 350 to 700 ppm, and even more preferably 400 to 600 ppm; and / or the high viscosity polyamide 56 resin has an amino content of 20 to 50 mmol / kg, preferably 24 to 45 mmol / kg, more preferably 28 to 40 mmol / kg, and even more preferably 32 to 36 mmol / kg. 【0036】 In some embodiments of the present invention, heating in step (1) is carried out in a screw extruder, which includes five heating zones, the temperature of the first zone being 250-290°C, the temperature of the second zone being 260-300°C, the temperature of the third zone being 270-320°C, the temperature of the fourth zone being 280-330°C, and the temperature of the fifth zone being 280-320°C. 【0037】 In some embodiments of the present invention, the spinning process in step (2) includes the following steps: a step of forming a spun yarn by ejecting polyamide 56 resin through a spinneret plate of a spinning beam. 【0038】 The temperature of the spinning beam is preferably 270-330°C, more preferably 280-310°C, even more preferably 290-300°C, and even more preferably 293-297°C; and / or the pressure of the spinning pack of the spinning beam is 8-25 MPa, preferably 12-20 MPa, and even more preferably 15-18 MPa; and / or the draw ratio of the spinning die of the spinning die plate is 50-400, preferably 70-300, even more preferably 80-200, and even more preferably 90-100. 【0039】 In some embodiments of the present invention, in step (3), the processing step includes: insulating, cooling, spinning, drawing, and winding the spun yarn coming out of the spinneret orifice to obtain polyamide 56 industrial yarn; Insulation is preferably carried out with an annealing device, with an annealing temperature of 150-280°C, more preferably 200-240°C; the annealing length is 10-80 mm, more preferably 20-50 mm; cooling is carried out with rapid cooling air, with an air velocity of 0.3-2.0 m / s, more preferably 0.6-1.5 m / s; the air temperature of the rapid cooling air is 15-25°C, more preferably 17-23°C, even more preferably 19-22°C, and / or the humidity of the rapid cooling air is 60-80%, even more preferably The yield is 65-75%; and / or the winding tension when winding the spun yarn into shape is 50-300 cN, preferably 80-200 cN, more preferably 100-160 cN, and even more preferably 120-140 cN; or the winding speed is 2,000-3,800 m / min, preferably 2,500-3,500 m / min, and even more preferably 2,800-3,000 m / min; and / or the winding overfeed ratio is 5% or less, preferably 4% or less, and even more preferably 3% or less. 【0040】 In some embodiments of the present invention, the stretching is carried out in four or more steps, preferably the stretching process includes: firstly, feeding the spun yarn through a godet roller to a first pair of hot rollers and performing a first-stage stretching between the first pair of hot rollers and a second pair of hot rollers; secondly, performing a second-stage stretching between the second pair of hot rollers and a third pair of hot rollers; thirdly, performing a third-stage stretching and a first heat-setting between the third pair of hot rollers and a fourth pair of hot rollers; and then, performing a fourth-stage stretching and a second heat-setting between the fourth pair of hot rollers and a fifth pair of hot rollers; Preferably, the total elongation ratio is 4.0 to 6.0; The temperature of the first heat set is 180-250°C, preferably 200-240°C; and / or the temperature of the second heat set is 200-240°C, preferably 220-230°C. [Effects of the Invention] 【0041】 The advantageous effects of the technical solution according to the present invention include the following: First, the raw materials for producing the polyamide 5X industrial yarn of this invention are green materials prepared by biological processes. They do not rely on petroleum resources and do not cause serious environmental pollution. Therefore, they can reduce carbon dioxide emissions and the greenhouse effect. 【0042】 Secondly, the polyamide 5X industrial yarn of the present invention has good heat resistance, mechanical properties, and dimensional stability. 【0043】 Thirdly, in the method for producing polyamide 5X industrial yarn according to the present invention, a heat stabilizer can be added during polymerization, so the polymerization is in situ polymerization. When thoroughly mixed, the heat stabilizer can be evenly distributed in the polyamide 5X resin and does not affect spinning. Furthermore, filament breakage is extremely rare, and the production yield is increased. 【0044】 Fourth, the polyamide 5X industrial yarn according to the present invention can be manufactured by directly using conventional equipment for producing polyamide 6 and polyamide 66 without modifying conventional spinning equipment. Instead, by optimizing the quality of the polyamide 5X resin and the spinning process, the manufacturing yield can be increased and manufacturing costs can be reduced, which represents a significant benefit for spinning manufacturers. [Modes for carrying out the invention] 【0045】 To further clarify the object, technical solution, and advantages of the present invention, the technical solution of the present invention is described below clearly and completely with reference to the examples. Obviously, the examples described are only a portion, but not all, of the examples of the present invention. All other examples that can be obtained by those skilled in the art based on the examples of the present invention and without creative work are within the scope of the protection of the present invention. 【0046】 The physical properties of the products obtained in the following examples and comparative examples were measured according to the following methods. (1) Fineness: Measured according to GB / T14343. (2) Breaking strength: Measured according to GB / T14344-2008. (3) Elongation at fracture: Measured according to GB / T14344-2008. 【0047】 (4) Heat-resistant breaking strength retention rate: Heat-resistant breaking strength retention rate = ((Breaking strength before heat treatment - Breaking strength after heat treatment) / Breaking strength before heat treatment) * 100%. Breaking strength is measured according to GB / T14344-2008. An oven is used as the heat treatment apparatus. The oven temperature is 180°C and the treatment time is 4 hours, or the oven temperature is 230°C and the treatment time is 30 minutes. 【0048】 (5) Dry heat shrinkage rate: Measured according to FZ / T50004 with a heat treatment temperature of 180°C. 【0049】 (6) Boiling water shrinkage rate: This is measured in accordance with GB / 6505-2008 "Method for testing the heat shrinkage of artificial filament yarn". Specifically, a section of polyamide industrial yarn is taken, pre-applied with a tension of 0.05 ± 0.005 cN / dtex, marked at two points 50.00 cm apart, wrapped in gauze, boiled in boiling water for 30 minutes, the sample is dried, the length between the two markings is measured, and the boiling water shrinkage rate is calculated using the following formula: Boiling water contraction rate = ((Initial length - Length after contraction) / Initial length) * 100% 【0050】 (7) Relative viscosity: The relative viscosity of de-oiled polyamide yarn (unfinished spun yarn) and the relative viscosity of the resin are measured using an Ubbelohde viscometer with concentrated sulfuric acid following the procedure below: Precisely weigh 0.25±0.0002g of a dried polyamide resin sample or its staple fibers, add 50mL of concentrated sulfuric acid (96%) for dissolution, and measure and record the flow time t0 of the concentrated sulfuric acid and the flow time t of the polyamide 56 tip or staple fiber sample solution in a water bath at a constant temperature of 25°C. Relative viscosity is calculated according to the following formula: Relative viscosity VN=t / t0; t represents the flow time of the solution, and t0 represents the solvent flow time. 【0051】 (8) Moisture content: Measured by a Karl Fischer water titrator. (9) Crystallinity and orientation: Using a D / max-2550PC X-ray diffractometer manufactured by Rigaku Corporation (Japan), the Cu target wavelength was measured. 【number】 Fiber samples were analyzed under conditions of voltage 20-40kV, current 10-450mA, and measurement angle 2θ in the range of 5-40°. The polyamide 56 industrial yarn samples used for crystallinity measurement were sufficiently shredded, and the sample mass was greater than 0.2g. Polyamide 56 industrial yarn samples used for microcrystalline orientation measurement were thoroughly combed into bundles with a length of 30mm for testing. Software such as Origin was used for data processing to analyze and calculate the crystallinity and orientation of the fibers. 【0052】 The following formula is used to calculate the degree of crystallinity: 【number】 During the ceremony, 【number】 This is the total diffraction integral intensity of the crystalline portion. 【number】 This represents the scattering integral intensity of the amorphous region. 【0053】 The following formula is used to calculate the degree of orientation: 【number】 Here, Hi is the full width at half maximum of the i-th peak. 【0054】 (10) Manufacturing yield: Manufacturing yield = ((Total amount of resin used - Amount of finished product) / Total amount of resin used) * 100% (11) Number-average molecular weight: Measured using standard GPC. (12) Molecular weight distribution: Measured by gel permeation chromatography (GPC). 【0055】 (13) Oligomer content test: Measured by water extraction (gravimetric analysis) as follows: Accurately weigh approximately 8 g of polyamide 56 resin dried at 130°C for 7 hours and place in a 500 mL round-bottom flask. Add 400 g of water. After refluxing in a heated mantle for 36 hours, decant the solution. Dry the particles in a constant-weight beaker at 130°C for 7 hours, then seal in an aluminum plastic bag, cool, and weigh. The weight loss is calculated. The polyamide 56 resin is prepared according to the methods disclosed in CN108503826A and CN108503824A and has a relative viscosity of 2.7-4.5. 【0056】 (14) Amino acid content: Measured using an automatic titrator. (15) Filament breakage: Manually count the number of times a filament breaks during spinning. 【0057】 (16) Manufacturing yield: The weight percentage of industrial yarn obtained after spinning, based on the weight of the resin used. 【0058】 Table 1 below shows the absolute difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin, the absolute difference between the amino content of the de-oiled yarn and the amino content of the raw material resin, filament breakage (times / 24hr), and manufacturing yield (%) in the following examples and comparative examples. The properties of the obtained polyamide 56 industrial yarn are shown in Table 2 below. 【0059】 Example 1: Polyimide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and copper acetate was added as a heat stabilizer in an amount of 200 ppm based on the total weight of the raw materials to obtain a 60% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.05:1; 【0060】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.2 MPa, degas the system, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.05 MPa at 285°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0061】 (3) A high-viscosity polyamide 56 resin was prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness was 155°C, the drying time was 20 hours, the relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.4, the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.3, the oligomer content was 0.8% by weight, the number-average molecular weight was 30,000, the molecular weight distribution was 1.6, the water content was 400 ppm, and the amino acid content was 36.5 mmol / kg. 【0062】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material; heating was performed using a screw extruder; the screw extruder had five heating zones, specifically the first zone with a temperature of 255°C, the second zone with a temperature of 270°C, the third zone with a temperature of 280°C, the fourth zone with a temperature of 290°C, and the fifth zone with a temperature of 300°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 290°C, the pack pressure was 15 MPa, and the spinneret draw ratio was 150; 【0063】 (2) The spun yarn is insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; Insulation was performed using an annealing device, with an annealing temperature of 220°C and an annealing length of 20 mm. Cooling was performed using rapid-cooling air, with an air velocity of 1.2 m / s, an air temperature of 22°C, and a humidity of 70%. 【0064】 The drawing process consisted of four stages: first, supplying the spun yarn to a first pair of hot rollers via a godet roller; second, performing a first-stage drawing between the first pair of hot rollers and a second pair of hot rollers; third, performing a second-stage drawing between the second pair of hot rollers and a third pair of hot rollers; fourth, performing a third, and first-stage drawing and first-stage heat setting between the third and fourth pair of hot rollers; and fifth, performing a fourth, and second-stage drawing and second-stage heat setting between the fourth and fifth pair of hot rollers. The total drawing ratio was 5.0, the temperature for the first-stage heat setting was 220°C, and the temperature for the second-stage heat setting was 230°C. The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 3500 m / min; and the winding overfeed ratio was 2%. 【0065】 Example 2: Polyamide 56 industrial yarn (830 dtex / 192 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and copper acetate was added as a heat stabilizer in an amount of 500 ppm based on the total weight of the raw materials to obtain a 60% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; 【0066】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.3 MPa, degas it, maintain the pressure at 255°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0 MPa at 265°C when the pressure reduction is complete, and evacuate to a vacuum of -0.08 MPa at 275°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0067】 (3) A high-viscosity polyamide 56 resin was prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness was 160°C and the drying time was 18 hours. The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.5, the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.5, the oligomer content was 0.6% by weight, the number-average molecular weight was 33,000, the molecular weight distribution was 1.5, the water content was 450 ppm, and the amino acid content was 33.5 mmol / kg. 【0068】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten mass; heating was performed using a screw extruder; the screw extruder had five heating zones, specifically the first zone with a temperature of 265°C, the second zone with a temperature of 275°C, the third zone with a temperature of 285°C, the fourth zone with a temperature of 295°C, and the fifth zone with a temperature of 305°C; the polyamide 56 molten mass was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 295°C, the pack pressure was 18 MPa, and the spinneret draw ratio was 180; 【0069】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 230°C and a annealing length of 30 mm; cooling was performed with rapid cooling air at an air velocity of 0.8 m / s, an air temperature of 23°C, and a humidity of 75%; the winding tension when winding the spun yarn into shape was 80 cN; the winding speed was 3,000 m / min; and the winding overfeed ratio was 3%. The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 4.8, the temperature of the first stage heat set was 225°C, and the temperature of the second stage heat set was 240°C. 【0070】 Example 3: Polyamide 56 industrial yarn (550 dtex / 96 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and cuprous iodide was added as a heat stabilizer in an amount of 150 ppm based on the total weight of the raw materials to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; 【0071】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.3 MPa, degas the system, maintain the pressure at 240°C when the pressure maintenance is complete, reduce the pressure to 0.1 MPa at 270°C when the pressure reduction is complete, and evacuate to a vacuum of -0.05 MPa at 280°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0072】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 160°C and the drying time is 22 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.6, while the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.0. The oligomer content was 0.8% by weight, the number-average molecular weight was 30,000, the molecular weight distribution was 1.6, the water content was 400 ppm, and the amino acid content was 42.5 mmol / kg. 【0073】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 248°C, the second zone 263°C, the third zone 276°C, the fourth zone 285°C, and the fifth zone 293°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 285°C, the pack pressure was 16 MPa, and the spinneret draw ratio was 100; 【0074】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 220°C and a annealing length of 25 mm; cooling was performed with rapid cooling air at an air velocity of 1.4 m / s, an air temperature of 22°C, and a humidity of 65%; the winding tension when winding the spun yarn into shape was 55 cN; the winding speed was 2,800 m / min; and the winding overfeed ratio was 2.5%. The drawing process was the same four-step drawing process as in Example 1, except that the total drawing ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 235°C. 【0075】 Example 4: Polyamide 56 industrial yarn (550 dtex / 96 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and cuprous iodide was added as a heat stabilizer in an amount of 250 ppm based on the total weight of the raw materials to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.12:1; 【0076】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.4 MPa, degas it, maintain the pressure at 245°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.07 MPa at 280°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0077】 (3) A high-viscosity polyamide 56 resin was prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness was 150°C and the drying time was 25 hours. The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.55, the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 2.9, the oligomer content was 0.8% by weight, the number-average molecular weight was 28,000, the molecular weight distribution was 1.5, the water content was 300 ppm, and the amino acid content was 40.5 mmol / kg. 【0078】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 245°C, the second zone 260°C, the third zone 270°C, the fourth zone 285°C, and the fifth zone 290°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 280°C, the pack pressure was 10 MPa, and the spinneret draw ratio was 200; 【0079】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 210°C and a annealing length of 25 mm; cooling was performed with rapid cooling air at an air velocity of 1.3 m / s, an air temperature of 24°C, and a humidity of 65%; the winding tension when winding the spun yarn into shape was 55 cN; the winding speed was 2,600 m / min; and the winding overfeed ratio was 2.5%. The drawing process was the same four-step drawing process as in Example 1, except that the total drawing ratio was 5.3, the temperature of the first stage heat set was 225°C, and the temperature of the second stage heat set was 235°C. 【0080】 Example 5: Polyamide 56 industrial yarn (233 dtex / 36 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and cuprous iodide was added as a heat stabilizer in an amount of 400 ppm based on the total weight of the raw materials to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.05:1; 【0081】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.0 MPa, degas it, maintain the pressure at 260°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.08 MPa at 295°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0082】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 155°C and the drying time is 25 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.45, while the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.6. The oligomer content was 1.0% by weight, the number-average molecular weight was 36,000, the molecular weight distribution was 1.7, the water content was 350 ppm, and the amino acid content was 46.5 mmol / kg. 【0083】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 255°C, the second zone 275°C, the third zone 280°C, the fourth zone 295°C, and the fifth zone 310°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 295°C, the pack pressure was 19 MPa, and the spinneret draw ratio was 250; 【0084】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 220°C and a annealing length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.0 m / s, an air temperature of 18°C, and a humidity of 70%; the winding tension when winding the spun yarn into shape was 23 cN; the winding speed was 2,900 m / min; and the winding overfeed ratio was 1.5%. The drawing process was the same four-step drawing process as in Example 1, except that the total drawing ratio was 5.5, the temperature of the first stage heat set was 230°C, and the temperature of the second stage heat set was 230°C. 【0085】 Example 6: Polyamide 56 industrial yarn (1,670 dtex / 192 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and a heat stabilizer was added to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 200 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 500 ppm based on the total weight of the raw materials. 【0086】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.3 MPa, degas the system, maintain the pressure at 255°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 270°C when the pressure reduction is complete, and evacuate to a vacuum of -0.01 MPa at 280°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0087】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 155°C and the drying time is 30 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.7, while the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.8. The oligomer content was 0.8% by weight, the number-average molecular weight was 38,000, the molecular weight distribution was 1.5, the water content was 500 ppm, and the amino acid content was 42.5 mmol / kg. 【0088】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 250°C, the second zone 275°C, the third zone 280°C, the fourth zone 295°C, and the fifth zone 305°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 290°C, the pack pressure was 14 MPa, and the spinneret draw ratio was 120; 【0089】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 230°C and a annealing length of 40 mm; cooling was performed with rapid cooling air at an air velocity of 1.1 m / s, an air temperature of 23°C, and a humidity of 75%; the winding tension when winding the spun yarn into shape was 160 cN; the winding speed was 3,200 m / min; and the winding overfeed ratio was 3.5%. The drawing process was the same four-step drawing process as in Example 1, except that the total drawing ratio was 5.6, the temperature of the first stage heat set was 225°C, and the temperature of the second stage heat set was 235°C. 【0090】 Example 7: Polyamide 56 industrial yarn (2,800 dtex / 480 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and a heat stabilizer was added to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.05:1; the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 250 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 2000 ppm based on the total weight of the raw materials. 【0091】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.2 MPa, degas it, maintain the pressure at 260°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 285°C when the pressure reduction is complete, and evacuate to a vacuum of -0.03 MPa at 290°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0092】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 155°C and the drying time is 30 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.35, while the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.2. The oligomer content was 0.8% by weight, the number-average molecular weight was 32,000, the molecular weight distribution was 1.5, the water content was 450 ppm, and the amino acid content was 38.5 mmol / kg. 【0093】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten mass; heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 258°C, the second zone 276°C, the third zone 288°C, the fourth zone 298°C, and the fifth zone 305°C; the polyamide 56 molten mass was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 293°C, the pack pressure was 12 MPa, and the spinneret draw ratio was 160; 【0094】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 230°C and a annealing length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 23°C, and a humidity of 70%; the winding tension when winding the spun yarn into shape was 280 cN; the winding speed was 2,700 m / min; and the winding overfeed ratio was 3%. 【0095】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 4.8, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0096】 Example 8: Polyamide 56 industrial yarn (233 dtex / 36 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and a heat stabilizer was added to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.05:1; the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 150 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 800 ppm based on the total weight of the raw materials. 【0097】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.2 MPa, degas it, maintain the pressure at 260°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 285°C when the pressure reduction is complete, and evacuate to a vacuum of -0.01 MPa at 290°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0098】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 155°C and the drying time is 30 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.4, and the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.4. The oligomer content was 0.8% by weight, the number-average molecular weight was 33,000, the molecular weight distribution was 1.6, the water content was 550 ppm, and the amino acid content was 33.5 mmol / kg. 【0099】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, specifically the first zone with a temperature of 268°C, the second zone with a temperature of 280°C, the third zone with a temperature of 290°C, the fourth zone with a temperature of 295°C, and the fifth zone with a temperature of 303°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 298°C, the pack pressure was 18 MPa, and the spinneret draw ratio was 120; 【0100】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a annealing temperature of 220°C and a annealing length of 30 mm; cooling was performed with rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 23°C, and a humidity of 70%; the winding tension when winding the spun yarn into shape was 140 cN; the winding speed was 3,000 m / min; and the winding overfeed ratio was 2%. 【0101】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 4.8, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0102】 Example 9: Polyamide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and copper chloride was added as a heat stabilizer in an amount of 300 ppm based on the total weight of the raw materials to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; 【0103】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.25 MPa, degas the system, maintain the pressure at 260°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.01 MPa at 280°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0104】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 160°C and the drying time is 22 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.4, and the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.4. The oligomer content was 0.8% by weight, the number-average molecular weight was 33,000, the molecular weight distribution was 1.6, the water content was 550 ppm, and the amino acid content was 33.5 mmol / kg. 【0105】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material; heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 268°C, the second zone 280°C, the third zone 290°C, the fourth zone 295°C, and the fifth zone 303°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 280°C, the pack pressure was 13 MPa, and the spinneret draw ratio was 150; 【0106】 (2) The spun yarn was insulated, cooled, spun, drawn, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a annealing temperature of 200°C and a annealing length of 40 mm; cooling was performed with rapid cooling air at an air velocity of 1.3 m / s, an air temperature of 20°C, and a humidity of 70%; the winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 2,700 m / min; and the winding overfeed ratio was 2.5%. 【0107】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 4.8, the temperature of the first stage heat set was 210°C, and the temperature of the second stage heat set was 220°C. 【0108】 Example 10: Polyamide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials, 1,5-pentanediamine, adipic acid, and water, were uniformly mixed under nitrogen conditions to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.15:1; 【0109】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.3 MPa, degas it, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.04 MPa at 285°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; The heat stabilizer masterbatch was injected online before the polymer melt was pelletized, the copper ion content in the heat stabilizer masterbatch was 2.0% by weight, the amount of heat stabilizer masterbatch added was 1.5% by weight, the heat stabilizer masterbatch base material was polyamide 56, and the method for producing the heat stabilizer masterbatch included the following steps: (a) the base material polyamide 56 was vacuum dried and then pulverized into a powder, resulting in 65 parts by mass of polyamide 56, with a relative viscosity of 2.9, a number-average molecular weight of 24 kg / mol, a molecular weight distribution of 2.1, and a water content of 500 ppm; (b) The powder obtained in step (a) is mixed with 12.5 parts by weight of heat stabilizer cuprous iodide, 0.5 parts by weight of lubricant wax OP, and 0.2 parts by weight of antioxidant 168, melted, and the mixture is extruded with a twin-screw to form pellets to obtain a heat stabilizer masterbatch. Here, the processing temperature of each zone was set as follows: the temperature of the first zone was 251°C, the temperature of the second zone was 264°C, the temperature of the third zone was 269°C, the temperature of the fourth zone was 273°C, the temperature of the fifth zone was 276°C, the screw rotation speed was 250 r / min, and the filtration screen was 150 mesh. 【0110】 (3) A high-viscosity polyamide 56 resin is prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness is 155°C and the drying time is 25 hours; The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.5, while the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.7. The oligomer content was 0.6% by weight, the number-average molecular weight was 34,000, the molecular weight distribution was 1.5, the water content was 300 ppm, and the amino acid content was 33.8 mmol / kg. 【0111】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, specifically the first zone with a temperature of 265°C, the second zone with a temperature of 278°C, the third zone with a temperature of 288°C, the fourth zone with a temperature of 295°C, and the fifth zone with a temperature of 300°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 295°C, the pack pressure was 14 MPa, and the spinneret draw ratio was 80; 【0112】 (2) The spun yarn was insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a temperature of 230°C and a length of 25 mm; cooling was performed with rapid cooling air at an air velocity of 1.1 m / s, an air temperature of 22°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 2,600 m / min; and the winding overfeed ratio was 2%. 【0113】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0114】 Example 11: Polyamide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials, 1,5-pentanediamine, adipic acid, and water, were uniformly mixed under nitrogen conditions to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.06:1; 【0115】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.2 MPa, degas it, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure at 0.1 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.06 MPa at 285°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0116】 (3) A high-viscosity polyamide 56 resin was prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness was 160°C and the drying time was 28 hours. The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.4, the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.3, the oligomer content was 0.9% by weight, the number-average molecular weight was 32,000, the molecular weight distribution was 1.6, the water content was 450 ppm, and the amino acid content was 36.5 mmol / kg. 【0117】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 255°C, the second zone 275°C, the third zone 280°C, the fourth zone 290°C, and the fifth zone 305°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 295°C, the pack pressure was 14 MPa, and the spinneret draw ratio was 140; The heat stabilizer masterbatch was blended during spinning using a masterbatch addition device. The copper ion content of the heat stabilizer masterbatch was 1.8% by weight, and the heat stabilizer masterbatch was added at 1.2% by weight. The method for producing the heat stabilizer masterbatch was the same as in Example 10. 【0118】 (2) The spun yarn was insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a temperature of 240°C and a length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.4 m / s, an air temperature of 22°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 3,500 m / min; and the winding overfeed ratio was 2%. 【0119】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0120】 Example 12: Polyamide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials, 1,5-pentanediamine, adipic acid, and water, were uniformly mixed under nitrogen conditions to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.08:1; 【0121】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.2 MPa, degas it, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0 MPa at 275°C when the pressure reduction is complete, and evacuate to a vacuum of -0.05 MPa at 290°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; 【0122】 (3) A high-viscosity polyamide 56 resin was prepared by imparting solid-phase tackiness to a low-viscosity polyamide 56 resin; the temperature for imparting solid-phase tackiness was 160°C and the drying time was 28 hours. The relative viscosity of the low-viscosity polyamide 56 resin in 96% sulfuric acid was 2.4, the relative viscosity of the high-viscosity polyamide 56 resin in 96% sulfuric acid was 3.2, the oligomer content was 0.8% by weight, the number-average molecular weight was 30,000, the molecular weight distribution was 1.6, the water content was 400 ppm, and the amino acid content was 32.3 mmol / kg. 【0123】 2. Spinning: (1) High-viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 250°C, the second zone 270°C, the third zone 285°C, the fourth zone 290°C, and the fifth zone 290°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 285°C, the pack pressure was 12 MPa, and the spinneret draw ratio was 180; The heat stabilizer masterbatch was blended during spinning using a masterbatch addition device, with a copper ion content of 1.6% by weight, and the heat stabilizer masterbatch was added at a concentration of 1.5% by weight. The heat stabilizer masterbatch base material was polyamide 6, and the method for producing the heat stabilizer masterbatch included the following steps: (a) The base material polyamide 6 was vacuum dried and then pulverized into a powder, resulting in 65 parts by mass of polyamide 6, with a relative viscosity of 2.9, a number-average molecular weight of 24 kg / mol, a molecular weight distribution of 2.1, and a water content of 500 ppm; (b) The powder obtained in step (a) is mixed with 15 parts by weight of heat stabilizer cuprous iodide, 0.5 parts by weight of lubricant wax OP, and 0.2 parts by weight of antioxidant 168, melted, and the mixture is extruded with a twin-screw to form pellets to obtain a heat stabilizer masterbatch. Here, the processing temperature of each zone was set as follows: the temperature of the first zone was 200°C, the temperature of the second zone was 210°C, the temperature of the third zone was 220°C, the temperature of the fourth zone was 230°C, the temperature of the fifth zone was 235°C, the screw rotation speed was 250 r / min, and the filtration screen was 150 mesh. 【0124】 (2) The spun yarn was insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a temperature of 225°C and a length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 22°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 3,300 m / min; and the winding overfeed ratio was 2%. 【0125】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0126】 Example 13: Polyamide 56 industrial yarn (933 dtex / 140 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and cuprous iodide was added as a heat stabilizer in an amount of 200 ppm based on the total weight of the raw materials to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; 【0127】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.25 MPa, degas it, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure in the reaction system to 0.1 MPa at 280°C when the pressure reduction is complete, and evacuate to a vacuum of -0.01 MPa at 295°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; The high-viscosity polyamide 56 resin in 96% sulfuric acid had a relative viscosity of 3.4, an oligomer content of 0.8% by weight, a number-average molecular weight of 30,000, a molecular weight distribution of 1.6, a water content of 400 ppm, and an amino acid content of 32.5 mmol / kg. 【0128】 2. Spinning: (1) A high-viscosity polyamide 56 molten material is transported to the spinning beam by a molten booster pump and spun directly; the polyamide 56 molten material is ejected through the spinneret plate of the spinning beam to form the spun yarn; the spinning beam temperature was 280°C, the pack pressure was 18 MPa, and the spinneret draw ratio was 200; 【0129】 (2) The spun yarn was insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a temperature of 220°C and a length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 22°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 2,500 m / min; and the winding overfeed ratio was 2%. 【0130】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0131】 Example 14: Polyamide 56 industrial yarn (2,800 dtex / 480 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and a heat stabilizer was added to obtain a 65% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.08:1; the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 200 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 700 ppm based on the total weight of the raw materials. 【0132】 (2) Heat the aqueous solution of polyamide 56 salt, raise the pressure of the reaction system to 2.4 MPa, degas, maintain the pressure at 265°C when the pressure maintenance is complete, reduce the pressure at 0.1 MPa at 285°C when the pressure reduction is complete, and evacuate to a vacuum of -0.06 MPa at 290°C when the exhaust is complete to obtain a high-viscosity polyamide 56 molten product; all pressures here are gauge pressures; The high-viscosity polyamide 56 resin in 96% sulfuric acid had a relative viscosity of 3.5, an oligomer content of 1.0% by weight, a number-average molecular weight of 34,000, a molecular weight distribution of 1.6, a water content of 450 ppm, and an amino acid content of 40.5 mmol / kg. 【0133】 2. Spinning: (1) A high-viscosity polyamide 56 molten material is transported to the spinning beam by a molten booster pump and spun directly; the polyamide 56 molten material is ejected through the spinneret plate of the spinning beam to form the spun yarn; the spinning beam temperature was 290°C, the pack pressure was 12 MPa, and the spinneret draw ratio was 180; 【0134】 (2) The spun yarn was insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing apparatus at a temperature of 210°C and a length of 20 mm; cooling was performed with rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 23°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 280 cN; the winding speed was 2,900 m / min; and the winding overfeed ratio was 3%. 【0135】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 4.5, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0136】 Example 15: Polyimide 56 industrial yarn (1,670 dtex / 192 f) The manufacturing method was the same as in Example 6, except that the heat stabilizer was a composite of copper acetate and potassium iodide, with copper acetate added at a concentration of 200 ppm relative to the total weight of the raw materials, and potassium iodide added at a concentration of 1000 ppm relative to the total weight of the raw materials. 【0137】 Example 16: Polyamide 56 industrial yarn (1,670 dtex / 192 f) The manufacturing method was the same as in Example 6, except that the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added at a concentration of 200 ppm based on the total weight of the raw materials, and potassium iodide added at a concentration of 2000 ppm based on the total weight of the raw materials. 【0138】 Example 17: Polyamide 56 industrial yarn (1,670 dtex / 192 f) The manufacturing method was the same as in Example 6, except that the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added at a concentration of 200 ppm based on the total weight of the raw materials, and potassium iodide added at a concentration of 1800 ppm based on the total weight of the raw materials. 【0139】 Example 18: Polyamide 56 industrial yarn (1,670 dtex / 192 f) The manufacturing method was the same as in Example 6, except that the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 200 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 2500 ppm based on the total weight of the raw materials. 【0140】 Comparative Example 1: Polyimide 56 Industrial Yarn (933 dtex / 140 f) The manufacturing method was the same as in Example 1, except that the heat stabilizer copper acetate was not added during the polymerization of 1,5-pentanediamine and adipic acid in step (1). 【0141】 Comparative Example 2: Polyimide 56 Industrial Yarn (933 dtex / 140 f) The manufacturing method was the same as in Example 1, except that the water content of the obtained high-viscosity polyamide 56 resin was 1200 ppm during polymerization in step 1. 【0142】 Comparative Example 3: Polyamide 56 Industrial Yarn (1,670 dtex / 192 f) The process included the following steps: 1. Polymerization: (1) The raw materials 1,5-pentanediamine, adipic acid, and water were uniformly mixed under nitrogen conditions, and a heat stabilizer was added to obtain a 60% concentration polyamide 56 salt solution; the molar ratio of 1,5-pentanediamine to adipic acid was 1.1:1; the heat stabilizer was a compound of copper acetate and potassium iodide, with copper acetate added in an amount of 200 ppm based on the total weight of the raw materials, and potassium iodide added in an amount of 500 ppm based on the total weight of the raw materials; 【0143】 (2) Heat the polyamide 56 salt aqueous solution to raise the pressure in the reaction system to 2.3 MPa, degas the system, maintain the pressure at 255°C when the pressure maintenance is complete, reduce the pressure to 0.1 MPa at 270°C when the pressure reduction is complete, and evacuate to a vacuum of -0.05 MPa at 280°C when the exhaust is complete to obtain low viscosity polyamide 56 resin; all pressures here are gauge pressures; In 96% sulfuric acid, the low viscosity polyamide 56 resin had a relative viscosity of 2.5, an oligomer content of 0.8% by weight, a number-average molecular weight of 16,000, a molecular weight distribution of 1.5, a water content of 500 ppm, and an amino acid content of 42.5 mmol / kg. 【0144】 2. Spinning: (1) Low viscosity polyamide 56 resin was heated to a molten state to form a polyamide 56 molten material. Heating was performed using a screw extruder; the screw extruder was divided into five heating zones, with the temperature of the first zone being 250°C, the second zone 275°C, the third zone 280°C, the fourth zone 295°C, and the fifth zone 305°C; the polyamide 56 molten material was ejected through the spinneret plate of a spinning beam to form a spun yarn; the spinning beam temperature was 290°C, the pack pressure was 14 MPa, and the spinneret draw ratio was 120; 【0145】 (2) The spun yarn is insulated, cooled, spun, stretched, and wound into shape to obtain polyamide 56 industrial yarn. Insulation was performed using an annealing device with an annealing temperature of 230°C and an annealing length of 40 mm; cooling was performed with rapid cooling air, with an air velocity of 1.1 m / s, an air temperature of 23°C, and a humidity of 75%; the winding tension when winding the spun yarn into shape was 160 cN; the winding speed was 3,200 m / min; and the winding overfeed ratio was 3.5%; the drawing process was the same four-stage drawing process as in Example 1, except that the total drawing ratio was 5.6, the temperature of the first stage heat set was 225°C, and the temperature of the second stage heat set was 235°C. 【0146】 Comparative Example 4: Polyamide 6 Industrial Yarn (933 dtex / 140 f) The process included the following steps: 1. High-viscosity polyamide 6 resin was heated to a molten state to form a polyamide 6 molten material. Heating was carried out using a screw extruder; the screw extruder was specifically divided into five heating zones, with the temperature of the first zone at 255°C, the second zone at 270°C, the third zone at 280°C, the fourth zone at 290°C, and the fifth zone at 300°C. The high-viscosity polyamide 6 resin in 96% sulfuric acid had a relative viscosity of 3.3, an oligomer content of 0.8% by weight, a number-average molecular weight of 30,000, a molecular weight distribution of 1.6, a water content of 400 ppm, and an amino acid content of 36.5 mmol / kg. 【0147】 2. Molten polyamide 6 is ejected through the spinneret plate of the spinning beam to form a filament, and the molten polyamide 6 is spun into yarn; the spinning beam temperature was 290°C, the pack pressure was 15 MPa, and the spinneret draw ratio was 150; 【0148】 3. The spun yarn was processed to obtain polyamide 6 industrial yarn. This processing included the steps of insulating, cooling, spinning, drawing, and winding the spun yarn into shape to obtain polyamide 56 industrial yarn; insulation was performed using an annealing device at a temperature of 220°C and a length of 20 mm; cooling was performed using rapid cooling air at an air velocity of 1.2 m / s, an air temperature of 22°C, and a humidity of 70%; The winding tension when winding the spun yarn into shape was 90 cN; the winding speed was 3,500 m / min; and the winding overfeed ratio was 2.0%. 【0149】 The stretching process was the same four-stage stretching process as in Example 1, except that the total stretching ratio was 5.0, the temperature of the first stage heat set was 220°C, and the temperature of the second stage heat set was 230°C. 【0150】 Table 1 below shows the absolute difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin, the absolute difference between the amino content of the de-oiled yarn and the amino content of the raw material resin, filament breakage (times / 24 hours), and manufacturing yield (%) in the above examples and comparative examples. Table 2 below shows the properties of the obtained polyamide 56 industrial yarn. 【0151】 [Table 1] 【0152】 In this invention, the uniformity and stability of the polyamide 56 molten material were improved by reducing the range of variation in viscosity and amino content of the de-oiled yarn, thereby reducing filament breakage and improving spinnability. The resulting polyamide 56 industrial yarn achieved a high yield of over 95%, and filament breakage occurred less than once every 24 hours. 【0153】 [Table 2] 【0154】 This invention optimizes the viscosity, oligomer content, molecular weight and its distribution, and water content of polyamide 56 resin. Furthermore, this invention optimizes the spinning process of polyamide 56 industrial yarn, improving its crystallinity and degree of orientation, increasing the set temperature and winding overfeed ratio, and reducing subsequent stress relaxation. Thus, this invention provides polyamide 56 industrial yarn with excellent mechanical properties and dimensional stability, including a breaking strength of 8.0 cN / dtex or higher, an elongation at break of 26% or less, a dry heat shrinkage rate and boiling water shrinkage rate of 6% or less, a crystallinity of 70% or higher, and an orientation of 80% or higher. 【0155】 The above description of embodiments is provided to facilitate understanding and application of the present invention for those skilled in the art. It will be apparent to those skilled in the art that various modifications to these embodiments are readily apparent. The general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements and modifications made by those skilled in the art in accordance with the disclosure of the present invention, without departing from the scope of the present invention, should all fall within the scope of protection of the present invention.

Claims

[Claim 1] Polyamide 56 industrial yarn, The polyamide 56 industrial yarn is characterized in that the raw materials for producing the polyamide 56 industrial yarn include at least a high viscosity polyamide 56 resin, the high viscosity polyamide 56 resin having a relative viscosity of 2.7 to 4.5 in 96% sulfuric acid, an oligomer content of 0.2 to 1.0% by weight, a number average molecular weight of 18,000 to 40,000, a molecular weight distribution of 0.8 to 1.8, a water content of 200 to 800 ppm, and an amino acid content of 20 to 50 mmol / kg, the polyamide 56 industrial yarn includes a heat stabilizer, the heat stabilizer includes one of copper acetate, potassium iodide, copper chloride, cuprous iodide, copper oxide, cuprous oxide, or a combination thereof, and the heat stabilizer is added in an amount of 10 to 2800 ppm based on the total weight of the raw materials for production. [Claim 2] The polyamide 56 industrial yarn according to claim 1, characterized in that the heat stabilizer is added in an amount of 100 to 2500 ppm relative to the total weight of the raw materials for production. [Claim 3] The polyamide 56 industrial yarn according to claim 1, characterized in that the heat stabilizer comprises a composition of potassium iodide and copper acetate, and the molar ratio of copper acetate to potassium iodide is 1:1 to 15. [Claim 4] The high-viscosity polyamide 56 resin has a relative viscosity of 3.2 to 4.0 in 96% sulfuric acid; and / or The high-viscosity polyamide 56 resin has an oligomer content of 0.4 to 0.6% by weight; and / or The high-viscosity polyamide 56 resin has a number-average molecular weight of 25,000 to 30,000 and a molecular weight distribution of 1.2 to 1.5; and / or The high-viscosity polyamide 56 resin has a water content of 300 to 750 ppm; and / or The polyamide 56 industrial yarn according to claim 1, characterized in that the high viscosity polyamide 56 resin has an amino acid content of 24 to 45 mmol / kg. [Claim 5] The polyamide 56 industrial yarn according to claim 1, characterized in that the copper ion content in the polyamide 56 resin is 10 to 1000 ppm. [Claim 6] The polyamide 56 industrial yarn according to any one of claims 1 to 5, characterized in that the polyamide 56 industrial yarn has a heat resistance to breaking strength retention rate of 90% or more after being treated at 180°C for 4 hours, and / or has a heat resistance to breaking strength retention rate of 90% or more after being treated at 230°C for 30 minutes, and / or the polyamide 56 industrial yarn has a dry heat shrinkage rate of 8.0% or less. [Claim 7] The polyamide 56 industrial yarn according to any one of claims 1 to 5, characterized in that the polyamide 56 industrial yarn has a heat resistance tensile strength retention rate of 93% or more after being treated at 180°C for 4 hours, and / or a heat resistance tensile strength retention rate of 92% or more after being treated at 230°C for 30 minutes, and / or the polyamide 56 industrial yarn has a dry heat shrinkage rate of 6.0% or less. [Claim 8] The aforementioned polyamide 56 industrial yarn has a breaking strength of 6.5 cN / dtex or more. The polyamide 56 industrial yarn has a boiling water shrinkage rate of 8.0% or less; and / or The polyamide 56 industrial yarn has a fineness of 100 to 3500 dtex; and / or The polyamide 56 industrial yarn has an elongation at break of 26% or less; and / or The polyamide 56 industrial yarn has a crystallinity of 70% or more; and / or The polyamide 56 industrial yarn according to any one of claims 1 to 5, characterized in that the polyamide 56 industrial yarn has an orientation degree of 80% or more. [Claim 9] A method for producing polyamide 56 industrial yarn according to any one of claims 1 to 8, wherein the method comprises the following steps: (1) A high-viscosity polyamide 56 molten material is obtained by polymerizing 1,5-pentanediamine and adipic acid, the molten material is transported to a spinning beam by a molten booster pump, and either spun directly or using tip spinning is used to first prepare a low-viscosity polyamide 56 resin by polymerization of 1,5-pentanediamine and adipic acid, then a high-viscosity polyamide 56 resin is obtained by solid-phase tackification, and the high-viscosity polyamide 56 resin is heated to a molten state to form a polyamide 56 molten material for spinning; (2) stretching the molten polyamide 56 obtained in step (1) to form a spinning yarn; and (3) Processing the spun yarn to obtain polyamide 56 industrial yarn; Here, In step (1), the heat stabilizer is added during the polymerization of 1,5-pentanediamine and adipic acid, or injected online in the form of a heat stabilizer masterbatch before cutting the polymer melt into pellets, or blended in the form of a heat stabilizer masterbatch during spinning; The copper ion content in the heat stabilizer masterbatch is 0.5 to 10% by weight; The aforementioned heat stabilizer masterbatch is added in an amount of 0.3 to 5.0% by weight; The substrate for the heat stabilizer masterbatch comprises any one of polyamide 6, polyamide 56, polyamide 66, polyamide 510, polyamide 610, polybutylene terephthalate, or a combination thereof; and / or The method further includes the step of adding other additives, which include one of the following: a matting agent, a flame retardant, an antioxidant, an ultraviolet absorber, an infrared absorber, a crystal nucleating agent, a fluorescent whitening agent, and an antistatic agent, or a combination thereof. [Claim 10] The method according to claim 9, characterized in that step (1) polymerization of 1,5-pentanediamine and adipic acid specifically includes the following steps: (1-1) Under inert gas or vacuum conditions, 1,5-pentanediamine, adipic acid, and water are homogeneously mixed to obtain a polyamide 56 salt solution; where the molar ratio of 1,5-pentanediamine to adipic acid is (0.95-1.2):1; (1-2) The polyamide 56 salt solution is heated to increase the pressure in the reaction system to 0.3 to 2.5 MPa, degassed, and maintain the pressure. Then, the pressure in the reaction system is reduced to 0 to 0.2 MPa, and the system is evacuated to a vacuum of -(0.01 to 0.1) MPa (gauge pressure) to obtain a molten polyamide 56. [Claim 11] In process (1), The low-viscosity polyamide 56 resin in 96% sulfuric acid has a relative viscosity of 2.0 to 2.7, and / or The heating in step (1) is carried out in a screw extruder, which includes five heating zones; The method according to claim 10, characterized in that the temperature of the first zone is 250 to 290°C, the temperature of the second zone is 260 to 300°C, the temperature of the third zone is 270 to 320°C, the temperature of the fourth zone is 280 to 330°C, and the temperature of the fifth zone is 280 to 320°C. [Claim 12] The method according to claim 9, characterized in that step (2) specifically includes the following steps: Forming a spun yarn by ejecting molten polyamide 56 through the spinneret plate of a spinning beam; and / or, The temperature of the spinning beam is 270 to 330°C, and / or The spinning pack pressure of the spinning beam is 8 to 25 MPa and / or The draw ratio of the spindle of the aforementioned spindle plate is 50 to 400. [Claim 13] The method according to claim 9, characterized in that step (3) specifically includes the following steps: Insulating, cooling, spinning, stretching, and winding the spun yarn coming out of the spinneret orifice to obtain polyamide 56 industrial yarn; and / or The aforementioned insulation is carried out by a slow cooling device, where the slow cooling temperature is 150 to 280°C; the slow cooling length is 10 to 80 mm; the cooling is carried out with rapid cooling air, where the air velocity of the rapid cooling air is 0.3 to 2.0 m / s; the air temperature of the rapid cooling air is 15 to 25°C; and / or the humidity of the rapid cooling air is 60 to 80%; and / or, The winding tension when winding the aforementioned spun yarn into shape is 50 to 300 cN; or The winding speed is 2,000 to 3,800 m / min; and / or the winding overfeed ratio is 5% or less. [Claim 14] The stretching is carried out in four or more stages. The stretching process includes, firstly, supplying the spun yarn to a first pair of hot rollers via a godet roller and performing a first stage of stretching between the first pair of hot rollers and a second pair of hot rollers; performing a second stage of stretching between the second pair of hot rollers and a third pair of hot rollers; performing a third stage of stretching and a first stage of heat setting between the third pair of hot rollers and a fourth pair of hot rollers; and performing a fourth stage of stretching and a second stage of heat setting between the fourth pair of hot rollers and a fifth pair of hot rollers; The temperature of the first heat set is 180-250°C; and / or The method according to claim 13, characterized in that the temperature of the second heat set is 200 to 240°C. [Claim 15] The method according to claim 9, characterized in that the de-oiled yarn of the polyamide 56 industrial yarn has a relative viscosity of 2.7 to 4.5, and the absolute value of the difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin is 0.12 or less. [Claim 16] The method according to claim 15, characterized in that the absolute value of the difference between the relative viscosity of the de-oiled yarn and the relative viscosity of the raw material resin is 0.10 or less. [Claim 17] The method according to claim 9, characterized in that the de-oiled polyamide 56 industrial yarn has an amino acid content of 20 to 50 mmol / kg, and the absolute difference between the amino acid content of the de-oiled yarn and the amino acid content of the raw material resin is 5 or less. [Claim 18] The method according to claim 17, characterized in that the absolute difference between the amino content of the de-oiled yarn and the amino content of the raw material resin is 3 or less. [Claim 19] The method according to claim 9, characterized in that the filaments of the polyamide 56 industrial yarn break no more than twice every 24 hours, and the manufacturing yield of the polyamide 56 industrial yarn is 90% or more. [Claim 20] Use of polyamide 56 industrial yarn according to any one of claims 1 to 8 in the fields of sewing thread, tire cord, airbag thread, release cloth, water cloth, canvas, safety belt, rope, fishing net, industrial filter cloth, conveyor belt, parachute, tent, bag and suitcase.

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