A melt direct spinning polyamide 56 staple fiber and its preparation method

Abstract

The present invention relates to the technical field of polyamide materials, and discloses a melt direct spinning polyamide 56 staple fiber and a preparation method thereof. By optimizing the polymerization formula and the melt direct spinning process, a large-capacity and high-performance bio-based polyamide 56 staple fiber is prepared, with stable production, few floating single filaments and nozzle filaments, high fiber forming rate, good cotton-like feel, few defect contents, good mechanical properties, large elongation rate, good crimping effect and fluffiness, and good hand feeling, which can meet the blending requirements with cotton, linen, silk, wool and other chemical fibers.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyamide materials, and particularly relates to a melt direct spinning polyamide 56 staple fiber and a preparation method thereof. Background Art

[0002] Melt spinning is one of the main forming methods of synthetic fibers, abbreviated as melt spinning. Melt spinning is divided into direct spinning method and chip spinning method. Direct spinning is to directly send the polymer melt after polymerization to spinning; chip spinning requires the polymer melt to go through pre-spinning preparation processes such as casting strip, pelletizing, and drying before being sent to spinning.

[0003] The monomer content in the polymer of polyamide 6 is relatively high (about 10 wt%), and the chips need to be extracted before melt spinning can be achieved. Currently, industrialized melt direct spinning cannot be realized. In the spinning process of polyamide 66, problems such as easy generation of gels and difficult dyeing are prone to occur, and there are great difficulties in the melt direct spinning technology of civil yarns. Although melt direct spinning has been partially realized in the field of industrial yarns, the melt conveying pipeline and the spinning box need to be disassembled, calcined, and cleaned regularly, increasing the spinning cost.

[0004] CN105669969 B discloses a nylon 6 polymerization method and its melt direct spinning method. By first preparing a polyamide 6 prepolymer at a low temperature, controlling the content of oligomers in the melt in advance, and then through a method of strengthening the polycondensation reaction kinetics, polymerization is completed before a large amount of cyclic oligomers are generated, obtaining a nylon 6 polymer melt with a certain molecular weight. In the obtained product, the content of extractables ≤ 1.5 wt%, and the content of cyclic dimers ≤ 0.2 wt%; then, after the polycondensation reaction kinetics strengthening ends, direct melt spinning is carried out for forming, but there is still no technical breakthrough and industrialization case.

[0005] CN103668510 A discloses a device and a method for producing fine denier or superfine denier nylon 66 filaments. The device includes an evaporator, a preheater, a reactor, a flash evaporator, and a post-condensation system. The nylon 66 brine solution is obtained through a polycondensation reaction to obtain a nylon 66 melt, and then the nylon 66 melt is directly spun to prepare fine denier or superfine denier nylon 66 POY filaments. The spinning speed is 4200 - 4300 m / min, the spinning speed is low, the output is low, and the fiber strength is low.

[0006] Bio-based polyamide 56 uses bio-based pentamethylenediamine as the monomer raw material. The carbon emissions per unit weight of bio-based polyamide 56 are reduced by more than 50% compared to the carbon emissions of the same weight of nylon 66 and nylon 6. The application and promotion of bio-based polyamide 56 will play a positive role in improving China's dependence on imported key materials and are of great significance for solving the sustainable development of fossil resource dependence and low-carbon emission reduction. Bio-based polyamide 56 materials have excellent mechanical properties, fast moisture absorption and drying properties, skin-friendly properties, wear resistance, good softness, and low-temperature dyeing characteristics, etc. Currently, they have broad application prospects in the fields of civil filament, staple fiber, industrial yarn, continuous bulk filament, monofilament, etc. However, there is currently no relevant research and report on the industrial production of large-capacity bio-based polyamide 56 staple fibers by melt direct spinning. Summary of the Invention

[0007] In order to meet the requirements of the industrial production of bio-based polyamide 56 by melt direct spinning, the present invention optimized the melt polymerization formula, process, and melt direct spinning process of polyamide 56, and prepared large-capacity and high-performance bio-based polyamide 56 staple fibers with stable production, few floating single filaments and nozzle filaments, and high fiber forming rate.

[0008] The first object of the present invention is to provide a melt direct spinning polyamide 56 staple fiber, the fineness of the polyamide 56 staple fiber is ≤100 D, further ≤80 D, further ≤60 D, and even further ≤30 D; and / or

[0009] The breaking strength of the polyamide 56 staple fiber is 3.0 - 8.0 cN / dtex, further 3.5 - 7.0 cN / dtex, further 3.8 - 6.0 cN / dtex, and even further 4.0 - 5.5 cN / dtex; and / or

[0010] The breaking elongation of the polyamide 56 staple fiber is 40 - 110%, further 45 - 100%, further 50 - 90%, and even further 60 - 85%; and / or

[0011] The dry heat shrinkage rate of the polyamide 56 staple fiber is 3.0 - 9.0%, further 4.0 - 8.5%, further 5.0 - 8.0%, and even further 6.0 - 7.0%; and / or

[0012] The specific resistance of the polyamide 56 staple fiber is ≤5.0×10 7 Ω·cm, further ≤4.5×10 7 Ω·cm, further ≤4.0×10 7 Ω·cm, and even further ≤3.0×10 7 Ω·cm.

[0013] In some specific embodiments, the length of the polyamide 56 staple fiber is ≤180 mm, preferably ≤150 mm, more preferably ≤120 mm, and even more preferably ≤80 mm.

[0014] In some specific embodiments, the defect content of the polyamide 56 staple fiber is ≤15 mg / 100 g, preferably ≤10 mg / 100 g, more preferably ≤8 mg / 100 g, and even more preferably ≤6 mg / 100 g.

[0015] In some specific embodiments, the crimp number of the polyamide 56 staple fiber is 8 - 25 per 25 mm, preferably 9 - 20 per 25 mm, more preferably 10 - 18 per 25 mm, and even more preferably 11 - 16 per 25 mm.

[0016] In some specific embodiments, the number of single floating filaments of the polyamide 56 staple fiber is ≤3 per 1 assembly * h, preferably ≤2 per 1 assembly * h, more preferably ≤1 per 1 assembly * h, and even more preferably ≤0 per 1 assembly * h.

[0017] In some specific embodiments, the number of nozzle head filaments of the polyamide 56 staple fiber is ≤4 per 1 assembly * h, preferably ≤3 per 1 assembly * h, more preferably ≤2 per 1 assembly * h, and even more preferably ≤1 per 1 assembly * h.

[0018] In some specific embodiments, the production rate of the polyamide 56 staple fiber is ≥95%, preferably ≥96%, more preferably ≥97%, and even more preferably ≥98%.

[0019] The second object of the present invention is to provide a method for preparing melt direct spinning polyamide 56 staple fiber, and the preparation method at least includes the following steps:

[0020] (1) The polyamide 56 melt is sent through a melt booster pump and a melt conveying pipeline to a spinning box for wire drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments;

[0021] (2) The polyamide 56 raw filaments are bundled, drawn, tension heat set, crimped, relaxation heat set, cut, and packed to obtain the polyamide 56 staple fiber;

[0022] When the polyamide 56 melt is a highly lustrous melt, its titanium dioxide content is 0; when the polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.2 - 0.4 wt%, preferably 0.25 - 0.35 wt%; when the polyamide 56 melt is a full dull melt, its titanium dioxide content is 1.2 - 2.0 wt%, preferably 1.4 - 1.8 wt%.

[0023] In some specific embodiments, from the melt booster pump to the spinning box, the dynamic viscosity of the polyamide 56 melt is controlled to be ≥180 Pa·s, preferably ≥200 Pa·s, more preferably ≥220 Pa·s, and even more preferably ≥230 Pa·s.

[0024] In some specific embodiments, the temperature of the melt delivery pipe is controlled to be 260 - 295 °C, preferably 263 - 293 °C, more preferably 265 - 290 °C, and even more preferably 270 - 288 °C.

[0025] In some specific embodiments, the length of the melt pipe for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 10 - 50 m, preferably 12 - 45 m, more preferably 14 - 40 m, and even more preferably 16 - 35 m.

[0026] In some specific embodiments, the residence time of the melt from the melt booster pump to the spinning box is 8 - 45 min, preferably 11 - 40 min, more preferably 13 - 35 min, and even more preferably 15 - 30 min.

[0027] In some specific embodiments, the melt pressure drop from the melt booster pump to the inlet of the spinning box is ≤10 MPa, preferably ≤8 MPa, more preferably ≤7 MPa, and even more preferably ≤6 MPa.

[0028] In some specific embodiments, the melt pressure at the inlet of the spinning box is ≥5.0 MPa, preferably ≥6.0 MPa, more preferably ≥6.5 MPa, and even more preferably ≥7.0 MPa.

[0029] In some specific embodiments, the relative viscosity of the polyamide 56 melt is 2.4 - 3.4, preferably 2.45 - 3.3, more preferably 2.5 - 3.2, and even more preferably 2.55 - 3.0.

[0030] In some specific embodiments, the oligomer content of the polyamide 56 melt is ≤1.1 wt%, preferably ≤1.0 wt%, more preferably ≤0.9 wt%, and even more preferably ≤0.8 wt%.

[0031] In some specific embodiments, the amino group content of the polyamide 56 melt is 30 - 100 mmol / kg, preferably 35 - 85 mmol / kg, more preferably 40 - 70 mmol / kg, and further preferably 43 - 60 mmol / kg.

[0032] In the present invention, the method for preparing the polyamide 56 melt includes the following steps: preparing a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtaining the polyamide 56 melt through prepolymerization, flash evaporation, and polycondensation.

[0033] In some specific embodiments, the molar ratio of pentamethylenediamine to adipic acid is (1 - 1.08):1.

[0034] In some specific embodiments, the concentration of the polyamide 56 salt solution is 35 - 80 wt%, preferably 40 - 70 wt%, more preferably 45 - 65 wt%, and still more preferably 48 - 60 wt%. The pH value of the polyamide 56 salt solution is 6.0 - 9.5, preferably 6.5 - 9.0, more preferably 7.0 - 8.8, and still more preferably 7.3 - 8.5.

[0035] In some specific embodiments, the pressure of the prepolymerization is 0.3 - 2.5 MPa, preferably 0.5 - 2.2 MPa, more preferably 0.8 - 2.0 MPa, and still more preferably 1.2 - 1.8 MPa; the temperature of the prepolymerization is 150 - 270 °C, preferably 180 - 265 °C, more preferably 200 - 260 °C, and still more preferably 225 - 255 °C.

[0036] The pressure of the polycondensation is -(0 - 0.08) MPa, preferably -(0.01 - 0.07) MPa, more preferably -(0.02 - 0.06) MPa, and still more preferably -(0.03 - 0.05) MPa; the temperature of the polycondensation is 250 - 295 °C, preferably 260 - 290 °C, more preferably 265 - 285 °C, and still more preferably 270 - 283 °C.

[0037] In one embodiment, a titanium dioxide matting agent can be added during the flash evaporation process. The dispersion particle size of the titanium dioxide in the polyamide 56 melt is 0.2 - 0.8 μm. As a preference, the particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2 - 0.5 μm is more than 95%; more preferably, the particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2 - 0.3 μm is more than 90%. Before adding the titanium dioxide matting agent, the present invention also includes performing a pre-treatment of powder grinding on the titanium dioxide matting agent, and mainly obtaining different titanium dioxide powders by controlling process conditions such as grinding time, polymerization, and spinning, so as to achieve different dispersion particle size distribution ratios.

[0038] In one embodiment, an antioxidant is added during the polymerization process. The addition amount of the antioxidant is 10 - 500 ppm, preferably 15 - 400 ppm, more preferably 20 - 300 ppm, and further preferably 25 - 200 ppm. The antioxidant is selected from any one or a combination of several of sodium hypophosphite, sodium acetate hypophosphite, calcium hypophosphite, phosphorous acid, antioxidant 1010, and antioxidant 1097.

[0039] In some specific embodiments, a saturated superheated steam device and a monomer suction device are arranged below the spinning box. The inventors of the present invention have found that by arranging the saturated superheated steam device and the monomer suction device, the saturated superheated steam can be sprayed in from the periphery around the lower part of the spinneret plate, and the polyamide oligomers overflowing from the spinneret holes and the fiber surface are dissolved in the saturated superheated steam and then taken away by the monomer suction device, keeping the spinneret plate and its lower part clean, prolonging the shoveling period of the spinning component, reducing the phenomena of head filaments and single filament breaks caused by oligomers during the spinning process, and effectively improving the spinning production stability and the forming rate.

[0040] In some specific embodiments, the temperature of the saturated superheated steam is 95 - 260 °C, preferably 100 - 250 °C, more preferably 110 - 240 °C, and further preferably 120 - 230 °C.

[0041] In some specific embodiments, the pressure of the saturated superheated steam is 0.4 - 3.5 bar, preferably 0.6 - 3.0 bar, more preferably 0.8 - 2.5 bar, and further preferably 1.0 - 2.0 bar.

[0042] In some specific embodiments, the pressure of the monomer suction device is ≥ 6.0 bar, preferably ≥ 6.5 bar, more preferably ≥ 7.0 bar, and further preferably ≥ 7.5 bar.

[0043] In some specific embodiments, the wire drawing in step (1) is to eject the polyamide 56 melt through the spinneret plate of the spinning box. The spinneret plate is a rectangular spinneret plate or a circular spinneret plate, preferably a circular spinneret plate. The number of holes of the spinneret plate is 300 - 3500 f, preferably 400 - 3000 f, more preferably 500 - 2500 f, and even more preferably 600 - 2000 f.

[0044] In some specific embodiments, the pressure of the spinning component in the spinning box is ≥ 6 MPa, preferably ≥ 7 MPa, more preferably ≥ 8 MPa, and even more preferably ≥ 9 MPa. The spinning component is a rectangular spinning component or a circular spinning component, preferably a circular spinning component.

[0045] In some specific embodiments, the cooling is carried out by side blowing or ring blowing, preferably ring blowing. The temperature of the cooling air is 16 - 25°C, preferably 17 - 24°C, more preferably 18 - 23°C, and even more preferably 19 - 22°C; the humidity is 60 - 95%, preferably 65 - 90%, more preferably 70 - 85%, and even more preferably 75 - 80%.

[0046] In some specific embodiments, the winding speed is 300 - 1500 m / min, preferably 500 - 1400 m / min, more preferably 600 - 1300 m / min, and even more preferably 700 - 1200 m / min.

[0047] In the present invention, in step (2), the drawing is a two-stage drawing. The first-stage drawing is carried out between the first drawing machine and the second drawing machine, and the second-stage drawing is carried out in the steam heating box between the second drawing machine and the tension heat setting machine. After passing through the second drawing zone, the filament obtains all the orientation of its molecular structure. The drawn filament sheet enters the roller heat setting machine, and after drying and baking, it is heated under a certain tension for relaxation heat setting to eliminate the residual stress generated by drawing of the filament sheet, so as to improve the strength of the fiber and reduce its elongation.

[0048] In some specific embodiments, the temperature of the first-stage drawing is 50 - 100°C, preferably 60 - 80°C; the draw ratio is 80 - 85%, preferably 82 - 84%; the temperature of the second-stage drawing is 90 - 130°C, preferably 95 - 120°C; the draw ratio is 15 - 20%.

[0049] In some specific embodiments, the speed of the second-stage drawing is 50 - 300 m / min, preferably 70 - 280 m / min, more preferably 80 - 260 m / min, and even more preferably 100 - 240 m / min.

[0050] In some specific embodiments, the total draw ratio is 2.0 - 5.0 times, preferably 2.2 - 4.5 times, more preferably 2.4 - 4.0 times, and even more preferably 2.5 - 3.5 times.

[0051] In some specific embodiments, the temperature during tension heat setting is 100 - 220°C, preferably 110 - 210°C, more preferably 120 - 200°C, and even more preferably 130 - 180°C.

[0052] In some specific embodiments, the temperature during relaxation heat setting is 60 - 150°C, preferably 70 - 140°C, more preferably 80 - 130°C, and even more preferably 90 - 120°C.

[0053] Based on the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention. The reagents and raw materials used in the present invention are all commercially available.

[0054] The positive and progressive effects of the present invention are as follows:

[0055] First, the present invention first optimizes the polymerization process to obtain a polyamide 56 melt with less and uniform oligomer content. Secondly, by controlling parameters such as the dynamic viscosity of the melt, the temperature of the melt conveying pipeline, the length of the melt pipeline conveying, the residence time of the melt, and the melt pressure drop from the melt booster pump to the inlet of the spinning box and the melt pressure at the inlet of the spinning box, the gel phenomenon and viscosity fluctuation phenomenon caused by the long-term residence of the high-temperature polyamide 56 melt are reduced, and the requirements for direct spinning of the polyamide 56 melt are realized. Finally, by optimizing the spinning process, the production of polyamide 56 staple fibers is stable, with few floating single filaments and injection head filaments, a high fiber forming rate, and few defect contents.

[0056] Second, by adopting the method for preparing polyamide 56 staple fibers by direct melt spinning according to the present invention, through optimizing the direct melt spinning process and controlling parameters such as the dynamic viscosity of the melt, the temperature of the melt conveying pipeline, the length of the melt pipeline conveying, the residence time of the melt, and the melt pressure drop from the melt booster pump to the inlet of the spinning box and the melt pressure at the inlet of the spinning box, not only can the production of large-capacity polyamide 56 staple fibers be realized, but also the gel content in the melt from the melt booster pump to the spinning box can be effectively reduced.

[0057] Specifically, the annual output of the polyamide 56 staple fibers is ≤60,000 tons / line, preferably ≤50,000 tons / line, more preferably ≤40,000 tons / line, and further preferably ≤30,000 tons / line; the number of spinning positions is ≤50 positions / line, preferably ≤40 positions / line, more preferably ≤30 positions / line, and further preferably ≤25 positions / line; the number of spinning heads is 1-8 heads / position, preferably 2-4 heads / position. The preparation method of the present invention saves the processes such as melt pelletizing, slice drying, and screw melting in the slice spinning process, and greatly reduces the production cost of polyamide 56 staple fibers. The gel content is ≤1.0 wt% / 6 months, preferably ≤0.8 wt% / 6 months, more preferably ≤0.6 wt% / 6 months, and further preferably ≤0.4 wt% / 6 months. The reduction of the gel content greatly reduces the number of disassembly, calcination, and cleaning of the melt pipeline and the spinning box, and reduces the production cost.

[0058] Thirdly, by arranging a superheated saturated steam device and a monomer suction device below the spinning box body, the present invention sprays superheated saturated steam from the periphery below the spinneret plate. The polyamide oligomers overflowing from the spinneret holes and the fiber surface are dissolved in the superheated saturated steam and then taken away by monomer suction, keeping the spinneret plate and the area below it clean, prolonging the scraping period of the spinning component, reducing the phenomena of head-end filaments and single filament breaks caused by oligomers during spinning, and improving the spinning production stability and the production rate.

[0059] Fourthly, by selecting a suitable antioxidant and optimizing its addition amount, the present invention can improve the mechanical properties and cotton-like feel of polyamide 56 staple fibers, and improve the strength and wear resistance of blended yarns.

[0060] Fifthly, by optimizing the polymerization formula, the present invention can obtain polyamide 56 staple fibers with good cotton-like feel, low defect content, good mechanical properties, large elongation, good crimp effect and fluffiness, and good hand feeling, which can meet the requirements of blending with cotton, linen, silk, wool and other chemical fibers. Specific Embodiments

[0061] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0062] Testing Methods:

[0063] (1) Denier: Bundle fiber break-off cutting and weighing method, determined according to GB / T 14343.

[0064] (2) Fiber length: Bundle fiber break-off cutting and weighing method, determined according to GB / T 14336.

[0065] (3) Specific resistance: Determined according to GB / T 14342.

[0066] (4) Crimp number: Determined according to GB / T 14338.

[0067] (5) Tensile strength and elongation: Determined according to GB / T 14337.

[0068] (6) Defect content: Manual selection and weighing method.

[0069] (7) Dry heat shrinkage rate: Executed according to the provisions of FZ / T 50004, and the heat treatment temperature is 180°C.

[0070] (8) Number of floating single filaments: Manually counted.

[0071] (9) Number of nozzle tip filaments: Manually counted.

[0072] (10) Yield rate: Yield rate = (mass of the prepared finished fiber / total mass of the polyamide melt input) × 100%.

[0073] (11) Gel content: Randomly extract melt samples from 6 places in the melt transfer pipeline after 6 months of production line operation, measure and take the average value according to the following method. Weigh the mass of the melt sample after cooling and drying as A1. After reflux extraction using the Soxhlet extraction method, take out the sample and dry it, and weigh the mass of the sample in the filter paper bag as A2. The calculation formula for gel content: Gel content wt% = A2 / A1 * 100%.

[0074] (12) Cotton-like feeling: Manually judged.

[0075] (13) Relative viscosity: By the Ubbelohde viscometer concentrated sulfuric acid method: Accurately weigh 0.5 ± 0.0002 g of the dried polyamide melt sample taken online, add 50 mL of concentrated sulfuric acid (96 wt%) to dissolve it; measure and record the flowing time t0 of the concentrated sulfuric acid and the flowing time t of the polyamide sample solution in a 25 °C constant temperature water bath. The calculation formula for viscosity number: Relative viscosity = t / t0; t - flowing time of the solution; t0 - flowing time of the solvent.

[0076] (14) Amino group content: Determined according to an automatic titrator.

[0077] (15) Oligomer content: By the boiling water method, the polyamide 56 melt is extracted in hot water at ≥ 97 °C, and the hot water extractable content of the dry chips is calculated by the mass difference of the dry chips before and after extraction.

[0078] Example 1: Bright polyamide 56 staple fiber with a specification of 1.2 D × 38 mm

[0079] Preparation of polyamide 56 melt

[0080] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0081] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.05:1; the concentration of the polyamide 56 salt solution is 50 wt%; the pH value of the polyamide 56 salt solution is 8.0;

[0082] The pressure of the prepolymerization is 1.7 MPa, and the temperature of the prepolymerization is 250 °C;

[0083] The pressure of the polycondensation is -0.06 MPa, and the temperature of the polycondensation is 282 °C;

[0084] An antioxidant is added during the polymerization process. The antioxidant is selected from sodium hypophosphite, and the addition amount is 25 ppm;

[0085] The relative viscosity of the polyamide 56 melt is 2.75, the amino group content is 50 mmol / kg, and the oligomer content is 0.5 wt%.

[0086] Preparation of polyamide 56 staple fiber

[0087] (1) The polyamide 56 melt is sent through a melt booster pump and a melt conveying pipeline to a spinning box for drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments;

[0088] (2) The polyamide 56 raw filaments are bundled, drawn, tension heat-set, crimped, relaxation heat-set, cut, and packed to obtain the polyamide 56 staple fibers.

[0089] From the melt booster pump to the spinning box, the dynamic viscosity of the polyamide 56 melt is controlled to be 240 Pa·s;

[0090] The temperature of the melt conveying pipeline is controlled to be 280 °C;

[0091] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 26 m;

[0092] The residence time of the melt from the melt booster pump to the spinning box is 15 min;

[0093] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 5 MPa;

[0094] The melt pressure at the inlet of the spinning box is 8.0 MPa;

[0095] The drawing in step (1) is to eject the polyamide 56 melt through the spinneret of the spinning box. The spinneret is a circular spinneret, and the number of holes in the spinneret is 1200 f;

[0096] The pressure of the spinning component in the spinning box is 12 MPa, and the spinning component is a circular spinning component;

[0097] The cooling uses ring blowing cooling. The temperature of the cooling air is 18 °C, and the humidity is 90%;

[0098] The winding speed is 1300 m / min;

[0099] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 160 °C, the pressure of the saturated superheated steam is 0.8 bar, and the pressure of the monomer suction device is 7.0 bar;

[0100] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 75 °C and the draw ratio is 85%; the temperature of the second-stage drawing is 110 °C and the draw ratio is 15%.

[0101] The speed of the second-stage drawing is 200 m / min;

[0102] The total draw ratio is 2.8 times;

[0103] The temperature during the tension heat setting is 130 °C;

[0104] The temperature during the relaxation heat setting is 110 °C.

[0105] The annual output of the polyamide 56 staple fiber in this example is 20,000 tons / line, the spinning positions are 24 positions / line, and the number of spinnerets is 4 heads / position.

[0106] Example 2: Bright polyamide 56 staple fiber with a specification of 1.5D×38mm

[0107] Preparation of polyamide 56 melt

[0108] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0109] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.06:1; the concentration of the polyamide 56 salt solution is 52 wt%; the pH value of the polyamide 56 salt solution is 7.8;

[0110] The pressure of the prepolymerization is 1.72 MPa and the temperature of the prepolymerization is 250 °C;

[0111] The pressure of the polycondensation is -0.06 MPa and the temperature of the polycondensation is 280 °C;

[0112] An antioxidant is added during the polymerization process. The antioxidant is selected from sodium hypophosphite and the addition amount is 30 ppm;

[0113] The relative viscosity of the polyamide 56 melt is 2.8, the amino group content is 50 mmol / kg, and the oligomer content is 0.7 wt%.

[0114] Preparation of polyamide 56 staple fiber

[0115] (1) Feed the polyamide 56 melt through a melt booster pump and a melt transfer pipeline into a spinning box for wire drawing, cooling, oiling and winding to obtain polyamide 56 raw filaments;

[0116] (2) Bundle, draw, tension heat set, crimp, relaxation heat set, cut, and pack the polyamide 56 raw filaments to obtain the polyamide 56 staple fibers.

[0117] From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt to be 250 Pa·s;

[0118] Control the temperature of the melt delivery pipe to be 275 °C;

[0119] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 18 m;

[0120] The residence time of the melt from the melt booster pump to the spinning box is 18 min;

[0121] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 6 MPa;

[0122] The melt pressure at the inlet of the spinning box is 7.0 MPa;

[0123] The wire drawing in step (1) is to eject the polyamide 56 melt through the spinneret of the spinning box. The spinneret uses a circular spinneret, and the number of holes in the spinneret is 1000 f;

[0124] The pressure of the spinning pack in the spinning box is 9 MPa, and the spinning pack uses a circular spinning pack;

[0125] The cooling uses ring blow air cooling. The temperature of the cooling air is 18 °C, and the humidity is 85%;

[0126] The winding speed is 1200 m / min;

[0127] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 150 °C, the pressure of the saturated superheated steam is 1.8 bar, and the pressure of the monomer suction device is 7.5 bar;

[0128] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 70 °C, and the draw ratio is 85%; the temperature of the second-stage drawing is 100 °C, and the draw ratio is 15%;

[0129] The speed of the second-stage drawing is 220 m / min;

[0130] The total draw ratio is 3.0 times;

[0131] The temperature during tension heat setting is 150 °C;

[0132] The temperature during relaxation heat setting is 120 °C.

[0133] In this embodiment, the annual output of the polyamide 56 staple fiber is 20,000 tons per line, the spinning positions are 24 positions per line, and the number of spinnerets is 4 per position.

[0134] Semi-dull polyamide 56 staple fiber with a specification of 2.0D×51mm in Example 3

[0135] Preparation of polyamide 56 melt

[0136] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0137] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.05:1; the concentration of the polyamide 56 salt solution is 55 wt%; the pH value of the polyamide 56 salt solution is 7.6;

[0138] The pressure of the prepolymerization is 1.75 MPa, and the temperature of the prepolymerization is 248 °C;

[0139] The pressure of the polycondensation is -0.05 MPa, and the temperature of the polycondensation is 278 °C;

[0140] An antioxidant is added during the polymerization process. The antioxidant is selected from calcium hypophosphite, and the addition amount is 50 ppm;

[0141] Add titanium dioxide delustering agent during the flash evaporation process;

[0142] The polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.32 wt%, and by controlling the process conditions, the particle size distribution ratio of particles with a diameter of 0.2 - 0.3 μm in the polyamide 56 melt is 92.5%;

[0143] The relative viscosity of the polyamide 56 melt is 2.6, the amino group content is 48 mmol / kg, and the oligomer content is 0.8 wt%.

[0144] Preparation of polyamide 56 staple fiber

[0145] (1) Feed the polyamide 56 melt through a melt booster pump and a melt transfer pipeline into the spinning box for drawing, cooling, oiling and winding to obtain polyamide 56 raw filaments;

[0146] (2) Bundle, draw, tension heat set, crimp, relaxation heat set, cut and pack the polyamide 56 raw filaments to obtain the polyamide 56 staple fiber.

[0147] From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt to be 230 Pa·s;

[0148] Control the temperature of the melt transfer pipeline to be 276 °C;

[0149] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 22 m;

[0150] The residence time of the melt from the melt booster pump to the spinning box is 18 min;

[0151] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 5 MPa;

[0152] The melt pressure at the inlet of the spinning box is 6.0 MPa;

[0153] The wire drawing in step (1) is to eject the polyamide 56 melt through the spinneret plate of the spinning box. The spinneret plate is a circular spinneret plate, and the number of holes in the spinneret plate is 900 f;

[0154] The pressure of the spinning pack in the spinning box is 11 MPa, and the spinning pack is a circular spinning pack;

[0155] The cooling uses ring blowing cooling. The temperature of the cooling air is 17 °C, and the humidity is 88%;

[0156] The winding speed is 1100 m / min;

[0157] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 130 °C, the pressure of the saturated superheated steam is 1.6 bar, and the pressure of the monomer suction device is 7.0 bar;

[0158] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 60 °C, and the draw ratio is 82%; the temperature of the second-stage drawing is 90 °C, and the draw ratio is 18%;

[0159] The speed of the second-stage drawing is 180 m / min;

[0160] The total draw ratio is 2.8 times;

[0161] The temperature during the tension heat setting is 130 °C;

[0162] The temperature during the relaxation heat setting is 110 °C.

[0163] The annual output of the polyamide 56 staple fibers described in this example is 30,000 tons / line, the spinning positions are 24 positions / line, and the number of spinning heads is 4 heads / position.

[0164] Example 4 Semi-dull polyamide 56 staple fibers with a specification of 2.5 D × 76 mm

[0165] Preparation of polyamide 56 melt

[0166] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0167] Among them, the molar ratio of the pentamethylenediamine to the adipic acid is 1.03:1; the concentration of the polyamide 56 salt solution is 53 wt%; the pH value of the polyamide 56 salt solution is 7.9;

[0168] The pressure of the prepolymerization is 1.72 MPa, and the temperature of the prepolymerization is 245 °C;

[0169] The pressure of the polycondensation is -0.03 MPa, and the temperature of the polycondensation is 275 °C;

[0170] An antioxidant is added during the polymerization process. The antioxidant is selected from sodium hypophosphite, and the addition amount is 40 ppm;

[0171] Add titanium dioxide delustering agent during the flash evaporation process;

[0172] The polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.31 wt%, and by controlling the process conditions, the particle size distribution ratio of particles with a diameter of 0.2 - 0.3 μm in the polyamide 56 melt is 93.5%;

[0173] The relative viscosity of the polyamide 56 melt is 2.75, the amino group content is 45 mmol / kg, and the oligomer content is 0.6 wt%.

[0174] Preparation of polyamide 56 staple fiber

[0175] (1) Feed the polyamide 56 melt through a melt booster pump and a melt conveying pipeline into a spinning box for drawing, cooling, oiling and winding to obtain polyamide 56 raw filaments;

[0176] (2) Bundle, draw, tension heat set, crimp, relaxation heat set, cut and pack the polyamide 56 raw filaments to obtain the polyamide 56 staple fibers.

[0177] From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt to be 240 Pa·s;

[0178] Control the temperature of the melt conveying pipeline to be 273 °C;

[0179] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 25 m;

[0180] The residence time of the melt from the melt booster pump to the spinning box is 16 min;

[0181] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 4 MPa;

[0182] The melt pressure at the inlet of the spinning box is 9.0 MPa;

[0183] The wire drawing in step (1) is to eject the polyamide 56 melt through the spinneret of the spinning box. The spinneret is a circular spinneret, and the number of holes in the spinneret is 800 f;

[0184] The pressure of the spinning pack in the spinning box is 10 MPa, and the spinning pack is a circular spinning pack;

[0185] The cooling is carried out by ring blowing, and the temperature of the cooling air is 16 °C and the humidity is 90%;

[0186] The winding speed is 1000 m / min;

[0187] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 160 °C, the pressure of the saturated superheated steam is 1.8 bar, and the pressure of the monomer suction device is 8.0 bar;

[0188] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 65 °C and the drawing ratio is 84%; the temperature of the second-stage drawing is 100 °C and the drawing ratio is 16%;

[0189] The speed of the second-stage drawing is 160 m / min;

[0190] The total drawing multiple is 2.6 times;

[0191] The temperature during the tension heat setting is 120 °C;

[0192] The temperature during the relaxation heat setting is 100 °C.

[0193] The annual output of the polyamide 56 staple fiber in this example is 20,000 tons / line, the spinning positions are 24 positions / line, and the number of spinning heads is 2 heads / position.

[0194] Example 5 Semi-dull polyamide 56 staple fiber with a specification of 3.0 D × 76 mm

[0195] Preparation of polyamide 56 melt

[0196] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0197] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.05:1; the concentration of the polyamide 56 salt solution is 55 wt%; the pH value of the polyamide 56 salt solution is 7.8;

[0198] The pressure of the prepolymerization is 1.77 MPa, and the temperature of the prepolymerization is 240 °C;

[0199] The pressure of the polycondensation is -0.05 MPa, and the temperature of the polycondensation is 277 °C;

[0200] An antioxidant is added during the polymerization process. The antioxidant is selected from sodium hypophosphite, and the addition amount is 30 ppm;

[0201] Titanium dioxide matting agent is added during the flash evaporation process;

[0202] The polyamide 56 melt is a semi-matt melt, and its titanium dioxide content is 0.30 wt%. By controlling the process conditions, the particle size distribution ratio of particles with a diameter of 0.2 - 0.3 μm in the polyamide 56 melt is 93.8%;

[0203] The relative viscosity of the polyamide 56 melt is 2.55, the amino group content is 49 mmol / kg, and the oligomer content is 0.7 wt%.

[0204] Preparation of polyamide 56 staple fiber

[0205] (1) The polyamide 56 melt is sent to the spinning box through a melt booster pump and a melt conveying pipeline for drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments;

[0206] (2) The polyamide 56 raw filaments are bundled, drawn, tension heat-set, crimped, relaxation heat-set, cut, and packed to obtain the polyamide 56 staple fibers.

[0207] From the melt booster pump to the spinning box, the dynamic viscosity of the polyamide 56 melt is controlled to be 225 Pa·s;

[0208] The temperature of the melt conveying pipeline is controlled to be 276 °C;

[0209] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 24 m;

[0210] The residence time of the melt from the melt booster pump to the spinning box is 15 min;

[0211] The melt pressure drop from the melt booster pump to the spinning box inlet is 5 MPa;

[0212] The melt pressure at the inlet of the spinning box is 8.5 MPa;

[0213] The drawing in step (1) is to eject the polyamide 56 melt through the spinneret of the spinning box. The spinneret is a circular spinneret, and the number of holes in the spinneret is 700 f;

[0214] The pressure of the spinning pack in the spinning box is 9 MPa, and the spinning pack adopts a circular spinning pack;

[0215] The cooling adopts ring blowing cooling, the temperature of the cooling air is 16 °C, and the humidity is 85%;

[0216] The winding speed is 900 m / min;

[0217] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 140 °C, the pressure of the saturated superheated steam is 1.6 bar, and the pressure of the monomer suction device is 7.0 bar;

[0218] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 50 °C, and the draw ratio is 80%; the temperature of the second-stage drawing is 110 °C, and the draw ratio is 20%;

[0219] The speed of the second-stage drawing is 150 m / min;

[0220] The total draw ratio is 2.5 times;

[0221] The temperature during the tension heat setting is 120 °C;

[0222] The temperature during the relaxation heat setting is 110 °C.

[0223] The annual output of the polyamide 56 staple fiber in this example is 15,000 tons / line, the spinning positions are 24 positions / line, and the number of spinning heads is 2 heads / position.

[0224] Example 6 Full dull polyamide 56 staple fiber with a specification of 5.0 D × 120 mm

[0225] Preparation of polyamide 56 melt

[0226] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0227] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.04:1; the concentration of the polyamide 56 salt solution is 56 wt%; the pH value of the polyamide 56 salt solution is 7.5;

[0228] The pressure of the prepolymerization is 1.7 MPa, and the temperature of the prepolymerization is 243 °C;

[0229] The pressure of the polycondensation is -0.04 MPa, and the temperature of the polycondensation is 274 °C;

[0230] An antioxidant is added during the polymerization process. The antioxidant is selected from antioxidant 1097, and the addition amount is 25 ppm;

[0231] Add titanium dioxide matting agent during the flash evaporation process;

[0232] The polyamide 56 melt is a full-matt melt, with a titanium dioxide content of 1.52 wt%, and by controlling the process conditions, the particle size distribution ratio of particles with a size of 0.2 - 0.3 μm in the polyamide 56 melt is 93.7%;

[0233] The relative viscosity of the polyamide 56 melt is 2.7, the amino group content is 44 mmol / kg, and the oligomer content is 0.6 wt%.

[0234] Preparation of polyamide 56 staple fiber

[0235] (1) Feed the polyamide 56 melt through a melt booster pump and a melt conveying pipeline into a spinning box for drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments;

[0236] (2) Bundle, draw, tension heat-set, crimp, relax heat-set, cut, and pack the polyamide 56 raw filaments to obtain the polyamide 56 staple fibers.

[0237] From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt to be 245 Pa·s;

[0238] Control the temperature of the melt conveying pipeline to be 278 °C;

[0239] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 28 m;

[0240] The residence time of the melt from the melt booster pump to the spinning box is 20 min;

[0241] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 4 MPa;

[0242] The melt pressure at the inlet of the spinning box is 7.0 MPa;

[0243] The drawing in step (1) is to extrude the polyamide 56 melt through a spinneret plate of the spinning box. The spinneret plate is a circular spinneret plate with 500 holes;

[0244] The pressure of the spinning component in the spinning box is 10 MPa, and the spinning component is a circular spinning component;

[0245] The cooling uses ring blowing air cooling, with the cooling air temperature being 17 °C and the humidity being 88%;

[0246] The winding speed is 700 m / min;

[0247] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 180°C, the pressure of the saturated superheated steam is 1.5 bar, and the pressure of the monomer suction device is 8.0 bar;

[0248] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 50°C, and the draw ratio is 83%; the temperature of the second-stage drawing is 110°C, and the draw ratio is 17%;

[0249] The speed of the second-stage drawing is 130 m / min;

[0250] The total draw ratio is 2.6 times;

[0251] The temperature during the tension heat setting is 130°C;

[0252] The temperature during the relaxation heat setting is 120°C.

[0253] The annual output of the polyamide 56 staple fiber in this example is 15,000 tons / line, the spinning positions are 12 positions / line, and the number of spinning heads is 4 heads / position.

[0254] Example 7 Full dull polyamide 56 staple fiber with a specification of 15.0 D×120 mm

[0255] Preparation of polyamide 56 melt

[0256] Prepare a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flash evaporation and polycondensation;

[0257] Among them, the molar ratio of pentamethylenediamine to adipic acid is 1.06:1; the concentration of the polyamide 56 salt solution is 50 wt%; the pH value of the polyamide 56 salt solution is 7.9;

[0258] The pressure of the prepolymerization is 1.72 MPa, and the temperature of the prepolymerization is 247°C;

[0259] The pressure of the polycondensation is -0.06 MPa, and the temperature of the polycondensation is 276°C;

[0260] An antioxidant is added during the polymerization process. The antioxidant is selected from antioxidant 1010, and the addition amount is 28 ppm;

[0261] Add titanium dioxide delustering agent during the flash evaporation process;

[0262] The polyamide 56 melt is a full dull melt, its titanium dioxide content is 1.50 wt%, and by controlling the process conditions, the particle size distribution ratio of particles with a diameter of 0.2 - 0.3 μm in the polyamide 56 melt is 94.2%;

[0263] The relative viscosity of the polyamide 56 melt is 2.6, the amino group content is 53 mmol / kg, and the oligomer content is 0.5 wt%.

[0264] Preparation of polyamide 56 staple fiber

[0265] (1) The polyamide 56 melt is sent through a melt booster pump and a melt conveying pipeline to a spinning box for drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments.

[0266] (2) The polyamide 56 raw filaments are bundled, drawn, tension heat-set, crimped, relaxation heat-set, cut, and packaged to obtain the polyamide 56 staple fibers.

[0267] From the melt booster pump to the spinning box, the dynamic viscosity of the polyamide 56 melt is controlled to be 240 Pa·s.

[0268] The temperature of the melt conveying pipeline is controlled to be 278 °C.

[0269] The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 25 m.

[0270] The residence time of the melt from the melt booster pump to the spinning box is 16 min.

[0271] The melt pressure drop from the melt booster pump to the inlet of the spinning box is 6 MPa.

[0272] The melt pressure at the inlet of the spinning box is 7.5 MPa.

[0273] The drawing in step (1) is to eject the polyamide 56 melt through a spinneret plate of the spinning box. The spinneret plate is a circular spinneret plate, and the number of holes in the spinneret plate is 350 f.

[0274] The pressure of the spinning component in the spinning box is 12 MPa, and the spinning component is a circular spinning component.

[0275] The cooling uses ring blowing cooling. The temperature of the cooling air is 18 °C, and the humidity is 85%.

[0276] The winding speed is 450 m / min.

[0277] A saturated superheated steam device and a monomer suction device are arranged below the spinning box. The temperature of the saturated superheated steam is 150 °C, the pressure of the saturated superheated steam is 1.4 bar, and the pressure of the monomer suction device is 7.0 bar.

[0278] In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 55°C, and the draw ratio is 82%; the temperature of the second-stage drawing is 100°C, and the draw ratio is 17%.

[0279] The speed of the second-stage drawing is 120 m / min;

[0280] The total draw ratio is 2.4 times;

[0281] The temperature during the tension heat setting is 120°C;

[0282] The temperature during the relaxation heat setting is 110°C.

[0283] In this example, the annual output of the polyamide 56 staple fiber is 12,000 tons / line, the spinning positions are 24 positions / line, and the number of spinnerets is 2 spinnerets / position.

[0284] Comparative Example 1

[0285] The bright polyamide 56 staple fiber with a specification of 1.5D×38mm was prepared by the same method as in Example 2, except that no antioxidant was added during the polymerization process.

[0286] Comparative Example 2

[0287] The bright polyamide 56 staple fiber with a specification of 1.5D×38mm was prepared by the same method as in Example 2, except that the relative viscosity of the polyamide 56 melt was 2.3.

[0288] Comparative Example 3

[0289] The bright polyamide 56 staple fiber with a specification of 1.5D×38mm was prepared by the same method as in Example 2, except that the oligomer content of the polyamide 56 melt was 1.25 wt%.

[0290] Comparative Example 4

[0291] The bright polyamide 56 staple fiber with a specification of 1.5D×38mm was prepared by the same method as in Example 2, except that the length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box was 60 m.

[0292] Comparative Example 5

[0293] The bright polyamide 56 staple fiber with a specification of 1.5D×38mm was prepared by the same method as in Example 2, except that the residence time of the melt from the melt booster pump to the spinning box was 55 min.

[0294] Comparative Example 6

[0295] The bright polyamide 56 staple fibers with a specification of 1.5D×38mm were prepared by the same method as in Example 2, except that the temperature of the melt transfer pipeline was controlled at 298 °C.

[0296] Comparative Example 7

[0297] The bright polyamide 56 staple fibers with a specification of 1.5D×38mm were prepared by the same method as in Example 2, except that from the melt booster pump to the spinning box, the dynamic viscosity of the polyamide 56 melt was controlled at 150 Pa·s.

[0298] Comparative Example 8

[0299] The bright polyamide 56 staple fibers with a specification of 1.5D×38mm were prepared by the same method as in Example 2, except that from the melt booster pump to the inlet of the spinning box, the melt pressure drop was 12 MPa, and the melt pressure at the inlet of the spinning box was 6.0 MPa.

[0300] Comparative Example 9

[0301] The bright polyamide 56 staple fibers with a specification of 1.5D×38mm were prepared by the same method as in Example 2, except that no saturated superheated steam device and monomer suction device were provided below the spinning box.

[0302] Comparative Example 10

[0303] The bright polyamide 56 staple fibers with a specification of 1.5D×38mm were prepared by the same method as in Example 2, except that the polyamide 56 melt obtained in step (1) was first granulated and dried to obtain chips, and then melted by a single screw and sent to the spinning box through the melt transfer pipeline, and the polyamide 56 staple fibers were prepared by chip spinning.

[0304] Table 1 Parameters of the polyamide 56 staple fibers prepared in the examples and comparative examples

[0305]

[0306] By using the preparation method of the polyamide 56 staple fibers of the present invention, by optimizing the direct melt spinning process and controlling parameters such as the dynamic viscosity of the melt, the temperature of the melt transfer pipeline, the length of the melt pipeline transfer, the residence time of the melt, and the melt pressure drop from the melt booster pump to the inlet of the spinning box and the melt pressure at the inlet of the spinning box, the polyamide 56 melt can be stabilized. It can not only realize the production of large-capacity polyamide 56 staple fibers, but also effectively reduce the gel content in the melt from the melt booster pump to the spinning box, and make the prepared polyamide 56 staple fibers have the advantages of good cotton feel, few defects, good mechanical properties, large elongation, good crimping effect and fluffiness, and good hand feeling.

[0307] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of melt direct spinning polyamide 56 staple fiber, characterized in that, The fineness of the polyamide 56 staple fiber is ≤100 D, the breaking strength is 4.0 - 5.5 cN / dtex, the elongation at break is 40 - 110%, the dry heat shrinkage rate is 4.0 - 9.0%, and the specific resistance is ≤5.0×10 7 Ω·cm; The preparation method at least includes the following steps: (1) Feed the polyamide 56 melt through a melt booster pump and a melt conveying pipeline into a spinning box for drawing, cooling, oiling, and winding to obtain polyamide 56 raw filaments. (2) Bundle, draw, tension heat-set, crimp, relax heat-set, cut, and package the polyamide 56 raw filaments to obtain the polyamide 56 staple fibers. When the polyamide 56 melt is a bright melt, its titanium dioxide content is 0; when the polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.2 - 0.4 wt%; when the polyamide 56 melt is a full-dull melt, its titanium dioxide content is 1.2 - 2.0 wt%. Among them, from the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt ≥ 180 Pa·s, control the temperature of the melt conveying pipeline to be 260 - 295 °C, the melt pipeline conveying length of the polyamide 56 melt from the melt booster pump to the spinning box is 10 - 50 m, the melt residence time from the melt booster pump to the spinning box is 8 - 45 min, the melt pressure drop from the melt booster pump to the spinning box inlet is ≤ 10 MPa, and the melt pressure at the spinning box inlet is ≥ 6.5 MPa; a saturated superheated steam device and a monomer suction device are arranged below the spinning box. An antioxidant is added during the polymerization of pentamethylenediamine and adipic acid to prepare polyamide 56; the relative viscosity of the polyamide 56 melt is 2.4 - 3.4, and the oligomer content of the polyamide 56 melt is ≤ 1.1 wt%.

2. The method according to claim 1, characterized in that, When the polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.25 - 0.35 wt%; and / or The amino group content of the polyamide 56 melt is 30 - 100 mmol / kg.

3. The method according to claim 1, wherein When the polyamide 56 melt is a full-dull melt, its titanium dioxide content is 1.4 - 1.8 wt%; and / or From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt ≥ 200 Pa·s; and / or Control the temperature of the melt conveying pipeline to be 263 - 293 °C; and / or The melt pipeline conveying length of the polyamide 56 melt from the melt booster pump to the spinning box is 12 - 45 m; and / or The melt residence time from the melt booster pump to the spinning box is 11 - 40 min; and / or The melt pressure drop from the melt booster pump to the spinning box inlet is ≤ 8 MPa; and / or The relative viscosity of the polyamide 56 melt is 2.45 - 3.3; and / or The oligomer content of the polyamide 56 melt is ≤ 1.0 wt%; and / or The amino group content of the polyamide 56 melt is 35 - 85 mmol / kg.

4. The method according to claim 1, characterized in that, From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt ≥ 220 Pa·s; and / or Control the temperature of the melt conveying pipeline to be 265 - 290 °C; and / or The melt pipeline conveying length of the polyamide 56 melt from the melt booster pump to the spinning box is 14 - 40 m; and / or The melt residence time from the melt booster pump to the spinning box is 13 - 35 min; and / or The melt pressure drop from the melt booster pump to the inlet of the spinning box is ≤7 MPa; and / or, The relative viscosity of the polyamide 56 melt is 2.5 - 3.2; and / or, The oligomer content of the polyamide 56 melt is ≤0.9 wt%; and / or, The amino group content of the polyamide 56 melt is 40 - 70 mmol / kg.

5. The method according to claim 1, wherein From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt ≥230 Pa·s; and / or, Control the temperature of the melt conveying pipeline to be 270 - 288 °C; and / or, The length of the melt pipeline for transporting the polyamide 56 melt from the melt booster pump to the spinning box is 16 - 35 m; and / or, The melt residence time from the melt booster pump to the spinning box is 15 - 30 min; and / or, The melt pressure drop from the melt booster pump to the inlet of the spinning box is ≤6 MPa; and / or, The melt pressure at the inlet of the spinning box is ≥7.0 MPa; and / or, The relative viscosity of the polyamide 56 melt is 2.55 - 3.0; and / or, The oligomer content of the polyamide 56 melt is ≤0.8 wt%; and / or, The amino group content of the polyamide 56 melt is 43 - 60 mmol / kg.

6. The method according to claim 1, wherein The preparation method of the polyamide 56 melt includes the following steps: preparing a polyamide 56 salt solution from pentamethylenediamine, adipic acid and water, and then obtaining the polyamide 56 melt through prepolymerization, flash evaporation and polycondensation; Adding titanium dioxide delustering agent during the flash evaporation process, and the dispersion particle size of the titanium dioxide in the polyamide 56 melt is 0.2 - 0.8 μm; The addition amount of the antioxidant is 10 - 500 ppm; the antioxidant is selected from any one or a combination of several of sodium hypophosphite, sodium acetate hypophosphite, calcium hypophosphite, phosphorous acid, antioxidant 1010, and antioxidant 1097.

7. The method according to claim 6, wherein The particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2 - 0.5 μm is above 95%; and / or, The addition amount of the antioxidant is 15 - 400 ppm.

8. The method according to claim 6, characterized in that, The particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2 - 0.3 μm is above 90%; and / or, The addition amount of the antioxidant is 20 - 300 ppm.

9. The method according to claim 6, wherein The addition amount of the antioxidant is 25 - 200 ppm.

10. The method according to claim 1, characterized in that, The temperature of the saturated superheated steam is 95 - 260 °C; and / or, The pressure of the saturated superheated steam is 0.4 - 3.5 bar; and / or, The pressure of the monomer suction device is ≥6.0 bar.

11. The method according to claim 10, characterized in that, The temperature of the saturated superheated steam is 100 - 250 °C; and / or, The pressure of the saturated superheated steam is 0.6 - 3.0 bar; and / or, The pressure of the monomer suction device is ≥6.5 bar.

12. The method according to claim 10, wherein The temperature of the saturated superheated steam is 110 - 240 °C; and / or, The pressure of the saturated superheated steam is 0.8 - 2.5 bar; and / or, The pressure of the monomer suction device is ≥7.0 bar.

13. The method according to claim 10, wherein The temperature of the saturated superheated steam is 120 - 230 °C; and / or, The pressure of the saturated superheated steam is 1.0 - 2.0 bar; and / or, The pressure of the monomer suction device is ≥7.5 bar.

14. The method according to claim 1, wherein In step (1), the pressure of the spinning pack in the spinning box is ≥6 MPa; and / or, The cooling is carried out by side blowing or ring blowing, the temperature of the cooling air is 16 - 25°C, and the humidity is 60 - 95%; and / or, The winding speed is 300 - 1500 m / min.

15. The method according to claim 14, wherein The pressure of the spinning pack in the spinning box is ≥7 MPa; and / or, The cooling is carried out by ring blowing; and / or, The temperature of the cooling air is 17 - 24°C; and / or, The humidity of the cooling air is 65 - 90%; and / or, The winding speed is 500 - 1400 m / min.

16. The method according to claim 14, wherein The pressure of the spinning pack in the spinning box is ≥8 MPa; and / or, The temperature of the cooling air is 18 - 23°C; and / or, The humidity of the cooling air is 70 - 85%; and / or, The winding speed is 600 - 1300 m / min.

17. The method according to claim 14, wherein The pressure of the spinning pack in the spinning box is ≥9 MPa; and / or, The temperature of the cooling air is 19 - 22°C; and / or, The humidity of the cooling air is 75 - 80%; and / or, The winding speed is 700 - 1200 m / min.

18. The method according to claim 1, characterized in that, In step (2), the drawing is two-stage drawing. The temperature of the first-stage drawing is 50 - 100°C, and the draw ratio is 80 - 85%; the temperature of the second-stage drawing is 90 - 130°C, and the draw ratio is 15 - 20%; and / or, The total draw ratio is 2.0 - 5.0 times.

19. The method according to claim 18, characterized in that, The speed of the second-stage drawing is 50 - 300 m / min; and / or, The temperature during the tension heat setting is 100 - 220°C; and / or, The temperature during the relaxation heat setting is 60 - 150°C.

20. The method according to claim 18, wherein The temperature of the first-stage drawing is 60 - 80°C; and / or, The draw ratio of the first-stage drawing is 82 - 84%; and / or, The temperature of the second-stage drawing is 95 - 120°C; and / or, The total draw ratio is 2.2 - 4.5 times; and / or, The speed of the second-stage drawing is 70 - 280 m / min; and / or, The temperature during the tension heat setting is 110 - 210°C; and / or, The temperature during the relaxation heat setting is 70 - 140°C.

21. The method according to claim 18, wherein The total draw ratio is 2.4 - 4.0 times; and / or, The speed of the second-stage drawing is 80 - 260 m / min; and / or, The temperature during the tension heat setting is 120 - 200°C; and / or, The temperature during the relaxation heat setting is 80 - 130°C.

22. The method according to claim 18, wherein The total draw ratio is 2.5 - 3.5 times; and / or, The speed of the second-stage drawing is 100 - 240 m / min; and / or, The temperature during the tension heat setting is 125 - 180°C; and / or, The temperature during the relaxation heat setting is 90 - 120°C.

23. A melt direct spinning polyamide 56 staple fiber, prepared by the preparation method according to any one of claims 1 to 22.

24. The polyamide 56 staple fiber according to claim 23, wherein The fineness of the polyamide 56 staple fiber is ≤80 D; and / or, The elongation at break of the polyamide 56 staple fiber is 45 - 100%; and / or, The dry heat shrinkage rate of the polyamide 56 staple fiber is 4.0 to 8.5%; and / or, The specific resistance of the polyamide 56 staple fiber is ≤ 4.5×10 7 Ω·cm.

25. The polyamide 56 staple fiber according to claim 23, wherein, The fineness of the polyamide 56 staple fiber is ≤60 D; and / or, The elongation at break of the polyamide 56 staple fiber is 50 to 90%; and / or, The dry heat shrinkage rate of the polyamide 56 staple fiber is 5.0 to 8.0%; and / or, The specific resistance of the polyamide 56 staple fiber is ≤ 4.0×10 7 Ω·cm.

26. The polyamide 56 staple fiber according to claim 23, wherein The fineness of the polyamide 56 staple fiber is ≤30 D; and / or, The elongation at break of the polyamide 56 staple fiber is 60 to 85%; and / or, The dry heat shrinkage rate of the polyamide 56 staple fiber is 6.0 to 7.0%; and / or, The specific resistance of the polyamide 56 staple fiber is ≤ 3.0×10 7 Ω·cm.

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