Polyamide flat yarn, polyamide bulk bag and method for producing the same

Abstract

This invention relates to polyamide flat yarns, polyamide container bags, and their preparation methods. The raw materials for production include at least polyamide resin, specifically one or more of polyamide 5X, polyamide 6X, polyamide 6, polyamide 5T / 5X, polyamide 5T / 66, and polyamide 6T / 66. X is selected from one or more of bisaccharide, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid. This invention enables the preparation of polyamide flat yarns with higher tensile strength using polyamide resin as a raw material, thereby obtaining polyamide container bags with better tensile strength, dimensional stability, heat resistance, low-temperature resistance, and abrasion resistance.

Description

Technical Field

[0001] This invention relates to the field of polyamide materials technology, and in particular to a polyamide flat yarn, a polyamide container bag, and a method for preparing the same. Background Technology

[0002] FIBCs, also known as flexible container bags, ton bags, or space bags, are a type of unitized container. When used with cranes or forklifts, they enable unitized transport of goods. They are widely used for transporting powdery, granular, and lumpy goods such as food, grains, pharmaceuticals, chemicals, and minerals. Using FIBCs can accelerate transportation, shorten loading and unloading time, speed up goods turnover, reduce labor intensity, improve efficiency, save labor, simplify packaging and transportation costs, effectively protect goods, ensure freight quality, and reduce damage.

[0003] Existing FIBCs are mainly woven from polypropylene (PP) and / or polyester (PET) flat yarns. During use, the low strength of polypropylene (PP) and / or polyester (PET) flat yarns can easily cause wear and tear on the FIBCs, making them unusable for repeated use. They also have poor aging resistance and low-temperature resistance. Summary of the Invention

[0004] To overcome at least one of the defects of the prior art, in a first aspect, one embodiment of the present invention provides a polyamide flat filament, the raw material of which includes at least a polyamide resin, wherein the polyamide resin includes one or more of polyamide 5X, polyamide 6X, polyamide 6, polyamide 5T / 5X, polyamide 5T / 66, and polyamide 6T / 66, wherein X is selected from one or more of bisaccharide, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0005] Secondly, one embodiment of the present invention provides a method for preparing the above-mentioned polyamide flat yarn, the method comprising:

[0006] 1) The polyamide resin is heated to a molten state to form a first polyamide melt and a second polyamide melt;

[0007] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; the second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament.

[0008] 3) The first and second nascent yarns are post-processed to obtain the polyamide warp flat yarn and the polyamide weft flat yarn.

[0009] Thirdly, one embodiment of the present invention provides the application of the above-described polyamide flat yarn or the polyamide flat yarn prepared by the above-described preparation method in polyamide container bags.

[0010] Fourthly, one embodiment of the present invention provides a polyamide container bag, which includes a polyamide container bag base fabric, said polyamide container bag base fabric being woven from the above-described polyamide flat yarn or polyamide flat yarn prepared by the above-described preparation method.

[0011] Fifthly, one embodiment of the present invention provides a method for preparing the above-mentioned polyamide container bag, the method comprising: weaving the above-mentioned polyamide flat yarn or the polyamide flat yarn obtained by the above-mentioned preparation method into a base fabric by a weaving machine, cutting the base fabric, and then sewing it with the straps and reinforcing ribs to obtain the polyamide container bag.

[0012] In a sixth aspect, one embodiment of the present invention provides a polyamide container bag, which includes polyamide warp flat yarns and polyamide weft flat yarns, wherein the tensile strength of the polyamide warp flat yarns is ≥5.0 cN / dtex and the tensile strength of the polyamide weft flat yarns is ≥4.8 cN / dtex.

[0013] The polyamide flat yarn of one embodiment of the present invention can be prepared from polyamide resin to obtain polyamide flat yarn with specific width and thickness and higher tensile strength.

[0014] The polyamide container bag of one embodiment of the present invention can be prepared by using polyamide flat yarns with specific properties, thereby obtaining a polyamide container bag with better tensile strength, dimensional stability, heat resistance, low temperature resistance and wear resistance. Detailed Implementation

[0015] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the description herein is for illustrative purposes only and not intended to limit the present invention.

[0016] One embodiment of the present invention provides a polyamide flat filament, the raw material of which includes at least a polyamide resin. The polyamide resin includes one or more of polyamide 5X, polyamide 6X, polyamide 6, polyamide 5T / 5X, polyamide 5T / 66, and polyamide 6T / 66, wherein X is selected from one or more of bisaccharide, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0017] In one embodiment, the polyamide resin has a melting point of 180-310°C, further 200-300°C, and even further 220-290°C, for example 225°C, 235°C, 240°C, 245°C, 255°C, 260°C, 265°C, 270°C, 278°C, and 285°C.

[0018] In one embodiment, the relative viscosity of the polyamide resin is 2.4-3.8, further 2.6-3.5, even further 2.8-3.3, and still further 2.9-3.0, for example 2.9, 3.0, 3.1, 3.2, 3.3.

[0019] In one embodiment, the terminal amino content of the polyamide resin is 10-70 mmol / kg, further 20-60 mmol / kg, and even further 30-50 mmol / kg, for example 35 mmol / kg, 40 mmol / kg, 45 mmol / kg, or 48 mmol / kg.

[0020] In one embodiment, the water content of the polyamide resin is 300-1000 ppm, further 400-900 ppm, and even further 500-800 ppm, for example 330 ppm, 380 ppm, 510 ppm, 520 ppm, 590 ppm, and 620 ppm.

[0021] In one embodiment, the polyamide flat yarn includes polyamide warp flat yarn and polyamide weft flat yarn.

[0022] In one embodiment, the width of the polyamide warp flat filament is 1.0-3.0 mm, further 1.2-2.5 mm, and even further 1.4-2.3 mm, for example 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, or 2.2 mm.

[0023] In one embodiment, the thickness of the polyamide warp filament is 0.06-0.20 mm, further 0.08-0.16 mm, and even further 0.10-0.13 mm, for example 0.12 mm.

[0024] In one embodiment, the width of the polyamide weft flat filament is 1.0-3.0 mm, further 1.3-2.6 mm, and even further 1.6-2.3 mm, for example 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, or 2.2 mm.

[0025] In one embodiment, the thickness of the polyamide weft flat yarn is 0.06-0.30 mm, further 0.08-0.25 mm, and even further 0.10-0.20 mm, for example 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, and 0.19 mm.

[0026] In one embodiment, the tensile strength of the polyamide warp flat filament is ≥5.0 cN / dtex, further ≥5.5 cN / dtex, and even further ≥5.8 cN / dtex.

[0027] In one embodiment, the breaking strength of the polyamide weft flat yarn is ≥4.8 cN / dtex, further ≥5.2 cN / dtex, and even further ≥5.5 cN / dtex.

[0028] One embodiment of the present invention provides a method for preparing the above-mentioned polyamide flat yarn, the method comprising:

[0029] 1) The polyamide resin is heated to a molten state to form a first polyamide melt and a second polyamide melt;

[0030] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; the second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament.

[0031] 3) The first and second nascent yarns are post-processed to obtain the polyamide warp flat yarn and the polyamide weft flat yarn.

[0032] In one embodiment, in step 1), the heating is performed using a screw, preferably a single screw, and the screw employs four-zone heating: zone one temperature is 180-290℃, preferably 200-280℃; zone two temperature is 200-300℃, preferably 220-290℃; zone three temperature is 220-320℃, preferably 240-310℃; and zone four temperature is 240-330℃, preferably 260-320℃.

[0033] In one embodiment, in step 2), the temperature of the machine head is 200-330°C, preferably 230-320°C.

[0034] In one embodiment, in step 2), the first spinneret and / or the second spinneret are circular or rectangular in shape.

[0035] In one embodiment, in step 2), the cross-section of the spinneret holes of the first spinneret and / or the second spinneret is in the shape of a straight line.

[0036] In one embodiment, in step 2), the length of the spinneret orifice of the first spinneret is 8-15mm and the width is 0.3-0.6mm, for example, the length of the spinneret orifice is 9mm, 10mm, 11mm, 12mm, 13mm, 14mm; and the width of the spinneret orifice is 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm.

[0037] In one embodiment, in step 2), the spinneret has a spinneret orifice length of 7-15mm and a width of 0.3-0.75mm, for example, spinneret orifice lengths of 7.5mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, and 14mm; and spinneret orifice widths of 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, and 0.7mm.

[0038] In one embodiment, the post-processing in step 3) includes: cooling the first nascent filament and the second nascent filament respectively, performing a first-stage water bath stretching, a second-stage hot air stretching, heat setting, and filament separation and winding to obtain the polyamide warp flat filament and the polyamide weft flat filament.

[0039] In one embodiment, the process of primary water bath stretching, secondary hot air stretching and heat setting includes: primary water bath stretching between the first traction machine and the second traction machine, secondary hot air stretching between the second traction machine and the third traction machine, and then heat setting between the third traction machine and the fourth traction machine.

[0040] In one embodiment, there is no particular limitation on the number of hot rollers of the first traction machine, the second traction machine, and the second traction machine, but seven hot rollers are preferred.

[0041] In one embodiment, there is no particular limitation on the number of hot rollers of the fourth traction machine, but five hot rollers are preferred.

[0042] In one embodiment, in step 3), the cooling is performed by water bath cooling, and the temperature of the water bath cooling is 10-50°C, more specifically 20-40°C, for example 30°C.

[0043] In one embodiment, in step 3), the stretching ratio of the first-stage water bath stretching is 2.0-4.0, further 2.5-3.5, for example 2.8, 3.0, 3.2.

[0044] In one embodiment, in step 3), the stretching ratio of the secondary hot air stretching is 1.0-2.0, further 1.2-1.8, for example 1.3, 1.4, 1.5, 1.6, 1.7.

[0045] In one embodiment, in step 3), the total stretch ratio is 3.0-6.5, further 4.0-6.0, for example 4.2, 4.5, 4.7, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9.

[0046] In one embodiment, in step 3), the temperature of the primary water bath stretching is 70-100°C, and more specifically 80-90°C, for example 82°C, 85°C, or 88°C.

[0047] In one embodiment, in step 3), the temperature of the secondary hot air stretching is 100-200°C, further 120-180°C, for example 130°C, 140°C, 150°C, 160°C, or 170°C.

[0048] In one embodiment, in step 3), the heat setting temperature is 160-240°C, further 180-220°C, for example 190°C, 200°C, or 210°C.

[0049] In one embodiment, in step 3), the winding speed is 40-300 m / min, further 60-200 m / min, for example 80 m / min, 90 m / min, 100 m / min, 120 m / min, 150 m / min, or 180 m / min.

[0050] One embodiment of the present invention provides the application of the above-described polyamide flat yarn or the polyamide flat yarn prepared by the above-described preparation method in polyamide container bags.

[0051] One embodiment of the present invention provides a polyamide container bag, which includes a polyamide container bag base fabric, wherein the polyamide container bag base fabric is woven from the polyamide flat yarn described above or the polyamide flat yarn prepared by the above preparation method.

[0052] In one embodiment, the warp density of the polyamide container bag base fabric is 30-100 threads / 10cm, further 35-90 threads / 10cm, and even further 40-80 threads / 10cm.

[0053] In one embodiment, the weft density of the polyamide container bag base fabric is 30-90 threads / 10cm, further 35-80 threads / 10cm, and even further 40-70 threads / 10cm.

[0054] In one embodiment, the weight of the polyamide container bag base fabric is 100-400 g / m². 2 Further, it is 130-350g / m 2 Furthermore, it is 150-300g / m 2 .

[0055] In one embodiment, the longitudinal tensile strength of the polyamide container bag base fabric is ≥2200N / 5cm, further ≥2400N / 5cm, and even further ≥2700N / 5cm.

[0056] In one embodiment, the transverse tensile strength of the polyamide container bag base fabric is ≥2000N / 5cm, further ≥2200N / 5cm, and even further ≥2400N / 5cm.

[0057] In one embodiment, the longitudinal elongation at break of the polyamide container bag base fabric is ≤45%, further ≤40%, and even further ≤35%.

[0058] In one embodiment, the transverse elongation at break of the polyamide container bag base fabric is ≤50%, further ≤45%, and even further ≤40%.

[0059] In one embodiment, the heat resistance of the polyamide container bag base fabric is ≥80°C, further ≥100°C, and even further ≥120°C.

[0060] In one embodiment, the cold resistance of the polyamide container bag base fabric is ≤-10℃, further ≤-15℃, and even further ≤-20℃.

[0061] In one embodiment, the abrasion resistance of the polyamide container bag base fabric is ≥4000 revolutions, further ≥6000 revolutions, and even further ≥8000 revolutions.

[0062] One embodiment of the present invention provides a method for preparing the above-mentioned polyamide container bag, the method comprising: weaving the above-mentioned polyamide flat yarn or the polyamide flat yarn obtained by the above-mentioned preparation method into a base fabric by a weaving machine, cutting the base fabric, and then sewing it with the straps and reinforcing accessories to obtain the polyamide container bag.

[0063] One embodiment of the present invention provides a polyamide container bag, which includes polyamide warp flat yarns and polyamide weft flat yarns, wherein the tensile strength of the polyamide warp flat yarns is ≥5.0 cN / dtex and the tensile strength of the polyamide weft flat yarns is ≥4.8 cN / dtex.

[0064] In one embodiment, the width, thickness, and breaking strength of the polyamide warp flat yarn and the polyamide weft flat yarn are as described above and will not be repeated here.

[0065] In one embodiment, the raw materials for producing the polyamide warp flat yarn and / or polyamide weft flat yarn are as described above and will not be repeated here.

[0066] One embodiment of the polyamide flat yarn of the present invention uses polyamide resin as raw material, and the resulting polyamide flat yarn has appropriate width and thickness, and higher tensile strength. Polyamide bulk bags woven using the polyamide flat yarn provided by the present invention have superior tensile strength, better dimensional stability, heat resistance, cold resistance, and abrasion resistance.

[0067] The following describes a specific embodiment of the polyamide flat yarn and its preparation therein. The raw materials and testing methods involved in each embodiment and comparative example are as follows.

[0068] raw material

[0069] PA56, PA510, PA512, and PA56 / 5T were purchased from Kaisai (Jinxiang) Biomaterials Co., Ltd., and other raw materials not explicitly stated were commercially available.

[0070] Test methods

[0071] 1) Relative viscosity of resin: The viscosity was determined by the concentrated sulfuric acid method using an Ubbelohde viscometer. The steps are as follows: Accurately weigh 0.5 ± 0.0002 g of dried polyamide resin or fiber sample, add 50 mL of concentrated sulfuric acid (96%) to dissolve it, and measure and record the flow time t0 of concentrated sulfuric acid and the flow time t of polyamide 56 chips or short fiber sample solution in a 25℃ constant temperature water bath.

[0072] The calculation formula is: relative viscosity VN = t / t0; where t: solution flow time; t0: solvent flow time.

[0073] 2) Moisture content of resin: determined by Karl Fischer moisture titrator.

[0074] 3) The terminal amino groups of the resin: determined by an automatic titrator.

[0075] 4) Melting point of resin: determined by DSC.

[0076] 5) Breaking strength of flat yarn: determined according to GB / T 14344-2008 Test method for tensile properties of chemical fibers.

[0077] 6) The tensile strength, heat resistance, cold resistance, and abrasion resistance of the base fabric of the container bag shall be tested in accordance with GB / T 10454-2000:

[0078] 6-1) Tensile Strength: Take 5 standard specimens (60mm wide and 300mm long) from both the longitudinal and transverse directions of the sample. Each specimen should be rounded down to 50mm in width. If the last filament exceeds half its length, retain it; otherwise, discard it. Based on the actual conditions of the fixtures, this experiment uses 15mm wide specimen strips for testing. The strength is converted to N / 5cm. The test interval is 200mm, the test speed is 200mm / min, the temperature is 20℃, and the humidity is 65%.

[0079] 6-2) Heat resistance: Take two 20mm wide and two 30mm long test pieces from the longitudinal and transverse directions of the sample, overlap their surfaces, apply a load of 9.8N, put them in an 80℃ oven for 1 hour, separate the two overlapping test pieces, and observe whether there is any adhesion, cracks or other conditions on the sample surface.

[0080] 6-3) Cold resistance: Take two 20mm wide and two 100mm long test pieces from the longitudinal and transverse directions of the sample, respectively, place them in a -35℃ constant temperature chamber for 2 hours, fold the sample in half along the length direction to 180°, and observe whether there is any damage, cracks or other conditions on the surface of the sample.

[0081] 6-4) Abrasion resistance: Take a square slice with a side length of 100mm, place it on a TABER abrasion tester with a pair of wear wheels rotating on it, use a load weight of 750g, rotate at a speed of 60rpm, and observe the damage, cracks, etc. on the surface of the sample.

[0082] Example 1

[0083] 1) Polyamide PA56 resin (melting point 254℃, relative viscosity 2.8, terminal amino content 50mmol / kg, water content 453ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 260℃, zone two temperature is 270℃, zone three temperature is 280℃, and zone four temperature is 290℃.

[0084] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 285℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 10mm and the width is 0.5mm.

[0085] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 285℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 8mm and the width is 0.5mm.

[0086] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 40℃; the first-stage water bath stretching ratio is 3.0; the second-stage hot air stretching ratio is 1.6; the total stretching ratio is 4.8; the first-stage water bath stretching temperature is 85℃; the second-stage hot air stretching temperature is 160℃; the heat setting temperature is 220℃; and the winding speed is 80m / min.

[0087] Example 2

[0088] 1) Polyamide PA510 resin (melting point 217℃, relative viscosity 2.7, terminal amino content 30mmol / kg, water content 505ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 230℃, zone two temperature is 240℃, zone three temperature is 250℃, and zone four temperature is 260℃.

[0089] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 260℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 9mm and the width is 0.6mm.

[0090] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 260℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 8mm and the width is 0.5mm.

[0091] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 30℃; the first-stage water bath stretching ratio is 4.0; the second-stage hot air stretching ratio is 1.3; the total stretching ratio is 5.2; the first-stage water bath stretching temperature is 70℃; the second-stage hot air stretching temperature is 160℃; the heat setting temperature is 200℃; and the winding speed is 120m / min.

[0092] Example 3

[0093] 1) Polyamide PA512 resin (melting point 207℃, relative viscosity 2.9, terminal amino content 40mmol / kg, water content 584ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 220℃, zone two temperature is 230℃, zone three temperature is 240℃, and zone four temperature is 250℃.

[0094] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 250℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 8mm and the width is 0.55mm.

[0095] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 250°C, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 8 mm and the width is 0.65 mm.

[0096] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 40℃; the first-stage water bath stretching ratio is 3.5; the second-stage hot air stretching ratio is 1.4; the total stretching ratio is 4.9; the first-stage water bath stretching temperature is 90℃; the second-stage hot air stretching temperature is 140℃; the heat setting temperature is 190℃; and the winding speed is 90m / min.

[0097] Example 4

[0098] 1) Polyamide PA6 resin (melting point 220℃, relative viscosity 2.6, terminal amino content 45mmol / kg, water content 385ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 240℃, zone two temperature is 250℃, zone three temperature is 260℃, and zone four temperature is 270℃.

[0099] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 265℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 10mm and the width is 0.5mm.

[0100] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 265℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 9mm and the width is 0.75mm.

[0101] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 35℃; the first-stage water bath stretching ratio is 3.0; the second-stage hot air stretching ratio is 1.7; the total stretching ratio is 5.1; the first-stage water bath stretching temperature is 80℃; the second-stage hot air stretching temperature is 190℃; the heat setting temperature is 200℃; and the winding speed is 70m / min.

[0102] Example 5

[0103] 1) Polyamide PA66 resin (melting point 260℃, relative viscosity 2.7, terminal amino content 40mmol / kg, water content 524ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 270℃, zone two temperature is 280℃, zone three temperature is 290℃, and zone four temperature is 290℃.

[0104] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 290℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 10mm and the width is 0.5mm.

[0105] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 290℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 8mm and the width is 0.5mm.

[0106] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 50℃; the first-stage water bath stretching ratio is 3.5; the second-stage hot air stretching ratio is 1.4; the total stretching ratio is 4.9; the first-stage water bath stretching temperature is 80℃; the second-stage hot air stretching temperature is 180℃; the heat setting temperature is 230℃; and the winding speed is 80m / min.

[0107] Example 6

[0108] 1) Polyamide PA610 resin (melting point 223℃, relative viscosity 2.8, terminal amino content 50mmol / kg, water content 620ppm) is heated to a molten state to form a first polyamide melt and a second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 220℃, zone two temperature is 240℃, zone three temperature is 260℃, and zone four temperature is 270℃.

[0109] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 265℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 8mm and the width is 0.6mm.

[0110] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 265℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 8mm and the width is 0.6mm.

[0111] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 30℃; the first-stage water bath stretching ratio is 4.0; the second-stage hot air stretching ratio is 1.2; the total stretching ratio is 4.8; the first-stage water bath stretching temperature is 70℃; the second-stage hot air stretching temperature is 150℃; the heat setting temperature is 190℃; and the winding speed is 100m / min.

[0112] Example 7

[0113] 1) Polyamide PA56 / 5T resin (melting point 270℃, relative viscosity 2.75, terminal amino content 50mmol / kg, water content 325ppm) is heated to a molten state to form the first polyamide melt and the second polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 270℃, zone two temperature is 280℃, zone three temperature is 290℃, and zone four temperature is 300℃.

[0114] 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 295℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 9mm and the width is 0.55mm.

[0115] The second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 295℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 9mm and the width is 0.55mm.

[0116] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyamide warp flat yarns and polyamide weft flat yarns. The water bath cooling temperature is 50℃; the first-stage water bath stretching ratio is 3.2; the second-stage hot air stretching ratio is 1.5; the total stretching ratio is 4.8; the first-stage water bath stretching temperature is 95℃; the second-stage hot air stretching temperature is 180℃; the heat setting temperature is 240℃; and the winding speed is 90m / min.

[0117] Example 8

[0118] Polyamide flat filaments were prepared using essentially the same raw materials and processes as in Example 1, with the only difference being that the relative viscosity of the polyamide PA56 resin was 3.0.

[0119] Comparative Example 1

[0120] 1) Polypropylene (PP) (melting point 160℃, melt index 38g / 10min, moisture content 10ppm) is heated to a molten state to form a first polypropylene melt and a second polypropylene melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 160℃, zone two temperature is 180℃, zone three temperature is 200℃, and zone four temperature is 220℃.

[0121] 2) The first polypropylene melt is accurately metered by the metering pump in the die head and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 200℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 9mm and the width is 0.5mm.

[0122] The second polypropylene melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 200℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 7.2mm and the width is 0.5mm.

[0123] 3) The first and second nascent filaments are cooled separately, and then subjected to a first-stage water bath stretching between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Finally, heat setting is carried out between the third and fourth / fifth seven-roll traction machines, followed by filament separation and winding to obtain polypropylene warp flat filaments and polypropylene weft flat filaments. The water bath cooling temperature is 40℃; the first-stage water bath stretching ratio is 4.0; the second-stage hot air stretching ratio is 1.2; the total stretching ratio is 4.8; the first-stage water bath stretching temperature is 80℃; the second-stage hot air stretching temperature is 120℃; the heat setting temperature is 140℃; and the winding speed is 100m / min.

[0124] Comparative Example 2

[0125] 1) Polyester PET (melting point 263℃, intrinsic viscosity 0.68, moisture content 34ppm) is heated to a molten state to form a first polyester melt and a second polyester melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone one temperature is 270℃, zone two temperature is 280℃, zone three temperature is 290℃, and zone four temperature is 295℃.

[0126] 2) The first polyester melt is accurately metered by the metering pump at the die head and extruded through the first spinneret of the spinning assembly to form the first nascent filament; wherein, the die head temperature is 290℃, the first spinneret is circular in shape, the cross-section of the spinneret hole of the first spinneret is in the shape of a straight line, and the length of the spinneret hole of the first spinneret is 9mm and the width is 0.55mm.

[0127] The second polyester melt is accurately metered by the metering pump at the die head and extruded through the second spinneret of the spinning assembly to form the second nascent filament. The die head temperature is 290℃, the second spinneret is circular, the cross-section of the spinneret orifice is straight, and the length of the spinneret orifice is 9mm and the width is 0.55mm.

[0128] 3) The first and second nascent yarns are cooled separately, and a first-stage water bath stretching is performed between the first and second seven-roll traction machines. A second-stage hot air stretching is performed between the second and third seven-roll traction machines. Then, heat setting is performed between the third and fourth / fifth seven-roll traction machines. The yarns are then separated and wound up to obtain polyester warp flat yarns and polyester weft flat yarns. The water bath cooling temperature is 40℃; the first-stage water bath stretching ratio is 3.5; the second-stage hot air stretching ratio is 1.4; the total stretching ratio is 4.9; the first-stage water bath stretching temperature is 90℃; the second-stage hot air stretching temperature is 180℃; the heat setting temperature is 230℃; and the winding speed is 90m / min.

[0129] Comparative Example 3

[0130] Polyamide flat filaments were prepared using essentially the same raw materials and processes as in Example 1, with the only difference being that in step 2), the length of the spinneret orifice of the first spinneret was 10 mm and the width was 0.25 mm; the length of the spinneret orifice of the second spinneret was 10 mm and the width was 0.25 mm.

[0131] Comparative Example 4

[0132] Polyamide flat filaments were prepared using essentially the same raw materials and processes as in Example 1, with the only difference being that in step 2), the length of the spinneret orifice of the first spinneret was 20 mm and the width was 0.5 mm; and the length of the spinneret orifice of the second spinneret was 17.5 mm and the width was 0.5 mm.

[0133] Comparative Example 5

[0134] 1) Polyamide PA56 resin (melting point 254℃, relative viscosity 2.8, terminal amino content 50mmol / kg, water content 453ppm) is heated to a molten state to form polyamide melt; wherein, a single screw is used for heating, and the single screw adopts four-zone heating: zone 1 temperature is 260℃, zone 2 temperature is 270℃, zone 3 temperature is 280℃, and zone 4 temperature is 290℃.

[0135] 2) After the polyamide melt is accurately metered by the metering pump in the die head, it is extruded through the die head, cooled, and stretched to form a cast film. Then, it is cut into flat filaments by a cutter for stretching. However, stretching flat filaments is difficult, and there are many broken filaments in production, making it impossible to produce polyamide flat filaments normally.

[0136] Application Example 1

[0137] The polyamide warp flat yarn and polyamide weft flat yarn obtained in Example 1 are woven into a polyamide container bag base fabric using a weaving machine. The polyamide container bag base fabric is then cut and sewn together with the straps and reinforcing ribs to obtain a polyamide container bag.

[0138] Application Example 2

[0139] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 2 were woven together.

[0140] Application Example 3

[0141] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 3 were woven together.

[0142] Application Example 4

[0143] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 4 were woven together.

[0144] Application Example 5

[0145] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 5 were woven together.

[0146] Application Example 6

[0147] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 6 were woven together.

[0148] Application Example 7

[0149] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 7 were woven together.

[0150] Application Example 8

[0151] Polyamide bulk bags were prepared using a process that was essentially the same as in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Example 8 were woven together.

[0152] Comparative Application Example 1

[0153] Polypropylene bulk bags were prepared using a process essentially the same as that used in Application Example 1, except that the polypropylene warp flat yarns and polypropylene weft flat yarns obtained in Comparative Example 1 were woven together.

[0154] Comparative Application Example 2

[0155] Polyester container bags were prepared using a process that was essentially the same as that used in Application Example 1, except that the polyester warp flat yarns and polyester weft flat yarns obtained in Comparative Example 2 were woven together.

[0156] Comparative Application Example 3

[0157] Polyamide bulk bags were prepared using a process that was essentially the same as that used in Application Example 1, except that the polyamide warp flat yarns and polyamide weft flat yarns obtained in Comparative Example 3 were woven together.

[0158] Comparative Application Example 4

[0159] Because the widths of the polyamide warp flat yarns and polyamide weft flat yarns prepared in Comparative Example 4 are too large, they cannot be woven into the base fabric of polyamide container bags, and therefore polyamide container bags cannot be obtained.

[0160] The warp and weft flat yarns obtained in each embodiment and comparative example were subjected to relevant performance tests, and the results are shown in Table 1.

[0161] The substrate fabrics for container bags prepared in each application example and the comparative application example were subjected to relevant performance tests, and the results are shown in Table 2.

[0162]

[0163]

[0164] As shown in Table 1, compared with Comparative Examples 1 to 2, the polyamide flat yarns obtained in Examples 1 to 8 of the present invention have higher breaking strength, indicating that the strength of the flat yarns in Examples 1 to 8 is significantly better than that in Comparative Examples 1 to 2. Therefore, by using polyamide as a raw material, the embodiments of the present invention can produce polyamide flat yarns with better breaking strength, which is more beneficial to the production of container bags.

[0165] Furthermore, compared to Comparative Examples 3 to 4, Examples 1 to 8 of the present invention optimize the preparation process of the flat yarn, thereby obtaining polyamide flat yarns with higher breaking strength.

[0166] Furthermore, according to the results in Table 2, compared with comparative examples 1 to 3, the polyamide bulk bags made from polyamide flat yarns in Examples 1 to 8 of the present invention have better tensile strength and dimensional stability, better wear resistance and can be recycled multiple times, and better heat resistance and low temperature resistance.

[0167] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0168] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A polyamide flat filament, characterized in that, Its raw materials include at least polyamide resin, which includes one or more of polyamide 5X, polyamide 6X, polyamide 6, polyamide 5T / 5X, polyamide 5T / 66, and polyamide 6T / 66, wherein X is selected from one or more of bisaccharide, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

2. The polyamide flat filament according to claim 1, characterized in that, The polyamide resin has a melting point of 180-310°C, further 200-300°C, and even further 220-290°C; and / or The polyamide resin has a relative viscosity of 2.4-3.8, more preferably 2.6-3.5, and even more preferably 2.8-3.3; and / or The polyamide resin has a terminal amino content of 10-70 mmol / kg, more preferably 20-60 mmol / kg, and even more preferably 30-50 mmol / kg; and / or, The water content of the polyamide resin is 300-1000 ppm, further 400-900 ppm, and even further 500-800 ppm.

3. The polyamide flat filament according to claim 1, characterized in that, The polyamide flat yarn includes polyamide warp flat yarn and polyamide weft flat yarn; wherein... The width of the polyamide warp flat filament is 1.0-3.0 mm, more preferably 1.2-2.5 mm, and even more preferably 1.4-2.3 mm; and / or, The thickness of the polyamide warp flat filament is 0.06-0.20 mm, more preferably 0.08-0.16 mm, and even more preferably 0.10-0.13 mm; and / or, The width of the polyamide weft flat filament is 1.0-3.0 mm, more specifically 1.3-2.6 mm, and even more specifically 1.6-2.3 mm; and / or, The thickness of the polyamide weft flat yarn is 0.06-0.30 mm, more specifically 0.08-0.25 mm, and even more specifically 0.10-0.20 mm; and / or, The tensile strength of the polyamide warp flat filament is ≥5.0 cN / dtex, further ≥5.5 cN / dtex, and even further ≥5.8 cN / dtex; and / or, The tensile strength of the polyamide weft flat yarn is ≥4.8 cN / dtex, further ≥5.2 cN / dtex, and even further ≥5.5 cN / dtex.

4. A method for preparing polyamide flat yarn according to any one of claims 1 to 3, characterized in that, The preparation method includes: 1) The polyamide resin is heated to a molten state to form a first polyamide melt and a second polyamide melt; 2) The first polyamide melt is accurately metered by the die head metering pump and extruded through the first spinneret of the spinning assembly to form the first nascent filament; the second polyamide melt is accurately metered by the die head metering pump and extruded through the second spinneret of the spinning assembly to form the second nascent filament. 3) The first and second nascent yarns are post-processed to obtain the polyamide warp flat yarn and the polyamide weft flat yarn.

5. The method for preparing polyamide flat yarn according to claim 4, characterized in that, In step 1), the heating is performed using a screw, which employs a four-zone heating system: zone one temperature is 180-290℃, preferably 200-280℃; zone two temperature is 200-300℃, preferably 220-290℃; zone three temperature is 220-320℃, preferably 240-310℃; and zone four temperature is 240-330℃, preferably 260-320℃; and / or, In step 2), the temperature of the machine head is 200-330℃, preferably 230-320℃; and / or, In step 2), the first spinneret and / or the second spinneret are circular or rectangular in shape; and / or, In step 2), the cross-section of the spinneret orifice of the first spinneret and / or the second spinneret is in the shape of a straight line; and / or, In step 2), the length of the spinneret orifice of the first spinneret is 8-15 mm, and the width is 0.3-0.6 mm; and / or, In step 2), the length of the spinneret orifice of the second spinneret is 7-15mm and the width is 0.3-0.75mm.

6. The method for preparing polyamide flat yarn according to claim 4, characterized in that, Step 3) of the post-processing includes: cooling the first and second nascent yarns, performing a first-stage water bath stretching, a second-stage hot air stretching, heat setting, and yarn separation and winding, respectively, to obtain the polyamide warp flat yarn and the polyamide weft flat yarn; wherein, The cooling is performed using a water bath, with the water bath temperature ranging from 10-50°C, and more specifically from 20-40°C; and / or, The stretching ratio of the first-stage water bath stretching is 2.0-4.0, more specifically 2.5-3.5; and / or, The stretching ratio of the secondary hot air stretching is 1.0-2.0, more specifically 1.2-1.8; and / or, The total stretch ratio is 3.0-6.5, more specifically 4.0-6.0; and / or, The temperature of the primary water bath stretching is 70-100℃, further 80-90℃; and / or, The temperature of the secondary hot air stretching is 100-200℃, further 120-180℃; and / or, The heat setting temperature is 160-240℃, more specifically 180-220℃; and / or, The winding speed is 40-300 m / min, and more specifically 60-200 m / min.

7. The application of the polyamide flat yarn according to any one of claims 1 to 3 or the polyamide flat yarn prepared by any one of claims 4 to 6 in polyamide bulk bags.

8. A polyamide container bag, comprising a polyamide container bag base fabric, said polyamide container bag base fabric being woven from polyamide flat yarns as described in any one of claims 1 to 3 or polyamide flat yarns prepared by any one of claims 4 to 6.

9. The polyamide container bag according to claim 8, characterized in that, The warp density of the polyamide container bag base fabric is 30-100 threads / 10cm, further 35-90 threads / 10cm, and even further 40-80 threads / 10cm; and / or The weft density of the polyamide container bag base fabric is 30-90 threads / 10cm, further 35-80 threads / 10cm, and even further 40-70 threads / 10cm; and / or The weight of the polyamide container bag base fabric is 100-400 g / m². 2 Further, it is 130-350g / m 2 Furthermore, it is 150-300g / m 2 ; and / or The longitudinal tensile strength of the polyamide container bag base fabric is ≥2200 N / 5 cm, further ≥2400 N / 5 cm, and even further ≥2700 N / 5 cm; and / or The polyamide container bag base fabric has a transverse tensile strength ≥2000N / 5cm, further ≥2200N / 5cm, and even further ≥2400N / 5cm; and / or The longitudinal elongation at break of the polyamide container bag base fabric is ≤45%, further ≤40%, and even further ≤35%; and / or The transverse elongation at break of the polyamide container bag base fabric is ≤50%, further ≤45%, and even further ≤40%; and / or The polyamide container bag base fabric has a heat resistance of ≥80℃, further ≥100℃, and even further ≥120℃; and / or The polyamide container bag base fabric has a cold resistance of ≤-10℃, further ≤-15℃, and even further ≤-20℃; and / or The abrasion resistance of the polyamide container bag base fabric is ≥4000 revolutions, further ≥6000 revolutions, and even further ≥8000 revolutions.

10. A method for preparing a polyamide container bag according to claim 8 or 9, characterized in that, The preparation method includes: weaving the polyamide flat yarn obtained by the preparation method of any one of claims 1 to 3 or any one of claims 4 to 6 into a base fabric using a weaving machine, cutting the base fabric, and then sewing it with the straps and reinforcing accessories to obtain the polyamide container bag.

11. A polyamide container bag, characterized in that, It includes polyamide warp flat yarn and polyamide weft flat yarn, wherein the tensile strength of the polyamide warp flat yarn is ≥5.0 CN / dtex and the tensile strength of the polyamide weft flat yarn is ≥4.8 cN / dtex.

12. The polyamide container bag according to claim 11, characterized in that, The tensile strength of the polyamide warp flat filament is ≥5.5 cN / dtex, more specifically ≥5.8 cN / dtex; and / or, The tensile strength of the polyamide weft flat yarn is ≥5.2 cN / dtex, more specifically ≥5.5 cN / dtex; and / or, The width of the polyamide warp flat filament is 1.0-3.0 mm, more preferably 1.2-2.5 mm, and even more preferably 1.4-2.3 mm; and / or, The thickness of the polyamide warp flat filament is 0.06-0.20 mm, more preferably 0.08-0.16 mm, and even more preferably 0.10-0.13 mm; and / or, The width of the polyamide weft flat filament is 1.0-3.0 mm, more specifically 1.3-2.6 mm, and even more specifically 1.6-2.3 mm; and / or, The thickness of the polyamide weft flat yarn is 0.06-0.30 mm, further 0.08-0.25 mm, and even further 0.10-0.20 mm.

13. The polyamide container bag according to claim 11 or 12, characterized in that, The raw materials for producing the polyamide warp flat yarn and / or the polyamide weft flat yarn include at least one or more polyamide resins selected from polyamide 5X, polyamide 6X, polyamide 6, polyamide 56 / 5T, and polyamide 66 / 6T, wherein X is selected from one or more of bisaccharide, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid; The polyamide resin has a melting point of 180-310°C, further 200-300°C, and even further 220-290°C; and / or, The relative viscosity of the polyamide resin is 2.4-3.8, more preferably 2.6-3.5, and even more preferably 2.8-3.3; and / or, The amino content of the polyamide resin is 10-70 mmol / kg, more preferably 20-60 mmol / kg, and even more preferably 30-50 mmol / kg; and / or, The water content of the polyamide resin is 300-1000 ppm, further 400-900 ppm, and even further 500-800 ppm.

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