High-strength polyethylene fiber melt spinning method

Abstract

The invention discloses a melt spinning method of high-strength polyethylene fiber, which comprises the following steps: drying a polyethylene raw material, adding into a screw extruder for melting, extruding through a filter, a metering pump and a spinneret plate to form a melt trickle, and oiling after the extruded melt trickle passes through a slow cooling area and is cooled by air to obtain the high-strength polyethylene fiber. After the protofilament is subjected to multiple times of drafting, the protofilament is wound into the high-strength polyethylene fiber. The prepared high-strength polyethylene fiber can be used for manufacturing anti-cutting gloves, cool fabrics, fishing nets, mooring ropes, wall cloth and the like.

Description

Technical Field

[0001] The invention relates to a melt spinning process for high-strength polyethylene fibers. Background Art

[0002] High-strength polyethylene fibers are typically produced via two different processes: dry gel spinning and wet gel spinning. Both methods require using a solvent to dissolve the raw materials, which are then ejected through a spinneret to form a precursor. The solvent is then removed from the precursor, and the fibers are then drawn to produce high-strength polyethylene fibers. Both methods are not only complex and costly, but also require the use of substances such as decalin and white oil, which can be very polluting to the environment.

[0003] The melt-spinning method for producing high-strength polyethylene fibers generally involves first pelletizing the polyethylene pellets through a twin-screw extruder. The polyethylene pellets are then melt-extruded through a single-screw extruder to form filaments, which are then stretched into polyethylene fibers. The twin-screw extruders used for pelletization generally have strong shear forces, a long melting range, and high processing temperatures. During processing, the polyethylene can degrade and cross-link, destroying its macromolecular structure. Therefore, while the process is relatively simple compared to gel spinning, its spinnability is poor, the spinning speed is extremely low, and it is not suitable for mass production.

[0004] Patents CN202211455932.6, CN202111254228.X, CN202011343381.5, CN202210829038.4, etc. all use gel spinning methods, which have disadvantages such as long production process, serious environmental pollution, and high production costs.

[0005] Patents CN202010589094.6, CN201810450839.3, CN202010587397.4, etc. have announced methods for preparing medium and high strength polyethylene fibers. They all use a twin-screw extruder for granulation modification and then melt spinning. This processing process is longer than the conventional melt spinning process and will cause serious damage to the polyethylene macromolecular chain, resulting in reduced performance.

[0006] The method of preparing high-strength polyethylene fibers using conventional melt spinning has always been a market gap. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for producing high-strength polyethylene fibers that is safe, environmentally friendly, has low production costs, and has an extremely short process.

[0008] The objects of the present invention are achieved by the following means.

[0009] Polyethylene with a viscosity-average molecular weight of ≤500,000 and a molecular weight distribution of ≤8 is used as raw material. After being melted at a temperature of 200-350°C in a screw extruder, it is filtered through a 10-500 mesh filter, passed through a spinneret, stayed in the spinneret hole for more than 0.05s, and extruded at a speed of 0.5-5m / min to form a melt stream. It is slowly cooled at a temperature of 80-350°C, and then forced to cool with wind at a temperature of 16-30°C, a humidity of 40-80%, and a pressure of 50-200Pa. After being oiled, it is wound onto a winder at a speed of 50-1000m / min to form a raw yarn.

[0010] The raw yarn undergoes three or four drawing passes: the first drawing temperature is 20-100°C, the drawing heating time is greater than 30s, and the drawing ratio is 1.05-10.0 times; the second drawing pass: the drawing temperature is 70-130°C, the drawing heating time is greater than 3s, and the drawing ratio is 1.10-8.0 times; the third drawing pass: the drawing temperature is 70-130°C, the drawing heating time is greater than 1s, and the drawing ratio is 0.80-3.00 times; the fourth drawing pass: the drawing temperature is 70-130°C, the drawing heating time is greater than 1s, and the drawing ratio is 0.80-3.00 times, and then it is wound onto a winder to make high-strength polyethylene fiber.

[0011] Compared with the prior art, the production method of the high-strength polyethylene fiber of the present invention is safe and environmentally friendly, has a simple process flow and low cost, and the prepared polyethylene fiber has good performance. DETAILED DESCRIPTION

[0012] The present invention will be further described in detail below with reference to the embodiments.

[0013] Example 1

[0014] Polyethylene with a viscosity-average molecular weight of 145,000 and a molecular weight distribution of 6.2 is used as raw material, dried at 80°C for 18 hours, melted at 290°C in a screw extruder, filtered through a 20-mesh filter, passed through a spinneret, stayed in the spinneret hole for 0.25s, and extruded at a speed of 0.8m / min to form a melt stream, which was slowly cooled at a temperature of 265°C, and then forced cooled using wind with a wind temperature of 25°C, a humidity of 60%, and a wind pressure of 120Pa. After oiling, it was wound onto a winder at a speed of 130m / min to form a raw yarn.

[0015] The raw yarn undergoes three stretching stages: the first stretching temperature is 30°C, the stretching heating time is 90s, and the stretching ratio is 2.5 times; the second stretching stage is 90°C, the stretching heating time is 36s, and the stretching ratio is 3.9 times; the third stretching stage is 105°C, the stretching heating time is 8.5s, and the stretching ratio is 0.97 times. It is then wound onto a winder to produce high-strength polyethylene fiber with a breaking strength of 10.73cN / dtex and an elongation at break of 10.37%.

[0016] Example 2

[0017] Polyethylene with a viscosity-average molecular weight of 145,000 and a molecular weight distribution of 6.2 is used as raw material, dried at 100°C for 12 hours, melted at 290°C in a screw extruder, filtered through a 200-mesh filter, passed through a spinneret, stayed in the spinneret hole for 0.25s, and extruded at a speed of 0.8m / min to form a melt stream, slowly cooled at a temperature of 150°C, and then forced cooled using wind with a wind temperature of 22°C, a humidity of 68%, and a wind pressure of 85Pa. After oiling, it is wound onto a winder at a speed of 170m / min to form a raw yarn.

[0018] The raw yarn undergoes three drawing stages: the first drawing temperature is 78°C, the drawing heating time is 80s, and the drawing ratio is 7 times; the second drawing stage is 100°C, the drawing heating time is 11s, and the drawing ratio is 1.6 times; the third drawing stage is 105°C, the drawing heating time is 6.8s, and the drawing ratio is 0.99 times. It is then wound onto a winder to produce high-strength polyethylene fiber with a breaking strength of 11.68cN / dtex and an elongation at break of 7.80%.

[0019] Example 3

[0020] Polyethylene with a viscosity-average molecular weight of 120,000 and a molecular weight distribution of 4.5 is used as raw material, dried at 110°C for 12 hours, melted at 270°C in a screw extruder, filtered through a 400-mesh filter, passed through a spinneret, stayed in the spinneret hole for 0.12s, and extruded at a speed of 1.2m / min to form a melt stream, slowly cooled at a temperature of 150°C, and then forced cooled using wind with a wind temperature of 22°C, a humidity of 70%, and a wind pressure of 80Pa. After oiling, it is wound onto a winder at a speed of 300m / min to form a raw yarn.

[0021] The raw yarn undergoes four stretching steps: the first stretching temperature is 15°C, the stretching heating time is 82s, and the stretching ratio is 1.07 times; the second stretching step is 80°C, the stretching heating time is 80s, and the stretching ratio is 6.5 times; the third stretching step is 100°C, the stretching heating time is 12.5s, and the stretching ratio is 1.5 times; the fourth stretching step is 110°C, the stretching heating time is 13s, and the stretching ratio is 0.985 times. It is then wound onto a winder to produce high-strength polyethylene fiber with a breaking strength of 13.65cN / dtex and an elongation at break of 5.62%.

[0022] Example 4

[0023] Polyethylene with a viscosity-average molecular weight of 120,000 and a molecular weight distribution of 4.5 is used as raw material. It is dried at 120°C for 10 hours, melted at 270°C in a screw extruder, filtered through a 400-mesh filter, passed through a spinneret, stayed in the spinneret hole for 0.1s, and extruded at a speed of 1.2m / min to form a melt stream. It is slowly cooled at a temperature of 150°C, and then forced to cool with wind at a temperature of 19°C, a humidity of 70%, and a pressure of 85Pa. After oiling, it is wound onto a winder at a speed of 300m / min to form a raw yarn.

[0024] The raw yarn undergoes three drawing stages: the first drawing temperature is 15°C, the drawing heating time is 90s, and the drawing ratio is 2.5 times; the second drawing stage is 85°C, the drawing heating time is 36s, and the drawing ratio is 3.0 times; the third drawing stage is 110°C, the drawing heating time is 12s, and the drawing ratio is 1.7 times. It is then wound onto a winder to produce high-strength polyethylene fiber with a breaking strength of 14.80cN / dtex and an elongation at break of 5.50%.

Claims

1. A method for melt-spinning high-strength polyethylene fibers, the process comprising drying the polyethylene raw material, then adding it to a screw extruder for melting, and then extruding it through a filter, a metering pump, and a spinneret to form a melt stream. The extruded melt stream is cooled by air and then oiled, and then wound into a precursor. The precursor is subjected to multiple drafting steps and then wound into a high-strength polyethylene fiber.

2. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The polyethylene raw material is granular or powder, with a viscosity-average molecular weight ≤ 500,000 and a molecular weight distribution index ≤ 8.

0.

3. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The drying temperature is 60 to 140°C, and the drying time is 10 to 48 hours.

4. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The melt spinning temperature is 200-350°C.

5. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The filter mesh size is 10 to 500 meshes.

6. The high-strength polyethylene fiber melt-spinning method according to claim 1, characterized in that: The temperature in the slow cooling zone is 80-350°C.

7. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The residence time of the melt in the spinneret is greater than 0.05s, and the speed of extrusion from the spinneret is 0.5-5m / min.

8. The high-strength polyethylene fiber melt-spinning method according to claim 1, characterized in that: The wind is air or nitrogen, the wind temperature is 16-30℃, the humidity is 40-80%, the wind pressure is 50-200Pa, and the height of the wind cooling zone is 50-200cm.

9. The method for melt-spinning high-strength polyethylene fibers according to claim 1, wherein: The yarn winding speed is 50 to 1000 m / min.

10. The method for melt-spinning high-strength polyethylene fibers according to claim 1, characterized in that: The drawing process is three-pass or four-pass drawing, with the temperature of one-pass drawing being 20-100°C, the drawing heating time being greater than 30s, and the drawing ratio being 1.05-10.0 times; the temperature of two-pass drawing being 70-130°C, the drawing heating time being greater than 3s, and the drawing ratio being 1.10-8.0 times; the temperature of three-pass drawing being 70-130°C, the drawing heating time being greater than 1s, and the drawing ratio being 0.80-3.00 times; the temperature of four-pass drawing being 70-130°C, the drawing heating time being greater than 1s, and the drawing ratio being 0.80-3.00 times.