Method for preparing medium-high strength polyethylene precursor through plunger type melt spinning

Abstract

The invention discloses a method for preparing medium-high strength polyethylene protofilaments by plunger type melt spinning, which comprises the following steps: a, adding a polyethylene raw material into a plunger extruder through a stock bin 4 for melting, and closing a valve 5; b, opening a valve 3, closing a valve 7, and inputting nitrogen with a certain pressure into the plunger extruder; c, extruding the polyethylene melt into a component 10 by nitrogen, filtering the polyethylene melt by a filter screen, and extruding the polyethylene melt into melt trickles through spinneret orifices; and d, cooling the melt trickle, and winding the cooled melt trickle on a winding machine 11 to form the polyethylene precursor. In the melt spinning process, the melting range is extremely short, the spinning temperature is low, the melt is not subjected to shear force in the whole process, entanglement and degradation of polyethylene macromolecular chain segments can be effectively avoided, and the formed protofilaments are uniform in structure and stable and excellent in performance.

Description

Technical Field

[0001] The invention relates to a melt spinning process for medium- and high-strength polyethylene precursor filaments. Background Art

[0002] Polyethylene fibers can be divided into high-strength polyethylene fibers and low-strength polyethylene fibers. The breaking strength of high-strength polyethylene fibers is generally ≥25cN / dtex, while the breaking strength of low-strength polyethylene fibers is generally ≤8cN / dtex, or even lower.

[0003] There are two different process routes for high-strength polyethylene fiber: dry gel spinning and wet gel spinning. Both methods require the use of solvents to dissolve the raw materials, which are then ejected through spinnerets to form raw fibers, and then the solvent in the raw fibers is removed, and finally drawn to prepare high-strength polyethylene fibers. Both methods are not only complex and costly, but also require the use of decahydronaphthalene, white oil and other substances, which will cause great pollution to the environment.

[0004] Low-strength polyethylene fiber uses a melt spinning method, first granulated by a twin-screw extruder, then the polyethylene pellets are melted and extruded through a single-screw extruder to make raw yarns, and then stretched into polyethylene fibers. The twin-screw extruder used for granulation generally has a strong shear force, and the screw extruder has a long melting range and a high processing temperature (generally 300-320°C). During the processing, polyethylene will be degraded and cross-linked, destroying the macromolecular structure. Therefore, although its process is relatively simple compared to gel spinning, the strength of the prepared fiber is relatively low.

[0005] 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 cost.

[0006] Patents CN202010589094.6, CN201810450839.3, CN202010587397.4, etc. have announced methods for preparing medium and high strength polyethylene fibers, all of which 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 chains, resulting in reduced performance.

[0007] There has been a gap in the market for medium and high strength polyethylene fibers, and the preparation of polyethylene precursors with excellent performance is the basis for the preparation of medium and high strength polyethylene fibers. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for producing medium- and high-strength polyethylene precursors which is safe, environmentally friendly, has low production costs, has an extremely short process, and does not cause any damage to polyethylene macromolecular chain segments.

[0009] The object of the present invention is achieved by the following means.

[0010] Polyethylene with a melt index of 0.1 to 10 g / 10 min is used as a raw material, melted at a temperature of 80 to 280° C. in a plunger extruder, extruded into a spinneret assembly by nitrogen with a purity of 99.999% and a pressure of 1.0 to 4.0 MPa, filtered through a 50 / 100 / 200 mesh filter, and finally extruded through a spinneret hole with a pore size of 0.5 mm and an aspect ratio of 2, cooled, and wound onto a winder at a speed of 20 to 100 m / min to obtain medium- and high-strength polyethylene precursor yarns. The obtained medium- and high-strength polyethylene precursor yarns can be used to produce medium- and high-strength polyethylene fibers.

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

[0012] The following is a brief description of the contents expressed in the drawings of the invention and the marks in the drawings:

[0013] Figure 1 This is a schematic diagram of a plunger-type melt spinning device, with the markings in the figure as follows: 1. nitrogen inlet pipe; 2. pressure regulating valve; 3. valve; 4. silo; 5. valve; 6. nitrogen outlet pipe; 7. valve; 8. temperature sensor; 9. plunger extruder; 10. assembly; 11. winder. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below in conjunction with embodiments.

[0015] Example 1

[0016] Polyethylene resin particles with a melt index of 1.1g / 10min were selected, heated and melted by a plunger extruder (the temperatures of the three zones were 120°C, 200°C, and 225°C, respectively), extruded into the component by nitrogen at a pressure of 1.88MPa, filtered through a 50 / 100 / 200 mesh filter, and then sprayed out through a spinneret with a pore size of 0.5mm and an aspect ratio of 2. Finally, the winder was wound into raw yarn at a speed of 42m / min, and the obtained raw yarn had a linear density of 14.5dtex, a breaking strength of 1.75cN / dtex, and an elongation at break of 485%.

[0017] Example 2

[0018] Polyethylene resin particles with a melt index of 0.6g / 10min were selected, heated and melted by a plunger extruder (the temperatures of the three zones were 120°C, 230°C, and 250°C, respectively), extruded into the component by nitrogen at a pressure of 2.00MPa, filtered through a 50 / 100 / 200 mesh filter, and then sprayed out through a spinneret with a pore size of 0.5mm and an aspect ratio of 2. Finally, the winder was wound into raw yarn at a speed of 42m / min, and the obtained raw yarn had a linear density of 16.1dtex, a breaking strength of 1.67cN / dtex, and an elongation at break of 445%.

[0019] Example 3

[0020] Polyethylene resin particles with a melt index of 0.9g / 10min were selected, heated and melted by a plunger extruder (the temperatures of the three zones were 120°C, 200°C, and 220°C, respectively), extruded into the component by nitrogen at a pressure of 1.90MPa, filtered through a 50 / 100 / 200 mesh filter, and then sprayed out through a spinneret with a pore size of 0.5mm and an aspect ratio of 2. Finally, the winder was wound into raw yarn at a speed of 40m / min, and the obtained raw yarn had a linear density of 18.3dtex, a breaking strength of 1.41cN / dtex, and an elongation at break of 424%.

[0021] Example 4

[0022] Polyethylene resin particles with a melt index of 0.6g / 10min were selected, heated and melted by a plunger extruder (the temperatures of the three zones were 120°C, 200°C, and 220°C, respectively), extruded into the component by nitrogen at a pressure of 1.85MPa, filtered through a 50 / 100 / 200 mesh filter, and then sprayed out through a spinneret with a pore size of 0.5mm and an aspect ratio of 2. Finally, the winder was wound into raw yarn at a speed of 45m / min, and the obtained raw yarn had a linear density of 12.7dtex, a breaking strength of 1.82cN / dtex, and an elongation at break of 418%.

Claims

1. A method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning, the process comprising: a. Add the polyethylene raw material into the plunger extruder through the silo 4 to melt, and close the valve 5; b. Open the valve 3, close the valve 7, and input a certain pressure of nitrogen into the plunger extruder; c. The nitrogen extrude the polyethylene melt into the component 10, and after being filtered through the filter screen, it is extruded into a melt stream through the spinneret hole; d. After cooling, the melt stream is wound onto the winder 11 to form polyethylene filaments.

2. A method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The polyethylene raw material is powder or granular material, and the melt index is 0.1-10g / 10min.

3. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The plunger extruder is vertical, and the heating is divided into three zones, with the temperature of each zone ranging from 80 to 280°C.

4. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The purity of the nitrogen is 99.999%, and the pressure is 1.0-4.0 MPa.

5. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The filter screen is a three-layer composite, with each layer having 50 mesh, 100 mesh and 200 mesh respectively.

6. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The spinneret hole has a diameter of 0.5 mm and an aspect ratio of 2.

7. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The winding speed is 20 to 100 m / min.

8. The method for preparing medium- and high-strength polyethylene precursor by plunger-type melt spinning according to claim 1, characterized in that: The obtained medium-high strength polyethylene raw yarn has a single yarn density of 8-30 dtex, a breaking strength of ≥1 cN / dtex, and a breaking elongation of ≥300%.

Images