POLYETHYLENE YARN OF HIGH TENACITY HAVING HIGH DIMENSIONAL STABILITY AND METHOD FOR MANUFACTURING THE SAME

Abstract

The present disclosure relates to a polyethylene yarn and a method for manufacturing the same. In the present disclosure, there are provided a polyethylene yarn having excellent dimensional stability and high tenacity, and a method for manufacturing the above polyethylene yarn more efficiently.

Claims

1. A polyethylene yarn comprising 40 to 500 filaments having fineness of 10 denier or less, wherein the polyethylene yarn has total fineness of 80 to 5000 denier, tenacity of 12 g/d or more, and a maximum thermal shrinkage stress of 0.325 g/d or less, and the filaments comprise a polyethylene having a weight average molecular weight (Mw) of 50,000 to 600,000 g/mol.

2. The polyethylene yarn of claim 1, wherein the polyethylene has a polydispersity index (PDI) of more than 5 and 9 or less.

3. The polyethylene yarn of claim 1, wherein the polyethylene has a melt index (MI) of 0.3 to 3 g/10 min.

4. The polyethylene yarn of claim 1, wherein the polyethylene has crystallinity of 65 to 85%.

5. The polyethylene yarn of claim 1, wherein the polyethylene has a melting temperature (T.sub.m) of 130 to 140° C.

6. The polyethylene yarn of claim 1, wherein the polyethylene has a density of 0.93 to 0.97 g/cm.sup.3.

7. The polyethylene yarn of claim 1, wherein the filaments further comprise at least one fluorine-based polymer selected from the group consisting of polytetrafluoroethylene (PTFE), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), an ethylene-tetrafluoroethylene copolymer (ETFE), a tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and ethylene-chlorotrifluoroethylene (ECTFE).

8. The polyethylene yarn of claim 7, wherein the fluorine-based polymer is contained in an amount such that 50 to 2500 ppm of fluorine is contained in the polyethylene yarn.

9. The polyethylene yarn of claim 1, wherein the polyethylene yarn has a crystallite size on a (110) plane of 120 Å or more and a crystallite size on a (200) plane of 90 Å or more, when measured using the Scherrer equation from XRD data.

10. A method for manufacturing a polyethylene yarn, comprising: (i) a preparation step of providing a melt for spinning containing a polyethylene having a weight average molecular weight (Mw) of 50,000 to 600,000 g/mol; (ii) a spinning step of obtaining filaments by extruding the melt through a spinneret having 40 to 500 holes; (iii) a quenching step of quenching the filaments; (iv) a drawing step of multi-stage drawing a multifilament composed of the quenched filaments at a total draw ratio of 11 to 23 times using a multi-stage drawing zone comprising a plurality of godet rollers set at a temperature of 40 to 140° C.; and (v) a take-up step of taking up the multi-stage drawn multifilament, wherein the multifilament is directly in contact with the plurality of godet rollers to be drawn and thermally fixed in the drawing step.

11. The method for manufacturing a polyethylene yarn of claim 10, wherein the polyethylene has a polydispersity index (PDI) of more than 5 and 9 or less.

12. The method for manufacturing a polyethylene yarn of claim 10, wherein the polyethylene has a melt index (MI) of 0.3 to 3 g/10 min.

13. The method for manufacturing a polyethylene yarn of claim 10, wherein the polyethylene has crystallinity of 65 to 85%.

14. The method for manufacturing a polyethylene yarn of claim 10, wherein the polyethylene has a melting temperature (T.sub.m) of 130 to 140° C.

15. The method for manufacturing a polyethylene yarn of claim 10, wherein the polyethylene has a density of 0.93 to 0.97 g/cm.sup.3.

16. The method for manufacturing a polyethylene yarn of claim 10, wherein the melt further comprises at least one fluorine-based polymer selected from the group consisting of polytetrafluoroethylene (PTFE), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), an ethylene-tetrafluoroethylene copolymer (ETFE), a tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and ethylene-chlorotrifluoroethylene (ECTFE).

17. The method for manufacturing a polyethylene yarn of claim 16, wherein the fluorine-based polymer is contained in an amount such that 50 to 2500 ppm of fluorine is contained in the polyethylene yarn.

18. The method for manufacturing a polyethylene yarn of claim 10, wherein the multi-stage drawing zone comprises 3 to 30 godet rollers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0147] FIG. 1 is a simplified process diagram showing the manufacturing process of a polyethylene yarn according to an embodiment of the present disclosure.

[0148] FIG. 2 schematically shows a thermal shrinkage stress tester.

[0149] FIG. 3 is a graph showing a change in thermal shrinkage stress with respect to temperature measured for the polyethylene yarn prepared in Example 3.

[0150] FIG. 4 is a graph showing a change in thermal shrinkage stress with respect to temperature measured for the polyethylene yarn prepared in Comparative Example 1.

[0151] FIG. 5 is a graph showing a comparison of changes in thermal shrinkage stress with respect to temperature between the polyethylene yarns obtained in Example 2 (-.square-solid.-indicated curve) and Comparative Example 3 (-.circle-solid.-indicated curve).

[0152]

TABLE-US-00001 [DESCRIPTION OF SYMBOLS] 100: Extruder 200: Spinneret 300: Quenching zone 11: Filament 10: Multifilament OR: Oil roller 400: Collecting zone 500: Multi-stage drawing zone GR1: First godet roller GRn: Last godet roller 600: Winder 700: Load cell 800: Hot chamber 900: Primary load hook 1000: Yarn sample

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0153] Hereinafter, the present invention will be described in more detail with the following preferred examples. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.

Example 1

[0154] A polyethylene yarn including 200 filaments was manufactured using the apparatus illustrated in FIG. 1, wherein the polyethylene yarn has total fineness of 400 denier.

[0155] Specifically, polyethylene chips having a weight average molecular weight (Mw) of 200,000 g/mol, a polydispersity index (Mw/Mn: PDI) of 7.5, a melt index (MI, @190° C.) of 0.4 g/10 min, a melting temperature (T.sub.m) of 132° C., and a density of 0.96 g/cm.sup.3 were added to an extruder (100). At the same time, a tetrafluoroethylene copolymer was added to the extruder (100) through a side feeder. The tetrafluoroethylene copolymer was added in an amount such that the amount of fluorine detected in the final yarn is 500 ppm. A melt for spinning was prepared by melting the chips introduced into the extruder (100).

[0156] The melt was extruded through a spinneret (200) having 200 holes.

[0157] The filaments (11) formed while being discharged from the spinneret (200) were finally quenched to 40° C. by cooling air at 0.45 m/s in the quenching zone (300). The quenched filaments (11) were collected by a collecting zone (400) into a multifilament (10) and continuously transferred to a multi-stage drawing zone (500) provided with 12 godet rollers (GR1-GR12). Continuously, the multifilament (10) in the multi-stage drawing zone (500) directly contacted the 12 godet rollers, and was drawn at a total draw ratio of 16 times, followed by heat-setting. The temperature range of the godet rollers was set to 80 to 130° C.

[0158] A polyethylene yarn was obtained by taking up the multi-stage drawn multifilament on a winder (600).

Example 2

[0159] A polyethylene yarn was obtained in the same manner as in Example 1, except that the temperature range of the godet rollers in the multi-stage drawing zone (500) was set to 60 to 120° C.

Example 3

[0160] A polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 170,000 g/mol, a polydispersity index (Mw/Mn: PDI) of 7.5, a melt index (MI, @190° C.) of 0.4 g/10 min, a melting temperature (T.sub.m) of 132° C., and a density of 0.96 g/cm.sup.3 were used.

Example 4

[0161] A polyethylene yarn was obtained in the same manner as in Example 1, except that the multifilament (10) in the multi-stage drawing zone (500) directly contacted the 12 godet rollers, and was drawn at a total draw ratio of 11 times, followed by heat-setting.

Example 5

[0162] A polyethylene yarn was obtained in the same manner as in Example 1, except that the multifilament (10) in the multi-stage drawing zone (500) directly contacted the 12 godet rollers, and was drawn at a total draw ratio of 23 times, followed by heat-setting.

Example 6

[0163] A polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 200,000 g/mol, a melt index (MI, @190° C.) of 0.4 g/10 min, and a polydispersity index (Mw/Mn: PDI) of 4.5 were used.

Comparative Example 1

[0164] A polyethylene yarn was manufactured in a two-step method including a take-up step of taking up an undrawn polyethylene yarn formed by melt spinning and a drawing step of drawing the undrawn yarn with a hot air oven without using the apparatus illustrated in FIG. 1.

[0165] Specifically, polyethylene chips having a weight average molecular weight (Mw) of 200,000 g/mol, a melt index (MI, @190° C.) of 0.4 g/10 min, and a polydispersity index (Mw/Mn: PDI) of 4.5 were added to an extruder. At the same time, a tetrafluoroethylene copolymer was added to the extruder (100) through a side feeder. The tetrafluoroethylene copolymer was added in an amount such that the amount of fluorine detected in the final yarn is 500 ppm. A melt for spinning was prepared by melting the chips introduced into the extruder.

[0166] The melt was extruded through a spinneret (200) having 200 holes.

[0167] The filaments formed while being discharged from the spinneret were finally quenched to 40° C. by cooling air at 0.45 m/s in the quenching zone. The quenched filaments were collected by a collecting zone into a multifilament and taken up on a winder.

[0168] After moving the winder on which the multifilament was taken up to the place where a drawing machine was located, the multifilament taken up on the winder was drawn at a total draw ratio of 16 times, followed by heat-setting while heating with hot air of 80 to 130° C.

[0169] A polyethylene yarn having total fineness of 420 denier was obtained by taking up the drawn multifilament on a winder.

Comparative Example 2

[0170] A polyethylene yarn was obtained in the same manner as in Example 1, except that the temperature range of the godet rollers in the multi-stage drawing zone (500) was set to 60 to 150° C.

Comparative Example 3

[0171] A polyethylene yarn was obtained in the same manner as in Comparative Example 1 (that is, drawing and heat-setting using a hot air oven at 80 to 130° C.), except that polyethylene chips having a weight average molecular weight (Mw) of 200,000 g/mol, a polydispersity index (Mw/Mn: PDI) of 7.5, a melt index (MI, @190° C.) of 0.4 g/10 min, a melting temperature (T.sub.m) of 132° C., and a density of 0.96 g/cm.sup.3 were used.

Comparative Example 4

[0172] A polyethylene yarn was obtained in the same manner as in Example 1, except that the multifilament (10) in the multi-stage drawing zone (500) directly contacted the 12 godet rollers, and was drawn at a total draw ratio of 6 times, followed by heat-setting.

Comparative Example 5

[0173] A polyethylene yarn was obtained in the same manner as in Example 1, except that the multifilament (10) in the multi-stage drawing zone (500) directly contacted the 12 godet rollers, and was drawn at a total draw ratio of 25 times, followed by heat-setting.

Test Examples

[0174] Each of the polyethylene yarns prepared in examples and comparative examples was tested by the following method, and the results are shown in Tables 1 to 4 below.

[0175] (1) Tenacity of Polyethylene Yarn (g/d)

[0176] According to the standard test method of ASTM D885, the tenacity (g/d) of the polyethylene yarn was measured using a universal tensile tester manufactured by Instron Engineering Corp (Canton, Mass.). The sample was 250 mm long, a tensile velocity was 300 mm/min, and an initial load was set to 0.05 g/d.

[0177] (2) Mw, Mn, PDI

[0178] After completely dissolving filaments constituting the polyethylene yarn in the following solvent, a weight average molecular weight (Mw), a number average molecular weight (Mn), and a polydispersity index (Mw/Mn: PDI) were measured by gel permeation chromatography (GPC). [0179] Analyzer: PL-GPC 220 system [0180] Column: 2×PLGEL MIXED-B (7.5×300 mm) [0181] Column temperature: 160° C. [0182] Solvent: Trichlorobenzene (TCB)+0.04 wt % dibutylhydroxytoluene (BHT, after drying with 0.1% CaCl.sub.2) [0183] Dissolution conditions: 160° C., 1˜4 hours, measuring the solution passed through a glass filter (0.7 ) after dissolution [0184] Temperature of injector, detector: 160° C. [0185] Detector: RI Detector [0186] Flow rate: 1.0 /min [0187] Injection volume: 200 [0188] Standard sample: Polystyrene

[0189] (3) Crystallinity and Crystallite Size of Polyethylene Yarn

[0190] The crystallinity and the crystallite size on the (110) plane and the (200) plane of the polyethylene yarn were measured by an X-ray diffractometer using X-rays. Specifically, the polyethylene yarn was cut to prepare a 2.5 cm sample, and the sample was fixed on a sample holder of the X-ray diffractometer, followed by measurement under the following conditions. When analyzing crystallinity by an X-ray diffractometer, the crystallinity (%) and the crystallite size (Å) are simultaneously derived.

[0191] i) Experimental equipment: Empyrean (Malvern Panalytical Ltd)

[0192] ii) X-ray source: Cu-Kα (1.54 Å), 45 kV, 20 mA

[0193] iii) Incident beam path [0194] Filter: Beta-filter Nickel 0.02 mm [0195] Slit: AS 1°, DS 1/2°, SS: 0.04 rad [0196] Mask: 10 mm

[0197] iv) Diffracted beam path [0198] Detector: PIXcel3D 2×2 (area detector) [0199] Slit: AS 5.0 mm, SS: 0.04 rad

[0200] v) Scan range: 10°˜32°

[0201] vi) Step size: 0.1°

[0202] vii) Beam direction: Reflection

[0203] viii) Background Method: Constant Background

[0204] ix) Standard Specimen: 3000 Denier

[0205] x) Apparent crystallite size (ACS): estimated from the half-height of the peak (110) plane and (200) plane using the Scherrer equation.

[00001]$D=\frac{0.89\lambda }{\beta \cos \theta }$ [0206] λ: X-ray wavelength, 0.154 nm [0207] β: FWHM [0208] Θ: Bragg angle (max. peak) [0209] Scherrer constant K=0.89

[0210] xi) Crystallinity (Xc): Constant background method

[0211] (4) Maximum Thermal Shrinkage Stress of Polyethylene Yarn (g/d)

[0212] The maximum thermal shrinkage stress of the polyethylene yarn was measured using a thermal shrinkage stress tester (KANEBO KE-2, Shinkoh, DAS-4007 type, KANEBO Engineering, Korean agent: Eiko).

[0213] As illustrated in FIG. 2, both ends of the polyethylene yarn were knotted to make a loop-shaped sample (1000) having a circumference of 10 cm. Both sides of the sample were placed in a hot chamber (800) of the thermal stress tester, and then hung on a load cell (700) and a primary load hook (900), respectively. The maximum thermal shrinkage stress was measured under the following conditions. [0214] Experimental equipment: KE-2 (Kanebo Engineering Co., Ltd.) [0215] Load cell: A load cell capable of measuring up to 500 gf [0216] Initial temperature: Room temperature [0217] Heating rate: 300° C./120 s [0218] Primary load: 0.06667 g/d

[0219] The measurement result of the thermal shrinkage stress was obtained as a graph by an output device (Type 3086 X-T Recorder, Yokogawa, Hokushin Electric, Tokyo, Japan).

[0220] FIG. 3 is a graph showing a result of the experiment performed on the polyethylene yarn of Example 3, and it was confirmed that the maximum thermal shrinkage stress was about 115 g at about 150° C.

[0221] FIG. 4 is a graph showing a result of the experiment performed on the polyethylene yarn of Comparative Example 1, and it was confirmed that the maximum thermal shrinkage stress was about 145 g at about 150° C.

[0222] FIG. 5 is a graph showing a comparison of changes in thermal shrinkage stress with respect to temperature between the polyethylene yarns obtained in Example 2 (-.square-solid.-indicated curve) and Comparative Example 3 (-.circle-solid.-indicated curve).

TABLE-US-00002 TABLE 1 Example 1 Example 2 Example 3 PE PDI 7.5 7.5 7.5 chip Mw (g/mol) 200,000 200,000 170,000 Total draw ratio (times) 16 16 16 Temperature range of godet 80-130 60-120 80-130 rollers (° C.) PE PDI 5.6 5.6 5.6 yarn Tenacity (g/d) 14.5 14.1 13.1 Crystallinity (%) 80 79 77 Crystallite (110) plane 161 165 183 size (Å) (200) plane 103 112 131 Max. thermal shrinkage stress (g/d) 0.270 0.300 0.315

TABLE-US-00003 TABLE 2 Example 4 Example 5 Example 6 PE PDI 7.5 7.5 4.5 chip Mw (g/mol) 200,000 200,000 200,000 Total draw ratio (times) 11 23 16 Temperature range of godet 80-130 80-130 80-130 rollers (° C.) PE PDI 5.6 5.6 3 yarn Tenacity (g/d) 12.5 16.3 16.3 Crystallinity (%) 75 82 80 Crystallite (110) plane 173 145 150 size (Å) (200) plane 125 95 99 Max. thermal shrinkage stress (g/d) 0.325 0.250 0.265

TABLE-US-00004 TABLE 3 Comp. Comp. Comp. Example 1 Example 2 Example 3 PE PDI 4.5 7.5 7.5 chip Mw (g/mol) 200,000 200,000 200,000 Total draw ratio (times) 16 16 16 Temperature range of godet (hot air oven) 60-150 (hot air oven) rollers (° C.) 80-130 80-130 PE PDI 3 PE yarn could 5.6 yarn Tenacity (g/d) 16 not be 13.8 Crystallinity (%) 78 manufactured 77 Crystallite (110) plane 155 due to 167 size (Å) (200) plane 97 breakage 106 Max. thermal shrinkage stress (g/d) 0.510 during drawing 0.525

TABLE-US-00005 TABLE 4 Comp. Comp. Example 4 Example 5 PE PDI 7.5 7.5 chip Mw (g/mol) 200,000 200,000 Total draw ratio (times) 6 25 Temperature range of godet 80-130 80-130 rollers (° C.) PE PDI 5.6 PE yarn could yarn Tenacity (g/d) 11.8 not be Crystallinity (%) 30 manufactured Crystallite (110) plane 200 due to size (Å) (200) plane 143 breakage Max. thermal shrinkage stress (g/d) 0.345 during drawing

[0223] Referring to Tables 1 and 2, it was confirmed that the polyethylene yarns according to the examples had high tenacity compared to the polyethylene yarns according to the comparative examples, and low maximum thermal shrinkage stress, thereby exhibiting excellent dimensional stability. In addition, the polyethylene yarn could be obtained more efficiently without uneven discharge during spinning in the manufacturing method of the examples compared to the manufacturing method of the comparative examples.