Polyethylene yarn with excellent thermal properties and its manufacturing method

Abstract

TECHNICAL FIELD The present invention relates to a polyethylene raw yarn and a method for producing the same. BACKGROUND OF THE INVENTION The present invention provides a polyethylene raw yarn having excellent thermal properties and a method for more efficiently producing the polyethylene raw yarn.

Description

[Technical Field]

[0001] The present invention relates to polyethylene yarn and a method for producing the same. [Background technology]

[0002] High-strength polyethylene yarns can be classified into ultra-high molecular weight polyethylene (UHMWPE) yarns and high molecular weight polyethylene (HMWPE) yarns.

[0003] The UHMWPE generally refers to linear polyethylene having a weight average molecular weight (Mw) of more than 600,000 g / mol, and the HMWPE generally refers to linear polyethylene having a weight average molecular weight (Mw) of 20,000 to 600,000 g / mol.

[0004] It is known that due to its high melt viscosity, the UHMWPE yarn can only be produced by gel spinning.

[0005] For example, a UHMWPE solution can be produced by polymerizing ethylene in an organic solvent in the presence of a catalyst, spinning the solution and cooling it to form a fibrous gel, and then stretching the fibrous gel to obtain a high-strength, high-modulus polyethylene yarn. However, this gel-spinning method requires the use of an organic solvent, which not only poses environmental problems but also requires significant costs for recovering the organic solvent.

[0006] HMWPE has a relatively low melt viscosity compared to UHMWPE, making it possible to produce yarn by melt spinning. However, HMWPE has a limitation in that the strength of the yarn is inevitably low due to its relatively low molecular weight.

[0007] In addition, polyethylene yarn has lower thermal properties (e.g., melting point) than yarns made from materials such as polyethylene terephthalate and polyamide, which can lead to a problem that the physical properties of the polyethylene yarn deteriorate during post-processing steps (e.g., dyeing, coating, curing, etc.) required to apply the polyethylene yarn to various applications. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides polyethylene yarns with excellent thermal properties.

[0009] The present invention also provides a method for efficiently producing the polyethylene yarn. [Means for solving the problem]

[0010] According to one embodiment of the invention, there is provided a polyethylene yarn that satisfies the following formula 1:

[0011] <Expression 1> 0.05≦[(AB) / A]≦0.35

[0012] In the above formula 1, A is the heat of fusion (ΔH f , J / g), B is the value of the heat of fusion (ΔH f , J / g).

[0013] And, according to another embodiment of the invention, providing a melt comprising polyethylene having a weight average molecular weight (Mw) of 50,000 g / mol to 600,000 g / mol and a melt index (190°C, 2.16 kgf load) of 0.3 g / 10 min to 5.0 g / 10 min; extruding the melt through a die to obtain a filament; allowing the filament to cool; drawing a multifilament formed from the cooled filaments; and winding the drawn multifilament, The cooling is performed in a cooling unit having a plurality of cooling zones divided by zone temperatures, and the plurality of cooling zones are set to have a temperature gradient that gradually decreases in a direction from an inlet of the filament to an outlet of the filament. A method for producing the polyethylene yarn is provided.

[0014] Hereinafter, polyethylene yarn and a method for producing the same according to an embodiment of the present invention will be described in more detail.

[0015] Unless expressly stated otherwise herein, terminology is for the purpose of referring to particular embodiments only and is not intended to be limiting of the invention.

[0016] As used herein, the singular forms "a," "an," and "the" include the plural forms as well, unless the context clearly dictates to the contrary.

[0017] As used herein, the meaning of "comprising" embodies certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other certain properties, regions, integers, steps, operations, elements, components, and / or groups.

[0018] As a result of research by the present inventors, it has been confirmed that when the heat of fusion value of polyethylene raw yarn measured by differential scanning calorimetry satisfies the ratio range according to the present invention, it can exhibit excellent thermal properties in post-processing processes such as dyeing, coating, and curing.

[0019] According to one embodiment of the invention, there is provided a polyethylene yarn that satisfies the following formula 1:

[0020] <Expression 1> 0.05≦[(AB) / A]≦0.35

[0021] In the above formula 1, A is the heat of fusion (ΔH f , J / g).

[0022] In the above formula 1, B is the value of the heat of fusion (ΔH f , J / g).

[0023] In the differential scanning calorimetry, the first temperature rise (1st run) is measured while increasing the temperature of the polyethylene yarn at a constant rate. In the first temperature rise, a peak due to the thermal history of the polyethylene yarn is observed.

[0024] After the polyethylene fiber is completely melted in the first heating run, it is cooled and then the temperature is increased again at a constant rate for the second heating run (2nd run). During the second heating run, peaks due to the inherent properties of the sample are observed.

[0025] The above formula 1 is the range of the ratio calculated from the value of the heat of fusion in the first heating (A) and the value of the heat of fusion in the second heating (B) for the polyethylene raw yarn.

[0026] According to one embodiment, the polyethylene yarn preferably has a ratio of heat of fusion values ​​([(AB) / A]) according to the above formula 1 of 0.05 to 0.35.

[0027] Specifically, the polyethylene yarn may have a ratio of the heat of fusion values ​​according to the above formula 1 of 0.05 or more, alternatively 0.10 or more, alternatively 0.15 or more; and 0.35 or less, alternatively 0.30 or less, alternatively 0.26 or less.

[0028] In order to achieve excellent thermal properties according to the present invention, the polyethylene yarn preferably has a ratio of the heat of fusion values ​​according to Equation 1 of 0.05 or more, or 0.10 or more, or 0.15 or more. However, if the ratio of the heat of fusion values ​​is too high, the mechanical properties of the yarn may be reduced, such as yarn breakage during drawing. Therefore, the polyethylene yarn preferably has a ratio of the heat of fusion values ​​according to Equation 1 of 0.35 or less, or 0.30 or less, or 0.26 or less.

[0029] Preferably, the polyethylene raw yarn may have a ratio of the heat of fusion values ​​according to the above formula 1 of 0.05 to 0.35, alternatively 0.10 to 0.35, alternatively 0.10 to 0.30, alternatively 0.15 to 0.30, or alternatively 0.15 to 0.26.

[0030] As a non-limiting example, the first temperature increase and the second temperature increase may be performed in succession under the following conditions using a conventional differential scanning calorimeter.

[0031] For polyethylene raw yarn samples, the temperature was increased from 50°C to 180°C at 10°C / min (first heating); held at 180°C for 1 to 5 minutes; cooled from 180°C to 50°C at 200°C / min; held at 50°C for 1 to 5 minutes; heated from 50°C to 180°C at 10°C / min (second heating); held at 180°C for 1 to 5 minutes; cooled from 180°C to 50°C at 10°C / min.

[0032] According to one embodiment, the polyethylene yarn has a melting temperature (T m ) can be included.

[0033] Preferably, the polyethylene yarn has a melting temperature (T m ) can be included.

[0034] The polyethylene yarn is heated to a melting temperature (T m ) can be included.

[0035] According to one embodiment, the polyethylene yarn may have a melt index of 0.3 g / 10 min to 5.0 g / 10 min (190° C., 2.16 kgf load).

[0036] Specifically, the polyethylene yarn may have a melt index (190°C, 2.16 kgf load) of 0.3 g / 10 min or more, alternatively 1.0 g / 10 min or more, alternatively 1.5 g / 10 min or more, alternatively 2.0 g / 10 min or more; and 5.0 g / 10 min or less, alternatively 4.0 g / 10 min or less, alternatively 3.0 g / 10 min or less.

[0037] To ensure appropriate productivity, the melt index of the polyethylene yarn is preferably 0.3 g / 10 min or more, or 1.0 g / 10 min or more, or 1.5 g / 10 min or more, or 2.0 g / 10 min or more. However, if the melt index is too high, the strength of the polyethylene yarn may decrease. Therefore, the melt index of the polyethylene yarn is preferably 5.0 g / 10 min or less, or 4.0 g / 10 min or less, or 3.0 g / 10 min or less.

[0038] Preferably, the polyethylene yarn has a melt index of 0.3 g / 10 min to 5.0 g / 10 min, alternatively 1.0 g / 10 min to 5.0 g / 10 min, alternatively 1.0 g / 10 min to 4.0 g / 10 min, alternatively 1.5 g / 10 min to 4.0 g / 10 min, alternatively 1.5 g / 10 min to 3.0 g / 10 min, or alternatively 2.0 g / 10 min to 3.0 g / 10 min.

[0039] The melt index can be determined by the melt mass-flow rate (MFR) measurement method according to ISO1133-1:2022 at a temperature of 190° C. and a load of 2.16 kgf.

[0040] According to one embodiment, the polyethylene yarn may have a crystallinity of 60% to 80%.

[0041] Specifically, the polyethylene yarn may have a crystallinity of 60% or more, alternatively 65% ​​or more, alternatively 70% or more; and 80% or less, alternatively 75% or less.

[0042] To achieve appropriate mechanical properties, the polyethylene yarn preferably has a crystallinity of 60% or more, or 65% or more, or 70% or more. However, if the crystallinity is too high, processability may be reduced. Therefore, the polyethylene yarn preferably has a crystallinity of 80% or less, or 75% or less.

[0043] Preferably, the polyethylene yarn has a crystallinity of 60% to 80%, alternatively 65% ​​to 80%, alternatively 65% ​​to 75%.

[0044] According to one embodiment, the polyethylene yarn may have an L* value of 85.5 to 92.0.

[0045] The L* value is a lightness value in the L*a*b* (CIE LAB) color system measured using a spectrophotometer on a test piece made of the polyethylene yarn. The L*a*b* (CIE LAB) color system is one method of indicating color tone for color evaluation, and is a color space established by the International Commission on Illumination (CIE) that indicates colors visible to the eye. The L* value is an index indicating brightness trends and ranges from 0 to 100.

[0046] Specifically, the polyethylene raw yarn may have an L* value of 85.5 or more, or 86.0 or more, and 92.0 or less, or 91.5 or less. Preferably, the polyethylene raw yarn may have an L* value of 85.5 to 92.0, or 86.0 to 92.0, or 86.0 to 91.5. The L* value may be measured in reflection mode on a test piece of an appropriate size using a spectrophotometer.

[0047] By satisfying the above-mentioned properties, the polyethylene yarn can exhibit excellent thermal properties in post-processing processes such as dyeing, coating, and curing. The polyethylene yarn can be used to manufacture a variety of products, including rope-like cord products, industrial or medical protective equipment, airbags, bedding, and cooling materials.

[0048] According to another embodiment of the invention, providing a melt comprising polyethylene having a weight average molecular weight (Mw) of 50,000 g / mol to 600,000 g / mol and a melt index (190°C, 2.16 kgf load) of 0.3 g / 10 min to 5.0 g / 10 min; extruding the melt through a die to obtain a filament; allowing the filament to cool; drawing a multifilament formed from the cooled filaments; and winding the drawn multifilament, The cooling is performed in a cooling unit having a plurality of cooling zones divided by zone temperatures, and the plurality of cooling zones are set to have a temperature gradient that gradually decreases in a direction from an inlet of the filament to an outlet of the filament. A method for producing the polyethylene yarn is provided.

[0049] FIG. 1 is a simplified process diagram showing a process for producing polyethylene yarn according to an embodiment of the invention.

[0050] Referring to FIG. 1, the method for producing the polyethylene yarn may include the steps of: feeding a raw material containing a polyethylene resin into an extruder 100 to provide a melt for spinning; extruding the melt through a die 200 to obtain filaments 11; cooling the filaments 11 in a cooling unit 300; drawing the multifilament 10 obtained by bundling the filaments 11 in a bundling unit 400 in a multi-stage drawing unit 500; and winding the drawn multifilament around a winder 600.

[0051] Hereinafter, each step included in the method for producing polyethylene yarn will be described with reference to FIG.

[0052] First, a step of providing a spinning melt is performed, which provides a melt containing polyethylene.

[0053] The polyethylene may have a weight average molecular weight (Mw) of 50,000 to 600,000 g / mol.

[0054] To ensure adequate strength of the yarn, the weight-average molecular weight (Mw) of the polyethylene is preferably 50,000 g / mol or more. However, if the molecular weight of the polyethylene is too high, the high melt viscosity can overload the spinning apparatus, making process control difficult and resulting in poor physical properties of the yarn. Therefore, the weight-average molecular weight (Mw) of the polyethylene is preferably 600,000 g / mol or less.

[0055] Preferably, the weight average molecular weight (Mw) of the polyethylene may be 50,000 g / mol to 600,000 g / mol, alternatively 100,000 g / mol to 500,000 g / mol, alternatively 100,000 g / mol to 450,000 g / mol, alternatively 150,000 g / mol to 450,000 g / mol, alternatively 150,000 g / mol to 400,000 g / mol, alternatively 200,000 g / mol to 400,000 g / mol, alternatively 250,000 g / mol to 400,000 g / mol, or alternatively 300,000 g / mol to 400,000 g / mol.

[0056] The weight average molecular weight (Mw) can be measured by completely dissolving the polyethylene in a solvent and then using gel permeation chromatography (GPC) under the following conditions.

[0057] -Analytical equipment: PL-GPC 220 system -Column: 2 x PLGEL MIXED-B (7.5 x 300 mm) -Solvent: Trichlorobenzene (TCB) + 0.04 wt% dibutylhydroxytoluene (BHT) (after drying with 0.1% CaCl2) -Injector, detection temperature: 160℃ -Flow rate: 1.0ml / min -Injection volume: 200μl -Standard sample: polystyrene

[0058] The polyethylene may have a melt index (190° C., 2.16 kgf load) of 0.3 g / 10 min to 5.0 g / 10 min.

[0059] To ensure smooth flow within the extruder 100, the melt index of the polyethylene is preferably 0.3 g / 10 min or more, or 0.5 g / 10 min or more. However, if the melt index of the polyethylene is too high, it may be difficult to achieve high strength due to the relatively low molecular weight. Therefore, the melt index of the polyethylene is preferably 5.0 g / 10 min or less, or 4.0 g / 10 min or less, or 3.0 g / 10 min or less.

[0060] Preferably, the melt index of the polyethylene may be 0.3 g / 10 min to 5.0 g / 10 min, alternatively 0.3 g / 10 min to 4.0 g / 10 min, 0.3 g / 10 min to 3.0 g / 10 min, or alternatively 0.5 g / 10 min to 3.0 g / 10 min.

[0061] The melt index can be determined by the melt mass-flow rate (MFR) measurement method according to ISO1133-1:2022 at a temperature of 190° C. and a load of 2.16 kgf.

[0062] Next, the melt is extruded through a die to obtain a filament. As a non-limiting example, a die having 40 to 500 or 100 to 500 holes may be used in this step. The melt is extruded through the die 200 while being conveyed by a screw (not shown) in the extruder 100.

[0063] The spinning step is preferably carried out at a temperature of 250 to 315°C or 280 to 310°C.

[0064] In order to form the uniform melt and perform stable spinning, the temperature of the inside of the extruder 100 and the die 200 is preferably 250°C or higher during the spinning step. However, if the temperature during the spinning step is too high, thermal decomposition of the melt may occur, making it difficult to achieve high strength. Therefore, the temperature of the inside of the extruder 100 and the die 200 during the spinning step is preferably 315°C or lower.

[0065] The ratio of the hole length (L) to the hole diameter (D) of the die 200, L / D, may be 3-40, alternatively 5-30, alternatively 5-20, or alternatively 10-20.

[0066] In order to prevent die swell during melt extrusion, the L / D is preferably 3 or more. However, if the L / D is too large, thread breakage due to necking of the molten material passing through the die 200 and non-uniform extrusion due to pressure drop may occur. Therefore, the L / D is preferably 40 or less.

[0067] In consideration of processability and productivity, the spinning step is preferably carried out so that the melt is extruded from the spinneret at a single-hole discharge rate of 0.05 to 0.45 g / min and a linear discharge velocity of 0.3 to 5.0 cm / sec.

[0068] In the spinning step, if the spinning draft ratio (DR=V1 / V0) is too high, many yarn breakages occur, resulting in poor workability, while if it is too low, orientation crystallization may not be sufficient, resulting in poor morphological stability of the filaments. Here, V0 is the extrusion linear velocity of the melt (i.e., the average velocity of the melt until it falls vertically 1.25 m from the hole of the spinneret 200), and V1 is the spinning speed (i.e., the linear velocity of the first godet roller GR1).

[0069] The higher the spinning speed (V1), the lower the total draw ratio in the drawing process, making it difficult to improve the final strength of the raw yarn. Therefore, to ensure an appropriate spinning draft ratio, the extrusion linear velocity (V0) is preferably 0.3 cm / sec or more. However, if the extrusion linear velocity is too high, it is difficult to apply a high draw ratio, so the extrusion linear velocity (V0) is preferably 5.0 cm / sec or less.

[0070] Specifically, the extrusion linear velocity (V0) may be 0.3 to 5.0 cm / sec, alternatively 1.0 to 4.0 cm / sec, or alternatively 2.0 to 3.0 cm / sec.

[0071] In addition, in order to ensure the linear discharge speed of 0.3 to 5.0 cm / sec in the spinning step and to satisfy the requirement of a single fiber fineness of 10 denier or less, it is preferable to apply a relatively small single-hole discharge rate (e.g., 0.05 to 0.45 g / min, or 0.1 to 0.40 g / min, or 0.15 to 0.35 g / min) in the spinning step.

[0072] A step of cooling the filament is then performed.

[0073] As the molten material is extruded from the holes of the spinneret 200, the difference between the spinning temperature and room temperature causes the molten material to begin to solidify, forming semi-solid filaments. In this specification, both semi-solidified filaments and fully solidified filaments are commonly referred to as "filaments."

[0074] The melt is discharged from the holes of the die 200 to form a number of filaments 11, which are then cooled in the cooling section 300 and completely solidified.

[0075] According to one embodiment, the cooling is performed in a cooling unit 300 having a plurality of cooling zones divided by zone temperature, and the plurality of cooling zones may be configured to have a temperature gradient that gradually decreases in a direction from the inlet to the outlet of the filament.

[0076] Cooling the filaments in the cooling unit 300, which has a plurality of cooling zones set to have the temperature gradient, can provide polyethylene yarn that satisfies the thermal characteristics defined by the above formula 1. Furthermore, cooling in this manner can provide polyethylene yarn with a higher crystallinity and a better appearance.

[0077] According to one embodiment, the cooling unit may be provided with 2 to 5 cooling sections, which may be advantageous for achieving the above-mentioned effects.

[0078] Preferably, the plurality of cooling zones can be set to have a temperature gradient that gradually decreases in the direction from the inlet to the outlet of the filament within a temperature range of 15°C to 80°C.

[0079] To prevent breakage during the drawing process due to excessive cooling of the filaments, the filaments 11 are preferably cooled to a temperature of 15°C or higher or 20°C or higher. However, if the filaments are not cooled sufficiently, uneven solidification can cause large deviations in fineness, which can lead to breakage during the drawing process. Therefore, the filaments 11 are preferably cooled to a temperature of 80°C or lower or 75°C or lower.

[0080] 2 to 4 are diagrams each showing a schematic configuration of the cooling unit 300 according to an embodiment of the invention in the process diagram of FIG.

[0081] 2, the cooling unit 300 includes a first cooling section 310 and a second cooling section 320 disposed in a direction from the inlet to the outlet of the filament. According to one embodiment, the first cooling section 310 may be set to a temperature selected in the range of 45°C to 80°C, and the second cooling section 320 may be set to a temperature selected in the range of 15°C to 40°C.

[0082] 3, the cooling unit 300 includes a first cooling section 310, a second cooling section 320, and a third cooling section 330, which are arranged in a direction from the inlet to the outlet of the filament. According to one embodiment, the first cooling section 310 may be set to a temperature selected in the range of 45°C to 80°C, the second cooling section 320 may be set to a temperature selected in the range of 30°C to 50°C, and the third cooling section 330 may be set to a temperature selected in the range of 15°C to 30°C.

[0083] 4, the cooling unit 300 includes a first cooling zone 310, a second cooling zone 320, a third cooling zone 330, and a fourth cooling zone 340, which are arranged in a direction from the inlet to the outlet of the filament. According to one embodiment, the first cooling zone 310 may be set to a temperature selected in the range of 45°C to 80°C, the second cooling zone 320 may be set to a temperature selected in the range of 35°C to 55°C, the third cooling zone 330 may be set to a temperature selected in the range of 20°C to 40°C, and the fourth cooling zone 340 may be set to a temperature selected in the range of 15°C to 25°C.

[0084] Independently of the temperature setting for the cooling zones, cooling air may be supplied to the cooling zones.

[0085] According to one embodiment, the wind speed of the cooling air can be set to have a wind speed gradient that decreases in a direction from the inlet to the outlet of the filament.

[0086] Preferably, the plurality of cooling sections can be set to have a cooling air velocity gradient in the range of 0.1 m / s to 3.0 m / s, the velocity of which decreases from the inlet to the outlet of the filaments. By providing the cooling air velocity gradient, a polyethylene raw yarn with a smoother surface can be obtained.

[0087] The cooled and completely solidified filaments are then gathered by the gathering section 400 to provide the multifilament 10.

[0088] Optionally, the method may further include a step of applying oil to the filaments using an oil roller OR or an oil jet before forming the multifilament 10. The application of the oil may be performed by a metered oiling (MO) method. The application of the oil may be performed between godet rollers and / or between the last godet roller and the winder 600 in the subsequent drawing step.

[0089] Next, a step of drawing a multifilament formed from the cooled filaments is performed.

[0090] According to one embodiment, the method for producing the polyethylene yarn involves directly drawing the multifilament 10 obtained by melt spinning, without winding it separately, by continuously transferring it to a multi-stage drawing unit 500 including a plurality of godet rollers. This manufacturing method is different from the conventional two-stage process method in which the undrawn yarn formed by melt spinning is wound and then drawn at a high draw ratio at a high temperature.

[0091] To ensure that the final polyethylene yarn has high strength, the drawing step must be precisely controlled using a multi-stage drawing section 500 including multiple godet rollers.

[0092] For this reason, the drawing step is preferably performed in a multi-stage drawing unit 500 including two or more stages, or two to ten stages, or two to eight stages, or two to six stages of godet rollers GR1, . . . , GRn.

[0093] That is, the drawing step may be advantageously performed in a multi-stage drawing unit equipped with two or more godet rollers to obtain a polyethylene raw yarn having excellent dimensional stability and high strength. However, if the number of godet rollers in the multi-stage drawing unit is too large, the final polyethylene raw yarn may not have the desired physical properties or the overall process efficiency may decrease. Therefore, the drawing step is preferably performed in a multi-stage drawing unit equipped with 10 or less, 8 or less, or 6 or less godet rollers.

[0094] In order to ensure sufficient stretching in the stretching step, the temperature of the godet rollers included in the multi-stage stretching unit 500 can be set to 40 to 140°C.

[0095] For example, the temperature of the first godet roller GR1 of the plurality of godet rollers may be set to 40 to 80°C, and the temperature of the last godet roller GRn may be set to 110 to 140°C. The temperatures of the remaining godet rollers GR2 to GRn-1, excluding the first and last godet rollers GR1 and GRn, may be set to a temperature equal to or higher than the temperature of the godet roller located immediately before the godet roller. If necessary, any godet roller may be set to a temperature lower than the temperature of the godet roller located immediately before it.

[0096] In the multistage drawing section 500, the total draw ratio of the multifilament is determined by the linear velocity (mpm) of the first godet roller GR1 and the linear velocity (mpm) of the last godet roller GRn. That is, the total draw ratio means the value obtained by dividing the linear velocity of the last godet roller GRn among the godet rollers provided in the multistage drawing section 500 by the linear velocity of the first godet roller GR1.

[0097] When the linear speed of the first godet roller GR1 is determined, the linear speeds of the remaining godet rollers can be determined so that a total draw ratio of 4 to 15 times can be applied to the multifilament 10 in the multi-stage drawing section 500.

[0098] The drawing step results in drawing and heat-setting of the multifilament.

[0099] Unlike a method in which heat setting is roughly performed using hot air or the like, in the present invention, the multifilament is drawn in direct contact with the plurality of godet rollers in the multi-stage drawing unit 500 of the drawing step, so that heat setting can be performed precisely.

[0100] Next, the drawn multifilament is wound up. The multifilament drawn in the drawing step is wound up by a winder 600 to obtain a polyethylene yarn. [Effects of the Invention]

[0101] According to the present invention, there are provided a polyethylene raw yarn having excellent thermal properties and a method for more efficiently producing the polyethylene raw yarn. [Brief explanation of the drawings]

[0102] [Figure 1] FIG. 1 is a process diagram illustrating a process for producing polyethylene yarn according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically showing the configuration of a cooling section according to one embodiment of the invention in the process diagram of FIG. 1. [Figure 3] FIG. 2 is a diagram schematically showing the configuration of a cooling section according to one embodiment of the invention in the process diagram of FIG. 1. [Figure 4] FIG. 2 is a diagram schematically showing the configuration of a cooling section according to one embodiment of the invention in the process diagram of FIG. 1. [Figure 5] 1 is a temperature-rising DSC curve [X axis = temperature (° C.); Y axis = endothermic energy (mW)] obtained by differential scanning calorimetry for polyethylene raw yarn according to Example 1 of the present invention. [Figure 6]1 is a temperature-rising DSC curve [X axis = temperature (° C.); Y axis = endothermic energy (mW)] obtained by differential scanning calorimetry for polyethylene raw yarn according to Example 2 of the present invention. [Figure 7] 1 is a temperature-rising DSC curve [X axis = temperature (° C.); Y axis = endothermic energy (mW)] obtained by differential scanning calorimetry for polyethylene raw yarn according to Comparative Example 2 of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0103] Preferred examples are presented below to aid in understanding the invention, but the following examples are merely illustrative of the invention and are not intended to limit the invention thereto.

[0104] Example 1 Using the apparatus shown in FIG. 1, a polyethylene yarn containing 200 filaments and having a total fineness of 400 denier was produced.

[0105] Specifically, polyethylene chips having a weight-average molecular weight (Mw) of 340,000 g / mol and a melt index of 1.8 g / 10 min (190°C, load of 2.16 kgf) were charged into an extruder 100. The chips charged into the extruder 100 were melted to prepare a melt for spinning.

[0106] The melt was extruded through a die 200 having 200 holes.

[0107] The filament 11 formed while being extruded from the spinneret 200 was cooled in the cooling section 300 having the configuration shown in FIG.

[0108] The cooling section 300 includes a first cooling section 310, a second cooling section 320, a third cooling section 330, and a fourth cooling section 340 arranged in a direction from the inlet to the outlet of the filament.

[0109] The first cooling zone 310 was set to a temperature of 45°C; the second cooling zone 320 was set to a temperature of 35°C; the third cooling zone 330 was set to a temperature of 25°C; and the fourth cooling zone 340 was set to a temperature of 15°C.

[0110] Cooling air was supplied to the cooling section, and the speed of the cooling air was set to a range of 0.1 m / s to 3.0 m / s, with a decreasing speed gradient in the direction from the inlet to the outlet of the filaments.

[0111] The cooled filaments 11 were converged into a multifilament 10 by the converging section 400 and then continuously moved to the multi-stage drawing section 500 equipped with four stages of godet rollers GR1-GR8. In the multi-stage drawing section 500, the multifilament 10 was continuously drawn and heat-set at a total draw ratio of 8 times and a relaxation rate of 4% while in direct contact with the godet rollers. The temperature range of the godet rollers was set to 80 to 130°C.

[0112] The multi-stage drawn multifilament was wound on a winder 600 at a winding tension of 0.8 g / d to obtain a polyethylene raw yarn.

[0113] Example 2 A polyethylene raw yarn was produced in the same manner as in Example 1, except that the yarn was drawn at a total draw ratio of 4 times in the multistage drawing section 500.

[0114] Example 3 A polyethylene raw yarn was produced in the same manner as in Example 1, except that the yarn was drawn at a total draw ratio of 12 times in the multistage drawing section 500.

[0115] Example 4 A polyethylene yarn was produced in the same manner as in Example 1, except that the filaments 11 were cooled in a cooling section 300 having the configuration shown in FIG. 2 and the drawing was performed in a multi-stage drawing section 500 equipped with two stages of godet rollers GR1-GR4.

[0116] The cooling section 300 includes a first cooling section 310 and a second cooling section 320 arranged in a direction from the inlet to the outlet of the filament; the first cooling section 310 is set to a temperature of 45°C; and the second cooling section 320 is set to a temperature of 25°C.

[0117] Example 5 A polyethylene yarn was produced in the same manner as in Example 1, except that polyethylene chips having a weight-average molecular weight (Mw) of 340,000 g / mol and a melt index (190°C, 2.16 kgf load) of 0.5 g / 10 min were used.

[0118] Comparative Example 1 A polyethylene yarn was produced in the same manner as in Example 1, except that the filaments were cooled in a cooling section consisting of one cooling zone instead of the cooling section configured as shown in Figure 4. At this time, the cooling section was set to a temperature of 45°C.

[0119] Comparative Example 2 A polyethylene yarn was produced in the same manner as in Example 2, except that polyethylene chips having a weight-average molecular weight (Mw) of 200,000 g / mol and a melt index of 7.0 g / 10 min (190°C, 2.16 kgf load) were used.

[0120] Comparative Example 3 A polyethylene yarn was produced in the same manner as in Example 4, except that polyethylene chips having a weight-average molecular weight (Mw) of 200,000 g / mol and a melt index of 7.0 g / 10 min (190°C, 2.16 kgf load) were used.

[0121] Test Example The polyethylene fibers produced in the examples and comparative examples were tested by the following methods, and the results are shown in Table 1 below.

[0122] (1) Crystallinity of polyethylene yarn The crystallinity of the polyethylene yarn was measured using an X-ray diffraction analyzer with an X-ray source. Specifically, the polyethylene yarn was cut to prepare a sample with a length of 2.5 cm, and the sample was fixed in a sample holder of the X-ray diffraction analyzer, and then measurement was performed under the following conditions.

[0123] i) Experimental equipment: Empyrean (Malvern Panalytical Ltd) ii) X-ray source: Cu-Kα (1.54Å), 45kV, 20mA

[0124] iii) Incident beam path -Filter:Beta-filter Nickel0.02mm -Slit: AS1゜, DS1 / 2゜, SS:0.04rad -Mask: 10mm

[0125] iv) Diffracted beam path -Detector:PIXcel3D 2X2(area detector) -Slit: AS5.0mm, SS: 0.04rad

[0126] v) Scan range: 10°~32° vi) Step size: 0.1° vii)Beam direction:Reflection viii) Background Method: Constant Background ix) Standard Specimen: 3000 denier

[0127] x) Apparent crystallite size (ACS): estimated from the half-height of the peak (110) plane and (200) plane using the Scherrer equation. JPEG2025529500000002.jpg1764

[0128] -λ:X-ray wavelength, 0.154nm -β:FWHM -Θ: Bragg angle (max. peak) -Scherrer constant K=0.89

[0129] xi)Crystallinity(Xc):Constant background method

[0130] (2) Melting temperature and heat of fusion of polyethylene yarn Using a differential scanning calorimeter (model: DSC7, manufacturer: Perkin Elmer), the melting temperature and heat of fusion of a polyethylene raw yarn test piece were measured during the first and second heating periods in succession under the following conditions. The value of Equation 1 above was then calculated from the values ​​of the heat of fusion during the first and second heating periods.

[0131] Heat from 50°C to 180°C at 10°C / min (first heating); hold at 180°C for 1 to 5 minutes; cool from 180°C to 50°C at 200°C / min; hold at 50°C for 1 to 5 minutes; heat from 50°C to 180°C at 10°C / min (second heating); hold at 180°C for 1 to 5 minutes; cool from 180°C to 50°C at 10°C / min.

[0132] Fig. 5 shows DSC curves [X axis = temperature (°C); Y axis = endothermic heat (mW)] for the first and second heating periods for the polyethylene raw yarn of Example 1. Fig. 6 shows DSC curves for the first and second heating periods for the polyethylene raw yarn of Example 2. Fig. 7 shows DSC curves for the first and second heating periods for the polyethylene raw yarn of Comparative Example 2.

[0133] (3) Color of polyethylene yarn The lightness (L*) value of the polyethylene raw yarn test piece was measured using a spectrophotometer (model name: Ci7860, manufacturer: X-rite) according to the L*a*b* (CIE LAB) color system. Test pieces measuring 63.5 mm x 12.7 mm x 3.2 mm according to the ASTM D256 standard were prepared, and the average value was recorded after three measurements in reflection mode.

[0134] (4) Dry heat shrinkage rate A polyethylene raw yarn test piece is left in a temperature and humidity chamber at 25°C and a relative humidity of 65% for 24 hours. The test piece is heat-shrunk at 150°C for 30 minutes without tension, and then left in the temperature and humidity chamber for another 24 hours. The length of the test piece before and after shrinkage is measured, and the dry heat shrinkage is calculated using the following formula:

[0135] Dry heat shrinkage rate (%)=[(L0-L1) / L0]x100

[0136] L0: Length of the sample before heat shrinkage after leaving it in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours L1: The length of the sample after it has been left in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours after heat shrinkage

[0137] [Table 1]

[0138] Referring to Table 1, it can be seen that the polyethylene yarns according to the Examples have generally higher L* values ​​and lower dry heat shrinkage rates than the polyethylene yarns according to the Comparative Examples, and thus have excellent thermal properties. [Explanation of symbols]

[0139] 100: Extruder 200: nozzle 300:quenching zone 310: First cooling section 320: Second cooling section 330: 3rd cooling section 340: 4th cooling section 11: Filament 10: Multifilament OR: Oil roller 400:Focusing part 500: Multi-stage stretching section GR1: 1st Godet Roller GRn: The Last Godet Roller 600: Winder

Claims

1. Polyethylene raw yarn satisfying the following formula 1: <Formula 1> 0.05≦[(AB) / A]≦0.35 In the above formula 1, A is the heat of fusion (ΔH) in the first temperature rise (1st run: temperature rise from 50°C to 180°C at 10°C / min) by differential scanning calorimetry for the polyethylene raw yarn. f , J / g), B is the value of the heat of fusion (ΔH) in the second heating run (2nd run: the polyethylene raw yarn cooled to 50°C after the first heating run is heated from 50°C to 180°C at a rate of 10°C / min) by differential scanning calorimetry for the polyethylene raw yarn. f , J / g).

2. The polyethylene yarn has a melting temperature (T m 2. The polyethylene fiber according to claim 1, wherein

3. The polyethylene raw yarn has a melting temperature (T m ) and the melting temperature (T m 2. The polyethylene fiber according to claim 1, wherein

4. 2. The polyethylene yarn according to claim 1, wherein the polyethylene yarn has a melt index (190°C, 2.16 kgf load) of 0.3 g / 10 min to 5.0 g / 10 min.

5. The polyethylene yarn according to claim 1, wherein the polyethylene yarn has a crystallinity of 60% to 80%.

6. The polyethylene raw yarn according to claim 1, wherein the polyethylene raw yarn has an L* value (a lightness value in the L*a*b* (CIE LAB) color system measured using a spectrophotometer on a test piece made of the polyethylene raw yarn) of 85.5 to 92.

0.

7. providing a melt comprising polyethylene having a weight average molecular weight (Mw) of 50,000 g / mol to 600,000 g / mol and a melt index (190°C, 2.16 kgf load) of 0.3 g / 10 min to 5.0 g / 10 min; extruding the melt through a die to obtain a filament; allowing the filament to cool; drawing a multifilament formed from the cooled filaments; and winding the drawn multifilament, The cooling is performed in a cooling unit having a plurality of cooling zones divided by zone temperatures, and the plurality of cooling zones are set to have a temperature gradient that gradually decreases from an inlet portion of the filament to an outlet portion. A method for producing the polyethylene fiber according to claim 1.

8. 8. The method for producing polyethylene fiber according to claim 7, wherein the plurality of cooling sections are set to have a temperature gradient that gradually decreases in a direction from an inlet portion to an outlet portion of the filament within a temperature range of 15°C to 80°C.

9. The method for producing polyethylene yarn according to claim 7, wherein the cooling unit comprises 2 to 5 cooling sections.

10. the cooling section includes first and second cooling sections arranged in a direction from the inlet to the outlet of the filaments, The first cooling zone is set to a temperature selected in the range of 45°C to 80°C, and the second cooling zone is set to a temperature selected in the range of 15°C to 40°C. The method for producing the polyethylene fiber according to claim 7.

11. the cooling section includes first to third cooling sections arranged in a direction from an inlet portion of the filament to an outlet portion thereof, The first cooling zone is set to a temperature selected in the range of 45°C to 80°C, the second cooling zone is set to a temperature selected in the range of 30°C to 50°C, and the third cooling zone is set to a temperature selected in the range of 15°C to 30°C. The method for producing the polyethylene fiber according to claim 7.

12. the cooling section includes first to fourth cooling sections arranged in a direction from an inlet portion of the filament to an outlet portion thereof, The first cooling zone is set to a temperature selected in the range of 45°C to 80°C, the second cooling zone is set to a temperature selected in the range of 35°C to 55°C, the third cooling zone is set to a temperature selected in the range of 20°C to 40°C, and the fourth cooling zone is set to a temperature selected in the range of 15°C to 25°C. The method for producing the polyethylene fiber according to claim 7.

13. Cooling air is supplied to the plurality of cooling sections, The wind speed of the cooling air is set to have a wind speed gradient that decreases in a direction from an inlet portion of the filament to an outlet portion of the filament. The method for producing the polyethylene fiber according to claim 7.

Images