Method for producing high strength polyethylene yarn with improved shrinkage rate

Abstract

The present invention relates to a high-strength polyethylene yarn having an improved shrinkage rate and a method for producing the same, and more particularly to a high-strength polyethylene yarn having a specific microstructure, an improved shrinkage rate, and capable of producing a high-density raw cloth, and a method for producing the same.

Description

[Technical field]

[0001] The present invention relates to a high-strength polyethylene raw yarn having an improved shrinkage rate and a method for producing the same, and more particularly to a high-strength polyethylene raw yarn having a specific microstructure, an improved shrinkage rate, and capable of producing a high-density raw cloth, and a method for producing the same. [Background technology]

[0002] People working in the security field, such as police and military personnel, as well as people handling sharp cutting tools in a variety of other industrial sectors, are constantly at risk of injury. To minimize the risk of injury, protective products such as gloves or clothing must be provided.

[0003] The protective products are required to be cut resistant in order to adequately protect the human body from weapons such as knives or sharp cutting tools.

[0004] In order to provide protective products with high cut resistance, high-strength polyethylene yarns are used in the manufacture of the protective products. For example, the high-strength polyethylene yarns may be used alone to manufacture a roll of fabric, or the high-strength polyethylene yarns may be combined with other types of yarns to form a ply-twisted yarn, which may then be used to manufacture a roll of fabric.

[0005] In order to solve the environmental problems caused by the use of organic solvents in the gel spinning method using ultra-high molecular weight polyethylene (UHMWPE), a type of high-strength polyethylene raw yarn, a melt-spun raw yarn using high-density polyethylene, which has a lower weight-average molecular weight, has been developed.

[0006] Unlike other polymers, high density polyethylene polymers have a very small number of molecular chains with short or long branches. Due to the influence of such branched chains, most of the high strength polyethylene raw yarns produced by melt spinning using high density polyethylene have high crystallinity and low shrinkage. When the shrinkage is low, there is a disadvantage that the weaving and knitting density of the product can only be determined in the weaving and knitting process in which the raw yarn is used to produce the finished product. In addition, it is impossible to produce a raw cloth with a higher density than the density determined by the weaving and knitting density. Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve the problems of the prior art, an object of the present invention is to provide a high-strength polyethylene raw yarn having an improved shrinkage rate and a method for producing the same.

[0008] Another object of the present invention is to provide a polyethylene yarn and a method for producing the same, which enable the production of a raw roll that has high cut resistance and provides an excellent wearing feel.

[0009] In addition, the present invention aims to provide a high-strength polyethylene raw yarn and a manufacturing method thereof that can provide a raw cloth having a higher areal density than the areal density that can be adjusted in the existing weaving and knitting processes. [Means for solving the problem]

[0010] As a result of research conducted to achieve the above-mentioned object, the inventors of the present invention discovered that by producing polyethylene raw yarn having a specific microstructure, the shrinkage rate of the raw yarn can be improved and high strength physical properties can be exhibited, thereby completing the present invention.

[0011] The inventors also discovered that by weaving and knitting using such polyethylene raw yarn with an improved shrinkage rate, it is possible to provide a raw cloth with a higher density and to manufacture a raw cloth that has high cut resistance and provides an excellent wearing comfort, thereby completing the present invention.

[0012] The polyethylene raw yarn having the specific microstructure means a raw yarn whose scattering vector in small-angle X-ray scattering (SAXS), which will be described later in detail, satisfies a specific range, and it has been found that it is possible to achieve the desired physical properties with a raw yarn that satisfies such a specific microstructure.

[0013] In the present invention, as long as it is possible to produce a raw yarn whose scattering vector of small angle X-ray scattering (SAXS) described below satisfies a specific range, the means for producing the raw yarn is not limited. As an example, the raw yarn can be produced by adjusting the molecular weight distribution of the polyethylene resin, the spinning temperature, the draw ratio, and the draw temperature during the production of the raw yarn to specific ranges. As long as the scattering vector of small angle X-ray scattering (SAXS) satisfies the range described below, the means for producing the raw yarn is not limited thereto.

[0014] In one embodiment of the present invention, the scattering vector of small angle X-ray scattering (SAXS) is 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05~0.08Å -1 The present invention relates to a polyethylene raw yarn having a ratio (A / B) of a peak intensity (Intensity Peak) generated at a point A to a highest point B of 16 or more and a shrinkage rate of 2.5% or more.

[0015] In one embodiment, the raw yarn may have a melt index (MI) of 0.3 to 6 g / 10 min measured at 190° C. and 2.16 kg, and a molecular weight distribution of more than 5 and less than 9.

[0016] In one embodiment, the raw yarn may have a crystallinity of 65 to 85%. In one embodiment, the raw yarn may have a melting temperature of 130 to 140°C. In one embodiment, the raw yarn has a density of 0.93 to 0.97 g / cm 3 It is possible.

[0017] Another aspect of the present invention is a method for producing a polyethylene raw yarn, comprising the steps of: A step of melting polyethylene chips having a melt index (MI) of 0.3 to 6 g / 10 min measured at 190 ° C. and 2.16 kg and a molecular weight distribution of more than 5 and less than 9 to obtain a polyethylene melt; spinning the polyethylene melt through a die having a plurality of nozzle holes; cooling the plurality of filaments formed when the polyethylene melt is discharged from the nozzle holes; converging the cooled filaments to form a multifilament yarn; Stretching the multifilament yarn at a total draw ratio of 5 to 20 times and heat fixing it; winding the drawn and heat-set multifilament yarn; The small angle X-ray scattering (SAXS) vector is 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05~0.08Å -1 The present invention provides a method for producing polyethylene raw yarn, in which the ratio (A / B) of the intensity peak generated at the highest point A to the highest point B is 16 or more, and the shrinkage rate is 2.5% or more.

[0018] In one embodiment, the spinning temperature of the polyethylene melt may be 220 to 300°C. In one embodiment, the maximum stretching temperature during the stretching may be 100 to 150°C.

[0019] In one embodiment, the drawing step may be performed by multi-stage drawing. In one embodiment, the stretching step may be performed using a plurality of godet rollers. In one embodiment, the drawing step may be performed by multi-stage drawing having 4 to 20 stages.

[0020] In one embodiment, the plurality of godet rollers are set at a temperature of 50 to 150° C., The temperature of the first godet roller among the plurality of godet rollers is 50 to 80° C. The temperature of the last godet roller among the plurality of godet rollers is 100 to 150° C. The temperature of each of the godet rollers, except for the first and last godet rollers, may be equal to or higher than the temperature of the godet roller immediately preceding it. Effect of the Invention

[0021] The polyethylene raw yarn according to the present invention has a specific microstructure, which makes it possible to provide a polyethylene raw yarn having high strength and an improved shrinkage rate.

[0022] Furthermore, a base cloth of a woven or knitted fabric produced from such a polyethylene raw yarn can provide a higher density base cloth than a base cloth produced using a conventional high-strength polyethylene raw yarn.

[0023] Furthermore, the polyethylene fiber according to the present invention has high strength despite being produced by melt spinning, and therefore has the effect of being applicable to protective products having excellent cut resistance. [Brief description of the drawings]

[0024] [Figure 1] 1 is a small angle X-ray scattering (SAXS) graph of the raw yarn according to Example 1. [Diagram 2] 1 is a small angle X-ray scattering (SAXS) graph of the raw yarn according to Example 2. [Diagram 3] 1 is a small angle X-ray scattering (SAXS) graph of the raw yarn according to Example 3. [Figure 4] 1 is a small angle X-ray scattering (SAXS) graph of the raw yarn according to Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention will now be described in more detail. Unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The terms used in the description of the present invention are merely for the purpose of effectively describing a particular embodiment and are not intended to limit the present invention.

[0026] Additionally, as used in the specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0027] Furthermore, when a part "comprises" a certain component, this means that it may further include other components, rather than excluding other components, unless otherwise specified to the contrary.

[0028] The present inventors have conducted research to provide a high-strength polyethylene yarn that can achieve both high strength and high shrinkage, and have found that such properties can be achieved by using a polyethylene yarn having a specific microcrystalline structure.

[0029] Specifically, one embodiment of the present invention is a method for producing a small-angle X-ray scattering (SAXS) scattering vector of 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The present invention relates to a polyethylene raw yarn having a ratio (A / B) of the intensity peak occurring at the highest point B to the highest point B of 16 or more, and a shrinkage rate of 2.5% or more. The present inventors have found that it is possible to produce a raw cloth having high strength and high density due to a high shrinkage rate, as intended, within a range in which the A / B of the small angle X-ray scattering (SAXS) and the shrinkage rate are simultaneously satisfied, and have completed the present invention.

[0030] The A / B of the small angle X-ray scattering (SAXS) may be 16 or more, preferably 18 or more, more preferably 20 to 40. Specifically, it may be 16 to 35. Within the above range, a specific fine crystal structure is formed, and thus it is possible to provide a raw yarn having a shrinkage rate of 2.5% or more, more preferably 3% or more, 3.5% or more, 4% or more, specifically 2.5 to 10%. The shrinkage rate means the dry heat shrinkage rate at 100°C. In addition to the above, it is possible to provide a raw yarn having high strength.

[0031] The present invention is not limited to a manufacturing method as long as it is possible to produce a raw yarn that simultaneously satisfies the physical properties of an A / B ratio of 16 or more in small angle X-ray scattering (SAXS) and a shrinkage rate of 2.5% or more. As an example, the raw yarn can be produced by adjusting the molecular weight distribution of the polyethylene resin, the spinning temperature, the draw ratio, and the draw temperature during the production of the raw yarn within specific ranges.

[0032] More specifically, it is produced using a polyethylene resin having a molecular weight distribution of more than 5 and less than 9, and the spinning temperature may be 220 to 300°C, the stretching ratio may be 5 to 20 times, and the stretching temperature may be 100 to 150°C. However, the above conditions are merely illustrative and are not intended to be limiting. Various conditions in the ordinary technical field may be modified to practice, and the above conditions are merely intended to illustrate or explain the present invention and are not intended to limit the scope of the present invention.

[0033] The configuration of the present invention will be described more specifically below.

[0034] In one embodiment of the present invention, the polyethylene resin used as the raw material means one whose repeating units are substantially ethylene, and may be a copolymer with a small amount of other monomers, such as α-olefins, acrylic acid and its derivatives, methacrylic acid and its derivatives, vinylsilane and its derivatives, etc. Also, blends (mixtures) of these copolymers with ethylene homopolymers or copolymers of other α-olefins, etc. are possible.

[0035] More preferably, a copolymer of ethylene with an α-olefin such as propylene or butene-1 is used to contain a certain amount of short or long chain branching, which is more advantageous in providing a raw yarn having a high shrinkage rate of the present invention. Ethylene homopolymers can also be used as long as they satisfy the physical properties of the present invention.

[0036] The polyethylene resin may have a weight average molecular weight of 600,000 g / mol or less, more specifically, 80,000 to 600,000 g / mol, in order to enable melt spinning.

[0037] In one embodiment of the present invention, the polyethylene raw yarn may have a molecular weight distribution of more than 5 and less than 9, more preferably 6 to 8, and even more preferably 6.5 to 7.5. The molecular weight distribution is the ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn), and may also be called polydispersity index or molecular weight distribution index (MWD). In addition, the melt index (MI) measured at 190°C and 2.16 kg may be 0.3 to 6 g / 10 min, more preferably 0.4 to 3 g / 10 min.

[0038] As long as all of the above physical properties are satisfied, the fluidity of the molten material during melt extrusion of the raw yarn is good, thermal decomposition is prevented, and processability is ensured without yarn breakage during drawing, making it possible to produce raw yarn with uniform physical properties, and to provide raw yarn with the desired high strength and shrinkage rate of 2.5% or more.

[0039] In addition, the density is 0.93 to 0.97 g / cm 3 , more preferably 0.941 to 0.965 g / cm 3 By using high density polyethylene (HDPE) that satisfies the range of molecular weight distribution of more than 5 and less than 9, it is possible to obtain fibers with a crystallinity of 65 to 85%, more preferably 70 to 80%, by melt spinning. The crystallinity of the polyethylene raw yarn can be derived together with the size of crystallites during analysis of crystallinity using an X-ray scattering analyzer.

[0040] In one embodiment, the cross-sectional shape of the yarn is not limited, but may be circular, or may be twisted.

[0041] In one embodiment, the polyethylene raw yarn of the present invention may be a multifilament yarn which is a bundle of 40 to 500 continuous filaments. Each of the continuous filaments may have a fineness of 1 to 3 denier, and the polyethylene raw yarn may have a total fineness of 100 to 1,000 denier. Within the above range, a raw cloth having a light weight and excellent durability can be provided.

[0042] The method for producing a polyethylene raw yarn according to one embodiment of the present invention will be specifically described below. The polyethylene raw yarn of the present invention has a scattering vector of 0 to 0.04 Å in small angle X-ray scattering (SAXS). -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 As long as the ratio (A / B) of the intensity peak generated at the highest point A to the highest point B is 16 or more and the shrinkage rate is 2.5% or more, the manufacturing method is not limited thereto, and the following describes one embodiment.

[0043] A method for producing a raw yarn according to one embodiment of the present invention includes the steps of: A step of melting polyethylene chips having a melt index (MI) of 0.3 to 6 g / 10 min measured at 190 ° C. and 2.16 kg and a molecular weight distribution of more than 5 and less than 9 to obtain a polyethylene melt; spinning the polyethylene melt through a die having a plurality of nozzle holes; cooling the plurality of filaments formed when the polyethylene melt is discharged from the nozzle holes; converging the cooled filaments to form a multifilament yarn; A step of drawing and heat setting the multifilament yarn at a total draw ratio of 5 to 20 times; winding the drawn and heat-set multifilament yarn; may include:

[0044] Each step will be described in detail. First, polyethylene in the form of chips is fed into an extruder 100 and melted to obtain a polyethylene melt.

[0045] The polyethylene chip may have a polydispersity index (PDI) of more than 5 and not more than 9. The polyethylene chip may also have a melt index (MI) of 0.3 to 6 g / 10 min. The polyethylene chip may also have a weight average molecular weight (Mw) of 600,000 g / mol or less, more specifically 80,000 to 600,000 g / mol, preferably 100,000 to 500,000 g / mol, more preferably 200,000 to 400,000 g / mol. Within the weight average molecular weight (Mw) range, a high strength raw yarn can be produced, specifically a raw yarn having a tensile strength of 10 g / d or more can be produced. When the weight average molecular weight (Mw) is excessively large, such as exceeding 600,000 g / mol, the spinning device is overloaded due to the high melt viscosity, and the process cannot be appropriately controlled, making it difficult to ensure excellent physical properties of the raw yarn. Therefore, the polyethylene chips preferably have a weight average molecular weight (Mw) of 600,000 g / mol or less, more specifically, 80,000 to 600,000 g / mol, preferably 100,000 to 500,000 g / mol, and more preferably 200,000 to 400,000 g / mol.

[0046] Molten polyethylene is conveyed through a die by a screw in the extruder and extruded through a plurality of holes formed in the die. The number of holes in the die is determined according to the DPF (Denier Per Filament) and fineness of the raw yarn to be produced. For example, when producing a raw yarn having a total fineness of 75 denier, the die may have 20 to 75 holes, and when producing a raw yarn having a total fineness of 450 denier, the die may have 90 to 450 holes, preferably 100 to 400 holes.

[0047] The melting process in the extruder and the extrusion process through the die can be changed depending on the melt index of the polyethylene chips, and specifically, for example, they can be performed at 150 to 315°C, preferably 220 to 300°C, and more preferably 250 to 290°C. That is, it is preferable that the extruder and die are maintained at 150 to 315°C, preferably 220 to 300°C, and more preferably 250 to 290°C.

[0048] If the spinning temperature is less than 150° C., the polyethylene may not melt uniformly due to the low spinning temperature, making spinning difficult, whereas if the spinning temperature exceeds 315° C., the polyethylene may be thermally decomposed, making it impossible to achieve the desired strength.

[0049] The ratio (L / D) of the hole length L to the hole diameter D in the spinneret may be 3 to 40. If L / D is less than 3, a die swell phenomenon occurs during melt extrusion, making it difficult to control the elastic behavior of the polyethylene, resulting in poor spinnability, and if L / D exceeds 40, thread breakage due to necking of the molten polyethylene passing through the spinneret and non-uniform extrusion due to pressure drop may occur.

[0050] The molten polyethylene is extruded from the holes in the spinneret, and the difference between the spinning temperature and room temperature causes the polyethylene to start to solidify, forming a semi-solid filament. In this specification, both the semi-solid filament and the completely solidified filament are referred to as "filament."

[0051] The filaments are cooled in a cooling section (or "quenching zone") to completely solidify. The filaments can be cooled by air cooling.

[0052] The filaments are preferably cooled in the cooling section to 15 to 40° C. using cooling air at a speed of 0.2 to 1 m / sec. If the cooling temperature is less than 15° C., the elongation is insufficient due to overcooling, and yarn breakage may occur during drawing, whereas if the cooling temperature exceeds 40° C., the fineness deviation between the filaments becomes large due to non-uniform solidification, and yarn breakage may occur during drawing.

[0053] Furthermore, by performing multi-stage cooling during cooling in the cooling section, crystallization can be carried out more uniformly.

[0054] More specifically, the cooling section is divided into three or more sections. For example, when it has three cooling sections, it is preferable that the temperature is designed to be gradually lower from the first cooling section to the third cooling section. For example, the first cooling section may be set to 40 to 80°C, the second cooling section may be set to 30 to 50°C, and the third cooling section may be set to 15 to 30°C.

[0055] Also, by setting the wind speed in the first cooling section to the highest, it is possible to produce fibers with a smoother surface. Specifically, the first cooling section may use cooling wind with a wind speed of 0.8 to 1 m / sec to cool to 40 to 80°C, the second cooling section may use cooling wind with a wind speed of 0.4 to 0.6 m / sec to cool to 30 to 50°C, and the third cooling section may use cooling wind with a wind speed of 0.2 to 0.5 m / sec to cool to 15 to 30°C. By adjusting the conditions in this way, it is possible to produce raw yarn with a higher crystallinity and a smoother surface.

[0056] Next, the cooled and completely solidified filaments are bundled by a bundler to form a multifilament.

[0057] The polyethylene raw yarn of the present invention may be produced by a direct spin-draw (DSD) process, in which the multifilament is directly transmitted to a multistage drawing section including a plurality of godet roller sections, and is multistage-drawn at a total draw ratio of 5 to 20 times, preferably 8 to 15 times, and then wound on a winder.

[0058] As an example, the drawing step using a plurality of godet rollers is preferably performed in a multi-stage drawing of 4 stages or more. Preferably, the drawing step may be performed in a multi-stage drawing of 4 stages or more and 20 stages or less using a plurality of godet rollers. If the multi-stage drawing is performed in 4 stages or less, rapid drawing occurs in each section of the godet rollers, which may increase the frequency of fuzz generation during the production of the filament yarn, increase the initial modulus, and cause the raw cloth to become excessively stiff. In addition, if the multi-stage drawing proceeds to 20 stages or more, friction between the filament yarn and the godet rollers increases, which may cause damage to the filament and breakage of the yarn.

[0059] Even if a polyethylene chip having a polydispersity index (PDI) of more than 5 and not more than 9 and a melt index (MI) (190°C) of 0.3 to 6 g / 10 min is used, the desired physical properties cannot be obtained if the draw ratio, draw temperature, and stage number conditions of the method of the present invention are not satisfied. For example, during the drawing, the maximum draw temperature is preferably 100 to 150°C, the total draw ratio is 5 to 20, and multi-stage drawing of 4 or more stages may be performed. The maximum draw temperature means the highest temperature in the drawing section, and the total draw ratio means the final draw ratio of the fiber after the final drawing compared to the fiber before drawing.

[0060] For example, the multistage drawing may be performed using a plurality of godet rollers in 4 stages or more, more specifically, in 4 stages or more and 20 stages or less. The temperature of the first godet roller GR1 among the plurality of godet rollers (GR1...GRn) may be 50 to 80°C, and the temperature of the last godet roller GRn may be 100 to 150°C. The temperature of each of the remaining godet rollers except for the first and last godet roller sections (GR1, GRn) may be set to be the same as or higher than the temperature of the godet roller in the previous stage. The temperature of the last godet roller section GRn may be set to be the same as or higher than the temperature of the godet roller section in the previous stage, but may also be set to be slightly lower than that.

[0061] In addition, during multi-stage drawing, by providing a shrinkage drawing (relaxation) of 1 to 5% in the final drawing section, it is possible to provide a raw yarn having even better durability.

[0062] More specifically, the multi-stage stretching may be composed of a total of four godet roller sections, and the first godet roller section may be set to stretch 2-4 times at 50-80°C, the second godet roller section may be set to stretch 3-10 times at 70-100°C, the third godet roller section may be set to stretch 1.1-3 times at 80-110°C, and the fourth godet roller section may be set to shrink and stretch (relax) 1-5% at 100-150°C. Each of the first godet roller section to the fourth godet roller section may be formed of a plurality of godet rollers. More specifically, the first godet roller section to the fourth godet roller section may be formed of two or more godet rollers, more specifically, two to ten godet rollers.

[0063] Alternatively, the polyethylene raw yarn of the present invention may be produced by once winding the multifilament as an undrawn yarn and then drawing the undrawn yarn. That is, the polyethylene raw yarn of the present invention may be produced by a two-stage process in which polyethylene is melt-spinned to once produce an undrawn yarn, and then the undrawn yarn is drawn.

[0064] If the total draw ratio applied in the drawing process is less than 5, the final polyethylene raw yarn cannot have a crystallinity of 65% or more, and cannot achieve physical properties such as a small angle X-ray scattering (SAXS) A / B of 16 or more and a shrinkage rate of 2.5% or more. In addition, there is a risk of pilling being induced on the raw cloth manufactured from the raw yarn.

[0065] On the other hand, if the total draw ratio exceeds 20 times, yarn breakage may occur, the strength of the finally obtained polyethylene raw yarn may not be suitable, and the weavability of the polyethylene raw yarn may be poor, and the raw cloth manufactured using the same may be too stiff, which may cause inconvenience to users.

[0066] Once the linear speed of the first godet roller section GR1, which determines the spinning speed of the melt spinning of the present invention, is determined, the linear speeds of the remaining godet roller sections are appropriately determined so that a total draw ratio of 5 to 20 times, preferably 8 to 15 times, can be applied to the multifilament in the multistage drawing section.

[0067] The multistage drawing section simultaneously performs multistage drawing and heat setting of the multifilament, and the multistage-drawn multifilament is wound on a winder to complete the polyethylene raw yarn of the present invention.

[0068] The polyethylene fiber of the present invention produced as described above can be used to produce protective products requiring excellent cut resistance (for example, protective gloves, underwear, bags, etc.).

[0069] The present invention will be described in more detail below based on examples and comparative examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples. The physical properties were measured as follows.

[0070] <Weight average molecular weight (Mw) (g / mol) and polydispersity index (PDI)> The polyethylene raw yarn was completely dissolved in the following solvent, and then the weight average molecular weight (Mw) and polydispersity index (Mw / Mn: PDI) of the polyethylene raw yarn were determined using the following gel permeation chromatography (GPC).

[0071] -Analytical equipment: Tosoh HLC-8321GPC / HT -Column: PLgel guard (7.5 x 50 mm) + 2 x PLgel mixed-B (7.5 x 300 mm) -Column temperature: 160°C -Solvent: Trichlorobenzene (TCB) + 0.04 wt.% dibutylhydroxytoluene (BHT) (after drying with 0.1% CaCl2) -Injector and detector temperature: 160℃ -Detector: RI Detector -Flow rate: 1.0ml / min -Injection volume: 300mL -Sample concentration: 1.5mg / mL -Standard sample: polystyrene

[0072] <Tensile strength (g / d), initial modulus (g / d), and elongation (%)> The deformation-stress curves of polyethylene raw yarns were obtained using a universal tensile tester (Instron Engineering Corp, Canton, Mass.) according to the ASTM D2256 method. The length of the sample was 250 mm, the tensile speed was 300 mm / min, and the initial load was set at 0.05 g / d. The tensile strength (g / d) and elongation (%) were calculated from the stress and elongation at the break point, and the initial modulus (g / d) was calculated from the tangent line that gave the maximum slope near the origin of the curve. Five measurements were taken for each raw yarn, and the average value was calculated.

[0073] <Crystallization of raw yarn> The crystallinity of the polyethylene yarn was measured using an XRD (X-ray Diffractometer) [manufacturer: PANalytical, model name: EMPYREAN]. Specifically, the polyethylene yarn was cut to prepare a sample having a length of 2.5 cm, and the sample was fixed to a sample holder, and then the measurement was performed under the following conditions.

[0074] Light source (X-ray Source):Cu-Kα radiation Power: 45KV x 25mA Mode: Continuous scan mode Scan angle range: 10~40° Scan speed: 0.1° / sec

[0075] <Melting index> Measured according to ASTM D1238 at 190°C and 2.16 kg.

[0076] <Small angle X-ray scattering> The measurement was performed using an XRD (X-ray Diffractometer) (manufacturer: PANalytical, model name: EMPYREAN).

[0077] From the measured graph, the scattering vector is 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was calculated.

[0078] Light source (X-ray Source):Cu-Kα radiation Power: 45KV x 40mA Mode: Continuous scan mode Scan angle range: 0.1~2.0° Scan speed: 0.01° / sec

[0079] <Shrinkage rate> The polyethylene yarn was cut to obtain a sample with a length of 70 cm, and marks were made at points 10 cm apart from both ends of the sample (i.e., the distance between the marking points = 50 cm). Next, the sample was heated at 100°C for 30 minutes in a hot air circulating heating oven while hanging from a jig so that no load was applied to the sample. Thereafter, the sample was removed from the heating oven and gradually cooled to room temperature, and the distance between the marking points was measured. Next, the dry heat shrinkage of the polyethylene yarn at 100°C was calculated using the following formula.

[0080] Dry heat shrinkage rate (%)=[(L0-L1) / L0]×100 (Here, L0 is the distance between the marking points before heating (i.e., 50 cm), and L1 is the distance between the marking points after heating.)

[0081] The dry heat shrinkage values ​​obtained from the two tests were averaged.

[0082] [Example 1] <Production of polyethylene yarn> A polyethylene yarn containing 240 filaments and having a total denier of 500 was produced.

[0083] Specifically, 0.962 g / cm 3 Polyethylene chips having a density of 1.0, a weight average molecular weight (Mw) of 340,000 g / mol, a molecular weight distribution of 7.5, and a melt index (MI at 190°C) of 1.8 g / 10 min were fed into an extruder and melted. The molten polyethylene was extruded through a die having 240 holes. The ratio of the hole length L to the hole diameter D (L / D) in the die was 6. The die temperature was 260°C.

[0084] The filaments formed by being discharged from the nozzle holes of the spinneret were sequentially cooled in a cooling section consisting of three sections. In the first cooling section, they were cooled to 50°C by cooling air with a wind speed of 0.9 m / sec, in the second cooling section, they were cooled to 35°C by cooling air with a wind speed of 0.5 m / sec, and in the third cooling section, they were finally cooled to 25°C by cooling air with a wind speed of 0.4 m / sec. After cooling, they were bundled into a multifilament yarn by a bundler.

[0085] Next, the multifilament yarn was transferred to the drawing section. The drawing section was composed of a multi-stage drawing section consisting of four sections, and was composed of a total of four godet roller sections, each of which was composed of 2 to 10 godet rollers. The first godet roller section had a maximum temperature of 80°C, the second godet roller section had a maximum temperature of 90°C, the third godet roller section had a maximum temperature of 95°C, and the fourth godet roller section had a maximum temperature of 120°C. The draw ratio was set to 2 times in the first godet roller section, 3 times in the second godet roller section, and 1.4 times in the third godet roller section, and the fourth godet roller section was shrunk and drawn (relaxed) by 4% compared to the third godet roller section, so that the yarn was drawn and heat-set at a total draw ratio of 8 times.

[0086] The drawn multifilament yarn was then wound on a winder with a winding tension of 0.8 g / d.

[0087] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) was also measured and is shown in Figure 1. The scattering vector of small angle X-ray scattering (SAXS) was 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was 28.

[0088] [Example 2] <Production of polyethylene yarn> The yarn was prepared in the same manner as in Example 1, except that the total draw ratio was adjusted to 11 times.

[0089] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) was also measured and is shown in Figure 2. The scattering vector of small angle X-ray scattering (SAXS) was 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was 27.5.

[0090] [Example 3] <Production of polyethylene yarn> The yarn was prepared in the same manner as in Example 1, except that the total draw ratio was adjusted to 13 times.

[0091] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) was also measured and is shown in Figure 3. The scattering vector of small angle X-ray scattering (SAXS) was 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was 22.6.

[0092] [Example 4] <Production of polyethylene yarn> In the above Example 1, 0.961 g / cm 3 A raw yarn was produced in the same manner as in Example 1, except that polyethylene chips having a density of 1.0 g / mol, a weight average molecular weight (Mw) of 340,000 g / mol, a molecular weight distribution of 5.5, and a melt index (MI at 190° C.) of 1.7 g / 10 min were used, and the total draw ratio was adjusted to 13 times.

[0093] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) scattering vector: 0-0.04 Å -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was 16.

[0094] [Example 5] <Production of polyethylene yarn> In the above Example 1, 0.961 g / cm 3 A raw yarn was produced in the same manner as in Example 1, except that polyethylene chips having a density of 1.0, a weight average molecular weight (Mw) of 340,000 g / mol, a molecular weight distribution of 8, and a melt index (MI at 190° C.) of 1.6 g / 10 min were used, and the total draw ratio was adjusted to 13 times.

[0095] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) scattering vector: 0-0.04 Å -1 The highest point A of the intensity peak and the scattering vector 0.05 to 0.08 Å -1 The ratio (A / B) of the intensity peak generated at point A to the highest point B was 18.

[0096] [Comparative Example 1] <Production of polyethylene yarn> In the above Example 1, 0.960 g / cm 3 A raw yarn was produced in the same manner as in Example 1, except that polyethylene chips having a density of 1.0, a weight average molecular weight (Mw) of 340,000 g / mol, a molecular weight distribution of 3, and a melt index (MI at 190° C.) of 1.5 g / 10 min were used, and the total draw ratio was adjusted to 11 times.

[0097] The physical properties of the produced raw yarn were measured and are shown in Table 1 below. Small angle X-ray scattering (SAXS) was also measured and is shown in Figure 4. The scattering vector of small angle X-ray scattering (SAXS) was 0 to 0.04 Å. -1 The highest point A of the intensity peak and the scattering vector 0.05~0.08Å -1 The ratio (A / B) of the intensity peak occurring at point A to the highest point B was 15.

[0098] [Table 1]

[0099] Although the present invention has been described above with reference to specific and limited embodiments and drawings, these are merely provided for a more general understanding of the present invention, and the present invention is not limited to the above embodiments. Those skilled in the art will appreciate that various modifications and variations are possible from such descriptions.

[0100] Therefore, the spirit of the present invention should not be limited to the described embodiments, and all modifications equivalent to or equivalent to the scope of the claims, as well as the scope of the claims described below, can be said to fall within the spirit of the present invention.

Claims

1. melting polyethylene chips having a melt index (MI) of 0.3 to 6 g / 10 min measured at 190° C. and 2.16 kg and a molecular weight distribution of more than 5 and less than 9 to obtain a polyethylene melt; spinning the polyethylene melt through a die having a plurality of nozzle holes; cooling the plurality of filaments formed when the polyethylene melt is discharged from the nozzle holes; converging the cooled filaments to form a multifilament yarn; drawing and heat setting the multifilament yarn at a total draw ratio of 5 to 20 times; winding the drawn and heat-set multifilament yarn; Including, The step of cooling the plurality of filaments includes a step of performing multi-stage cooling in a cooling section having three cooling sections designed such that the temperature is gradually lower from the first cooling section to the third cooling section, Small angle X-ray scattering (SAXS) scattering vector 0-0.04 Å －１ The highest point A of the intensity peak occurring at 0.05 to 0.08 Å and the scattering vector －１ a ratio (A / B) of a peak intensity (Intensity Peak) occurring at a point A to a highest point B is 16 or more, and a shrinkage percentage is 2.5% or more.

2. The method for producing polyethylene yarn according to claim 1, wherein the spinning temperature of the polyethylene melt is 220 to 300°C.

3. The method for producing a polyethylene raw yarn according to claim 1, wherein the maximum drawing temperature during the drawing is 100 to 150°C.

4. The method for producing a polyethylene raw yarn according to claim 1 , wherein the drawing step is carried out by multi-stage drawing.

5. The method for producing a polyethylene raw yarn according to claim 4, wherein the multi-stage drawing is carried out using a plurality of godet rollers.

6. The method for producing a polyethylene raw yarn according to claim 4 , wherein the multistage drawing is performed in 4 stages or more and 20 stages or less.

7. The godet rollers are set at a temperature of 50 to 150° C. the temperature of the first godet roller of the plurality of godet rollers is 50 to 80° C.; the temperature of the last godet roller of the plurality of godet roller sections is 100 to 150° C.; 6. The method for producing a polyethylene raw yarn according to claim 5, wherein the temperature of each of the godet rollers, except for the first and last godet rollers, among the plurality of godet rollers is equal to or higher than the temperature of the godet roller located in the immediately preceding stage.

8. 3. The method for producing a polyethylene raw yarn according to claim 2, wherein the first cooling section cools the raw yarn to 40 to 80°C using cooling air at a speed of 0.8 to 1 m / sec, the second cooling section cools the raw yarn to 30 to 50°C using cooling air at a speed of 0.4 to 0.6 m / sec, and the third cooling section cools the raw yarn to 15 to 30°C using cooling air at a speed of 0.2 to 0.5 m / sec.

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