Method for manufacturing polyethylene yarn with improved post-processing properties and raw material containing the same.

Abstract

The present invention relates to a polyethylene yarn having improved post-processability, and more particularly to a polyethylene yarn having excellent mechanical properties even in harsh environments such as high temperatures, and having improved post-processability such as dyeing and coating. The polyethylene yarn according to the present invention can maintain a certain level of strength or more in high-temperature environments and have excellent post-processability.

Description

[Technical Field]

[0001] This invention relates to polyethylene yarn with improved post-processability and to a raw material containing the same. [Background technology]

[0002] Polyethylene resin is inexpensive, has excellent chemical resistance and processability, and is increasingly being used in engineering plastics, film fibers, and nonwoven fabrics. In the textile sector, it is manufactured from monofilaments and multifilaments, and its applications are expanding to clothing, industrial use, and more. In particular, in response to the latest trends in textiles, there is growing interest in high-performance polyethylene fibers that require high strength and high modulus of elasticity.

[0003] U.S. Patent No. 4,228,118 describes the production of 10-20 g / d fibers using polyethylene resin with a number-average molecular weight of 20,000 or more and a weight-average molecular weight of 125,000 or less. These fibers were wound at a spinning temperature of 220-335°C at a minimum spinning speed of 30 m / min, and then stretched more than 20 times. However, this method has limitations in the commercial production of polyethylene fibers due to the low number of nozzle holes and spinning speed using the spindraw method. It is difficult to produce polyethylene fibers with good uniformity and spinnability when producing tens to hundreds of multifilaments.

[0004] Generally, polyethylene fibers have inherent properties such as high strength, light weight, and chemical resistance, making them suitable for a wide range of applications including safety equipment, leisure goods, and household items. However, compared to polyethylene terephthalate fibers or polyamide fibers, which have relatively high melting points, polyethylene fibers have a low melting point, which means their physical properties tend to deteriorate at high temperatures, limiting the conditions for possible post-processing steps. There is an urgent need to develop polyethylene filaments that overcome these problems and maintain their mechanical properties even when post-processed at high temperatures. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide polyethylene filament yarn that maintains its mechanical properties even in high-temperature environments and has improved post-processability.

[0006] Furthermore, the objective is to provide a raw material with excellent mechanical properties, containing polyethylene filaments with improved post-processability. [Means for solving the problem]

[0007] The polyethylene filament according to the present invention has a melting index (MI) of 0.3 to 3 g / 10 min as measured according to ASTM D1238, a ratio (B / A) of strength (B) measured after heat treatment at 120°C for 30 minutes to strength (A) measured at room temperature according to ASTM D885 being 85% or more, and a ratio (C / A) of strength (C) measured after heat treatment at 50°C for 30 minutes to strength (A) measured at room temperature being 90% or more.

[0008] In the polyethylene filament according to one embodiment of the present invention, the polyethylene filament may have a degree of crystallinity of 60 to 85% (the same applies hereinafter).

[0009] In the polyethylene filament according to one embodiment of the present invention, the polyethylene filament may have a crystal size of 200 Å or more in the direction parallel to the fiber axis (002 plane) and a crystal size of 110 Å or more in the direction perpendicular to the fiber axis (110 plane), as measured by an X-ray diffraction pattern using CuKα rays.

[0010] In the polyethylene filament according to one embodiment of the present invention, the polyethylene filament may have a melting temperature of 130 to 140°C.

[0011] In a polyethylene yarn according to one embodiment of the present invention, the polyethylene yarn has a density of 0.93 to 0.97 g / cm³. 3 That's fine.

[0012] In a polyethylene yarn according to one embodiment of the present invention, the dry heat shrinkage rate of the polyethylene yarn is 2.5% or more.

[0013] In a polyethylene filament according to one embodiment of the present invention, the polyethylene filament may have a strength of 1 to 20 g / d as measured according to ASTM D2256.

[0014] In the polyethylene filament according to one embodiment of the present invention, the polyethylene filament may have a break elongation of 20% or less, as measured according to ASTM D2256.

[0015] The raw material according to the present invention includes the polyethylene raw yarn described above.

[0016] In the raw material according to one embodiment of the present invention, the wear resistance (cycles) of the raw material may be 500 or more. [Effects of the Invention]

[0017] The polyethylene yarn according to the present invention can maintain a certain level of strength or higher in a high-temperature environment and exhibit excellent post-processability.

[0018] Furthermore, the raw material according to the present invention, by containing polyethylene raw yarn with excellent post-processing properties, can maintain the excellent mechanical properties unique to polyethylene, and can be applied to a wide range of fields such as safety products, leisure products, household goods, or cooling materials. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram illustrating the measurement of the strength of polyethylene filament according to one embodiment of the present invention. [Modes for carrying out the invention]

[0020] Hereinafter, with reference to the drawings attached to the present invention, a preferred embodiment of the present invention will be described in detail. When explaining the present invention, specific explanations regarding related known functions or configurations will be omitted so as not to obscure the gist of the present invention.

[0021] The following specific examples or embodiments are merely one reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be realized in various forms.

[0022] In the present invention, unless otherwise defined, all technical terms and scientific terms have the meanings usually understood by those having ordinary knowledge in the technical field to which the invention pertains. The terms used in the description of the present invention are merely for effectively describing a specific embodiment and are not for limiting the present invention.

[0023] Also, the singular forms used in the specification may be intended to include plural forms as well, unless otherwise indicated by the context.

[0024] Also, when a certain part "includes" a certain component, this means that, unless otherwise stated, it does not exclude other components but may further include other components.

[0025] Hereinafter, the units used without particular mention are based on weight. As an example, the units of % or ratio mean weight % or weight ratio.

[0026] The present inventor noted that although polyethylene raw yarns have inherent properties such as high strength, light weight, and chemical resistance, and also have excellent cool feeling properties due to high crystallinity, their melting points are low and they are fragile at high temperatures, so the post-processing process is very difficult. Therefore, through in-depth research, it was found that when the polyethylene raw yarns meet specific melt index and strength conditions, high crystallinity and mechanical physical properties can be maintained even after post-processing, and the present invention was thus completed.

[0027] In this specification, polyethylene filament refers to monofilaments and multifilaments produced from polyethylene chips by processes such as spinning and drawing. For example, polyethylene filament may contain 40 to 500 filaments, each having a fineness of 1 to 3 denier, and may have a total fineness of 100 to 1,000 denier.

[0028] The polyethylene filament according to the present invention is characterized in that the melt index (MI, @190°C) measured at 190°C and 2.16 kg according to ASTM D1238 is 0.3 to 3 g / 10 min, the ratio of strength (B) measured after heat treatment at 120°C for 30 minutes to strength (A) measured at room temperature according to ASTM D885 (B / A) is 85% or more, and the ratio of strength (C) measured after heat treatment at 50°C for 30 minutes to strength (A) measured at room temperature (C / A) is 90% or more.

[0029] Specifically, the ratio (B / A) of the strength (A) measured after heat treatment at 120°C for 30 minutes to the strength (A) measured at room temperature may be 87% or more, and preferably 90% or more. Furthermore, the ratio (C / A) of the strength (C) measured after heat treatment at 50°C for 30 minutes to the strength (A) measured at room temperature may be 92% or more, and preferably 95% or more.

[0030] Furthermore, the melting index (MI) may be preferably 0.4–3 g / mol, and more preferably 0.7–3 g / mol.

[0031] Polyethylene yarns that meet these strength ratio and melt index requirements have the advantage of being advantageous for post-processing such as weaving and twisting, as they hardly experience any deterioration in physical properties even when exposed to high temperatures for extended periods.

[0032] Furthermore, the polyethylene filament may have a polydispersity index (PDI) of 1 to 20, specifically 3 to 15, more specifically 5 to 10, and a weight-average molecular weight (Mw) of 600,000 g / mol or less, specifically 80,000 to 500,000 g / mol, more specifically 200,000 to 400,000 g / mol. Polyethylene filament having the above-mentioned polydispersity index and weight-average molecular weight ensures good processability during melt extrusion, preventing thermal decomposition and preventing yarn breakage during stretching, thereby enabling the production of filament with uniform physical properties and providing a filament with excellent durability. Here, the number-average molecular weight is not limited as long as it can satisfy the above-mentioned PDI value with respect to the weight-average molecular weight.

[0033] Furthermore, the polyethylene filament may have a crystallinity of 60-90%, more preferably 60-85%, and even more preferably 65-85%, but is not limited thereto. The crystallinity of the polyethylene filament can be derived by analyzing its crystallinity using an X-ray diffraction analyzer. When the crystallinity is within the above range, heat is rapidly diffused and dissipated by lattice vibrations called "phonons" in the direction of the molecular chains linked by the covalent bonds of polyethylene, resulting in excellent thermal conductivity.

[0034] Furthermore, the polyethylene filament may satisfy the following conditions, as measured by X-ray diffraction patterns using CuKα rays: the crystal size in the direction parallel to the fiber axis (002 plane) is 200 Å or more, and the crystal size in the direction perpendicular to the fiber axis (110 plane) is 110 Å or more. Specifically, the crystal size in the direction parallel to the fiber axis may be 210 Å to 360 Å, more specifically 220 Å to 350 Å. Also, the crystal size in the direction perpendicular to the fiber axis may be 120 Å to 190 Å, preferably 130 Å to 180 Å, but is not limited to these. However, within the above range, the polyethylene filament can exhibit high strength and low shrinkage characteristics, satisfying excellent heat resistance and strength, and may also have improved heat absorption and thus improved coolness.

[0035] Furthermore, the polyethylene filament may have a melting temperature of 130-140°C. Specifically, it may be 138-140°C, but is not limited to this range. However, filament that meets the aforementioned melting temperature can maintain its mechanical properties even at relatively high temperatures.

[0036] Furthermore, the polyethylene yarn has a density of 0.93 to 0.97 g / cm³. 3 Specifically, 0.941-0.965 g / cm³ 3 It may also be the case that polyethylene filaments satisfying the aforementioned density maintain their mechanical properties even when exposed to high temperatures for extended periods, exhibiting high thermal resistance and low shrinkage.

[0037] Specifically, the polyethylene yarn may have a dry heat shrinkage rate of 1.5 to 3.5%, specifically 2 to 3%, or 2.5 to 3%.

[0038] Furthermore, the polyethylene filament may have a strength of 1 to 25 g / d as measured according to ASTM D2256. Preferably, it may be 1 to 20 g / d, and more preferably, 7 to 20 g / d. Polyethylene filament that satisfies the above strength is relatively flexible and can have excellent weaving properties, so when it is subsequently woven or knitted to produce a roll, a roll of superior quality can be obtained.

[0039] The following describes in detail the method for producing polyethylene filament yarn according to the present invention. The polyethylene filament yarn of the present invention is not limited to its production method as long as it satisfies the above-mentioned ranges of physical properties such as PDI, strength ratio, and strength, and the following describes one embodiment.

[0040] First, there is the step of melting polyethylene chips to obtain a polyethylene molten product, The steps include spinning the polyethylene molten material through a die having multiple nozzle holes, The steps include: cooling the multiple filaments formed when the polyethylene molten material is extruded from the nozzle hole, stretching them to a total stretch ratio of 5 to 20 times, and then heat-setting them; The process may also include the step of winding up the stretched and heat-fixed multifilament yarn.

[0041] To explain each step in detail, first, polyethylene in chip form is fed into an extruder and melted to obtain molten polyethylene.

[0042] The polyethylene chips may have a polydispersity index (PDI) greater than 5 and less than 9, preferably 5.5 to 8. They may also have a melt index (MI) of 0.3 to 3 g / 10 min, preferably 0.4 to 3 g / mol, and more preferably 0.7 to 3 g / mol. Furthermore, they may 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.

[0043] Molten polyethylene is transported 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 can be determined according to the DPF (Denier Per Filament) and fineness of the yarn to be produced. For example, when producing yarn with a total fineness of 75 deniers, the die may have 20 to 75 holes, and when producing yarn with a total fineness of 450 deniers, the die may have 90 to 450, preferably 100 to 400 holes.

[0044] The melting process within the extruder and the extrusion process via the die can be modified or applied according to the melting index of the polyethylene chips. Specifically, for example, these processes may be carried out at 150-315°C, preferably 220-300°C, and more preferably 250-290°C. In other words, it is preferable that the extruder and die be maintained at 150-315°C, preferably 220-300°C, and more preferably 250-290°C.

[0045] If the spinning temperature is less than 150°C, the polyethylene may not melt uniformly due to the low spinning temperature, making spinning difficult. This can lead to excessive shear stress in the nozzle, resulting in severe melt fracture. Conversely, if the spinning temperature exceeds 315°C, the thermal decomposition of polyethylene is accelerated, making it difficult to achieve the target level of physical properties. The ratio of the hole length (L) to the hole diameter (D) in the die (L / D) may be between 3 and 40. If L / D is less than 3, die swell occurs during melt extrusion, making it difficult to control the elastic behavior of polyethylene, resulting in poor spinnability. If L / D exceeds 40, necking of the molten polyethylene passing through the die may cause yarn breakage, along with uneven discharge due to pressure drop.

[0046] Molten polyethylene is extruded from the holes in the die, and the solidification of the polyethylene begins due to the difference between the spinning temperature and room temperature, forming a semi-solid filament. In this specification, both semi-solidified filaments and fully solidified filaments are referred to as "filaments."

[0047] Multiple filaments are completely solidified by being cooled in a cooling section (or "quenching zone"). The cooling of the filaments may be performed by air cooling.

[0048] Preferably, the filament cooling in the cooling section is performed using a cooling airflow with a wind speed of 0.2 to 1 m / sec to cool to 15 to 40°C. If the cooling temperature is less than 15°C, the elongation will be insufficient due to supercooling, and thread breakage may occur during the stretching process. If the cooling temperature exceeds 40°C, the deviation in fineness between filaments will become large due to uneven solidification, and thread breakage may occur during the stretching process.

[0049] Furthermore, by performing multi-stage cooling during the cooling process in the cooling section, crystallization can be made even more uniform.

[0050] More specifically, the cooling section is divided into two or more sections. For example, if it consists of three cooling sections, it is preferable that the temperature gradually decreases from the first cooling section to the third cooling section. Specifically, the first cooling section may be set to 40-80°C, the second cooling section to 30-50°C, and the third cooling section to 15-30°C.

[0051] Furthermore, by setting the air velocity in the first cooling section to the highest possible value, it is possible to produce fibers with a smoother surface. Specifically, the first cooling section may be cooled to 40 to 80°C using cooling air with an air velocity of 0.8 to 1 m / sec, the second cooling section may be cooled to 30 to 50°C using cooling air with an air velocity of 0.4 to 0.6 m / sec, and the third cooling section may be cooled to 15 to 30°C using cooling air with an air velocity of 0.2 to 0.5 m / sec. By adjusting the conditions in this way, it is possible to produce raw yarn with a higher degree of crystallinity and a smoother surface.

[0052] Next, a focusing machine is used to focus the cooled and completely solidified filaments to form a multifilament.

[0053] The polyethylene filament of the present invention may be manufactured by a direct spin-drawn (DSD) process. That is, the multifilament may be directly transferred to a multi-stage drawing section including multiple godet roller sections, and after being drawn in multiple stages with a total draw ratio of 5 to 20 times, preferably 8 to 15 times, it may be wound onto a winder.

[0054] As an example, the stretching step using the multiple godet rollers is preferably performed in two or more stages. Preferably, the stretching step may be performed in two to 20 stages using the multiple godet rollers. If the stretching is performed in fewer than two stages, rapid stretching occurs in each section of the godet roller, increasing the frequency of fluffing during filament yarn production, increasing the initial modulus, and potentially making the raw material excessively stiff. Also, if the stretching is performed in 20 or more stages, friction between the filament yarn and the godet roller increases, potentially causing filament damage and yarn breakage.

[0055] Furthermore, even if polyethylene chips having a polydispersity index (PDI) of 5 to 10 and a melt index (MI) of 0.3 to 3 g / 10 min at 190°C are used, the desired physical properties cannot be met if the stretch ratio, stretch temperature, and number of stages conditions according to the method of the present invention are not satisfied. For example, during the stretching, the maximum stretch temperature may be 100 to 150°C. If the stretch temperature is less than 100°C, the amount of heat transferred to the yarn is insufficient, the stretching efficiency decreases, and severe yarn breakage occurs. If it exceeds 150°C, fusion may occur in the filaments, reducing the strength of the yarn. The total stretch ratio may be 5 to 20 times, and multi-stage stretching of two or more stages may be performed. The maximum stretch temperature refers to the highest temperature during the stretching section, and the total stretch ratio refers to the final stretch ratio of the fiber after the last stretch compared to the fiber before stretching.

[0056] For example, the multi-stage stretching may be performed using multiple godet rollers in two or more stages, more specifically in four to twenty stages. The temperature of the first godet roller GR1 among the multiple 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, excluding the first and last godet roller sections (GR1, GRN), may be the same as or higher than the temperature of the godet roller immediately preceding it. The temperature of the last godet roller section GRn may be the same as or higher than the temperature of the godet roller immediately preceding it, but may also be set slightly lower.

[0057] Furthermore, during multi-stage stretching, applying a 1-5% shrinkage stretch (relaxation) in the final stretching section can provide a yarn with superior durability.

[0058] To give a more specific example, the multi-stage stretching may consist of a total of four godet roller sections, where the first godet roller section is set to stretch 2 to 4 times at 50 to 80°C, the second godet roller section is set to stretch 3 to 10 times at 70 to 100°C, the third godet roller section is set to stretch 1.1 to 3 times at 80 to 110°C, and the fourth godet roller section is set to shrink and stretch (relax) by 1 to 5% at 100 to 150°C. Each of the first to fourth godet roller sections may consist of multiple godet rollers. To give a specific example, it may consist of two or more, more specifically, two to ten godet rollers.

[0059] The polyethylene filament of the present invention may be produced by selectively winding the multifilament as an undrawn yarn and then drawing the undrawn yarn. That is, the polyethylene filament of the present invention may be produced by a two-step process in which polyethylene is melt-spun to produce an undrawn yarn, and then the undrawn yarn is drawn.

[0060] If the total stretch ratio applied to the stretching process is less than 5, the degree of fiber orientation will be low, making it difficult for the polyethylene filament to have a crystallinity of 60% or more, and thus making it difficult to achieve high strength.

[0061] In contrast, if the total stretch ratio exceeds 20 times, yarn breakage may occur, the strength of the resulting polyethylene yarn may not be suitable, the weaving properties of the polyethylene yarn may be poor, and the resulting fabric may become excessively stiff, causing inconvenience to the user.

[0062] 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 stretch ratio of 5 to 20 times, preferably 8 to 15 times, can be applied to the multifilament in the multi-stage stretching section.

[0063] The multi-stage stretching section simultaneously performs multi-stage stretching and heat fixing of the multifilament, and the multi-stage stretched multifilament is wound onto a winder to complete the polyethylene yarn of the present invention.

[0064] The polyethylene yarn produced according to the present invention as described above exhibits high strength retention, low shrinkage, and excellent heat resistance and strength retention even when applied to high temperatures, and can therefore be used in articles that require post-processing steps. For example, it can be used as a material for general clothing.

[0065] The raw material according to the present invention contains the polyethylene raw yarn described above, and by including raw yarn with improved post-processability, it can maintain the excellent mechanical properties unique to polyethylene, such as high strength, low shrinkage, coolness, and heat resistance, even after going through manufacturing processes for the raw material such as knitting and weaving. Therefore, it can be applied to a wide range of fields such as safety products, leisure products, household goods, or cooling materials.

[0066] Furthermore, by including yarn with improved post-processing properties, the resulting fabric can maintain its mechanical properties even during post-processing such as dyeing and coating.

[0067] Specifically, the raw material according to the present invention may have an abrasion resistance (cycles) of 500 or more, preferably 530 to 700, as measured according to the ASTM D3884 standard.

[0068] The raw material according to the present invention may use the aforementioned polyethylene filament alone, or it may further contain other types of filaments to provide other functionalities, but from the viewpoint of simultaneously having post-processability and cooling properties, it is preferable to use the polyethylene filament alone.

[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 illustrative examples for illustrating the present invention in more detail, and the present invention is not limited to the following examples and comparative examples.

[0070] The physical properties of the polyethylene filament were measured as follows.

[0071] <Melting Index> The measurement was performed according to ASTM D1238, with a measurement temperature of 190°C, a weight set to 2.16 kg, and the amount of flow measured over a 10-minute period.

[0072] <Weight-average molecular weight (Mw) (g / mol) and polydispersity index (PDI)> After completely dissolving the polyethylene filaments in the following solvents, the weight-average molecular weight (Mw) and polydispersity index (Mw / Mn; PDI) of the polyethylene filaments were determined using the following gel permeation chromatography (GPC).

[0073] -Analytical equipment: Tosoh HLC-8321 GPC / HT - Column: PLgel guard (7.5 x 50 mm) + 2 x PLgel mixed-B (7.5 x 50 mm) - Column temperature: 160℃ - 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: 1.5 mg / mL -Standard sample: Polystyrene

[0074] <Strength (g / d), initial modulus (g / d), and elongation rate (%)> Deformation-stress curves of polyethylene filaments were obtained using an Instron Engineering Corp. (Canton, Mass.) universal tensile testing machine according to the ASTM D2256 method. The sample length was 250 mm, the tensile speed was 300 mm / min, and the initial load was set to 0.05 g / d. Strength (g / d) and elongation (%) were determined from the stress and elongation at the fracture point, and the initial modulus (g / d) was determined from the tangent line giving the maximum slope near the origin of the curve. After five measurements for each filament, the average was calculated.

[0075] <Strong measurement> The strength (g / d) of polyethylene filaments was measured using an Instron Engineering Corp. (Canton, Mass) universal tensile testing machine according to the ASTM D885 method. The sample length was 250 mm, the tensile speed was 300 mm / min, and the initial load was set to 0.05 g / d.

[0076] As shown in Figure 1, after cutting polyethylene filaments to obtain samples 200 with a length of 250 mm or more, the samples were passed through a cylindrical glass tube 100 with both ends open, and then both ends of the samples were fixed to both ends of the glass tube.

[0077] During this process, no load was applied to the sample. Then, using a hot air circulation type heating furnace, the sample was heated at the test temperature (50°C, 120°C) for 30 minutes, and the strength of the yarn sample was measured. Afterward, the sample was removed from the heating furnace and gradually cooled to room temperature (20±5°C), and the strength of the yarn sample was measured again. The strength was measured a total of five times, and the average value was calculated.

[0078] Next, the ratio of strength was calculated using the following formula.

[0079] [formula] Strength ratio (%) = (Strength of polyethylene yarn at high temperature (B or C)) / (Strength of polyethylene yarn at room temperature (A)) × 100

[0080] In the above formula, the high temperature may be the test temperature, specifically 50°C or 120°C.

[0081] <Degree of crystallinity of the raw yarn> The degree of crystallinity of polyethylene filaments was measured using an XRD instrument (X-ray Diffractomer) [Manufacturer: PANalytical, Model: EMPYREAN]. Specifically, polyethylene filaments were cut to prepare a sample with a length of 2.5 cm, and after fixing the sample in a sample holder, measurements were performed under the following conditions.

[0082] -Light source (X-ray Source):Cu-Kα radiation -Power: 45kV × 25mA - Mode: Continuous scan mode - Scan angle range (2Θ): 10~40° - Scan speed: 0.1° / sec -Calculation of crystallinity Crystallinity (%) = I C / (I A +I C )×100

[0083] In the 2Θ range scanned using XRD, the fraction of the crystalline region of polyethylene is I C and the fraction of the amorphous region is I A . The crystallinity is shown as the ratio of the fraction of the crystalline region to the sum of the fractions of the crystalline and amorphous regions of polyethylene.

[0084] <Dry heat shrinkage rate> Leave the sample in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours. After heat shrinking under the condition of 150°C × 30 minutes without tension, leave the sample in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours. It shows the length change before and after the shrinkage of the raw yarn.

[0085] Shrinkage rate (%) = (L0 - L1) / L0 × 100 L0: The length of the sample after leaving it in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours before heat shrinkage L1: The length of the sample after leaving it in a constant temperature and humidity chamber at 25°C and 65% relative humidity for 24 hours after heat shrinkage

[0086] <Evaluation of abrasion resistance> The abrasion resistance of the knitted fabric manufactured by knitting using the polyethylene raw yarn according to the present invention was measured according to the ASTM D3884 standard. As the evaluation equipment, a Martindale abrasion tester was used. The friction cloth used at this time was 320Cw sandpaper, and the applied load was 1,000 g.

[0087] [Example 1] A polyethylene raw yarn containing 240 filaments and having a total fineness of 500 denier was produced.

[0088] Specifically, 0.962 g / cm 3Polyethylene chips having a density of 340,000 g / mol, a weight-average molecular weight (Mw) of 7.5, a polydispersity index (PDI) of 7.5, and a melting index (MI) of 1.8 g / 10 min at 190°C were fed into an extruder and melted. The molten polyethylene was extruded through a die with 240 holes. The ratio of hole length to hole diameter (L / D) in the die was 5. The die temperature was 270°C.

[0089] The filament formed by extrusion from the nozzle hole of the die moved to the cooling section and the stretching section. The cooling section and the stretching section each consisted of four sections, and the multifilament yarn was cooled and stretched sequentially. The first cooling section cooled to 50°C, the second and third cooling sections cooled to 45°C, and the fourth cooling section cooled to 40°C. The stretching section consisted of a total of four godet roller sections, each godet roller section consisting of 1 to 10 godet rollers. The first godet roller section was set to a maximum temperature of 80°C, the second godet roller section to a maximum temperature of 90°C, the third godet roller section to a maximum temperature of 95°C, and the fourth godet roller section to a maximum temperature of 120°C. The stretch ratio was set to be 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. The fourth godet roller section underwent 4% shrinkage (relaxation) compared to the third godet roller section, resulting in a total stretch and heat fixation with a total stretch ratio of 8 times.

[0090] Next, the stretched multifilament yarn was wound onto a winder. The winding tension was 0.8 g / d.

[0091] The physical properties of the manufactured yarn were measured and are shown in Table 1 below.

[0092] Furthermore, the strength (A) of the raw yarn produced at room temperature was measured, and the strength (B) of the raw yarn produced as described above after heat treatment at 120°C for 30 minutes was measured.

[0093] The ratio of strength (B) measured after heat treatment at 120°C for 30 minutes to strength (A) measured at room temperature (B) (B / A), and the ratio of strength (C) measured after heat treatment at 50°C for 30 minutes to strength (A) measured at room temperature (C / A) (C / A) were calculated and are shown in Table 1.

[0094] <Manufacturing of raw materials> Knitted fabric was manufactured by knitting using the polyethylene yarn produced as described above. The physical properties of the manufactured knitted fabric were measured and are shown in Table 2 below.

[0095] [Examples 2-3] The manufacturing process was the same as in Example 1, except that the conditions were changed as shown in Table 1 below.

[0096] Furthermore, the physical properties of the raw material manufactured in the same manner as in Example 1 were measured and are shown in Table 2 below.

[0097] [Example 4] In the above-described embodiment 1, the cooling section and the stretching section each consisted of two sections, specifically, the first cooling section cooled to 50°C and the second cooling section cooled to 40°C, the stretching section consisted of a total of two godet roller sections, the first godet roller section was set to a maximum temperature of 80°C and the second godet roller section to a maximum temperature of 120°C, and the stretching ratio was adjusted so that the first godet roller section was stretched 4.4 times and the second godet roller section was stretched 3 times, resulting in a total stretching ratio of 13 times. Except for these adjustments, the raw yarn was manufactured in the same manner as in embodiment 1.

[0098] [Example 5] In Example 1, 0.961 g / cm³ 3 The yarn was produced in the same manner as in Example 1, except that polyethylene chips having a density of 340,000 g / mol, a weight-average molecular weight (Mw), a polydispersity index (PDI) of 5.5, and a melting index (MI at 190°C) of 1.7 g / 10 min, were used, and the total stretch ratio was adjusted to 13 times.

[0099] [Example 6] In Example 1, 0.961 g / cm³ 3 The yarn was produced in the same manner as in Example 1, except that polyethylene chips having a density of 340,000 g / mol, a weight-average molecular weight (Mw), a polydispersity index (PDI) of 8, and a melting index (MI at 190°C) of 1.6 g / 10 min, were used, and the total stretch ratio was adjusted to 13 times.

[0100] [Comparative Example 1] In the above Example 1, 0.960 g / cm³ 3 The yarn was manufactured in the same manner as in Example 1, except that polyethylene chips having a density of 200,000 g / mol, a weight-average molecular weight (Mw), a polydispersity index (PDI) of 7.5, and a melting index (MI at 190°C) of 5 g / 10 min were used, and the total stretch ratio was adjusted to 11 times.

[0101] Furthermore, the physical properties of the raw material manufactured in the same manner as in Example 1 were measured and are shown in Table 2 below.

[0102] [Table 1]

[0103] [Table 2]

Claims

1. A step of melting polyethylene chips to obtain a polyethylene molten product, The steps include spinning the polyethylene molten material through a die having multiple nozzle holes, The steps include: cooling the multiple filaments formed when the polyethylene molten material is extruded from the nozzle hole, stretching them to a total stretch ratio of 5 to 20 times, and then heat-fixing them; A method for producing polyethylene filament yarn, comprising the steps of winding up the stretched and heat-fixed multifilament yarn, The polyethylene chips have a polydispersity index of 5 to 10 and a melting index of 0.3 to 3 g / 10 min at 190°C. During the stretching process, the maximum stretching temperature is 100 to 150°C, and multi-stage stretching of two or more stages is performed. The melting index (MI) measured according to ASTM D1238 was 0.3–3 g / 10 min. The ratio (B / A) of the strength (A) measured after heat treatment at 120°C for 30 minutes to the strength (A) measured at room temperature according to ASTM D885 is 85% or higher. A method for producing polyethylene filament yarn, wherein the ratio (C / A) of the strength (C) measured after heat treatment at 50°C for 30 minutes to the strength (A) measured at room temperature is 90% or more.

2. The method for producing polyethylene filamentary yarn according to claim 1, wherein the polyethylene filamentary yarn has a degree of crystallinity of 60 to 85%.

3. The method for producing polyethylene filament according to claim 1, wherein the polyethylene filament is such that, as measured by an X-ray diffraction pattern using CuKα rays, the crystal size in the direction parallel to the fiber axis (002 plane) is 200 Å or more, and the crystal size in the direction perpendicular to the fiber axis (110 plane) is 110 Å or more.

4. The method for producing polyethylene filamentary yarn according to claim 1, wherein the polyethylene filamentary yarn has a melting temperature of 130 to 140°C.

5. The aforementioned polyethylene yarn has a density of 0.93 to 0.97 g / cm³. ３ The method for producing polyethylene yarn according to claim 1.

6. The method for producing polyethylene filament yarn according to claim 1, wherein the dry heat shrinkage rate of the polyethylene filament yarn is 2.5% or more.

7. The method for producing polyethylene filamentary yarn according to claim 1, wherein the polyethylene filamentary yarn has a strength of 1 to 20 g / d as measured according to ASTM D2256.

8. The method for producing polyethylene filamentary yarn according to claim 1, wherein the polyethylene filamentary yarn has a break elongation of 20% or less as measured according to ASTM D2256.

9. A method for manufacturing a raw material, comprising a method for manufacturing polyethylene raw yarn according to any one of claims 1 to 8.

10. The method for manufacturing the raw material according to claim 9, wherein the raw material has an abrasion resistance of 500 cycles or more.

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