Cut resistant polyethylene yarn, method of making and protective articles made therewith

Abstract

The present invention relates to a polyethylene yarn capable of manufacturing a protective article having high cut resistance and capable of providing excellent wearing feeling, a manufacturing method thereof, and a protective article manufactured using the same. The polyethylene yarn of the present invention has high strength although manufactured by melt spinning, thereby capable of manufacturing a protective article having high cut resistance index. In addition, the polyethylene yarn of the present invention has low initial modulus and high elongation, and thus capable of producing a protective article having excellent wearing feeling.

Description

[0001] This case is a divisional application, the parent application being the application filed on March 20, 2020, entitled "Cut-resistant polyethylene yarn, method of manufacturing the same and protective article made therefrom", with application number 202080022462.7. Technical Field

[0002] This invention relates to a cut-resistant polyethylene yarn, a method for manufacturing the same, and protective articles made using the same. More specifically, it relates to a polyethylene yarn capable of producing protective articles that have high cut resistance while providing excellent wearability, a method for manufacturing the same, and protective articles made using the same. Background Technology

[0003] Personnel working in security fields, such as police officers and military personnel, as well as those handling sharp cutting tools in various other industries, are always exposed to the risk of injury. Protective equipment such as gloves or clothing should be provided to minimize this risk.

[0004] To properly protect the human body from weapons or sharp cutting tools (such as knives), protective items need to be cut-resistant.

[0005] To provide high cut resistance to protective items, high-strength polyethylene yarn is used in their manufacture. For example, high-strength polyethylene yarn can be used alone to make fabrics, or it can be used together with other types of yarn (multiple) to form a ply yarn, which can then be used to make fabrics.

[0006] Ultra-high molecular weight polyethylene (UHMWPE), a type of high-strength polyethylene yarn, is generally made from linear polyethylene with a weight-average molecular weight of 600,000 g / mol or higher. Due to its high melt viscosity, UHMWPE can only be manufactured via gel spinning. For example, UHMWPE solution can be prepared by polymerizing ethylene in an organic solvent in the presence of a catalyst. The solution is then spun and cooled to form a gel in fibrous form, which can be stretched to obtain high-strength and high-modulus polyethylene yarn. However, this gel spinning method requires the use of organic solvents, which not only causes environmental problems but also incurs significant costs for solvent recovery.

[0007] Generally, high-density polyethylene (HDPE), being linear polyethylene with a weight-average molecular weight of 20,000 to 600,000 g / mol, has a relatively lower melt viscosity than UHMWPE, making it melt-spun and thus overcoming the environmental and high-cost problems inherent in gel spinning. However, due to its relatively lower molecular weight compared to UHMWPE, the strength of HDPE yarn is inevitably lower than that of UHMWPE yarn.

[0008] Therefore, continuous efforts have been made to improve the strength of high-density polyethylene yarn, so that even using polyethylene yarn manufactured by melt spinning, it is possible to produce protective items with satisfactory cut resistance.

[0009] However, while high-density polyethylene yarns developed solely for increased strength can provide satisfactory cut resistance for protective gear, they lead to a serious problem of poor wearability. In other words, protective gloves or clothing made from polyethylene yarns become too stiff, which hinders the wearer's movement (e.g., finger movement in the case of gloves) and reduces work efficiency. This poor wearability leads to avoidance of wearing protective gear and increases the risk of injury. Summary of the Invention

[0010] Technical issues

[0011] This invention relates to a cut-resistant polyethylene yarn, a method of manufacturing the same, and protective articles made using the same, which can prevent problems caused by the limitations and disadvantages of the prior art.

[0012] One aspect of the present invention is to provide a polyethylene yarn that can be used to manufacture protective articles that have high cut resistance while providing excellent wearability.

[0013] Another aspect of the present invention is to provide a method for manufacturing polyethylene yarn, which can produce protective articles that have high cut resistance while providing excellent wearability.

[0014] Another aspect of the present invention is to provide a protective article that can have high cut resistance while providing excellent wearability.

[0015] The above and other objects, features and advantages of the present invention will be set forth below, or will be clearly understood by those skilled in the art from such description.

[0016] Technical solution

[0017] According to one aspect of the invention, a polyethylene yarn is provided having a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol, an initial modulus of 100 g / d to 250 g / d, and an elongation of 6% to 10%.

[0018] Polyethylene yarns can have an initial modulus of 120 g / d to 200 g / d.

[0019] The dry heat shrinkage rate of polyethylene yarn at 100℃ can be greater than 2.5% and less than 6.0%.

[0020] The ratio of the storage elastic modulus of polyethylene yarn at 50°C to that at 30°C can be 65% to 75%, the ratio at 80°C to that at 30°C can be 30% to 45%, and the ratio at 105°C to that at 30°C can be 10% to 25%.

[0021] The polyethylene yarn may include 40 to 500 filaments, each of which has a fineness of 1 denier to 3 denier, and the polyethylene yarn may have a total fineness of 100 denier to 1,000 denier.

[0022] According to another aspect of the present invention, a method for manufacturing polyethylene yarn is provided, comprising the following steps:

[0023] Polyethylene chips with a melt index (MI) of 0.3 to 3 g / 10 min at 190 °C are melted to obtain polyethylene melt;

[0024] Polyethylene melt is extruded through a spinneret with multiple nozzle holes;

[0025] The multiple filaments formed when the polyethylene melt is discharged from the nozzle orifice are cooled;

[0026] The cooled filaments are brought together to form multifilament yarn;

[0027] Multifilament yarns are stretched and heat-set with a total stretch ratio of 8 to 20 times; and

[0028] The stretched and heat-set multifilament yarns are then wound.

[0029] The stretching process is performed in a multi-stage stretching manner, and the relaxation rate at the final stretch is 3% to 8% during the multi-stage stretching process.

[0030] Polyethylene chips can have a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol.

[0031] The stretching step can be performed using multiple guide rollers.

[0032] Heat setting of multifilament yarns can be performed using multiple guide rollers.

[0033] According to another aspect of the present invention, a protective article woven from covered yarn is provided, the covered yarn comprising:

[0034] The aforementioned polyethylene yarn;

[0035] Polyurethane yarn, wherein the polyurethane yarn spirally surrounds a polyethylene yarn; and

[0036] Polyamide yarn or polyester yarn, wherein the polyamide yarn or polyester yarn spirally surrounds the polyethylene yarn.

[0037] Among them, protective items have a cut resistance index of 5.0 or higher and a stiffness of 5.0gf or lower.

[0038] Protective equipment can have a cut resistance index of 5.5 to 8.5 and a stiffness of 2.0 gf to 5.0 gf.

[0039] The dry heat shrinkage rate of polyethylene yarn at 100℃ can be greater than 2.5% and less than 6%.

[0040] The weight of polyethylene yarn can be 45% to 85% of the total weight of the covering yarn, the weight of polyurethane yarn can be 5% to 30% of the total weight of the covering yarn, and the weight of polyamide yarn or polyester yarn can be 5% to 30% of the total weight of the covering yarn.

[0041] The above general description of the present invention is for illustration or explanation only and does not limit the scope of the invention.

[0042] Beneficial effects

[0043] Although the polyethylene yarn of the present invention is manufactured by melt spinning, it still has a high strength of 11 g / d or more, thereby enabling the manufacture of protective articles with a high cut resistance index of 5 or more, more preferably 5.5 to 8.5.

[0044] Furthermore, the polyethylene yarn of the present invention has a low initial modulus of less than 250 g / d and a high elongation of more than 6%, thus enabling the manufacture of protective articles with a low stiffness (i.e., excellent wearability) of less than 5 gf, more preferably 2 to 5 gf. Attached Figure Description

[0045] The accompanying drawings are included herein to provide a further understanding of the invention and are incorporated in and constitute a part of this application. The drawings illustrate embodiments of the invention and, together with the description, serve to illustrate the principles of the invention.

[0046] Figure 1 An apparatus for manufacturing polyethylene yarn according to an embodiment of the present invention is illustrated schematically.

[0047] Figure 2 and Figure 3 A method for measuring the strength of protective gloves is shown.

[0048] <Explanation of Figure Markers>

[0049] 100: Extruder; 200: Spinneret

[0050] 300: Cooling section; 400: Convergence section

[0051] 500: Stretching section; 600: Entanglement device

[0052] 700: Winding machine

[0053] 20: Protective gloves

[0054] 21: Sample of protective gloves

[0055] 21a: The side adjacent to the fingers of the glove

[0056] 21b: The side adjacent to the wrist of the glove

[0057] f1: Outside of the glove

[0058] f2: Inside of the glove

[0059] 31: Sample holder

[0060] 32: Sample press Detailed Implementation

[0061] Various embodiments of the polyethylene yarn of the present invention will be described in detail below.

[0062] The polyethylene yarn of the present invention is used to manufacture protective articles requiring high cut resistance (e.g., protective gloves) and is manufactured by melt spinning. The polyethylene yarn of the present invention may have a weight-average molecular weight (Mw) of 80,000 g / mol to 180,000 g / mol, an initial modulus of 100 g / d to 250 g / d, and an elongation of 6% to 10%.

[0063] Previous studies that overemphasized the cut resistance of protective items proposed increasing the initial modulus of polyethylene yarn, for example, to over 300 g / d, and reducing the elongation, for example, to below 6%.

[0064] However, according to the present invention, the cut resistance of the protective article is mainly determined by the strength of the polyethylene yarn, the slippage property of the polyethylene yarn (i.e., the property that a knife or sharp tool slides along the surface of the polyethylene yarn without being caught by the yarn), and the winding property of the fibers constituting the yarn (i.e., the property that the fibers twist or curl around the longitudinal axis of the yarn when a knife or sharp tool passes through the yarn), and it is determined that once the initial modulus and elongation of the polyethylene yarn reach a certain level, they no longer have a substantial impact on the cut resistance of the protective product.

[0065] Conversely, if the initial modulus of the polyethylene yarn is too high and / or the elongation of the polyethylene yarn is too low, the fabric made from such polyethylene yarn will have high stiffness. Due to poor coverage and weaving properties, the wearability of protective products will be significantly reduced, and the yield rate may be lower.

[0066] Therefore, the inventors have confirmed through experiments that when the initial modulus of polyethylene yarn is 100 g / d to 250 g / d, the elongation is 6% to 10%, and the weight-average molecular weight is 80,000 g / mol to 180,000 g / mol, it has excellent strength and cut resistance index, while having low stiffness, thus improving wearability, thereby completing the present invention.

[0067] One embodiment of the polyethylene yarn has a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol, or 120,000 g / mol to 160,000 g / mol, or 140,000 to 160,000 g / mol, which can achieve high strength.

[0068] Meanwhile, one embodiment of the polyethylene yarn has an initial modulus of 100 g / d to 250 g / d and an elongation of 6% to 10%, which enables a high cut resistance index and excellent wearability.

[0069] Specifically, the initial modulus of the polyethylene yarn can be above 100 g / d, or above 120 g / d, or above 150 g / d; and below 250 g / d, or below 230 g / d, or below 200 g / d. For example, the initial modulus of the polyethylene yarn can be from 100 g / d to 250 g / d, or from 100 g / d to 230 g / d, or from 100 g / d to 200 g / d, or from 120 g / d to 250 g / d, or from 120 g / d to 230 g / d, or from 120 g / d to 200 g / d, or from 150 g / d to 250 g / d, or from 150 g / d to 230 g / d, or from 150 g / d to 200 g / d.

[0070] When the initial modulus of polyethylene yarn is greater than 250 g / d or the elongation is less than 6%, the fabric made from polyethylene yarn has a high stiffness of more than 5 gf, which makes the fabric too stiff and may make the wearer of the protective product feel uncomfortable.

[0071] When the initial modulus of polyethylene yarn is less than 100 g / d or the elongation is greater than 10%, the cut resistance decreases as users continuously use protective products made from polyethylene yarn, which may cause pilling in the fabric or even damage the fabric.

[0072] Meanwhile, the polyethylene yarn of the present invention has a dry heat shrinkage rate of greater than 2.5% and less than 6% at 100°C.

[0073] Specifically, the dry heat shrinkage rate of polyethylene yarn at 100°C can be greater than 2.5%, or greater than 2.8%, or greater than 3.0%; and less than 6.0%, or less than 5.0%, or less than 4.0%, or less than 3.5%. For example, the dry heat shrinkage rate of polyethylene yarn at 100°C can be greater than 2.5% and less than 6.0%, or greater than 2.5% and less than 5.0%, or greater than 2.5% and less than 4.0%, or greater than 2.5% and less than 3.5%, or 2.8% to 6.0%, or 2.8% to 5.0%, or 2.8% to 4.0%, or 2.8% to 3.5%, or 3.0% to 6.0%, or 3.0% to 5.0%, or 3.0% to 4.0%, or 3.0% to 3.5%.

[0074] When the dry heat shrinkage rate is below 2.5%, the initial modulus of the yarn exceeds 250 g / d, which may worsen the wearability of protective items. On the other hand, when the dry heat shrinkage rate exceeds 6%, there is a high risk that finished products (e.g., protective gloves) made from such yarns will deform due to shrinkage. According to one embodiment of the invention, by selecting polyethylene raw materials with an appropriate molecular weight and appropriately adjusting the stretching conditions, the dry heat shrinkage rate of polyethylene yarn can be adjusted to be greater than 2.5% and less than 6%.

[0075] The ratio of the storage elastic modulus of the polyethylene yarn at 50°C to that at 30°C (hereinafter referred to as "storage elasticity retention rate at 50°C") of the present invention can be 65% to 75%, or 68% to 75%.

[0076] The ratio of the storage modulus of elasticity of polyethylene yarn at 80°C to that at 30°C (hereinafter referred to as "storage elasticity retention rate at 80°C") can be 30% to 45%, or 35% to 45%, or 37% to 45%.

[0077] Furthermore, the ratio of the storage modulus of elasticity of the polyethylene yarn at 105°C to that at 30°C (hereinafter referred to as "storage elasticity retention rate at 105°C") can be 10% to 25%, or 15% to 25%, or 20% to 25%.

[0078] By selecting polyethylene raw materials with appropriate molecular weight, the storage elasticity retention rate of polyethylene yarn can be adjusted within the aforementioned ranges.

[0079] When the elasticity retention rate at 50°C is less than 65%, or at 80°C it is less than 30%, or at 105°C it is less than 10%, the strength of the yarn decreases to less than 11 g / d, making it difficult to manufacture protective products with satisfactory cut resistance.

[0080] On the other hand, if the elasticity retention rate at 50°C exceeds 75%, or at 80°C exceeds 45%, or at 105°C exceeds 25%, the initial modulus of the yarn exceeds 250 g / d. Therefore, the wearability of the protective clothing may be reduced and the shrinkage rate may be reduced.

[0081] Meanwhile, the polyethylene yarn of the present invention can be a multifilament yarn, which is a bundle of 40 to 500 continuous filaments. Each of the continuous filaments can have a fineness of 1 denier to 3 denier, and the polyethylene yarn can have a total fineness of 100 denier to 1,000 denier.

[0082] Furthermore, the polyethylene yarn of the present invention can have a polydispersity index (PDI) greater than 5 and less than 9 for protective articles manufactured using this yarn. The polydispersity index (PDI) is the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), also known as the molecular weight distribution index (MWD).

[0083] Furthermore, the strength of the polyethylene yarn of the present invention can be 11 g / d or more, preferably 11 g / d to 18 g / d, so that protective articles made using the yarn can have a cut resistance index of 5 or more.

[0084] Meanwhile, according to another embodiment of the present invention, a method for manufacturing polyethylene yarn can be provided, the method comprising the following steps:

[0085] Polyethylene chips with a melt index (MI) of 0.3 g / 10 min to 3 g / 10 min (at 190 °C) are melted to obtain polyethylene melt;

[0086] Polyethylene melt is extruded through a spinneret with multiple nozzle holes;

[0087] The multiple filaments formed when the polyethylene melt is discharged from the nozzle orifice are cooled;

[0088] The cooled filaments are brought together to form multifilament yarn;

[0089] Multifilament yarns are stretched and heat-set with a total draw ratio of 8 to 20 times; and

[0090] The stretched and heat-set multifilaments are then wound.

[0091] The stretching step is performed in a multi-stage stretching manner, and the relaxation rate at the final stretch is 3% to 8% during the multi-stage stretching process.

[0092] In the following text, reference will be made to the appendix. Figure 1 A method for manufacturing polyethylene yarn according to an embodiment of the present invention is described in detail.

[0093] A method for manufacturing polyethylene yarn may include melting polyethylene chips with a melt index (MI) of 0.3 g / 10 min to 3 g / 10 min (at 190°C) to obtain polyethylene melt.

[0094] For example, polyethylene melt is obtained by first introducing polyethylene chips into an extruder 100 and melting them.

[0095] In the method of this invention, the melt index (MI) of the polyethylene (hereinafter referred to as "polyethylene chips") used as a raw material is from 0.3 g / 10 min to 3 g / 10 min. In this specification, the melt index of the polyethylene chips is a value measured at 190°C.

[0096] When the melt index (MI) of polyethylene chips is less than 0.3 g / 10 min, the high viscosity and low fluidity of the polyethylene melt make it difficult to ensure smooth flow in the extruder 100, causing the spinning unit to overload and process control to be inadequate, thus making it difficult to ensure the uniformity of yarn properties. On the other hand, when the melt index (MI) of polyethylene chips exceeds 3 g / 10 min, the fluidity of the polyethylene melt in the extruder 100 is relatively good, but due to the low molecular weight of polyethylene, it is difficult to obtain yarns with high strength properties of 11 g / d or higher.

[0097] The weight-average molecular weight (Mw) of polyethylene chips can be above 80,000 g / mol, above 100,000 g / mol, or above 120,000 g / mol. When the weight-average molecular weight (Mw) is less than 80,000 g / mol, the resulting yarn is unlikely to have a strength of more than 11 g / d.

[0098] Meanwhile, if the weight-average molecular weight (Mw), which is typically inversely related to the melt index (MI), is too high, exceeding 180,000 g / mol, the spinning equipment will be overloaded due to the high melt viscosity, and process control cannot be properly implemented, making it difficult to ensure the excellent properties of the yarn. Therefore, the weight-average molecular weight (Mw) of polyethylene chips is preferably below 180,000 g / mol, or below 170,000 g / mol, or below 160,000 g / mol.

[0099] However, considering that the molecular weight may decrease slightly due to the thermal decomposition of polyethylene during spinning, the upper limit of the weight-average molecular weight (Mw) of polyethylene chips can be slightly higher than the upper limit of the target molecular weight (i.e., the weight-average molecular weight of the polyethylene yarn in this invention, which is 80,000 to 180,000 g / mol).

[0100] The polyethylene chips of the present invention can have an initial modulus of 100 g / d to 250 g / d and an elongation of 6% to 10%.

[0101] The polyethylene chips of the present invention can have a polydispersity index (PDI) greater than 5 and less than 9.

[0102] Meanwhile, one embodiment of the method for manufacturing polyethylene yarn may include extruding polyethylene melt through a spinneret having a plurality of nozzle holes.

[0103] The polyethylene melt is fed through a screw in an extruder 100 to a spinneret 200 having multiple nozzle orifices, and then extruded through the nozzle orifices. The number of nozzle orifices in the spinneret 200 can be determined based on the DPF (denier per filament) and total fineness of the yarn to be manufactured. According to one embodiment of the invention, to manufacture a yarn with a DPF of 1 to 3 and a total fineness of 100 to 1,000, the spinneret 200 may have 40 to 500 nozzle orifices.

[0104] The melting process in the extruder 100 and the extrusion process through the spinneret 200 are performed at 150°C to 315°C, preferably 250°C to 315°C, and more preferably 260°C to 290°C. That is, the extruder 100 and the spinneret 200 are maintained at 150°C to 315°C, preferably 250°C to 315°C, and more preferably 260°C to 290°C. According to one embodiment of the invention, polyethylene chips are introduced into the extruder 100, and the space from which they move until they are discharged through the nozzle orifice of the spinneret 200 is divided into multiple sections, thereby controlling the temperature of each section. For example, the temperature of each section can be controlled within a temperature range of 150°C to 315°C, preferably 250°C to 315°C, and more preferably 260°C to 290°C, such that the temperature of the section at a later stage is equal to or greater than the temperature of the section at a earlier stage.

[0105] When the spinning temperature is below 150°C, the polyethylene chips cannot be uniformly melted due to the low spinning temperature, making spinning difficult. Meanwhile, when the spinning temperature exceeds 315°C, it causes thermal decomposition of the polyethylene, making it difficult to exhibit high strength.

[0106] The ratio of orifice length L to orifice diameter D in the spinneret 200, L / D, can be between 3 and 40. When L / D is less than 3, dieswell occurs during melt extrusion, making it difficult to control the elastic behavior of polyethylene and resulting in poor spinnability. When L / D exceeds 40, yarn breakage may occur due to necking of the polyethylene melt passing through the spinneret 200, and irregular discharge may also occur due to pressure drop.

[0107] Meanwhile, one embodiment of the method for manufacturing polyethylene yarn may include multiple filaments formed when cooled polyethylene melt is discharged from a nozzle orifice.

[0108] When the polyethylene melt is discharged from the nozzle orifice of the spinneret 200, due to the difference between the spinning temperature and room temperature, the polyethylene melt begins to solidify and forms multiple filaments 11 in a semi-solid state. In this specification, both semi-solid and fully solidified filaments are collectively referred to as "filaments".

[0109] Multiple filaments 11 are fully cured by cooling in a cooling section (or quenching zone) 300. Cooling of the filaments 11 can be performed by air cooling. For example, cooling air with a wind speed of 0.2 m / sec to 1 m / sec can be used to cool the filaments 11 at a temperature between 15°C and 40°C. When the cooling temperature is below 15°C, insufficient elongation due to overcooling may cause yarn breakage during subsequent stretching. When the cooling temperature exceeds 40°C, irregular curing leads to increased fineness deviation between the filaments 11, and yarn breakage may occur during stretching.

[0110] Meanwhile, one embodiment of the method for manufacturing polyethylene yarn may include bringing together multiple cooled filaments to form a multifilament yarn.

[0111] For example, the cooled and fully cured filaments 11 are gathered together using a gathering device 400 to form multifilament yarns 10.

[0112] like Figure 1 As shown, before forming the multifilament yarn 10, an oiling process can be further performed, in which oil is applied to the cooled filament 11 using an oil roller (OR) or an oil sprayer. The oiling process can also be performed using a metered oiling method (MO).

[0113] Optionally, when the filaments 11 are gathered to form the multifilament yarn 10, the oiling step can be performed simultaneously, and additional oiling steps can be performed during the stretching step and / or immediately before the winding step.

[0114] Meanwhile, one embodiment of the method for manufacturing polyethylene yarn may include stretching and heat-setting the multifilament yarn with a total elongation of 8 to 20 times.

[0115] At this point, multiple guide rollers can be used to perform the stretching step, and multiple guide rollers can be used to perform the heat setting of the multifilament yarn.

[0116] Specifically, the multifilament yarn 10 can be stretched at a total stretch ratio of 8 to 20 times, more preferably 10 to 15 times.

[0117] To achieve a strength of 11 g / d or higher in the final polyethylene yarn, the multifilament yarn 10 must be stretched at a total stretch ratio of 8 times or more. However, if a total stretch ratio of more than 20 times is applied during the stretching step, the risk of yarn breakage in the filaments (multiple strands) 11 increases.

[0118] Meanwhile, the stretching step can be performed in a multi-stage stretching manner, and the relaxation rate at the final stretch during the multi-stage stretching process can be 3% to 8%.

[0119] The inventors have confirmed that the initial modulus and elongation of polyethylene yarn during the spinning process of polyethylene used as raw material are mainly affected by the relaxation rate during the final stretching process in the multi-stage stretching process.

[0120] The relaxation rate at final stretch refers to the relaxation rate when the final stretch is performed after stretching but before winding.

[0121] To achieve an initial modulus of less than 250 g / d and an elongation of more than 6% in polyethylene yarn, the relaxation rate at the final stretch during the multi-stage stretching process in manufacturing polyethylene yarn should be 3% to 8%, or 4% to 6%. If the relaxation rate at the final stretch is too high, it may be difficult to manufacture polyethylene yarn with a strength of more than 11 g / d.

[0122] Specifically, when the relaxation rate at the final stretch is below 3%, the resulting yarn has a modulus of over 250 g / d, which can cause problems with flexibility. When the relaxation rate is above 8%, the yarn on the guide roller may move violently, potentially leading to production difficulties.

[0123] Therefore, in order to manufacture polyethylene yarn with reduced initial modulus, high elongation and improved wearability, it is preferable to apply the relaxation rate of the final stretch in the multi-stage stretching process to the range described above.

[0124] The polyethylene yarn of the present invention can be manufactured by once winding a multifilament yarn 10 as an unstretched yarn, and then unwinding and stretching the unstretched yarn. Figure 1 As shown, polyethylene yarn can also be manufactured by directly stretching it using a stretching section 500 that includes multiple guide rollers GR1...GRn, without winding the multifilament yarn 10, which is an unstretched yarn.

[0125] Regardless of which of the two steps described above is applied, precise control of the stretching process is required to minimize the risk of yarn breakage in the filaments (multiple strands) 11 when stretching the multifilament yarn 10 at a large total stretch ratio of 8 to 20 times. Furthermore, as described above, it is preferable to keep the relaxation rate of the final stretch portion of the guide roller below 3% to 8% during stretching.

[0126] Meanwhile, one embodiment of the method for manufacturing polyethylene yarn may include winding stretched multifilament yarn.

[0127] like Figure 1 As shown, before the stretched multifilament 10 is wound onto the winding machine 700, a further entanglement step can be performed by the entanglement device 600 to improve the cohesiveness and braiding properties of the polyethylene yarn.

[0128] The polyethylene yarn of the present invention, manufactured as described above, can be used to produce protective items requiring excellent cut resistance (e.g., protective gloves, underwear, bags, etc.).

[0129] The protective article according to an embodiment of the present invention will be described in detail below.

[0130] The protective article of the present invention is a protective article woven from covered yam, such as protective gloves.

[0131] The covering yarns include the polyethylene yarns of the present invention, polyurethane yarns (e.g., spandex) spirally surrounding the polyethylene yarns, and polyamide yarns (e.g., nylon 6 or nylon 66 yarns) spirally surrounding the polyethylene yarns. Depending on the characteristics of the desired article, polyester yarns (e.g., PET yarns) may be substituted for polyamide yarns.

[0132] The weight of polyethylene yarn can be 45% to 85% of the total weight of the covering yarn, the weight of polyurethane yarn can be 5% to 30% of the total weight of the covering yarn, and the weight of polyamide yarn or polyester yarn can be 5% to 30% of the total weight of the covering yarn.

[0133] As described above, the polyethylene yarn of the present invention may have a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol, an initial modulus of 100 g / d to 250 g / d, and an elongation of 6% to 10%.

[0134] Preferably, the polyethylene yarn may have an initial modulus of 120 g / d to 200 g / d.

[0135] In addition, the dry heat shrinkage rate of polyethylene yarn at 100°C can be greater than 2.5% and less than 6%.

[0136] In addition, the storage elasticity retention rate of polyethylene yarn can be 65% to 75% at 50°C, 30% to 45% at 80°C, and 10% to 25% at 105°C.

[0137] The protective article of the present invention has a cut resistance index of 5 or higher and a low stiffness of less than 5 gf, thus exhibiting excellent cut resistance and excellent wearability.

[0138] Specifically, according to EN388:2016, the cut resistance index of protective articles can be: 5.0 or higher, or 5.5 or higher, or 5.7 or higher; and below 8.5, or 8.0, or 7.5, or 7.0, or 6.8. For example, according to EN388:2016, the cut resistance index of protective articles can be: 5.0 to 8.5, or 5.0 to 8.0, or 5.0 to 7.5, or 5.0 to 7.0, or 5.0 to 6.8, or 5.5 to 8.5, or 5.5 to 8.0, or 5.5 to 7.5, or 5.5 to 7.0, or 5.5 to 6.8, or 5.7 to 8.5, or 5.7 to 8.0, or 5.7 to 7.5, or 5.7 to 7.0, or 5.7 to 6.8.

[0139] Meanwhile, the stiffness of protective equipment can be: below 5.0gf or below 4.5gf; and above 2.0gf, or above 3.0gf, or above 3.5gf, or above 3.8gf. For example, the stiffness of protective equipment can be: 2.0gf to 5.0gf, or 2.0gf to 4.5gf, or 3.0gf to 5.0gf, or 3.0gf to 4.5gf, or 3.5gf to 5.0gf, or 3.5gf to 4.5gf, or 3.8gf to 5gf, or 3.8gf to 4.5gf.

[0140] The present invention will be described in detail below with reference to specific embodiments and comparative examples. However, these embodiments are only for the purpose of helping to understand the present invention, and the scope of the present invention should not be limited thereto.

[0141] <Manufacturing of Polyethylene Yarn>

[0142] Preparation Example 1

[0143] use Figure 1 The equipment shown manufactures polyethylene multifilament entangled yarn containing 240 filaments with a total fineness of 400 denier.

[0144] Specifically, polyethylene chips with a weight-average molecular weight (Mw) of 150,000 g / mol and a melt index (MI) of 1 g / 10 min (190 °C) are introduced into an extruder 100 and melted. The polyethylene melt is then extruded through a spinneret 200 with 240 nozzle orifices.

[0145] The filaments 11 formed when discharged from the nozzle orifice of the spinneret 200 are cooled in the cooling section 300 and then converged into multifilament yarns 10 by the converging device 400.

[0146] Next, in the stretching section 500, the multifilament yarn is stretched and heat-set at a total stretch ratio of 12 times by a guide roller set to 70°C to 130°C.

[0147] The stretching process is performed in a multi-stage stretching manner, and the relaxation rate at the final stretch is 8% during the multi-stage stretching process.

[0148] Next, the stretched multifilament is entangled in the entanglement device 600 at a rate of 6.0 kgf / cm. 2 The air pressure is entangled and then wound in a winding machine 700. The winding tension is 0.6 g / d.

[0149] Preparation Example 2

[0150] The polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips with a weight-average molecular weight (Mw) of 150,000 g / mol and a melt index (MI) of 1 g / 10 min (at 190°C) were used and the relaxation rate at the final stretch during the multi-stage stretching process was 5%.

[0151] Preparation Example 3

[0152] The polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips with a weight-average molecular weight (Mw) of 180,000 g / mol and a melt index (MI) of 0.8 g / 10 min (at 190°C) were used and the relaxation rate at the final stretch during the multi-stage stretching process was 3%.

[0153] Preparation of Comparative Example 1

[0154] The polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips with a weight-average molecular weight (Mw) of 200,000 g / mol and a melt index (MI) of 0.6 g / 10 min (at 190°C) were used and the relaxation rate at the final stretch during multi-stage stretching was 2%.

[0155] Preparation of Comparative Example 2

[0156] The polyethylene yarn was obtained in the same manner as in Example 1, except that polyethylene chips with a weight-average molecular weight (Mw) of 200,000 g / mol and a melt index (MI) of 0.6 g / 10 min (at 190°C) were used and the relaxation rate at the final stretch during the multi-stage stretching process was 10%.

[0157] Test Example 1

[0158] The strength, initial modulus, elongation, dry heat shrinkage, storage elasticity retention and weight-average molecular weight (Mw) of the polyethylene yarns manufactured in each of Preparation Examples 1 to 3 and Preparation Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Table 1 below.

[0159] (1) Strength (g / d), initial modulus (g / d), and elongation (%)

[0160] According to the test method ASTM D885, the strength, elongation, and initial modulus of polyethylene yarn were determined by obtaining strain-stress curves using a universal testing machine (Instron Engineering Corp., Canton, Mass). Specifically, the sample length was set to 250 mm, the tensile speed to 300 mm / min, and the initial load to 0.05 g / d. The initial modulus (g / d) was determined by the tangent line that gave the maximum gradient near the origin. Five measurements were taken for each polyethylene yarn, and the average value was calculated.

[0161] (2) Dry heat shrinkage rate

[0162] The polyethylene yarn was cut to obtain a sample with a length of 70 cm, and then marked at points 10 cm from both ends of the sample (i.e., the distance between the marked points = 50 cm).

[0163] Then, with the sample suspended on a fixture without applying any load, it was heated at 100°C for 30 minutes in a hot air circulating furnace. Afterward, the sample was removed from the furnace, slowly cooled to room temperature, and the distance between the marked points was measured. The dry heat shrinkage rate of the polyethylene yarn at 100°C was then calculated using Equation 1.

[0164] Equation 1: Dry heat shrinkage rate (%) = [(I0-I1) / I0] × 100

[0165] (Where, I0 is the distance between the marked points before heating (i.e., 50cm), and I1 is the distance between the marked points after heating.)

[0166] The average dry heat shrinkage rate obtained from the two tests was obtained.

[0167] (3) Storage elasticity retention rate

[0168] After preparing polyethylene yarn samples with a length of 10 mm, the storage elastic modulus at 30°C, 50°C, 80°C, and 105°C was measured using an intrinsic viscoelasticity measuring device (manufactured by TA Instruments, DMA Q800). Specifically, the two ends of the sample were clamped between thick paper using adhesive and double-sided tape to prevent slippage or scattering of the filaments between the sample and the device during measurement. The measurement start temperature was set to -10°C, the measurement end temperature to 140°C, and the heating rate to 1.0°C / min. The deformation was set to 0.04%, the initial load at the start of the measurement to 0.05 cN / dtex, and the measurement frequency to 11 Hz. The data were analyzed using "TA Universal Analysis" (manufactured by TA Instruments). The storage elasticity retention rates at 50°C, 80°C, and 105°C were calculated using Equation 2.

[0169] Equation 2: Storage elasticity retention rate (%) at T℃ = (Storage elasticity modulus at T℃ / Storage elasticity modulus at 30℃) × 100 (where T℃ = 50℃ / 80℃ / 105℃)

[0170] (4) Weight-average molecular weight (Mw) (g / mol) and polydispersity index (PDI)

[0171] Polyethylene yarn was completely dissolved in the following solvent, and then the following gel permeation chromatography (GPC) method was used to determine the weight-average molecular weight (Mw), number-average molecular weight (Mn), and polydispersity index (Mw / Mn: PDI) of the polyethylene yarn.

[0172] -Analytical instrument: PL-GPC 220 system

[0173] -Column: 2×PLGEL MIXED-B (7.5×300mm)

[0174] - Column temperature: 160℃

[0175] Solvent: Trichlorobenzene (TCB) + 0.04 wt% Butylated hydroxytoluene (BHT) (dried with 0.1% CaCl2)

[0176] - Dissolution conditions: After dissolving at 160°C for 1 to 4 hours, measure the solution passing through a glass filter (0.7 μm).

[0177] - Syringe and detector temperature: 160℃

[0178] -Detector: RI detector

[0179] - Flow rate: 1.0 ml / min

[0180] -Injection volume: 200μl

[0181] -Standard sample: Polystyrene

[0182] Table 1

[0183]

[0184] Production of Protective Gloves

[0185] Example 1

[0186] The coated yarn of Example 1 was produced by spirally wrapping the polyethylene yarn with 140 denier polyurethane yarn (spandex) and 140 denier nylon yarn. The polyethylene yarn accounted for 60% of the total weight of the coated yarn, and the polyurethane yarn and nylon yarn each accounted for 20% of the total weight of the coated yarn. The coated yarn was then woven to produce protective gloves.

[0187] Example 2

[0188] Protective gloves were obtained in the same manner as in Example 1, except that the polyethylene yarn used in Preparation Example 2 was used.

[0189] Example 3

[0190] Protective gloves were obtained in the same manner as in Example 1, except that the polyethylene yarn used in Preparation Example 3 was used.

[0191] Comparative Example 1

[0192] Protective gloves were obtained in the same manner as in Example 1, except that the polyethylene yarn used in the preparation of Comparative Example 1 was used.

[0193] Comparative Example 2

[0194] Protective gloves were obtained in the same manner as in Example 1, except that the polyethylene yarn used in the preparation of Comparative Example 2 was used.

[0195] Test Example 2

[0196] The cut resistance index and strength of the protective gloves prepared by each of Examples 1 to 3 and Comparative Examples 1 to 2 were measured by the following methods, and the results are shown in Table 2 below.

[0197] (1) Cut resistance index (CI)

[0198] According to EN388:2016 standard, the cut resistance index of protective gloves is measured.

[0199] (2) Stiffness (gf)

[0200] like Figure 2 and Figure 3 As shown, after collecting the specimen (width: 60 mm, length: 60 mm) 21 from the palm portion of the protective glove 20, the stiffness of the specimen was measured according to Section 38 of ASTM D885 / D885M-10a (2014). The measuring apparatus is as follows.

[0201] (i) CRE type tensile testing machine (model: INSTRON 3343)

[0202] (ii) Loading unit, 2KN [200kgf]

[0203] (iii) Specimen holder: The specimen holder specified in Section 38.4.3

[0204] (iv) Sample presser: The sample presser specified in Section 38.4.4.

[0205] Specifically, with the outer surface (f1) of the glove facing upwards and the inner surface (f2) facing downwards, the side (21a) adjacent to the fingers of the glove and its opposite side (21b, i.e., the side adjacent to the wrist of the glove) are placed in the center of the sample holder 31, so that the sample 21 is directly supported by the sample holder 31. The sample 21 remains flat and does not bend. At this time, the distance between the sample support part of the sample holder 31 and the pressing part of the sample presser 32 is 5 mm. Then, with the sample presser 32 stationary, the sample holder 31 is raised to 15 mm while the maximum strength is measured.

[0206] Table 2

[0207]

[0208] According to Table 2 above, it was confirmed that the protective gloves of Examples 1 to 3 produced using the polyethylene yarn according to Preparation Examples 1 to 3 have excellent cut resistance and low stiffness, thus having improved wearability compared to Comparative Examples 1 and 2.

Claims

1. A polyethylene yarn having a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol, an initial modulus of 150 g / d to 200 g / d, and an elongation of 6% to 10%. wherein The polyethylene yarn comprises 40 to 500 filaments, each of which has a fineness of 1 to 3 denier, and the polyethylene yarn has a total fineness of 100 to 1,000 denier. The ratio of the storage elastic modulus at 50°C to that at 30°C is 68% to 75%. The ratio of the storage elastic modulus at 80°C to that at 30°C is 37% to 45%, and The ratio of the storage elastic modulus at 105°C to that at 30°C is 20% to 25%.

2. The polyethylene yarn according to claim 1, wherein, The dry heat shrinkage rate at 100℃ is greater than 2.5% and less than 6.0%.

3. A method for manufacturing polyethylene yarn according to claim 1, comprising the following steps: Polyethylene chips with a weight-average molecular weight of 80,000 g / mol to 180,000 g / mol and a melt index (MI) of 0.3 g / 10 min to 3 g / 10 min at 190 °C are melted to obtain polyethylene melt. The polyethylene melt is extruded through a spinneret with multiple nozzle holes; The multiple filaments formed when the polyethylene melt is discharged from the nozzle orifice are cooled; The cooled filaments are then gathered together to form a multifilament yarn; The multifilament yarn is stretched and heat-set with a total stretch ratio of 8 to 20 times. as well as The stretched and heat-set multifilament yarn is then wound. The stretching step is performed in a multi-stage stretching manner, and the relaxation rate at the final stretch during the multi-stage stretching process is 3% to 8%.

4. The method for manufacturing polyethylene yarn according to claim 3, wherein, The stretching step is performed using multiple guide rollers.

5. The method for manufacturing polyethylene yarn according to claim 3, wherein, The heat setting of the multifilament yarn is performed by multiple guide rollers.

6. A protective item woven from covered yarn, The covering yarn includes: The polyethylene yarn according to claim 1; A polyurethane yarn, wherein the polyurethane yarn spirally surrounds the polyethylene yarn; as well as Polyamide yarn or polyester yarn, wherein the polyamide yarn or polyester yarn spirally surrounds the polyethylene yarn. The protective item has a cut resistance index of 5.7 to 6.8 and a stiffness of 3.8 gf to 5.0 gf.

7. The protective article according to claim 6, wherein, The polyethylene yarn has a dry heat shrinkage rate of greater than 2.5% and less than 6.0% at 100°C.

8. The protective article according to claim 6, wherein, The weight of the polyethylene yarn is 45% to 85% of the total weight of the covering yarn. The weight of the polyurethane yarn is 5% to 30% of the total weight of the covered yarn, and The weight of the polyamide yarn or the polyester yarn is 5% to 30% of the total weight of the covered yarn.

Images