阅读说明：本技术 耐切割聚乙烯纱线、其制造方法及使用其制造的防护物品 (Cut-resistant polyethylene yarn, method for producing same, and protective article produced using same ) 是由 李英洙 李相牧 金成龙 李信镐 南民祐 于 2020-03-20 设计创作，主要内容包括：本发明涉及一种能够制造具有高耐切割性并且能够提供优异穿着感的防护物品的聚乙烯纱线、其制造方法及使用其制造的防护物品。本发明的聚乙烯纱线尽管通过熔融纺丝制造但仍具有高强度,从而能够制造具有高耐切割指数的防护物品。另外,本发明的聚乙烯纱线具有低初始模量和高伸长率,因此能够生产具有优异穿着感的防护物品。(The present invention relates to a polyethylene yarn capable of producing a protective article having high cut resistance and providing excellent wearing feeling, a method for producing the same, and a protective article produced using the same. The polyethylene yarn of the invention has high strength despite being produced by melt spinning, enabling the manufacture of protective articles with a high cut resistance index. In addition, the polyethylene yarn of the present invention has a low initial modulus and a high elongation, and therefore can produce protective articles having excellent wearing feeling.)

1. A polyethylene yarn having a weight average molecular weight of 80,000 to 180,000g/mol, an initial modulus of 100 to 250g/d, and an elongation of 6 to 10%.

2. The polyethylene yarn according to claim 1, wherein the initial modulus is from 120 to 200 g/d.

3. The polyethylene yarn according to claim 1, wherein the dry heat shrinkage at 100 ℃ is more than 2.5% and 6.0% or less.

4. The polyethylene yarn according to claim 1,

a ratio of storage elastic modulus at 50 ℃ to storage elastic modulus at 30 ℃ is 65% to 75%,

a ratio of storage elastic modulus at 80 ℃ to storage elastic modulus at 30 ℃ is 30% to 45%, and

the ratio of the storage elastic modulus at 105 ℃ to the storage elastic modulus at 30 ℃ is 10% to 25%.

5. The polyethylene yarn according to claim 1,

the polyethylene yarn includes 40 to 500 filaments, each of the filaments has a fineness of 1 to 3 deniers, and the polyethylene yarn has a total fineness of 100 to 1,000 deniers.

6. A method of making a polyethylene yarn comprising the steps of:

melting polyethylene chips having a melt index, i.e., MI, of 0.3g/10min to 3g/10min at 190 ℃ to obtain a polyethylene melt;

extruding the polyethylene melt through a spinneret having a plurality of nozzle orifices;

cooling a plurality of filaments formed as the polyethylene melt is discharged from the nozzle bore;

converging the cooled filaments to form a multifilament yarn;

drawing and heat-setting the multifilament yarn at a total draw ratio of 8 to 20 times; and

winding the drawn and heat-set multifilament yarn,

wherein the stretching step is performed in a multi-stage stretching manner, and a relaxation rate at the time of final stretching in the multi-stage stretching process is 3% to 8%.

7. The process for producing a polyethylene yarn according to claim 6,

the weight average molecular weight of the polyethylene chip is 80,000g/mol to 180,000 g/mol.

8. The process for producing a polyethylene yarn according to claim 6,

the drawing step is performed using a plurality of godets.

9. The process for producing a polyethylene yarn according to claim 6,

the heat-setting of the multifilament yarns is performed by a plurality of godets.

10. A protective article knitted by using a covering yarn,

the wrap yarn comprises:

the polyethylene yarn of claim 1;

a polyurethane yarn helically surrounding the polyethylene yarn; and

a polyamide yarn or a polyester yarn spirally surrounding the polyethylene yarn,

wherein the protective article has a cut resistance index of 5.0 or more and a stiffness of 5.0gf or less.

11. The protective article according to claim 10,

the protective article has a cut resistance index of 5.5 to 8.5 and a stiffness of 2.0gf to 5.0 gf.

12. The protective article according to claim 10,

the polyethylene yarn has an initial modulus of 120g/d to 200 g/d.

13. The protective article according to claim 10,

the polyethylene yarn has a dry heat shrinkage of more than 2.5% and 6.0% or less at 100 ℃.

14. The protective article according to claim 10,

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 covering yarn, and

the polyamide yarn or the polyester yarn is 5% to 30% by weight of the total weight of the covered yarn.

Technical Field

The present invention relates to a cut-resistant polyethylene yarn, a method for manufacturing the same, and a protective article manufactured using the same, and more particularly, to a polyethylene yarn which can manufacture a protective article capable of providing excellent wearability while having high cut resistance, a method for manufacturing the same, and a protective article manufactured using the same.

Background

Personnel working in the security field, such as police and military personnel, and in other various industrial fields, operating sharp cutting tools, are always exposed to the risk of injury. Protective articles such as gloves or clothing should be provided to minimize the risk of injury.

In order to properly protect the body from weapons or sharp cutting tools (e.g., knives), the protective articles need to be cut resistant.

In order to provide high cut resistance to protective articles, high strength polyethylene yarns are used in the manufacture of these protective articles. For example, high strength polyethylene yarn alone is used to make a fabric, or high strength polyethylene yarn and other type of yarn(s) can be used together to form a plied yarn, which can then be used to make a fabric.

Ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE"), which is a type of high strength polyethylene yarn, is generally a yarn formed of linear polyethylene having a weight average molecular weight of 600,000g/mol or more, and can be manufactured only by a gel spinning method due to the high melt viscosity (meltviscoity) of UHMWPE. For example, ethylene may be polymerized in an organic solvent in the presence of a catalyst to produce a UHMWPE solution, the solution is spun and cooled to form a gel in the form of fibers, and the gel in the form of fibers may be drawn to obtain high strength and high modulus polyethylene yarns. However, since such a gel spinning method requires the use of an organic solvent, it not only poses environmental problems, but also requires a huge cost for recovering the organic solvent.

Generally, since high-density polyethylene, which is linear polyethylene having a weight average molecular weight of 20,000 to 600,000g/mol, has a relatively low melt viscosity compared to UHMWPE, it is melt-spinnable, and thus, environmental problems and high cost problems, which cannot be avoided in the gel spinning process, can be overcome. However, the strength of high density polyethylene yarns is inevitably lower than that of UHMWPE yarns due to their relatively low molecular weight compared to UHMWPE.

Therefore, attempts have been made to improve the strength of high-density polyethylene yarns, and therefore, even when polyethylene yarns produced by melt spinning are used, protective articles having satisfactory cut resistance can be produced.

However, although high density polyethylene yarns developed with only an emphasis on the increase in strength can provide satisfactory cut resistance to protective articles, they cause a serious problem of deterioration in wearability (wearability). In other words, protective gloves or garments made of polyethylene yarn become too stiff, which impedes the wearer's movements (e.g., the movement of fingers in the case of gloves) and reduces work efficiency. This poor wearability leads to escape wearing protective articles and increases the risk of injury.

Disclosure of Invention

Technical problem

The present invention is directed to a cut resistant polyethylene yarn that prevents problems due to limitations and disadvantages of the related art, a method of manufacturing the same, and a protective article manufactured using the same.

One aspect of the present invention is to provide a polyethylene yarn that can manufacture a protective article capable of providing excellent wearability while having high cut resistance.

It is yet another aspect of the present invention to provide a method of manufacturing a polyethylene yarn that can manufacture a protective article capable of providing excellent wearability while having high cut resistance.

It is yet another aspect of the present invention to provide a protective article capable of providing excellent wearability while having high cut resistance.

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

Technical scheme

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

The polyethylene yarn may have an initial modulus of 120g/d to 200 g/d.

The polyethylene yarn may have a dry heat shrinkage at 100 ℃ of more than 2.5% and 6.0% or less.

The ratio of the storage elastic modulus at 50 ℃ to the storage elastic modulus at 30 ℃ of the polyethylene yarn may be 65% to 75%, the ratio of the storage elastic modulus at 80 ℃ to the storage elastic modulus at 30 ℃ may be 30% to 45%, and the ratio of the storage elastic modulus at 105 ℃ to the storage elastic modulus at 30 ℃ may be 10% to 25%.

The polyethylene yarn may include 40 to 500 filaments, each of the filaments having a fineness of 1 to 3 deniers, and the polyethylene yarn may have a total fineness of 100 to 1,000 deniers.

According to another aspect of the present invention, there is provided a method of manufacturing a polyethylene yarn, comprising the steps of:

melting polyethylene chips having a Melt Index (MI) (at 190 ℃) of 0.3 to 3g/10min to obtain a polyethylene melt;

extruding a polyethylene melt through a spinneret having a plurality of nozzle orifices;

cooling a plurality of filaments formed as the polyethylene melt is discharged from the nozzle orifice;

converging the cooled filaments to form a multifilament yarn;

drawing and heat-setting (heat-setting) the multifilament yarn at an overall draw ratio of 8 to 20 times; and

winding the drawn and heat-set multifilament yarn,

wherein the stretching step is performed in a multi-stage stretching manner, and a relaxation rate at the time of final stretching during the multi-stage stretching is 3% to 8%.

The polyethylene chips may have a weight average molecular weight of 80,000g/mol to 180,000 g/mol.

The drawing step may be performed using a plurality of godet rolls.

Heat-setting of the multifilament yarn may be performed by a plurality of godets.

According to another aspect of the present invention there is provided a protective article knitted with a covering yarn (coveredyarn), the covering yarn comprising:

the above polyethylene yarn;

a polyurethane yarn helically surrounding a polyethylene yarn; and

a polyamide or polyester yarn helically surrounding a polyethylene yarn,

wherein the protective article has a cut resistance index (SAI) of 5.0 or more and a stiffness (stiffness) of 5.0gf or less.

The protective article may have a cut resistance index of 5.5 to 8.5 and a stiffness of 2.0gf to 5.0 gf.

The polyethylene yarn may have a dry heat shrinkage at 100 ℃ of greater than 2.5% and less than 6%.

The weight of the polyethylene yarn may be 45% to 85% of the total weight of the cover yarn, the weight of the polyurethane yarn may be 5% to 30% of the total weight of the cover yarn, and the weight of the polyamide yarn or the polyester yarn may be 5% to 30% of the total weight of the cover yarn.

The general description of the invention above is intended only to illustrate or explain the invention and does not limit the scope of the invention.

Advantageous effects

The polyethylene yarn of the invention, although produced by melt spinning, has a high strength of 11g/d or more, enabling the manufacture of protective articles having a high cut resistance index of 5 or more, more preferably 5.5 to 8.5.

Further, the polyethylene yarn of the present invention has a low initial modulus of 250g/d or less and a high elongation of 6% or more, and thus can produce protective articles having a low stiffness of 5gf or less, more preferably 2 to 5gf (i.e., excellent wearability).

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention.

Fig. 1 schematically shows an apparatus for manufacturing polyethylene yarns according to one embodiment of the present invention.

Fig. 2 and 3 illustrate a method of measuring the strength of a protective glove.

< description of reference >

100: the extruder 200: spinning nozzle

300: cooling section 400: converging part

500: stretching section 600: entanglement device

700: winding machine

20: protective gloves

21: sample of protective gloves

21 a: side adjacent to fingers of glove

21 b: side adjacent to wrist of glove

f 1: outside of the glove

f 2: inner side of glove

31: sample holder

32: sample pressing device

Detailed Description

Hereinafter, various embodiments of the polyethylene yarn of the present invention will be described in detail.

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

In previous studies, where only the cut resistance of protective articles was overemphasized, it was proposed to increase the initial modulus of polyethylene yarns, for example, to above 300g/d, and to reduce the elongation, for example, to below 6%.

However, according to the present invention, the cut resistance of the protective article is mainly determined by the strength of the polyethylene yarn, the slipperiness of the polyethylene yarn (i.e. the characteristic of the polyethylene yarn sliding along the surface without being caught by the yarn when a knife or sharp tool passes over it), and the winding characteristics of the fibers constituting the yarn (i.e. the characteristic of the fibers twisting or curling around the longitudinal axis of the yarn when a knife or sharp tool passes over it), and it is judged that the initial modulus and elongation of the polyethylene yarn once reaching a certain level no longer have a substantial influence on the cut resistance of the protective product.

In contrast, if the initial modulus of the polyethylene yarn is too high and/or the elongation of the polyethylene yarn is too low, the fabric manufactured using such polyethylene yarn has high stiffness, the wearability of the protective product is significantly reduced due to poor covering and weaving properties, and the yield may be reduced.

Accordingly, the present inventors have experimentally confirmed that when a polyethylene yarn has an initial modulus of 100 to 250g/d, an elongation of 6 to 10%, and a weight average molecular weight of 80,000 to 180,000g/mol, it has excellent strength and cut resistance index while having low stiffness, and thus can improve wearability, thereby completing the present invention.

The polyethylene yarn of one embodiment has a weight average molecular weight of 80,000 to 180,000g/mol, or 120,000 to 160,000g/mol, or 140,000 to 160,000g/mol, which can achieve high strength.

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

Specifically, the initial modulus of the polyethylene yarn may be 100g/d or more, or 120g/d or more, or 150g/d or more; and is 250g/d or less, 230g/d or less, or 200g/d or less. For example, the initial modulus of the polyethylene yarn may be from 100g/d to 250g/d, or from 100g/d to 230g/d, or from 100g/d to 200g/d, or from 120g/d to 250g/d, or from 120g/d to 230g/d, or from 120g/d to 200g/d, or from 150g/d to 250g/d, or from 150g/d to 230g/d, or from 150g/d to 200 g/d.

When the initial modulus of the polyethylene yarn is greater than 250g/d or the elongation is less than 6%, the fabric manufactured using the polyethylene yarn has high stiffness of more than 5gf, so the fabric is excessively stiff and the wearer of the protective product may feel uncomfortable.

In case the initial modulus of the polyethylene yarn is less than 100g/d or the elongation is more than 10%, as the user continuously uses the protective product manufactured using the polyethylene yarn, the cut resistance is reduced, the pilling (piles) in the fabric may occur, and the fabric may be even damaged.

Meanwhile, the dry heat shrinkage rate of the polyethylene yarn can be more than 2.5% and less than 6% at 100 ℃.

Specifically, the polyethylene yarn may exhibit a dry heat shrinkage at 100 ℃ of greater than 2.5%, or 2.8% or more, or 3.0% or more; and 6.0% or less, or 5.0% or less, or 4.0% or less, or 3.5% or less. For example, the dry heat shrinkage of the polyethylene yarn at 100 ℃ may be expressed as greater than 2.5% and 6.0% or less, or greater than 2.5% and 5.0% or less, or greater than 2.5% and 4.0% or less, or greater than 2.5% and 3.5% or less, 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%.

When the dry heat shrinkage rate is 2.5% or less, the initial modulus of the yarn exceeds 250g/d, and thus the wearability of the protective article may be deteriorated. On the other hand, when the dry heat shrinkage rate exceeds 6%, there is a problem that a finished product (e.g., protective glove) manufactured with such yarn has a high risk of deformation due to shrinkage. According to an embodiment of the present invention, the dry heat shrinkage rate of the polyethylene yarn can be adjusted to be more than 2.5% and less than 6% by selecting a polyethylene raw material having an appropriate molecular weight and appropriately adjusting the stretching conditions.

The ratio of the storage elastic modulus at 50 ℃ to the storage elastic modulus at 30 ℃ (hereinafter referred to as "storage elastic retention at 50 ℃) of the polyethylene yarn of the present invention may be 65% to 75%, or 68% to 75%.

The ratio of the storage elastic modulus at 80 ℃ to the storage elastic modulus at 30 ℃ (hereinafter referred to as "storage elastic retention at 80 ℃) of the polyethylene yarn may be 30% to 45%, or 35% to 45%, or 37% to 45%.

Also, the ratio of the storage elastic modulus at 105 ℃ to the storage elastic modulus at 30 ℃ (hereinafter referred to as "storage elastic retention at 105 ℃) of the polyethylene yarn may be 10% to 25%, or 15% to 25%, or 20% to 25%.

By selecting a polyethylene raw material having an appropriate molecular weight, the storage elasticity retention rates of the polyethylene yarns can be adjusted within the above ranges, respectively.

When the storage elasticity retention at 50 ℃ is less than 65%, or the storage elasticity retention at 80 ℃ is less than 30%, or the storage elasticity retention at 105 ℃ is less than 10%, the strength of the yarn is reduced to less than 11g/d, making it difficult to manufacture a protective product having satisfactory cut resistance.

On the other hand, if the storage elasticity retention at 50 ℃ exceeds 75%, or the storage elasticity retention at 80 ℃ exceeds 45%, or the storage elasticity retention at 105 ℃ exceeds 25%, the initial modulus of the yarn exceeds 250g/d, and therefore, the wearability of the protective article may decrease and the shrinkage rate may decrease.

Meanwhile, the polyethylene 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 denier to 3 denier, and the polyethylene yarn may have a total fineness of 100 denier to 1,000 denier.

Meanwhile, the polyethylene yarn pair of the present invention may have a polydispersity index (PDI) of more than 5 and 9 or less for a protective article manufactured using the yarn. The polydispersity index (PDI) is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn), also known as the molecular weight distribution index (MWD).

Furthermore, the strength of the polyethylene yarn of the invention may be 11g/d or more, preferably 11g/d to 18g/d, so that the protective articles manufactured using the yarn may have a cut resistance index of 5 or more.

Meanwhile, according to another embodiment of the present invention, there may be provided a method of manufacturing a polyethylene yarn, the method including the steps of:

melting polyethylene chips having a Melt Index (MI) (at 190 ℃) of 0.3g/10min to 3g/10min to obtain a polyethylene melt;

extruding a polyethylene melt through a spinneret having a plurality of nozzle orifices;

cooling a plurality of filaments formed as the polyethylene melt is discharged from the nozzle bore;

converging the cooled filaments to form a multifilament yarn;

drawing and heat-setting the multifilament yarn at a total draw ratio of 8 to 20 times; and

the drawn and heat-set multifilament yarn is wound,

wherein the stretching step is performed in a multi-stage stretching manner, and a relaxation rate at the time of final stretching during the multi-stage stretching is 3% to 8%.

Hereinafter, a method of manufacturing a polyethylene yarn according to one embodiment of the present invention will be described in detail with reference to fig. 1.

A method of making a polyethylene yarn may include melting polyethylene chips having a Melt Index (MI) (at 190 ℃) of 0.3g/10min to 3g/10min to obtain a polyethylene melt.

For example, a polyethylene melt is obtained by first introducing polyethylene chips into the extruder 100 and melting them.

The polyethylene used as a raw material in the process of the present invention (hereinafter referred to as "polyethylene chip") has a Melt Index (MI) of 0.3g/10min to 3g/10 min. In the present specification, the melt index of a polyethylene chip is a value measured at 190 ℃.

When the Melt Index (MI) of the polyethylene chip is less than 0.3g/10min, it is difficult to ensure smooth fluidity in the extruder 100 due to high viscosity and low fluidity of the polyethylene melt, the spinning device is overloaded and process control cannot be properly performed, and thus it is difficult to ensure uniformity of yarn characteristics. On the other hand, when the Melt Index (MI) of the polyethylene chip exceeds 3g/10min, the fluidity of the polyethylene melt in the extruder 100 is relatively good, but it is difficult to obtain a yarn having high strength characteristics of 11g/d or more due to the low molecular weight of polyethylene.

The polyethylene chips may have a weight average molecular weight (Mw) of 80,000g/mol or more, or 100,000g/mol or more, or 120,000g/mol or more. When the weight average molecular weight (Mw) is less than 80,000g/mol, it is difficult for the finally obtained yarn to have a strength of 11g/d or more.

Meanwhile, if the weight average molecular weight (Mw), which generally has an inverse relationship with the Melt Index (MI), is excessively high, exceeding 180,000g/mol, the spinning apparatus is overloaded due to high melt viscosity and process control cannot be properly performed, so it is difficult to ensure excellent characteristics of the yarn. Therefore, the weight average molecular weight (Mw) of the polyethylene chip is preferably 180,000g/mol or less, 170,000g/mol or less, or 160,000g/mol or less.

However, considering that the molecular weight may be slightly decreased due to thermal decomposition of polyethylene during spinning, the upper limit of the weight average molecular weight (Mw) of the polyethylene chip may be slightly higher than the upper limit of the target molecular weight (i.e., the weight average molecular weight of the polyethylene yarn in the present invention and is 80,000 to 180,000 g/mol).

The polyethylene chip of the invention may have an initial modulus of 100g/d to 250g/d and an elongation of 6% to 10%.

The polyethylene chip of the present invention may have a polydispersity index (PDI) of more than 5 and 9 or less.

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

The polyethylene melt is fed to a spinneret 200 having a plurality of nozzle holes through a screw in an extruder 100 and then extruded through the nozzle holes. The number of nozzle holes in the spinneret 200 may be determined according to DPF (denier per filament) and total fineness of the yarn to be manufactured. According to an embodiment of the present invention, in order to manufacture a yarn having DPF of 1 to 3 and a total fineness of 100 to 1,000, the spinneret 200 may have 40 to 500 nozzle holes.

The melting process in the extruder 100 and the extrusion process through the spinneret 200 are performed at 150 to 315 ℃, preferably at 250 to 315 ℃, more preferably at 260 to 290 ℃. That is, the extruder 100 and the spinneret 200 are maintained at 150 ℃ to 315 ℃, preferably at 250 ℃ to 315 ℃, and more preferably at 260 ℃ to 290 ℃. According to one embodiment of the present invention, polyethylene chips are introduced into the extruder 100, and a space moving until being discharged through nozzle holes of the spinneret 200 is divided into a plurality of sections, thereby controlling the temperature of each divided space. For example, the temperature of each of the divided spaces may be controlled such that the temperature of the divided space at the rear stage is equal to or greater than the temperature of the divided space at the front stage in a temperature range of 150 to 315 ℃, preferably 250 to 315 ℃, more preferably 260 to 290 ℃.

When the spinning temperature is less than 150 ℃, uniform melting of polyethylene chips cannot be achieved due to the low spinning temperature, and thus spinning may be difficult. Meanwhile, when the spinning temperature exceeds 315 ℃, thermal decomposition of polyethylene is caused, and thus it may be difficult to exhibit high strength.

The spinneret 200 can have a ratio L/D of the hole length L to the hole diameter D of 3 to 40. When L/D is less than 3, a die swell (dieswell) phenomenon occurs during melt extrusion, and it becomes difficult to control the elastic behavior of polyethylene, resulting in poor spinnability. When the L/D exceeds 40, yarn breakage may occur due to a necking phenomenon of the polyethylene melt passing through the spinneret 200, and an irregular discharge phenomenon may also occur due to a pressure drop.

Also, a method of making a polyethylene yarn of one embodiment may include cooling a plurality of filaments formed as a polyethylene melt is discharged from a nozzle orifice.

When the polyethylene melt is discharged from the nozzle holes of the spinneret 200, the polyethylene melt starts to solidify due to the difference between the spinning temperature and the room temperature, and a plurality of filaments 11 in a semi-solidified state are formed. In the present specification, not only semi-solidified filaments but also completely solidified filaments are collectively referred to as "filaments".

The plurality of filaments 11 are completely solidified by cooling in a cooling section (or quenching zone) 300. The cooling of the filaments 11 may be performed by an air cooling method. For example, the cooling of the filaments 11 may be performed at 15 ℃ to 40 ℃ using cooling air having a wind speed of 0.2m/sec to 1 m/sec. When the cooling temperature is less than 15 ℃, yarn breakage may occur during subsequent drawing due to insufficient elongation caused by supercooling. When the cooling temperature exceeds 40 ℃, deviation in fineness among the filaments 11 increases due to irregular solidification, and yarn breakage may occur during drawing.

Also, a method of making a polyethylene yarn of one embodiment may include converging the cooled plurality of filaments to form a multifilament yarn.

For example, the cooled and fully solidified filaments 11 are gathered by a gathering device 400 to form a multifilament yarn 10.

As shown in fig. 1, a oiling process (oiling process) of applying oil to the cooled filaments 11 using an Oil Roll (OR) OR an oil sprayer may be further performed before forming the multifilament yarn 10. The oiling process may also be performed by a Metered Oiling (MO) method.

Alternatively, the oiling-up step may be performed simultaneously when the filaments 11 are gathered to form the multifilament yarn 10, and an additional oiling-up step may be further performed during the drawing step and/or immediately before the winding step.

Meanwhile, the manufacturing method of the polyethylene yarn of one embodiment may include drawing and heat-setting the multifilament yarn at a total drawing ratio of 8 times to 20 times.

At this time, the drawing step may be performed using a plurality of godets, and the heat-setting of the multifilament yarn may be performed by a plurality of godets.

Specifically, the multifilament yarn 10 may be drawn at an overall draw ratio of 8 to 20 times, more preferably 10 to 15 times.

In order to provide the final polyethylene yarn with a strength of 11g/d or more, the multifilament yarn 10 must be drawn at a total draw ratio of 8 times or more. However, if more than 20 times the total draw ratio is applied in the drawing step, the risk of yarn breakage of the filament(s) 11 increases.

Meanwhile, the stretching step may be performed in a multi-stage stretching manner, and a relaxation rate at the time of final stretching during the multi-stage stretching may be 3% to 8%.

The present inventors have confirmed that the initial modulus and elongation of a polyethylene yarn during spinning of polyethylene used as a raw material are mainly affected by the relaxation rate at the time of final drawing during multi-stage drawing.

The relaxation rate at the time of final stretching means a relaxation rate at the time when stretching is performed last after stretching but before winding.

In order for the polyethylene yarn to have an initial modulus of 250g/d or less and an elongation of 6% or more, the relaxation rate at the final stretching during the multistage stretching in the production of the polyethylene yarn should be 3% to 8%, or 4% to 6%. At this time, if the relaxation rate at the time of final drawing is too high, it may be difficult to manufacture a polyethylene yarn having a high strength of 11g/d or more.

Specifically, when the relaxation rate at the time of final stretching is 3% or less, the modulus of the resulting yarn is 250g/d or more, which causes a problem in flexibility. When the relaxation rate is 8% or more, the yarn on the godet roll may move vigorously, and production difficulties may occur.

Therefore, in order to manufacture a polyethylene yarn having a reduced initial modulus, a high elongation, and improved wearability, it is preferable to apply the relaxation rate of the final drawing in the multistage drawing process to the above range.

The polyethylene yarn of the present invention can be produced by winding the multifilament yarn 10 as an undrawn yarn at one time, and then unwinding and drawing the undrawn yarn. As shown in fig. 1, the polyethylene yarn may also be manufactured by direct drawing using a drawing section 500 including a plurality of godet rolls gr1.. GRn without winding the multifilament yarn 10 as an undrawn yarn.

Whichever of the above two steps is applied, in order to minimize the risk of yarn breakage of the filament(s) 11 when drawing the multifilament yarn 10 at a large total draw ratio of 8 to 20 times, it is necessary to precisely control the drawing step. Further, as described above, it is preferable that the relaxation rate of the final stretching portion of the godet roll is 3% to 8% or less at the time of stretching.

Meanwhile, a method of manufacturing a polyethylene yarn of one embodiment may include winding the drawn multifilament yarn.

As shown in fig. 1, an entanglement step may be further performed by an entanglement unit 600 before winding the drawn multifilament yarn 10 on a winder 700 to improve convergence and braiding of the polyethylene yarn.

The polyethylene yarn of the present invention manufactured as above can be used for producing protective articles (e.g., protective gloves, underwear, bags, etc.) requiring excellent cut resistance.

Hereinafter, a protective article according to an embodiment of the present invention will be described in detail.

The protective article of the present invention is a protective article knitted with covered yarn (covered yarn), and may be, for example, a protective glove.

The covering yarn includes the polyethylene yarn of the present invention, a polyurethane yarn (e.g., spandex) spirally surrounding the polyethylene yarn, and a polyamide yarn (e.g., nylon 6 or nylon 66 yarn) spirally surrounding the polyethylene yarn. Polyamide yarns, including polyester yarns (e.g., PET yarns), may be substituted depending on the properties of the article desired.

The weight of the polyethylene yarn may be 45% to 85% of the total weight of the cover yarn, the weight of the polyurethane yarn may be 5% to 30% of the total weight of the cover yarn, and the weight of the polyamide yarn or the polyester yarn may be 5% to 30% of the total weight of the cover yarn.

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

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

Further, the polyethylene yarn may have a dry heat shrinkage at 100 ℃ of more than 2.5% and 6% or less.

Further, the polyethylene yarn may have a retention of storage elasticity at 50 ℃ of 65% to 75%, a retention of storage elasticity at 80 ℃ of 30% to 45%, and a retention of storage elasticity at 105 ℃ of 10% to 25%.

The protective article of the present invention has a cut resistance index of 5 or more and a low stiffness of 5gf or less, and thus can exhibit excellent cut resistance and excellent wearability.

Specifically, according to EN 388: 2016, the cut resistance index of the protective article may be: 5.0 or more, or 5.5 or more, or 5.7 or more; and is 8.5 or less, or 8.0 or less, or 7.5 or less, or 7.0 or less, or 6.8 or less. For example, according to EN 388: 2016, the cut resistance index of the protective article may 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.

At the same time, the stiffness of the protective article may be: 5.0gf or less or 4.5gf or less; and 2.0gf or more, or 3.0gf or more, or 3.5gf or more, or 3.8gf or more. For example, the stiffness of the protective article may 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 4.5 gf.

Hereinafter, the present invention will be described in detail with reference to specific examples and comparative examples. However, these examples are only for helping the understanding of the present invention, and the scope of the present invention should not be limited thereto.

Production of polyethylene yarn

Preparation of example 1

A polyethylene multifilament entangled yarn containing 240 filaments and having a total fineness of 400 denier was manufactured using the apparatus shown in fig. 1.

Specifically, polyethylene chips having a weight average molecular weight (Mw) of 150,000g/mol and a Melt Index (MI) of 1g/10min (190 ℃) were introduced into the extruder 100 and melted. The polyethylene melt was extruded through a spinneret 200 having 240 nozzle holes.

The filaments 11 formed while being discharged from the nozzle holes of the spinneret 200 are cooled in the cooling section 300 and then collected into the multifilament yarn 10 by the collecting device 400.

Next, the multifilament yarn was drawn and heat-set at a total draw ratio of 12 times by a godet set to 70 to 130 ℃ in a drawing section 500.

The stretching step was performed in a multi-stage stretching manner, and the relaxation rate at the time of final stretching during the multi-stage stretching was 8%.

Next, the drawn multifilament yarn was entangled at 6.0kgf/cm in an entangling device 600²Is entangled and then wound in the winder 700. The winding tension was 0.6 g/d.

Preparation of example 2

A polyethylene yarn was obtained in the same manner as in example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 150,000g/mol and a Melt Index (MI) (at 190 ℃) of 1g/10min were used and the relaxation rate at the time of final stretching during multistage stretching was 5%.

Preparation of example 3

A polyethylene yarn was obtained in the same manner as in example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 180,000g/mol and a Melt Index (MI) (at 190 ℃) of 0.8g/10min were used and the relaxation rate at the time of final stretching during multi-stage stretching was 3%.

Preparation of comparative example 1

A polyethylene yarn was obtained in the same manner as in example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 200,000g/mol and a Melt Index (MI) (at 190 ℃) of 0.6g/10min were used and the relaxation rate at the time of final stretching during multistage stretching was 2%.

Preparation of comparative example 2

A polyethylene yarn was obtained in the same manner as in example 1, except that polyethylene chips having a weight average molecular weight (Mw) of 200,000g/mol and a Melt Index (MI) (at 190 ℃) of 0.6g/10min were used and the relaxation rate at the time of final stretching during multi-stage stretching was 10%.

Test example 1

The strength, initial modulus, elongation, dry heat shrinkage, storage elastic retention rate, and weight average molecular weight (Mw) of the polyethylene yarn 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.

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

The strength, elongation and initial modulus of polyethylene yarns were determined by obtaining strain-stress curves of the polyethylene yarns using an Instron Engineering corp. canton, Mass according to test method ASTM D885. Specifically, the sample length was set to 250mm, the drawing speed was set to 300mm/min, and the initial load was set to 0.05 g/d. The initial modulus (g/d) is determined by the tangent giving the maximum gradient near the origin. After 5 measurements for each polyethylene yarn, the average was calculated.

(2) Dry heat shrinkage ratio

The polyethylene yarn was cut to give a sample having a length of 70cm, and then marked at points 10cm from both ends of the sample (i.e., the distance between the marked points was 50 cm).

Then, the sample was heated at 100 ℃ for 30 minutes using a hot air circulation type heating furnace in a state of being suspended on a jig so that no load was applied to the sample. Thereafter, the sample was taken out of the heating furnace, slowly cooled to room temperature, and the distance between the marked points was measured. Then, the dry heat shrinkage of the polyethylene yarn at 100 ℃ was calculated using the following formula 1.

-formula 1: dry heat shrinkage (%) (I)₀-I₁)/I₀]×100

(wherein, I)₀Distance between marked points before heating (i.e. 50cm), I₁For distance between the marks after heating)

The average of the dry heat shrinkage obtained by the two tests was obtained.

(3) Retention of storage elasticity

After preparing a polyethylene yarn sample having a length of 10mm, storage elastic moduli at 30 ℃, 50 ℃, 80 ℃ and 105 ℃ were measured using an intrinsic viscoelasticity measuring apparatus (manufactured by t.a. instruments, DMAQ800), respectively. Specifically, both ends of the sample were sandwiched between thick papers using an adhesive and a double-sided tape so that no slippage or scattering of the filaments occurred between the sample and the device during measurement. The measurement start temperature was set to-10 ℃, the measurement end temperature was set to 140 ℃, and the temperature rise rate was set to 1.0 ℃/min. The deformation amount was set to 0.04%, the initial load at the start of measurement was set to 0.05cN/dtex, and the measurement frequency was set to 11 Hz. Data were analyzed using "TA Universal Analysis" (manufactured by t.a. instruments). The retention rate of storage elasticity at 50 ℃, the retention rate of storage elasticity at 80 ℃ and the retention rate of storage elasticity at 105 ℃ were respectively calculated by the following formula 2.

-formula 2: storage elasticity retention (%) at T ℃ ═ (storage elastic modulus at T ℃/storage elastic modulus at 30 ℃) × 100 (wherein T ℃ ═ 50 ℃/80 ℃/105 ℃)

(4) Weight average molecular weight (Mw) (g/mol) and polydispersity index (PDI)

The polyethylene yarn was completely dissolved in the following solvents, and then the weight average molecular weight (Mw), the number average molecular weight (Mn), and the polydispersity index (Mw/Mn: PDI) of the polyethylene yarn were respectively determined using the following Gel Permeation Chromatography (GPC).

-an analytical instrument: PL-GPC 220 system

-a column: 2 XPPLGEL MIXED-B (7.5X 300mm)

Column temperature: 160 deg.C

-a solvent: trichlorobenzene (TCB) + 0.04% by weight of dibutylhydroxytoluene (BHT) (with 0.1% CaCl₂After drying)

-dissolution conditions: after dissolution at 160 ℃ for 1 to 4 hours, the solution passing through a glass filter (0.7 μm) was measured

Injector, detector temperature: 160 deg.C

-a detector: RI detector

-flow rate: 1.0ml/min

-injection volume: 200 μ l

-standard sample: polystyrene

TABLE 1

< production of protective gloves >

Example 1

A covering yarn was produced by spirally surrounding the polyethylene yarn of preparation example 1 with 140 denier polyurethane yarn (spandex) and 140 denier nylon yarn. The weight of the polyethylene yarn was 60% of the total weight of the covering yarn, and the weight of the polyurethane yarn and the nylon yarn were each 20% of the total weight of the covering yarn. The covering yarn is knitted to produce protective gloves.

Example 2

A protective glove was obtained in the same manner as in example 1, except that the polyethylene yarn of preparation example 2 was used.

Example 3

A protective glove was obtained in the same manner as in example 1, except that the polyethylene yarn of preparation example 3 was used.

Comparative example 1

A protective glove was obtained in the same manner as in example 1, except that the polyethylene yarn of preparation comparative example 1 was used.

Comparative example 2

A protective glove was obtained in the same manner as in example 1, except that the polyethylene yarn of preparation comparative example 2 was used.

Test example 2

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, respectively, and the results are shown in table 2 below.

(1) Cut resistance index (CI)

According to EN 388: 2016, measure cut resistance index of protective gloves.

(2) Stiffness (gf)

As shown in FIGS. 2 and 3, after collecting a test piece (width: 60mm, length: 60mm)21 from the palm portion of the protective glove 20, the stiffness of the test piece was measured according to section 38 of ASTM D885/D885M-10a (2014). The measurement apparatus is as follows.

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

(ii) Loading Unit, 2KN [200kgf ]

(iii) Sample holder: sample holder as defined in section 38.4.3

(iv) A sample presser: the sample press defined in section 38.4.4.

Specifically, the side (21a) adjacent to the fingers of the glove and the opposite side 21b thereof (i.e., the side adjacent to the wrist of the glove) with the outer glove surface (f1) of the sample (21) facing upward and the inner glove surface (f2) facing downward are placed in the center of the sample holder 31, with the sample 21 being directly supported by the sample holder 31. The test piece 21 remains flat and does not bend. At this time, the distance between the sample support portion of the sample holder 31 and the pressing portion of the sample presser 32 was 5 mm. Then, the maximum strength was measured while lifting the sample holder 31 to 15mm with the sample presser 32 kept stationary.

TABLE 2

From table 2 above, it was confirmed that the protective gloves of examples 1 to 3 produced using the polyethylene yarns according to the preparation examples 1 to 3 had low stiffness while having excellent cut resistance, and thus had improved wearability as compared to comparative examples 1 and 2.