Polyethylene resin composition, method for preparing the same, and article made therefrom

Abstract

The present disclosure relates to a polyethylene resin composition, a method of preparing the same, and an article made therefrom. Disclosed is a polyethylene resin composition including an ethylene copolymer including ethylene monomer units and comonomer units, wherein the content of the comonomer units is 2 to 15 wt% based on the total weight of the ethylene copolymer, the content of the ethylene copolymer is 45 to 57 wt% based on the total weight of the polyethylene resin composition, the content of a peroxide is 0.001 to 0.01 parts by weight based on 100 parts by weight of the polyethylene resin composition, and the ethylene copolymer has a melt flow index MI21.6 (21.6 kg load, 190°C) of 0.26 to 0.50 g / 10 min.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0171931, filed with the Korean Intellectual Property Office on November 27, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a polyethylene resin composition having excellent anti-sagging properties, resistance to slow crack growth, pressure resistance, and suitability for large-diameter pipes, a method for preparing the composition thereof, and articles made therefrom. Background Technology

[0004] Pipes made of polyethylene have been widely used in water pipes, gas pipes, and industrial pipelines. With improvements in its resistance to slow crack growth and sag resistance, various applications are gradually shifting towards PE100-RC grade. Compared to PE100 grade polyethylene, PE100-RC grade materials exhibit improved resistance to slow crack growth (RC). Due to the enhanced resistance to slow crack growth in PE100-RC polyethylene, non-traditional installation methods (trenchless, sand-free technology, etc.) can be employed, thereby reducing installation costs and time compared to traditional methods.

[0005] Furthermore, as the long-term durability of large-diameter pipelines used in power plant cooling water transportation, seawater desalination, fire-fighting pipelines, integrated energy terminals, and agriculture and fisheries becomes increasingly important, the demand for polyethylene materials that resist slow crack growth is also constantly increasing.

[0006] Generally, diameters of 800 mm or larger are classified as large diameter. As thickness increases, sag in the direction of gravity increases significantly during pipe fabrication; therefore, polyethylene materials used in large-diameter pipes generally require sag resistance. This sag phenomenon can occur not only in large-diameter pipes but also in medium-diameter (630 mm) or larger polyethylene pipes. Consequently, with the expansion of the polyethylene pipe market, the demand for polyethylene materials with high sag resistance is also increasing.

[0007] Generally, polyethylene materials should possess a molecular structure in which the connecting molecules are highly entangled to enhance their resistance to slow crack growth. For this purpose, high molecular weight or high carbon number comonomers are typically used. However, the resistance to slow crack growth in polyethylene materials is directly related to crystallinity (i.e., density). While increasing density improves the pressure resistance of the pipe, it significantly reduces resistance to slow crack growth.

[0008] On the other hand, during the processing of large-diameter pipes, due to differences in the cooling rate of the molten products, the pipes will sag under their own weight, increasing the incidence of pipe defects such as uneven thickness. To solve this problem, it is necessary to enhance the anti-sag properties.

[0009] Therefore, there is a need to develop a polyethylene resin composition that possesses both excellent pressure resistance and resistance to slow crack growth (contradictory properties) and high resistance to sag.

[0010] [Existing technical documents]

[0011] [Patent Documents]

[0012] Korean Patent Publication No. 10-2020-0101872 Summary of the Invention

[0013] The embodiments of this disclosure provide a polyethylene resin composition with excellent anti-sagging, anti-slow crack growth, and pressure resistance.

[0014] The embodiments of this disclosure provide a method for preparing a polyethylene resin composition.

[0015] Embodiments of this disclosure provide an article of manufacture made from a polyethylene resin composition.

[0016] The objectives of this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the following description other objectives not mentioned herein.

[0017] To achieve the above objectives, the polyethylene resin composition according to the present disclosure may comprise an ethylene copolymer comprising ethylene monomer units and comonomer units, wherein, based on the total weight of the ethylene copolymer, the content of the comonomer units is 2% to 15% by weight, the content of the ethylene copolymer is 45% to 57% by weight based on the total weight of the polyethylene resin composition, the content of peroxide is 0.001 to 0.01 parts by weight based on 100 parts by weight of the polyethylene resin composition, and the ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190°C) of 0.26 g / 10 min to 0.50 g / 10 min.

[0018] The comonomer may include at least one of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicosene.

[0019] Ethylene copolymers can have a content of 0.915 g / cm³. 3 Up to 0.935 g / cm 3The density.

[0020] The polyethylene resin composition may have a zero shear viscosity (η0) of 12,000,000 poise to 50,000,000 poise.

[0021] The peroxide in the polyethylene resin composition may include at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, tert-butylperoxyisopropylbenzene, 1,1-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-(dibutylperoxy)valerate, diisopropylbenzene peroxide, tert-butyl peroxide, tert-butylperoxybenzoate, and 1,1-bis(tert-butylperoxyisopropyl)benzene.

[0022] Ethylene copolymers can have a melt index MI5 (5 kg load, 190 °C) of 0.14 g / 10 min to 0.28 g / 10 min.

[0023] The polyethylene resin composition may have a content of 0.956 g / cm³. 3 Up to 0.962 g / cm 3 The density.

[0024] The polyethylene resin composition has a melt strength of 135 mN to 300 mN.

[0025] The polyethylene resin composition can have a dripping time of 130 seconds to 200 seconds.

[0026] The polyethylene resin composition may have 1,500,000 or higher CRB (round bar crack test, 12.5 MPa).

[0027] The polyethylene resin composition may have a strain hardening modulus of 70 MPa to 90 MPa.

[0028] The polyethylene resin composition exhibits a fracture time of 100 hours or longer in a pipeline hydrostatic pressure test at 20°C and 12.0 MPa.

[0029] The polyethylene resin composition may have 10 kJ / m 2 Up to 25kJ / m 2 The impact strength of the cyclohexane (-30℃).

[0030] Polyethylene resin compositions can be used to produce pipes.

[0031] According to another embodiment of this disclosure, in order to achieve the above-mentioned objective, a method for preparing a polyethylene resin composition may include: preparing a polyethylene resin composition comprising an ethylene copolymer using ethylene monomers and comonomers in the presence of a catalyst in a plurality of slurry polymerization reactors comprising a first reactor and a second reactor connected to each other; mixing the polyethylene resin composition with an additive comprising a peroxide; and extruding the mixture of the polyethylene resin composition and the additive by an extruder, wherein the content of comonomer units is 2% to 15% by weight based on the total weight of the ethylene copolymer, the content of ethylene copolymer is 45% to 57% by weight based on the total weight of the polyethylene resin composition, the content of peroxide is 0.001 parts by weight to 0.01 parts by weight based on 100 parts by weight of the polyethylene resin composition, and the ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190 °C) of 0.26 g / 10 min to 0.50 g / 10 min.

[0032] The catalyst can be a Ziegler-Natta catalyst.

[0033] According to another embodiment of this disclosure, the article that achieves the above-mentioned objective can be produced from a polyethylene resin composition.

[0034] The product can be a pipe. Detailed Implementation

[0035] The advantages and features of this disclosure, as well as the methods for achieving these advantages and features, will become clearer and more understandable through the following detailed description of the embodiments. However, this disclosure is not limited to these embodiments and may be embodied in different forms. These embodiments are only intended to help those skilled in the art to fully understand this disclosure and to fully inform the technical concepts of this disclosure, which is limited only by the scope of the claims.

[0036] Before beginning the description, the meanings of the terms used herein will be briefly explained. However, the explanations of the terms are for the purpose of better understanding this disclosure, and unless the context clearly indicates that these terms are used to limit the scope of this disclosure, they should not be construed as limiting the technical ideas of this disclosure.

[0037] The terminology used herein is for illustrative purposes only and should not be construed as limiting the scope of this disclosure. Unless the context clearly indicates otherwise, the singular form also includes the plural form. It should also be understood that the terms “comprising” and / or “including” as used herein do not exclude the presence or addition of one or more other components besides those described. The terms “and / or” as used herein include any of the listed items and any combination thereof. It should be understood that although terms such as “first,” “second,” etc., may be used herein to describe various elements, these elements should not be construed as being limited by these terms, which are used only to distinguish one element from another. For example, within the scope defined by this disclosure, a first element may be referred to as a second element.

[0038] Unless otherwise defined, all terms used herein (including technical or scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Furthermore, terms identical to those defined in commonly used dictionaries shall be interpreted as having the same meaning as in the context of the relevant field, and shall not be construed as having an idealized or overly formal meaning unless expressly defined herein.

[0039] The implementation scheme of this disclosure will now be described in detail.

[0040] According to one embodiment, this disclosure provides a polyethylene resin composition. The polyethylene resin composition may comprise an ethylene copolymer, the ethylene copolymer comprising ethylene monomer units and comonomer units, wherein the content of comonomer units is 2% to 15% by weight based on the total weight of the ethylene copolymer, the content of the ethylene copolymer is 45% to 57% by weight based on the total weight of the polyethylene resin composition, the content of peroxide is 0.001 parts by weight to 0.01 parts by weight based on 100 parts by weight of the polyethylene resin composition, and the ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190°C) of 0.26 g / 10 min to 0.50 g / 10 min.

[0041] In one embodiment, the comonomer may include at least one selected from 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicosene. As a specific example, the comonomer may be 1-hexene.

[0042] Based on the total weight of the ethylene copolymer, the content of comonomer units can be 2% to 15% by weight, 3% to 12% by weight, or 3% to 9% by weight. When the ethylene copolymer contains comonomers in amounts within the above ranges, its compressive strength and resistance to slow crack growth can be excellent.

[0043] In one embodiment, the polyethylene resin composition may contain 45% to 57% by weight or 47% to 57% by weight of an ethylene copolymer, based on the total weight of the polyethylene resin composition. Polyethylene resin compositions containing amounts of ethylene copolymer within the above range exhibit excellent anti-sagging properties, resistance to slow crack growth, and pressure resistance.

[0044] In one embodiment, the ethylene copolymer may have a melt index MI21.6 (21.6 kg load, 190 °C) of 0.26 to 0.50 g / 10 min, 0.26 to 0.45 g / 10 min, or 0.28 to 0.40 g / 10 min. The melt index MI21.6 of the ethylene copolymer is measured using a die with an inner diameter of 2.75 mm at 190 °C and 21.6 kg load. When the polyethylene resin composition contains an ethylene copolymer with a melt index MI21.6 within the above range, it exhibits excellent resistance to slow crack growth and compressive strength, as well as an improved appearance.

[0045] In one embodiment, the density of the ethylene copolymer may be 0.915 g / cm³. 3 Up to 0.935 g / cm 3 0.915g / cm 3 Up to 0.923 g / cm 3 Or 0.917 g / cm 3 Up to 0.921 g / cm 3 When a polyethylene resin composition contains an ethylene copolymer with a density within the above range, it can simultaneously exhibit excellent pressure resistance and resistance to slow crack growth in the pipe.

[0046] In one embodiment, the polyethylene resin composition may have a melt index MI5 (5 kg load, 190 °C) of 0.14 to 0.28 g / 10 min, 0.15 to 0.24 g / 10 min, 0.15 to 0.22 g / 10 min, or 0.15 to 0.20 g / 10 min. The melt index MI5 of the polyethylene resin composition is measured using a die with an inner diameter of 2.095 mm at 190 °C and a 5 kg load. Because the melt index MI5 of the polyethylene resin composition is within the above range, it exhibits excellent anti-sagging properties, melt strength, and processability.

[0047] In one embodiment, the density of the polyethylene resin composition may be 0.956 g / cm³. 3 Up to 0.962 g / cm 3 0.956 g / cm 3 Up to 0.960 g / cm 3 0.956 g / cm 3 Up to 0.959 g / cm 3Or 0.957 g / cm 3 Up to 0.959 g / cm 3 Polyethylene resin compositions with densities within the aforementioned range can prevent pipe sagging while exhibiting excellent pressure resistance and resistance to slow crack growth.

[0048] In one embodiment, the zero-shear viscosity (η0) of the polyethylene resin composition can be from 12,000,000 poise to 50,000,000 poise, 15,000,000 poise to 35,000,000 poise, 20,000,000 poise to 35,000,000 poise, or 25,000,000 poise to 35,000,000 poise. The zero-shear viscosity can be obtained by measuring the storage modulus and loss modulus, which depend on the shear rate (in rad / sec). When the zero-shear viscosity of the polyethylene resin composition is within the above range, the sagging problem caused by thickness imbalance when the polyethylene resin composition flows in the direction of gravity at the cooling front during pipe extrusion processing can be solved.

[0049] In one embodiment, the polyethylene resin composition may include an additive comprising a peroxide. The peroxide may include at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, tert-butylperoxyisopropylbenzene, 1,1-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-(dibutylperoxy)valerate, dicumyl peroxide, tert-butyl peroxide, tert-butylperoxybenzoate, and 1,1-bis(tert-butylperoxyisopropyl)benzene. As a specific example, the peroxide may include at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, and tert-butylperoxide.

[0050] The peroxide content can be 0.001 to 0.01 parts by weight, 0.001 to 0.008 parts by weight, or 0.002 to 0.007 parts by weight, based on 100 parts by weight of the polyethylene resin composition. When the peroxide content is within the above range, sagging can be prevented and processing performance can be improved.

[0051] In one embodiment, the additive may further include at least one selected from the group consisting of antioxidants and neutralizers. The content of antioxidants and neutralizers may be appropriately adjusted to amounts commonly used in the art. For example, based on 100 parts by weight of the polyethylene resin composition, the content of antioxidants and neutralizers may be from 0.1 to 5 parts by weight.

[0052] There are no particular restrictions on the types of antioxidants, but antioxidants include at least one selected from the group consisting of: 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propamido]hexane, 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propamido]propane, tetra[methylene(3,5-di-tert-butyl-4-hydroxyhydrogenated methyl)]hexane, and methyl[3,5-di-tert-butyl-4-hydroxyphenyl]propane. [Cinnamyl ester]methane, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6-trione, bis(octadecyl)hydroxylamine, tris(2,4-di-tert-butylphenyl)phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite. As a specific example, the antioxidant may be a mixture of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate and tris(2,4-di-tert-butylphenyl)phosphite.

[0053] Based on 100 parts by weight of the polyethylene resin composition, the antioxidant content can be 0.1 to 5 parts by weight, or 0.2 to 0.4 parts by weight. When the antioxidant content is within the above range, corrosion and discoloration of the pipeline due to oxidation can be prevented.

[0054] There are no particular restrictions on the type of neutralizing agent, but it may include at least one selected from the group consisting of calcium stearate, zinc stearate, basic aluminum magnesium carbonate, zinc oxide, and basic magnesium stearate. As a specific example, the neutralizing agent may be calcium stearate.

[0055] Based on 100 parts by weight of polyethylene resin composition, the content of neutralizing agent can be 0.01 to 0.3 parts by weight, or 0.1 to 0.2 parts by weight. When the content of neutralizing agent is within the above range, the pipe's resistance to sag, resistance to slow crack growth, and processability are all improved.

[0056] In one embodiment, the melt strength of the prepared polyethylene resin composition can be from 135 mN to 300 mN, 135 mN to 250 mN, 145 mN to 240 mN, or 155 mN to 230 mN. Melt strength can be obtained by measuring the force that stabilizes with increasing resin stretching speed at a resin temperature of 200°C and a chamber temperature of 180°C. When the melt strength of the polyethylene resin composition is within the above range, the polyethylene resin exhibits excellent anti-sagging properties during pipe processing, especially in the processing of large-diameter pipes, and is therefore suitable for large-diameter pipes.

[0057] In one embodiment, the dripping time of the polyethylene resin composition can be 130 to 200 seconds, 135 to 195 seconds, or 140 to 190 seconds. When extruded to a height of 90.5 cm above the ground using a single-screw extruder at an extrusion temperature of 200°C, an extrusion rate of 38.1 g / min, and an initial linear velocity of 0.546 cm / s, the time it takes for the extruded molten product to reach the ground (dripping time, seconds) can be measured to evaluate sag resistance. When the dripping time is within this range, excellent anti-sag properties are obtained during pipe processing, especially in the processing of large-diameter pipes; therefore, this polyethylene resin composition is suitable for large-diameter pipes.

[0058] The CRB (round bar crack test, 12.5 MPa) of the polyethylene resin composition can be 1,500,000 cycles or more, 1,500,000 to 3,500,000 cycles, 1,700,000 to 3,000,000 cycles, or 1,800,000 to 2,500,000 cycles. When the CRB falls within the above range, the pipe exhibits excellent resistance to slow crack growth, and therefore can be easily manufactured using unconventional installation techniques.

[0059] The polyethylene resin composition may have a strain hardening modulus of 70 MPa to 90 MPa, 75 MPa to 90 MPa, or 75 MPa to 85 MPa. When the strain hardening modulus is within the above range, pipes with excellent long-term stability can be provided due to improved resistance to slow crack growth.

[0060] In one embodiment, the prepared polyethylene resin composition exhibits a rupture time of 100 hours or longer, 150 hours or longer, or 100 hours to 500 hours under hydrostatic pressure testing of pipes at 20°C and 12.0 MPa. The pressure resistance of the pipe is measured according to ISO 1167 standard; specifically, the rupture time can be measured after fabrication of a pipe with a nominal diameter of 32 mm (SDR11) under conditions of 20°C and a circumferential stress of 12.0 MPa. When the rupture time is less than 100 hours, it does not meet the minimum required strength standard for PE100 material and is therefore unsuitable for gas pipes, water pipes, etc.

[0061] The Chippen impact strength (-30℃) of the polyethylene resin composition can be 10 kJ / m. 2 Up to 25kJ / m 2 15kJ / m 2 Up to 25kJ / m 2 or 15kJ / m 2 Up to 20kJ / m 2 When the impact strength of the pipe is within the above range, pipes with excellent impact strength can be manufactured.

[0062] In one embodiment, the polyethylene resin composition can be used in pipe manufacturing, specifically for the manufacturing of large-diameter pipes.

[0063] Because the above-mentioned polyethylene resin composition has excellent anti-sagging, anti-slow crack growth and pressure resistance, it can be used for large-diameter pipes.

[0064] In one embodiment, this disclosure provides a method for preparing a polyethylene resin composition. The method for preparing the polyethylene resin composition includes: preparing a polyethylene resin composition containing an ethylene copolymer using ethylene monomers and comonomers in the presence of a catalyst in a plurality of slurry polymerization reactors comprising a first reactor and a second reactor connected to each other; mixing the polyethylene resin composition with an additive including a peroxide; and extruding the mixture of the polyethylene resin composition and the additive using an extruder, wherein the content of comonomer units is 2% to 15% by weight based on the total weight of the ethylene copolymer, the content of the ethylene copolymer is 45% to 57% by weight based on the total weight of the polyethylene resin composition, the content of peroxide is 0.001 to 0.01 parts by weight based on 100 parts by weight of the polyethylene resin composition, and the ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190°C) of 0.26 g / 10 min to 0.50 g / 10 min.

[0065] In one embodiment, the catalyst may be a Ziegler-Natta catalyst. The slurry polymerization reaction can be carried out in the presence of the Ziegler-Natta catalyst. Specifically, the polyethylene resin composition can be polymerized in a two-stage manner, using a first reactor and a second reactor in series, in the presence of the Ziegler-Natta catalyst, by adding ethylene monomers and comonomers for slurry polymerization.

[0066] Ziegler-Natta catalysts are the known conventional Ziegler-Natta catalysts. Transition metal compounds belonging to Groups IV, V, or VI of the periodic table can be used as main catalysts. The most commonly used Ziegler-Natta catalysts are magnesium and titanium-containing, or magnesium and vanadium-containing halide complexes.

[0067] The comonomer may include at least one selected from 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicosene. As a specific example, the comonomer may be 1-hexene.

[0068] Based on the total weight of the ethylene copolymer, the content of comonomer units can be 2% to 15% by weight, 3% to 12% by weight, or 3% to 9% by weight. When the comonomer content of the ethylene copolymer is within the above range, its pressure resistance and resistance to slow crack growth can be excellent.

[0069] In one embodiment, the prepared polyethylene resin composition may contain 45% to 57% by weight or 47% to 57% by weight of an ethylene copolymer, based on the total weight of the polyethylene resin composition. Polyethylene resin compositions with ethylene copolymer content within the above range exhibit excellent anti-sagging properties, resistance to slow crack growth, and pressure resistance.

[0070] In one embodiment, the prepared ethylene copolymer may have a melt index MI of 21.6 (21.6 kg load, 190 °C) of 0.26 g / 10 min to 0.50 g / 10 min, 0.26 g / 10 min to 0.45 g / 10 min, or 0.28 g / 10 min to 0.40 g / 10 min. The melt index MI of the ethylene copolymer is measured using a die with an inner diameter of 2.75 mm at 190 °C and 21.6 kg load. When the polyethylene resin composition contains an ethylene copolymer with a melt index MI of 21.6 within the above range, it exhibits excellent resistance to slow crack growth and compressive strength, as well as an improved appearance.

[0071] In one embodiment, the density of the ethylene copolymer contained in the prepared polyethylene resin composition may be 0.915 g / cm³. 3 Up to 0.935 g / cm 3 0.915g / cm 3 Up to 0.923 g / cm 3 Or 0.917 g / cm 3 Up to 0.921 g / cm 3 When a polyethylene resin composition contains an ethylene copolymer with a density within the above range, it can simultaneously exhibit excellent pressure resistance and resistance to slow crack growth in the pipe.

[0072] In one embodiment, the polyethylene resin composition may have a melt index MI5 (5 kg load, 190 °C) of 0.14 g / 10 min to 0.28 g / 10 min, 0.15 g / 10 min to 0.24 g / 10 min, 0.15 g / 10 min to 0.22 g / 10 min, or 0.15 g / 10 min to 0.20 g / 10 min. The melt index MI5 of the polyethylene resin composition is measured using a die with an inner diameter of 2.095 mm at 190 °C and a 5 kg load. Because the melt index MI5 of the polyethylene resin composition is within the above range, it exhibits excellent anti-sagging properties, melt strength, and processability.

[0073] In one embodiment, the density of the polyethylene resin composition may be 0.956 g / cm³. 3 Up to 0.962 g / cm 3 0.956 g / cm 3 Up to 0.960 g / cm 3 0.956 g / cm 3 Up to 0.959 g / cm 3 Or 0.957 g / cm 3 Up to 0.959 g / cm 3 Polyethylene resin compositions with densities within the aforementioned range can prevent pipe sagging while exhibiting excellent pressure resistance and resistance to slow crack growth.

[0074] In one embodiment, the zero-shear viscosity (η0) of the polyethylene resin composition can be from 12,000,000 poise to 50,000,000 poise, 15,000,000 poise to 35,000,000 poise, 20,000,000 poise to 35,000,000 poise, or 25,000,000 poise to 35,000,000 poise. The zero-shear viscosity can be obtained by measuring the storage modulus and loss modulus, which depend on the shear rate (in rad / sec). When the zero-shear viscosity of the polyethylene resin composition is within the above range, the sagging problem caused by thickness imbalance when the polyethylene resin composition flows in the direction of gravity at the cooling front during pipe extrusion processing can be solved.

[0075] In one embodiment, in the step of mixing the polyethylene resin composition with an additive including a peroxide, the peroxide may include at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, tert-butylperoxyisopropylbenzene, 1,1-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-(dibutylperoxy)valerate, dicumyl peroxide, tert-butyl peroxide, tert-butylperoxybenzoate, and 1,1-bis(tert-butylperoxyisopropyl)benzene. As a specific example, the peroxide may include at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, and tert-butylperoxide.

[0076] Based on 100 parts by weight of the polyethylene resin composition, the peroxide content can be 0.001 to 0.01 parts by weight, 0.001 to 0.008 parts by weight, or 0.002 to 0.007 parts by weight. When the peroxide content is within the above range, sagging can be prevented and processing performance can be improved.

[0077] In one embodiment, the additive may further include at least one selected from the group consisting of antioxidants and neutralizers. The content of antioxidants and neutralizers may be appropriately adjusted to amounts commonly used in the art. For example, based on 100 parts by weight of the polyethylene resin composition, the content of antioxidants and neutralizers may be from 0.1 to 5 parts by weight.

[0078] There are no particular restrictions on the types of antioxidants, but antioxidants include those selected from 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propamido]hexane, 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propamido]propane, tetra[methylene(3,5-di-tert-butyl-4-hydroxycinnamate)]methane, and pentaerythritol. At least one of the following groups: tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6-trione, bis(octadecyl)hydroxylamine, tris(2,4-di-tert-butylphenyl) phosphite, pentaerythritol diphosphite, and bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite. As a specific example, the antioxidant may be a mixture of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate and tris(2,4-di-tert-butylphenyl) phosphite.

[0079] Based on 100 parts by weight of the polyethylene resin composition, the antioxidant content can be 0.1 to 5 parts by weight, or 0.2 to 0.4 parts by weight. When the antioxidant content is within the above range, corrosion and discoloration of the pipeline due to oxidation can be prevented.

[0080] There are no particular restrictions on the type of neutralizing agent, but it may include at least one selected from the group consisting of calcium stearate, zinc stearate, basic aluminum magnesium carbonate, zinc oxide, and basic magnesium stearate. As a specific example, the neutralizing agent may be calcium stearate.

[0081] Based on 100 parts by weight of polyethylene resin composition, the content of neutralizing agent can be 0.01 to 0.3 parts by weight, or 0.1 to 0.2 parts by weight. When the content of neutralizing agent is within the above range, the pipe's resistance to sag, resistance to slow crack growth, and processability can all be improved.

[0082] In one embodiment, the melt strength of the prepared polyethylene resin composition can be from 135 mN to 300 mN, 135 mN to 250 mN, 145 mN to 240 mN, or 155 mN to 230 mN. Melt strength can be obtained by measuring the force that stabilizes with increasing resin stretching speed at a resin temperature of 200°C and a chamber temperature of 180°C. When the melt strength of the polyethylene resin composition is within the above range, the polyethylene resin exhibits excellent anti-sagging properties during pipe processing, especially in the processing of large-diameter pipes, and is therefore suitable for large-diameter pipes.

[0083] In one embodiment, the dripping time of the prepared polyethylene resin composition can be 130 to 200 seconds, 135 to 195 seconds, or 140 to 190 seconds. When extruded to a height of 90.5 cm above the ground using a single-screw extruder at an extrusion temperature of 200°C, an extrusion rate of 38.1 g / min, and an initial linear velocity of 0.546 cm / s, the time it takes for the extruded molten product to reach the ground (dripping time, seconds) can be measured to evaluate sag resistance. When the dripping time is within this range, excellent anti-sag properties can be obtained during pipe processing, especially in the processing of large-diameter pipes; therefore, the polyethylene resin composition is suitable for large-diameter pipes.

[0084] The CRB (round bar crack test, 12.5 MPa) of the polyethylene resin composition can be 1,500,000 cycles or more, 1,500,000 to 3,500,000 cycles, 1,700,000 to 3,000,000 cycles, or 1,800,000 to 2,500,000 cycles. When the CRB is within the above range, it exhibits excellent resistance to slow crack growth, thus allowing the pipes to be easily manufactured using unconventional installation techniques.

[0085] The polyethylene resin composition may have a strain hardening modulus of 70 MPa to 90 MPa, 75 MPa to 90 MPa, or 75 MPa to 85 MPa. When the strain hardening modulus is within the above range, pipes with excellent long-term stability can be provided due to improved resistance to slow crack growth.

[0086] In one embodiment, the prepared polyethylene resin composition exhibits a rupture time of 100 hours or longer, 150 hours or longer, or 100 hours to 500 hours under hydrostatic pressure testing of pipes at 20°C and 12.0 MPa. The pressure resistance of the pipe is measured according to ISO 1167; specifically, the rupture time can be measured after fabrication of a pipe with a nominal diameter of 32 mm (SDR11) under conditions of 20°C and a circumferential stress of 12.0 MPa. When the rupture time is less than 100 hours, it does not meet the minimum required strength standard for PE100 material and is therefore unsuitable for gas pipes, water pipes, etc.

[0087] The Chippen impact strength (-30℃) of the polyethylene resin composition can be 10 kJ / m. 2 Up to 25kJ / m 2 15kJ / m 2 Up to 25kJ / m 2 or 15kJ / m 2 Up to 20kJ / m 2 When the impact strength of the pipe is within the above range, pipes with excellent impact strength can be manufactured.

[0088] In one embodiment, in the step of extruding the mixture of the polyethylene resin composition and the additive, the extruder can be a single-screw extruder or a twin-screw extruder. As a specific example, the extruder can be a twin-screw extruder with a screw diameter of 500 mm to 800 mm, 550 mm to 750 mm, or 550 mm to 650 mm, and an L / D (screw length / screw diameter) of 5 to 10 or 7 to 10.

[0089] The extruder can operate at temperatures of 200°C to 300°C, 210°C to 270°C, or 230°C to 250°C and screw speeds of 1,000 rpm to 1,300 rpm, 1,000 rpm to 1,200 rpm, or 1,050 rpm to 1,150 rpm.

[0090] Furthermore, according to one embodiment, this disclosure provides articles made from the above-described polyethylene resin composition.

[0091] The product can be, for example, a pipe. The above-mentioned polyethylene resin composition has excellent anti-sagging properties, resistance to slow crack growth, and pressure resistance, and therefore can be used for pipes.

[0092] As a specific example, the product can be a large-diameter pipe used for water pipes, gas pipes, industrial pipelines, etc. The above-mentioned polyethylene resin composition can be used for large-diameter pipes because it has excellent anti-sagging properties, resistance to slow crack growth, and pressure resistance.

[0093] Specific embodiments of this disclosure will be described below. However, the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this disclosure. Furthermore, other details that will be readily understood by those skilled in the art will not be repeated.

[0094] (Preparation of the polyethylene resin composition)

[0095] [Example]

[0096] Example 1

[0097] A first and second reactor connected in series were used to carry out two-stage polymerization through continuous slurry polymerization, using Ziegler-Natta catalyst as catalyst and 1-hexene as comonomer.

[0098] The ethylene copolymer obtained in the first reactor had a melt index (MI) of 21.6 of 0.30 g / 10 min and a density of 0.919 g / cm³. 3 The polymerization rate in the first reactor was 51% by weight, and the copolymer content was 5% by weight.

[0099] The reaction product obtained from the first reactor is fed into the second reactor for further reaction. 100 parts by weight of powdered polyethylene resin obtained from the reaction product in the second reactor are mixed with 0.15 parts by weight of Irganox 1010 and 0.15 parts by weight of Irgafos-168 as antioxidants, 0.15 parts by weight of calcium stearate as a neutralizing agent, and 0.003 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide using a Henschel mixer. The polyethylene resin composition is then pelletized using a twin-screw extruder. At this point, the twin-screw extruder has a screw diameter of 608 mm, an L / D (screw length / screw diameter) of 8, an operating temperature of 240°C, and a speed of 1,090 rpm.

[0100] The prepared polyethylene resin composition had a melt flow index (MI5) of 0.19 g / 10 min and a density of 0.957 g / cm³. 3 The zero-shear viscosity is 29,000,000 poise.

[0101] Example 2

[0102] A first and second reactor connected in series were used to carry out two-stage polymerization through continuous slurry polymerization, using Ziegler-Natta catalyst as catalyst and 1-hexene as comonomer.

[0103] The ethylene copolymer obtained in the first reactor had a melt index (MI) of 21.6 of 0.35 g / 10 min and a density of 0.920 g / cm³. 3 The polymerization rate in the first reactor was 51% by weight, and the copolymer content was 7.5% by weight.

[0104] The reaction product obtained from the first reactor is fed into the second reactor to participate in the reaction. 100 parts by weight of the powdered polyethylene resin obtained from the reaction product of the second reactor are mixed with 0.15 parts by weight of Irganox 1010 and 0.15 parts by weight of Irgafos-168 as antioxidants, 0.15 parts by weight of calcium stearate as a neutralizing agent, and 0.004 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide using a Henschel mixer. The mixture is then extruded into a polyethylene resin composition in pellet form using a twin-screw extruder.

[0105] The polyethylene resin composition has a melt flow index (MI5) of 0.17 g / 10 min and a density of 0.958 g / cm³. 3 The zero-shear viscosity is 32,000,000 poise.

[0106] [Comparative Example]

[0107] Comparative Example 1

[0108] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0109] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 51% by weight and the copolymer content to 5.5% by weight has a melt index MI21.6 of 0.35 g / 10 min and a density of 0.920 g / cm³. 3 The powdered polyethylene resin obtained from the second reactor did not contain any added peroxides. The prepared pellet-type polyethylene resin composition had a melt index (MI5) of 0.20 g / 10 min and a density of 0.958 g / cm³. 3 The zero-shear viscosity is 13,000,000 poise.

[0110] Comparative Example 2

[0111] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0112] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 51% by weight and the copolymer content to 5.8% by weight had a melt index (MI) of 21.6 of 0.35 g / 10 min and a density of 0.920 g / cm³. 3 A pelletized polyethylene resin composition prepared by adding 0.011 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide to 100 parts by weight of powdered polyethylene resin obtained from a second reactor has a melt index (MI5) of 0.15 g / 10 min and a density of 0.958 g / cm³. 3 The zero-shear viscosity is 30,500,000 poise.

[0113] Comparative Example 3

[0114] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0115] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 49% by weight and the copolymer content to 2.8% by weight has a melt index (MI) of 21.6 of 0.51 g / 10 min and a density of 0.925 g / cm³. 3 A pelletized polyethylene resin composition prepared by adding 0.0045 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide to 100 parts by weight of powdered polyethylene resin obtained from a second reactor has a melt index (MI5) of 0.18 g / 10 min and a density of 0.958 g / cm³. 3 The zero-shear viscosity is 22,000,000 poise.

[0116] Comparative Example 4

[0117] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0118] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 50% by weight and the copolymer content to 9.2% by weight had a melt index (MI) of 21.6 of 0.25 g / 10 min and a density of 0.917 g / cm³. 3 A pelletized polyethylene resin composition prepared by adding 0.004 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide to 100 parts by weight of powdered polyethylene resin obtained from a second reactor has a melt index (MI5) of 0.14 g / 10 min and a density of 0.954 g / cm³. 3The zero-shear viscosity is 34,000,000 poise.

[0119] Comparative Example 5

[0120] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0121] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 44% by weight and the copolymer content to 6% by weight had a melt index (MI) of 21.6 of 0.48 g / 10 min and a density of 0.924 g / cm³. 3 A pelletized polyethylene resin composition prepared by adding 0.0045 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide to 100 parts by weight of powdered polyethylene resin obtained from a second reactor has a melt index (MI5) of 0.26 g / 10 min and a density of 0.960 g / cm³. 3 The zero-shear viscosity is 11,000,000 poise.

[0122] Comparative Example 6

[0123] Except for the composition and conditions shown in Table 1 below, the polyethylene resin composition was prepared in the same manner as in Example 1.

[0124] Compared to Example 1, the ethylene copolymer obtained by adjusting the polymerization rate of the ethylene copolymer in the first reactor to 58% by weight and the copolymer content to 5.5% by weight had a melt index (MI) of 21.6 of 0.48 g / 10 min and a density of 0.919 g / cm³. 3 A pelletized polyethylene resin composition prepared by adding 0.002 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a peroxide to 100 parts by weight of powdered polyethylene resin obtained from a second reactor has a melt index (MI5) of 0.17 g / 10 min and a density of 0.955 g / cm³. 3 The zero-shear viscosity is 32,000,000 poise.

[0125] [Table 1]

[0126]

[0127] Test 1: Performance Measurement of Polyethylene Resin Compositions

[0128] The following performance measurements were performed on the polyethylene resin compositions prepared in Examples 1 and 2 and Comparative Examples 1 to 6, and the results are shown in Table 2 below.

[0129] Melt index (MI)

[0130] The melt flow index MI21.6 was measured according to ASTM D1238 at 190°C and a load of 21.6 kg (die inner diameter 2.75 mm).

[0131] The melt flow index MI5 was measured according to ASTM D1238 at 190°C and a 5kg load (die inner diameter of 2.095mm).

[0132] density

[0133] Measured according to ASTM D1505.

[0134] Zero-shear viscosity (η0)

[0135] The storage modulus (G') and loss modulus (G”) were measured using ARES (Advanced Rheometer Extension System, 190°C) based on the shear rate (in rad / sec), and the resulting values ​​were applied to the Carreau model to calculate the zero-shear viscosity (η0).

[0136] dripping time

[0137] A HAAKE Rheomex OS single-screw extruder with a 12mm diameter rod die was used. The processing temperature was 200℃, the extrusion rate was maintained at 38.1 g / min, the initial linear velocity of the extruded resin was 0.546 cm / sec, and the height above the ground was 90.5 cm. The time (drip time, seconds) of the extruded melt product of each polyethylene resin composition to reach the ground was measured.

[0138] melt strength

[0139] When the resin temperature is 200℃ and the chamber temperature is 180℃, the stabilizing force is measured as the resin stretching speed increases.

[0140] Fatigue testing (round bar crack test, CRB)

[0141] Fatigue testing was conducted according to ISO 18489 standard, and the evaluation was carried out within the target stress range of 11.5 MPa to 13.5 MPa. When the stress was 12.5 MPa, the number of cycles was determined by extrapolation.

[0142] Strain hardening modulus (SHM)

[0143] Measurements were taken in accordance with ISO 18488.

[0144] Chabe impact strength

[0145] Measurements were performed at -30°C using samples that met the conditions of ISO 1872-2, in accordance with ISO 179 / 1Ea.

[0146] hydrostatic pressure test

[0147] According to ISO 1167, a pipe with a nominal diameter of 32 mm and SDR11 size is formed using a polyethylene resin composition, and the fracture time is measured at 20°C and a circumferential stress of 12.0 MPa.

[0148] Appearance

[0149] Using a Battenfeld-Cincinnati pipe extruder (uniEX 35-30C), pipes with a nominal diameter of 32 mm (SDR11) or 110 mm (SDR11) were produced from a polyethylene resin composition. The outer and inner surfaces of the produced pipes were visually inspected, and the appearance was evaluated according to the following criteria.

[0150] [Testing Standards]

[0151] ○: Smooth surface, normal

[0152] ×: Rough surface with bumps

[0153] [Table 2]

[0154]

[0155] As can be seen from Table 2 above, Comparative Example 1 is outside the range of the polyethylene resin composition for pipes in this embodiment due to the absence of peroxide. At this point, its zero-shear viscosity is 13,000,000 poise, its dripping time is 128 seconds, and its melt strength is 130 mN. This means that compared to Examples 1 and 2, both the zero-shear viscosity and melt strength are significantly reduced, resulting in very poor anti-sagging properties.

[0156] Since the peroxide content is 0.011 parts by weight, Comparative Example 2 is outside the range of the polyethylene resin composition for pipes in this embodiment. At this time, the dripping time is 205 seconds and the melt strength is 255 mN, which means that the appearance is very poor compared to Examples 1 and 2, and therefore it is not suitable for preparing samples for evaluating physical properties.

[0157] In Comparative Example 3, the ethylene copolymer had a melt flow index (MI) of 21.6 of 0.51 g / 10 min, a comonomer content of 2.8% by weight, and a density of 0.925 g / cm³. 3This exceeds the range of the polyethylene resin composition for pipes according to one embodiment. In this case, it can be seen that the CRB is 120 × 10⁴ cycles, the resistance to slow crack growth is significantly reduced compared to Examples 1 and 2, and the impact strength is also reduced.

[0158] In Comparative Example 4, the ethylene copolymer had a melt flow index (MI21.6) of 0.25 g / 10 min, a comonomer content of 9.2% by weight, and a density of 0.917 g / cm³. 3 The MI5 of the polyethylene resin composition prepared by pelleting was 0.14 g / 10 min, and the density of the polyethylene resin composition prepared by pelleting was 0.954 g / cm³. 3 These values ​​exceed the range of the polyethylene resin composition for pipes according to one embodiment. In this case, the fracture time in the hydrostatic pressure test is 60 hours, which is significantly shorter than that in Examples 1 and 2, and appearance problems also occur.

[0159] In Comparative Example 5, the pellet-type polyethylene resin composition prepared with a polymerization rate of 44% by weight of ethylene copolymer had a density of 0.26 g / 10 min, which exceeded the range of the polyethylene resin composition for pipes according to one embodiment. At this point, the zero-shear viscosity was 11,000,000 poise, the dripping time reduction rate was 22%, the CRB was 115 × 10⁴ cycles, the SHM was 69 MPa, and the resistance to slow crack growth was significantly reduced compared to Examples 1 and 2. Sagging resistance and impact strength were also reduced.

[0160] In Comparative Example 6, the density of the pellet-type polyethylene resin composition prepared with a polymerization rate of 58% by weight of ethylene copolymer was 0.955 g / cm³. 3 This exceeds the scope of the polyethylene resin composition for pipes according to one embodiment. It can be seen that the fracture time in the hydrostatic pressure test is 70 hours, thus the pressure resistance of the pipe is significantly reduced compared to Examples 1 and 2.

[0161] On the other hand, Examples 1 and 2, which use a polyethylene resin composition according to one embodiment, exhibit superior anti-sagging and anti-slow crack growth properties compared to Comparative Examples 1 to 6, while meeting pipe pressure resistance requirements, demonstrating results that meet conventional PE100 requirements.

[0162] As can be clearly seen from the above, the polyethylene resin composition according to this disclosure has both excellent pressure resistance and resistance to slow crack growth (which are contradictory properties), and exhibits high resistance to sag.

[0163] The effects of this disclosure are not limited to those described above, and those skilled in the art will understand other unmentioned technical effects based on the description of the exemplary embodiments above.

[0164] Although embodiments of this disclosure have been disclosed, those skilled in the art will understand that various modifications, additions, and substitutions can be made without departing from the scope and spirit of this disclosure. Therefore, it is evident that the above exemplary embodiments are illustrative in all respects and do not limit this disclosure.

Claims

1. A polyethylene resin composition comprising an ethylene copolymer containing ethylene monomer units and comonomer units, in, Based on the total weight of the ethylene copolymer, the content of comonomer units ranges from 2% to 15% by weight. Based on the total weight of the polyethylene resin composition, the content of the ethylene copolymer is 45% to 57% by weight. Based on 100 parts by weight of a polyethylene resin composition, the peroxide content is 0.001 to 0.01 parts by weight, and The ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190 °C) ranging from 0.26 g / 10 min to 0.50 g / 10 min.

2. The polyethylene resin composition according to claim 1, wherein the comonomer comprises at least one selected from 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicosene.

3. The polyethylene resin composition according to claim 1, wherein the density of the ethylene copolymer is 0.915 g / cm³. 3 Up to 0.935 g / cm 3 .

4. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a zero shear viscosity (η0) of 12,000,000 poise to 50,000,000 poise.

5. The polyethylene resin composition according to claim 1, wherein, The peroxide in the polyethylene resin composition includes at least one selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane-heptane, di-tert-butyl peroxide, tert-butylperoxyisopropylbenzene, 1,1-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-(dibutylperoxy)valerate, diisopropylbenzene peroxide, tert-butyl peroxide, tert-butylperoxybenzoate, and 1,1-bis(tert-butylperoxyisopropyl)benzene.

6. The polyethylene resin composition according to claim 1, wherein the ethylene copolymer has a melt index MI5 (5 kg load, 190 °C) of 0.14 g / 10 min to 0.28 g / 10 min.

7. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a content of 0.956 g / cm³. 3 Up to 0.962 g / cm 3 The density.

8. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a melt strength of 135 mN to 300 mN.

9. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a dripping time of 130 seconds to 200 seconds.

10. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has 1,500,000 or more cycles of CRB (round bar crack test, 12.5 MPa).

11. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a strain hardening modulus of 70 MPa to 90 MPa.

12. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a fracture time of 100 hours or longer at 20°C and 12.0 MPa in a hydrostatic pressure test of a pipeline.

13. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition has a content of 10 kJ / m³. 2 Up to 25kJ / m 2 The impact strength of the cyclohexane (-30℃).

14. The polyethylene resin composition according to claim 1, wherein the polyethylene resin composition is used in the production of pipes.

15. A method for preparing a polyethylene resin composition, comprising: In a plurality of slurry polymerization reactors, including a first reactor and a second reactor connected to each other, a polyethylene resin composition comprising an ethylene copolymer is prepared using ethylene monomers and comonomers in the presence of a catalyst. The polyethylene resin composition is mixed with an additive including peroxide; as well as The mixture of polyethylene resin composition and additives is extruded through an extruder. The content of comonomer units is 2% to 15% by weight, based on the total weight of the ethylene copolymer. Based on the total weight of the polyethylene resin composition, the content of the ethylene copolymer is 45% to 57% by weight. Based on 100 parts by weight of a polyethylene resin composition, the peroxide content is 0.001 to 0.01 parts by weight, and The ethylene copolymer has a melt flow index MI of 21.6 (21.6 kg load, 190 °C) ranging from 0.26 g / 10 min to 0.50 g / 10 min.

16. The method of claim 15, wherein the catalyst is a Ziegler-Natta catalyst.

17. An article prepared from the polyethylene resin composition according to claim 1.

18. The article of claim 17, wherein the article is a pipe.

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