Polyethylene resin composition

Abstract

The present invention provides a polyethylene resin composition exhibiting excellent stretchability and processability, and being highly effective in improving optical properties and rigidity during film manufacturing.

Description

Polyethylene resin composition

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0023563 filed February 24, 2025 and Korean Patent Application No. 10-2026-0033299 filed February 23, 2026, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003] The present invention relates to a polyethylene resin composition that exhibits excellent elongation and processability, and provides excellent improvement in optical properties and rigidity during film manufacturing.

[0004]

[0005] Recently, polyethylene used for food packaging films comes with various requirements.

[0006] First, it must be possible to manufacture low-temperature stretched films due to excellent stretchability. Second, it requires optical properties that allow for the verification of food condition and freshness. Third, it must have excellent printability due to uniform thickness variation. Fourth, it must have excellent heat resistance to facilitate drying after printing. Finally, it must possess excellent mechanical properties.

[0007] In particular, there are few successful commercialization cases of high-density polyethylene (HDPE) due to its inferior optical properties and stretchability. Additionally, because of its high polymer and high crystallinity content, it has the disadvantage of being difficult to print on films due to rough surfaces and large thickness variations during manufacturing.

[0008] To overcome this, methods have been proposed to improve stretchability and transparency by securing low molecular weights while maintaining physical properties derived from high polymers by broadening the crystal and molecular weight distributions of HDPE. However, broadening the molecular weight distribution alone results in unoriented regions under specific stretching conditions, making processing difficult and causing significant variations in film thickness.

[0009] Therefore, to solve the above problem, it is necessary to reduce the crystal size while increasing the low-temperature crystal distribution favorable for elongation.

[0010]

[0011] To solve the problems of the prior art described above, the present invention aims to provide a polyethylene resin composition that exhibits excellent elongation and processability, and provides excellent improvement effects in optical properties and rigidity during film manufacturing.

[0012] Furthermore, the present invention aims to provide a stretched film manufactured using the above-described polyethylene resin composition, which exhibits excellent stretchability, haze characteristics, and high rigidity.

[0013]

[0014] To solve the above problem, according to the present invention, one or more ethylene / alpha-olefin copolymers; and a nucleating agent are included, wherein the density measured according to ISO 1183-2 at 23°C is 0.940 to 0.960 g / cm³ 3 The present invention provides a polyethylene resin composition in which, when measured by CEF (Crystallization Elution Fractionation), the ratio of crystal distribution at 25°C to 70°C based on the total crystal distribution is 15.0 to 21.0%.

[0015] Additionally, according to the present invention, the method comprises: a first step of polymerizing ethylene and an alpha-olefin comonomer through a multimodal slurry polymerization process in the presence of a Ziegler-Natta catalyst and hydrogen to produce an ethylene / alpha-olefin copolymer; and a second step of mixing the ethylene / alpha-olefin copolymer with a nucleating agent and then extruding it.

[0016] A method for manufacturing a polyethylene resin composition is provided, wherein the multimodal slurry polymerization process in the first step comprises: a first process of producing a first copolymer by introducing hydrogen in the presence of a Ziegler-Natta catalyst in a first reactor and performing a primary slurry polymerization reaction between ethylene and an alpha-olefin comonomer; and a second process of producing an ethylene / alpha-olefin copolymer by transferring the first copolymer to a second reactor connected to the first reactor, introducing ethylene, and performing a secondary slurry polymerization reaction in the presence of a Ziegler-Natta catalyst.

[0017] In addition, according to the present invention, a stretched film comprising the polyethylene resin composition is provided.

[0018]

[0019] The polyethylene resin composition according to the present invention has excellent stretchability and processability. Furthermore, the polyethylene resin composition can form a film having a uniform thickness, and in particular, it is possible to manufacture a biaxially stretched film having excellent optical properties and high rigidity. As a result, it is particularly useful for food packaging films.

[0020]

[0021] In the present invention, terms such as first, second, etc. are used to describe various components, and these terms are used solely for the purpose of distinguishing one component from another.

[0022] Furthermore, the terms used herein are used merely to describe exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0023] Also, throughout this specification, the terms "polyethylene" or "ethylene (co)polymer" include both ethylene homopolymers and / or copolymers of ethylene and alpha-olefins.

[0024] Unless otherwise defined in this specification, "copolymer" may mean block copolymer, random copolymer, graft copolymer, or alternating copolymer, and "copolymer" may mean block copolymer, random copolymer, graft copolymer, or alternating copolymer.

[0025] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0026] The polyethylene resin composition of the present invention will be described in detail below.

[0027]

[0028] The polyethylene resin composition according to the present invention is,

[0029] One or more ethylene / alpha-olefin copolymers; and

[0030] It includes a nucleating agent,

[0031] Density of 0.940 to 0.960 g / cm³ measured according to ISO 1183-2 at 23℃ 3 And,

[0032] When measured by the Crystallization Elution Fractionation (CEF) method, the ratio of the crystal distribution at 25°C to 70°C based on the total crystal distribution is 15.0 to 21.0%.

[0033] In the present invention, the polyethylene resin composition produced by reducing the crystal size related to stretching and simultaneously suppressing crystal growth for high-density polyethylene copolymerized with one or more alpha-olefin comonomers such as butene exhibits excellent optical and surface properties, and it was confirmed that the coefficient of friction (COF) is improved and thickness variation is reduced, making it easy to print, particularly a biaxially oriented polyethylene (BOPE) film, can be produced using the polyethylene resin composition, thereby completing the present invention.

[0034] Specifically, the polyethylene resin composition according to the present invention has a crystal distribution ratio of 15.0 to 21.0% at 25°C to 70°C based on the total crystal distribution when measured by CEF.

[0035] When measuring CEF, crystals distributed within the temperature range of 25°C to 70°C affect the stretchability of the film. In particular, when a polyethylene mold is manufactured for biaxial stretching, it undergoes a process of first stretching in the MD (Machine Direction, longitudinal direction) followed by stretching in the TD (Transverse Direction, transverse direction). During this process, the crystals mainly oriented during the first MD stretching (5x or less) consist of crystals in the high-crystallinity (90°C or higher) region, which are widely distributed in high-density polyethylene, and become a factor determining mechanical properties such as the film's stiffness. Subsequently, when the second TD stretching (8x to 10x) is performed, the crystals are mainly oriented in the medium-crystallinity (70°C or higher and 90°C or lower) and low-crystallinity (25°C to 70°C) regions, excluding the high-crystallinity region oriented in the first stage, creating a web-like structure within the biaxially stretched film. At this time, if the crystal distribution in the relevant region is insufficient, TD stretching is difficult, and in particular, since high-density polyethylene has a very low degree of crystallinity in the low-crystallinity region, film breakage is likely to occur during TD stretching. The polyethylene resin composition according to the present invention can exhibit excellent stretchability as a large amount of crystals exist in the above temperature range. More specifically, when measured by CEF, the polyethylene resin composition may have a crystal distribution ratio of 15.0% or more, or 18.0% or more, or 18.5% or more, or 18.9% or more based on the total crystal distribution, and 21.0% or less, or 20.8% or less, or 20.6% or less, or 20.5% or less, or 20.0% or less, or 19.8% or less.

[0036] Meanwhile, in the present invention, the ratio of the crystal distribution at 25°C to 70°C is calculated as a percentage based on the total peak area in a CEF analysis graph derived through CEF analysis, where the elution temperature (Te) (°C) is on the x-axis and the elution amount (dw / dt) is on the y-axis. At this time, the peak area is obtained through integration. Also, the total peak area corresponds to the total crystal distribution, and the peak area at 25°C to 70°C corresponds to the ratio of the crystal distribution at 25°C to 70°C.

[0037] In addition, the specific method and analysis conditions for CEF analysis in the present invention are as described in the experimental examples below.

[0038] In addition, the polyethylene resin composition exhibits high density along with the crystal characteristics described above. Specifically, the polyethylene resin composition has a density of 0.940 to 0.960 g / cm³ as measured according to ISO 1183-2 at 23°C.

[0039] The density of the polyethylene resin composition affects the stiffness of the stretched film. The density of the polyethylene resin composition is 0.940 g / cm³ 3 If it is less than, there is a risk that the stiffness of the stretched film will decrease, and 0.960 g / cm² 3 If it exceeds [value], the stretchability of the film may be reduced due to the excessively high density. Since the polyethylene resin composition according to the present invention has a density within the above-mentioned range, it exhibits excellent stretchability during film manufacturing and can also improve the stiffness of the manufactured film. More specifically, the polyethylene resin composition has a density of 0.940 g / cm³ 3 Above, or 0.942 g / cm³ 3 Above, or 0.944 g / cm³ 3 Above, or 0.945 g / cm³ 3 That is all, 0.960 g / cm³ 3 Less than or equal to 0.955 g / cm³ 3Less than, or 0.950 g / cm³ 3 Less than or equal to 0.949 g / cm³ 3 It may be less than.

[0040] In addition, the polyethylene resin composition has a high density as described above, along with a melt index (MI) of 0.6 to 1.5 g / 10 min. 2.16 It represents ).

[0041] The melt index of polyethylene resin compositions affects film processability and dimensional stability during the manufacture of stretched films. MI 2.16 If this is less than 0.6 g / 10 min, the processing pressure increases, raising concerns about reduced processability; if it exceeds 1.5 g / 10 min, the high fluidity may cause a neck-in phenomenon, leading to variations in film thickness. More specifically, the MI of the above polyethylene resin composition 2.16 It may be 0.6 g / 10min or more, or 0.8 g / 10min or more, or 0.9 g / 10min or more, and 1.5 g / 10min or less, or 1.4 g / 10min or less, or 1.3 g / 10min or less.

[0042] In addition, the polyethylene resin composition has a processing temperature range (or processing temperature region) of 13°C or more, defined by the difference between the melting temperature (Tm) and the crystallization temperature (Tc) (Tm-Tc).

[0043] The above processing temperature range refers to a temperature range in which processing is possible when manufacturing films, etc. using a polyethylene resin composition, and the wider the processing temperature range, the better the processability. Since the polyethylene resin composition according to the present invention has a high processing temperature range of 13°C or higher, it exhibits excellent processability that allows processing over a wide temperature range.

[0044] More specifically, the processing temperature range of the polyethylene resin composition is 13°C or higher, or 14°C or higher, or 15°C or higher. Since a higher processing temperature range is preferable, the upper limit is not specifically limited, but considering the limitations of the manufacturing process, it may be 30°C or lower, or 25°C or lower, or 20°C or lower, or 17°C or lower.

[0045] Meanwhile, the high processing temperature range as described above is due to the high Tm resulting from the high molecular weight content. Specifically, the polyethylene resin composition has a melting temperature (Tm) of 120 to 150°C. More specifically, the melting temperature may be 120°C or higher, or 125°C or higher, and 150°C or lower, or 140°C or lower, or 135°C or lower.

[0046] In addition, the polyethylene resin composition has a crystallization temperature (Tc) of 125°C or lower. More specifically, the crystallization temperature may be 125°C or lower, or 120°C or lower, or 117°C or lower, or 110°C or higher, or 112°C or higher, or 114°C or higher.

[0047] As described above, having a high melting temperature and a low crystallization temperature allows for a wider processing temperature range, thereby exhibiting excellent processability.

[0048] Meanwhile, in the present invention, the crystallization temperature (Tc) and melting temperature (Tm) of the polyethylene resin composition can be measured using a Differential Scanning Calorimeter (DSC, device name: DSC 2920, manufacturer: TA instrument). Specifically, the temperature is raised to heat the polyethylene resin composition to 200 ℃ and then maintained at that temperature for 5 minutes (1 st(RUN thermal history removal), then lower to -50℃, and increase the temperature again to define the melting temperature (Tm) as the highest point of the endothermic peak corresponding to the peak of the DSC curve, and define the crystallization temperature (Tc) as the highest point of the exothermic peak corresponding to the peak of the DSC curve appearing while decreasing the temperature again. At this time, the rate of temperature increase and decrease is 10 ℃ / min, and the melting temperature (Tm) and crystallization temperature (Tc) are in the second temperature increase and decrease section (2 nd This is the result of measurements taken in RUN.

[0049] In addition, the polyethylene resin composition according to the present invention has a melt strength (Melt Strength, F) at 170°C. b ) is 70 mN or more, more specifically 75 mN or more, and 100 mN or less, or 90 mN or less, or 85 mN or less, or 82 mN or less.

[0050] A higher melt strength implies superior processability. The polyethylene resin composition according to the present invention exhibits high melt strength compared to conventional materials, and from this, it can be seen that it possesses superior processability.

[0051] Meanwhile, in the present invention, the melt strength of the polyethylene resin composition can be measured at 200°C using a capillary rheometer. Specifically, the polyethylene resin composition is discharged through a capillary die (flat die, 180-degree angle) having a length (Lo / Do) ratio to diameter (Do) of 6.25. After equilibrating at 200°C for 5 minutes, it is discharged at a constant extrusion speed of 22 g / min. At this time, the capillary shear rate is 200 / s, the rheotens start rate is 50 mm / s, and the standard test temperature is 200°C. The sample is 1.2 cm / sec 2The single-axis is pulled by a set of acceleration nips located 80 mm below the die with acceleration. Tension is recorded as a function of the pulling speed of the nip rolls. Melt strength is defined as the Plato force (mN) before the strand breaks. Specific measurement methods and conditions are as described in the test examples below.

[0052] In addition, the polyethylene resin composition exhibits a high degree of crystallinity of 60% or more.

[0053] More specifically, the degree of crystallization of the polyethylene resin composition may be 60% or more, or 63% or more, or 65% or more, or 67% or more, or 68% or more. The upper limit of the degree of crystallization is not specifically limited, but for example, it may be 80% or less, or 75% or less, or 70% or less. As such, when a film is manufactured using the polyethylene resin composition, a dense crystal structure is formed due to the high degree of crystallization, and the transparency of the film can be improved.

[0054] Meanwhile, the crystallinity of the above polyethylene resin composition can be measured using a Differential Scanning Calorimeter (DSC) in accordance with ASTM F2625. Specifically, the polyethylene resin composition is dried at 140°C under a pressure of 10 mmHg for 12 hours, then a 5 mg sample is placed in an aluminum pan for liquids. Using a differential scanning calorimeter, the temperature is increased from 25°C to 200°C at a rate of 10°C / min, maintained at 200°C for 5 minutes, and then cooled to -50°C at a rate of 10°C / min. This heating and cooling cycle is repeated twice. For the heating curve appearing during the second cycle, a new baseline is established to ensure a smooth connection between the onset and end of the endothermic peak and the temperatures before and after melting. The melting peak, which is the highest endothermic peak, is then determined by integrating the area of ​​the melting peak to obtain the heat of fusion (ΔH) of the polyethylene resin composition.f ) is calculated. Based on the heat of fusion of a polyethylene resin composition having a degree of crystallization of 100%, the degree of crystallization of each resin composition is calculated according to the following mathematical formula 1.

[0055] [Mathematical Formula 1]

[0056] Degree of crystallization (%) = (△H f / △H0) X 100

[0057] Here, △H f ε is the heat of fusion (J / g) of the polyethylene resin composition, and ΔH0 is the heat of fusion (J / g) of the polyethylene resin composition having 100% crystallinity, using the heat of fusion value of 293.4 J / g for 100% crystalline polyethylene (Reference: “Using DSC to Measure the Degree of Crystallinity in Polyethylene Waste Bags”, ebatco). The method and conditions for measuring the degree of crystallinity of the polyethylene resin composition are as described in the experimental examples below.

[0058] In addition, the polyethylene resin composition has a molecular weight distribution (MWD) of 8.0 to 12.0.

[0059] Specifically, since the polyethylene resin composition has a molecular weight distribution within the range described above, it can exhibit the effect of improving processability and stretchability when manufacturing a stretched film. If the molecular weight distribution is narrow to less than 8.0, the melting point (Tm) and crystallization temperature (Tc) are lowered, which reduces processing stability, and the processing window (Tm-Tc) used for processing is reduced, which may lead to a decrease in processability. On the other hand, if the molecular weight distribution exceeds 12.0, the content of ultra-high molecular weight that is difficult to stretch increases, and the content of low molecular weight and wax increases, which may lead to a decrease in film appearance and stretchability. More specifically, the polyethylene resin composition may have a molecular weight distribution of 8.0 or higher, or 8.5 or higher, or 9.0 or higher, or 9.5 or higher, and 12.0 or lower, or 11.5 or lower, or 11.0 or lower, or 10.5 or lower.

[0060] In the present invention, the molecular weight distribution of the polyethylene resin composition can be determined by measuring the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polyethylene using gel permeation chromatography (GPC), and calculating the molecular weight distribution (Mw / Mn, polydispersity index) by dividing the weight-average molecular weight by the number-average molecular weight. Specific measurement methods and conditions are as described in the test examples below.

[0061] The above-described polyethylene resin composition comprises one or more ethylene / alpha-olefin copolymers and a nucleating agent.

[0062] The above ethylene / alpha-olefin copolymer may, specifically, be a copolymer of ethylene and one or more C4 to C10 alpha-olefin comonomers.

[0063] In addition, the above alpha-olefin monomer may specifically be 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-eicocene, etc.

[0064] In addition, the ethylene / alpha-olefin copolymer may contain an alpha-olefin comonomer-derived structure in an amount of 0.5 to 1.6 weight% based on the total weight of the ethylene / alpha-olefin copolymer. As the ethylene / alpha-olefin copolymer contains a comonomer-derived structural unit within the above-mentioned content range, when the film is biaxially stretched in the TD direction after stretching in the MD direction, the content of low molecular weight and low crystal distribution involved in microfibril formation is high, which is advantageous for stretching, and it can exhibit superior biaxial stretchability compared to conventional polyethylene resin compositions. More specifically, the ethylene / alpha-olefin copolymer may contain an alpha-olefin comonomer-derived structure in an amount of 0.5% by weight or more, 0.8% by weight or more, 1.0% by weight or more, or 1.1% by weight or more, and 1.6% by weight or less, or 1.5% by weight or less, or 1.4% by weight or less, or 1.3% by weight or less, or 1.2% by weight or less, based on the total weight of the copolymer.

[0065] Specifically, the ethylene / alpha-olefin copolymer may be an ethylene / 1-butene copolymer, and more specifically, it may be an ethylene / 1-butene copolymer containing a 1-butene-derived structure in an amount of 0.5% by weight or more, 0.8% by weight or more, 1.0% by weight or more, or 1.1% by weight or more, and 1.6% by weight or less, or 1.5% by weight or less, or 1.4% by weight or less, or 1.3% by weight or less, or 1.2% by weight or less, based on the total weight of the ethylene / 1-butene copolymer.

[0066] Meanwhile, in the present invention, the content of structures derived from alpha-olefin comonomers within the ethylene / alpha-olefin copolymer can be calculated through 1H NMR analysis. Specific analysis and content calculation methods are as described in the experimental examples below.

[0067] In addition, the ethylene / alpha-olefin copolymer may satisfy one or more or both of the following conditions (b1) and (b2):

[0068] (b1) Density of 0.940 to 0.960 g / cm³ when measured by the ISO 1183-2 method at 23℃,

[0069] (b2) Melt index (MI) measured according to the ISO 1133 method under a load of 2.16 kg at 190°C 2.16 ) 0.5 to 5.0g / 10min

[0070] Specifically, the ethylene / alpha-olefin copolymer may have a density of 0.940 to 0.960 g / cm³ when measured by the ISO 1183-2 method at 23°C.

[0071] The density of the above ethylene / alpha-olefin copolymer affects the stiffness of the stretched film. The density of the ethylene / alpha-olefin copolymer is 0.940 g / cm³ 3 If it is less than, there is a risk that the stiffness of the stretched film will decrease, and 0.960 g / cm² 3 If it exceeds, the stretchability of the film may be reduced due to the excessively high density. More specifically, the density of the ethylene / alpha-olefin copolymer is 0.940 g / cm³ 3 Above, or 0.945 g / cm³ 3 Above, or 0.946 g / cm³ 3 Above, or 0.946 g / cm³ 3 That is all, 0.960 g / cm³ 3 Less than or equal to 0.955 g / cm³ 3 Less than, or 0.950 g / cm³ 3 It may be less than.

[0072] In addition, the melt index (MI) of the above ethylene / alpha-olefin copolymer when measured according to the ISO 1133 method under a load of 2.16 kg at 190°C 2.16 ) may be 0.5 to 5.0 g / 10 min. The melt index of polyethylene affects the processability and dimensional stability of the resin composition. MI 2.16 If this is less than 0.5 g / 10 min, there is a risk that processing performance will be reduced due to increased processing pressure, and if it exceeds 5.0 g / 10 min, a neck-in phenomenon may occur due to high fluidity, which may result in variations in film thickness.

[0073] Typically, the melt index can be controlled by adjusting the type of catalyst and the amount of hydrogen input during the polymerization process, and the amount of hydrogen input is determined by the hydrogen reactivity of the catalyst used. In the present invention, by using a transition metal compound having low hydrogen reactivity, the melt index of the polyethylene produced is reduced, and as a result, viscosity in the processing range is increased, thereby improving dimensional stability. More specifically, MI 2.16 This may be 0.5 g / 10min or more, or 0.7 g / 10min or more, or 0.8 g / 10min or more, and 5.0 g / 10min or less, or 3.0 g / 10min or less, or 2.0 g / 10min or less, or 1.5 g / 10min or less, or 1.2 g / 10min or less. Thus, along with high density, the MI within the above-mentioned range 2.16 By having [this], excellent film stretchability and processability can be exhibited.

[0074] In addition, in the polyethylene resin composition according to the present invention, the nucleating agent reduces the size of crystals related to elongation within the polyethylene resin composition.

[0075] Specifically, the nucleating agent acts as a nucleation site when the ethylene / alpha-olefin copolymer reaches the crystallization temperature through a gradual decrease in temperature from a temperature above the melting temperature, thereby making the size of the polymer crystal denser and increasing the degree of crystallization.

[0076] As the above nucleating agent, organic nucleating agents, inorganic nucleating agents, or mixtures thereof may be used.

[0077] In addition, the above organic nucleating agent may specifically include metal carboxylate salts, metal phosphate salts, dibenzylidene sorbitol, etc., and any one or more of these may be used as a mixture.

[0078] More specifically, the nucleating agent may be a metal carboxylic acid salt, a metal phosphate salt, an inorganic nucleating agent, or a mixture thereof.

[0079] Specifically, the metal carboxylic acid salt may include a metal element selected from the group consisting of alkali metals of Group 1, alkaline earth metals of Group 2, and transition metals of Group 12 in the periodic table. Among these, since the alkaline earth metals of Group 2 and the transition metals of Group 12 exist in the form of divalent cations, they separate into two fatty acid forms at temperatures above the melting point of the ethylene / alpha-olefin copolymer, and can bond with the fatty acid or polymer at temperatures below the melting point of the ethylene / alpha-olefin copolymer. When bonded to the crystallized polymer ends, they form a crystal structure with uniform inter-crystal distances and prevent the formation of superpolymers, thereby improving the haze characteristics, which are the transparency of the film. Additionally, when kneaded with the ethylene / alpha-olefin copolymer, the melt viscosity of the resin composition is lowered to improve flowability, and as a result, moldability can be improved. More specifically, the metal may be Mg, Ca, Sr, Ba, Cd, or Zn, and more specifically, may be Ca, Mg, or Zn.

[0080] Specific examples of the metal carboxylate salts mentioned above include calcium cis-1,2-cyclohexanedicarboxylate, calcium bicycle[2,2,1]heptane-2,3-dicarboxylate, sodium benzoate, 4-tert-aluminum butylbenzoate, sodium adipose, or sodium bicyclo[2.2.1]heptane-2,3-dicarboxylate, and the like, and any one or more of these may be used. In addition, commercially available products such as HPN-20E™ (Milliken) may be used.

[0081] In addition, the metal phosphate salt may contain a metal element selected from the group consisting of alkali metals of Group 1 or metals of Group 13 in the periodic table. More specifically, the metal in the metal phosphate salt may be Na or Al.

[0082] Specific examples of the metal salts of the above phosphoric acid include mono-, bis-, or tetra-phenyl compounds such as sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl)phosphate (CAS No. 85209-91-2) and hydroxybis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1.3,2)dioxaphosphocin 6-oxidato) aluminum (CAS No. 151841-65-5). Phosphates may be used, and any one or more of these may be used. Additionally, commercially available products such as ADK STAB NA-11™ (Adeka) and ADK STAB NA-21™ (Adeka) may be used.

[0083] In addition, the above-mentioned inorganic nucleating agent may include talc, calcium oxide, or mica, and any one or more of these may be used.

[0084] More specifically, the nucleating agent may comprise calcium cis-hexahydrodicarboxylate, calcium bicyclo[2.2.1]heptane-2,3-dicarboxylate, sodium benzoate, 4-tert-butylbenzoate aluminum, sodium adipose, bicyclo[2.2.1]heptane-2,3-dicarboxylate sodium, sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl)phosphate, hydroxybis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1.3.2)-dioxaphosphosine 6-oxidato) aluminum, talc, calcium oxide, mica, or a mixture thereof.

[0085] The nucleating agent may be included in an amount of 300 to 3,000 ppm based on the total weight of the ethylene / alpha-olefin copolymer. More specifically, if the content of the nucleating agent in the polyethylene resin composition is less than 300 ppm based on the total weight of the ethylene / alpha-olefin copolymer, the effect of improving crystallinity and crystal orientation uniformity is negligible, and if it exceeds 3,000 ppm, metal cations may leach out, thereby reducing the smoothness of the film surface or become a source of contamination, thereby reducing transparency. More specifically, the nucleating agent may be included in an amount of 300 ppm or more, or 400 ppm or more, or 500 ppm or more, and 3,000 ppm or less, or 2,500 ppm or less, or 2,000 ppm or less.

[0086] Meanwhile, the polyethylene resin composition according to the present invention as described above can be produced by multimodal slurry polymerization using a plurality of reactors.

[0087] In the present invention, multimodal slurry polymerization means producing polymers with two or more different physical or chemical properties, such as particle size and molecular weight, by continuously performing a polymerization reaction in multiple stages using a plurality of reactors. At this time, the polymerization conditions in each reactor, such as the type and amount of monomer, catalyst, additive, polymerization temperature, and polymerization time, may be the same or different.

[0088] For example, when a two-stage continuous polymerization reaction is carried out using two reactors, it is called bimodal slurry polymerization.

[0089] Specifically, the polyethylene resin composition according to the present invention is,

[0090] A first step of producing an ethylene / alpha-olefin copolymer by polymerizing ethylene and alpha-olefin comonomers through a multimodal slurry polymerization process in the presence of a Ziegler-Natta catalyst and hydrogen;

[0091] A second step of mixing the above ethylene / alpha-olefin copolymer with a nucleating agent and then extruding; comprising

[0092] The multimodal slurry polymerization process in the first step above may be carried out by: a first process of producing a first copolymer by introducing hydrogen in a first reactor in the presence of a Ziegler-Natta catalyst and performing a primary slurry polymerization reaction between ethylene and an alpha-olefin comonomer; and a second process of producing an ethylene / alpha-olefin copolymer by transferring the first copolymer to a second reactor connected to the first reactor, introducing ethylene, and performing a secondary slurry polymerization reaction in the presence of a Ziegler-Natta catalyst.

[0093] As the method for manufacturing the above polyethylene resin composition is carried out by a multimodal slurry polymerization reaction using a plurality of reactors, two or more reactors, for example, two or more continuous stirred tank reactors (CSTRs), may be used.

[0094] Specifically, in the multimodal slurry polymerization process of the first step of the above manufacturing method, a first reactor in which a first slurry polymerization reaction for the production of a first copolymer takes place, and a second reactor connected to the first reactor in which a second slurry polymerization reaction takes place between the first copolymer transferred from the first reactor and ethylene introduced into the second reactor may be used.

[0095] In addition, the polymerization process in the first and second reactors is carried out by a slurry polymerization process.

[0096] In the case of solution polymerization, since the catalyst is activated by high temperature and high pressure reactions, the resin composition produced exhibits degraded stretchability due to a narrow molecular weight distribution (MWD) and a low high molecular weight tail content. However, in the case of the slurry polymerization process of the present invention, since polymerization is performed at a relatively low temperature, it is possible to secure a molecular structure with a wide MWD and a large amount of high molecular weight tail, which is required for polyethylene resin compositions for manufacturing transparent films. As a result, excellent biaxial stretchability can be exhibited, and high transparency can be achieved by selectively enhancing the low molecular weight and low crystallization distribution through the securing of comonomers.

[0097] In addition, in the manufacturing method according to the present invention, the comonomer may be a C4 to C10 alpha-olefin. The alpha-olefin monomer is as previously defined.

[0098] In addition, the total input amount of the alpha-olefin comonomer is 0.005 to 1.50 weight% based on the total weight of the monomers, including ethylene and the alpha-olefin comonomer, input into the first and second reactors. If the total input amount of the comonomer is less than 0.005 weight% based on the total weight of the monomers, the content of low molecular weight structures in the finally produced copolymer is low, making it difficult to achieve a sufficient effect. Furthermore, if it exceeds 1.50 weight% and is excessively high, it is undesirable for production via a slurry polymerization process due to process instability factors such as fouling, and also the density is 0.940 g / cm³ 3It is difficult to achieve the above. In addition, the polyethylene resin composition being manufactured has a low polymer and high crystal content, which reduces the MD direction stretching ratio and raises concerns that the mechanical properties of the resulting film may deteriorate. More specifically, the total input amount of the alpha-olefin comonomer may be 0.005 wt% or more, or 0.05 wt% or more, or 0.50 wt% or more, or 0.80 wt% or more, or 1.00 wt% or more, or 1.10 wt% or more, or 1.14 wt% or more, or 1.20 wt% or more, based on the total weight of the monomer including ethylene and the alpha-olefin comonomer, or 1.50 wt% or less, or 1.40 wt% or less, or 1.38 wt% or less, or 1.35 wt% or less, or 1.30 wt% or less.

[0099] Furthermore, in the manufacturing method according to the present invention, the Ziegler-Natta catalyst used in the first and second processes of the first step may be the same or different. When the same Ziegler-Natta catalyst is used in the first and second processes, it is easier to control the physical properties of the polyethylene resin composition being manufactured and to realize the corresponding physical property conditions.

[0100] In addition, in the manufacturing method according to the present invention, the polymerization temperature (T1) and pressure (P1) during the primary slurry polymerization reaction in the first process are higher than the polymerization temperature (T2) and pressure (P2) during the second slurry polymerization reaction. By controlling the amount of comonomer input as described above and making the temperature and pressure conditions during the primary slurry polymerization reaction higher, a polyethylene resin composition having the crystal distribution and physical properties described above can be more easily realized.

[0101] Specifically, the difference (T1-T2) between the polymerization temperature (T1) during the first slurry polymerization reaction and the polymerization temperature (T2) during the second slurry polymerization reaction may be 3°C or more, or 4°C or more, or 4.5°C or more, or 5°C or more, and 6°C or less, or 5.8°C or less, or 5.5°C or less.

[0102] In addition, the difference (P1-P2) between the pressure (P1) during the first slurry polymerization reaction and the pressure (P2) during the second slurry polymerization reaction may be 3 bar or more, or 3.5 bar or more, or 4 bar or more, and 6 bar or less, or 5.5 bar or less, or 5 bar or less.

[0103] In addition, while satisfying the above-mentioned temperature difference and pressure difference, in the manufacturing method according to the present invention, the polymerization temperature (T1) during the first slurry polymerization reaction may be 70 to 90°C, and the polymerization temperature (T2) during the second slurry polymerization reaction may be 70 to 90°C.

[0104] In addition, the pressure (P1) during the first slurry polymerization reaction may be 5 to 10 bar, and the pressure (P2) during the second slurry polymerization reaction may be 1 to 5 bar.

[0105] Each step is explained in detail below.

[0106] In the method for manufacturing a polyethylene resin composition according to the present invention, the first step is to polymerize ethylene and an alpha-olefin comonomer through a multimodal slurry polymerization process in the presence of a Ziegler-Natta catalyst and hydrogen to produce an ethylene / alpha-olefin copolymer.

[0107] The multimodal slurry polymerization process in the first step above specifically comprises: a first process for producing a first copolymer by introducing hydrogen in the presence of a Ziegler-Natta catalyst in a first reactor and performing a primary slurry polymerization reaction between ethylene and an alpha-olefin comonomer; and a second process for producing an ethylene / alpha-olefin copolymer by transferring the first copolymer to a second reactor connected to the first reactor, introducing ethylene, and performing a secondary slurry polymerization reaction in the presence of a Ziegler-Natta catalyst.

[0108] The Ziegler-Natta catalyst used in the production of the above ethylene / alpha-olefin copolymer may specifically be a magnesium-supported titanium catalyst. In addition, the magnesium-supported titanium catalyst may further include a halogenated hydrocarbon.

[0109] Specifically, the magnesium-supported titanium catalyst comprises a solid magnesium support. Examples of the magnesium support include magnesium, magnesium oxide, magnesium chloride, or silica-magnesia, and any one or more of these may be used. Among these, considering the catalytic activity and the ease of achieving optimal physical property conditions of the polyethylene resin composition, the magnesium support may be magnesium or magnesium chloride.

[0110] Meanwhile, the magnesium-supported titanium catalyst comprises a titanium-containing compound represented by the following chemical formula 1 as a main catalyst:

[0111] [Chemical Formula 1]

[0112] Ti(OR 1 ) m X 1 4-m

[0113] In the above chemical formula 1,

[0114] R 1 is the same or different, and is an alkyl group having 1 to 10 carbon atoms, and

[0115] X 1 is a halogen element, more specifically Cl, Br, or I, and

[0116] m is an integer from 0 to 4.

[0117] In the above chemical formula 1, R 1 Specifically, it may be an alkyl group having 1 or more carbon atoms, or 2 or more, or 3 or more carbon atoms, or 10 or fewer, or 8 or fewer, or 5 or fewer carbon atoms.

[0118] Also, X 1It can specifically be Br or Cl, and more specifically, it can be Cl.

[0119] Specific examples of the above titanium-containing compounds include titanium tetrachloride (TiCl4) or titanium chlorinated oxide, and either one or a mixture of both of these may be used.

[0120] In addition, the catalyst containing the titanium-containing compound may include Mg:Ti in a molar ratio of 1:1 to 10:1, or 2:1 to 7:1, or 4:1 to 5:1, based on the content of Mg in the magnesium support and the content of Ti in the titanium-containing compound. Superior catalytic activity may be exhibited when included within the above molar ratio range.

[0121] In addition, the shape of the catalyst is not particularly limited, but, for example, may be in the form of spherical fine particles.

[0122] In addition, the average particle size of the catalyst may be 5 to 100 μm, and more specifically, 5 μm or more, or 8 μm or more, and 100 μm or less, or 50 μm or less, or 20 μm or less, or 13 μm or less.

[0123] Meanwhile, in the present invention, the average particle size of the catalyst can be measured through scanning electron microscopy (SEM) observation. Specifically, after obtaining an SEM image in which 100 or more catalyst particles are observed, a random straight line is plotted, and the average size of the catalyst particles can be calculated through the length of the straight line, the number of particles included in the straight line, and the magnification.

[0124] In addition, the magnesium-supported titanium catalyst may further include halogenated hydrocarbons.

[0125] Halogenated hydrocarbons coordinate around titanium, which acts as an active site, thereby altering the electrical properties of titanium. Additionally, due to the large volume of the halogenated hydrocarbons, sufficient steric space is formed between titanium atoms, which can significantly enhance catalytic activity during polyethylene polymerization.

[0126] The above halogenated hydrocarbon may specifically be an alkane having 1 to 12 carbon atoms, a cycloalkane having 3 to 12 carbon atoms, an alkene having 2 to 12 carbon atoms, an alkyne having 2 to 12 carbon atoms, or an aromatic hydrocarbon having 6 to 30 carbon atoms, substituted with one or more halogen groups, and the halogen group may be a fluoro, chloro, or bromo.

[0127] Specific examples include bromoform, tetrachloroethane, hexachloroethane, pentachloroethane, 1,1,2,2-tetrachloroethane, 1-bromo-1-chloroethane, 1,2-dibromoethane, 1,2-dichloroethane, bromoethane, hexachloropropane, 1,2,3-trichloropropane, 1,2-dichloropropane, 1-chloropropane, 2-chloropropane, chlorobutane, dichlorobutane, 1-chloro-2-methylpropane, n-butyl chloride, tert-butyl chloride, 1-chloro-3-methylbutane, 1-chloropentane, 1,5-dichloropentane, bromopentane, neopentyl chloride, 1-chloroheptane, cyclopropyl bromide, cyclobutyl chloride, Examples include cyclohexyl chloride, cyclohexyl bromide, vinylidene chloride, 1,2,3,3-tetrachloropropene, 1,2-dibromo-1-propene, 1,3-dichloropropene, hexachloro-1,3-butadiene, 2-bromo-2-butene, propagyl chloride, chlorobenzene, tetrachlorobenzene, trichlorobenzene, dichlorobenzene, 4-chlorobenzyl chloride, benzyl chloride, or 1,1-dichloro-2-phenylcyclopropane, and any one or a mixture of two or more of these may be used.

[0128] The above halogenated hydrocarbon may be included in an amount of 0.1 mole or more, or 0.12 mole or more, or 0.13 mole or more, and 500 mole or less, or 100 mole or less, or 50 mole or less, or 10 mole or less, or 1 mole or less, or 0.5 mole or less, based on 1 mole of the titanium-containing compound which is the main catalyst.

[0129] The above-described Ziegler-Natta catalyst may be manufactured by a manufacturing method comprising: a support treatment step of mixing a raw material of a magnesium support with an alcohol and reacting it; and a titanium-containing compound supporting step of reacting the product obtained as a result of the above step with a titanium-containing compound represented by Formula 1, and further comprising a step of contacting and reacting a halogenated hydrocarbon during the support treatment step and the titanium-containing compound supporting step, or after the titanium-containing compound supporting step. Accordingly, the method for manufacturing a polyethylene resin composition according to the present invention may include, prior to the first step, a step for manufacturing the Ziegler-Natta catalyst, specifically the support treatment step and the titanium-containing compound supporting step, and may further comprise a step of contacting and reacting a halogenated hydrocarbon during the support treatment step and the titanium-containing compound supporting step, or after the titanium-containing compound supporting step.

[0130] Specifically, the support treatment step for manufacturing the Ziegler-Natta catalyst can be performed by mixing and reacting the raw material of the magnesium support with an alcohol under a non-polar solvent.

[0131] Specific examples of the above alcohols include methanol, ethanol, 1-propanol, isopropanol, n-butanol, isobutanol, 1-pentanol, isopentanol, n-hexanol, 1-octanol, 2-ethyl-1-hexanol, etc., and any one or more of these may be used. Among these, ethanol or 2-ethyl-1-hexanol may be used.

[0132] The above alcohol may be used in an amount of 1.0 mole or more, or 1.5 mole or more, or 2.0 mole or more, and 10.0 mole or less, or 8.0 mole or less, or 6.0 mole or less, per 1 mole of raw material of the magnesium support.

[0133] Meanwhile, the raw materials for the magnesium support may include the magnesium support itself, such as magnesium, magnesium oxide, magnesium chloride, or silica-magnesia; or magnesium alcoholates such as magnesium ethylate, and any one or more of these may be used. For example, when magnesium alcoholate is used as a raw material for the magnesium support, it is converted into magnesium chloride by titanium tetrachloride (TiCl4) introduced as a main catalyst and is included as a support in the final catalyst produced.

[0134] The method of mixing the raw material of the magnesium support and the alcohol can be specifically performed by adding the alcohol to a slurry prepared by mixing the raw material of the magnesium support with a non-polar solvent such as hexane, or by adding a solution mixed with the non-polar solvent and the alcohol to the slurry and then stirring when it becomes a transparent solution at a temperature of 20 to 150°C. As a result of the mixing, a homogeneous solution of the magnesium support is obtained, and at this time, an additional product is formed in the solution in which the crystals of the magnesium support are surrounded by alcohol molecules.

[0135] Next, the step of supporting the titanium-containing compound for the preparation of the Ziegler-Natta catalyst is carried out by reacting the reaction product of the magnesium support and the alcohol produced in the support treatment step with the titanium-containing compound.

[0136] Specifically, the process can be carried out by directly adding the titanium-containing compound to the reaction product of the magnesium support and alcohol generated in the support treatment step, or by adding a solution in which the titanium compound is dissolved in a non-polar solvent, and reacting at -50 to 120°C or -20 to 80°C.

[0137] The types and content of the titanium-containing compounds mentioned above are as previously described.

[0138] In addition, when the titanium-containing compound is added, the reaction product of the magnesium support and the alcohol generated in the support treatment step may be stirred at 10 to 500 rpm or 50 to 400 rpm.

[0139] Meanwhile, when manufacturing the above-mentioned Ziegler-Natta catalyst, a step of introducing a halogenated hydrocarbon when introducing alcohol to the magnesium support during the support treatment step; introducing a halogenated hydrocarbon when introducing the titanium-containing compound during the titanium-containing compound support step; or introducing a halogenated hydrocarbon to react after the titanium-containing compound support step is completed may be further performed.

[0140] The types and contents of the above-mentioned halogenated hydrocarbons are as described above.

[0141] The Ziegler-Natta catalyst produced by the above-described manufacturing method may be used as is during polyethylene polymerization, or it may be used after being slurried in a non-polar solvent.

[0142] In addition, the above Ziegler-Natta catalyst can be used as a co-catalyst with an organometallic compound represented by the following chemical formula 2.

[0143] [Chemical Formula 2]

[0144] R 2 n MX 2 (3-n)

[0145] In the above chemical formula 2,

[0146] M is selected from the group of elements in groups IB, IIA, IIIB and IVB of the periodic table, and

[0147] R 2 Each is identical or different and is an alkyl group having 1 to 10 carbon atoms, and

[0148] X 2 is a halogen, and

[0149] n is an integer from 1 to 3.

[0150] In the above chemical formula 2, M is specifically aluminum, and R 2 is an alkyl group having 1 to 5 carbon atoms, or 2 to 4 carbon atoms, and X 2 is Cl or Br.

[0151] Specific examples of organometallic compounds represented by the above chemical formula 2 include triethylaluminum, methylaluminum dichloride, methylaluminum dibromide, dimethylaluminum chloride, dimethylaluminum bromide, propylaluminum dichloride, propylaluminum dibromide, butylaluminum dichloride, butylaluminum dibromide, dibutylaluminum chloride, dibutylaluminum bromide, isobutylaluminum dichloride, isobutylaluminum dibromide, diisobutylaluminum chloride, diisobutylaluminum bromide, hexylaluminum dichloride, hexylaluminum dibromide, dihexylaluminum chloride, dihexylaluminum bromide, octylaluminum dichloride, octylaluminum dibromide, dioctylaluminum chloride. Examples include dioctyl aluminum bromide, and any one or more of these may be used.

[0152] Meanwhile, since the above co-catalyst affects the polymerization activity of the magnesium-supported catalyst, the polymerization activity of the catalyst can be further increased by controlling the content of the co-catalyst. For example, in the case of the organometallic compound represented by Chemical Formula 2, aluminum may be used in an amount of 3 moles or more, 10 moles or more, or 25 moles or more, and 200 moles or less, or 100 moles or less, for every 1 mole of titanium in the catalyst.

[0153] The above co-catalyst may be added to the polyethylene polymerization reaction after mixing with the above Ziegler-Natta catalyst, or may be added separately before or after the addition of the Ziegler-Natta catalyst. Accordingly, the method for manufacturing a polyethylene resin composition according to the present invention may further include a process of adding the above co-catalyst during the production of the first polyethylene in step 1.

[0154] Meanwhile, the primary slurry polymerization reaction in the first process above is a copolymerization reaction between ethylene and a C4 to C10 alpha-olefin comonomer, and the amount of monomer input can be determined by considering the physical properties of the ethylene / alpha-olefin copolymer to be realized and the physical properties of the final polyethylene resin composition. For example, in the present invention, the C4 to C10 alpha-olefin comonomer may be input in an amount of 0.01 to 5 weight% based on the total weight of the ethylene. When input within the above content range, an increase in the TD direction elongation ratio can be achieved by increasing the ratio of low molecular weight and low crystallinity content.

[0155] In addition, the above primary slurry polymerization reaction is carried out under conditions of hydrogen gas input.

[0156] Since the amount of hydrogen gas introduced above affects the physical properties of the copolymer being manufactured, the amount introduced is appropriately determined according to the physical properties to be achieved. For example, in the present invention, the total amount of hydrogen gas introduced may be 0.001 to 0.5 weight% based on the total weight of the monomers including ethylene and alpha-olefin comonomers introduced into the first and second reactors. When hydrogen gas is introduced within the above range, the combined physical properties of the polyethylene resin composition described above can be easily achieved. More specifically, it may be introduced in an amount of 0.001 weight% or more, or 0.01 weight% or more, or 0.05 weight% or more, or 0.07 weight% or more, and 0.5 weight% or less, or 0.3 weight% or less, or 0.1 weight% or less.

[0157] In addition, the temperature and pressure conditions during the above primary slurry polymerization reaction are as defined above.

[0158] In addition, the above primary slurry polymerization reaction is carried out in a solvent. Specifically, a non-polar solvent such as hexane may be used as the solvent. The amount of solvent used is not particularly limited and can be appropriately determined by considering the amount of reactants used, etc.

[0159] In addition, the temperature of the solvent in the first reactor during the first slurry polymerization reaction may affect the degree of crystallization of the polymer. Accordingly, in the manufacturing method according to the present invention, the first slurry polymerization reaction in the first step may be carried out by circulating the solvent to an outer cooler connected to the first reactor and cooled to a temperature of 15 to 25°C, thereby maintaining the solvent temperature at 75 to 85°C. In this case, crystal formation is promoted, and as a result, the degree of crystallization may be further increased.

[0160] Accordingly, to control the temperature of the solvent in the first reactor, the first reactor may further be equipped with an outer cooler connected to the first reactor outside the reactor.

[0161] A first copolymer is prepared by a polymerization reaction under the above-mentioned manufacturing conditions.

[0162] Next, the secondary slurry polymerization reaction is carried out in a second reactor connected to the first reactor.

[0163] Specifically, the first copolymer produced in the first process is transferred to a second reactor connected to the first reactor, ethylene is introduced, and a second slurry polymerization reaction is performed in the presence of a Ziegler-Natta catalyst.

[0164] In the second reactor, a secondary slurry polymerization reaction takes place between the first copolymer transferred from the first reactor and the ethylene introduced into the second reactor.

[0165] The Ziegler-Natta catalyst used in the above secondary slurry polymerization reaction is as described in the first process. Accordingly, the Ziegler-Natta catalysts used in the primary and secondary slurry polymerization reactions may be the same or different. When the same Ziegler-Natta catalyst is used in the above primary and secondary slurry polymerization reactions, it may be easier to control the physical properties of the polyethylene resin composition being manufactured and to achieve the corresponding physical property conditions.

[0166] In addition, the above secondary slurry polymerization reaction may be carried out under conditions of hydrogen addition or no addition. For example, when hydrogen gas is added, hydrogen gas may be added in an amount of 0.001 to 0.05 weight% based on the total weight of ethylene introduced into the second reactor.

[0167] In addition, the temperature and pressure conditions during the secondary slurry polymerization reaction are as defined above.

[0168] An ethylene / alpha-olefin copolymer is produced as a result of the above-mentioned secondary slurry polymerization reaction.

[0169] Next, in the manufacturing method according to the present invention, the second step is to mix the ethylene / alpha-olefin copolymer prepared in the first step with a nucleating agent and then extrude to produce a polyethylene resin composition.

[0170] The above nucleating agent and its input amount are the same as previously explained.

[0171] In addition, during the extrusion process, one or more additives such as antioxidants, neutralizing agents, slip agents, anti-blocking agents, UV stabilizers, and antistatic agents may be added within a range that does not degrade the physical properties of the polyethylene resin composition.

[0172] For example, the above antioxidants may include phenolic antioxidants; phosphorus-based antioxidants; amine-based antioxidants, etc., and any one of these or a mixture of two or more may be used. Specific examples of the above antioxidants include phenolic antioxidants such as pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; phosphorus-based antioxidants such as tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite; Alternatively, amine-based antioxidants such as phenylnaphthylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, and N,N'-di-2-naphthyl-p-phenylenediamine may be used, and any one or a mixture of two or more of these may be used. In addition, commercially available Irganox™ 1010 (BASF), Irganox™ 3114 (BASF), Irganox™ 1076 (BASF), Irgafos™ 168 (BASF), Irgafos™ 626 (BASF), or Cyanox™ 1790 (CYTEC) may be used. Among these, considering the effect of improving film properties, the polyethylene resin composition may include a mixture of a phenol-based primary antioxidant and a phosphorus-based secondary antioxidant.At this time, the phenol-based primary antioxidant may be included in an amount of 50 ppm or more, or 200 ppm or more, or 250 ppm or more, and 500 ppm or less, or 300 ppm or less, based on the total weight of the polyethylene resin composition, and the phosphorus-based secondary antioxidant may be included in an amount of 100 ppm or more, or 300 ppm or more, or 500 ppm or more, and 1000 ppm or less, or 700 ppm or less, based on the total weight of the polyethylene resin composition.

[0173] In addition, the above neutralizing agent may include calcium stearate (Ca-St), calcium palmitate, zinc stearate, zinc palmitate, or hydrotalcite (magnesium aluminum hydroxy carbonate), and any one or more of these may be used. In addition, commercially available DHT-4A™ (manufactured by KYOWA) may be used. The above neutralizing agent may be included in an amount of 100 ppm or more, 300 ppm or more, or 500 ppm or more, and 1000 ppm or less, or 700 ppm or less, based on the total weight of the polyethylene resin composition.

[0174] Meanwhile, the above extrusion process can be performed using a conventional extruder.

[0175] For example, using an extruder such as a twin screw extruder, it can be performed at an extrusion temperature of 180 to 250°C or 180 to 230°C.

[0176] Typically, since the polymerization product obtained after the polymerization reaction in the first step is obtained in powder form, the types of additives, such as antioxidants, that can be used in the subsequent film manufacturing process are limited. Furthermore, because the antioxidant content varies significantly depending on the powder, there is a large variation in the physical properties of the articles manufactured using this method. However, if an extrusion process is performed, the constituent components, including the antioxidant, are uniformly mixed during the subsequent film manufacturing process, and the resulting articles can possess uniform physical properties.

[0177] A pellet-shaped polyethylene resin composition is obtained through the above extrusion process.

[0178] Meanwhile, in the present invention, a pellet or pellet-type refers to a small particle or piece formed by the extrusion of a raw material, and includes all forms classified as pellets in the relevant technical field, such as circular, flat, flaky, polygonal, and rod shapes. Furthermore, the size of the pellet is not particularly limited and is appropriately determined according to the use and shape; however, in order to distinguish it from powders having a small average diameter of typically 1 mm, the pellet in the present invention is defined as having an average diameter of 2 mm or more. At this time, "diameter" is the longest straight distance among any straight distances on the outer surface of the pellet, and can be measured using an imaging microscope or the like.

[0179] In addition, the second step may further include a process of cooling the pelletized extruded product to 30°C or lower after the extrusion.

[0180] When cooling is performed under the above-mentioned temperature conditions after extrusion, crystal growth is suppressed by the rapid cooling of the extruded product, and as a result, a polyethylene resin composition with excellent optical and surface properties can be produced. In addition, when biaxial stretching is performed using this, a BOPE film that is easy to print can be produced by improving COF and thickness variation.

[0181] Specifically, the above cooling is performed by cooling the extruded product to 30°C or lower, and a solvent such as hexane may be used for cooling.

[0182] In addition, during the above cooling, a conventional cooling device such as an outer cooler may be used.

[0183] A polyethylene resin composition satisfying the aforementioned physical property conditions is produced by the above-described manufacturing method. As a result, the polyethylene resin composition exhibits excellent stretchability, processability, and optical properties. Furthermore, the polyethylene resin composition can form a film with uniform thickness variation, and in particular, it is possible to manufacture a biaxially stretched film with excellent rigidity. Consequently, it is particularly useful for food packaging films.

[0184] Accordingly, the present invention provides a stretched film, specifically a biaxially stretched film, manufactured using the above-described polyethylene resin composition.

[0185] Specifically, the stretched film according to the present invention comprises the polyethylene resin composition described above.

[0186] In addition, the above-described stretched film exhibits excellent stretchability and strength characteristics by including the above-described polyethylene resin composition.

[0187] Specifically, the stretched film is stretched at a stretching ratio of 5×8 times (MD direction × TD direction) or more, more specifically 5×8 times or more and 7×12 times or less, or 6×10 times or less, or 5.5×9.5 times or less, and the thickness is 10 to 30 μm, more specifically 10 μm or more, or 15 μm or more, or 20 μm or more and 30 μm or less, or 25 μm or less, and satisfies the following conditions. In this case, the 'greater than' and 'less than' of the stretching ratio range are based on the stretching ratio value in the MD direction.

[0188] (i) The haze measured according to ISO 13468 standards is 6% or less, and

[0189] (ii) The thermal shrinkage rate in the MD direction calculated according to the following Equation 2 after shrinking at 100°C for 7 minutes in accordance with ASTM D 1204 is 3% or less, or 2% or less, and

[0190] (iii) The 1% secant modulus in the MD direction measured according to ASTM D882 is 1000 MPa or more, more specifically 1100 MPa or more, 2000 MPa or less, or 1500 MPa or less.

[0191] [Mathematical Formula 2]

[0192] Thermal shrinkage rate (%) = [(1 - Film length in MD direction after shrinkage) / Film length in MD direction before shrinkage] × 100

[0193] In addition, the above-mentioned stretched film may have a minimum stretching temperature of 120°C or higher, or 122°C or higher, and a maximum stretching temperature of 150°C or lower, or 130°C or lower.

[0194]

[0195] Preferred embodiments are presented below to aid in understanding the present invention. However, the following embodiments are provided merely to facilitate a better understanding of the invention and do not limit the scope of the invention.

[0196] Catalyst Manufacturing

[0197] Preparation Example

[0198] 34 g of anhydrous magnesium chloride (99 wt% or more, moisture content less than 1%) was added to a nitrogen-dried 2-liter Buchi reactor, and 600 ml of purified hexane with a moisture content of less than 0.5 ppm was added to the reactor. While stirring the resulting reaction mixture, 175 ml of anhydrous 2-ethyl-1-hexanol was added, and the mixture was stirred at a temperature of 130°C for about 2 hours to prepare a homogeneous solution of the magnesium support.

[0199] While stirring the homogeneous solution at a temperature of 35°C at a speed of 200 rpm, 200 ml of TiCl4 was slowly added over 1 hour and stirred for another 1 hour. During this process, a solid material was formed. After precipitating the solid material, the liquid phase was removed, and the separated solid material was washed several times with hexane until the titanium concentration in the washing solution was 0.5 mmol or less. Purified hexane was added to the washed solid material to make the total volume 1 liter. The titanium concentration in the resulting hexane slurry was 30 mM. To the hexane slurry, 7 ml of cyclohexyl chloride was added at a temperature of 40°C and stirred for 1 hour to obtain a magnesium-supported Ziegler-Natta catalyst.

[0200] As a result of analysis using the following method with an ICP-MS (Inductively Coupled Plasma Mass Spectrometer) (NexION 2200, manufactured by PerkinElmer), the prepared Ziegler Natta catalyst contained TiCl4 as the main catalyst, and also contained cyclohexyl chloride at a molar ratio of 0.13 based on 1 mole of the main catalyst, and the Mg:Ti molar ratio in the Ziegler Natta catalyst was 4:1.

[0201] The detection limits for ICP-MS analysis were 1 ppm (Ti), 1 ppm (Cl), and 1 ppm (Mg). Here, ppm refers to weight percentage.

[0202] The catalyst sample was first ash-diluted by a known method and then dissolved in a suitable acidic solvent. The dilution of the standard for the standard calibration curve was dissolved in the same solvent as the catalyst sample, and a concentration was selected such that the sample concentration corresponded to the standard calibration curve. The ash content was measured according to the ISO 3451-1 (1997) standard.

[0203] Specifically, about 0.7 g of the catalyst sample prepared above was placed in a platinum crucible (Pt crucible), about 1 mL of concentrated sulfuric acid (98 wt%, Electronic grade) was added, and the mixture was heated at 300°C for 3 hours. The resulting product was then placed in an electric furnace (Thermo Scientific, Lindberg Blue M) and batching was carried out according to the program of steps 1 to 3 below. To the resulting residue, 1 mL of concentrated nitric acid (48 wt%) and 20 µL of concentrated hydrofluoric acid (50 wt%) were added, the platinum crucible was sealed, and the mixture was shaken for at least 30 minutes. 1 mL of boric acid was added to the resulting product and stored at 0°C for at least 2 hours. Afterward, the mixture was diluted in 30 mL of ultrapure water, and the amounts of the main catalyst and cyclohexyl chloride, as well as the amounts of Mg and Ti in the catalyst, were measured.

[0204] 1) step 1: initial temp 0℃, rate (temp / hr) 180 ℃ / hr, temp(holdtime) 180℃ (1hr)

[0205] 2) step 2: initial temp 180℃, rate (temp / hr) 85 ℃ / hr, temp(holdtime) 370℃ (2hr)

[0206] 3) step 3: initial temp 370℃, rate (temp / hr) 47 ℃ / hr, temp(holdtime) 510℃ (3hr)

[0207]

[0208] In addition, the number average particle size of the catalyst was measured using a laser diffraction size analyzer (Helos-KR, manufactured by Sympatec GmbH). Specifically, 5 g of the magnesium-supported Ziegler-Natta catalyst obtained above was mixed with 2 L of n-hexane to prepare a measurement sample, and the catalyst particle size was measured by continuously introducing n-hexane into the measurement cell using n-hexane as the filling solvent. At this time, the measurement range was set to 0.1 µm to 35 µm. As a result of the measurement, the number average particle size of the Ziegler-Natta catalyst particles was 8 µm.

[0209]

[0210] Example 1-1

[0211] An ethylene / alpha-olefin copolymer was prepared by polymerizing in the presence of a Ziegler-Natta catalyst system using a bimodal slurry polymerization process with two 100L continuous stirred tank reactors (CSTR).

[0212] Specifically, in the first reactor, a first copolymer (first powder) was prepared by performing a primary polymerization reaction in a hexane solvent in the presence of ethylene under the conditions listed in Table 1 below, the Ziegler-Natta catalyst prepared in the above preparation example, hydrogen, and 1-butene as the first comonomer. At this time, 85 ml / hr of TEAL at a concentration of 0.2 mM was used as a co-catalyst. In addition, the temperature of the hexane in the first reactor was maintained at 82°C by circulating hexane through an outer cooler connected to the first reactor and having a temperature of 15°C to 25°C. At this time, the flow rate of hexane circulated to the outer cooler was 1 L / hr, the flow rate of hexane cooled and reintroduced into the first reactor was 5 L / hr, and the hexane in the first reactor was maintained at 122 L.

[0213] The first copolymer was transferred to a second reactor connected in series with the first reactor, and a polymerization reaction (secondary polymerization reaction) was performed by introducing ethylene under the conditions listed in Table 1 below to produce an ethylene / alpha-olefin copolymer as polyethylene.

[0214]

[0215] Examples 1-2 and Comparative Examples 1-1, 1-2

[0216] Polyethylene was prepared by performing the same method as in Example 1-1 above, except that the conditions were changed to those listed in Table 1 below.

[0217]

[0218]

[0219] In the table above, the amount of comonomer (1-butene) added (weight%) is based on the total weight of the monomer containing ethylene and 1-butene added to the first and second reactors.

[0220]

[0221] Meanwhile, the MI of the first and second polymerization products in Table 1 above 2.16 The polymerization product obtained after the completion of the polymerization reaction in the first reactor and the second reactor, respectively, was measured according to the ISO 1133 method at 190°C under a load of 2.16 kg.

[0222]

[0223] Experimental Example 1

[0224] The physical properties of the polyethylene prepared in the above examples and comparative examples were measured using the method described below, and the results are shown in Table 2.

[0225]

[0226] (1) Density

[0227] The density of polyethylene was measured at 23°C according to the ISO 1183-2 method.

[0228] Specifically, the powdered polyethylene finally prepared in the above examples and comparative examples, specifically the ethylene / alpha-olefin copolymer of Examples 1-1, 1-2 and Comparative Example 1-2, or the homopolyethylene of Comparative Example 1-1, is dried at 70°C for 24 hours, and then a square molded plate with a thickness of 2 mm is used in a heating press at a temperature of 190°C at 10 kg / cm² 2 The above dry powder is preheated for 3 minutes under a pressure of 50 kg / cm², and then 50 kg / cm² 2 After maintaining the pressure for 3 minutes, the specimen was prepared by rapidly cooling to 30°C, and the density of the prepared specimen was measured at 23°C according to the ISO 1183-2 method.

[0229]

[0230] (2) Melt Index MI 2.16

[0231] The melt index of polyethylene was measured according to the ISO 1133 method under a load of 2.16 kg at 190°C.

[0232]

[0233] (3) Content of structures derived from comonomers

[0234] The content of alpha-olefin comonomer-derived structures present in polyethylene 1 It was measured using H NMR (1B500, 500 MHz NMR).

[0235] Specifically, 0.1 g of polyethylene and 1 ml of D-solvent TCE (d2) were placed in a 5 ml vial and dissolved at 50°C. Then, the moles of ethylene and 1-butene in the corresponding ppm ranges were determined using an NMR analyzer (1B500, 500 MHz NMR) at a temperature of 385 K, and calculated according to Equation 1.

[0236] - Ethylene (4H): 1.2 ~ 1.6 ppm

[0237] - 1-Butene: 0.8 ~ 1.0 ppm

[0238] [Mathematical Formula 1]

[0239] Content of alpha-olefin comonomer-derived structure (weight%) = (Moles of 1-Butene) x 56.11 x 100 / [(Moles of ethylene) x 28 + (Moles of 1-Butene) x 56.11]

[0240]

[0241] Example 1-1 Example 1-2 Comparative Example 1-1 Comparative Example 1-2 Density 0.944 0.942 0.952 0.943 MI 2.16 [g / 10min] 0.8 1.2 1.2 0.9 Content of structures derived from comonomers (weight%) 1.1 1.3 0.0 1.8

[0242] In the table above, the unit weight % of the content of the comonomer-derived structure is based on the total weight of polyethylene.

[0243] Experimental results confirmed that the copolymers prepared according to the examples and comparative examples had similar levels of density and MI.

[0244]

[0245] <Preparation of Polyethylene Resin Composition>

[0246] Example 2-1

[0247] A polyethylene resin composition was prepared by mixing a nucleating agent into the ethylene / alpha-olefin copolymer prepared in Example 1-1 above under the conditions listed in Table 3 below, and then extruding and cooling.

[0248] Specifically, based on the total weight of the ethylene / alpha-olefin copolymer prepared in Example 1-1 above, 500 ppm of HPN-20E™ (manufactured by Milliken) was added as a nucleating agent and mixed, and then extruded at an extrusion temperature of 230°C using a twin screw extruder (TEK 30 MHS, manufactured by SMPLATECH CO., diameter 32 phi, L / D=40), and then the extruded product was immediately passed through a cooling water bath at 10°C or lower to rapidly cool it. The rapidly cooled extruded product was pelletized using a pelletizer to prepare a polyethylene resin composition.

[0249]

[0250] Examples 2-2 to 2-4, and Comparative Examples 2-1 to 2-5

[0251] A polyethylene resin composition was prepared by performing the same method as in Example 2-1 above, except that the conditions were changed to those listed in Table 3 below.

[0252]

[0253] Examples 2-5

[0254] A polyethylene resin composition was prepared by performing the same method as in Example 2-1 above, except that ADK STAB NA-11™ (manufactured by Adeka) was used as the nucleating agent as described in Table 3 below.

[0255]

[0256] Polyethylene Type Nucleating Agent Type Nucleating Agent Added Amount (ppm) Extrusion Temperature (°C) Example 2-1 Example 1-1 HPN-20E500230 Example 2-2 Example 1-2 HPN-20E500230 Example 2-3 Example 1-1 HPN-20E2,000230 Example 2-4 Example 1-2 HPN-20E2,000230 Example 2-5 Example 1-1 ADK STAB NA-11500230 Comparative Example 2-1 Comparative Example 1-1 HPN-20E500230 Comparative Example 2-2 Comparative Example 1-2 HPN-20E500230 Comparative Example 2-3 Comparative Example 1-1 HPN-20E300230 Comparative Example 2-4 Comparative Example 1-2HPN-20E300230 Comparative Example 2-5 Example 1-1--230

[0257] Comparative Example 2-6

[0258] As a polyethylene resin composition containing an ethylene / 1-hexene copolymer, LG Chem's XO2906™ was used.

[0259]

[0260] Comparative Example 2-7

[0261] ME1000™ from LG Chem was used as the polyethylene resin composition.

[0262]

[0263] Comparative Example 2-8

[0264] ME2500™ from LG Chem was used as the polyethylene resin composition.

[0265]

[0266] Comparative Example 2-9

[0267] LG Chem's LY5204™ was used as a polyethylene resin composition containing an ethylene / 1-butene copolymer.

[0268]

[0269] Comparative Example 2-10

[0270] LG Chem's XM3108BN™ was used as the polyethylene resin composition.

[0271]

[0272] Comparative Example 2-11

[0273] SE0327™ from LG Chem was used as the polyethylene resin composition.

[0274]

[0275] Comparative Example 2-12

[0276] HP1018BN™ from LG Chem was used as the polyethylene resin composition.

[0277]

[0278] Experimental Example 2

[0279] The physical properties of the polyethylene resin compositions of the above examples and comparative examples were measured using the method described below, and the results are shown in Tables 4 to 6, respectively.

[0280] (1) Density: Measured at 23℃ according to the ISO 1183-2 method.

[0281]

[0282] (2) Melt Index (MI) 2.16 ): Measured according to the ISO 1133 method under a load of 2.16 kg at 190℃.

[0283]

[0284] (3) Melting temperature (Tm), crystallization temperature (Tc) and processing temperature range

[0285] Using a Differential Scanning Calorimeter (DSC, device name: DSC Q20, manufacturer: TA instrument), the melting temperature (Tm) and crystallization temperature (Tc) of the polyethylene resin compositions of the examples and comparative examples were measured, the difference between the melting temperature and the crystallization temperature was calculated, and this was set as the processing temperature range (Tm-Tc).

[0286] Specifically, the temperature was raised to heat the polyethylene resin composition to 200°C at a rate of 10°C / min (first heating), and after isothermaling at 200°C for 5 minutes, it was cooled to -50°C at a rate of 10°C / min and isothermaled at -50°C for 5 minutes. Subsequently, it was heated again to 200°C at a rate of 10°C / min (second heating).

[0287] In the DSC curve obtained through this, the temperature at the peak of the endothermic peak was set as the melting temperature (Tm, °C), and the temperature at the peak of the exothermic peak was set as the crystallization temperature (Tc, °C). At this time, the melting temperature (Tm) and crystallization temperature (Tc) are the results measured in the sections where the temperature rises and falls, respectively, during secondary heating.

[0288]

[0289] (4) Melt strength (MS) (mN)

[0290] A sample of a polyethylene resin composition was connected to the Rheotens of a capillary rheometer (Gottfert’s Rheo-tester 2000), and the melt strength was measured 5 times under the following conditions, after which the average value was taken.

[0291] Specifically, a polyethylene resin composition was placed in a capillary die at a temperature of 200 ℃ and melted for 5 minutes, after which a filament of the polyethylene resin composition was discharged at a constant extrusion speed of 22 g / min and measured using a leotense. The maximum tensile stress until the discharged filament of the polyethylene resin composition broke was expressed as melt strength.

[0292] - Capillary die specifications: Diameter 4 mm, Length 25 mm, Lo / Do=6.25

[0293] - Distance from capillary die to rheothens wheel: 80 mm

[0294] - Capillary shear rate: 200 / s

[0295] - Leotens starting speed: 50mm / s

[0296] - Wheel acceleration: 1.2 cm / sec 2

[0297]

[0298] (5) Degree of crystallization (%)

[0299] The degree of crystallinity was determined using a Differential Scanning Calorimeter.

[0300] Specifically, the polyethylene resin composition prepared in the above examples and comparative examples was dried for 12 hours at a temperature of 140°C and a pressure of 10 mmHg, then 5 mg was sampled into an aluminum pan for liquids, and the heating and cooling cycle was repeated twice using a differential scanning calorimeter (DSC) of PerkinElmer Co., increasing the temperature from 25°C to 200°C at a rate of 10°C / min, maintaining it at 200°C for 5 minutes, and then cooling it down to -50°C at a rate of 10°C / min.

[0301] For the temperature rise curve appearing during the second cycle's heating process, a new baseline is established to ensure a smooth connection between the temperatures before and after melting from the onset to the end of the endothermic peak, thereby determining the melting peak, which is the highest endothermic peak, and the heat of fusion (△H) of the polyethylene resin composition is obtained by integrating the area of ​​the melting peak. f ...was calculated. Then, based on the heat of fusion of a polyethylene resin composition having a degree of crystallization of 100%, the degree of crystallization of the polyethylene resin composition was calculated according to the following mathematical formula 1.

[0302] [Mathematical Formula 1]

[0303] Degree of crystallization (%) = (△H f / △H0) × 100

[0304] Here, △H fis the heat of fusion (J / g) of the polyethylene resin composition, and △H0 is the heat of fusion (J / g) of the polyethylene resin composition having 100% crystallinity, using the heat of fusion value of 293.4 J / g of 100% crystalline polyethylene.

[0305]

[0306] (6) Crystal distribution ratio (%) at 25℃ to 70℃

[0307] Crystallization Elution Fractionation (CEF) analysis was performed on the polyethylene resin compositions of the above examples and comparative examples using the method described below, and the content ratio of the polymer fraction eluted by temperature range was determined.

[0308] Specifically, a 30 mg sample of a polyethylene resin composition was introduced into a CEF apparatus (manufactured by PolymerChar), dissolved in 8 mL of trichlorobenzene solvent at 160°C for 90 minutes, and then stabilized at 110°C for 15 minutes. This was cooled to 35°C at a cooling rate of 0.5°C / min while the solvent, trichlorobenzene, was flowed at a flow rate of 0.01 mL / min. After reaching 35°C, it was maintained for 5 minutes. Subsequently, while heating from 35°C to 135°C at a heating rate of 1°C / min, the solvent, trichlorobenzene, was flowed through a column at a flow rate of 0.5 mL / min, and the concentration of the eluted polymer was measured. Other measurement conditions are as follows. From the concentration measurement results above, a CEF analysis graph was derived with the elution temperature (Te) (°C) on the x-axis and the elution amount (dw / dt) on the y-axis. From the CEF analysis graph, the ratio of the crystal distribution at an elution temperature of 25°C to 70°C relative to the total crystal distribution, that is, the content ratio of the polymer fraction eluted at 25°C to 70°C, was determined. Specifically, the ratio of the peak area at 25°C to 70°C was calculated based on the total peak area in the CEF fraction graph. The peak area was obtained through integration.

[0309] <CEF 측정 조건>

[0310] Stabilization Temperature: 110 ℃

[0311] Stabilization Rate: 30 ℃ / min

[0312] Crystallization Rate: 0.5 ℃ / min

[0313] Elution Rate: 1 ℃ / min

[0314] Cleaning temperature: 140 ℃

[0315] Cleaning rate: 30 ℃ / min

[0316] Cleaning time: 10 min

[0317] Dissolution temperature: 160 ℃

[0318] Crystallization temperature: 35 ℃

[0319] Elution init. temp: 35 ℃

[0320] Elution temperature: 135 ℃

[0321] Dissolution time: 90 min

[0322] Stabilization time: 15 min

[0323] Crystallization time: 5 min

[0324] Soluble Fraction time: 5 min

[0325]

[0326] (6) 분자량 분포 (MWD)

[0327] The polyethylene resin compositions of the above examples and comparative examples were analyzed by gel permeation chromatography (GPC) to measure the weight-average molecular weight (Mw) and number-average molecular weight (Mn), respectively, and the molecular weight distribution (MWD, Mw / Mn) was obtained by dividing the weight-average molecular weight measured above by the number-average molecular weight.

[0328] Specifically, the measurement samples were analyzed using a Waters PL-GPC220 instrument with a Polymer Laboratories PLgel MIX-B 300 mm long column. The measurement temperature was 160°C, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL / min. The polyethylene resin composition samples were pretreated by dissolving them in 1,2,4-trichlorobenzene containing 0.0125% BHT at 160°C for 10 hours using the GPC analyzer PL-GP220, prepared to a concentration of 10 mg / 10 mL, and supplied in a volume of 200 μL. The values ​​of Mw and Mn were measured using a calibration curve formed with a polystyrene standard. Nine types of polystyrene standards were used, with molecular weights of 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

[0329]

[0330] (7) Film characteristics evaluation

[0331] (7-1) Haze

[0332] After manufacturing a biaxially stretched film using the polyethylene resin compositions of the above examples and comparative examples by the method described below, the haze of the film was measured according to ISO 13468 standards.

[0333] <Manufacture of Biaxially Stretched Films>

[0334] - Manufacture of a 0.72 mm thick casting sheet of polyethylene composition using a Bruckner lab extruder line (L / D ratio: 42, Screw diameter: 25 mm, Melt / T-Die temperature: 250 ℃)

[0335] - Biaxial stretching performed on a polyethylene composition measuring 90 mm x 90 mm with a thickness of 0.8 mm using KARO 5.0 equipment

[0336] - Perform sequential stretching (MD→TD) after preheating for 100 seconds at 120 ℃ for each

[0337] - Stretching speed: 200 % / s

[0338] - Final film thickness (based on a stretch ratio of 5x8): 20㎛

[0339]

[0340] (7-2) Thermal shrinkage rate

[0341] For the biaxially stretched films of the example and comparative example prepared in (7-1) above, the length of each film was measured after shrinking at 100°C for 7 minutes according to ASTM D 1204, and the heat shrinkage rate was calculated according to the following mathematical formula 2.

[0342] [Mathematical Formula 2]

[0343] Thermal shrinkage rate (%) = [(1 - Film length in MD direction after shrinkage) / Film length in MD direction before shrinkage] × 100

[0344]

[0345] (7-3) Minimum film stretching temperature and maximum film stretching temperature

[0346] Using a Bruckner Karo 5.0 Lab stretcher, the polyethylene resin compositions of the above examples and comparative examples were prepared into a sheet with a thickness of 1.2 mm, then stretched 5 times in the MD direction, and immediately followed by stretching 8 times in the TD direction to produce a film with a thickness of 30 μm.

[0347] At this time, if the film is stretched at a stretching ratio of 5 x 8 times without being destroyed and the force applied to the stretching clip is 10 N or more, it was determined that normal stretching has occurred. In addition, the lowest stretching temperature at which normal stretching begins with a force of 10 N or more was defined as the 'lowest film stretching temperature', and the highest stretching temperature was defined as the 'highest film stretching temperature'.

[0348] On the other hand, when a force of 10 N or less is applied, it is determined that a melt drawing phenomenon occurs in which the amorphous region melts and stretches rather than the arrangement and orientation of the polymer. In this case, the thickness variation of the film is 20% or more, so it cannot be considered that a normal film is formed.

[0349]

[0350] (7-4) 1% secant modulus

[0351] For the biaxially stretched films of the example and comparative example prepared in (7-1) above, the 1% secant modulus in the machine direction (MD) and transverse direction (TD) of the film was measured according to ASTM D882 using an Instron Universal Testing Machine (UTM).

[0352]

[0353]

[0354]

[0355]

[0356]

[0357]

[0358] Experimental results confirmed that the polyethylene resin composition of the example exhibits excellent elongation and processability compared to the comparative example, and that the film manufactured using it also exhibits excellent optical properties and rigidity.

Claims

1. One or more ethylene / alpha-olefin copolymers; and It includes a nucleating agent, Density of 0.940 to 0.960 g / cm³ measured according to ISO 1183-2 at 23℃ 3 And, When measured by CEF (Crystallization Elution Fractionation), the ratio of the crystal distribution at 25°C to 70°C relative to the total crystal distribution is 15.0 to 21.0%, Polyethylene resin composition.

2. In Paragraph 1, The above polyethylene resin composition has a melt index MI when measured according to the ISO 1133 method under a load of 2.16 kg at 190°C. 2.16 A polyethylene resin composition having a g of 0.6 to 1.5 g / 10 min.

3. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a processing temperature range defined as the value obtained by subtracting the crystallization temperature from the melting temperature, which is 13℃ or higher.

4. In Paragraph 1, The above polyethylene resin composition has a melting temperature of 120 to 150 Polyethylene resin composition at ℃.

5. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a crystallization temperature of 125°C or lower.

6. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a melt strength of 70 mN or more at 170°C.

7. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a degree of crystallinity of 60% or more calculated according to the following mathematical formula 1: [Mathematical Formula 1] Degree of crystallization (%) = (△H f / △H0) × 100 In mathematical formula 1, △H f is the heat of fusion (J / g) of the polyethylene resin composition, and △H0 is the heat of fusion (J / g) of the polyethylene resin composition having 100% crystallinity, which is 293.4 J / g.

8. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a molecular weight distribution of 8.0 to 12.

0.

9. In Paragraph 1, A polyethylene resin composition wherein the above ethylene / alpha-olefin copolymer satisfies either or both of the following conditions (b1) and (b2): (b1) Density of 0.940 to 0.960 g / cm³ when measured by the ISO 1183-2 method at 23℃, (b2) Melt index (MI) measured according to the ISO 1133 method under a load of 2.16 kg at 190°C 2.16 ) is 0.5 to 5.0g / 10min.

10. In Paragraph 1, The above ethylene / alpha-olefin copolymer is a polyethylene resin composition comprising 0.5 to 1.6 weight% of an alpha-olefin-derived structure based on the total weight of the copolymer.

11. In Paragraph 1, The above ethylene / alpha-olefin copolymer is a polyethylene resin composition that is a copolymer of ethylene and 1-butene.

12. In Paragraph 1, The above nucleating agent comprises a metal carboxylic acid salt, a metal phosphate salt, an inorganic nucleating agent, or a mixture thereof, in a polyethylene resin composition.

13. In Paragraph 12, A polyethylene resin composition in which the metal in the above-mentioned carboxylic acid metal salt is an alkali metal of Group 1, an alkaline earth metal of Group 2, or a transition metal of Group 12.

14. In Paragraph 12, A polyethylene resin composition in which the metal in the metal phosphate salt is an alkali metal of Group 1 or a metal of Group 13.

15. In Paragraph 1, The above nucleating agent comprises calcium cis-hexahydrodicarboxylate, calcium bicyclo[2.2.1]heptane-2,3-dicarboxylate, sodium benzoate, 4-tert-butylbenzoate aluminum, sodium adipose, bicyclo[2.2.1]heptane-2,3-dicarboxylate sodium, sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl)phosphate, hydroxybis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1.3.2)-dioxaphosphosine 6-oxidato) aluminum, talc, calcium oxide, mica, or a mixture thereof, in a polyethylene resin composition.

16. In Paragraph 1, A polyethylene resin composition in which the nucleating agent is included in an amount of 300 to 3,000 ppm based on the total weight of the ethylene / alpha-olefin copolymer.

17. A first step of producing an ethylene / alpha-olefin copolymer by polymerizing ethylene and alpha-olefin comonomers through a multimodal slurry polymerization process in the presence of a Ziegler-Natta catalyst and hydrogen; A second step of mixing the above ethylene / alpha-olefin copolymer with a nucleating agent and then extruding; comprising The multimodal slurry polymerization process in the first step comprises: a first process for producing a first copolymer by primary slurry polymerization reaction of ethylene and an alpha-olefin comonomer in the presence of a Ziegler-Natta catalyst in a first reactor while introducing hydrogen; and a second process for producing an ethylene / alpha-olefin copolymer by transferring the first copolymer to a second reactor connected to the first reactor, introducing ethylene, and secondary slurry polymerization reaction in the presence of a Ziegler-Natta catalyst. Method for manufacturing a polyethylene resin composition according to claim 1.

18. In Paragraph 17, A manufacturing method in which the primary slurry polymerization reaction in the first step is performed by circulating the solvent to an external cooler at 15 to 25°C connected to the first reactor, thereby maintaining the solvent temperature at 75 to 85°C.

19. In Paragraph 17, The above second step further comprises a process of cooling the extruded product to 30°C or lower after extrusion, a manufacturing method.

20. In Paragraph 17, A manufacturing method in which the total amount of the alpha-olefin comonomer input is 0.005 to 1.50 weight% based on the total weight of the monomers including ethylene and the alpha-olefin comonomer input into the first reactor and the second reactor.

21. A stretched film comprising a polyethylene resin composition according to claim 1.

22. In Paragraph 21, The above stretched film is stretched in the MD direction × TD direction with a stretching ratio of 5 × 8 or more, and when the thickness is 20 μm, The haze measured according to ISO 13468 standards is 6% or less, and According to ASTM D 1204, the thermal shrinkage rate in the MD direction calculated according to the following Equation 2 after shrinking at 100°C for 7 minutes is 3% or less, and A stretched film having a 1% secant elastic modulus in the MD direction of 1000 MPa or more, measured according to ASTM D882. [Mathematical Formula 2] Thermal shrinkage rate (%) = [(1 - Film length in MD direction after shrinkage) / Film length in MD direction before shrinkage] × 100

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