Polyethylene resin composition and film comprising same

Abstract

The present invention relates to: a polyethylene resin composition capable of producing a film having excellent stretching process stability and excellent transparency and rigidity during stretching; and to a stretched film manufactured therefrom.

Description

Polyethylene resin composition and film containing the same

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

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0190238 filed December 18, 2024 and Korean Patent Application No. 10-2025-0196417 filed December 11, 2025, and all contents disclosed in said documents are incorporated herein as part of this specification.

[0003] The present invention relates to a polyethylene resin composition and a stretched film comprising the same.

[0004] With the recent increase in consumer interest in the environment, single-material packaging that is easy to recycle is gaining attention. Notably, the food packaging and distribution industries are trending toward manufacturing "All-PE" films using only polyethylene (PE), a general-purpose material.

[0005] Conventional multilayer film packaging materials have used composite materials in which BOPP (bi-axially oriented polypropylene), BOPET (biaxially-oriented polyethylene terephthalate), or BOPA (biaxially-oriented polyamide) are applied to the printing layer. However, since these composite materials are not recyclable, research and development are underway to manufacture single-material packaging films by replacing the printing layer film with PE. To replace the printing layer film with PE, higher physical properties and transparency than existing PE blown films are required.

[0006] Meanwhile, biaxially oriented polyethylene (BOPE) film is manufactured by stretching a cast sheet in the machine direction (MD) and transverse direction (TD), respectively, and has significantly superior tensile strength, impact strength, and transparency compared to conventional blown films.

[0007] Conventional development of resins for BOPE has focused on linear low-density polyethylene (LLDPE), which has excellent stretchability due to its low density. However, when manufacturing BOPE films with LLDPE, there are problems such as severe shrinkage and poor heat resistance, making it difficult to apply to printing layers. In addition, while high-density polyethylene (HDPE) has excellent physical properties, it has problems such as high crystallinity, making it difficult to stretch, and low transparency of the film.

[0008] Accordingly, there is a need to develop a high-density polyethylene resin composition that not only exhibits excellent stretchability but also simultaneously satisfies transparency and excellent mechanical strength when manufactured into a film.

[0009] One objective of the present invention is to provide a polyethylene resin composition that has excellent stretchability, high transparency when manufactured into a film, and excellent mechanical properties such as rigidity.

[0010] Another objective of the present invention is to provide a stretched film comprising the above-described polyethylene resin composition that has a uniform thickness, excellent appearance characteristics such as high transparency, and excellent mechanical rigidity.

[0011] However, the technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0012] According to one embodiment of the present invention, the invention relates to a polyethylene resin composition comprising an ethylene homopolymer or an ethylene / alpha olefin copolymer having 3 to 20 carbon atoms, wherein a film made of the polyethylene resin composition includes a stem region when observed at a magnification of 10,000 using a scanning electron microscope (SEM), and when the SEM image is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region is 5,000 pixels or more, and preferably 5,500 pixels or more and 15,000 pixels or less.

[0013] The above polyethylene resin composition has a density of 0.940 g / cm³ or higher as measured according to ASTM D792, and preferably 0.940 g / cm³ 3 Above 0.970 g / cm³ 3 It may be less than.

[0014] The above polyethylene resin composition has a melt index (MI) when measured under a load of 2.16 kg at 190 ℃. 2.16 ) may be 0.50 to 3.00 g / 10 min.

[0015] The above polyethylene resin composition may have a molecular weight distribution curve in which the log value of the weight-average molecular weight (Mw) (log Mw) is the x-axis and the molecular weight distribution (dw / dlog Mw) for the log value is the y-axis, through gel permeation chromatography (GPC) analysis, such that the area ratio of the region in which 4.5 ≤ log Mw ≤ 5.5 out of the total area is 40% or more and 51% or less.

[0016] The above polyethylene resin composition may have a number of short chain branches (SCB) with 2 to 7 carbon atoms per 1,000 carbon atoms of 2.0 or more and 6.0 or less.

[0017] The film produced from the above polyethylene resin composition may have a haze of 6% or less.

[0018] The film made from the above polyethylene resin composition may have a stiffness of 900 MPa or more and 1500 MPa or less in the length direction (MD), and a stiffness of 1500 MPa or more and 2500 MPa or less in the width direction (TD).

[0019] As a preferred example, the polyethylene resin composition may satisfy all of the conditions (i) to (vi) below. Conditions (iv) to (vi) below are based on a film made of the polyethylene resin composition.

[0020] (i) Density is 0.940 g / cm³ 3 Above 0.970 g / cm³ 3 Below;

[0021] (ii) In a molecular weight distribution curve obtained through gel permeation chromatography (GPC) analysis, where the log value of the weight-average molecular weight (Mw) (log Mw) is on the x-axis and the molecular weight distribution for said log value (dw / dlog Mw) is on the y-axis, the proportion of the area of ​​the region where 4.5 ≤ log Mw ≤ 5.5 out of the total area is 40% or more and 51% or less;

[0022] (iii) The polyethylene resin composition has a number of short chain branches (SCB) having 2 to 7 carbon atoms per 1,000 carbon atoms of 2.0 or more and 6.0 or less;

[0023] (iv) When the 10,000x magnification SEM image is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region within the total area is between 5,500 pixels and 15,000 pixels;

[0024] (v) Haze is 6% or less;

[0025] (vi) The stiffness in the longitudinal direction (MD) is 900 MPa or more and 1500 MPa or less, and the stiffness in the transverse direction (TD) is 1500 MPa or more and 2500 MPa or less.

[0026] According to another embodiment of the present invention, the invention relates to a cast sheet comprising the polyethylene resin composition described above.

[0027] According to another embodiment of the present invention, the invention relates to a biaxially stretched film comprising the polyethylene resin composition described above.

[0028] The above film may satisfy all of conditions (i) to (vi). The following (iv) to (vi) are based on a film made of the above polyethylene resin composition.

[0029] (i) Density is 0.940 g / cm³ 3 That's all;

[0030] (ii) In a molecular weight distribution curve obtained through gel permeation chromatography (GPC) analysis, where the log value of the weight-average molecular weight (Mw) (log Mw) is on the x-axis and the molecular weight distribution for said log value (dw / dlog Mw) is on the y-axis, the proportion of the area of ​​the region where 4.5 ≤ log Mw ≤ 5.5 out of the total area is 40% or more and 51% or less;

[0031] (iii) The number of short chain branches (SCBs) with 2 to 7 carbon atoms per 1,000 carbon atoms is 2.0 or more and 6.0 or less;

[0032] (iv) When the 10,000x magnification SEM image is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region within the total area is 5,000 pixels or more;

[0033] (v) Haze is 6% or less;

[0034] (vi) The stiffness in the longitudinal direction (MD) is 900 MPa or more and 1500 MPa or less, and the stiffness in the transverse direction (TD) is 1500 MPa or more and 2500 MPa or less.

[0035] In addition, the film may have an average stiffness in the length direction (MD) and stiffness in the width direction (TD) of 1300 MPa or more and 2300 MPa or less.

[0036] The thickness of the above film may be 10 to 100 μm.

[0037] The polyethylene resin composition of the present invention not only exhibits excellent stretchability, but the film produced therefrom, particularly the stretched film, also possesses balanced and excellent mechanical properties such as transparency (i.e., appearance characteristics) and stiffness. Therefore, the aforementioned film can be utilized as a film printed with logos, labels, barcodes, etc., or as a stand-up pouch, and is also suitable for use as a packaging material for various other purposes.

[0038] Unless otherwise defined in this specification, all technical and scientific terms 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 presence 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.

[0039] 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.

[0040] The technical terms used in this specification are intended merely to refer to specific embodiments and are not intended to limit the invention. Furthermore, the singular forms used herein include plural forms unless the phrases clearly indicate otherwise.

[0041] In this specification, the terms “polyethylene” or “ethylene (co)polymer” include both ethylene homopolymers and / or copolymers of ethylene and alpha-olefins.

[0042] In addition, throughout this specification, the term “polyethylene resin composition” encompasses all resin compositions that include the ethylene (co)polymer, or in which additives, generally belonging to the technical field to which the present invention belongs, may be further added to such homopolymers or copolymers. Meanwhile, the polyethylene resin composition may be a resin that includes an ethylene (co)polymer without long chain branches.

[0043] In this specification, "stiffness" may refer to initial stiffness obtained by measuring the slope of the stress-strain curve up to the 1% strain point, "Young's Modulus" may refer to pure elastic stiffness obtained by measuring the slope of the stress-strain curve up to the yield point, and "tensile modulus" may refer to overall tensile performance representing the rate of change over the entire range until break-up.

[0044] According to one embodiment of the present invention, the polyethylene resin composition has a density of 0.940 g / cm³ or more as measured according to ASTM D792, and includes a stem region when a film made of the polyethylene resin composition is observed with a scanning electron microscope (SEM), and when the SEM image is fixed to a size of 640 pixels X 440 pixels, the total area of ​​the stem region is 5,000 pixels or more of the total area.

[0045] Conventional high-density polyethylene (HDPE) resins, while possessing excellent physical properties, suffered from problems such as high crystallinity making stretching difficult and low film transparency. Consequently, attempting to lower crystallinity to improve film transparency resulted in a decline in mechanical properties.

[0046] Meanwhile, during the biaxial stretching process of a polyethylene resin composition, when the polymer crystals are first stretched in the longitudinal direction (Machine Direction, MD), they are aligned in a certain direction. Subsequently, when the polymer crystals are secondarily stretched in the width direction (Transverse Direction, TD), reorientation occurs in the amorphous regions between the lamellar in addition to the aligned crystals, thereby forming stem-shaped regions and web-shaped regions on the film surface. Through diligent efforts, the inventors of the present invention discovered that when manufacturing a biaxially stretched film from a polyethylene resin composition, the degree of formation of stem-shaped and web-shaped regions on the film surface has a high correlation not only with the processability of the stretch but also with mechanical properties such as the transparency and stiffness of the film. Furthermore, the inventors discovered a polyethylene resin composition that allows for the production of a film with excellent biaxial processability, excellent appearance characteristics, and excellent stiffness, in which the stem-shaped and web-shaped regions are formed in a balanced manner during stretching, thereby completing the present invention.

[0047] The above-described polyethylene composition has a density of 0.940 g / cm³ 3 It may be abnormal. Specifically, the density is 0.940 g / cm³. 3 Above, 0.941 g / cm³ 3 Above, 0.942 g / cm³ 3 Above, 0.943 g / cm³ 3 Above, 0.944 g / cm³ 3 Above, or 0.945 g / cm³ 3 Above, 0.970 g / cm³ 3 Below, 0.965 g / cm³ 3 Below, 0.964 g / cm³ 3 Below, 0.963 g / cm³ 3 Below, 0.960 g / cm³ 3 Below, 0.958 g / cm³ 3 Below, 0.955 g / cm³ 3 Below, 0.953 g / cm³ 3 Less than, or 0.950 g / cm³ 3 It may be less than or equal to, preferably 0.940 g / cm³ 3 Above, 0.970 g / cm³ 3 Less than; or 0.940 g / cm³ 3 Above, 0.965 g / cm³ 3 Less than; or 0.940 g / cm³ 3 Above, 0.955 g / cm³ 3 It may be less than or equal to the following. The density of the above 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 0.970 g / cm² 3 If it exceeds, the stretchability of the film may be reduced due to the excessively high density.

[0048] The above density (g / cm³) 3 ) can be measured according to ASTM D792 standards, for example, and may be a value measured at 23 ℃.

[0049] In addition, the polyethylene resin composition has a high density as described above, along with a melt index (MI 2.16 ) may be 0.50 to 3.00 g / 10 min. Melt index (MI) of the polyethylene resin composition 2.16 ) may be related to film processability and dimensional stability during the manufacture of stretched films. The above melt index (MI 2.16 If ) is less than 0.50 g / 10min, the processing pressure increases, leading to reduced processability, and if it exceeds 3.00 g / 10min, bubble stability deteriorates due to high fluidity, which may result in variations in film thickness. The melt index (MI) of the above polyethylene resin composition 2.16 ) may be 0.50 g / 10min or more, or 0.80 g / 10min or more, or 1.00 g / 10min or more, or 1.20 g / 10min or more, or 1.25 g / 10min or more, or 1.30 g / 10min or more, and 3.00 g / 10min or less, or 2.50 g / 10min or less, or 2.00 g / 10min or less, or 1.80 g / 10min or less, or 1.65 g / 10min or less, or 1.60 g / 10min or less. Specific examples include 0.50 to 3.00 g / 10min, 1.00 to 3.00 g / 10min, 1.00 to 2.50 g / 10min, or 1.00 to 2.00 g / 10min.

[0050] The above melt index (MI) 2.16 ) can be measured at 190°C under a 2.16 kg load according to ASTM D1238 standards and can be expressed as the weight (g) of the polymer melted over 10 minutes.

[0051] The above polyethylene resin composition can obtain a molecular weight distribution curve with the logarithm of the weight-average molecular weight (Mw) (log Mw) on the x-axis and the molecular weight distribution for the logarithm (dw / dlog Mw) on the y-axis through gel permeation chromatography (GPC) analysis.

[0052] In order to manufacture a film having high stiffness or in which the stem region is formed to a level greater than the desired level upon stretching of the above polyethylene resin composition, the weight-average molecular weight (Mw) is 10 4.5 to 10 5.5 There must be a sufficient amount of polymer within the range. Accordingly, the polyethylene resin composition of the present invention may have an area ratio of the polymer region having 4.5 ≤ log Mw ≤ 5.5 in the above molecular weight distribution curve of 40% or more, 40.5% or more, 41% or more, 41.5% or more, or 42% or more of the total area, and may be 52% or less, 51.5% or less, 51% or less, 50.5% or less, or 50% or less, and preferably may be 40% or more and 51% or less.

[0053] In the above molecular weight distribution curve, if the area ratio of the low molecular weight polymer region with 4.5 ≤ log Mw ≤ 5.5 is less than 40%, the stem region may not be formed to the desired level during stretching, which may reduce the mechanical strength of the film. Additionally, if the area ratio exceeds 52%, the stem may be excessively developed, and during secondary stretching in the TD direction, there may not be enough polymer crystals for reorientation between the lamellae to occur, which may result in fracture and reduced stretchability.

[0054] In the above molecular weight distribution curve, the area ratio of 4.5 ≤ log Mw ≤ 5.5 can be calculated from the fraction (%) of the polymer satisfying the corresponding weight-average molecular weight from the GPC analysis results.

[0055] In addition, when stretching the polyethylene resin composition, the web region must be formed in a balanced manner as a chain acting as an anchoring between the lamellae after the formation of the stem region to enable stretching into a film of uniform thickness without breakage and to ensure excellent appearance characteristics of the stretched film. The polyethylene resin composition of the present invention may include a short chain branch (SCB) associated with the formation of the web region in a limited amount.

[0056] Specifically, the short chain (SCB) is a short chain having 2 to 7 carbon atoms bonded to the polyethylene polymer main chain in a branch-like form, and can be formed when an alpha-olefin having 4 or more carbon atoms, such as 1-butene, 1-hexene, or 1-octene, is used as a comonomer. The SCB content refers to the number of branched chains having 2 to 7 carbon atoms per 1,000 carbon atoms (unit: number / 1,000 C), and may be proportional to the content of α-olefin monomers included in the polymer chains. While this SCB content can be calculated through analysis using Fourier Transform Infrared Spectroscopy (FT-IR), Proton Nuclear Magnetic Resonance (PNR) 1 It can also be calculated using H-NMR.

[0057] The SCB content derived from FT-IR analysis relative to the total moles of the entire composition in the above polyethylene composition may be 2.0 (pieces / 1000C) or more and 6.0 (pieces / 1000C) or less. Preferably, the SCB content may be 2.5 (pieces / 1000C) or more, 3.0 (pieces / 1000C) or more, 3.5 (pieces / 1000C) or more, or 4.0 (pieces / 1000C) or more, and 6.0 (pieces / 1000C) or less, 5.7 (pieces / 1000C) or less, or 5.0 (pieces / 1000C) or less.

[0058] If the above SCB content is less than 2.0 (pieces / 1000C), the stretchability may be reduced, such as by failing to form a sufficient web area to connect the stems during stretching and causing breakage. If the SCB content exceeds 6.0 (pieces / 1000C), the mechanical strength of the stretched film may be reduced.

[0059] In addition, when the above-described polyethylene resin composition is manufactured into a film, the total area of ​​the stem region within the total area may be 5,000 pixels or more, based on a scanning electron microscope (SEM) image of the film at 10,000x magnification fixed at 640 pixels x 440 pixels (width x height).

[0060] The area of ​​the stem region refers to the number of pixels of enclosed white blocks corresponding to the stem region in a threshold image calculated by simplifying the SEM image of the film surface according to shading criteria to have black and white pixels.

[0061] To measure the area ratio of the stem region, the brightness values ​​of the SEM image of the film surface at the aforementioned magnification and size can first be normalized. That is, the contrast ratio of the image can be adjusted so that the brightness value of the darkest part of the image becomes 0 and the brightness value of the brightest part becomes 255. A Histogram Equalization algorithm can be used for normalizing the image. Next, the brightness of each pixel can be converted to white (1) or black (0) based on a specific threshold to obtain a binary image. The threshold for the binary conversion is not specifically limited and, for example, can be based on the median value of the total pixel brightness values. The binary conversion process can be performed using the otsu algorithm of the CV2 library. Among the enclosed white (1) regions included in the obtained binary image, regions with a pixel size of 60 or less can be preprocessed into black (0). Subsequently, the FindContours function can be used on the preprocessed image to track the outlines of white (1) pixels, and each outline can be represented as a polygon to return coordinates. Then, the Skeletonization algorithm is used to repeatedly remove the outlines of the white (1) region while maintaining the main shape of the white (1) region, and the number of pixels included in the centerline when the thickness (short axis) of the white (1) region becomes 1 pixel is defined as the area of ​​each stem region. The total area of ​​the stem region in the obtained SEM image of the film surface can be represented as the sum of the number of pixels in the centerline for each stem region.The Histogram Equalization algorithm, FindContours function, and Skeletonization algorithm used in the above image processing process are provided by data analysis platforms. While those provided by programs such as Python, R, and MATLAB, or the OpenCV library, may be used, they are not limited to these, and any program with such capabilities may be used without restriction.

[0062] In the present invention, the area ratio of the stem region can be obtained by processing the SEM image using the DX method (Digital Transformation Method) in addition to the method described above. Here, the DX method refers to a process of converting an image into an optimal image based on digital technology such as artificial intelligence. The DX method may be based on at least one of a rule-based algorithm and a learning-based algorithm. The "rule-based algorithm" is not particularly limited as long as it corresponds to known methods such as a "threshold detection algorithm" (e.g., Threshold) and an "image contour detection algorithm" (findContours), provided that it does not deviate from the scope of the present invention. Furthermore, the "learning-based algorithm" is not particularly limited as long as it corresponds to known methods such as CNN-based deep learning, provided that it does not deviate from the scope of the present invention.

[0063] In the present invention, the total area of ​​the stem region may be the average of the total area values ​​of the stem regions of each image obtained by observing the surface of 10 randomly selected parts of a biaxially stretched film made of the above-described polyethylene resin composition, cut to a size of 10 cm x 10 cm, at a magnification of 10,000 using a scanning electron microscope (SEM). Here, the biaxially stretched film is a film having a thickness in the range of about 20 to 40 μm, and as an example, it may be based on a biaxially stretched film having a thickness of about 25 ± 5 μm.

[0064] The total area of ​​the stem region may be 5,000 pixels or more, 5,500 pixels or more, 6,000 pixels or more, 6,500 pixels or more, 7,000 pixels or more, or 7,500 pixels or more, and 20,000 pixels or less, 15,000 pixels or less, 14,000 pixels or less, or 13,000 pixels or less. Preferably, the total area of ​​the stem region may be 5,000 pixels or more and 20,000 pixels or less; or 5,000 pixels or more and 15,000 pixels or less; or 5,500 pixels or more and 15,000 pixels or less; or 6,000 pixels or more and 15,000 pixels or less.

[0065] If the area ratio of the stem region falls outside the aforementioned range, an oriented crystal structure may not be sufficiently formed or the stem region and web region may not be formed in a balanced manner, which may increase the haze of the film or decrease the stiffness of the film.

[0066] As such, the polyethylene resin composition according to the present invention has excellent stretchability.

[0067] The above-described polyethylene resin composition can be uniaxially or biaxially stretched with a stretching ratio of 4 to 8 times in the length (MD) direction or 5 to 10 times in the width (TD) direction.

[0068] As an example, the above polyethylene resin composition can be biaxially stretched with a stretching ratio of 4 to 8 times in the length (MD) direction and 7 to 10 times in the width (TD) direction.

[0069] As another example, the above polyethylene resin composition can be biaxially stretched with a stretching ratio of 5 times in the length (MD) direction and 8 times in the width (TD) direction.

[0070] In this specification, "excellent stretchability" or "stretchable" means that when a sheet made of the above-described polyethylene resin composition is uniaxially stretched or biaxially stretched at the corresponding stretching ratio, no breakage, melting, shrinkage, or melt drawing occurs in the film. Furthermore, it may mean that the average thickness of the stretched film is greater than 14 μm, greater than 15 μm, greater than 16 μm, greater than 17 μm, greater than 18 μm, greater than 19 μm, or greater than 20 μm, and the thickness deviation is less than 5 μm, less than 4 μm, less than 3 μm, or less than 2.5 μm, but is not limited thereto. Alternatively, the average thickness of the stretched film may be 1.25% or more, 1.6% or more, 1.7% or more, 1.8% or more, 1.9% or more, or 2.0% or more of the average thickness of the sheet before stretching, and the upper limit may be 3% or less, or 2.5% or less, although the upper limit is not specifically restricted.

[0071] The average thickness and standard deviation of the film described in this specification are the average and standard deviation values ​​of thickness values ​​measured at 20 or more non-overlapping points on a stretched film (e.g., a stretched film with dimensions of 210 mm in width and 297 mm in length). The thickness measurement method may be performed using a thickness gauge, but may also be measured by other methods known in the art to which the present invention belongs.

[0072] As such, the polyethylene resin composition of the present invention has low haze characteristics and high stiffness characteristics when manufactured into a film. The haze and stiffness below are based on the polyethylene resin composition being manufactured into a film having a thickness in the range of about 20 to 40 μm, as an example, into a biaxially stretched film having a thickness of about 25 ± 5 μm.

[0073] Specifically, the haze may be 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less, or 5% or less. Since a lower haze value is better, the lower limit is not specifically limited, but, for example, it may be 0.5% or more or 1% or more.

[0074] The above haze can be measured according to ISO 13468 standards.

[0075] The above film has high stiffness in both the length direction (MD) and the width direction (TD). Specifically, the stiffness in the length direction (MD) may be 900 MPa or more, 950 MPa or more, 1000 MPa or more, 1050 MPa or more, 1100 MPa or more, 1150 MPa or more, or 1200 MPa or more, and 1500 MPa or less, or 1400 MPa or less. Preferably, it may be 900 MPa or more and 1500 MPa or less.

[0076] In addition, the stiffness in the width direction (TD) may be 1200 MPa or more, 1400 MPa or more, 1600 MPa or more, 1700 MPa or more, 1800 MPa or more, 1900 MPa or more, 2000 MPa or more, or 2100 MPa or more, and may be 2500 MPa or less, or 2400 MPa or less. Preferably, it may be 1500 MPa or more and 2500 MPa or less.

[0077] In addition, the average of the stiffness in the reference length direction (MD) and the stiffness in the width direction (TD) of the film may be 1200 MPa or more, 1300 MPa or more, 1400 MPa or more, 1500 MPa or more, or 1600 MPa or more, and 2300 MPa or less, or 2100 MPa or less. Preferably, it may be 1300 MPa or more and 2300 MPa or less.

[0078] The above stiffness can be measured according to ASTM D 882 standards.

[0079] In the polyethylene resin composition according to the present invention, the polyethylene may be an ethylene homopolymer or an ethylene / alpha olefin copolymer having 3 to 20 carbon atoms. More specifically, the copolymer may be an ethylene / alpha olefin copolymer having 4 to 10 carbon atoms, and specific examples may be an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, an ethylene / 1-octene copolymer, or a mixture of two or more of these, but are not limited thereto.

[0080] The above-described polyethylene resin composition can be prepared by polymerizing ethylene by introducing hydrogen gas in the presence of a catalyst, or by copolymerizing ethylene with a comonomer. In this case, the polyethylene resin composition having the above-described characteristics can be realized by controlling the manufacturing method as follows, in addition to controlling the low molecular weight polymer or SCB content.

[0081] The above comonomer may be an olefin monomer. The olefin monomer may be an olefin compound having 3 to 20 carbon atoms or 4 to 10 carbon atoms. Specific examples include 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, and any one or more of these may be used. More specifically, the above olefin monomer may be 1-butene, 1-hexene, or 1-octene, and preferably two or more of these may be used, but are not limited thereto.

[0082] The amount of the above comonomer added may be determined according to the physical properties of the polyethylene to be manufactured, but considering the physical properties of the polyethylene to be realized in the present invention, it may be added in an amount of 3.0 to 10.0 weight% based on the total weight of ethylene. More specifically, it may be 3.0 weight% or more, 3.5 weight% or more, 4.0 weight% or more, 4.3 weight% or more, or 4.5 weight% or more, and 10.0 weight% or less, 9.0 weight% or less, 8.0 weight% or less, 7.5 weight% or less, or 7.3 weight% or less.

[0083] In addition, the input amount of the above comonomer may be 10 to 20 ml / min, 11 to 19 ml / min, or 12 to 18 ml / min based on ethylene being input into the reactor at a rate of 10 kg / hr. Furthermore, when the above comonomer is used as a single type, the input amount may be 16 to 20 ml / min or more, and hydrogen may be injected at a rate of 14 g / hr or more. In addition, when the above comonomer is used as two types, the total input amount of the comonomer may be 14 to 20 ml / min, and hydrogen may be injected at a rate of 14 g / hr or more, preferably 16 g / hr or more. Thus, the polyethylene resin composition produced by mutually controlling the type of comonomer, the input amount, and the hydrogen injection amount can achieve a balanced realization of appearance characteristics such as transparency and mechanical properties such as stiffness when manufacturing a stretched film.

[0084] The above polymerization reaction may be carried out in the presence of a catalyst. In this case, the catalyst may be a Ziegler-Natta catalyst, a metallocene catalyst, or a mixture thereof, but is not limited thereto.

[0085] The metallocene catalyst may include one or more of a first metallocene compound selected from compounds represented by the following chemical formula 1; and a second metallocene compound selected from compounds represented by the following chemical formula 2. Preferably, it may include one or more first metallocene compounds selected from compounds represented by the following chemical formula 1 and one or more second metallocene compounds selected from compounds represented by the following chemical formula 2.

[0086] [Chemical Formula 1]

[0087]

[0088] In the above chemical formula 1,

[0089] M1 is a group 4 transition metal, and

[0090] X 11 and X 12 Each independently, substituted or unsubstituted C 1-20 It is an alkyl or halogen, and

[0091] R1 to R5 and R7 to R 12 Each independently contains hydrogen, substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-60 Aryl, or -(CH2) n1 -OR 13 And,

[0092] R6 is substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-60 Aryl, or -(CH2) n1 -OR 13 However,

[0093] R1 to R 12 At least one of them is -(CH2) n1 -OR 13 And,

[0094] R 13 is substituted or unsubstituted C 1-20 It is alkyl, and

[0095] n1 is an integer from 0 to 10.

[0096] [Chemical Formula 2]

[0097]

[0098] In the above chemical formula 2,

[0099] M2 is a group 4 transition metal, and

[0100] X 21 and X 22 Each independently, substituted or unsubstituted C 1-20 It is an alkyl or halogen, and

[0101] T2 is C (carbon) or Si (silicon), and

[0102] Q 21 and Q 22 C, each independently substituted or unsubstituted 1-20Alkyl, substituted, or unsubstituted C 6-60 Aryl, or -(CH2) n2 -OR 32 Or, Q 21 and Q 22 C that combines with each other to become substituted or non-substituted 3-20 Forming a cycloalkyl ring,

[0103] R 20 to R 31 Each independently contains hydrogen, substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-60 Aryl, or -(CH2) n2 -OR 32 Or, R 20 to R 31 Among them, two adjacent C's are combined to form a substituted or unsubstituted C' 3-20 Forms a cycloalkyl ring,

[0104] R 20 to R 31 , Q 21 and Q 22 At least one of them is -(CH2) n2 -OR 32 And,

[0105] R 32 is substituted or unsubstituted C 1-20 It is alkyl, and

[0106] n2 is an integer from 0 to 10.

[0107] In the present invention, the substituents of the above chemical formula are described in more detail as follows.

[0108] Halogens can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0109] The above C 1-20 The alkyl group may be a straight-chain, branched-chain, or cyclic alkyl group. Specifically, the above C 1-20The alkyl group may be a straight-chain alkyl having 1 to 20 carbon atoms; a straight-chain alkyl having 1 to 10 carbon atoms; a straight-chain alkyl having 1 to 5 carbon atoms; a branched-chain or cyclic alkyl having 3 to 20 carbon atoms; a branched-chain or cyclic alkyl having 3 to 15 carbon atoms; or a branched-chain or cyclic alkyl having 3 to 10 carbon atoms. More specifically, the alkyl having 1 to 20 carbon atoms may be a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a tert-butyl group, an n-pentyl group, an iso-pentyl group, or a cyclohexyl group, etc.

[0110] C 3-20 The cycloalkyl ring may be a ring composed of carbon atoms. It may be a hydrocarbon ring having 3 to 20 carbon atoms; a hydrocarbon ring having 3 to 15 carbon atoms; or a hydrocarbon ring having 3 to 10 carbon atoms. More specifically, C 3-20 The cycloalkyl ring can be a cyclopropene ring, a cyclobutene ring, a cyclopentene ring, or a cyclohexene ring, etc.

[0111] C 2-20 The alkenyl can be a straight-chain, branched-chain, or cyclic alkenyl. Specifically, the above C 2-20 The alkenyl of may be a straight-chain alkenyl having 2 to 20 carbon atoms, a straight-chain alkenyl having 2 to 10 carbon atoms, a straight-chain alkenyl having 2 to 5 carbon atoms, a branched-chain alkenyl having 3 to 20 carbon atoms, a branched-chain alkenyl having 3 to 15 carbon atoms, a branched-chain alkenyl having 3 to 10 carbon atoms, a cyclic alkenyl having 5 to 20 carbon atoms, or a cyclic alkenyl having 5 to 10 carbon atoms. More specifically, C 2-20 The alkenyl of may be ethenyl, propenyl, butenyl, fentenyl, or cyclohexanyl, etc.

[0112] C 1-20 The alkoxy group may be a straight-chain, branched-chain, or cyclic alkoxy group. Specifically, the above C 1-20The alkoxy group may be a straight-chain alkoxy group having 1 to 20 carbon atoms; a straight-chain alkoxy group having 1 to 10 carbon atoms; a straight-chain alkoxy group having 1 to 5 carbon atoms; a branched-chain or cyclic alkoxy group having 3 to 20 carbon atoms; a branched-chain or cyclic alkoxy group having 3 to 15 carbon atoms; or a branched-chain or cyclic alkoxy group having 3 to 10 carbon atoms. More specifically, the alkoxy group having 1 to 20 carbon atoms may be a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, an iso-butoxy group, a tert-butoxy group, an n-pentoxy group, an iso-pentoxy group, a neo-pentoxy group, or a cyclohexoxy group, etc.

[0113] C 2-20 Alkoxyalkyl is -R y -OR z A structure containing alkyl(-R y One or more hydrogens of ) are alkoxy(-OR z It may be a substituent substituted with ). Specifically, the above carbon atoms C2 to C 20 The alkoxyalkyl group may be a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an iso-propoxymethyl group, an iso-propoxyethyl group, an iso-propoxyhexyl group, a tert-butoxymethyl group, a tert-butoxyethyl group, or a tert-butoxyhexyl group, etc.

[0114] C 6-60 Aryl may refer to monocyclic, bicyclic, or tricyclic aromatic hydrocarbons. Specifically, the C6 to C 60 The aryl group can be a phenyl group, a naphthyl group, or anthracenyl group, etc.

[0115] C 7-20 Alkylaryl may refer to a substituent in which one or more hydrogens of an aryl are substituted by an alkyl group. Specifically, the above C 7-20 The alkylaryl of may be methylphenyl, ethylphenyl, n-propylphenyl, iso-propylphenyl, n-butylphenyl, iso-butylphenyl, tert-butylphenyl, or cyclohexylphenyl, etc.

[0116] C7-20 Arylalkyl may refer to a substituent in which one or more hydrogens of an alkyl group are substituted by an aryl group. Specifically, the above C 7-20 The arylalkyl group can be a benzyl group, phenylpropyl or phenylhexyl, etc.

[0117] In addition, group 4 transition metals may include titanium, zirconium, hafnium, etc.

[0118] The above metallocene catalyst may be a hybrid catalyst comprising a first metallocene compound of high molecular weight and high crystallinity and a second metallocene compound of low molecular weight and low crystallinity.

[0119] In copolymerization in a single reactor using a hybrid metallocene catalyst, it is important to control the expression of polymerization characteristics between the metallocene compounds constituting the hybrid metallocene catalyst under a single copolymerization condition. In particular, to obtain a polyethylene polymer for biaxial stretching, high molecular weight, highly crystalline components and low molecular weight, low-crystalline components must be composed together. The polyethylene copolymer of the present invention can express each characteristic under a single polymerization condition by using a hybrid metallocene catalyst obtained from a combination of the first metallocene compound and the second metallocene compound.

[0120] The first metallocene compound represented by Chemical Formula 1 above has the characteristic of having a lower polymerization rate of the comonomer and a higher polymerization rate of the ethylene monomer compared to the second metallocene compound due to the structure of the non-bridged ligand bonded to the central metal. As a result, high molecular weight, highly crystalline polyethylene can be produced under ethylene / 1-hexene copolymerization conditions.

[0121] Meanwhile, the second metallocene compound represented by Chemical Formula 2 has the characteristic of having a high polymerization rate of the comonomer and a low polymerization rate of the ethylene monomer compared to the first metallocene compound due to the bridge-type ligand structure bonded to the central metal. As a result, low molecular weight, low-crystallinity polyethylene can be produced under ethylene / 1-hexene copolymerization conditions.

[0122] Preferably, the central metal (M1) of Formula 1 may be a group 4 transition metal specifically Ti, Zr, or Hf, and more specifically Hf or Zr.

[0123] Preferably, X 11 , X 12 Each can independently be methyl or chloro, and more preferably X 11 , X 12 All of them may be methyl or all of them may be chloro.

[0124] Preferably, R1 to R5 and R7 to R 12 Each independently contains hydrogen, substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-20 Aryl, or -(CH2) n1 -OR 13 And, R6 is substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-20 Aryl, or -(CH2) n1 -OR 13 However, R1 to R 12 One or two of them are -(CH 2)n1 -OR 13 It could be.

[0125] Preferably, either R7 or R8 is -(CH2) n1 -OR 13 While, the remainder and R1 to R5 and R9 to R 12 Each independently contains hydrogen, substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-60Aryl, or -(CH2) n1 -OR 13 And, R6 is substituted or unsubstituted C 1-20 Alkyl, substituted, or unsubstituted C 6-60 Aryl, or -(CH2) n1 -OR 13 It could be.

[0126] Preferably, R1 to R5 are each independently hydrogen, methyl, isopropyl, n-butyl, phenyl, or -(CH2) n1 -OR 13 It may be. More preferably, R1 to R5 may each independently be hydrogen, methyl, n-butyl, phenyl, or tert-butoxyhexyl.

[0127] Preferably, R6 is unsubstituted or C 6-10 C substituted with aryl or Si(R')3 1-20 alkyl, or C 6-20 It could be Aril, and here R' is C 1-20 alkyl or C 6-10 It may be an aryl. More preferably, R6 is unsubstituted or C substituted with phenyl, trimethylsilyl, or triphenylsilyl. 1-20 alkyl, or C 6-20 It may be an aryl. Most preferably, R6 may be methyl, ethyl, isopropyl, benzyl, trimethylsilylmethyl, or phenyl.

[0128] Preferably, either R7 or R8 is -(CH2) n1 -OR 13 While being, the remainder and R9 to R 12 Each may be hydrogen. More preferably, either R7 or R8 is tertbutoxyhexyl, and the remainder and R9 to R 12 Each can be hydrogen.

[0129] Preferably, R 13 It can be tertbutyl.

[0130] Preferably, n1 can be an integer from 4 to 10, more preferably, n1 can be an integer from 4 to 7, and most preferably, n1 can be 6.

[0131] Preferably, the first metallocene compound represented by the above formula 1 may be any one selected from the group consisting of the following:

[0132]

[0133] Meanwhile, the method for preparing the first metallocene compound represented by the above chemical formula 1 is not particularly limited, but, for example, it can be prepared by the method shown in the following reaction formula 1.

[0134] Although the compound represented by the above chemical formula 1 is difficult to synthesize due to the steric hindrance of the indene ligand, the compound of the above chemical formula 1 can be prepared with high yield and high purity according to a method such as the following reaction scheme 1.

[0135] Accordingly, according to one embodiment of the present invention, the compound represented by Formula 1 may be prepared by a manufacturing method comprising: a step of preparing a ligand of Formula 1-3 by reacting a compound represented by Formula 1-1 with a compound represented by Formula 1-2; and a step of reacting the ligand of Formula 1-3, a compound represented by Formula 1-4, and a halogen salt of a transition metal represented by Formula 1-5:

[0136] [Reaction Equation 1]

[0137]

[0138] In the above reaction scheme 1, M1, X 11 , X 12 and R1 to R 12 is as defined in Chemical Formula 1 above, and X' is independently a halogen.

[0139] Preferably, the central metal (M2) of Formula 2 may be a group 4 transition metal such as Ti, Zr, or Hf, and more specifically, Zr.

[0140] Preferably, X 21 , X 22 Each can independently be methyl or chloro, and more preferably X 21 , X 22 Each can be chloro.

[0141] Preferably, T2 can be C (carbon).

[0142] Preferably, R 20 to R 31 , Q 21 and Q 22 At least one of them is -(CH2) n2 -OR 32 It can be. More preferably, R 20 to R 25 , Q 21 and Q 22 At least one of them is -(CH2) n2 -OR 32 It can be. More preferably, R 20 to R 31 , Q 21 and Q 22 One or two of them are -(CH2) n2 -OR 32 It can be. More preferably, R 20 to R 25 , Q 21 and Q 22 One or two of them are -(CH2) n2 -OR 32 It can be. Most preferably, R 20 to R 25 , Q 21 and Q 22 Either one or two of them may be tertbutoxyhexyl.

[0143] Preferably, Q 21 and Q 22C, each independently substituted or unsubstituted 1-20 Alkyl, substituted, or unsubstituted C 6-20 Aryl, or -(CH2) n2 -OR 32 Or, Q 21 and Q 22 C that combines with each other to be substituted or unsubstituted 3-20 It can form a cycloalkyl ring. More preferably, Q 21 and Q 22 are independently methyl, ethyl, isopropyl, phenyl, or -(CH2) n2 -OR 32 Or, Q 21 and Q 22 They can combine with each other to form a cyclopentene ring or a cyclohexene ring.

[0144] Preferably, R 20 to R 23 Each independently, hydrogen, C 1-20 Alkyl, C 6-20 Aryl, or -(CH2) n2 -OR 32 It can be, and more preferably, R 20 to R 23 Each can independently be hydrogen, methyl, n-butyl, phenyl, or tertbutoxyhexyl. More preferably, R 20 to R 23 One is tertbutoxyhexyl or n-butyl, and the rest are hydrogen, or R 20 to R 23 Two of them may each independently be methyl, n-butyl, or phenyl, and the remainder may be hydrogen.

[0145] Preferably, R 24 to R 31 Each independently, hydrogen, C 1-10 Alkyl, C 6-20 Aryl, or -(CH2) n2 -OR 32 Or, R 24 to R 31Among them, two adjacent C's are combined to form a substituted or unsubstituted C' 3-10 It can form a cycloalkyl ring. More preferably, R 24 to R 31 Each is independently hydrogen, tertbutyl, or tertbutoxyhexyl, or R 24 to R 31 Two adjacent ones can combine to form a cyclohexane ring substituted with four methyl groups.

[0146] Preferably, R 32 It could be tertbutyl.

[0147] Preferably, n2 can be an integer from 4 to 10, more preferably, n2 can be an integer from 4 to 7, and most preferably, n2 can be 6.

[0148] Preferably, the metallocene compound represented by Formula 2 may be any one selected from the group consisting of the following:

[0149]

[0150] Meanwhile, the method for preparing the second metallocene compound represented by the above chemical formula 2 is not particularly limited, but, for example, it can be prepared by the method shown in reaction formula 2 below.

[0151] Although the compound represented by the above chemical formula 2 is difficult to synthesize due to the steric hindrance of the indene ligand, the compound of the above chemical formula 2 can be prepared with high yield and high purity according to a method such as the following reaction scheme 2.

[0152] Accordingly, according to one embodiment of the present invention, the compound represented by Formula 2 may be prepared by a method comprising the steps of: reacting a compound represented by Formula 2-1 with a compound represented by Formula 2-2 to produce a compound represented by Formula 2-3; reacting a compound represented by Formula 2-3 with a compound represented by Formula 2-4 to produce a ligand of Formula 2-5; and reacting the ligand of Formula 2-5 with a halogen salt of a transition metal represented by Formula 2-6.

[0153] [Reaction Equation 2]

[0154]

[0155] In the above reaction scheme 2,

[0156] M2, X 21 , X 22 , T2, Q 21 , Q 22 and R 20 to R 31 is as defined in the above chemical formula 2, and X" is independently a halogen.

[0157] In the above-described hybrid metallocene catalyst, the first metallocene compound and the second metallocene compound may be included in a molar ratio of 1:1 to 25:1, 2:1 to 25:1, 3:1 to 25:1, 3:1 to 23:1, or 3:1 to 20:1. If the ratio of the first metallocene compound to the second metallocene compound is less than 1:1, the high crystal content is low, making it difficult for the stretched film to have heat resistance; and if the ratio of the first metallocene compound to the second metallocene compound exceeds 25:1, the low crystal content is low, making biaxial stretching processability difficult.

[0158] The above metallocene catalyst may be a metallocene supported catalyst comprising a carrier that supports a metallocene compound. As the carrier, a carrier containing hydroxyl groups on its surface may be used, and preferably, a carrier having highly reactive hydroxyl groups, silanol groups, or siloxane groups on its surface may be used. For this purpose, a carrier that has been surface-modified by calcination or has had moisture removed from its surface by drying may be used.

[0159] For example, silica prepared by calcining silica gel, silica dried at high temperatures, silica-alumina, and silica-magnesia may be used, and these may typically contain oxide, carbonate, sulfate, and nitrate components such as Na2O, K2CO3, BaSO4, and Mg(NO3)2.

[0160] When used in the above supported catalyst state, the particle shape and bulk density of the polymer produced are excellent, and it can be used in conventional slurry polymerization, bulk polymerization, or gas phase polymerization processes. In addition, among the various supports, since the functional groups of the transition metal compound are chemically bonded and supported on the silica support, there is almost no catalyst released from the surface of the support during the ethylene polymerization process, and as a result, fouling caused by the reactor walls or polymer particles sticking together can be minimized when producing polyethylene copolymers by slurry or gas phase polymerization.

[0161] The above-mentioned carrier may have an average particle size (D50) of 20 to 60 μm. When having the above-mentioned particle size, transition metal compounds can be supported with superior efficiency, and as a result, catalytic activity can be increased. More specifically, it may be 20 μm or more, or 25 μm or more, and 60 μm or less, or 50 μm or less.

[0162] Meanwhile, the average particle size (D50) of the above carrier refers to the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size (particle diameter). The above D50 can be measured using the laser diffraction method. Specifically, the carrier to be measured is dispersed in a dispersion medium such as deionized water, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. The particle size at the point that is 50% of the cumulative distribution of the number of particles according to particle size in the measuring device is calculated and used as the average particle size.

[0163] In addition, when supported on the above-mentioned carrier, the metallocene compound may be supported in a content range of 1 mmol or more, 10 mmol or more, 15 mmol or more, 20 mmol or more, 25 mmol or more, or 30 mmol or more, based on 1,000 g of the carrier, and 500 mmol or less, 400 mmol or less, 300 mmol or less, 200 mmol or less, 100 mmol or less, 80 mmol or less, 60 mmol or less, or 52.5 mmol or less. When the metallocene compound includes both the first metallocene compound and the second metallocene compound, each compound may be supported in the above-mentioned amounts. When supported in the above-mentioned content range, appropriate supported catalyst activity is exhibited, which may be advantageous in terms of maintaining catalyst activity and economic efficiency.

[0164] In addition, the metallocene catalyst may further include a co-catalyst to improve high activity and process stability.

[0165] Specifically, the above co-catalyst may include one or more of the compounds represented by the following chemical formula 3.

[0166] [Chemical Formula 3]

[0167] -[Al(R 41)-O] a -

[0168] In the above chemical formula 3,

[0169] R 41 is a halogen; or C substituted or unsubstituted with a halogen 1-20 It is hydrocarbil;

[0170] a is an integer greater than or equal to 2.

[0171] Meanwhile, in this specification, the hydrocarbyl group is a monovalent functional group in which a hydrogen atom has been removed from a hydrocarbon, and may include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, aralkyl groups, aralkenyl groups, aralkinyl groups, alkylaryl groups, alkenylaryl groups, and alkynylaryl groups, etc. Furthermore, the hydrocarbyl group having 1 to 20 carbon atoms may be a hydrocarbyl group having 1 to 15 carbon atoms or 1 to 10 carbon atoms. Specifically, the hydrocarbyl group having 1 to 20 carbon atoms is a straight-chain, branched-chain, or cyclic alkyl group such as a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, or a cyclohexyl group; Or it may be an aryl group such as a phenyl group, a naphthyl group, or anthracenyl group.

[0172] Examples of compounds represented by the above chemical formula 3 include alkylaluminoxane compounds such as methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, or butylaluminoxane, and any one or more of these may be used.

[0173] Among the compounds mentioned above, the co-catalyst may be, more specifically, an alkylaluminoxan-based co-catalyst such as methylaluminoxan.

[0174] The above alkylaluminoxane-based co-catalyst can further enhance catalytic activity by including a metal element that stabilizes the first and second metallocene compounds and acts as a Lewis acid to form a bond through Lewis acid-base interaction with the functional group introduced into the bridge group of the first and second metallocene compounds.

[0175] In addition, the amount of the above co-catalyst used can be appropriately adjusted according to the physical properties or effects of the desired catalyst and polyethylene copolymer. For example, when silica is used as the carrier, the above co-catalyst can be supported in an amount of 100g or more, 1000g or more, or 2000g or more, and 6000g or less, or 5500g or less, or 5400g or less, based on 1000g of silica.

[0176] A hybrid metallocene catalyst according to the present invention having the above-described composition can be manufactured by a manufacturing method comprising the steps of: supporting a co-catalyst compound on a carrier; and supporting the first and second metallocene compounds on the carrier. In this case, the order of supporting the co-catalyst and the first and second metallocene compounds may be changed as needed, and the order of supporting the first and second metallocene compounds may also be changed as needed. The first and second metallocene compounds may be supported simultaneously. Considering the effect of the supported catalyst with a structure determined by the order of support, among these, sequentially supporting the first and second metallocene compounds after supporting the co-catalyst on the carrier allows the manufactured supported catalyst to achieve superior process stability along with high catalytic activity in the manufacturing process of polyethylene copolymers.

[0177] As described above, the hybrid supported metallocene catalyst can exhibit excellent catalytic activity by including first and second metallocene compounds having a specific structure. Accordingly, the hybrid supported metallocene catalyst can be suitably used for the polymerization of ethylene and olefin monomers.

[0178] In addition, the polymerization reaction is carried out under conditions of hydrogen input. The amount of hydrogen input may be determined according to the physical properties of the polyethylene to be manufactured, but considering the physical properties of the polyethylene to be realized in the present invention, it may be input at an amount of 1300 ppm or more, 1400 ppm or more, or 1500 ppm or more based on the weight of the monomer ethylene, and at 2500 ppm or less, 2300 ppm or less, 2100 ppm or less, or 2000 ppm or less. Specifically, it may be input in an amount of 1300 to 2300 ppm, or 1500 to 2000 ppm.

[0179] The above polymerization reaction can be carried out at a temperature of 60°C or higher, 70°C or higher, or 80°C or higher, and 90°C or lower, or 85°C or lower.

[0180] In addition, when controlling the pressure conditions during the above polymerization reaction, 5 kgf / cm 2 Above, or 7 kgf / cm² 2 This is the limit, and 20 kgf / cm² 2 Less than or equal to 15 kgf / cm² 2 Less than or equal to 10 kgf / cm² 2 It can be performed under the following pressure.

[0181] When the polymerization reaction is carried out under the above-mentioned temperature and pressure conditions, the desired physical properties of the polyethylene resin composition can be achieved more easily.

[0182] In addition, after the above polymerization reaction, an additional polymerization reaction can be performed on the unreacted monomers contained in the polymerization reaction product in a post-reactor.

[0183] At this time, the additional polymerization reaction can be carried out under the same reaction conditions as the polymerization reaction above, specifically at a temperature of 70 to 90 ℃ and a pressure of 5 to 10 bar.

[0184] The above polymerization reaction can be carried out as a gas phase polymerization reaction or a slurry polymerization reaction. Accordingly, it can be carried out using a single gas phase polymerization reactor, a continuous slurry polymerization reactor, or a loop slurry reactor.

[0185] Meanwhile, the method for manufacturing a polyethylene resin composition according to the present invention may further include a step of adding and mixing one or more of an antioxidant and a neutralizing agent to the polymerization product manufactured after the completion of the polymerization reaction described above. In addition, the manufacturing method may further include a step of melting and extruding the resulting mixture after the mixing step.

[0186] Examples of the above antioxidants include phenolic antioxidants; phosphorus-based antioxidants; amine-based antioxidants or sulfur compounds, and any one or more of these may be used.

[0187] In addition, specific examples of the above-mentioned phenolic antioxidants include 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, and any one or more of these may be used. In addition, phosphorus-based antioxidants include tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and any one or more of these may be used. In addition, the above-mentioned amine-based antioxidants may include phenylnaphthylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, and N,N'-di-2-naphthyl-p-phenylenediamine, and any one or a mixture of two or more of these may be used. Also, commercially available Irganox TM 1010 (BASF), Irganox TM 3114 (BASF), Irganox TM 1076 (BASF manufactured), Irgafos TM 168 (BASF), Irgafos TM 626 (BASF) or Cyanox TM You can also use 1790 (manufactured by CYTEC), etc.

[0188] In addition, the polyethylene resin composition may include a mixture of a phenolic primary antioxidant and a phosphorus-based secondary antioxidant. In this case, the phenolic primary antioxidant and the phosphorus-based secondary antioxidant may be included in a weight ratio of 5:1 to 1:5. More specifically, they may be included in a weight ratio of 3:1 to 1:3, or 2:1 to 1:1.

[0189] The above antioxidant may be included in an amount of 2500 ppm or less based on the total weight of the polymerization product obtained as a result of the polymerization reaction, specifically polyethylene. More specifically, the above antioxidant may be included in an amount of 2500 ppm or less, or 2000 ppm or less, or 1500 ppm or less based on the total weight of the polyethylene, or in an amount of 500 ppm or more, or 800 ppm or more, or 1000 ppm or more.

[0190] In addition, the above neutralizing agent may include fatty acid metal salts; or hydrotalcite (magnesium aluminum hydroxy carbonate) or a similar compound thereof (hydrotalcite-like compound), and any one or more of these may be used.

[0191] In the above fatty acid metal salt, the metal may be an alkaline earth metal or a transition metal. In addition, the above fatty acid may be a saturated fatty acid having 13 to 36 carbon atoms, and more specifically, it may be a saturated fatty acid having 13 or more carbon atoms, or 14 or more carbon atoms, or 16 or more carbon atoms, or 36 or fewer carbon atoms, or 20 or fewer carbon atoms, or 18 or fewer carbon atoms. Specific examples of the above fatty acid metal salt include calcium stearate (Ca-St), zinc stearate, magnesium stearate, calcium palmitate, or zinc palmitate, and any one or more of these may be used. In addition, commercially available DHT-4A (manufactured by KYOWA), etc., may be used as the above neutralizing agent.

[0192] The above neutralizing agent may be included in an amount of 2000 ppm or less based on the total weight of the polymerization product obtained as a result of the polymerization reaction, specifically polyethylene. More specifically, the above neutralizing agent may be included in an amount of 100 ppm or more, or 300 ppm or more, or 500 ppm or more, or 1000 ppm or more, and 2000 ppm or less, or 1500 ppm or less, or 1300 ppm or less based on the total weight of polyethylene.

[0193] Meanwhile, the polyethylene resin composition according to the present invention may further include one or more additives, such as a nucleating agent, a slip agent, an anti-blocking agent, a UV stabilizer, and an anti-foaming agent, in addition to the polyethylene, antioxidant, and neutralizing agent described above. The content of the additives is not particularly limited, and for example, each may be 500 ppm or more, 700 ppm or more, or 1,000 ppm or more, and 2,500 ppm or less, or 1,500 ppm or less, based on the total weight of the polyethylene.

[0194] At this time, the mixing method is not particularly limited, and conventional mixing processes and mixing devices may be used.

[0195] Since the polymerization product obtained after the polymerization reaction for the production of the above-mentioned polyethylene is in powder form, the types of usable antioxidants are limited, and because the antioxidant content varies significantly depending on the powder, there is a large variation in the physical properties of articles manufactured using this. However, when a melting and extrusion process is performed, the components, including the antioxidants, are uniformly mixed, and the resulting articles can possess uniform physical properties.

[0196] 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, slab-shaped, polygonal, and rod-shaped forms. 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.

[0197] The above melt extrusion process can be performed using a conventional extruder, and as long as the morphological conditions of the pellets are satisfied, the specific method and conditions are not particularly limited.

[0198] In addition, the melting and extrusion processes can be performed according to conventional methods. For example, using an extruder such as a twin screw extruder, the process can be performed at an extrusion temperature of 180 to 220 ℃ or 180 to 210 ℃.

[0199] A polyethylene resin composition satisfying the aforementioned physical property conditions is manufactured by the above-described manufacturing method. The manufactured polyethylene resin composition can form a small and uniform crystalline structure upon stretching, and the stretched film can be produced as a stretched film having excellent transparency and surface properties while maintaining high strength characteristics.

[0200] According to another embodiment of the present invention, the invention relates to an unoriented sheet comprising the polyethylene resin composition described above.

[0201] The thickness of the above sheet may be 0.1 to 5 mm, 0.1 to 3 mm, 0.1 to 2 mm, 0.5 to 2 mm, or 0.5 to 1 mm, but can be appropriately adjusted according to the application of the polyethylene resin composition or according to the stretching conditions to be subsequently performed on the above sheet.

[0202] The above-mentioned unoriented sheet may be a cast sheet manufactured by a casting process. For example, it may be manufactured by maintaining the cylinder temperature of a T-die extrusion laminator capable of melt extrusion at 150 to 230 ℃ and the T-die temperature at 200 to 280 ℃ and extruding the molten resin, but is not limited thereto.

[0203] According to another embodiment of the present invention, the invention relates to a stretched film comprising the polyethylene resin composition described above.

[0204] The above-mentioned stretched film comprises a polyethylene resin composition according to the present invention, and may be obtained by stretching a sheet comprising the polyethylene resin composition provided in the present invention.

[0205] The stretched film of the present invention has excellent stretchability along with enhanced transparency and high stiffness. The stretched film described above can satisfy at least two of the following (i) to (vi).

[0206] (i) Density measured according to ASTM D792: 0.940 g / cm³ or greater;

[0207] (ii) When the 10,000x magnification SEM image of the film is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region out of the total area is 5,000 pixels or more;

[0208] (iii) The area ratio of the polymer region where 4.5 ≤ log Mw ≤ 5.5 in the molecular weight distribution curve is 40% or more and 51% or less;

[0209] (iv) SCB content of 2.0 (pieces / 1000C) or more and 6.0 (pieces / 1000C) or less;

[0210] (v) haze measured according to ISO 13468 is 10% or less; and

[0211] (vi) The stiffness in the longitudinal direction (MD) measured according to ASTM D 882 is 900 MPa or more and 1500 MPa or less, and the stiffness in the transverse direction (TD) is 1500 MPa or more and 2500 MPa or less.

[0212] As an example, the above-mentioned stretched film may satisfy all of (i) to (vi).

[0213] The meaning and more preferred range of the above conditions (i) to (vi) overlap with those previously described in the polyethylene resin composition, so they are omitted to avoid excessive complexity in the following specification.

[0214] The stretched film may be a uniaxially stretched or biaxially stretched film. The stretched film may be a sheet that has been uniaxially stretched or biaxially stretched with a stretching ratio of 4 to 8 times in the length (MD) direction or 5 to 10 times in the width (TD) direction.

[0215] As an example, the above-mentioned stretched film may be a sheet that has been biaxially stretched with a stretching ratio of 4 to 8 times in the length (MD) direction and 7 to 10 times in the width (TD) direction.

[0216] As another example, the above-mentioned stretched film may be a sheet that has been biaxially stretched with a stretching ratio of 5 times in the length (MD) direction and 8 times in the width (TD) direction.

[0217] The thickness of the stretched film may be a value measured at 10 to 100 μm, for example, 14 to 95 μm, 20 to 95 μm, or 30 to 90 μm, or 40 to 85 μm.

[0218] However, the above haze and surface modulus are based on the thickness of the stretched film being 25±5㎛.

[0219] The above-mentioned stretched film has high thickness smoothness, and may mean that the average thickness is greater than 14 μm, 15 μm or more, 16 μm or more, 17 μm or more, 18 μm or more, 19 μm or more, or 20 μm or more, and 100 μm or less, and the thickness deviation is 5 μm or less, 4 μm or less, 3 μm or less, or 2.5 μm or less, but is not limited thereto.

[0220] In addition, the above-mentioned stretched film with high thickness smoothness has an average thickness greater than 14 μm, and the smoothness, which is the percentage of the standard deviation of the average thickness value, may be 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, and may be 0.001% or more considering actual process limitations.

[0221] The average thickness and standard deviation of the above-mentioned stretched film may be the average and standard deviation values ​​of thickness measurements taken at 20 or more non-overlapping points of the stretched film (e.g., with dimensions of 210 mm in width and 297 mm in length). The thickness measurement method may be performed using a thickness gauge, but may be measured by other methods known in the art to which the present invention belongs.

[0222] The above-described stretched film may have a Young's Modulus in the MD direction measured according to ASTM D882-07 of 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, or 700 MPa or more, and may be 1000 MPa or less, 950 MPa or less, 900 MPa or less, 800 MPa or less, or 700 MPa or less. Specifically, the Young's Modulus in the MD direction may be 300 MPa or more and 1000 MPa or less, 400 MPa or more and 1000 MPa or less, or 500 MPa or more and 1000 MPa or less, but is not limited thereto.

[0223] The above-mentioned stretched film may have a tensile modulus in the MD direction measured according to ASTM D 882 of 300 MPa or more, 500 MPa or more, 700 MPa or more, 900 MPa or more, 1000 MPa or more, or 1100 MPa or more. However, in terms of simultaneously achieving excellent stretchability and transparency of the final film, it may be 3000 MPa or less, 2500 MPa or less, 2000 MPa or less, 1500 MPa or less, 1400 MPa or less, 1300 MPa or less, or 1200 MPa or less.

[0224] In addition, the stretched film may have a tensile modulus in the TD direction measured according to ASTM D 882 of 300 MPa or more, 500 MPa or more, 700 MPa or more, 900 MPa or more, 1000 MPa or more, 1100 MPa or more, or 1200 MPa or more. However, in terms of simultaneously achieving excellent stretchability and transparency of the final film, it may be 3000 MPa or less, 2500 MPa or less, 2000 MPa or less, 1900 MPa or less, 1800 MPa or less, or 1700 MPa or less.

[0225] The polyethylene stretched film produced in the present invention can be applied as packaging material for various products such as product bags, food bags, food and special packaging, and industrial liners, and can be particularly preferably applied as a printable film.

[0226] The present invention will be explained in detail below through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following examples.

[0227] <Example>

[0228] Preparation of Metallocene Compounds

[0229] Synthesis Example 1: Preparation of Metallocene Compound A1

[0230]

[0231] 1. Synthesis of ligands

[0232] Under Ar, 27.2 g (100 mmol) of 3-(6-tert-butoxyhexyl)-1H-indene and 250 mL of n-hexane were added to a dried 2 L Schlenk flask. After cooling to -78 °C, 42 mL (1.05 eq., 105 mmol) of 2.5 M n-BuLi in hexane was added dropwise. The reaction mixture was slowly heated to room temperature and stirred for 8 hours. After cooling again to -78 °C, 21.3 g (1.5 eq., 150 mmol) of iodomethane was added dropwise. After slowly raising the temperature to room temperature and stirring for 24 hours, the organic layer was separated using water and diethyl ether and dried with MgSO4 to obtain 24.1 g of 3-(6-tert-butoxyhexyl)-1-methyl-1H-indene (84.2 mmol, 84.2% yield).

[0233] 1H NMR (500 MHz, CDCl3): 1.12 (9H, s), 1.29 (3H, d), 1.42 (4H, m), 1.56 (2H, m), 1.70 (2H, m), 2.52 (2H, t), 3.34 (2H, t), 3.42 (1H, m), 6.25 (1H, brs), 7.21 (1H, t), 7.25-7.32 (2H, m), 7.40 (1H, d).

[0234] 2. Synthesis of Metallocene Compounds

[0235] Under Ar, 5.73 g (20 mmol) of the ligand synthesized above and 70 mL of diethyl ether were added to a dried 250 mL Schlenk flask. After cooling to -78 °C, 8.4 mL (1.05 eq., 21 mmol) of 2.5 M n-BuLi in hexane was added dropwise. The reaction mixture was slowly heated to room temperature and stirred for 8 hours. After cooling again to -78 °C, 8.46 g (1.0 eq., 20 mmol) of (1-n-butyl-3-methylcyclopentadienyl)ZrCl3-dimethoxyethane complex was added along with 30 mL of diethyl ether. After slowly heating to room temperature and stirring for 24 hours, the reaction mixture was dried under reduced pressure and dichloromethane was added. The resulting suspension was filtered under Ar to remove LiCl, the filtrate was dried under reduced pressure, and n-hexane was added. The resulting suspension was filtered under Ar to obtain 7.52 g (12.9 mmol, 64.5% yield) of solid metallocene compound A1.

[0236] 1H NMR (500 MHz, CDCl3): 0.77-0.81 (3H, m), 1.09 (9H, s), 1.16-1.28 (6H, m), 1.48-1.56 (6H, m), 1.95 (3H, d), 2.14 (1H, m), 2.42 (4H, m), 2.68 (1H, m), 2.90 (1H, m), 3.23 (2H, t), 4.97 (1H, dt), 5.11 (1H, dt), 5.76 (1H, t), 6.41 (1H, brs), 7.13-7.15 (2H, m), 7.46-7.48 (2H, m).

[0237] Synthesis Example 2: Preparation of Metallocene Compound B1

[0238]

[0239] 1. Synthesis of ligands

[0240] Under Ar, 100 g (450 mmol) of 2-(6-tert-butoxyhexyl)cyclopentadiene, 103 g (2.0 eq., 900 mmol) of 2,4-dimethyl-3-pentanone, and 1 L of ethanol were added to a dried 250 mL Schlenk flask. After cooling to 0 °C, 48.0 g (1.5 eq., 675 mmol) of pyrrolidine was added dropwise. The reaction mixture was slowly heated to room temperature and stirred for 24 hours. After cooling the reaction mixture to 0 °C, 1 L of 10 vol% aq. acetic acid was added and stirred for 30 minutes. The organic layer was separated using water and diethyl ether and dried with MgSO4 to obtain 44.9 g (141 mmol, 31.3% yield) of 2-(6-tert-butoxyhexyl)-5-(2,4-dimethylpentan-3-ylidene)-cyclopenta-1,3-diene.

[0241] Under Ar, 1.66 g (10 mmol) of fluorene and 40 mL of tetrahydrofuran were added to another dry 250 mL Schlenk flask. After cooling to -78 °C, 4.8 mL (1.2 eq., 12 mmol) of 2.5 M n-BuLi in hexane was added dropwise. The reaction mixture was slowly heated to room temperature and stirred for 8 hours. After cooling to -78 °C, 3.19 g (1.0 eq., 10 mmol) of the 2-(6-tert-butoxyhexyl)-5-(2,4-dimethylpentan-3-ylidene)-cyclopenta-1,3-diene synthesized above was added along with 10 mL of tetrahydrofuran. After slowly raising the temperature to room temperature and stirring for 24 hours, the organic layer was separated using water and diethyl ether and dried with MgSO4 to obtain 3.94 g of ligand (8.12 mmol, 81.2% yield).

[0242] 1 H NMR (500 MHz, CDCl3): 0.87 (12H, d), 1.12 (9H, s), 1.34 (2H, m), 1.41 (2H, m), 1.46 (2H, m), 1.55 (4H, m), 2.18 (2H, t), 2.91 (2H, d), 3.36 (2H, t), 3.73 (1H, s), 6.15 (1H, t), 6.25 (1H, brs), 7.25-7.44 (4H, m), 7.55 (2H, dd), 7.90 (2H, dd).

[0243] 2. Synthesis of Metallocene Compounds

[0244] Under Ar, 3.94 g (8.12 mmol) of the ligand synthesized above, 5 mL of methyl t-butyl ether, and 20 mL of toluene were added to a dried 250 mL Schlenk flask. After cooling to -78 °C, 7.1 mL (2.2 eq., 17.8 mmol) of 2.5 M n-BuLi in hexane solution was added dropwise. The reaction mixture was slowly heated to room temperature and stirred for 8 hours. After cooling to -78 °C, 23.06 g (1.0 eq., 8.12 mmol) of ZrCl4(THF) was added along with 5 mL of methyl t-butyl ether. After slowly heating to room temperature and stirring for 24 hours, the reaction mixture was dried under reduced pressure at room temperature to remove the methyl t-butyl ether. The generated toluene suspension was filtered under Ar to remove LiCl, the filtrate was dried under reduced pressure at 50 °C, and n-hexane was added. The generated suspension was filtered under Ar to obtain 2.61 g (4.04 mmol, 49.8% yield) of solid metallocene compound B1.

[0245] 1 H NMR (500 MHz, C6D6): 0.91 (12H, d), 1.13 (9H, s), 1.15-1.38 (6H, m), 1.40-1.55 (6H, m), 3.22 (2H, t), 5.32-6.12 (3H, m), 7.20-7.32 (2H, t), 7.47-7.55 (2H, dd), 7.72 (2H, d), 7.93 (2H, t).

[0246] Preparation of Hybrid Supported Metallocene Catalysts

[0247] Preparation Example 1: Preparation of Hybrid Supported Metallocene Catalyst

[0248] Silica (SP 952, manufactured by Grace Davision) was dehydrated and dried under vacuum at a temperature of 200°C for 12 hours.

[0249] 800 g of dried silica was placed in a 20 L SUS reactor, and 6 kg of methylaluminoxan (MAO) solution (10 wt% in toluene) was added to the toluene solution and reacted slowly at 70 °C for 1 hour with stirring. After the reaction was complete, the unreacted aluminum compound was washed several times with a sufficient amount of toluene until it was completely removed. A solution prepared by dissolving 25.4 g of metallocene compound A1 and 2.8 g of metallocene compound B1 (moles of metallocene compound 1 / moles of metallocene compound 2 = 10) in toluene was sequentially added to the reactor, and the reaction was carried out at 40 °C for 4 hours with stirring. After washing with a sufficient amount of toluene, the mixture was vacuum dried to obtain a hybrid supported metallocene catalyst as a solid powder.

[0250] <Preparation of Polyethylene Resin Composition>

[0251] Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-6

[0252] Polyethylene was produced by a slurry process using a 100L continuous stirred tank reactor (CSTR) and a post reactor in the presence of the hybrid supported catalyst 1 prepared in Catalyst Preparation Example 1 above. Specifically, polymerization was carried out in the reactor in the presence of ethylene, the catalyst, hydrogen, and a comonomer as shown in Table 1 below, under conditions of a polymerization temperature of 80°C or higher. The resulting polymer mixture was then transferred to a post reactor connected in series with the reactor. The temperature inside the post reactor was maintained at 78°C. In the post reactor, unreacted monomers in the transferred polymer mixture were polymerized. The resulting polymerization product was subjected to solvent removal and drying to obtain a polyethylene polymer.

[0253] Based on the total weight of the polymerization product obtained as a result of the polymerization reaction, 200 ppm of BASF’s Irganox 1010 as a primary antioxidant, 400 ppm of BASF’s Irgafos 168 as a secondary antioxidant, and 500 ppm of calcium stearate (Ca-St) or DHT4A as a neutralizing agent were added and mixed, and then extruded at an extrusion temperature of 190 ℃ using a twin screw extruder (TEK 30 MHS, manufactured by SMPLATECH CO., diameter 32 phi, L / D=40) to produce a polyethylene composition in the form of pellets.

[0254] Classification Reactor Ethylene Catalyst Comonomer 1 Comonomer 2 Hydrogen Temperature Pressure [kg / hr][ml / hr][ml / min][ml / min][g / hr][℃][bar] Example 1-1 10706 (1-butene) 6 (1-octene) 13.28 46.8 Example 1-2 10707.1 (1-butene) 7.1 (1-hexene) 15.5 78 6.8 Example 1-3 107016.8 (1-butene) - 14.38 46.8 Example 1-4 10706.75 (1-butene) 6.75 (1-octene) 17.68 26.8 Example 1-5 10708.75 (1-hexene) 8.75 (1-octene) 20.8 80 6.8 Comparative Example 1-1107014.7(1-Butene)-11.2806.8 Comparative Example 1-2107018.8(1-Hexene)-8.2786.8 Comparative Example 1-3107010.1(1-Butene)10.1(1-Hexene)16.1786.8 Comparative Example 1-4107025.1(1-Octene)-18786.8 Comparative Example 1-51070--9846.8 Comparative Example 1-610706.7(1-Butene)6.7(1-Hexene)13.6806.8

[0255]

[0256] Experimental Example 1: Evaluation of Physical Properties of Polyethylene Resin Composition

[0257] The physical properties of the polyethylene resin compositions of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-6 prepared were evaluated in the following manner, and the results are shown in Table 2 below.

[0258] 1. Melt Index (MI 2.16)

[0259] The melt index (MI2.16) was measured according to ASTM D1238 (condition E, 190°C, 2.16kg load).

[0260] 2. Density (g / cm³) 3 )

[0261] Density (g / cm³) according to ASTM D 792 3 ) was measured.

[0262] 3. Ratio of Log Mw (region above 4.5 and below 5.5) based on GPC analysis

[0263] The weight-average molecular weight (Mw) of the polyethylene resin compositions according to the above examples and comparative examples was measured by gel permeation chromatography (GPC). The ratio (%) of the integral value in the region where the Log Mw value was 4.5 or higher and 5.5 or lower to the total integral value was calculated using a log graph of the measured weight-average molecular weight (Mw) of polyethylene, i.e., a GPC curve graph where the x-axis is log Mw and the y-axis is dw / dlogMw. A Waters PL-GPC220 instrument was used for the GPC analysis, and a Polymer Laboratories PLgel MIX-B 300 mm long column was used. The measurement temperature was 160 ℃, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was set to 1 mL / min. Polymer samples according to the examples and comparative examples were each pretreated by dissolving them in trichlorobenzene (1,2,4-Trichlorobenzene) containing 0.0125% butylated hydroxytoluene (BHT) using a GPC analyzer (PL-GP220) at 160 °C for 10 hours, prepared to a concentration of 10 mg / 10 mL, and supplied in an amount of 200 μL. The values ​​of Mw and Mn were derived using a calibration curve formed using a polystyrene standard specimen. Nine types of polystyrene standard specimens with weight-average molecular weights of 2000 g / mol, 10000 g / mol, 30000 g / mol, 70000 g / mol, 200000 g / mol, 700000 g / mol, 2000000 g / mol, 4000000 g / mol, and 10000000 g / mol were used.

[0264] 4. Average number of SCBs

[0265] The average number of SCBs was measured under the following conditions using FT-IR connected to the above GPC device.

[0266] <FT-IR 측정 기기 및 측정 조건>

[0267] Measuring device: PerkinElmer Spectrum 100

[0268] Measured temperature: 160 ℃

[0269] Wavenumber: 2700 cm -1 up to 3000 cm -1

[0270] Number of scans: 8

[0271] Resolution: 8 cm -1

[0272] Detector: DTGS

[0273] Through the above FT-IR analysis, an SCB distribution graph was derived with the log value (log Mw) of the weight-average molecular weight (Mw) (g / mol) on the x-axis and the number of SCBs per 1000 carbons corresponding to the log value on the y-axis, and the average number of SCBs in the entire region was calculated.

[0274] Classification MI 2.16 (g / 10 min) Density (g / cm³) 3 ) Proportion (%) of the region (%) of 4.5≤log Mw≤5.5 Average number of SCBs Example 1-11.32 0.948 44.13.53 Example 1-21.37 0.945 42.74.13 Example 1-31.43 0.941 41.34.81 Example 1-41.38 0.948 50.23.67 Example 1-51.42 0.945 49.15.62 Comparative Example 1-10. 90.95452.81.98Comparative Example 1-21.070.95345.43.12Comparative Example 1-31.470.93839.26.05Comparative Example 1-42.10.93432.19.86Comparative Example 1-51.270.9752.10.1Comparative Example 1-61.20.95238.04.52

[0275] As shown in Table 2 above, the polyethylene resin compositions according to the present invention (Examples 1-1 to 1-5) have a density of 0.940 g / cm³ 3A composition comprising the above high-density polyethylene resin, wherein the melt index (MI 2.16 It was confirmed that the value was 0.50 to 3.00 g / 10 min, the ratio of the integral value of the polymer region with 4.5 ≤ log Mw ≤ 5.5 in GPC analysis was 40% or more and 51% or less, and the SCB content per 1,000 carbons was 2 or more and 6 or less.

[0276] Manufacture of Stretched Film

[0277] Examples 2-1 to 2-5, and Comparative Examples 2-1 to 2-6

[0278] Biaxially stretched films were prepared according to the following conditions using the polyethylene resin compositions of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-6 prepared above. However, with the resin compositions of Comparative Examples 1-1 and 1-5, fracture occurred during the biaxial stretching process and could not be produced into a film.

[0279] - A cast sheet of the above polyethylene was first manufactured using a Bruckner lab extruder line (L / D ratio: 42, Screw diameter: 25 mm, Melt / T-Die temperature: 250 ℃, thickness: 0.72 mm).

[0280] - Biaxial stretching was performed on a polyethylene sheet using a Bruckner pilot line.

[0281] - Sequential biaxial stretching was performed with a stretching ratio of 5 times in the MD direction and 8 times in the TD direction under conditions of Line speed 36 m / min and extrusion rate 130 kg / hr.

[0282] - The final film thickness (based on a stretch ratio of 5x8) was approximately 25㎛.

[0283] Experimental Example 2: Evaluation of the stem region on the film surface

[0284] For the biaxially stretched films of the examples and comparative examples prepared above, the total area of ​​the stem region formed on the film surface was evaluated in the following manner, and the results are shown in Table 3.

[0285] Specifically, the previously manufactured biaxially stretched film was cut to a size of 10 cm x 10 cm in width x height, and images were obtained by observing the surface of 10 random areas at a magnification of 10,000 using a scanning electron microscope (SEM), after which the width x height was fixed to 640 pixels x 440 pixels. To normalize the brightness values ​​in each image, the Histogram Equalization algorithm of a Python program was applied so that the brightness value of the darkest pixel in the image became 0 and the brightness value of the brightest pixel became 255. Next, a binarized image was obtained using the otsu function of the CV2 library, in which the stem area was converted to white (1) and the remaining background was converted to black (0). To remove small stem areas that do not have a high significant correlation with the haze or stiffness of the film, areas within the white (1) enclosed areas included in the binarized image that have a pixel size of 60 or less were converted to black (0). Subsequently, for the preprocessed image, the outline of the white (1) pixel was tracked using Python's FindContours function, and the outline of the white (1) area was repeatedly removed using Python's Skeletonization algorithm while maintaining the main shape of the white (1) area, thereby obtaining the number of pixels included in the centerline when the thickness (short axis) of the white (1) area becomes 1 pixel. Thus, the total area of ​​the stem region in each SEM image was defined as the sum of the number of centerline pixels for each stem region. The average value of the sum of the number of centerline pixels for each stem region in the SEM images obtained from 10 parts of the film is shown in Table 4 below. Note that the results are rounded to the first decimal place.

[0286] Separation Stem Area (Number of Pixels) Example 2-112819 Example 2-210548 Example 2-36608 Example 2-414097 Example 2-57307 Comparative Example 2-21523 Comparative Example 2-34589 Comparative Example 2-4988 Comparative Example 2-63273

[0287] As shown in Table 3 above, it was confirmed that the total area of ​​the stem region of the biaxially stretched films (Examples 2-1 to 2-5) prepared from the polyethylene resin composition according to the present invention was 5,000 pixels or more. However, the films of Comparative Examples 2-2 to 2-4 and 2-6 showed very low values, with the total area of ​​the stem region being less than 5,000 pixels. As mentioned above, in Comparative Examples 2-1 and 2-5, stretched films could not be obtained due to fracture, so the results were not included in the table above.

[0288] Experimental Example 3: Evaluation of Film Properties

[0289] The physical properties of the biaxially stretched films of the examples and comparative examples prepared above were evaluated in the following manner, and the results are shown in Table 4.

[0290] 1. Transparency

[0291] The haze of the biaxially stretched film was measured according to ISO 13468.

[0292] 2. Stiffness

[0293] Specimens were prepared by cutting the manufactured stretched film according to ASTM D 882 standards. After horizontally fixing the specimens in a Zwick tensile testing machine (UTM), the 1% Secant modulus was measured while pulling at a speed of 5 mm / min in the MD direction or TD direction at room temperature (23±5 ℃).

[0294] Classification Haze (%) Stiffness (MPa) MDTD Example 2-1 4.8 138 32263 Example 2-2 4.2 1207 2122 Example 2-3 3.9 103 11637 Example 2-4 5.3 1173 1950 Example 2-5 4.7 107 1761 Comparative Example 2-1 --- Comparative Example 2-2 10.2 142 42263 Comparative Example 2-3 3.1 893 1382 Comparative Example 2-4 2.3 679 1037 Comparative Example 2-5 --- Comparative Example 2-6 13.2 997 1517

[0295] As shown in Table 4 above, all polyethylene resin compositions according to the present invention were stretched into films with a thickness of about 25 μm during the biaxial stretching process, and it was observed that they exhibited excellent stretchability. In addition, the films of Examples 2-1 to 2-5, prepared from the polyethylene resin compositions according to the present invention, showed a haze of 6% or less, a stiffness in the MD direction of 900 MPa or more and 1500 MPa or less, a stiffness in the TD direction of 1500 MPa or more and 2500 MPa or less, and an average value in the MD and TD directions of 1300 MPa or more and 2300 MPa or less. However, the films of Comparative Examples 2-2 and 2-6 showed a haze exceeding 10%, indicating very poor transparency. In addition, the films of Comparative Examples 2-3 and 2-4 showed very low stiffness in the MD direction (less than 900 MPa) and in the TD direction (less than 1382 MPa), indicating a decrease in stiffness.

[0296] Through the above-mentioned experiment, the high density (0.940 g / cm³) according to the present invention 3 Above) It was observed that the polyethylene resin composition not only has excellent stretchability, but the biaxially stretched film produced therefrom also has excellent appearance characteristics (transparency) and simultaneously possesses excellent rigidity characteristics.

[0297] Although the present invention has been described above by limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

1. A polyethylene resin composition comprising an ethylene homopolymer or an ethylene / alpha olefin copolymer having 3 to 20 carbon atoms, wherein The density measured according to ASTM D792 is 0.940 g / cm³ or higher; A polyethylene resin composition having a stem region when a film made of the above polyethylene resin composition is observed at a magnification of 10,000 using a scanning electron microscope (SEM), and having a total area of ​​the stem region of 5,000 pixels or more of the total area when the SEM image is fixed at a size of 640 pixels x 440 pixels.

2. In Paragraph 1, The above density is 0.940 g / cm³ 3 Above 0.970 g / cm³ 3 Polyethylene resin composition, including the above.

3. In Paragraph 1, A polyethylene resin composition having a total area of ​​the stem region of 5,500 pixels or more and 15,000 pixels or less.

4. In Paragraph 1, The above polyethylene resin composition has a melt index (MI) when measured under a load of 2.16 kg at 190 ℃. 2.16 A polyethylene resin composition having ) 0.50 to 3.00 g / 10 min.

5. In Paragraph 1, A polyethylene resin composition having, through gel permeation chromatography (GPC) analysis, a molecular weight distribution curve in which the log value of the weight-average molecular weight (Mw) (log Mw) is on the x-axis and the molecular weight distribution (dw / dlog Mw) for said log value is on the y-axis, wherein the area ratio of the region in which 4.5 ≤ log Mw ≤ 5.5 is 40% or more and 51% or less of the total area.

6. In Paragraph 1, The above polyethylene resin composition is a polyethylene resin composition having a number of short chain branches (SCB) with 2 to 7 carbon atoms per 1,000 carbon atoms of 2.0 or more and 6.0 or less.

7. In Paragraph 1, The film manufactured from the above polyethylene resin composition has a haze of 6% or less, and A polyethylene resin composition having a stiffness in the longitudinal direction (MD) of 900 MPa or more and 1500 MPa or less, and a stiffness in the transverse direction (TD) of 1500 MPa or more and 2500 MPa or less.

8. In Paragraph 1, The above polyethylene resin composition satisfies the conditions of (i) to (vi) below: (i) Density is 0.940 g / cm³ 3 Above 0.970 g / cm³ 3 Below; (ii) In a molecular weight distribution curve obtained through gel permeation chromatography (GPC) analysis, where the log value of the weight-average molecular weight (Mw) (log Mw) is on the x-axis and the molecular weight distribution for said log value (dw / dlog Mw) is on the y-axis, the proportion of the area of ​​the region where 4.5 ≤ log Mw ≤ 5.5 out of the total area is 40% or more and 51% or less; (iii) The polyethylene resin composition has a number of short chain branches (SCB) having 2 to 7 carbon atoms per 1,000 carbon atoms of 2.0 or more and 6.0 or less; Based on a film made of the above polyethylene resin composition, (iv) When the 10,000x magnification SEM image is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region within the total area is 5,500 pixels or more and 15,000 pixels or less; (v) Haze is 6% or less; (vi) The stiffness in the longitudinal direction (MD) is 900 MPa or more and 1500 MPa or less, and the stiffness in the transverse direction (TD) is 1500 MPa or more and 2500 MPa or less.

9. A cast sheet comprising a polyethylene resin composition according to any one of claims 1 to 8.

10. A biaxially stretched film comprising a polyethylene resin composition according to any one of claims 1 to 8.

11. A biaxially stretched film comprising a polyethylene resin composition comprising an ethylene homopolymer or an ethylene / alpha-olefin copolymer having 3 to 20 carbon atoms, satisfying the conditions of (i) to (vi) below: (i) Density is 0.940 g / cm³ 3 That's all; (ii) In a molecular weight distribution curve obtained through gel permeation chromatography (GPC) analysis, where the log value of the weight-average molecular weight (Mw) (log Mw) is on the x-axis and the molecular weight distribution for said log value (dw / dlog Mw) is on the y-axis, the proportion of the area of ​​the region where 4.5 ≤ log Mw ≤ 5.5 out of the total area is 40% or more and 51% or less; (iii) The number of short chain branches (SCBs) with 2 to 7 carbon atoms per 1,000 carbon atoms is 2.0 or more and 6.0 or less; (iv) When the 10,000x magnification SEM image is fixed at 640 pixels x 440 pixels, the total area of ​​the stem region within the total area is 5,000 pixels or more; (v) Haze is 6% or less; (vi) The stiffness in the longitudinal direction (MD) is 900 MPa or more and 1500 MPa or less, and the stiffness in the transverse direction (TD) is 1500 MPa or more and 2500 MPa or less.

12. In Paragraph 11, The above film is a biaxially stretched film having an average stiffness in the length direction (MD) and stiffness in the width direction (TD) of 1300 MPa or more and 2300 MPa or less.

13. In Paragraph 11, A biaxially stretched film having a thickness of 10 to 100 μm.

Images