Polyethylene resin composition, method for producing the same, and molded article containing the same

Abstract

A polyethylene resin composition, a method for producing the same, and a molded article containing the same are provided. The polyethylene resin composition contains a polyethylene resin formed by sequentially using a first reactor and a second reactor. The zero-shear viscosity (η01) of the polyethylene resin formed in the first reactor at 180 °C is from 10 6 Poise to 10 8 Poise, and the number of short-chain branches per 1000 carbons (SCB1) by 13 C-NMR is from 5.0 to 20. The ratio of the zero-shear viscosity of the polyethylene resin formed in the first reactor to that of the polyethylene resin formed in the second reactor at 180 °C (η01 / η02) is from 10 to 100. The ratio of the number of short-chain branches per 1000 carbons (SCB1 / SCB2) by 13 C-NMR is from 2 to 20, and the density difference (D2-D1) is from 0.01 g / cm 3 to 0.05 g / cm 3 .

Description

Technical Field

[0001] The embodiments relate to a polyethylene resin composition, a method for manufacturing the same, and a molded article including the same. Background Art

[0002] In recent years, as regulations on recycling have become increasingly strict around the world, and as companies' own social responsibilities regarding the sustainability and awareness of solving widespread environmental problems have changed, flexible packaging materials are required to be designed to be suitable for collection, sorting, and recycling. As the most effective way to solve the above problems, by using a single material as the packaging material that has previously been used in combination with various materials, especially by applying a packaging material to which a single material of polyethylene (PE) or polypropylene (PP) has been applied, recycling can be easily carried out, and it helps to improve the quality of recycled products.

[0003] However, in the case of applying a polyethylene film typically manufactured by a blown film or cast film process to a single material and simply replacing a base film such as an existing polyethylene terephthalate (PET) film or polyamide (PA) film, the problem is that the mechanical and physical properties of the polyethylene film are degraded. For this reason, it is necessary to apply a biaxially oriented polyethylene (BOPE) film. In the process of manufacturing a biaxially oriented polyethylene (BOPE) film, when the film is stretched in the longitudinal and transverse directions, the polyethylene chains and crystal structure are highly oriented, so that better mechanical strength is obtained, especially the impact strength is improved, and optical properties such as transparency and film appearance are significantly improved.

[0004] A method for manufacturing a biaxially stretched film includes a tenter process and a tubular stretching method. The tenter process has been used to process general biaxially stretched films such as polypropylene (PP), polyethylene terephthalate, and polyamide. When compared with the tubular stretching method, the tenter process has the advantages of higher elongation rate, faster molding speed, and higher production efficiency. Moreover, the biaxially stretched film manufactured thereby has good thickness uniformity as well as excellent mechanical and physical properties and optical properties.

[0005] However, in the case of the tenter process, film processing is greatly affected by the molecular structure of the raw material, and the stretching process conditions are very demanding. In particular, typical polyethylene has a fast crystallization rate and a high degree of crystallinity, and thus has a narrow stretchable temperature range and an extremely low elongation rate, and when wrinkles or thickness non-uniformity are formed during stretching, the film will eventually tear during stretching. Therefore, it is necessary to develop a raw material for a polyethylene resin composition suitable for the tenter process for manufacturing a BOPE film having a high elongation rate. Summary of the Invention

[0006] One aspect of the present invention provides a polyethylene resin composition that can be sequentially biaxially stretched up to 6 times in the machine direction (MD) and up to 10 times in the transverse direction (TD) using a tenter process, has excellent processability during stretching, and has a wide stretchable temperature range.

[0007] Another aspect of the present invention provides a method for manufacturing the polyethylene resin composition.

[0008] Another aspect of the present invention provides a molded article comprising the polyethylene resin composition.

[0009] According to at least one of the embodiments, a polyethylene resin composition comprises a polyethylene resin formed sequentially using a first reactor and a second reactor, wherein the polyethylene resin formed in the first reactor has a zero-shear viscosity (η01) of 10 6 Poise to 10 8 Poise at 180 °C as measured by an ARES rheometer, and the number of short-chain branches per 1000 carbons (SCB1) determined by 13 C-NMR is 5.0 to 20, and the ratio of the zero-shear viscosity of the polyethylene resin formed in the first reactor to that of the polyethylene resin formed in the second reactor (η01 / η02) at 180 °C as measured by an ARES rheometer is 10 to 100, the ratio of the number of short-chain branches per 1000 carbons (SCB1 / SCB2) determined by 13 C-NMR is 2 to 20, and the density difference (D2 - D1) is 0.01 g / cm 3 to 0.05 g / cm 3 .

[0010] The density (D1) of the polyethylene resin formed in the first reactor may be 0.915 g / cm 3 to 0.935 g / cm 3 , and the density (D2) of the polyethylene resin formed in the second reactor is 0.945 g / cm 3 to 0.965 g / cm 3 .

[0011] When forming the polyethylene resin in the first reactor, the comonomer may be supplied at a feed ratio of 10 to 150 g / kg relative to C2.

[0012] When forming the polyethylene resin in the first reactor, H2 may be supplied at a feed ratio of 10 to 100 mg / kg relative to C2.

[0013] The melting temperature (Tm) of the polyethylene resin formed in the first reactor may be from 110°C to 126°C, and the difference (Tm - Tc) between the melting temperature (Tm) and the crystallization temperature (Tc) may be from 10°C to 15°C.

[0014] When forming the polyethylene resin in the second reactor, H2 may be supplied at a supply ratio of 0.4 to 0.7 mol% / wt% relative to C2.

[0015] The zero-shear viscosity (η02) of the polyethylene resin formed in the second reactor at 180°C by an ARES rheometer may be from 9.0×10 4 poise to 7.0×10 5 poise.

[0016] The polyethylene resin formed in the second reactor passes through 13 The number of short chain branches per 1000 carbons (SCB2) by C-NMR may be from 1.0 to 5.0.

[0017] The weight ratio of the polyethylene resin formed in the first reactor to the polyethylene resin formed in the second reactor may be (45 to 55):(55 to 45).

[0018] The density of the polyethylene resin composition may be from 0.945 g / cm 3 to 0.970 g / cm 3 .

[0019] The melt flow index (also referred to as "melt index" or "melt index") of the polyethylene resin composition may be from 0.4 g / 10 min to 3.0 g / 10 min at 190°C under a load condition of 2.16 kg, and may be from 2.0 g / 10 min to 10 g / 10 min at 190°C under a load condition of 5 kg.

[0020] According to another embodiment, a method for manufacturing a polyethylene resin composition includes sequentially using a first reactor and a second reactor to prepare a polyethylene resin, wherein the zero-shear viscosity (η01) of the polyethylene resin formed in the first reactor at 180°C by an ARES rheometer is from 10 6 poise to 10 8 poise, and the number of short chain branches per 1000 carbons (SCB1) by 13 C-NMR is from 5.0 to 20, and the ratio (η01 / η02) of the zero-shear viscosity of the polyethylene resin formed in the first reactor to the zero-shear viscosity of the polyethylene resin formed in the second reactor at 180°C by an ARES rheometer is from 10 to 100, and by13 The ratio of the number of short chain branches per 1000 carbons (SCB1 / SCB2) of the C-NMR is from 2 to 20, and the density difference (D2 - D1) is 0.01 g / cm 3 to 0.05 g / cm 3 .

[0021] According to another embodiment, a molded article comprises the polyethylene resin composition.

[0022] The molded article may be a film that is successively biaxially stretched to a longitudinal (MD) elongation ratio of 4 to 6 times and a transverse (TD) elongation ratio of 8 to 10 times by a tenter frame process.

[0023] Advantageous effects

[0024] The polyethylene resin composition according to an embodiment of the present invention can be successively biaxially stretched by a tenter frame process at a longitudinal (MD) elongation ratio of up to 6 times and a transverse (TD) elongation ratio of up to 10 times, has excellent processability during stretching, and has a wide stretchable temperature range, thereby having excellent tensile properties. Accordingly, a final film having improved transparency and high mechanical strength can be ensured. Detailed description

[0025] Hereinafter, embodiments will be described in detail to enable those skilled in the art to easily implement them. However, these embodiments can be embodied in many different forms, and the present invention is not limited to the embodiments described herein.

[0026] The polyethylene resin composition according to an embodiment of the present invention comprises a polyethylene resin. The polyethylene resin can be formed by polymerization using a two-stage reactor composed of a first reactor and a second reactor connected to each other. Specifically, the polyethylene resin is initially formed by polymerization in the first reactor, and the polyethylene resin obtained at this time is transferred to the second reactor and polymerized therein to obtain the polyethylene resin secondly. The first reactor and the second reactor may be a slurry process.

[0027] The polyethylene resin formed in the first reactor may be a low-density polyethylene resin having a density lower than that of the polyethylene resin formed in the second reactor, and the polyethylene resin formed in the second reactor may be a high-density polyethylene resin having a density higher than that of the polyethylene resin formed in the first reactor.

[0028] Specifically, the density (D1) of the polyethylene resin formed in the first reactor may be 0.915 g / cm 3 to 0.935 g / cm 3 , and may be, for example, 0.920 g / cm 3 to 0.935 g / cm3 When the density of the polyethylene resin formed in the first reactor is within the above range, the final film can be stably biaxially stretched successively in the longitudinal and transverse directions, and the draw ratio can be improved.

[0029] In addition, the density (D2) of the polyethylene resin formed in the second reactor can be from 0.945 g / cm 3 to 0.935 g / cm 3 , and can be, for example, from 0.945 g / cm 3 to 0.935 g / cm 3 . When the density of the polyethylene resin formed in the second reactor is within the above range, the modulus of the stretched film is excellent, and the thermal stability is improved.

[0030] The zero-shear viscosity (η01) of the polyethylene resin formed in the first reactor at 180 °C by an ARES rheometer can be from 10 6 Poise to 10 8 Poise, and can be, for example, from 10 6 Poise to 10 7 Poise. When the polyethylene resin formed in the first reactor has a zero-shear viscosity within the above range, the mechanical strength of the finally formed polyethylene resin can be improved.

[0031] The number of short-chain branches per 1000 carbons (SCB1) of the polyethylene resin formed in the first reactor by 13 C-NMR can be from 5 to 20, and can be, for example, from 5 to 15. When the polyethylene resin formed in the first reactor has a number of short-chain branches within the above range, during the process of successively biaxially stretching the final film using a tenter frame process, the elongation in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0032] When forming the polyethylene resin in the first reactor, a comonomer can be supplied and polymerized together. The comonomer can be 1-butene, 1-hexene, 1-octene, etc., but is not limited thereto. The comonomer can be supplied to the first reactor at a supply ratio of 10 to 150 g / kg relative to C2, and can be supplied, for example, at a supply ratio of 30 to 100 g / kg. When the comonomer is supplied to the first reactor at a supply ratio within the above range, there is no risk of reactor blockage and fouling formation, and during the process of biaxially stretching the final film, the elongation in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0033] In addition, when forming a polyethylene resin in the first reactor, H2 can be supplied and polymerized together. H2 can be supplied to the first reactor at a supply ratio of 10 to 100 mg / kg relative to C2, and can be supplied, for example, at a supply ratio of 20 to 60 mg / kg. When H2 is supplied to the first reactor at a supply ratio within the above range, there is no risk of reactor blockage and fouling formation, and during the biaxial stretching of the final film, the elongation rate in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0034] The melting temperature (Tm) of the polyethylene resin formed in the first reactor can be 110°C to 126°C, and can be, for example, 120°C to 126°C. When the melting temperature of the polyethylene resin formed in the first reactor is within the above range, the stretching performance can be improved during the biaxial stretching of the final film.

[0035] In addition, the difference (Tm - Tc) between the melting temperature (Tm) and the crystallization temperature (Tc) of the polyethylene resin formed in the first reactor can be 10°C to 15°C, and can be, for example, 10°C to 12°C. When the difference between the melting temperature and the crystallization temperature of the polyethylene resin formed in the first reactor is within the above range, the stretchable temperature range of the final film can be widened.

[0036] The high load melt flow index (HLMI) (21.6 kg load, 190°C) of the polyethylene resin formed in the first reactor can be 0.1 to less than 10, and can be, for example, 1.0 to 8.0. When the melt flow index of the polyethylene resin formed in the first reactor is within the above range, the mechanical strength of the finally formed polyethylene resin can be improved.

[0037] The zero shear viscosity (η02) of the polyethylene resin formed in the second reactor at 180°C by an ARES rheometer can be 9.0×10 4 poise to 7.0×10 5 poise, and can be, for example, 9.0×10 4 poise to 5.0×10 5 poise. When the polyethylene resin formed in the second reactor has a zero shear viscosity within the above range, the mechanical strength of the finally formed polyethylene resin can be improved.

[0038] The polyethylene resin formed in the second reactor passes through 13The number of short chain branches per 1000 carbons (SCB2) of the C-NMR can be from 1.0 to 5.0, and can be, for example, from 2.0 to 4.0. When the polyethylene resin formed in the second reactor has a number of short chain branches within the above range, during the process of biaxially stretching the final film successively using a tenter frame process, the elongation rates in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0039] When forming the polyethylene resin in the second reactor, a comonomer can be supplied and polymerized together. The comonomer can be 1-butene, 1-hexene, 1-octene, etc., but is not limited thereto. The comonomer can be supplied to the second reactor at a supply ratio of 0 to 30 g / kg relative to C2, and can be supplied, for example, at a supply ratio of 0 to 20 g / kg or 1 to 20 g / kg. When the comonomer is supplied to the second reactor at a supply ratio within the above range, there is no risk of reactor blockage and fouling formation, and during the process of biaxially stretching the final film, the elongation rates in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0040] In addition, when forming the polyethylene resin in the second reactor, H2 can be supplied and polymerized together. H2 can be supplied to the second reactor at a supply ratio of 0.4 to 0.7 mol% / wt% relative to C2, and can be supplied, for example, at a supply ratio of 0.45 to 0.65 mol% / wt%. When H2 is supplied to the second reactor at a supply ratio within the above range, there is no risk of reactor blockage and fouling formation, and during the process of biaxially stretching the final film, the elongation rates in the longitudinal and transverse directions can be increased, and a final film with high mechanical strength can be obtained.

[0041] The melt flow index (5 kg load, 190 °C) of the polyethylene resin formed in the second reactor can be from 2 to 10, and can be, for example, from 2.5 to 8.5. When the melt flow index of the polyethylene resin formed in the second reactor is within the above range, stable film extrusion processing performance can be ensured, and the mechanical and physical properties of the final film can be improved.

[0042] The ratio (η01 / η02) of the zero shear viscosity of the polyethylene resin formed in the first reactor to that of the polyethylene resin formed in the second reactor measured by an ARES rheometer at 180 °C can be from 10 to 100, and can be, for example, from 10 to 30. When the ratio of the zero shear viscosities of the polyethylene resin formed in the first reactor to that formed in the second reactor is within the above range, the modulus of the final film can be increased, and the transparency of the film can be improved due to the reduction of the surface roughness caused by the pressure load during film extrusion.

[0043] In addition, the ratio (SCB1 / SCB2) of the number of short chain branches per 1000 carbons of the polyethylene resin formed in the first reactor to that of the polyethylene resin formed in the second reactor, as determined by 13 13C-NMR, may be from 2 to 20, and may be, for example, from 2 to 10. When the ratio of the number of short chain branches of the polyethylene resin formed in the first reactor to that of the polyethylene resin formed in the second reactor is within the above range, during the biaxial stretching of the final film, the elongation rates in the longitudinal and transverse directions can be increased, and excellent mechanical strength can be ensured.

[0044] In addition, the density difference (D2 - D1) between the polyethylene resin formed in the first reactor and the polyethylene resin formed in the second reactor may be from 0.01 g / cm 3 to 0.05 g / cm 3 and may be, for example, from 0.015 g / cm 3 to 0.03 g / cm 3 . When the density difference between the polyethylene resin formed in the first reactor and the polyethylene resin formed in the second reactor is within the above range, during the biaxial stretching of the final film, the elongation rates in the longitudinal and transverse directions can be increased, and excellent mechanical strength can be ensured.

[0045] The weight ratio of the polyethylene resin formed in the first reactor to the polyethylene resin formed in the second reactor may be (45 to 55):(55 to 45), and may be, for example, (47 to 52):(53 to 48). When the weight ratio of the polyethylene resin formed in the first reactor to the polyethylene resin formed in the second reactor is within the above range, the production efficiency can be improved, the elongation rates in the longitudinal and transverse directions can be increased during the biaxial stretching of the final film, and film tearing can be prevented.

[0046] A polyethylene resin composition comprising the final polyethylene resin formed by the above method, i.e., a polyethylene resin formed to have a zero shear viscosity (η01), number of short chain branches (SCB1), zero shear viscosity ratio (η01 / η02), ratio of the number of short chain branches (SCB1 / SCB2), and density difference (D2 - D1) within the respective predetermined ranges, can be biaxially stretched successively by a tenter frame process at a longitudinal (MD) elongation rate of up to 6 times and a transverse (TD) elongation rate of up to 10 times, has excellent processability during stretching, and has a wide stretchable temperature range, and thus can have excellent tensile properties.

[0047] The density of the polyethylene resin composition according to one embodiment may be from 0.945 g / cm 3 to 0.970 g / cm 3, and can be, for example, 0.945 g / cm 3 to 0.965 g / cm 3 . When the density of the polyethylene resin composition is within the above range, the thermal stability of the final film can be excellent, the modulus can be increased, and the transparency can be improved.

[0048] The melt flow index of the polyethylene resin composition can be 0.40 g / 10 min to 3.0 g / 10 min under a load of 2.16 kg at 190 °C, and can be, for example, 0.49 g / 10 min to 2.3 g / 10 min. In addition, the melt flow index of the polyethylene resin composition can be 2.0 g / 10 min to 10 g / 10 min under a load of 5 kg at 190 °C, and can be, for example, 2.5 g / 10 min to 8.5 g / 10 min. When the melt flow index of the polyethylene resin composition is within the above range, the extrusion processability can be excellent, and the deterioration of physical properties due to small molecules can be prevented.

[0049] In addition to the polyethylene resin, the polyethylene resin composition according to an embodiment of the present invention may further contain additives, and the additives include antioxidants, neutralizers, or a combination thereof.

[0050] Based on 100 parts by weight of the polyethylene resin composition, the amount of the additives contained can be 0.005 parts by weight to 0.5 parts by weight.

[0051] The antioxidant may include phenolic compounds, phosphorus-based compounds, or a combination thereof. The phenolic compound may be pentaerythritol tetrakis(3-(3,5-ditert-butyl-4-hydroxyphenyl)propionate), octadecyl 3-(3,5-ditert-butyl-4-hydroxyphenyl)propionate, tris(3,4-ditert-butyl-4-hydroxybenzyl) isocyanurate, triethylene glycol bis(3-(tert-butyl-4-hydroxy-5-methylphenyl)propionate), etc., and the phosphorus-based compound may be tris(2,4-ditert-butylphenyl) phosphite, tetrakis(2,4-ditertiarybutylphenyl)-4,4-diphenyl diphosphonite, distearyl pentaerythritol diphosphite, 2,4-dinonylphenyl diphosphite bis(4-monononylphenyl), etc.

[0052] Based on 100 parts by weight of the polyethylene resin composition, the amount of the antioxidant contained can be 0.01 parts by weight to 0.5 parts by weight, for example, 0.1 parts by weight to 0.3 parts by weight. When the antioxidant contained is within the above content range, excellent processability can be obtained without discoloration or viscosity change.

[0053] The neutralizing agent may include calcium stearate, zinc stearate, magnesium aluminum hydroxycarbonate (or called basic magnesium aluminum carbonate or magnesium aluminum hydroxide carbonate), zinc oxide, magnesium hydroxy stearate, or a combination thereof.

[0054] Based on 100 parts by weight of the polyethylene resin composition, the amount of the neutralizing agent included may be 0.005 parts by weight to 0.3 parts by weight, for example, 0.02 parts by weight to 0.1 parts by weight. When the neutralizing agent included is within the above content range, excellent processing performance can be obtained without color change or viscosity change.

[0055] Hereinafter, a method for manufacturing the above polyethylene resin composition according to another embodiment will be described.

[0056] The method for manufacturing the above polyethylene resin composition includes sequentially using a first reactor and a second reactor to prepare the polyethylene resin.

[0057] Specifically, a polyethylene resin having a relatively high molecular weight and a relatively low density can be prepared by polymerization in the first reactor, and then the polyethylene resin can be transferred to the second reactor and polymerized to prepare a polyethylene resin having a relatively low molecular weight and a relatively high density.

[0058] The polymerization in the first reactor and the second reactor can be carried out under a Ziegler-Natta catalyst. The Ziegler-Natta catalyst is a catalyst generally known as the Ziegler-Natta catalyst and uses a transition metal compound belonging to Group IV, Group V, or Group VI of the periodic table as the main catalyst. The most commonly used Ziegler-Natta catalyst is a halogenated complex composed of magnesium and titanium or magnesium and vanadium.

[0059] In addition, during the polymerization in the first reactor and the second reactor, a comonomer can be introduced therein. The comonomer may be a C3 to C20 (for example, C4 to C8 or C6 to C8) α-olefin.

[0060] The polymerization in the first reactor can be carried out under the conditions of a pressure of 40 MPa to 50 MPa, a temperature of 70 °C to 100 °C, and a residence time of 40 minutes to 70 minutes, and can be carried out, for example, under the conditions of a pressure of 42 MPa to 48 MPa, a temperature of 80 °C to 95 °C, and a residence time of 50 minutes to 65 minutes.

[0061] In addition, the polymerization in the second reactor can be carried out under the conditions of a pressure of 40 MPa to 50 MPa, a temperature of 80 °C to 110 °C, and a residence time of 20 minutes to 50 minutes, and can be carried out, for example, under the conditions of a pressure of 42 MPa to 48 MPa, a temperature of 90 °C to 100 °C, and a residence time of 25 minutes to 40 minutes.

[0062] The description of the density (D1), zero-shear viscosity (η01), number of short-chain branches (SCB1), supply ratio of comonomer relative to C2, supply ratio of H2 relative to C2, melting temperature (Tm), difference between melting temperature (Tm) and crystallization temperature (Tc) (Tm - Tc), high-load melt flow index, etc. of the polyethylene resin formed in the first reactor is the same as above, and the description of the density (D2), zero-shear viscosity (η02), number of short-chain branches (SCB2), supply ratio of comonomer relative to C2, supply ratio of H2 relative to C2, melt flow index, etc. of the polyethylene resin formed in the second reactor is the same as those above. In addition, the ratio of zero-shear viscosities (η01 / η02), ratio of number of short-chain branches (SCB1 / SCB2), density difference (D2 - D1), weight ratio, etc. of the polyethylene resin formed in the first reactor and the polyethylene resin formed in the second reactor are also the same as those above.

[0063] According to another embodiment of the present invention, a molded article made of the above polyethylene resin is provided.

[0064] The molded article can be a film that is sequentially biaxially stretched to a longitudinal (MD) elongation ratio of 4 to 6 times and a transverse (TD) elongation ratio of 8 to 10 times by a tenter frame process.

[0065] Hereinafter, specific embodiments of the present invention will be presented. However, the embodiments described below are only for specifically exemplifying or describing the present invention, and the present invention should not be limited thereby. In addition, those skilled in the art can fully infer technically what is not described herein, and thus the description thereof will be omitted.

[0066] <Manufacturing a polyethylene resin composition>

[0067] Example 1

[0068] Two reactors (each reactor having a capacity of 90 liters) are connected in series to carry out ethylene polymerization using a Ziegler-Natta catalyst and a comonomer. As a known catalyst composed of magnesium and titanium, a Ziegler-Natta catalyst prepared by a typical method is used.

[0069] Specifically, the polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 51:49. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 90 g / kg relative to C2, and H2 is supplied at a supply ratio of 31 mg / kg relative to C2. In addition, during the polymerization of the polyethylene resin in the second reactor, 1-hexene is supplied as a comonomer at a supply ratio of 10 g / kg relative to C2, and H2 is supplied at a supply ratio of 0.52 mol% / wt% relative to C2. The polymerization in the first reactor is carried out under the conditions of a temperature of 80 °C, a pressure of 45 kgf / cm 2 and a residence time of 61 minutes, and the polymerization in the second reactor is carried out under the conditions of a temperature of 94 °C, a pressure of 45 kgf / cm 2 and a residence time of 34 minutes. The process conditions in each of the first and second reactors and the physical properties of each formed polyethylene resin are shown in Table 1 below.

[0070] Together with 100 parts by weight of the obtained powdered polyethylene resin, 0.1 part by weight of Irganox-1076 and 0.1 part by weight of Irgafos-168 as antioxidants and 0.025 part by weight of basic magnesium carbonate hydroxide (DHT-4A) as a neutralizing agent are mixed using a Henschel mixer and then mixed using a twin-screw extruder to obtain a polyethylene resin composition in the form of pellets.

[0071] Example 2

[0072] A polyethylene resin composition is prepared in the same manner as in Example 1 according to the composition in Table 1 below.

[0073] The polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 47:53. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 68 g / kg relative to C2, and H2 is supplied at a supply ratio of 38 mg / kg relative to C2, and no comonomer is supplied during the polymerization of the polyethylene resin in the second reactor.

[0074] Example 3

[0075] A polyethylene resin composition is prepared in the same manner as in Example 1 according to the composition in Table 1 below.

[0076] The polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 49:51. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 40 g / kg relative to C2, and H2 is supplied at a supply ratio of 55 mg / kg relative to C2, and during the polymerization of the polyethylene resin in the second reactor, no comonomer is supplied.

[0077] Comparative Example 1

[0078] A polyethylene resin composition was prepared in the same manner as in Example 1 according to the composition in Table 1 below.

[0079] The polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 50:50. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 17 g / kg relative to C2, and H2 is supplied at a supply ratio of 210 mg / kg relative to C2, and during the polymerization of the polyethylene resin in the second reactor, 1-hexene is supplied as a comonomer at a supply ratio of 33 g / kg relative to C2.

[0080] Comparative Example 2

[0081] A polyethylene resin composition was prepared in the same manner as in Example 1 according to the composition in Table 1 below.

[0082] The polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 50:50. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 90 g / kg relative to C2, and H2 is supplied at a supply ratio of 120 mg / kg relative to C2, and during the polymerization of the polyethylene resin in the second reactor, no comonomer is supplied.

[0083] Comparative Example 3

[0084] A polyethylene resin composition was prepared in the same manner as in Example 1 according to the composition in Table 1 below.

[0085] The polymer in the slurry phase polymerized in the first reactor is transferred to the second reactor for continuous polymerization, and the ratio of the polymerization amounts in each reactor is set to a weight ratio of 50:50. At this time, in the first reactor, 1-hexene is supplied as a comonomer at a supply ratio of 13 g / kg relative to C2, and H2 is supplied at a supply ratio of 48 mg / kg relative to C2, and during the polymerization of the polyethylene resin in the second reactor, no comonomer is supplied.

[0086] Evaluation 1: Measurement of Physical Properties of Polyethylene Resin Composition

[0087] The physical properties of the polyethylene resin compositions produced in each of Examples 1 to 3 and Comparative Examples 1 to 3 were measured, and the results are shown in Table 1 below.

[0088] Melt Flow Index (MI)

[0089] Measurements were carried out according to ASTM D1238 at 190 °C under loads of 2.16 kg, 5 kg, and 21.6 kg, respectively.

[0090] The melt flow index measured at a load of 2.16 kg is denoted as MI2, the melt flow index measured at a load of 5 kg is denoted as MI5, and the melt flow index measured at a load of 21.6 kg is denoted as HLMI.

[0091] Density

[0092] Measurements were carried out according to ASTM D1505.

[0093] Zero Shear Viscosity

[0094] Using an Advanced Rheology Expansion System (ARES) rheometer, measurements were carried out under the conditions of a frequency sweep at 180 °C, a strain of 5%, and 0.01 to 400 rad / s, and then the zero-shear viscosity was calculated using the Carreau model.

[0095] Number of Short Chain Branches per 1000 Carbons (SCB)

[0096] Using quantitative nuclear magnetic resonance (NMR) spectroscopy, the number of short chain branches per 1000 carbons of the polyethylene resin was calculated. A Bruker 600 MHz NMR spectrometer was used, and for 1310 mm multi - nuclear high - temperature CryoProbe optimized for ¹³C - NMR. Approximately 2 g of the sample was dissolved in 2.8 ml of a mixed solvent in which 1,2 - dichlorobenzene and benzene - d6 were mixed at a ratio of 4:1 at 150 °C, and measurements were carried out under the experimental conditions of 5000 scans, D1 of 12 s, a pulse width of 90°, a measurement temperature of 130 °C, and proton - decoupling mode.

[0097] The molar % content of the polyethylene resin was calculated by calculating the integral ratio of the characteristic signals (38.2 ppm, 34.6 ppm, and 34.2 ppm) of 1 - hexene monomers by using specific comonomers. 13 Quantitative calculation of ¹³C - NMR spectra, where the chemical shift of the main - chain methylene (-(CH₂)-) at 30 ppm is not affected by other comonomer sequences. n Using this, the number of short - chain branches (SCB) per 1000 carbons was calculated by the following equations 1 to 4.

[0098]

[0099] [Equation 1]

[0100] The number of moles of hexene - 1 (H’) = (H1 + H2) / 2

[0101] (In the above Equation 1,

[0102] H1 is A, where A is the integral value at 38.1 ppm, and

[0103] H2 is (B + C) / 3, where B is the integral value at 34.6 ppm, and C is the integral value at 34.2 ppm.)

[0104] [Equation 2]

[0105] The number of moles of ethylene (E’) = [{(D + E)-E} / 2]+H’

[0106] (In the above Equation 2,

[0107] D + E is the integral value from 33.9 ppm to 27.3 ppm, where E is the integral value at 27.3 ppm.)

[0108] [Equation 3]

[0109] The molar % of hexene - 1 = H’ / (H’ + E’)×100

[0110] [Equation 4]

[0111] The number of short - chain branches per 1000 carbons (SCB) = H’ / (E’×2 + H’×6)×1000

[0112] Melting Temperature and Crystallization Temperature ​

[0113] Measurement was carried out using a differential scanning calorimeter (DSC) according to ASTM D 3418 at a heating rate of 10 °C / min.

[0114] [Table 1]

[0115]

[0116] Evaluation 2: Evaluation of Biaxial Tensile Properties

[0117] To evaluate the biaxial stretching properties of the polyethylene resin compositions produced in each of Examples 1 to 3 and Comparative Examples 1 to 3, a film sheet with a width of 300 mm and a thickness of 800 μm was prepared at a temperature of 220 °C by OCS in a PE30-CR9 casting molding machine. Square specimens with dimensions of 80 mm × 80 mm were cut from the middle of the extruded sheet, and a Bruckner Karo V biaxial stretcher was used for biaxial stretching at a stretching rate of 100% / s based on the original specimen. The preheating time before stretching was fixed at 120 seconds, and stretching was performed simultaneously or sequentially in two directions. In simultaneous biaxial stretching, the specimen was stretched at a stretching ratio of 8 × 8 in two directions. In sequential biaxial stretching, the specimen was first stretched longitudinally (MD) up to 6 times, and then transversely (TD) up to 9 times.

[0118] This is shown in Table 2 below, and the cases where stretching was possible are indicated as O, while the cases where stretching was not possible are indicated as X.

[0119] [Table 2]

[0120]

[0121] From Table 2 above, it was confirmed that when using the polyethylene resin compositions of each of Examples 1 to 3 according to one embodiment, sequential stretching up to 6 times longitudinally and up to 9 times transversely was easily achieved. It was also confirmed that the stretching process could be carried out within a wide temperature range with a stretchable temperature range between 118 °C and 125 °C.

[0122] Evaluation 3: Measurement of Physical Properties of Sheet for Biaxially Stretched Film

[0123] The physical properties of the film sheets of each of Examples 1 to 3 prepared as above were measured in the following manner, and the results are shown in Table 3 below.

[0124] Haze

[0125] Measurement was carried out according to ASTM D 1003.

[0126] Glossiness

[0127] Measure according to ASTM D 2457.

[0128] Dart Impact Strength

[0129] Measure according to ASTM D 1709.

[0130] Puncture Test

[0131] Measure according to ASTM D 5748.

[0132] Tensile Strength, Elongation and Modulus

[0133] All are measured according to ASTM D 882.

[0134] [Table 3]

[0135] Example 1 Example 2 Example 3 Tensile Ratio 6×9 6×9 6×9 Sheet Thickness (μm) 800 800 800 Average Thickness (μm) 15 15 15 Haze (%) 4.3 6.1 6.6 Glossiness (45°) (%) 79 69 72 Drop Impact Strength (g) 520 430 390 Puncture Load (N) 36 35 35 Puncture Energy (kgf-mm) 206 177 182 <![CDATA[1% secant MD modulus (kg / cm 2 )]]> 11112 11575 13031 <![CDATA[1% secant TD modulus (kg / cm 2 )]]> 14398 17698 17135 <![CDATA[MD Tensile Strength (kg / cm 2 )]]> 906 1008 1055 MD Elongation (%) 121 121 108 <![CDATA[Tensile strength (kg / cm 2 )]]> 1597 1831 1733 TD Elongation (%) 39 33 35

[0136] From the above Table 3, it can be confirmed that in the case of using a film which is biaxially stretched 6 times longitudinally and 9 times in the transverse direction in order, of each of Examples 1 to 3 according to an embodiment, the transparency is excellent, and mechanical strengths such as impact strength, modulus and tensile strength are also excellent.

[0137] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims and the detailed description of the invention. It is obvious that these modifications also fall within the scope of the present invention.

Claims

1. A polyethylene resin composition comprising a second polyethylene resin formed by continuously polymerizing the first polyethylene resin formed in a first reactor in a second reactor. When the first polyethylene resin is formed in the first reactor, a comonomer is supplied at a supply ratio of 30 to 100 g / kg relative to ethylene, and H2 is supplied at a supply ratio of 20 to 60 mg / kg relative to ethylene. The zero-shear viscosity of the first polyethylene resin formed in the first reactor at 180 °C is from 10 6 poise to 10 8 poise, and the number of short-chain branches per 1000 carbons by 13 C-NMR is from 5 to 20, and The ratio of the zero-shear viscosity of the first polyethylene resin formed in the first reactor to that of the second polyethylene resin formed in the second reactor at 180 °C is 10 to 100, and by 13 the ratio of the number of short chain branches per 1000 carbons by C-NMR is 2 to 20, and The difference D2 - D1 between the density D2 of the second polyethylene resin and the density D1 of the first polyethylene resin is 0.01 g / cm 3 to 0.05 g / cm 3 , Wherein the ratio of the polymerization amounts of the first reactor and the second reactor is a weight ratio of (45 to 55):(55 to 45).

2. The polyethylene resin composition according to claim 1, wherein the density of the first polyethylene resin formed in the first reactor is 0.915 g / cm 3 to 0.935 g / cm 3 , and the density of the second polyethylene resin formed in the second reactor is 0.945 g / cm 3 to 0.965 g / cm 3 .

3. The polyethylene resin composition according to claim 1, wherein the melting temperature of the first polyethylene resin formed in the first reactor is 110°C to 126°C, and the difference between the melting temperature and the crystallization temperature is 10°C to 15°C.

4. The polyethylene resin composition according to claim 1, wherein the second polyethylene resin formed in the second reactor has a zero-shear viscosity of 9.0×10 4 poise to 7.0×10 5 poise at 180°C as measured by an ARES rheometer.

5. The polyethylene resin composition according to claim 1, wherein the number of short-chain branches per 1000 carbons of the second polyethylene resin formed in the second reactor is 1.0 to 5.0 by 13 13C-NMR.

6. The polyethylene resin composition according to claim 1, wherein the density of the polyethylene resin composition is 0.945 g / cm 3 to 0.970 g / cm 3 .

7. The polyethylene resin composition according to claim 1, wherein the melt flow index of the polyethylene resin composition is 0.4 g / 10 min to 3.0 g / 10 min at 190°C under a load of 2.16 kg, and 2.0 g / 10 min to 10 g / 10 min at 190°C under a load of 5 kg.

8. A method for manufacturing a polyethylene resin composition, the method comprising continuously polymerizing the first polyethylene resin formed in a first reactor in a second reactor to prepare a second polyethylene resin. When the first polyethylene resin is formed in the first reactor, a comonomer is supplied at a supply ratio of 30 to 100 g / kg relative to ethylene, and H2 is supplied at a supply ratio of 20 to 60 mg / kg relative to ethylene. The zero-shear viscosity of the first polyethylene resin formed in the first reactor at 180 °C is from 10 6 poise to 10 8 poise, and the number of short chain branches per 1000 carbons by 13 C-NMR is from 5.0 to 20, and The ratio of the zero-shear viscosity of the first polyethylene resin formed in the first reactor to the zero-shear viscosity of the second polyethylene resin formed in the second reactor at 180 °C is from 10 to 100, and by 13 the ratio of the number of short-chain branches per 1000 carbons by C-NMR is from 2 to 20, and The difference D2 - D1 between the density D2 of the second polyethylene resin and the density D1 of the first polyethylene resin is 0.01 g / cm 3 to 0.05 g / cm 3 , Wherein the ratio of the polymerization amounts of the first reactor and the second reactor is a weight ratio of (45 to 55):(55 to 45).

9. A molded article comprising the polyethylene resin composition according to any one of claims 1 to 7.

10. The molded article according to claim 9, wherein the molded article is a film that is successively biaxially stretched to a longitudinal elongation ratio of 4 to 6 times and a transverse elongation ratio of 8 to 10 times by a tenter frame process.

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