JP7736553B2 - Polyethylene resin composition - Google Patents

Description

The present invention relates to a polyethylene resin composition.

Polyethylene resin compositions are extruded to form molded articles such as sheets, films, or filaments. These molded articles are used as various industrial materials. A known polyethylene resin composition for extrusion molding is characterized by blending 0.01 to 1.5 ^parts by weight of (B) a fatty acid amide, 0.01 to 1.5 parts by weight of (C) an organic acid metal salt, and 0.01 to 1.0 parts by weight of (D) a phenolic antioxidant and/or a phosphorus-based antioxidant with 100 parts by weight of (A) a polyethylene resin having a density of 0.945 to 0.970 g/cm 3 and a melt index of 0.1 to 2.0 g/10 min (see Patent Document 1).

Japanese Patent Application Publication No. 7-126448

In particular, for molded articles intended for use in applications where they are likely to be visible to the public or come into contact with the skin, it is desirable that the surface formed by extrusion of a polyethylene resin composition be as smooth as possible from the standpoint of the appearance and feel of the molded article.

Therefore, one aspect of the present invention provides a polyethylene resin composition that can be extruded to form molded articles with smooth surfaces.

One aspect of the present invention relates to a polyethylene resin composition comprising a polyethylene resin and an organic acid metal salt, wherein the polyethylene resin has a density of 880 to 910 kg/ ^m3 and the content of the organic acid metal salt is 0.025 to 0.5 parts by mass per 100 parts by mass of the polyethylene resin.

One aspect of the present invention provides a polyethylene resin composition that can be extruded to form molded articles with smooth surfaces.

The present invention is not limited to the following examples.

An example of a polyethylene resin composition contains at least a polyethylene resin and an organic acid metal salt.

Polyethylene-based resins are copolymers containing ethylene-based monomer units. The polyethylene-based resin may be, for example, an ethylene-α-olefin copolymer. From the viewpoint of excellent moldability, the polyethylene-based resin may be an ethylene-α-olefin copolymer having long chain branches. The polyethylene-based resin may be a single type, or two or more types may be used in combination.

The number of carbon atoms of the α-olefin in the ethylene-α-olefin copolymer may be 4 to 20, 5 to 20, or 6 to 20. Examples of α-olefins include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The α-olefin may be a single type, or two or more types may be used in combination. The α-olefin may be 1-hexene, 4-methyl-1-pentene, or 1-octene.

The content of ethylene-based monomer units (ethylene units) in the polyethylene-based resin may be 50% by mass or more, 70% by mass or more, 75% by mass or more, or 79% by mass or more, relative to the total mass of the polyethylene-based resin, and may be 99.5% by mass or less, 95% by mass or less, 92% by mass or less, or 89% by mass or less. The content of ethylene-based monomer units (ethylene units) in the polyethylene-based resin may be 50 to 99.5% by mass, relative to the total mass of the polyethylene-based resin.

The content of monomer units based on α-olefins in the polyethylene resin may be 0.5% by mass or more, 5% by mass or more, 8% by mass or more, or 11% by mass or more, relative to the total mass of the polyethylene resin, and may be 50% by mass or less, 30% by mass or less, 25% by mass or less, or 21% by mass or less. The content of monomer units based on α-olefins in the polyethylene resin may be 0.5 to 50% by mass, relative to the total mass of the polyethylene resin.

Polyethylene-based resins may contain monomer units based on other monomers in addition to ethylene-based and α-olefin-based monomer units. Examples of other monomers include conjugated dienes (e.g., butadiene and isoprene), non-conjugated dienes (e.g., 1,4-pentadiene), acrylic acid, acrylic acid esters (e.g., methyl acrylate and ethyl acrylate), methacrylic acid, methacrylic acid esters (e.g., methyl methacrylate and ethyl methacrylate), and vinyl acetate.

Examples of polyethylene-based resins include ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-1-butene-1-hexene copolymer, ethylene-1-butene-4-methyl-1-pentene copolymer, and ethylene-1-butene-1-octene copolymer. The polyethylene-based resin may be ethylene-1-hexene copolymer, ethylene-1-butene-1-hexene copolymer, or ethylene-1-butene-4-methyl-1-pentene copolymer.

The density of the polyethylene resin is 880 to 910 kg/m ³ . From the viewpoint of increasing the rigidity of the molded body and the viewpoint of reducing deformation of the molded body due to load, the density of the polyethylene resin may be 881 kg/m ^{or more} , 882 kg/m ^{or more} , 883 kg/m ^or more, 884 kg/m ^{or more} , 885 kg/m ^{or more} , 886 kg/m or more, 887 kg/m ^or more, 888 kg/m ^or more, 889 kg/m ^or more, 890 kg/m ^or more, 891 kg/m ^or more, 892 kg/m ^or more, 893 kg/m ^or more, 894 kg/m ^or more, 895 kg/m ^{or more} , 896 kg/m ^or more, 897 kg/m ^{or more} , 898 kg/m ^{or more} , 899 kg/m ^{or more} , or 900 kg/m or ^more . From the viewpoint of further improving the transparency of the molded article and from the viewpoint of increasing the impact resistance of the molded article, the density of the polyethylene resin may be 909 kg/m ^or less, 908 kg/m ^or less, 907 kg/m ^{or less} , 906 kg/m ^or less, 905 kg/m ^{or less} , 904 kg/m ^{or less} , 903 kg/m ^{or less} , 902 kg/m ^or less, 901 kg/m or less, or 900 kg/m or ^less . The density of the polyethylene resin means a value measured according to the method specified in Method A of JIS K7112-1980.

The MFR (melt flow rate) of the polyethylene resin may be 3.0 g/10 min or more, 3.2 g/10 min or more, or 3.4 g/10 min or more, from the viewpoints of improving moldability and reducing the load applied during extrusion. The MFR of the polyethylene resin may be 8.5 g/10 min or less, 8.0 g/10 min or less, 7.5 g/10 min or less, 7.0 g/10 min or less, 6.5 g/10 min or less, 6.0 g/10 min or less, 5.5 g/10 min or less, 5.0 g/10 min or less, or 4.5 g/10 min or less, from the viewpoint of improving the mechanical strength of the molded article. The MFR of the polyethylene resin may be 3.0 to 8.5 g/10 min, or 3.0 to 5.0 g/10 min. The MFR of polyethylene resins refers to the value measured using Method A under conditions of a load of 21.18 N and a temperature of 190°C, as specified in JIS K7210-1995.

The molecular weight distribution Mw/Mn of the polyethylene resin may be 1.5 or greater, or 1.7 or greater, from the viewpoints of improving moldability and reducing the load applied during extrusion. The molecular weight distribution Mw/Mn of the polyethylene resin may be 2.5 or less, or 2.0 or less, from the viewpoint of improving the mechanical strength of the molded body. The molecular weight distribution Mw/Mn of the polyethylene resin may be 1.5 to 2.5. The molecular weight distribution Mw/Mn of the polyethylene resin refers to a value calculated from the weight average molecular weight (Mw) and number average molecular weight (Mn) measured by gel permeation chromatography (GPC). Specifically, the molecular weight distribution Mw/Mn of the polyethylene resin can be calculated by the method described in the Examples below.

The temperature at which the maximum value of the melting peak observed in differential scanning calorimetry of a polyethylene-based resin is observed (hereinafter sometimes referred to as the "melting peak temperature") may be 100°C or lower, 95°C or lower, 93°C or lower, 90°C or lower, 85°C or lower, or 80°C or lower, from the viewpoints of improving moldability and reducing the load on the polyethylene-based resin composition during extrusion molding. The melting peak temperature of a polyethylene-based resin may be 50°C or higher, 55°C or higher, 60°C or higher, 65°C or higher, 70°C or higher, or 75°C or higher. The melting peak temperature of a polyethylene-based resin refers to the temperature indicated by the maximum value of the melting peak with the greatest height among the melting peaks present in the range from 25°C to 150°C, obtained by obtaining a DSC thermogram including a melting peak using a differential scanning calorimeter. Specifically, the maximum melting peak temperature of a polyethylene-based resin can be measured by the method described in the Examples below.

Polyethylene-based resins can be produced by conventional polymerization methods using conventional polymerization catalysts. Examples of polymerization catalysts include metallocene catalysts, vanadium-based catalysts, Ziegler-Natta catalysts, and chromium-based catalysts. Examples of polymerization methods include liquid-phase polymerization, slurry polymerization, gas-phase polymerization, and high-pressure ionic polymerization. The polymerization method may be, for example, batch polymerization, continuous polymerization, or multi-stage polymerization with two or more stages. Commercially available polyethylene-based resins with a specified density can also be used.

Examples of metallocene catalysts include those described in JP-A-58-19309, JP-A-60-35005, JP-A-60-35006, JP-A-60-35007, JP-A-60-35008, JP-A-61-130314, JP-A-3-163088, JP-A-4-268307, JP-A-9-12790, JP-A-9-87313, JP-A-11-80233, and JP-T-10-508055.

Specific examples of metallocene catalysts include catalysts having a metallocene ^compound represented by ^the general formula ^{R1kR2lR3mR4nM} (wherein M is zirconium, titanium, hafnium, or ^vanadium ; ^R1 is a group having a cyclopentadiene-type anion skeleton; _R2 ^, _R3 ^, _and ^R4 are _each a group having a cyclopentadiene-type anion skeleton, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or a hydrogen atom; k and l are integers of 1 or more, and k+l+m+n=4), and an organoaluminum oxide compound.

Examples of metallocene compounds represented by the above general formula include bis(cyclopentadienyl)diethyltitanium, bis(cyclopentadienyl)dimethyltitanium, bis(pentamethylcyclopentadienyl)titanium, bis(cyclopentadienyl)dichlorotitanium, bis(cyclopentadienyl)titanium monochloride monohydride, bis(indenyl)titanium monochloride monohydride, bis(indenyl)titanium dichloride, ethylene Ethylene bis(indenyl)dimethyl titanium, ethylene bis(indenyl)methyl titanium chloride, ethylene bis(indenyl)titanium dichloride, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)titanium dichloride, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)dimethyl titanium, ethylene bis(4-methyl-1-indenyl)titanium dichloride, ethylene bis(2,3-dimethyl-1-indenyl)titanium dichloride, bis(cyclopentadienyl)diethyltitanium, bis(cyclopentadienyl)dimethylzirconium, bis(pentamethylcyclopentadienyl)zirconium, bis(cyclopentadienyl)dichlorozirconium, bis(cyclopentadienyl)monochloride monohydride, bis(indenyl)zirconium monochloride monohydride, bis(indenyl)zirconium dichloride, ethylenebis(indenyl)dimethylzirconium, ethylene Examples include ethylene bis(indenyl)methyl zirconium dichloride, ethylene bis(indenyl)zirconium dichloride, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)dimethyl zirconium, ethylene bis(4-methyl-1-indenyl)zirconium dichloride, and ethylene bis(2,3-dimethyl-1-indenyl)zirconium dichloride.

Examples of organoaluminum oxide compounds include tetramethyldialuminoxane, tetraethyldialuminoxane, tetrabutyldialuminoxane, tetrahexyldialuminoxane, methylaluminoxane, ethylaluminoxane, butylaluminoxane, and hexylaluminoxane.

The vanadium catalyst may be a catalyst containing a vanadium compound and an organoaluminum compound. Examples of the vanadium compound include compounds represented by the general formula VO(OR) _{nX3 -n} (wherein R is a hydrocarbon group, X is a halogen atom, and n is an integer of 0 to 3), such as _VOCl3 , VO( _OCH3 ) _Cl2 , VO( _OCH3 ) _2Cl , VO( _OCH3 ) ₃ , VO( _{OC2H5 ) Cl2} , VO( _OC2H5 ) _2Cl , VO( _{OC2H5 ) 3} , VO _{( OC3H7} ) _{Cl2, VO(OC3H7)2Cl , VO ( OC3H7 ) 3 ,} and mixtures thereof.

Examples of organoaluminum compounds include compounds represented by the general formula _{R'mAlX3 -m (} wherein R' is a hydrocarbon group, X is a halogen atom, and _m is an integer of 1 to 3), and specific examples include ( _{C2H5 ) 2AlCl} , _{( C4H9 )} 2AlCl, ( _C6H13 ) _{2AlCl ,} ( _C2H5 ) _{1.5AlCl1.5 , ( C4H9 ) 1.5AlCl1.5} , _{( C6H13 ) 1.5AlCl1.5 , C2H5AlCl2 , C4H9AlCl2 , and C6H13AlCl2 .}

Ziegler-Natta catalysts include catalysts consisting of at least one component selected from the group consisting of titanium trichloride, vanadium trichloride, titanium tetrachloride, and titanium haloalcoholates supported on a magnesium compound support, and an organometallic co-catalyst, as well as catalysts consisting of a coprecipitate or eutectic of a magnesium compound and a titanium compound, and an organometallic co-catalyst.

Examples of chromium-based catalysts include those consisting of a chromium compound supported on silica or silica-alumina, and an organometallic compound as a co-catalyst.

The content of the polyethylene resin may be 95% by mass or more, 97% by mass or more, or 99% by mass or more, based on the total mass of the polyethylene resin composition, and may be 99.9% by mass or less, 99.5% by mass or less, or 99.1% by mass or less. The content of the polyethylene resin may be 95 to 99.9% by mass, based on the total mass of the polyethylene resin composition.

An organic acid metal salt is a salt formed from an organic acid and a metal. The organic acid metal salt may be a metal soap. The organic acid may be a higher fatty acid or an aliphatic oxyacid. The metal may be magnesium, calcium, barium, zinc, aluminum, lithium, tin, or lead.

Examples of higher fatty acids include chain monocarboxylic acids having 10 to 22 carbon atoms. The aliphatic oxyacid may be an aliphatic carboxylic acid having an alcoholic hydroxyl group.

The organic acid metal salt may be, for example, at least one selected from the group consisting of magnesium stearate, calcium stearate, barium stearate, zinc stearate, aluminum stearate, lithium stearate, calcium citrate, calcium lactate, calcium 12-hydroxystearate, calcium stearyl lactate, and calcium lauryl lactate.

From the viewpoint of reducing the load on the polyethylene resin composition during extrusion molding, the content of the organic acid metal salt may be 0.025 parts by mass or more, 0.030 parts by mass or more, 0.040 parts by mass or more, 0.045 parts by mass or more, or 0.50 parts by mass or more per 100 parts by mass of the polyethylene resin. From the viewpoint of maintaining the mechanical strength of the molded product, the content of the organic acid metal salt may be 0.5 parts by mass or less, 0.4 parts by mass or less, 0.3 parts by mass or less, 0.2 parts by mass or less, or 0.1 parts by mass or less per 100 parts by mass of the polyethylene resin. The content of the organic acid metal salt may be 0.025 to 0.5 parts by mass based on the total mass of the polyethylene resin composition.

The polyethylene resin composition may further contain components other than the polyethylene resin and the organic acid metal salt. For example, the polyethylene resin composition may further contain stabilizers, lubricants, antistatic agents, antiblocking agents, dyes, pigments, etc.

Examples of stabilizers include phenolic stabilizers such as 2,6-di-t-butyl-p-cresol (BHT), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, and n-octadecyl-3-(4'-hydroxy-3,5'-di-t-butylphenyl)propionate; and phosphite stabilizers such as bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite and tris(2,4-di-t-butylphenyl)phosphite.

The lubricant may be an organic fatty acid amide. Examples of organic fatty acid amides include saturated fatty acid amides, unsaturated fatty acid amides, saturated fatty acid bisamides, and unsaturated fatty acid bisamides. Examples of saturated fatty acid amides include stearic acid amide and behenic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of saturated fatty acid bisamides include ethylene bisstearic acid amide. Examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, and N,N'-dioleyl sebacate amide.

Examples of antistatic agents include glycerin esters of fatty acids having 8 to 22 carbon atoms, sorbitan acid esters, and polyethylene glycol esters. Examples of antiblocking agents include silica, calcium carbonate, and talc.

The polyethylene resin composition can be produced by melt-kneading a polyethylene resin and an organic acid metal salt. The polyethylene resin composition may also be produced by melt-kneading multiple polyethylene resins and organic acid metal salts.

Methods for melt-kneading polyethylene resin and organic acid metal salt include mixing the polyethylene resin and organic acid metal salt in a blender such as a Henschel mixer or tumbler mixer, and then melt-kneading using a single-screw extruder, twin-screw extruder, Banbury mixer, heated roll, etc. Methods for adding components other than the polyethylene resin and organic acid metal salt include melt-kneading the polyethylene resin together with the organic acid metal salt, dry blending, and preparing a masterbatch and dry-blending this masterbatch with the polyethylene resin, etc.

The polyethylene-based resin composition may be for extrusion molding. By extrusion molding using the polyethylene-based resin composition according to the present disclosure, a molded article having a smooth surface can be easily formed. For example, the surface roughness Rz of a molded article formed by extrusion molding in which the polyethylene-based resin composition is discharged through a die hole can be 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, or 1.0 μm or less when the shear rate of the polyethylene-based resin composition passing through ^the die hole is 950 to 1050 s −1. The polyethylene-based resin composition may be formed by melt-kneading a raw material mixture containing a polyethylene-based resin and an organic acid metal salt in an extruder.

The present invention will be explained in detail below using examples. However, the present invention is not limited to the following examples.

1. Polyethylene Resin The following polyethylene resin was prepared.
Polyethylene resin P1 (ethylene-1-hexene copolymer, ethylene unit content: 80% by mass)
Polyethylene resin P2 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P3 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P4 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P5 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P6 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P7 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P8 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P9 (ethylene-1-hexene copolymer, ethylene unit content: 79% by mass)
Polyethylene resin P10 (ethylene-1-hexene copolymer, ethylene unit content: 82% by mass)
Polyethylene resin P11 (ethylene-1-hexene copolymer, ethylene unit content: 80% by mass)
Polyethylene resin P12 (ethylene-1-hexene copolymer, ethylene unit content: 83% by mass)
Polyethylene resin P13 (ethylene-1-hexene copolymer, ethylene unit content: 89% by mass)

2. Evaluation of Density of Polyethylene Resin The density of the polyethylene resin was measured according to the method specified in Method A of JIS K7112-1980.

Melt Flow Rate The melt flow rate of the polyethylene resin was measured by Method A specified in JIS K7210-1995 under conditions of a load of 21.18 N and a temperature of 190°C.

Molecular weight distribution Mw/Mn
The weight-average molecular weight Mw and number-average molecular weight Mn of the polyethylene resin were measured in terms of standard polystyrene using gel permeation chromatography (GPC) under the following conditions (1) to (8). The molecular weight distribution Mw/Mn of the polyethylene resin was calculated from Mw and Mn. The baseline on the chromatogram was a straight line connecting a point in a stable, flat region with a retention time sufficiently shorter than that at which the elution peak of the polyethylene resin appears and a point in a stable, flat region with a retention time sufficiently longer than that at which the solvent elution peak is observed.
(1) Apparatus: Waters 150C, manufactured by Waters
(2) Separation column: TOSOH TSKgel GMH6-HT
(3) Measurement temperature: 140℃
(4) Carrier: orthodichlorobenzene (5) Flow rate: 1.0 mL/min (6) Injection volume: 500 μL
(7) Detector: differential refraction (8) Molecular weight standard: standard polystyrene

Melting Peak Temperature: A polyethylene resin was pressed at 10 MPa for 5 minutes using a hot press at 150°C, followed by cooling for 5 minutes using a cooling press at 30°C to obtain a sheet approximately 100 μm thick. Approximately 10 mg of a sample was cut out of the sheet and sealed in an aluminum pan. Using the aluminum pan containing the sample, differential scanning calorimetry was performed under the following conditions: holding at 150°C for 5 minutes, cooling from 150°C to -80°C at 10°C/min, holding at -80°C for 2 minutes, and heating from -80°C to 150°C at 10°C/min, thereby obtaining a DSC thermogram including a melting peak. A differential scanning calorimeter (PerkinElmer, DSC-7 type differential scanning calorimeter) was used as the measuring device. The temperature at which the maximum value of the melting peak with the greatest height was observed among the melting peaks present in the range from 25°C to 150°C in the obtained DSC thermogram was determined as the melting peak temperature.

3. Extrusion Molding Test A co-rotating twin-screw kneading extruder (KZW20TW, manufactured by Technobel Co., Ltd.) having a feeder and a nozzle head attached to the extruder side was prepared. The temperatures of nine barrels C1 to C9, which were arranged in order from the hopper side of the twin-screw kneading extruder along the extrusion direction, were 100°C for barrel C1, 170°C for barrel C2, and 210°C for barrels C3 to C9. A polyethylene resin and an organic acid metal salt shown in Table 1 or Table 2 were charged into the hopper opening of barrel C1 of the twin-screw kneading extruder. Tables 1 and 2 show the amount of organic acid metal salt added per 100 parts by mass of polyethylene resin (unit: parts by mass). The nozzle head temperature was set to 210°C, and the screw rotation speed was set to 300 rpm, and the polyethylene resin and the organic acid metal salt were melt-kneaded. The formed kneaded product (polyethylene resin composition) was discharged from the die hole of the twin-screw kneading extruder at a throughput rate of 5 kg/hour. The discharged kneaded product was cooled in a water bath at 10 to 35°C to obtain a strand-shaped molded product. The shear rate γ of the polyethylene resin composition passing through the die hole was calculated using the formula: γ = 32Q/(πD ³ ) and was found to be 950 to 1050 S ^-1 . In the formula, Q is the volumetric flow rate of the polyethylene resin composition (unit: mm ³ /s), and D is the inner diameter of the die hole (unit: mm).

Appearance The appearance of the strand-shaped molded products produced was visually observed, and the appearance of each molded product was classified as transparent, translucent, or opaque.

The surface roughness of the molded body was evaluated using a microscope (RH-2000, manufactured by HiROX Corporation). Specifically, photographs of the molded body surface were taken at intervals of 0.15 μm along a direction perpendicular to the extrusion direction of the strand, and the obtained images were processed using a 3D profile to determine the surface roughness Rz.

Time until appearance of scum When obtaining a strand-shaped molded product, the time until adhesion of scum to the die holes was confirmed was measured, with 5 minutes after the polyethylene resin and the organic acid metal salt were charged into the hopper opening provided in the barrel C1 of the twin-screw kneading extruder being set as 0 minutes.

Claims (6)

Contains a polyethylene resin and an organic acid metal salt,
The density of the polyethylene resin is 880 to 910 kg/ ^m3 ,
the organic acid metal salt is a salt formed from an organic acid and a metal,
the organic acid is a higher fatty acid ,
the higher fatty acid is a chain monocarboxylic acid having 10 to 22 carbon atoms ,
The polyethylene-based resin composition has a content of the organic acid metal salt of 0.025 to 0.5 parts by mass per 100 parts by mass of the polyethylene-based resin. 2. The polyethylene resin composition according to claim 1, wherein the organic acid metal salt is at least one selected from the group consisting of magnesium stearate, calcium stearate, barium stearate, zinc stearate, aluminum stearate, and lithium stearate. 3. The polyethylene resin composition according to claim 1 , wherein the polyethylene resin has an MFR of 3.0 to 8.5 g/10 min. the molecular weight distribution Mw/Mn of the polyethylene resin is 1.5 to 2.5;
The polyethylene resin composition according to any one of claims 1 to 3 , wherein the temperature at which the maximum value of the melting peak observed in differential scanning calorimetry of the polyethylene resin is shown is 100°C or lower. The polyethylene resin composition according to any one of claims 1 to 4 , which is for extrusion molding. 6. The polyethylene resin composition according to claim 1, wherein a molded article formed by extrusion molding the polyethylene resin composition through a die hole has a surface roughness Rz of 4.5 μm or less when the shear rate of the polyethylene resin composition passing through the die hole is 950 to 1,050 ^s .