Low density polyethylene composition and molded body thereof and method for producing the same

Abstract

To provide a low density polyethylene composition and a molded body thereof, which have excellent low staining properties to an adherend while suppressing thermal degradation during processing and also have excellent high-speed film-forming properties and a method for producing the same.SOLUTION: There is provided a low density polyethylene composition which comprises a low density polyethylene and an antioxidant, wherein the composition has a melt flow rate at 190°C under a load of 2.16 kg of 0.1 g / 10 min or more and 20.0 g / 10 min or less, the composition has a density of 910 kg / m3 or more and 935 kg / m3 or less, the antioxidant includes an antioxidant A having a phenol skeleton and an antioxidant B having a phenol skeleton other than the antioxidant A, the molecular weight Ma of the antioxidant A is 50 g / mol or more and 1200 g / mol or less, the molecular weight Ma and the molecular weight Mb of the antioxidant B satisfy the condition of Ma<Mb and the content Wa of the antioxidant A in the composition is 5 ppm or more and 450 ppm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a low-density polyethylene composition, a molded article thereof, and a process for producing the same. [Background technology]

[0002] Low-density polyethylene compositions are molded by various molding methods and used in a wide range of applications. The properties required of the low-density polyethylene compositions vary depending on the molding method and application.

[0003] A typical application of low-density polyethylene is a film. Specifically, a surface protection film is known as a film. The surface protection film is attached to the surface of an adherend such as a metal plate, a resin plate, a wooden decorative plate, a nameplate, a liquid crystal member, an electric / electronic part, a building material, and an automobile part for the purpose of preventing scratches and stains from the outside during processing, transportation, and storage.

[0004] Surface protection films are required to have few fisheyes in order to prevent scratches on the substrate they are intended to protect. To meet this requirement, it is also desirable for the low-density polyethylene used as the raw material to have few fisheyes.

[0005] As a method for producing low-density polyethylene with fewer fisheyes, for example, Patent Document 1 discloses a method in which 170 ppm of 2,6-di-tert-butyl-4-methylphenol, a phenolic antioxidant, is added as a polymerization inhibitor to ethylene gas as a raw material. Patent Document 1 describes that the radical scavenging function of the antioxidant suppresses crosslinking reactions between low-density polyethylene molecules in a polymerization reactor, and as a result, low-density polyethylene with reduced fisheyes can be provided.

[0006] Furthermore, Patent Document 2 describes a method of suppressing the occurrence of fisheyes by setting the amount of an antioxidant to 0.1 ppm or more and 3.0 ppm or less.

[0007] On the other hand, in recent years, there has been a demand for thinner surface protection films from the viewpoints of cost reduction and environmental load reduction. Thinner films can be achieved by increasing the production rate of the film forming machine and taking up the film at high speed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2003-342307 A [Patent Document 2] JP 2010-202697 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in Patent Document 1, the antioxidant remains in the low-density polyethylene, and therefore the antioxidant bleeds out from the surface of the obtained surface protection film over time, which causes a problem that the adherend to be protected is contaminated by the antioxidant.

[0010] Furthermore, when the production rate of a film-making machine is increased to reduce the thickness, high shear is generated in the low-density polyethylene at the film outlet, which tends to cause the low-density polyethylene to thermally deteriorate. If the low-density polyethylene that has been thermally deteriorated at the film outlet is mixed into the film product, fish eyes tend to become apparent due to the difference in viscosity between the thermally deteriorated area and normal areas.

[0011] Furthermore, in Patent Document 2, the amount of antioxidant is reduced to suppress fisheyes and to obtain low contamination of the adherend. However, under high-speed processing conditions, even if the low-density polyethylene contains a small number of fisheyes, there is a problem that fisheyes occur due to thermal degradation in the film forming machine, resulting in a decrease in the fisheye quality of the film. Patent Document 2 does not consider thinning at all, and does not verify thermal degradation in the film forming machine at all. The amount of antioxidant described in Patent Document 2 is not sufficient to reduce thermal degradation in the film forming machine, and there is room for improvement.

[0012] The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-density polyethylene composition which is excellent in low-fouling properties to adherends and further excellent in high-speed film-formability while suppressing thermal degradation during processing, a molded article thereof, and a production method thereof. [Means for solving the problem]

[0013] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems and have found that the above problems can be solved by a specific low-density polyethylene composition, thereby completing the present invention.

[0014] That is, the present invention includes the following embodiments. [1] A low-density polyethylene composition comprising a low-density polyethylene and an antioxidant, the composition having a melt flow rate of 0.1 g / 10 min or more and 20.0 g / 10 min or less at 190° C. under a load of 2.16 kg, and a density of 910 kg / m 3 More than 935kg / m 3The following, wherein the antioxidant includes antioxidant A having a phenolic skeleton and antioxidant B having a phenolic skeleton other than antioxidant A, the molecular weight Ma of antioxidant A is 50 g / mol or more and 1200 g / mol or less, and the condition Ma < Mb is satisfied for the molecular weight Ma and the molecular weight Mb of antioxidant B, and the content Wa of antioxidant A in the composition is 5 ppm or more and 450 ppm or less, a low-density polyethylene composition.

[0015] 〔2〕The low-density polyethylene composition according to 〔1〕, wherein the value of Wa / Wb of the content Wa of antioxidant A with respect to the content Wb of antioxidant B in the composition is 0.05 or more and 0.45 or less.

[0016] 〔3〕The low-density polyethylene composition according to 〔1〕 or 〔2〕, wherein the molecular weight Ma is 50 g / mol or more and 600 g / mol or less, and the difference (Mb - Ma) between the molecular weight Mb and the molecular weight Ma is 100 g / mol or more and 1500 g / mol or less.

[0017] 〔4〕The low-density polyethylene composition according to any one of 〔1〕 to 〔3〕, wherein the absolute value (|Tga - Tgb|) of the difference between the melting point Tga of antioxidant A and the melting point Tgb of antioxidant B is 59 °C or less.

[0018] 〔5〕A molded article of the low-density polyethylene composition according to any one of 〔1〕 to 〔4〕.

[0019] 〔6〕The molded article according to 〔5〕, wherein the molded article is a film.

[0020] 〔7〕A method for producing a low-density polyethylene composition comprising low-density polyethylene and an antioxidant, the method comprising: a first mixing step of mixing the antioxidant A and the antioxidant B in a molten state; and a second mixing step of mixing the mixture obtained in the first mixing step in a molten state with low-density polyethylene in a molten state, wherein the melt flow rate of the composition at 190 ° C and a load of 2.16 kg is 0.1 g / 10 min or more and 20.0 g / 10 min or less, and the density of the composition is 910 kg / m 3 or more and 935 kg / m 3 or less, the antioxidant comprising an antioxidant A having a phenolic skeleton and an antioxidant B having a phenolic skeleton other than the antioxidant A, the molecular weight Ma of the antioxidant A being 50 g / mol or more and 1200 g / mol or less, and the molecular weight Ma and the molecular weight Mb of the antioxidant B satisfying the condition Ma < Mb, and the content Wa of the antioxidant A in the composition being 5 ppm or more and 450 ppm or less.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a low-density polyethylene and a molded article thereof that are excellent in low contamination to an adherend and further excellent in high-speed film formation while suppressing thermal deterioration during processing, and a method for producing the same.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be variously modified and implemented within the scope of its gist.

[0023] 〔Low-Density Polyethylene Composition〕 The low-density polyethylene composition of this embodiment (hereinafter, also simply referred to as "composition") contains low-density polyethylene and an antioxidant. The antioxidant includes antioxidant A having a phenol skeleton (hereinafter, also simply referred to as "antioxidant A") and antioxidant B having a phenol skeleton other than antioxidant A (hereinafter, also simply referred to as "antioxidant B"), and satisfies the following <Condition (A)> to <Condition (D)>.

[0024] <Condition (A)> The melt flow rate of the composition at 190 °C and a load of 2.16 kg is 0.1 g / 10 min or more and 20.0 g / 10 min or less.

[0025] <Condition (B)> The density of the composition is 910 kg / m 3 or more and 935 kg / m 3 or less.

[0026] <Condition (C)> The molecular weight Ma of antioxidant A is 50 g / mol or more and 1200 g / mol or less, and the condition Ma < Mb is satisfied for the molecular weight Ma of antioxidant A and the molecular weight Mb of antioxidant B.

[0027] <Condition (D)> The content Wa of antioxidant A in the composition is 5 ppm or more and 450 ppm or less.

[0028] Since the composition has such a configuration, a composition that suppresses thermal deterioration during processing, is excellent in low contamination to the adherend, and is further excellent in adhesion to the adherend can be obtained.

[0029] The composition preferably further satisfies at least one condition selected from the group consisting of the following <Condition (E)> to <Condition (G)>, more preferably further satisfies at least two conditions selected from the group consisting of the following <Condition (E)> to <Condition (G)>, and even more preferably further satisfies all of the following <Condition (E)> to <Condition (G)>. By providing the composition with such a constitution, there is a tendency to obtain a composition which is more excellent in low staining properties for adherends and more excellent in adhesion to adherends while further suppressing thermal deterioration during processing.

[0030] <Condition (E)> The value of the content Wa (ppm) of the antioxidant A relative to the content Wb (ppm) of the antioxidant B in the composition (Wa / Wb) is 0.05 or more and 0.45 or less.

[0031] <Condition (F)> The molecular weight Ma of antioxidant A is 50 g / mol or more and 600 g / mol or less, and the difference between the molecular weight Mb of antioxidant B and the molecular weight Ma of antioxidant A (Mb-Ma) is 100 g / mol or more and 1500 g / mol or less.

[0032] <Condition (G)> The absolute value of the difference (|Tga-Tgb|) between the melting point Tga (°C) of antioxidant A and the melting point Tgb (°C) of antioxidant B is 59°C or less.

[0033] Examples of the low-density polyethylene according to the present embodiment include high-pressure low-density polyethylene, linear low-density polyethylene, and other special ultra-low-density polyethylene. Among them, high-pressure low-density polyethylene is preferred because it contains fewer fish eyes in the raw material, has better stability during film processing, can further suppress thermal degradation during processing, and has better high-speed film-forming properties. Linear low-density polyethylene and other special ultra-low-density polyethylene tend to contain metal components derived from the polymerization catalyst and oligomers generated by unreacted comonomers. Therefore, high-pressure low-density polyethylene is also preferred from the viewpoints of thermal stability and contamination of the adherend.

[0034] The low-density polyethylene according to the present embodiment may be, for example, one produced from ethylene produced from biomass-derived naphtha as a raw material. For example, the biomass-derived low-density polyethylene can be produced from biomass-derived naphtha as a raw material by a conventionally known method.

[0035] (Melt Flow Rate) As shown in the above <Condition (A)>, the composition has a melt flow rate of 0.1 g / 10 min or more and 20.0 g / 10 min or less at 190° C. and a load of 2.16 kg. The lower limit is preferably 0.5 g / 10 min or more, more preferably 1.0 g / 10 min or more, and even more preferably 2.0 g / 10 min or more. The upper limit is preferably 15.0 g / 10 min or less, more preferably 10.0 g / 10 min or less, and even more preferably 7.0 g / 10 min or less.

[0036] When the melt flow rate of the composition is within the above range, the composition tends to have sufficient fluidity when molded into a film.

[0037] In the present embodiment, the melt flow rate (g / 10 min) of the low-density polyethylene composition is measured under conditions of 190° C. and a load of 2.16 kg using a melt flow rate measuring device conforming to JIS K7210 Code D: 1999. For specific measurement methods, see the Examples.

[0038] The melt flow rate of the low-density polyethylene composition can be controlled within the above range, for example, by adjusting the polymerization temperature, polymerization pressure, and the presence or absence of a chain transfer agent.

[0039] (density) As shown in the above <Condition (B)>, the composition has a density of 910 kg / m 3 More than 935kg / m 3 The lower limit is preferably 913 kg / m 3 More preferably, 917 kg / m 3More preferably, it is 920 kg / m or more. 3 The upper limit is preferably 930 kg / m 3 More preferably, it is 925 kg / m or less. 3 More preferably, it is 924 kg / m or less. 3 The following is the result.

[0040] Density 910kg / m 3 If the density is 935 kg / m or more, a film having sufficient strength tends to be obtained. 3 When the density is 940 kg / m or less, the stability during high-speed film formation is excellent, and the obtained film has sufficient flexibility and tends to easily conform to and adhere to an adherend. 3 If high density polyethylene having the above properties is used, the film is likely to tear during high speed film formation, and the film is likely to wrinkle, tending to deteriorate the adhesion to the adherend.

[0041] In this embodiment, the density (kg / m 3 ) is measured by a density gradient tube method (23° C.) in accordance with JIS K7112:1999. For specific measurement methods, see the Examples.

[0042] The density of the low-density polyethylene composition can be controlled within the above range by adjusting, for example, the polymerization temperature, the polymerization pressure, and the presence or absence of a chain transfer agent.

[0043] (Antioxidants) The composition contains an antioxidant, and the antioxidant includes antioxidant A having a phenol skeleton and antioxidant B having a phenol skeleton other than antioxidant A. When the molecular weight of antioxidant A is Ma (g / mol) and the molecular weight of antioxidant B is Mb (g / mol), as shown in the <Condition (C)>, the molecular weight Ma of antioxidant A is 50 g / mol or more and 1200 g / mol or less. As shown in the <Condition (C)>, the molecular weight Ma of antioxidant A and the molecular weight Mb of antioxidant B satisfy the condition Ma < Mb. As long as the molecular weight Ma of antioxidant A satisfies the above range and the molecular weight Ma of antioxidant A and the molecular weight Mb of antioxidant B satisfy the condition Ma < Mb, antioxidant A may be used alone or in combination of two or more. Similarly, antioxidant B may also be used alone or in combination of two or more.

[0044] When an antioxidant having a phenol skeleton is contained in low-density polyethylene, it can capture radicals generated by thermal degradation of low-density polyethylene and suppress the cross-linking reaction and oxidative degradation reaction of low-density polyethylene. Therefore, in processing machines such as film forming machines, the generation of fish eyes due to thermal degradation can be preferably suppressed. On the other hand, an antioxidant having a phenol skeleton tends to cause a bleed-out phenomenon due to the strong polarity of the phenol group.

[0045] The radical scavenging function and the ease of bleed-out of an antioxidant having a phenol skeleton can be controlled by the molecular weight and molecular structure. In particular, the molecular weight of an antioxidant having a phenol skeleton is known to affect the radical scavenging function and the ease of bleed-out. Generally, the lower the molecular weight of an antioxidant having a phenol skeleton, the easier it is to escape from the crystal structure of polyethylene, and the tendency of the bleed-out phenomenon to occur is high, but the radical scavenging ability tends to be excellent. Also, the higher the molecular weight of an antioxidant having a phenol skeleton, the more difficult it is to escape from the crystal structure of polyethylene, and the tendency of the bleed-out phenomenon to occur is low, but the radical scavenging ability tends to be inferior.

[0046] In this embodiment, it has been found that by mixing two types of antioxidants having phenol skeletons with different molecular weights in low-density polyethylene, it is possible to suppress the bleed-out of the antioxidants while suppressing thermal degradation of the low-density polyethylene.

[0047] Examples of the antioxidants A and B include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone, pentaerythritol tetrakis[3-(3,5 -di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene), 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxa Spiro[5,5]undecane, bis[3,3-bis(4'-hydroxy-3'-t-butylphenyl)butyric acid] glycol ester, 2,2'-ethylidenebis(4,6-di-t-butylphenol), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2' -Oxamide bis[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,1,3-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-Triazine, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzodioxaphosphepin-6-yl)oxy}propyl-2-methylphenol, and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane are mentioned. In this embodiment, from the antioxidants having these phenolic skeletons, two types of antioxidants A and B having different molecular weights can be used in combination such that the molecular weight Ma of antioxidant A is 50 g / mol or more and 1200 g / mol or less, and Ma < Mb where Ma is the molecular weight of antioxidant A and Mb is the molecular weight of antioxidant B.,

[0048] As the antioxidants A and B, 2,6-di-t-butyl-4-methylphenol, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3-t-butyl-4-hydroxy-5-methylbenzene propanoic acid) ethylene bis(oxyethylene), 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene propanamide], thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane are preferred. By combining two types of antioxidants A and B with different molecular weights from these antioxidants having a phenol skeleton such that the molecular weight Ma of antioxidant A is 50 g / mol or more and 1200 g / mol or less, and Ma < Mb for the molecular weight Ma of antioxidant A and the molecular weight Mb of antioxidant B, an antioxidant with more excellent dispersibility in low-density polyethylene can be obtained, bleeding out of the antioxidant is more preferably suppressed, and thermal degradation of low-density polyethylene tends to be more preferably suppressed.

[0049] (Content of antioxidant A Wa) As shown in the above <Condition (D)>, the content Wa of the antioxidant A in the composition is 5 ppm or more and 450 ppm or less. The lower limit is preferably 10 ppm or more, more preferably 15 ppm or more, and even more preferably 20 ppm or more. The upper limit is preferably 425 ppm or less, more preferably 400 ppm or less, and even more preferably 375 ppm or less.

[0050] The content Wa is the amount of antioxidant A, which has a smaller molecular weight, added between the two antioxidants. Antioxidant A, which has a smaller molecular weight, is prone to bleeding out, but has excellent dispersibility, so has a high radical scavenging function and tends to be more effective in suppressing thermal degradation of low-density polyethylene. If the molecular weight Wa is within the above range, it is preferable because it is more effective in suppressing thermal degradation of low-density polyethylene and tends to further reduce the amount of bleeding out.

[0051] (Wa / Wb value) As shown in the above <Condition (E)>, the value of the content Wa (ppm) of antioxidant A relative to the content Wb (ppm) of antioxidant B in the composition (Wa / Wb) is preferably 0.05 or more and 0.45 or less. The lower limit is more preferably 0.07 or more, even more preferably 0.10 or more, and even more preferably 0.12 or more. The upper limit is more preferably 0.42 or less, even more preferably 0.40 or less, and even more preferably 0.37 or less.

[0052] When the Wa / Wb value is within the above range, the balance of the contents of the two antioxidants A and B is more suitable, and there is a tendency for the suppression of thermal degradation of low-density polyethylene to be more excellent while further suppressing bleed-out. When the Wa / Wb value is 0.50 or more, the content ratio of antioxidant A is high, and the antioxidant A having a low molecular weight tends to bleed out easily. When the Wa / Wb value is less than 0.05, the content ratio of antioxidant A is low, and there is a tendency for the suppression of thermal degradation of low-density polyethylene to be insufficient.

[0053] (Molecular weight Ma of antioxidant A and difference (Mb-Ma)) As shown in the above <Condition (F)>, it is preferable that the molecular weight Ma of antioxidant A is 50 ppm or more and 600 ppm or less, and the difference (Mb-Ma) between the molecular weight Mb of antioxidant B and the molecular weight Ma of antioxidant A is 100 g / mol or more and 1500 g / mol or less. The lower limit of the difference (Mb-Ma) is more preferably 150 g / mol or more, even more preferably 200 g / mol or more, and even more preferably 250 g / mol or more. The upper limit is more preferably 1400 g / mol or less, even more preferably 1300 g / mol or less, and even more preferably 1200 g / mol or less.

[0054] When the difference (Mb-Ma) is within the above range, the difference in molecular weight between the two antioxidants A and B becomes more sufficient, and there is a tendency that the bleed-out of the antioxidants can be further suppressed while the thermal degradation of the low-density polyethylene can be further suppressed. In addition, when the difference (Mb-Ma) is within the above range, the antioxidants A and B can be mixed more suitably, and therefore there is a tendency that a low-density polyethylene composition having even more excellent high-speed film-forming properties can be obtained.

[0055] The combination of antioxidants A and B in which the molecular weight Ma of antioxidant A is within the above range and the difference (Mb-Ma) is within the above range can be arbitrarily selected from the examples of antioxidants having a phenol skeleton described above.

[0056] Examples of such combinations include, as antioxidants A and B, 2,6-di-t-butyl-4-methylphenol and 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 2,6-di-t-butyl-4-methylphenol and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-4-methylphenol and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 2,6-di-t-butyl-4-methylphenol and acrylic acid 2-[1-(2 -Hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl, 2,6-di-t-butyl-4-methylphenol and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylenebis(oxyethylene), 2,6-di-t-butyl-4-methylphenol and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2,6-di-t-butyl-4-methylphenol and N,N'-(1,6-hexanediyl)bis[3,5-bis (1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 2,6-di-t-butyl-4-methylphenol and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,6-di-t-butyl-4-methylphenol and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 2,6-di-t-butyl-4-methylphenol and 3,9-bis{1,1-dimethyl- 2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 2,6-di-t-butyl-4-methylphenol and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 2,6-di-t-butyl-4-methylphenol and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 2,6-di-t-butyl-4-methylphenol and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butyl 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene), 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 4,4'-butyl 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2] dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and N,N '-(1,6-Hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxadiyl} 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane; 3,5-di-t-butyl-4-hydroxyphenyl)propionate and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t -butyl-4-hydroxybenzyl)benzene, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,1,3-Tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 1,1,3-tris(2-methyl-4-hydroxy- 5-t-butylphenyl)butane and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],

[0057] 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methyl 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxybenzyl)benzene}-2,4,8,10-tetraoxaspiro[5,5]ethyl]-4,6-di-t-pentylphenyl acrylate; hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoate)ethylene bis(oxyethylene) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5 -methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5], bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene) and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5], 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butyla Examples of such compounds include 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl), 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate].

[0058] Antioxidants A and B include 2,6-di-t-butyl-4-methylphenol and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-4-methylphenol and N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 2,6-di-t-butyl-4-methylphenol and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and pentaerythritoltetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] are preferred. By using these antioxidants A and B, there is a tendency that the bleed-out of the antioxidants can be further suppressed while the thermal degradation of the low-density polyethylene can be further suppressed.

[0059] (Absolute value of the difference in melting points between antioxidants A and B) As shown in the above <Condition (G)>, the absolute value of the difference between the melting point Tga (°C) of antioxidant A and the melting point Tgb (°C) of antioxidant B (|Tga-Tgb|) is preferably 59°C or less. The upper limit is more preferably 54°C or less, even more preferably 49°C or less, and even more preferably 44°C or less. The lower limit is not particularly limited, and is, for example, 0°C or more, may be 5°C or more, or may be 10°C or more.

[0060] In this embodiment, the melting point (° C.) of the antioxidant can be measured, for example, by DSC (differential scanning calorimeter).

[0061] When the absolute value of the difference in melting points is within the above range, the antioxidant having a higher melting point does not solidify first in the step of melting and cooling the low-density polyethylene composition for molding, and the two types of antioxidants tend not to separate, which tends to further suppress the bleed-out of the antioxidants.

[0062] The combination of antioxidants A and B such that the absolute value of the difference in melting points falls within the above range can be arbitrarily selected from the examples of antioxidants having a phenol skeleton given above.

[0063] Examples of such combinations include, as antioxidants A and B, 2,6-di-t-butyl-4-methylphenol and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-4-methylphenol and 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, and 2,6-di-t-butyl-4-methylphenol and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoate)ethylenebis(oxyethylene) 2,6-di-t-butyl-4-methylphenol and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2,6-di-t-butyl-4-methylphenol and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,6-di-t-butyl-4-methylphenol and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 2,6-di-t-butyl-4-methylphenol and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 2,6-di-t-butyl-4-methylphenol and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxypentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 4,4'- Butylidenebis(3-methyl-6-t-butylphenol) and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 4,4'-butylidenebis(3-methyl-6-t-butylphenol) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylenebis(oxyethylene), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, Decyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate,

[0064] 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoate)ethylene bis(oxyethylene), 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2-[1-(2- 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide], 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2-methylphenol; 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2-methylphenol; ,4,8,10-Tetraoxaspiro[5,5]undecane, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoate) ethylene bis(oxyethylene) and 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-Triazine, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene) and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid) ethylene bis(oxyethylene) and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, bis(3-t-butyl 2,4-bis(n-octyl)-4-hydroxy-5-methylbenzenepropanoic acid)ethylene bis(oxyethylene) and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylene bis(oxyethylene) and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octyl) 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, 2,4-bis(n-octylthio) (O)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5], 2,4-bis(n-octylthio)-6-(4'-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-(1,6-Hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide] and 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol, N,N'-(1,6-Hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide] and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propanamide} pionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, N,N'-(1,6-hexanediyl)bis[3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanamide] and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol and 3,9-bis{1,1 -Dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 6-t-butyl-4-{3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}-2-methylphenol and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4 -hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and 3,9-bis{1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate.

[0065] The antioxidants A and B are 2,6-di-t-butyl-4-methylphenol and pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,6-di-t-butyl-4-methylphenol and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]. Preferred are octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoate)ethylene bis(oxyethylene), and acrylic acid 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl and thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]. By using these antioxidants A and B, the two antioxidants tend to be even less likely to separate, so that bleed-out can be further suppressed and the suppression of thermal degradation of low-density polyethylene tends to be even more excellent.

[0066] [Method for producing low-density polyethylene composition] The method for producing the low-density polyethylene composition of the present embodiment is not particularly limited, and examples thereof include a high-pressure radical polymerization method, a gas phase method, a solution method, and a slurry method. Among these, it is preferable to produce the low-density polyethylene composition by a high-pressure radical polymerization method. By using the high-pressure radical polymerization method, there is a tendency that a metal catalyst is not used, and that the solvent, unreacted monomer and oligomer components, etc. are removed by a high-pressure separator. Therefore, there is a tendency that the thermal stability is excellent, and contamination of the adherend can be more suitably prevented.

[0067] The low-density polyethylene of the present embodiment can be obtained by radical polymerization of ethylene using, for example, an autoclave type reactor or a tubular type reactor, although the method is not particularly limited thereto.

[0068] When an autoclave type reactor is used, the polymerization conditions are usually set to a temperature of 200° C. to 300° C. and a polymerization pressure of 100 MPa to 250 MPa in the presence of a peroxide. When a tubular type reactor is used, the polymerization conditions are usually set to a temperature of 180° C. to 400° C. and a polymerization pressure of 100 MPa to 400 MPa in the presence of a peroxide.

[0069] The weight average molecular weight, number average molecular weight, density, molecular weight distribution, and molecular structure of the obtained low density polyethylene can be appropriately controlled by the polymerization temperature, polymerization pressure, type of peroxide, and the presence or absence of a chain transfer agent. In general, when the polymerization pressure is set high, the weight average molecular weight tends to increase, and when the polymerization pressure is set low, the weight average molecular weight tends to decrease. In addition, the addition of a chain transfer agent can suppress the branching reaction, so that the density tends to increase and the weight average molecular weight tends to decrease.

[0070] The peroxide is not particularly limited, but examples thereof include methyl ethyl ketone peroxide, peroxyketals (specifically, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl 4,4-bis(t-butylperoxy)valerate, and 2,2-bis(t-butylperoxy)butane, etc.), hydroperoxides (specifically, t-butyl hydroperoxy side, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide, etc.), dialkyl peroxides (specifically, di-t-butyl peroxide, dicumyl peroxide, bis(t-butylperoxyisopropyl)benzene, t-butylcumyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyldi(t-butyl peroxy)hexane-3, etc.), diacyl peroxides (specifically, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, etc.), peroxydicarbonates (specifically, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, dimethoxy Diisopropyl peroxydicarbonate, di(3-methyl-3-methoxybutyl peroxydicarbonate, diallyl peroxydicarbonate, etc.), peroxyesters (specifically, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxyoctate, t-butyl peroxyneodecanoate, cumyl peroxyneodecanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-3,5,6-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl carbonate, cumyl peroxyoctoate, t-hexyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxyneohexanoate, t-hexyl peroxyneohexanoate, cumyl peroxyneohexanoate, etc.), acetylcyclohexylsulfonyl peroxide, and t-butyl peroxyallyl carbonate. The peroxide may be used alone or in combination of two or more. Among them, the peroxide is preferably a peroxy ester, and more preferably at least one selected from the group consisting of t-butyl peroxyacetate and t-butyl peroxy-2-ethylhexanoate.

[0071] The chain transfer agent is not particularly limited, and examples thereof include hydrocarbon compounds such as propane, propylene, butane, etc. By using the chain transfer agent, radicals of a growing polymer can be terminated, and various physical properties can be adjusted.

[0072] The low-density polyethylene polymerized in the reactor is separated into unreacted ethylene gas and polymer components by a gas separation device adjusted to an arbitrary pressure. A plurality of gas separation devices may be connected, and usually, two or more gas separation devices are installed from the viewpoint of safety.

[0073] The low-density polyethylene from which the unreacted ethylene gas component has been separated is charged in a molten state into an extruder and processed into pellets. The extruder is not particularly limited, but examples thereof include single-screw extruders, twin-screw extruders, vent extruders, tandem extruders, and extruders having other special structures. Among these, the single-screw extruder is preferred as the extruder since it tends to be able to further suppress shear heat generation in the low-density polyethylene and further suppress thermal degradation.

[0074] The low-density polyethylene composition of the present embodiment contains an antioxidant A having a phenol skeleton and an antioxidant B having a phenol skeleton other than the antioxidant A. The antioxidants A and B may or may not be mixed in advance. The mixing method is not particularly limited, and examples thereof include a method of mixing the antioxidants A and B in a solid state, and a method of heating the antioxidants A and B to a melting point or higher and mixing them in a molten state. Among these, the method of heating the antioxidants A and B to a melting point or higher and mixing them in a molten state is preferred because the antioxidants A and B are mixed at the molecular level, and therefore bleed-out tends to be further suppressed.

[0075] The method for mixing the antioxidants A and B in the low-density polyethylene is not particularly limited, and examples thereof include a method of adding the antioxidants A and B to raw ethylene gas, a method of adding the antioxidants A and B to molten low-density polyethylene, a method of mixing low-density polyethylene pellets with the antioxidants A and B by melt kneading, and a method of dissolving the low-density polyethylene in a solution and adding the antioxidants A and B to the solution.

[0076] The production method for the low-density polyethylene composition of the present embodiment preferably includes a first mixing step of mixing antioxidant A and antioxidant B in a molten state, and a second mixing step of mixing the molten mixture obtained in the first mixing step with a molten low-density polyethylene. By going through such steps, the low-density polyethylene composition of the present embodiment tends to be produced more preferably.

[0077] Examples of methods for bringing the low-density polyethylene into a molten state include a method using molten low-density polyethylene polymerized in a polymerization reactor, and a method of applying heat to pellets of low-density polyethylene.

[0078] The method of adding the antioxidants A and B to the polymerized low-density polyethylene in a molten state is preferable because the antioxidants A and B can be easily added uniformly to the low-density polyethylene, there is little risk of them being separated together with the gas components, and the antioxidants can be added during continuous production.

[0079] (Additives) The low-density polyethylene composition of the present embodiment may contain, as necessary, additives other than the low-density polyethylene, antioxidant A, and antioxidant B. Examples of such additives include phosphorus-based antioxidants, sulfur-based antioxidants, light stabilizers, slip agents, fillers, and antistatic agents.

[0080] [Molded body] The molded article of the present embodiment is a molded article of the low-density polyethylene composition of the present embodiment. Examples of the molded article of the present embodiment include a film. When the film is a multi-layer film, the molded article of the low-density polyethylene composition of the present embodiment may be used as the outermost layer or as an intermediate layer. Specific applications of the film include a surface protection film. EXAMPLES

[0081] The present embodiment will be described in detail below with specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples. The measurement and evaluation methods for each physical property and characteristic are described below. The measurements and evaluations were performed at room temperature unless otherwise specified.

[0082] [Methods for measuring physical properties] (Physical property 1) Melt flow rate (MFR) at 190℃ and 2.16kg load For each of the low-density polyethylene compositions and the high-density polyethylene compositions obtained in the Examples and Comparative Examples, the melt flow rate (g / 10 min) was measured according to JIS K7210 Code D:1999 (temperature = 190°C, load = 2.16 kg).

[0083] (Physical properties 2) Density The density (kg / m) of each of the low-density polyethylene compositions and the high-density polyethylene compositions obtained in the examples and comparative examples was measured by the density gradient tube method (23°C) according to JIS K7112:1999. 3 ) was measured.

[0084] [Evaluation method] (Evaluation 1) Suppression of thermal degradation The melt flow rate (g / 10 min) of each of the low-density polyethylene compositions and the high-density polyethylene compositions obtained in the Examples and Comparative Examples was measured at a temperature of 230°C and a load of 2.16 kg using a melt flow rate measuring device conforming to JIS K7210 Code D:1999. The strand samples prepared by the measurement were then cut into pellets with scissors, and the melt flow rate (g / 10 min) was measured again under the same conditions. This was repeated five times, and the first measurement value was designated MFR1 and the fifth measurement value was designated MFR5. The ratio of these values, MFR5 / MFR1, was taken as the MFR retention. This retention was used as an index of suppression of thermal degradation and was evaluated according to the following criteria.

[0085] <Evaluation criteria> ◎: 0.80 or higher ○: 0.70 or more and less than 0.80 △: 0.60 or more and less than 0.70 ×: Less than 0.60

[0086] (Evaluation 2) Staining of the substrate Each of the low-density polyethylene compositions and the high-density polyethylene compositions obtained in the Examples and Comparative Examples was molded using a T-die film forming machine (HM40N (product name) manufactured by Hokushin Sangyo Co., Ltd., screw diameter 40 mm, die width 300 mm) at a cylinder temperature of 230°C, a die temperature of 210°C, an extrusion rate of 5 kg / hour, an air gap of 10 cm, and a take-up speed of 9 m / min, and both ends were trimmed by 50 mm to obtain a film having a thickness of 35 μm. The obtained film was cut to a size of 5 cm wide x 5 cm long, placed on a new slide glass of 7.6 cm wide x 2.6 cm long without trapping air bubbles, and fixed at the four corners with cellophane tape to prepare a sample. This sample was subjected to an evaluation test of the residue after high-temperature processing. The sample was placed in an oven set at 60°C, 2 atm, and 100% RH, and was left there for 24 hours before being removed. After 1 minute, the film was peeled off with tweezers, and the surface of the 5 cm wide x 2.6 cm long slide where the film and the slide were in contact was visually observed, and the residue after high-temperature processing was evaluated according to the following criteria.

[0087] <Evaluation criteria> : No residue was observed within the observation area. ◯: Residue was observed in less than 20% of the observation area. △: Residue was observed in 20% or more and less than 40% of the observation area. ×: Residue was observed in 40% or more of the observation area.

[0088] (Evaluation 3) High-speed film formation Each of the low-density polyethylene compositions and high-density polyethylene compositions obtained in the Examples and Comparative Examples was processed into a film using an extruder having a screw diameter of 65 mm and L / D=30, and a die adjusted to a width of 400 mm, under conditions of a temperature of 320°C, an extrusion resin amount of 60 kg / hour, and an air gap of 13 cm. With the extrusion resin amount kept constant, the take-up processing speed was gradually increased, and the take-up processing speed at which the film-like resin dropping from the die broke was defined as the breaking speed. The breaking speed was evaluated according to the following criteria as an index of high-speed film-formability.

[0089] <Evaluation criteria> ◎: Breaking speed exceeds 450m / min ○: The breaking speed is more than 350 m / min and less than 450 m / min. ×: The breaking speed is 350 m / min or less.

[0090] [Antioxidants having a phenol skeleton used in the examples and comparative examples] Table 1 below shows the names (AO-1 to AO-8), types, molecular weights (g / mol), and melting points (° C.) of the antioxidants having a phenol skeleton used in the examples and comparative examples.

[0091] [Table 1]

[0092] <Example 1> AO-1 and AO-3 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:6, and heated to 150° C. to prepare a mixture of AO-1 and AO-3.

[0093] Ethylene gas was used as a raw material, and propylene was added at a ratio of 1.2 mol% to ethylene gas in an autoclave reactor at a polymerization temperature of 255°C and a polymerization pressure of 130.0 MPa, and a polymer was polymerized using t-butyl peroxyacetate as a polymerization initiator. Next, unreacted ethylene gas contained in the polymer in a molten state was separated in a gas separator adjusted to 50.0 MPa and 240°C. Furthermore, unreacted ethylene gas contained in the polymer in a molten state was separated in a gas separator adjusted to 2.0 MPa and 240°C.

[0094] To the molten polymer from which the unreacted gas had been separated, the mixed liquid of AO-1 and AO-3 was added so that the amount was 700 ppm based on the polymer mass. The mixture was then granulated using a single-screw extruder manufactured by Japan Steel Works, Ltd. (screw diameter 100 mm, L / D=24, L: distance from raw material supply inlet to discharge outlet (m), D: inner diameter of extruder (m); the same applies hereinafter) to obtain a pelletized low-density polyethylene composition.

[0095] <Example 2> AO-1 and AO-2 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:4, and heated to 100° C. to prepare a mixture of AO-1 and AO-2. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-1 and AO-2 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 1000 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0096] <Example 3> AO-2 and AO-4 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:5, and heated to 100° C. to prepare a mixture of AO-2 and AO-4. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-4 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 900 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 1.

[0097] <Example 4> AO-2 and AO-5 were placed in a heated vessel equipped with a stirrer in a mass ratio of 2:5, and heated to 100° C. to prepare a mixture of AO-2 and AO-5. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-5 was added to the molten polymer from which the gas had been separated so that the amount was 1400 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0098] <Example 5> AO-6 and AO-4 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:10, and heated to 130° C. to prepare a mixture of AO-6 and AO-4. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-6 and AO-4 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 880 ppm based on the polymer mass. Subsequently, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0099] <Example 6> AO-1 and AO-2 were placed in a heated vessel equipped with a stirrer in a mass ratio of 3:4, and heated to 100° C. to prepare a mixture of AO-1 and AO-2. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-1 and AO-2 was added to the molten polymer from which the gas had been separated so that the amount was 700 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0100] <Example 7> AO-1 and AO-3 were placed in a heated vessel equipped with a stirrer in a mass ratio of 3:5, and heated to 150° C. to prepare a mixture of AO-1 and AO-3.

[0101] Ethylene gas was used as a raw material, and in a tubular reactor, butane was added at a ratio of 20.4 mol% to ethylene gas at a polymerization temperature of 250°C and a polymerization pressure of 200.0 MPa, and a polymer was polymerized using t-butylperoxy-2-ethylhexanoate as a polymerization initiator. Next, unreacted ethylene gas contained in the polymer in a molten state was separated in a gas separator adjusted to 50.0 MPa and 240°C. Furthermore, unreacted ethylene gas contained in the polymer in a molten state was separated in a gas separator adjusted to 2.0 MPa and 240°C.

[0102] To the molten polymer from which the unreacted gas had been separated, the mixed liquid of AO-1 and AO-3 was added so as to give a concentration of 800 ppm relative to the polymer mass, and the mixture was then granulated using a single-screw extruder manufactured by Japan Steel Works, Ltd. (screw diameter: 100 mm, L / D=24) to obtain a pelletized low-density polyethylene composition.

[0103] <Example 8> AO-2 and AO-3 were placed in a heated vessel equipped with a stirrer in a mass ratio of 3:10, and heated to 150° C. to prepare a mixture of AO-2 and AO-3. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-3 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 650 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0104] <Example 9> AO-1 and AO-8 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:7, and heated to 160° C. to prepare a mixture of AO-2 and AO-3. A polymer was polymerized under the same conditions as in Example 7, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-3 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 400 ppm based on the polymer mass. Subsequently, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 1.

[0105] <Example 10> AO-2 and AO-7 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:2, and heated to 130° C. to prepare a mixture of AO-2 and AO-7. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-7 was added to the molten polymer from which the gas had been separated so that the amount was 600 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0106] <Example 11> AO-2 and AO-6 were placed in a heated vessel equipped with a stirrer in a mass ratio of 1:9, and heated to 130° C. to prepare a mixture of AO-2 and AO-6. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-6 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 1000 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0107] <Example 12> AO-2 and AO-5 were placed in a heated vessel equipped with a stirrer in a mass ratio of 7:6, and heated to 100° C. to prepare a mixture of AO-2 and AO-5. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-2 and AO-5 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 650 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0108] Table 2 below shows the physical properties and evaluation results of the low-density polyethylene compositions obtained in the examples.

[0109] [Table 2]

[0110] <Comparative Example 1> AO-1 was placed in a heated vessel equipped with a stirrer and heated to 100° C. to prepare a liquid. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then AO-1 was added to the molten polymer from which the gas had been separated so that the amount of AO-1 was 170 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0111] <Comparative Example 2> AO-2 was placed in a heated vessel equipped with a stirrer and heated to 100°C to prepare a liquid. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then AO-2 was added to the molten polymer from which the gas had been separated in an amount of 1500 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 1.

[0112] <Comparative Example 3> AO-2 was placed in a heated vessel equipped with a stirrer and heated to 100°C to prepare a liquid. A polymer was polymerized under the same conditions as in Example 1, and unreacted ethylene gas was separated. Then, AO-2 was added to the molten polymer from which the gas had been separated in an amount of 200 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 1.

[0113] <Comparative Example 4> AO-3 was placed in a heated vessel equipped with a stirrer and heated to 150°C to prepare a liquid. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then AO-3 was added to the molten polymer from which the gas had been separated in an amount of 400 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 1.

[0114] <Comparative Example 5> AO-7 was placed in a heated vessel equipped with a stirrer and heated to 150°C to prepare a liquid. A polymer was polymerized under the same conditions as in Example 7, and unreacted ethylene gas was separated. Then, AO-7 was added to the molten polymer from which the gas had been separated in an amount of 400 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained in the same manner as in Example 7.

[0115] <Comparative Example 6> AO-1 and AO-3 were placed in a heated vessel equipped with a stirrer in a mass ratio of 3:10, and heated to 150° C. to prepare a mixture of AO-1 and AO-3. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-1 and AO-3 was added to the molten polymer from which the gas had been separated so that the amount was 2600 ppm based on the polymer mass. Subsequently, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0116] <Comparative Example 7> AO-1 and AO-2 were placed in a heated vessel equipped with a stirrer in a mass ratio of 5:3, and heated to 100° C. to prepare a mixture of AO-1 and AO-2. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then a mixed liquid of AO-1 and AO-3 was added to the molten polymer from which the gas had been separated so that the amount of the mixed liquid was 800 ppm based on the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0117] <Comparative Example 8> AO-1 was placed in a heated vessel equipped with a stirrer and heated to 100° C. to prepare a liquid. A polymer was polymerized under the same conditions as in Example 1, unreacted ethylene gas was separated, and then AO-1 was added to the molten polymer from which the gas had been separated so that the amount of AO-1 was 1 ppm relative to the polymer mass. Then, a pellet-shaped low-density polyethylene composition was obtained by the same procedure as in Example 1.

[0118] <Comparative Example 9> The melt flow rate is 5g / 10min and the density is 947kg / m 3 Solid AO-1 and solid AO-3 were added at 450 ppm and 900 ppm to high-density polyethylene pellets not containing a phenol-based antioxidant (Creolex (registered trademark) T4750 (product name), manufactured by Asahi Kasei Corporation), and the mixture was melt-kneaded at a set temperature of 200°C using a twin-screw extruder (screw diameter 44 mm, L / D = 35) manufactured by Japan Steel Works, Ltd., to obtain a pellet-shaped high-density polyethylene composition.

[0119] <Comparative Example 10> The melt flow rate is 5g / 10min and the density is 947kg / m 3750 ppm of solid AO-1 and 150 ppm of solid AO-2 were added to high-density polyethylene pellets not containing a phenol-based antioxidant (Creolex (registered trademark) T4750 (product name), manufactured by Asahi Kasei Corporation), and the mixture was melt-kneaded at a set temperature of 200°C using a twin-screw extruder (screw diameter 44 mm, L / D = 35) manufactured by Japan Steel Works, Ltd., to obtain a pellet-shaped high-density polyethylene composition.

[0120] Table 3 below shows the physical properties and evaluation results of the low-density polyethylene compositions and high-density polyethylene compositions obtained in the comparative examples.

[0121] [Table 3]

[0122] As shown in Table 2, the low-density polyethylene composition of the present embodiment can provide a low-density polyethylene that is excellent in low-fouling properties to adherends and further excellent in high-speed film-formability while suppressing thermal degradation during processing, a molded article thereof, and a production method thereof.

[0123] As shown in Table 3, in Comparative Examples 1 to 5, only one type of antioxidant is contained, so the trade-off between suppression of thermal degradation and staining of the adherend cannot be resolved. In Comparative Examples 6 and 7, the content of antioxidant A exceeds 450 ppm, so the suppression of staining of the adherend is insufficient. In Comparative Example 8, only one type of antioxidant is contained, and the content of antioxidant A is less than 5 ppm, so the suppression of thermal degradation is insufficient. In Comparative Examples 9 and 10, high-density polyethylene is used, so the high-speed film-forming property is insufficient, and the content of antioxidant A exceeds 450 ppm, so the suppression of staining of the adherend is insufficient. [Industrial Applicability]

[0124] The low-density polyethylene composition of the present embodiment has industrial applicability as a raw material for film applications in which prevention of contamination of adherends and prevention of fisheyes are important, such as surface protection films and the like.

Claims

1. A low density polyethylene composition comprising a low density polyethylene and an antioxidant, The composition has a melt flow rate of 0.1 g / 10 min or more and 20.0 g / 10 min or less at 190° C. and a load of 2.16 kg, and a density of the composition is 910 kg / m 3 More than 935kg / m 3 is as follows: The antioxidant includes an antioxidant A having a phenol skeleton, and an antioxidant B having a phenol skeleton other than the antioxidant A, a molecular weight Ma of the antioxidant A is 50 g / mol or more and 1200 g / mol or less, and the molecular weight Ma and a molecular weight Mb of the antioxidant B satisfy the condition Ma<Mb; A low-density polyethylene composition, wherein a content Wa of the antioxidant A in the composition is 5 ppm or more and 450 ppm or less.

2. 2. The low-density polyethylene composition according to claim 1, wherein a value of the content Wa to the content Wb of the antioxidant B in the composition (Wa / Wb) is 0.05 or more and 0.45 or less.

3. 2. The low-density polyethylene composition according to claim 1, wherein the molecular weight Ma is 50 g / mol or more and 600 g / mol or less, and the difference between the molecular weight Mb and the molecular weight Ma (Mb-Ma) is 100 g / mol or more and 1500 g / mol or less.

4. The low-density polyethylene composition according to claim 1, wherein the absolute value of the difference between the melting point Tga of the antioxidant A and the melting point Tgb of the antioxidant B (|Tga-Tgb|) is 59°C or less.

5. A molded article of the low-density polyethylene composition according to any one of claims 1 to 4.

6. The molded article according to claim 5 , wherein the molded article is a film.

7. A method for producing a low-density polyethylene composition comprising a low-density polyethylene and an antioxidant, comprising the steps of: a first mixing step of mixing the antioxidant A and the antioxidant B in a molten state; a second mixing step of mixing the molten mixture obtained in the first mixing step with a molten low-density polyethylene, The composition has a melt flow rate of 0.1 g / 10 min or more and 20.0 g / 10 min or less at 190° C. and a load of 2.16 kg, and a density of the composition is 910 kg / m 3 More than 935kg / m 3 is as follows: The antioxidant includes an antioxidant A having a phenol skeleton, and an antioxidant B having a phenol skeleton other than the antioxidant A, a molecular weight Ma of the antioxidant A is 50 g / mol or more and 1200 g / mol or less, and the molecular weight Ma and a molecular weight Mb of the antioxidant B satisfy the condition Ma<Mb; The content Wa of the antioxidant A in the composition is 5 ppm or more and 450 ppm or less. Manufacturing method.

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