Polyethylene-based resin composition and extrusion molded foam

Abstract

To provide a polyethylene-based resin composition which is formed into a non-crosslinked polyethylene foam molding that has a high expansion ratio and excellent compression durability and secondary workability.SOLUTION: A polyethylene-based resin composition contains 50 to 90 wt.% of an ethylene-α-olefin copolymer (A) having a melt flow rate (hereinafter referred to as MFR) measured at 190°C and a load of 21.2 N of 0.5 g / 10 min or more and less than 10 g / 10 min and a density of 930 kg / m3 or more and 945 kg / m3 or less, 5 to 30 wt.% of high pressure method low density polyethylene (B) having an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min and a density of 925 kg / m3 or more and 935 kg / m3 or less, and 5 to 20 wt.% of an ethylenic polymer (C) having an MFR of 20 g / 10 min or more and less than 200 g / 10 min, wherein a density difference between the ethylene-α-olefin copolymer (A) and the high pressure method low density polyethylene (B) is 15 kg / m3 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyethylene resin composition, and more specifically to a polyethylene resin composition comprising a specific ethylene-α-olefin copolymer and a high-pressure low-density polyethylene, and a foam. [Background technology]

[0002] Polyethylene resin foams are widely used mainly for buffer materials, cushioning materials, shock absorbing materials, etc., and are roughly divided into non-crosslinked foams and crosslinked foams. In recent years, from the viewpoint of reducing environmental load, interest in improving the recyclability of plastic materials has been increasing, and the demand for non-crosslinking of crosslinked products is also increasing in polyethylene resin foams. When manufacturing a non-crosslinked polyethylene resin foam with a high expansion ratio, a polyethylene with a high melt tension is required, so it is known that a low-density polyethylene having long chain branches manufactured by a high-pressure method (hereinafter, high-pressure low-density polyethylene) is used. Non-crosslinked foams made of high-pressure low-density polyethylene are flexible and have excellent compression durability, so they are suitably used for applications in which they are repeatedly compressed (such as buffer materials), but have the disadvantage that the temperature range for molding is very narrow because of the sudden change in viscosity during secondary processing such as thermoforming. In order to solve such problems, it has been proposed to use a mixture of high-pressure low-density polyethylene and linear low-density polyethylene or high-density polyethylene (see, for example, Patent Documents 1 and 2). The present inventors have also found that ethylene-α-olefin copolymers that satisfy specific requirements have excellent foaming properties and extrusion foam moldability (see, for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-222222 [Patent Document 2] JP 2006-274038 A [Patent Document 3] JP 2006-096910 A [Patent Document 4] JP 2006-199872 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the methods proposed in the above Patent Documents 1 and 2 require the use of linear polyethylene that has low melt tension and does not exhibit foamability, and flexibility is lost during repeated compression, making it difficult to apply the methods to cushioning materials that are frequently subjected to compression. An object of the present invention is to overcome the drawbacks of the above prior art and provide a non-crosslinked polyethylene foam that has a high expansion ratio, excellent compression durability and secondary processability. [Means for solving the problem]

[0005] As a result of intensive research to solve the above problems, the present inventors have found that a specific polyethylene resin composition has excellent extrusion foamability, and that a non-crosslinked polyethylene foam having excellent heat resistance and flexibility can be obtained by extrusion foam molding of the polyethylene resin composition, and have thus completed the present invention. That is, the respective aspects of the present invention are as follows [1] to [5]. [1] A melt flow rate (MFR) measured at 190°C and a load of 21.2N is between 0.5g / 10min and 10g / 10min, and a density of 930kg / m 3 More than 945kg / m 3 The following ethylene-α-olefin copolymer (A) is 50-90% by weight, has an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min, and has a density of 925 kg / m 3 More than 935kg / m 3 A polyethylene resin composition comprising 5 to 30% by weight of the following high-pressure low-density polyethylene (B) and 5 to 20% by weight of an ethylene polymer (C) having an MFR of 20 g / 10 min or more and less than 200 g / 10 min, wherein the density difference between the ethylene-α-olefin copolymer (A) and the high-pressure low-density polyethylene (B) is 15 kg / m 3A polyethylene resin composition comprising: [2] The density of the ethylene polymer (C) is 900 kg / m 3 More than 945kg / m 3 The polyethylene resin composition according to [1], [3] The polyethylene resin composition according to [1] or [2], having a heat of fusion at 120°C or higher of 25 J / g or more. [4] A non-crosslinked extruded foam made from the polyethylene resin composition according to any one of [1] to [3]. [5] The non-crosslinked extruded foam according to [4], having a closed cell rate of 70% or more. Effect of the Invention

[0006] According to the present invention, it is possible to obtain a polyethylene resin composition for extrusion foam molding which can provide a foam having a high expansion ratio and excellent heat resistance and secondary processability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present invention will be described in detail below.

[0008] The polyethylene resin composition according to one embodiment of the present invention has an MFR of 0.5 g / 10 min or more and less than 10 g / 10 min and a density of 930 kg / m 3 More than 945kg / m 3 The following ethylene-α-olefin copolymer (A) is 50-90% by weight, has an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min, and has a density of 925 kg / m 3 More than 935kg / m 3 A polyethylene resin composition comprising 5 to 30% by weight of the following high-pressure low-density polyethylene (B) and 5 to 20% by weight of an ethylene polymer (C) having an MFR of 20 g / 10 min or more and less than 200 g / 10 min, wherein the density difference between the ethylene-α-olefin copolymer (A) and the high-pressure low-density polyethylene (B) is 15 kg / m 3 The polyethylene resin composition is as follows:

[0009] The ethylene-α-olefin copolymer (A) has an MFR of 0.5 g / 10 min or more and less than 10 g / 10 min and a density of 930 kg / m 3 More than 950kg / m 3 Any ethylene-α-olefin copolymer may be used so long as it falls within the category of ethylene-α-olefin copolymers described below.

[0010] The MFR of the ethylene-α-olefin copolymer (A) is 0.5 g / 10 min or more and less than 10 g / 10 min, preferably 0.7 g / 10 min or more and less than 8.0 g / 10 min. If the MFR is less than 0.5 g / 10 min, the load on the extruder increases when molding into a polyethylene resin composition, resulting in reduced productivity. On the other hand, if the MFR is 10 g / 10 min or more, the polyethylene resin composition will be inferior in foamability and mechanical strength.

[0011] The density of the ethylene-α-olefin copolymer (A) is 930 kg / m 3 More than 950kg / m 3 The density is 950kg / m 3 If the density exceeds 930 kg / m, the compatibility of the polyethylene resin composition obtained by blending with the high-pressure low-density polyethylene is poor, and when the composition is extruded into a foam, the cells are united, and the foam does not have uniform and fine cells, resulting in a foam that is inferior in compression durability. 3 If it is less than this, the resulting polyethylene resin composition will have excellent flexibility but poor heat resistance.

[0012] Examples of ethylene-α-olefin copolymers (A) that satisfy the above requirements include (trade name) Nipolon-L M50 (manufactured by Tosoh Corporation), (trade name) Nipolon-Z ZF260 (manufactured by Tosoh Corporation), and (trade name) TOSOH-HMS 10S65B.

[0013] High-pressure low-density polyethylene (B) has an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min and a density of 925 kg / m 3 More than 935kg / m 3Any of the following high-pressure low-density polyethylenes may be used as long as they are low-density polyethylenes produced by a high-pressure process.

[0014] The high-pressure low-density polyethylene (B) has an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min, preferably 0.3 g / 10 min or more and less than 8.0 g / 10 min, so that the load on the extruder when molded into a polyethylene resin composition is small and the polyethylene resin composition has excellent foamability and mechanical strength.

[0015] In addition, the compatibility with the ethylene-α-olefin copolymer (A) is improved, resulting in a polyethylene resin composition with high melt tension, excellent extrusion foamability, and excellent heat resistance, and a density of 925 kg / m 3 More than 935kg / m 3 less than 930 kg / m 3 More than 935kg / m 3 Here, the high-pressure low-density polyethylene (B) and the ethylene-α-olefin copolymer (A) have extremely good compatibility with each other, and a polyethylene-based resin composition that can be easily foamed is obtained, so the density difference is 15 kg / m 3 less than 10 kg / m 3 The following is the result.

[0016] Examples of the high-pressure low-density polyethylene (B) that satisfies the above-mentioned requirements include (trade name) Petrothene 220K (manufactured by Tosoh Corporation), (trade name) Petrothene 219 (manufactured by Tosoh Corporation), and (trade name) Petrothene 221.

[0017] The ethylene polymer (C) may be any ethylene polymer as long as it belongs to the category of ethylene polymers having an MFR of 20 g / 10 min or more and less than 200 g / 10 min. Examples of such ethylene polymers include high-pressure low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer. In particular, high-pressure low-density polyethylene is preferred because it gives a polyethylene resin composition with excellent moldability.

[0018] The ethylene polymer (C) has an MFR of 20 g / 10 min or more and less than 200 g / 10 min, preferably 20 g / 10 min or more and less than 150 g / 10 min, so that the load on the extruder is small when molding into a polyethylene resin composition and the polyethylene resin composition has extremely excellent foamability.

[0019] The density of the ethylene polymer (C) is 900 kg / m because it becomes a flexible foam. 3 More than 945kg / m 3 It is preferable that the content is equal to or less than 900 kg / m 3 More than 925kg / m 3 It is preferable that:

[0020] Examples of ethylene polymers (C) that satisfy the above requirements include (trade name) Petrothene 219 (manufactured by Tosoh Corporation), (trade name) Petrothene 221 (manufactured by Tosoh Corporation), and (trade name) Ultrathene 526 (manufactured by Tosoh Corporation).

[0021] In the polyethylene resin composition, the content of the ethylene-α-olefin copolymer (A), the high-pressure low-density polyethylene (B) and the ethylene polymer (C) is 90-50% by weight, preferably 90-40% by weight, of the ethylene-α-olefin copolymer (A). If the content exceeds 90% by weight, the foamability is poor. On the other hand, if the content is less than 50% by weight, the heat resistance is poor. The content of the high-pressure low-density polyethylene (B) is 5-30% by weight, preferably 10-25% by weight. If the content exceeds 30% by weight, the heat resistance is impaired. On the other hand, if the content is less than 5% by weight, the foam moldability is poor. The content of the ethylene polymer (C) is 5-20% by weight, preferably 5-15% by weight. If the content exceeds 20% by weight, bubbles grow in the die, making molding difficult. On the other hand, if the blending amount is less than 5% by weight, the foam moldability is poor. Here, (A), (B) and (C) are mixed so that the total amount of each is 100% by weight.

[0022] The above resin composition may contain components other than the ethylene-α-olefin copolymer (A), the high-pressure low-density polyethylene (B) and the ethylene polymer (C) as long as the effects of the present invention are not impaired.

[0023] The polyethylene resin composition has a high closed cell ratio and a high expansion ratio, and therefore has an MFR of 0.8 g / 10 min or more and less than 6 g / 10 min and a density of 925 kg / m 3 More than 935kg / m 3 and the melt tension is preferably 30 mN or more and less than 80 mN.

[0024] Since the polyethylene resin composition is a resin composition with excellent heat resistance, it is preferable that the heat of fusion at 120° C. or higher as measured by DSC is 25 J / g or more.

[0025] The polyethylene resin composition can be obtained by mixing the ethylene-α-olefin copolymer (A), the high-pressure low-density polyethylene (B) and the ethylene polymer (C) by a conventionally known method, for example, by using a Henschel mixer, a V-blender, a ribbon blender, a tumbler blender or the like, or by melt-kneading the mixture obtained by such a method using a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer or the like, and then granulating the mixture.

[0026] The polyethylene resin composition may contain known additives such as a heat stabilizer, a weather stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, a nucleating agent, a pigment, an inorganic filler or reinforcing agent such as carbon black, talc, glass powder or glass fiber, an organic filler or reinforcing agent, a flame retardant, and a neutron shielding agent.

[0027] The polyethylene resin composition can be extruded without the addition of a crosslinking agent to produce a non-crosslinked extruded foam having excellent heat resistance. If the extruded foam has a closed cell ratio of 70% or more, the foam has excellent compression durability, which is preferable.

[0028] The non-crosslinked extrusion foam molded product, which is one aspect of the present invention, is a foam made of the above polyethylene resin composition. Any method may be used as the manufacturing method of the above foam as long as a foam can be obtained. For example, a method in which a polyethylene resin composition and a bubble regulator such as talc, a shrinkage inhibitor, etc., which are added as necessary, are fed to an extruder, heated and melted, kneaded, and a foaming agent is further fed to form a foamable molten resin mixture, and then the extrusion resin temperature, the internal pressure of the extrusion die, the discharge amount, etc. are adjusted, and the mixture is extruded into a low pressure region from a die attached to the tip of the extruder to be foamed. In addition, by selecting a die to be attached to the tip of the extruder according to the shape of the desired foam, extruded foams of various shapes such as a round rod-shaped foam, a sheet-shaped foam, and a plate-shaped foam can be manufactured. For example, a round rod-shaped foam can be obtained by attaching a strand die, a sheet-shaped foam can be obtained by attaching an annular die, and a plate-shaped foam can be manufactured by attaching a slit die.

[0029] The foam made of the polyethylene resin composition can be formed by feeding the polyethylene resin composition, additives, foaming agent, etc. to an extruder, heating and melting kneading the mixture to obtain a foamable molten resin mixture, and then extruding the mixture from the extruder into a low pressure region while adjusting the extrusion resin temperature within an appropriate range. The specific extrusion resin temperature is preferably adjusted to within the range of (melting point of polyethylene resin composition -10°C) to (melting point of polyethylene resin composition +10°C) based on the melting point of the polyethylene resin composition, and more preferably adjusted to within the range of (melting point of polyethylene resin composition -5°C) to (melting point of polyethylene resin composition +5°C). The melting point of the polyethylene resin composition is the apex temperature of the peak determined from a test piece subjected to a certain heat treatment according to JIS K7121 (1987) using a heat flux DSC curve. Examples of the foaming agent used in the extrusion foam molding include inorganic gas foaming agents such as carbon dioxide, nitrogen, argon, and air; volatile foaming agents such as propane, butane, pentane, hexane, cyclobutane, cyclohexane, trichlorofluoromethane, and dichlorodifluoromethane; and chemical foaming agents that are liquid or solid at room temperature and generate gas when heated, such as azodicarbonamide, barium azodicarboxylate, N,N-dinitrosopentamethylenetetramine, 4,4'-oxybis(benzenesulfonylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide, p-toluenesulfonylsemicarbazide, trihydrazinotriazine, biurea, and zinc carbonate. The amount of the foaming agent added is preferably 1 to 20 parts by weight, and particularly preferably 3 to 15 parts by weight, per 100 parts by weight of the polyethylene resin composition.

[0030] The foam has a high expansion ratio, excellent compression durability and secondary processability, and can be used for applications such as heat retaining materials and building materials. EXAMPLES

[0031] The present invention will be described in more detail below by showing examples, but the present invention is not limited to these examples.

[0032] The measurement methods used in the examples and comparative examples are shown below.

[0033] ~MFR measurement~ The measurement was performed in accordance with JIS K6922-1 at a temperature of 190°C and a load of 2.16 kg.

[0034] ~Density~ The measurement was performed by the density gradient tube method in accordance with JIS K6922-1.

[0035] ~Melt tension measurement~ A Capilograph (manufactured by Toyo Seiki Seisakusho) was used. At 190°C, a strand was lowered from a die having a length (L) of 8 mm and a diameter (D) of 2.095 mm at a piston lowering speed of 10 mm / min, and taken up at 10 m / min. The take-up load was taken as the melt tension.

[0036] ~Evaluation of physical properties and moldability of extruded foam sheets~ ~Foaming ratio~ A foam having a width of 5 cm, a length of 5 cm, and a thickness of 3 mm was cut out from the extruded foam sheet obtained by molding the polyethylene resin composition, and the weight (Wg) of the foam was measured. The apparent density was calculated according to the following formula in accordance with JIS K 6767.

[0037] Apparent density (g / cm 3 )=W / (5×5×0.3) The expansion ratio was calculated from the apparent density using the following formula.

[0038] Expansion ratio = 1 / apparent density ~Foam sheet properties~ The appearance of the extruded foam sheet obtained by molding the polyethylene resin composition and the state of bubbles in the cross section were visually evaluated.

[0039] ○: Smooth foam surface, uniform cell structure △: Smooth surface foam shape, uneven bubble state ×: Uneven foam shape, non-uniform bubble state ~Residual crystal fusion heat~ A foam was cut out from an extruded foam sheet obtained by molding a polyethylene resin composition, and heated at a rate of 10°C / min using a heat flux type differential scanning calorimeter (DS7000X, Hitachi High-Tech Science Co., Ltd.) From the obtained DSC curve, the heat of fusion at a temperature of 120°C or higher was calculated.

[0040] Example 1 (1) Production of polyethylene resin composition Ethylene-α-olefin copolymer (A) is available under the trade name Nipolon-L M50 (MFR 3.0g / 10min, density 936kg / m 3 (B) high-pressure low-density polyethylene (Petrothene 220K, manufactured by Tosoh Corporation, MFR 3.0 g / 10 min, density 931 kg / m 3 The ethylene polymer (C) was Petrothene 208, manufactured by Tosoh Corporation, with a MFR of 24 g / 10 min and a density of 924 kg / m 3 These were dry-blended in a ratio of 70:20:10 (wt%) and melt-mixed in a 30 mm diameter single screw extruder manufactured by IKG Co. The barrel temperatures were C1: 180°C, C2: 200°C, C3: 210°C, and die head: 210°C. (2) Production of foamed products made from polyethylene resin compositions A sodium bicarbonate-based chemical foaming agent (product name: Panthren H2610, manufactured by Eiwa Chemical Industry Co., Ltd.) was dry-blended in a ratio of 3 parts by weight as a foaming agent with 100 parts by weight of the above polyethylene resin composition, and a sheet-shaped foamed molded product was extruded using an FS50 sheet molding machine manufactured by Ikegai Co., Ltd. (slit die) with a lip opening of 1 mm, with the die temperature set to 160°C.

[0041] The resulting polyethylene resin composition had an MFR of 2.6 g / 10 min and a density of 933 kg / m 3 The melt tension was 48 mN. The obtained extruded polyethylene foam sheet had a high surface smoothness and uniform fine cells, and the expansion ratio was 3.6 times and the closed cell ratio was 83%. The melting point of the polyethylene resin composition was 123°C, and the heat of fusion at 120°C or higher was 35 J / g. The results are shown in Table 1.

[0042] Example 2 Ethylene-α-olefin copolymer (A) is available under the trade name Nipolon-Z ZF260 (MFR 2.0g / 10min, density 936kg / m 3 (B) high-pressure low-density polyethylene (Petrothene 220K, manufactured by Tosoh Corporation, MFR 3.0 g / 10 min, density 931 kg / m 3 The ethylene polymer (C) was Petrocene 248, manufactured by Tosoh Corporation, with a MFR of 58 g / 10 min and a density of 917 kg / m 3 The mixture was dry-blended in a ratio of 60:20:20 (wt %) and molded into an extruded foam sheet in the same manner as in Example 1.

[0043] The resulting polyethylene resin composition had an MFR of 2.4 g / 10 min and a density of 933 kg / m 3 The melt tension was 62 mN.

[0044] The obtained extruded polyethylene foam sheet had a high surface smoothness and uniform fine cells, and the expansion ratio was 3.8 times and the closed cell ratio was 85%. The melting point of the polyethylene resin composition was 123°C, and the heat of fusion at 120°C or higher was 25 J / g. The results are shown in Table 1.

[0045] Example 3 Ethylene-α-olefin copolymer (A) is available under the trade name Nipolon-Z ZF260 (MFR 2.0g / 10min, density 936kg / m 3 (B) high-pressure low-density polyethylene (Petrothene 220K, manufactured by Tosoh Corporation, MFR 3.0 g / 10 min, density 931 kg / m 3 The ethylene polymer (C) is Petrothene 353, manufactured by Tosoh Corporation, with a MFR of 145 g / 10 min and a density of 915 kg / m 3 The above components were dry-blended in a ratio of 60:30:10 (wt %), and an extruded foam sheet was formed in the same manner as in Example 1.

[0046] The resulting polyethylene resin composition had an MFR of 2.0 g / 10 min and a density of 932 kg / m 3 The melt tension was 65 mN.

[0047] The obtained extruded polyethylene foam sheet had a high surface smoothness and uniform fine cells, and the expansion ratio was 3.8 times and the closed cell ratio was 84%. The melting point of the polyethylene resin composition was 123°C, and the heat of fusion at 120°C or higher was 25 J / g. The results are shown in Table 1.

[0048] Example 4 As the ethylene-α-olefin copolymer (A), the product name TOSOH-HMS 10S65B (MFR 1.8g / 10min, density 941kg / m 3 (B) high-pressure low-density polyethylene (Petrothene 220K, manufactured by Tosoh Corporation, MFR 3.0 g / 10 min, density 931 kg / m 3 The ethylene polymer (C) was Petrothene 248, manufactured by Tosoh Corporation, with a MFR of 58 g / 10 min and a density of 917 kg / m 3 The mixture was dry-blended in a ratio of 80:10:10 (wt %) and molded into an extruded foam sheet in the same manner as in Example 1.

[0049] The resulting polyethylene resin composition had an MFR of 3.0 g / 10 min and a density of 934 kg / m 3 The melt tension was 35 mN.

[0050] The obtained extruded polyethylene foam sheet had a high surface smoothness and uniform fine cells, and the expansion ratio was 3.6 times and the closed cell ratio was 81%. The melting point of the polyethylene resin composition was 123°C, and the heat of fusion at 120°C or higher was 47 J / g. The results are shown in Table 1.

[0051] Comparative Example 1 High-pressure low-density polyethylene (B) is available under the trade name Petrothene 360, manufactured by Tosoh Corporation, with a MFR of 1.9 g / 10 min and a density of 919 kg / m 3An extruded foam sheet was molded in the same manner as in Example 1, except that the above-mentioned step was changed to the above-mentioned step.

[0052] The resulting polyethylene resin composition had an MFR of 3.2 g / 10 min and a density of 931 kg / m 3 The melt tension was 61 mN.

[0053] The obtained extruded polyethylene foam sheet had a poor surface smoothness and non-uniform cells. The expansion ratio was 2.9 times, and the closed cell ratio was 63%. The melting point of the polyethylene resin composition was 123°C, and the heat of fusion at 120°C or higher was 21 J / g, indicating poor heat resistance. The results are shown in Table 1.

[0054] Comparative Example 2 Ethylene-α-olefin copolymer (A) is available under the trade name Nipolon-L M50 (MFR 3.0g / 10min, density 936kg / m 3 (B) high-pressure low-density polyethylene (Petrothene 220K, manufactured by Tosoh Corporation, MFR 3.0 g / 10 min, density 931 kg / m 3 The ethylene polymer (C) was Petrothene 208, manufactured by Tosoh Corporation, with a MFR of 24 g / 10 min and a density of 924 kg / m 3 The above were dry-blended in a ratio of 40:30:30 (wt %) and molded into an extruded foam sheet in the same manner as in Example 1.

[0055] The resulting polyethylene resin composition had an MFR of 4.1 g / 10 min and a density of 931 kg / m 3 The melt tension was 68 mN.

[0056] The resulting extruded polyethylene foam sheet had a heat of fusion of 18 J / g at 120° C. or higher, and was poor in heat resistance. The results are shown in Table 1.

[0057] [Table 1]

[0058] [Table 2] [Industrial Applicability]

[0059] The uses of the foam made of the polyethylene resin composition of the present invention are not particularly limited, and it can be suitably used as a heat-insulating molded article such as a shock-absorbing container, a building material, or a heating device.

Claims

1. The melt flow rate (hereinafter referred to as MFR) measured at 190°C and a load of 21.2 N is 0.5 g / 10 min or more and less than 10 g / 10 min, and the density is 930 kg / m ３ More than 945kg / m ３ The following ethylene / α-olefin copolymer (A) is 50 to 90% by weight, has an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min, and has a density of 925 kg / m ３ More than 935kg / m ３ A polyethylene resin composition comprising 5 to 30% by weight of a high-pressure low-density polyethylene (B) and 5 to 20% by weight of an ethylene polymer (C) having an MFR of 20 g / 10 min or more and less than 200 g / 10 min, wherein the density difference between the ethylene / α-olefin copolymer (A) and the high-pressure low-density polyethylene (B) is 15 kg / m ３ A polyethylene resin composition comprising:

2. The density of the ethylene polymer (C) is 900 kg / m ３ More than 945kg / m ３ The polyethylene resin composition according to claim 1, wherein:

3. The polyethylene resin composition according to claim 1, which has a heat of fusion at 120° C. or higher of 25 J / g or more.

4. A non-crosslinked extruded foam comprising the polyethylene resin composition according to any one of claims 1 to 3.

5. The non-crosslinked extruded foam according to claim 4, having a closed cell content of 70% or more.

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