Polyethylene-based resin foamed sheet

Abstract

To provide a foamed sheet that is less prone to formation of through-holes in the sheet even when widened and thinned and that enables stable production.SOLUTION: A polyethylene-based resin foamed sheet obtained by foaming a resin composition containing a copolymer (A) of ethylene and an α-olefin having 4 to 10 carbon atoms, the copolymer (A) satisfying requirements (A-1) to (A-3), (A-1) a melt flow rate (MFR2.16(A)) measured at 190°C under a 2.16 kg load in accordance with JIS K6921 being 2.0 g / 10 min or more and 12.0 g / 10 min or less, (A-2) a density (ρ(A)) measured in accordance with JIS K7112 being 913 kg / m3 or more and 928 kg / m3 or less, and (A-3) a ratio (MFR10(A) / MFR2.16(A)) of a melt flow rate (MFR10(A)) measured at 190°C under a 10 kg load in accordance with JIS K6921 to the melt flow rate (MFR2.16(A)) measured at 190°C under a 2.16 kg load in accordance with JIS K6921 being 6.0 or more and 18.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyethylene-based resin foam sheet, and more particularly to a resin foam sheet suitable as interleaving paper for glass plates. [Background technology]

[0002] Resin foam sheets are used in a variety of applications due to their excellent light weight and cushioning properties. Examples of base resins that constitute resin foam sheets include various resins such as polyethylene resin, polypropylene resin, polystyrene resin, and polyester resin.

[0003] For example, a resin foam sheet is used as an interleaf paper in the form of a flat sheet (see, for example, Patent Document 1). The interleaf paper is interposed between glass plates for liquid crystal displays and other such glass plates to prevent foreign matter from adhering to the glass plates and to prevent cracks and damage caused by contact between the glass plates during transportation and storage of the glass plates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-040773 Summary of the Invention [Problem to be solved by the invention]

[0005] However, interleaf paper is required to be thin and wide in order to transport and store glass plates and the like in greater quantities and more efficiently, but conventional resin foam sheets such as those disclosed in Patent Document 1 have a problem in that when the sheets are made wider and thinner, through holes are formed in the sheets. Therefore, it is difficult to stably produce wide and thin resin foam sheets using conventional techniques.

[0006] The present invention has been made in consideration of such problems, and aims to provide a resin foam sheet that is unlikely to develop through holes in the sheet even when made wider and thinner, and that can be produced stably. [Means for solving the problem]

[0007] Means for Solving the Problems The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that a polyethylene-based resin foamed sheet obtained by foaming a resin composition containing a copolymer of a specific ethylene and an α-olefin having 4 to 10 carbon atoms can be stably produced without the formation of through holes even when the sheet is made wider and thinner, and have thus completed the present invention.

[0008] The present invention includes the following embodiments. [1] A polyethylene-based resin foamed sheet obtained by foaming a resin composition containing a copolymer (A) of ethylene and an α-olefin having 4 to 10 carbon atoms, wherein the copolymer (A) satisfies the following requirements (A-1) to (A-3): (A-1) A melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921 2.16(A) (A-2) The density (ρ) measured in accordance with JIS K7112 is 2.0 g / 10 min or more and 12.0 g / 10 min or less. (A) ) is 913 kg / m 3 More than 928kg / m 3 (A-3) Melt flow rate (MFR) measured at 190°C under a load of 10 kg in accordance with JIS K6921 10(A) ) and the melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921. 2.16(A) ) and the ratio (MFR 10(A) / MFR 2.16(A) ) is between 6.0 and 18.0.

[0009] [2] The foamed sheet according to [1], wherein the copolymer (A) has long chain branches.

[0010] [3] The foamed sheet according to [1] or [2], wherein the copolymer (A) is a copolymer of ethylene and 1-hexene.

[0011] [4] The foamed sheet according to any one of [1] to [3], wherein the resin composition further contains a low-density polyethylene (B) that satisfies the following requirements (B-1) and (B-2): (B-1) The melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921 2.16(B) (B-2) The density (ρ) measured in accordance with JIS K7112 is 0.5 g / 10 min or more and 10.0 g / 10 min or less. (B) ) is 910 kg / m 3 More than 930kg / m 3 The following is the result.

[0012] [5] The foamed sheet according to [4], wherein the content of the copolymer (A) is 20.0 parts by mass or more and 95.0 parts by mass or less, per 100 parts by mass of the total of the copolymer (A) and the polyethylene (B), and the content of the polyethylene (B) is 5.0 parts by mass or more and 80.0 parts by mass or less, per 100 parts by mass of the total of the copolymer (A) and the polyethylene (B).

[0013] [6] The foamed sheet according to any one of [1] to [5], which is used as an interleaving paper for glass plates. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a polyethylene resin foam sheet that is unlikely to have through holes even when made wider and thinner and can be stably produced. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment.

[0016] [Polyethylene resin foam sheet] The polyethylene-based resin foamed sheet of the present embodiment (hereinafter also simply referred to as "foamed sheet") is a foamed sheet obtained by foaming a resin composition containing a copolymer (A) of ethylene and an α-olefin having 4 to 10 carbon atoms (hereinafter also simply referred to as "copolymer (A)"), and the copolymer (A) satisfies the following requirements (A-1) to (A-3): (A-1) Melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921 2.16(A) ) is 2.0g / 10min or more and 12.0g / 10min or less. (A-2) Density (ρ) measured in accordance with JIS K7112 (A) ) is 913 kg / m 3 More than 928kg / m 3 The following is the result. (A-3) Melt flow rate (MFR) measured at 190°C under a 10 kg load in accordance with JIS K6921 10(A) ) and the melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921. 2.16(A) ) and the ratio (MFR 10(A) / MFR 2.16(A) ) is between 6.0 and 18.0.

[0017] According to the present embodiment, a foamed sheet can be provided that is unlikely to have through holes even when the sheet is made wider and thinner, and that can be stably produced. Although the reason for this is not clear, the inventors speculate as follows.

[0018] That is, the base resin used in conventional thin resin foam sheets is high-pressure low-density polyethylene, which is suitable for thin foaming, but has a limit to the resin's elongation properties, and when the foam sheet is made wider and thinner, it tends to easily develop through holes. On the other hand, the foamed sheet of this embodiment is obtained by foaming a resin composition containing copolymer (A). Copolymer (A) is a linear low-density polyethylene with long-chain branching introduced therein, and is a resin in which the long-chain branching is controlled to improve elongation properties while maintaining resin properties suitable for thin foaming. Therefore, it is presumed that a foamed sheet obtained by foaming a resin composition containing such copolymer (A) is unlikely to develop through-holes in the sheet even when the sheet is made wider and thinner, and can be produced stably. However, the reason is not limited to this.

[0019] The shape of the foamed sheet is not particularly limited, and may be any shape that is formed in the production of ordinary foamed sheets, such as a square, approximately square, rectangle, approximately rectangle, trapezoid, or approximately trapezoid when viewed from the surface. The thickness (cross-sectional length) of the foamed sheet is, for example, 0.15 to 2.00 mm. The foamed sheet is mainly handled as a roll product. The length and width suitable for such a roll product are, for example, 10.0 to 1000.0 m in the winding direction (length) and 1.0 to 4.0 m in width. When the foamed sheet is cut into a rectangular shape from the roll product, the length is, for example, 1.0 to 3.5 m and the width is 1.0 to 4.0 m, and the rectangular shape is used according to the size of the glass. As described above, according to this embodiment, through holes are unlikely to occur in the foamed sheet, and a wide and thin foamed sheet can be stably produced.

[0020] Foamed sheets tend to have excellent moldability during thermoforming, comparable to that of ordinary cross-linked polyethylene sheets, and molded articles thermoformed from foamed sheets tend to be more rigid than articles made from cross-linked polyethylene sheets.

[0021] Next, the resin composition, the method for producing the same, and the method for producing the foamed sheet will be described in detail.

[0022] [Resin composition] <Copolymer (A)> The resin composition according to this embodiment contains a copolymer (A) of ethylene and an α-olefin having 4 to 10 carbon atoms. The copolymer (A) satisfies the following requirements (A-1) to (A-3). The copolymer (A) may be used singly or in combination of two or more.

[0023] The copolymer (A) is preferably a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and more preferably a copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms. Examples of the α-olefin in the copolymer (A) include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. The copolymer (A) may contain one type of these structural units alone, or two or more types.

[0024] Copolymer (A) is preferably a copolymer of ethylene and 1-hexene (hereinafter also simply referred to as "ethylene-1-hexene copolymer"), since this makes it less likely for through holes to form in the sheet even when the sheet is made wider and thinner, and allows for more stable production.

[0025] (Requirement (A-1)) Melt Flow Rate (MFR 2.16(A) The melt flow rate (MFR) is 2.0 g / 10 min or more and 12.0 g / 10 min or less, preferably 4.0 g / 10 min or more and 9.0 g / 10 min or less. 2.16(A) When the melt flow rate (MFR) is in the above range, the thickness is less likely to be uneven during production, and through holes are less likely to be formed, so that a foamed sheet with a wider width and a thinner thickness can be stably produced. 2.16(A) ), and the melt flow rate (MFR 2.16(B) ) are measured at 190°C under a load of 2.16 kg in accordance with JIS K6921. For specific measurement methods, see the examples.

[0026] (Requirement (A-2)) Density (ρ (A) ) is 913 kg / m 3 More than 928kg / m 3or less, preferably 914 kg / m 3 More than 926kg / m 3 The density (ρ (A) When the density (ρ) is within the above range, the foaming agent is less likely to escape excessively immediately after molding, and wrinkles are less likely to occur. Therefore, even if fine pores are present, they are less likely to expand, and a foamed sheet tends to be produced more stably. In this specification, the density (ρ (A) ) and density (ρ (B) ) are measured in accordance with JIS K7112. Specifically, the density (ρ (A) ) or density (ρ (B) ) is MFR 2.16(A) or MFR 2.16(B) The strand obtained when measuring the density is slowly cooled by air cooling, and the strand is used for measurement in a density gradient tube. For more specific measurement methods, see the Examples.

[0027] (Requirement (A-3)) Melt Flow Rate (MFR 10(A) ) and Melt Flow Rate (MFR 2.16(A) ) and the ratio (MFR 10(A) / MFR 2.16(A) ) is 6.0 or more and 18.0 or less, preferably 9.0 or more and 14.0 or less. 10(A) / MFR 2.16(A) When the ratio (MFR) is in the above range, the frequency of bubbles breaking tends to decrease even when a partially coarse foaming phenomenon occurs, and even when the sheet is made wider and thinner, through holes are less likely to occur in the sheet, and a foamed sheet tends to be produced stably. 10(A) / MFR 2.16(A) ) is an index of the amount of long chain branches present, and since it is 6.0 or more, it can be seen that the copolymer (A) has a considerable number of long chain branches. 10(A) ) is measured at 190°C under a load of 10 kg in accordance with JIS K6921. For specific measurement methods, see the examples.

[0028] The copolymer (A) may be a commercially available product, such as Evolue (registered trademark) E (trade name, manufactured by Prime Polymer Co., Ltd.) and Symphotec (registered trademark, manufactured by Japan Polyethylene Co., Ltd.).

[0029] The content of copolymer (A) is preferably 20.0 to 100.0 parts by mass, more preferably 22.0 to 84.0 parts by mass, and even more preferably 24.0 to 80.0 parts by mass, relative to 100 parts by mass of the resin composition. The higher the proportion of copolymer (A), the less likely through holes will be formed in the sheet.

[0030] <Low-density polyethylene (B)> The resin composition according to this embodiment preferably further contains a low-density polyethylene (B) (hereinafter also simply referred to as "polyethylene (B)"). The polyethylene (B) satisfies the following requirements (B-1) and (B-2), and preferably satisfies requirements (B-1) to (B-3). Examples of the polyethylene (B) include linear low-density polyethylene and high-pressure low-density polyethylene. The polyethylene (B) is preferably high-pressure low-density polyethylene. One type of polyethylene (B) may be used alone, or two or more types may be used in combination.

[0031] Polyethylene (B) has excellent shock-absorbing properties, and even a thin foamed sheet tends to maintain its shock-absorbing properties. Therefore, a foamed sheet obtained by foaming a resin composition containing such polyethylene (B) and copolymer (A) tends to be less likely to have through-holes and to be more stably wide and thin. Furthermore, such a foamed sheet tends to be more suitable as an interleaf paper.

[0032] (Requirement (B-1)) Melt Flow Rate (MFR 2.16(B) The melt flow rate (MFR) is 0.5 g / 10 min or more and 10.0 g / 10 min or less, preferably 3.0 g / 10 min or more and 6.0 g / 10 min or less. 2.16(B)) is within the above range, melt-kneading with the copolymer (A) is more suitably carried out, and the film thickness is less likely to be uneven during production, and through holes are less likely to be formed, which tends to enable more stable production of a wider and thinner foamed sheet.

[0033] (Requirement (B-2)) Density (ρ (B) ) is 910 kg / m 3 More than 930kg / m 3 or less, preferably 925 kg / m 3 More than 927kg / m 3 The density (ρ (B) ) in the above range, the foaming agent does not evaporate excessively immediately after molding, and wrinkles tend to be less likely to occur. Therefore, even if fine pores are present, they tend not to expand, and a wider and thinner foamed sheet tends to be produced more stably.

[0034] (Requirement (B-3)) The difference between the melting point of the polyethylene (B) and that of the copolymer (A) is preferably within 10° C., more preferably within 5° C. When the difference between the melting points of the copolymer (A) and the polyethylene (B) is within the above range, better bubbles tend to be formed, which tends to enable more stable production of wider and thinner foamed sheets.

[0035] The polyethylene (B) can be produced by a conventionally known method using a conventionally known catalyst, including a multi-site catalyst such as a Ziegler catalyst, or a single-site catalyst such as a metallocene catalyst. The polyethylene (B) may be a commercially available product, such as the Sumikathen (registered trademark) series (trade name, manufactured by Sumitomo Chemical Co., Ltd.), the Suntec (registered trademark) LD series (trade name, manufactured by Asahi Kasei Corporation), or the Novatec (registered trademark) LD series (trade name, manufactured by Japan Polyethylene Co., Ltd.).

[0036] When the resin composition contains polyethylene (B), the content of copolymer (A) is preferably 20.0 parts by mass or more and 95.0 parts by mass or less, more preferably 30.0 parts by mass or more and 80.0 parts by mass or less, based on 100 parts by mass of the total of copolymer (A) and polyethylene (B). The content of polyethylene (B) is preferably 5.0 parts by mass or more and 80.0 parts by mass or less, more preferably 20.0 parts by mass or more and 70.0 parts by mass or less, based on 100 parts by mass of the total of copolymer (A) and polyethylene (B). When the contents of copolymer (A) and polyethylene (B) are within the above ranges, copolymer (A) and polyethylene (B) are more suitably melt-kneaded, which tends to make it less likely for through holes to form, and to enable the more stable production of a foamed sheet with a wider width and a thinner thickness. The higher the proportion of polyethylene (B), the less likely through holes to form in the sheet.

[0037] The content of the polyethylene (B) is preferably 3.0 to 68.0 parts by mass, and more preferably 20.0 to 66.0 parts by mass, based on 100 parts by mass of the resin composition.

[0038] <Polyolefin polymer antistatic agent> The resin composition according to the present embodiment preferably further contains a polyolefin polymer-type antistatic agent (hereinafter also simply referred to as "antistatic agent"). One type of antistatic agent may be used alone, or two or more types may be used in combination.

[0039] When the resin composition contains an antistatic agent, it tends to exhibit antistatic properties immediately after production and to be able to more effectively suppress excessive charging due to friction during transport on the production line, which tends to more effectively prevent ignition caused by discharge phenomena and enable more stable production of wider and thinner foamed sheets.

[0040] Examples of antistatic agents include polyolefin-based polymer-type antistatic agents having a number-average molecular weight (Mn) of 50,000 or less. The lower limit of the number-average molecular weight (Mn) is usually 1,000 or more. Examples of polyolefin-based polymer-type antistatic agents include polyetherolefin-based polymer-type antistatic agents. In this specification, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersity (Mw / Mn) can be measured by gel permeation chromatography (GPC) and calculated using a calibration curve based on standard polystyrene.

[0041] For example, the antistatic agent is preferably a polyether olefin polymer-based antistatic agent having a melting point of 100° C. or higher, since this can more suitably prevent the antistatic agent from bleeding from the surface of the foamed sheet in a high-temperature environment such as summer. In this specification, the melting point can be measured, for example, by DSC (differential scanning calorimetry).

[0042] The antistatic agent may be a commercially available product, such as Pelestat (registered trademark) 300 (product name), Pelectoron (registered trademark) HS (product name), or Pelectoron (registered trademark) LMP (product name) manufactured by Sanyo Chemical Industries, Ltd.

[0043] The content of the antistatic agent is preferably 1.0 to 12.0 parts by mass, and more preferably 4.0 to 9.0 parts by mass, relative to 100 parts by mass of the resin composition.

[0044] <Hydrophilic agent> The resin composition according to this embodiment preferably further contains a hydrophilizing agent. The hydrophilizing agents may be used alone or in combination of two or more.

[0045] When the resin composition contains a hydrophilizing agent, for example, when the foamed sheet is used as interleaving paper for glass or the like, the washability when washed with water after transportation tends to be improved.

[0046] Examples of hydrophilizing agents include surfactants with an HLB value of not less than 18. Preferred hydrophilizing agents are surfactants with an HLB value of not less than 19, and more preferably polyethylene glycols with an HLB value of not less than 19. The number-average molecular weight (Mn) of polyethylene glycol is preferably 10,000 or less, and more preferably 5,000 or less, in order to obtain more suitable water solubility.

[0047] In this specification, the HLB (Hydrophile-Lipophile Balance) value is a value proposed by Davis et al. to evaluate the hydrophilicity of a compound, and is a numerical value determined by the Davis method defined in, for example, the literature "JT Davis and EK Rideal, "Interface Phenomena," 2nd ed., Academic Press, New York, 1963," and refers to a value calculated by the following formula (i): HLB value = 7 + Σ[1] - Σ[2] (i) (In formula (i), [1] represents the number of hydrophilic groups, and [2] represents the number of hydrophobic groups.)

[0048] The hydrophilizing agent may be a commercially available product, such as polyethylene glycol "PEG300" and "PEG400" manufactured by Sanyo Chemical Industries, Ltd.

[0049] The content of the hydrophilizing agent is preferably 0.01 to 5.0 parts by mass, and more preferably 0.1 to 1.0 part by mass, relative to 100 parts by mass of the resin composition.

[0050] <Other ingredients> The resin composition according to this embodiment may contain other components such as various polymeric compounds, such as thermosetting resins, thermoplastic resins, and their oligomers, and elastomers, which have not been mentioned above, and additives, as long as the properties of this embodiment are not impaired. Examples of such components include polyester polymeric antistatic agents, foaming agents, cell regulators, stabilizers, flame retardants, antioxidants, colorants, UV absorbers, and auxiliary agents. These other components may be used alone or in combination.

[0051] Examples of the foaming regulator include organic foaming regulators and inorganic foaming regulators. The foaming regulator is preferably an organic foaming regulator, more preferably polytetrafluoroethylene, because it can more suitably improve or suppress the foaming power.

[0052] The content of each of the other components is usually 0.001 to 10.0 parts by mass relative to 100 parts by mass of the resin composition.

[0053] [Method for producing resin composition] The resin composition according to the present embodiment may be prepared by, for example, blending the above-described components and, if necessary, a foaming agent in an extrusion molding machine, and extruding the mixture into a rod, tube, thread, plate, or other shape depending on the die shape. Examples of the extruder include a single-screw extruder, a twin-screw extruder, a vent extruder, and a tandem extruder. For details about the foaming agent, please refer to the description below and the examples.

[0054] [Method for producing foamed sheet] The foamed sheet of the present embodiment can be produced, for example, by charging the resin composition obtained by the above-mentioned production method or each of the above-mentioned components, and, if necessary, a foaming agent, into an extruder, heating and melt-kneading the mixture, and then extrusion-foaming the mixture into a sheet.

[0055] <Foaming agent> Examples of blowing agents include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, and isohexane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; chlorinated hydrocarbons such as methyl chloride and ethyl chloride; fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane; ethers such as dimethyl ether, diethyl ether, and ethyl ether; organic physical blowing agents such as dimethyl carbonate, methanol, and ethanol; inorganic blowing agents such as oxygen, nitrogen, carbon dioxide, air, and water; and decomposition-type blowing agents such as azodicarbonamide. These blowing agents may be used alone or in combination.

[0056] The blowing agent is preferably an organic physical blowing agent, more preferably a blowing agent containing normal butane, isobutane, or a mixture thereof as a main component, because of its excellent compatibility with the copolymer (A) and the polyethylene (B) blended as needed, and its excellent foaming properties.

[0057] The amount of foaming agent added can be adjusted appropriately depending on the type of foaming agent and the desired density of the foamed sheet, but is usually 4.0 to 35.0 parts by mass, preferably 5.0 to 30.0 parts by mass, and more preferably 6.0 to 25.0 parts by mass, per 100 parts by mass of the resin composition.

[0058] [Interleaving paper] The foamed sheet of the present embodiment is suitably used as an interleaving paper for glass plates. The interleaving paper is usually interposed between a plurality of glass plates. Examples of the glass plates include glass plates for liquid crystal displays, glass plates for plasma displays, and glass panels for various image display devices such as electroluminescence displays.

[0059] The foamed sheet is less likely to develop through-holes even when the sheet is wide and thin. By using such a foamed sheet as interleaf paper, it becomes possible to transport and store glass plates and the like more efficiently. Furthermore, by using interleaf paper, it becomes possible to more effectively prevent adhesion of foreign matter to glass plates and cracks and damage caused by contact between glass plates.

[0060] The shape and size of the interleaf paper may be determined by referring to the foamed sheet described above. In this embodiment, even if the interleaf paper has a planar area larger than that of the glass plate and a thickness equal to or smaller than that of the glass plate, through holes are unlikely to be formed, and therefore the interleaf paper can be used as the interleaf paper.

[0061] In this embodiment, interleaving paper for glass plates is exemplified as a suitable example of the foamed sheet, but the use of the foamed sheet is not limited to interleaving paper for glass plates, and the foamed sheet can also be used for components other than glass plates, such as packaging materials for electronic products, precision instruments, circuit boards, and electronic precision instruments such as silicon wafers. [Example]

[0062] The present invention will be described in more detail below with reference to examples, although the present invention is not particularly limited to the following examples.

[0063] [Method of measuring raw materials] (1) Melt flow rate (MFR 2.16(A) , M.F.R. 10(A) , and MFR 2.16(B) ) The melt flow rate (MFR) of the copolymer (A) used in the examples and comparative examples 2.16(A) , and MFR 10(A) ), and the melt flow rate (MFR 2.16(B) ) was measured as follows: Specifically, the melt flow rate (MFR 2.16(A)The melt flow rate (MFR) of polyethylene (B) was measured at 190°C under a load of 2.16 kg using a melt indexer QC-652B (trade name, manufactured by Cometech) in accordance with JIS K6921. 2.16(B) ) was measured at 190°C under a load of 2.16 kg in accordance with JIS K6921. Melt flow rate (MFR) of copolymer (A) 10(A) ) was measured using a melt indexer QC-652B (trade name, manufactured by Cometech) at 190°C under a load of 10 kg in accordance with JIS K6921.

[0064] (2) Ratio (MFR 10(A) / MFR 2.16(A) ) The melt flow rate (MFR) of the copolymer (A) obtained by the above-mentioned melt flow rate measurement method was 2.16(A) , and MFR 10(A) ) value, the ratio (MFR 10(A) / MFR 2.16(A) ) was calculated.

[0065] (3) Density (ρ (A) , and (ρ (B) ) The density (ρ (A) ), and the density of polyethylene (B) (ρ (B) ) was measured as follows: Specifically, the density (ρ (A) ) is the melt flow rate (MFR) of the copolymer (A) in accordance with JIS K7112. 2.16(A) The strand obtained when measuring the density was slowly cooled by air, and the strand was used for measurement in a density gradient tube. Similarly, the density of polyethylene (B) (ρ (B) ) was also measured in a density gradient tube using the strand after slow cooling in accordance with JIS K7112.

[0066] [Preparation of Resin Composition and Foam Sheet] Example 1 Copolymer (A) was ethylene-1-hexene copolymer (MFR 2.16(A) :6.1g / 10min, ρ (A) :920kg / m 3 , ratio (MFR 10(A) / MFR 2.16(A) A resin composition was obtained by feeding 100 parts by mass of a copolymer having long chain branches (Evolue (registered trademark) E (trade name) manufactured by Prime Polymer Co., Ltd.) (91.6 parts by mass per 100 parts by mass of the resin composition), 8.7 parts by mass of a polyetherolefin polymer-type antistatic agent (Pelestat (registered trademark) 300 (trade name) manufactured by Sanyo Chemical Industries, Ltd., Mn: 14000, melting point: 136°C) as a polyolefin polymer-type antistatic agent (8.0 parts by mass per 100 parts by mass of the resin composition), and 0.4 parts by mass of polyethylene glycol (PEG300 (trade name) manufactured by Sanyo Chemical Industries, Ltd.) as a hydrophilizing agent (0.4 part by mass per 100 parts by mass of the resin composition) into an extruder. Furthermore, butane, a volatile gas, was injected as a foaming agent into the middle of the cylinder, and the mixture was heated, melted, and kneaded, followed by extrusion foam molding into a sheet, to obtain a foamed sheet (1) which was a long roll product having a thickness of 0.30 mm and a width of 2.8 m.

[0067] Example 2 The copolymer (A) was 70 parts by mass (64.2 parts by mass per 100 parts by mass of the resin composition) of ethylene-1-hexene copolymer (Evolue (registered trademark) E (product name) manufactured by Prime Polymer Co., Ltd.), and the polyethylene (B) was high-pressure low-density polyethylene (MFR 2.16(B) :5.1g / 10min, ρ (B) :926kg / m 330 parts by mass of a polyolefin-based polymer antistatic agent (manufactured by Asahi Kasei Corporation under the trade name Suntec (registered trademark) LD (product name)) (27.5 parts by mass per 100 parts by mass of the resin composition), 8.7 parts by mass of a polyetherolefin-based polymer antistatic agent (manufactured by Sanyo Chemical Industries, Ltd. under the trade name Pelestat (registered trademark) 300 (product name)) (8.0 parts by mass per 100 parts by mass of the resin composition) as a polyolefin-based polymer antistatic agent, and 0.4 parts by mass of a polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd. under the trade name PEG300 (product name)) as a hydrophilizing agent (0.4 parts by mass per 100 parts by mass of the resin composition) were fed into an extruder to obtain a resin composition. Using the obtained resin composition, a foamed sheet (2) was obtained as a long roll product having a thickness of 0.30 mm and a width of 2.8 m, as in Example 1.

[0068] Example 3 The copolymer (A) was 30 parts by mass (27.5 parts by mass per 100 parts by mass of the resin composition) of ethylene-1-hexene copolymer (Evolue (registered trademark) E (product name) manufactured by Prime Polymer Co., Ltd.), and the polyethylene (B) was high-pressure low-density polyethylene (MFR 2.16(B) :5.1g / 10min, ρ (B) :926kg / m 3 A resin composition was obtained in the same manner as in Example 1, except that the amount of the acrylic resin used was changed to 70 parts by mass (64.2 parts by mass per 100 parts by mass of the resin composition) of Suntec (registered trademark) LD (product name) manufactured by Asahi Kasei Corporation. A foamed sheet (2) was obtained in the form of a long roll having a thickness of 0.30 mm and a width of 2.8 m using the obtained resin composition in the same manner as in Example 1.

[0069] Comparative Example 1 High-pressure low-density polyethylene (MFR 2.16(B) :5.1g / 10min, ρ (B) :926kg / m 3100 parts by mass of a polyolefin-based polymer antistatic agent (manufactured by Asahi Kasei Corporation under the trade name Suntec (registered trademark) LD (product name)) (91.6 parts by mass per 100 parts by mass of the resin composition), 8.7 parts by mass of a polyetherolefin-based polymer antistatic agent (manufactured by Sanyo Chemical Industries, Ltd. under the trade name Pelestat (registered trademark) 300 (product name)) (8.0 parts by mass per 100 parts by mass of the resin composition) as a polyolefin-based polymer antistatic agent, and 0.4 parts by mass of a polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd. under the trade name PEG300 (product name)) (0.4 parts by mass per 100 parts by mass of the resin composition) as a hydrophilizing agent were fed into an extruder to obtain a resin composition. Using the obtained resin composition, a foamed sheet (4) was obtained as a long roll product having a thickness of 0.30 mm and a width of 2.8 m, as in Example 1.

[0070] The foamed sheets (1) to (4) obtained in Examples 1 to 3 and Comparative Example 1 were evaluated according to the following evaluation methods. The results are shown in Table 1 together with the formulation of each resin composition.

[0071] [Evaluation method] (1) Through-hole evaluation From each of the long rolls of foamed sheets obtained in Examples and Comparative Examples, foamed sheets having a sheet length of 400 m were obtained. The through holes in each foamed sheet were counted and counted every 1 m. 2 Number of through holes per m 2 The number of through holes was calculated using a surface defect inspection system ("KE-XGXM" (trade name) manufactured by Frontier Systems Co., Ltd.) while the foamed sheet was flowed at a line speed of 20 m / min. The surface defect inspection system counted through holes with an area of ​​0.624 mm 2 More than 5mm 2 Through holes of less than 1000 mm in size were detected and their number was counted.

[0072] (2) Productivity The foamed sheets obtained in the examples and comparative examples were each produced as long rolls of 400 m each, and 80 rolls of 400 m each were produced to confirm the productivity of the foamed sheets. The productivity was evaluated by carrying out the above-mentioned through-hole evaluation for each of the 80 rolls.2 More than 5mm 2 50 or more through holes of less than 5mm in area are detected per roll. 2 If one or more of the above through holes were detected per roll, the roll was deemed to be lost (defective). Rolls with excessive wrinkles or foreign matter other than through holes were also deemed to be lost. The ratio of the number of lost rolls to the 80 rolls produced (number of lost rolls / 80) was calculated, and productivity was evaluated according to the following criteria. (standard) ○: The ratio was 0% or more and less than 5%. △: The ratio was 5% or more and less than 20%. ×: The ratio was 20% or more.

[0073] [Table 1]

[0074] As shown in Table 1, it was found that the foamed sheet of the present embodiment is less likely to have through holes even when it is made wider and thinner. It was also found that such a foamed sheet can be stably produced according to the present embodiment.

Claims

1. A polyethylene-based resin foamed sheet obtained by foaming a resin composition containing a copolymer (A) of ethylene and an α-olefin having 4 to 10 carbon atoms, The copolymer (A) satisfies the following requirements (A-1) to (A-3): (A-1) Melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921 ２．１６（Ａ） ) is 2.0 g / 10 min or more and 12.0 g / 10 min or less. (A-2) Density (ρ) measured in accordance with JIS K7112 （Ａ） ) is 913 kg / m ３ More than 928kg / m ３ The following is the result. (A-3) Melt flow rate (MFR) measured at 190°C under a load of 10 kg in accordance with JIS K6921 １０（Ａ） ) and the melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921. ２．１６（Ａ） ) and the ratio (MFR １０（Ａ） / MFR ２．１６（Ａ） ) is 6.0 or more and 18.0 or less.

2. The foamed sheet according to claim 1 , wherein the copolymer (A) has long chain branches.

3. 2. The foamed sheet according to claim 1, wherein the copolymer (A) is a copolymer of ethylene and 1-hexene.

4. The foamed sheet according to claim 1, wherein the resin composition further contains a low-density polyethylene (B) that satisfies the following requirements (B-1) and (B-2): (B-1) Melt flow rate (MFR) measured at 190°C under a load of 2.16 kg in accordance with JIS K6921 ２．１６（Ｂ） ) is 0.5 g / 10 min or more and 10.0 g / 10 min or less. (B-2) Density (ρ) measured in accordance with JIS K7112 （Ｂ） ) is 910 kg / m ３ More than 930kg / m ３ The following is the result.

5. the content of the copolymer (A) is 20.0 parts by mass or more and 95.0 parts by mass or less, relative to 100 parts by mass of the total of the copolymer (A) and the polyethylene (B), 5. The foamed sheet according to claim 4, wherein an amount of the polyethylene (B) is 5.0 parts by mass or more and 80.0 parts by mass or less, based on 100 parts by mass of the total of the copolymer (A) and the polyethylene (B).

6. The foamed sheet according to any one of claims 1 to 5, which is used as an interleaving paper for glass plates.

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