Resin foam sheet

Abstract

The present invention provides a resin foam sheet that is less likely to cause deposits on a target material. The present invention provides a resin foam sheet comprising at least one foam layer, wherein at least one surface of the resin foam sheet is composed of a resin composition containing a polyethylene resin, wherein the polyethylene resin contained in the resin composition has a density of 928 kg / m 3 Above 933kg / m 3 Hereinafter, the crystallinity of the polyethylene resin is 44% or more and 58% or less.

Description

Technical Field

[0001] (Cross-reference to related applications)

[0002] This application claims the benefit of Japanese Patent Application No. 2020-162454, the contents of which are incorporated herein by reference.

[0003] The present invention relates to a resin foam sheet. Background Art

[0004] Resin foam sheets have excellent lightness and cushioning properties due to their foam layer. Therefore, they are used in a variety of applications. Known examples of such resin foam sheets include those with a single-layer structure consisting solely of a foam layer and those with a non-foamed layer as a layer other than the foam layer.

[0005] As the raw material resin of the resin foam sheet, for example, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, etc. are known.

[0006] Resin foam sheets with a single-layer structure consisting of only a foamed layer are typically manufactured using an extrusion foaming method. These sheets are produced by melt-kneading a raw resin and a foaming agent in an extruder, extruding the resulting melt-kneaded product into a sheet through a circular or flat die, and then foaming it. Resin foam sheets with a multilayer structure consisting of a foamed layer and a non-foamed layer are produced by methods such as: temporarily preparing a resin foam sheet consisting of only the foamed layer and then laminating it with a resin film to form the non-foamed layer; or co-extruding the foamed and non-foamed layers.

[0007] Resin foam sheets can be used as raw material sheets for thermoforming containers and the like. Furthermore, they can be used as cushioning materials while remaining flat. For example, Patent Document 1 below describes a multilayered resin foam sheet comprising a non-foamed layer as a spacer to be interposed between adjacent glass sheets when stacking multiple glass sheets.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2019-64048 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] It is believed that forming at least the surface layer of a resin foam sheet from a relatively soft resin such as polyethylene resin is effective in achieving excellent cushioning properties. However, there are commercially available polyethylene resins that are mixed with additives such as antioxidants and lubricants. When the surface of a resin foam sheet is formed from such a polyethylene resin, the aforementioned additives will also be present on the surface of the resin foam sheet, and the aforementioned additives may adhere to the target material in contact with the surface. Although the amount of additives attached is minimal, the adhesion of the additives may become a problem when the target material is an item requiring high cleanability, such as an electronic device-related component.

[0013] To address this issue, one approach might be to use commercially available additive-free polyethylene resin as the raw material resin for the resin foam sheet. However, if both additive-free and non-additive-free forms are used at the same manufacturing site, additives may adhere to the storage yard and manufacturing lines, raising concerns about additives contaminating the additive-free polyethylene resin. On the other hand, establishing a dedicated production line for using additive-free polyethylene resin at the resin foam sheet manufacturing site to prevent this is less desirable from the perspective of production line operational efficiency.

[0014] Even if additives are included, if the resin foam sheet itself can be given a function to prevent the additives from migrating to the target material, the above-mentioned problem can be solved. However, a method for imparting such a function to the resin foam sheet has not yet been established. Therefore, the object of the present invention is to provide a resin foam sheet that is less likely to cause adhesion to the target material.

[0015] Solutions for solving problems

[0016] The present invention for solving the above-mentioned problems provides a resin foam sheet comprising at least one foam layer.

[0017] At least one surface of the resin foam sheet is composed of a resin composition containing a polyethylene resin,

[0018] The density of the polyethylene resin contained in the resin composition is 928 kg / m 3 Above 933kg / m 3 The polyethylene resin has a crystallinity of 44% to 58%.

[0019] The present invention for solving the above-mentioned problems provides a resin foam sheet comprising at least one foam layer.

[0020] It has a multilayer structure in which the foamed layer and other layers are stacked.

[0021] At least one surface of the resin foam sheet is composed of a resin composition containing a polyethylene resin,

[0022] The density of the polyethylene resin contained in the resin composition is 928 kg / m 3 Above 933kg / m 3 The polyethylene resin has a crystallinity of 44% to 58%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram showing one way to use the resin foam sheet.

[0024] Figure 2 This is a schematic cross-sectional view showing the structure of a resin foam sheet according to one embodiment.

[0025] Figure 3 This is a schematic cross-sectional view showing a resin foam sheet according to another embodiment.

[0026] Figure 4 This is a schematic cross-sectional view showing a resin foam sheet according to another embodiment.

[0027] Figure 5 This is a schematic diagram showing a method for evaluating the migration of additives from a resin foam sheet to a counterpart material. DETAILED DESCRIPTION

[0028] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0029] The resin foam sheet in this embodiment is not particularly limited in its use and can be used in various applications. Regarding the migration of additives, the migration of fatty acid compounds is likely to be a problem. Therefore, in this embodiment, a specific polyethylene resin is used in the resin foam sheet to thereby suppress the migration of fatty acid compounds, etc., to the target material.

[0030] Hereinafter, the resin foam sheet in this embodiment will be described in detail by taking the case where it is used as a backing paper for a glass plate as an example. Figure 1 As shown, the resin foam sheet 1 of this embodiment is used as a backing paper for glass plates. The resin foam sheet 1 of this embodiment is sandwiched between adjacent glass plates 2 when a plurality of glass plates 2 are stacked in the vertical direction to form a stacked body 100 and used as a backing paper. The backing paper in this embodiment is composed of a resin foam sheet 1 produced by an extrusion foaming method. The backing paper in this embodiment is as shown in FIG. Figure 2 As shown, the resin foam sheet 1 is composed of a single-layer structure, with the foam layer 10 exposed on both surfaces. As described above, in the resin foam sheet 1 of this embodiment, both surfaces of the foam layer 10 serve as contact surfaces with the counterpart material (glass plate 2).

[0031] Examples of the glass plate 2 in the present embodiment include a glass plate for a substrate or a glass plate for a protective glass in a display panel such as a liquid crystal display or an organic EL display.

[0032] Such glass sheets generally have high expectations for cleanability. Therefore, substances such as fatty acid compounds, which are often added as additives to many commercially available resins, can easily become a problem when they adhere to such glass sheets. Therefore, the resin foam sheet 1 of this embodiment, which can suppress the migration of fatty acid compounds, can be used as a backing paper for glass sheets, making this effect particularly effective.

[0033] The resin foam sheet 1 (foam layer 10) of this embodiment is composed of a resin composition containing a polyethylene resin. The resin composition in this embodiment comprises the polyethylene resin and additives. The resin composition in this embodiment need not contain the polyethylene resin and the additives separately, but may contain multiple polyethylene resins and multiple additives.

[0034] The resin composition may include, for example, a high-density polyethylene resin (PE-HD) as the polyethylene resin. The high-density polyethylene resin (PE-HD) is obtained by a catalyst method (medium-low pressure polymerization method) with substantially no branching in the molecular structure and a molecular weight of 942 kg / m 3 The resin composition may include, for example, a linear low-density polyethylene resin (PE-LLD) as the polyethylene resin, wherein the linear low-density polyethylene resin (PE-LLD) is made into 910 kg / m by introducing a comonomer. 3 Above 925kg / m 3 The resin composition may contain, for example, a medium-density polyethylene resin (PE-MD) as the polyethylene resin, wherein the medium-density polyethylene resin (PE-MD) is produced to have a density between that of the linear low-density polyethylene resin (PE-LLD) and the high-density polyethylene resin (PE-HD).

[0035] The resin composition may include a very low density polyethylene resin (PE-VLD) as the polyethylene resin. The polyethylene resin may be, for example, a low density polyethylene resin (PE-LD) produced by high pressure polymerization and having long chain branches in its molecular structure.

[0036] As described above, the polyethylene resin contained in the resin composition of this embodiment does not need to be just one of these polyethylene resins. The resin composition of this embodiment may contain multiple polyethylene resins among these. That is, the resin composition may contain a first polyethylene resin and a second polyethylene resin as the polyethylene resin.

[0037] For example, one of the first polyethylene resin and the second polyethylene resin may be a high-density polyethylene resin (PE-HD) and the other may be a low-density polyethylene resin (PE-LD), or both may be low-density polyethylene resins (PE-LD).

[0038] In order to avoid the generation of deposits on the resin foam sheet relative to the counterpart material, the density of the polyethylene resin is preferably within a predetermined range. The density (density at 23°C) of the polyethylene resin in the resin composition of this embodiment is preferably 928 kg / m 3 More than 930 kg / m 3 The density of the polyethylene resin in the resin composition is preferably 933 kg / m 3 Below, more preferably 932kg / m 3 the following.

[0039] In order to make the density of the polyethylene resin contained in the aforementioned resin composition within the above-mentioned range, it is sufficient to include one polyethylene resin with a density within the above-mentioned range in the aforementioned resin composition. Alternatively, a plurality of polyethylene resins with a density within the above-mentioned range may be prepared and included in the aforementioned resin composition. Furthermore, it is also possible to combine a plurality of polyethylene resins including a polyethylene resin with a density exceeding the above-mentioned range, and adjust the density of the polyethylene resin in the state contained in the aforementioned resin composition to be within the above-mentioned range. That is, in the case where the aforementioned resin composition contains a plurality of polyethylene resins, it is sufficient to adjust the ratio of the plurality of polyethylene resins so that the density in the state of mixing the plurality of polyethylene resins becomes within the above-mentioned numerical range. Therefore, the polyethylene resin with the preferred density may be, for example, 928 kg / m 3 Above 932kg / m 3 The following low-density polyethylene resin (PE-LD) can also be made of a density lower than 928kg / m 3 The first polyethylene resin with a density exceeding 933kg / m 3 The second polyethylene resin is composed of

[0040] The density of the polyethylene resin can be determined by, for example, preparing a mixture in which the resin composition contains a plurality of polyethylene resins in such a proportion by mass that the plurality of polyethylene resins are blended, melt-kneading the mixture, and preparing a sample from the resulting melt-kneaded product. The density of the polyethylene resin can be determined by measuring the density of the sample. If the resin composition contains only one type of polyethylene resin, the density can be measured using a sample prepared from the polyethylene resin.

[0041] The density of the polyethylene resin can be measured, for example, by the method described in JIS K 7112, and can be obtained by the D method (density gradient tube).

[0042] In order to minimize the risk of deposits on the foamed resin sheet, the polyethylene resin preferably has a crystallinity within a specified range. The polyethylene resin preferably has a crystallinity of 44% or greater, more preferably 45% or greater. It is further preferred that the polyethylene resin have a crystallinity exceeding 45%. It is further preferred that the polyethylene resin have a crystallinity of 58% or less, more preferably 51% or less. It is further preferred that the polyethylene resin have a crystallinity of 47% or less.

[0043] To achieve a crystallinity within the aforementioned range for the polyethylene resin contained in the resin composition, it is sufficient to include a single polyethylene resin having a crystallinity within the aforementioned range in the resin composition. Alternatively, the resin composition may include multiple polyethylene resins having crystallinity within the aforementioned range. Furthermore, it is possible to combine multiple polyethylene resins, including one having a crystallinity exceeding the aforementioned range, to adjust the crystallinity of the polyethylene resin contained in the resin composition to within the aforementioned range. In other words, when the resin composition includes multiple polyethylene resins, it is sufficient to adjust the proportions of the multiple polyethylene resins so that the crystallinity of the mixed polyethylene resins falls within the aforementioned numerical range.

[0044] The crystallinity of the polyethylene resin can be determined by, for example, measuring the crystallinity of a sample prepared from a melt-kneaded product obtained by melt-kneading a mixture prepared by blending the plurality of polyethylene resins in such a proportion by mass that the resin composition contains the plurality of polyethylene resins. If the resin composition contains only one type of polyethylene resin, the crystallinity can be measured using a sample prepared from the polyethylene resin.

[0045] The crystallinity of the polyethylene resin can be measured according to the method described in JIS K7122: 1987 and JIS K7122: 2012 “Methods for determining heat of transition of plastics”.

[0046] That is, the crystallinity of the polyethylene resin can be measured by differential scanning calorimetry (DSC).

[0047] The sampling method and temperature conditions can be set as follows.

[0048] 5.5±0.5 mg of the sample was filled to the bottom of an aluminum measuring container so as to leave no gaps, and then the container was capped with an aluminum lid.

[0049] Then, differential scanning calorimetry analysis was performed using a "DSC7000X, AS-3" differential scanning calorimeter manufactured by Hitachi High-Tech Corporation.

[0050] The sample was heated and cooled according to the following procedure at a nitrogen flow rate of 20 mL / min to obtain a DSC curve.

[0051] (Step 1) Cool from 30°C to -40°C and hold for 10 minutes.

[0052] (Step 2) The temperature was raised from -40°C to 220°C (first temperature increase), and maintained for 10 minutes.

[0053] (Step 3) Cool down (cool) from 220°C to -40°C and maintain for 10 minutes.

[0054] (Step 4) The temperature was raised from -40°C to 220°C (second temperature increase).

[0055] In addition, all heating and cooling were performed at a rate of 10°C / min.

[0056] Alumina was used as the reference substance.

[0057] The heat of crystallization (J / g) was determined from the area of ​​the crystallization peak observed during the cooling process (step 3).

[0058] The ratio obtained by dividing the heat of crystallization by the theoretical heat of fusion of completely crystallized polyethylene, 285.7 J / g, was defined as the degree of crystallinity.

[0059] The heat of crystallization is calculated using analysis software included with the device from a straight line connecting a point where the DSC curve deviates from the high-temperature baseline and a point where the DSC curve returns to the low-temperature baseline, and the area of ​​the portion enclosed by the DSC curve.

[0060] The crystallinity can be calculated according to the following formula.

[0061] Crystallinity (%) = (heat of crystallization (J / g) / 285.7 (J / g)) × 100 (%)

[0062] In terms of the resin foam sheet having less concern about the generation of deposits on the counterpart material, it is particularly preferred that the density of the polyethylene resin be 930 kg / m 3 Above 932kg / m 3 In the case where the resin composition contains a plurality of polyethylene resins, the density of the mixed polyethylene resins is 930 kg / m 3 Above 932kg / m 3The crystallinity of the mixed polyethylene resins may be 45% or more and 51% or less. The resin composition can be easily adjusted to the above-mentioned preferred state by containing a plurality of polyethylene resins including the first polyethylene resin and the second polyethylene resin.

[0063] At least one of the first polyethylene resin and the second polyethylene resin is preferably a low-density polyethylene resin (PE-LD) polymerized by a high-pressure polymerization method. Since the low-density polyethylene resin (PE-LD) has long-chain branches, the resin composition is advantageous for capturing fatty acid compounds. The low-density polyethylene resin (PE-LD) is believed to facilitate the formation of a morphology comprising both amorphous regions with free volume and crystalline regions within the resin composition.

[0064] Long chain branching of polyethylene can be achieved, for example, by 13 C-NMR confirmation. For example, if 13 The presence of alkyl groups longer than hexyl by C-NMR can be used to determine the presence of long-chain branches in the polyethylene. Low-density polyethylene resin (PE-LD) preferably has alkyl groups longer than heptyl, and more preferably has alkyl groups longer than octyl.

[0065] In the case of multiple polyethylenes including the first polyethylene resin and the second polyethylene resin in the resin composition, it is preferred that both are low-density polyethylene resins (PE-LD). In the resin composition comprising two or more low-density polyethylene resins (PE-LD), the peak of crystallization in the DSC curve of the resin composition becomes broadened. That is, by including two or more low-density polyethylene resins (PE-LD), the overall crystallization behavior of the polyethylene resin during the cooling of the molten resin composition can be slowed down. Therefore, it is believed that a resin foam sheet comprising two or more low-density polyethylene resins (PE-LD) is advantageous in that it can suppress the change in the formed morphology depending on the cooling conditions.

[0066] The polyethylene resin described above preferably has a molecular structure that is bulky to a certain extent, for example, preferably has a moderately low melt mass flow rate. The melt mass flow rate (MFR) of the polyethylene resin is preferably 6 g / 10 minutes or less. The melt mass flow rate (MFR) of the polyethylene resin is more preferably 5 g / 10 minutes or less, and further preferably 4 g / 10 minutes or less. In order to reduce the equipment load when the resin foam sheet 1 is manufactured by the extrusion foaming method, the melt mass flow rate (MFR) of the polyethylene resin is preferably 0.1 g / 10 minutes or more. The melt mass flow rate (MFR) of the polyethylene resin is more preferably 0.2 g / 10 minutes or more, and further preferably 0.3 g / 10 minutes or more.

[0067] The melt mass melt flow rate (MFR) can be measured according to JIS K7210:1999, "Plastics—Test Methods for Melt Mass Melt Flow Rate (MFR) and Melt Volume Melt Flow Rate (MVR) of Thermoplastics." The melt mass melt flow rate (MFR) can be measured according to Method B of the same standard, "b) Measuring the Time for the Piston to Move a Predetermined Distance." Specifically, the melt mass melt flow rate (MFR) can be measured using, for example, the "Semi Auto Melt Indexer 2A" manufactured by Toyo Seiki Co., Ltd.

[0068] The measurement conditions were set as follows.

[0069] Sample: 3-8g

[0070] Warm-up: 270 seconds

[0071] Load holding: 30 seconds

[0072] Test temperature: 190℃

[0073] Test load: 21.18N

[0074] Piston travel distance (clearance): 25mm

[0075] The number of test times for the sample is set to 3, and the average of the results can be used as the value of the melt mass melt flow rate (g / 10 minutes).

[0076] The content of the polyethylene resin in the resin composition is preferably 80% by mass or greater, more preferably 83% by mass or greater, further preferably 85% by mass or greater, particularly preferably 88% by mass or greater, and even more preferably 90% by mass or greater. It should be noted that when the resin composition contains multiple polyethylene resins, the content of the polyethylene resin refers to the total amount.

[0077] Examples of the additives contained in the resin composition together with the polyethylene resin include polymeric antistatic agents, low-molecular antistatic agents (surfactants), lubricants, weathering stabilizers, light stabilizers, antioxidants, antibacterial agents, deodorants, pigments, inorganic fillers, and the like.

[0078] The total content of the additives in the resin composition in this embodiment is, for example, 1% by mass or more and 20% by mass or less. The total content of the additives in the resin composition is preferably 17% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0079] The resin foam sheet 1 of the present embodiment composed of the aforementioned resin composition is used as a backing paper for the glass plate 2 as described above. After the backing paper is in contact with the glass plate 2, it is peeled off from the surface of the glass plate 2, and therefore, it is preferably given antistatic properties. Therefore, the aforementioned resin composition constituting the contact surface of the resin foam sheet 1 preferably contains a polymer antistatic agent and a surfactant as the aforementioned additives. The aforementioned resin composition of the present embodiment may also contain a fatty acid compound. The fatty acid compound may be included in the aforementioned resin composition as the aforementioned additive or as an unavoidable impurity (mixed with foreign matter).

[0080] Examples of the polymeric antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester amide, polyether ester amide, ionomers such as ethylene-methacrylic acid copolymers, quaternary ammonium salts such as polyethylene glycol methacrylate copolymers, and copolymers of olefinic blocks and hydrophilic blocks.

[0081] The polymeric antistatic agent is preferably a copolymer of an olefin block and a hydrophilic block. The olefin block may be composed of, for example, a polyolefin having one or more olefins with 2 to 8 carbon atoms as structural units. The hydrophilic block may be composed of, for example, a polyoxyalkylene having, as structural units, an alkylene oxide with 2 to 8 carbon atoms, such as ethylene oxide, propylene oxide, or butylene oxide.

[0082] In this embodiment, the total content of the polymeric antistatic agent in the resin composition is, for example, 0.5% by mass or more and 10% by mass or less. The total content of the polymeric antistatic agent is preferably 1% by mass or more, more preferably 2% by mass or more. The total content of the polymeric antistatic agent is preferably 8% by mass or less, more preferably 6% by mass or less.

[0083] Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0084] Examples of the nonionic surfactants include ester surfactants in which polyols such as glycerol and sugars are ester-bonded with fatty acids; ether surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers; ester-ether surfactants in which alkylene oxides are added to fatty acids or polyol fatty acid esters; and amide surfactants such as fatty acid alkanolamides in which a hydrophobic group and a hydrophilic group are bonded via an amide bond.

[0085] Examples of the anionic surfactant include sulfonate-type surfactants such as alkylsulfonates, dialkylsulfosuccinates, α-olefinsulfonates, linear alkylbenzenesulfonates, naphthalenesulfonate-formaldehyde condensates, alkylnaphthalenesulfonates, and N-methyl-N-acyltaurates; carboxylate-type surfactants such as aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosinates, and N-acylglutamates; sulfate-type surfactants such as alkyl sulfates, polyoxyethylene alkyl ether sulfates, and oil sulfates; and phosphate-type surfactants such as alkylphosphates, polyoxyethylene alkylether phosphates, and polyoxyethylene alkylphenyl ether phosphates. Examples of the metal constituting the salt include alkali metals such as sodium, potassium, and lithium, and alkaline earth metals such as calcium and magnesium.

[0086] Examples of the cationic surfactant include quaternary ammonium salt-type surfactants such as alkylammonium salts and alkylbenzylammonium salts; and amine salt-type surfactants such as N-methylbishydroxyethylamine fatty acid ester hydrochloride.

[0087] Examples of the amphoteric surfactant include betaine-type surfactants such as alkyl betaines; amino acid-type surfactants such as alkylamino fatty acid salts; and amine oxide-type surfactants such as alkylamine oxides.

[0088] In this embodiment, the total content of the surfactant in the resin composition is, for example, 0.5% by mass or more and 10% by mass or less. The total content of the surfactant is preferably 1% by mass or more, more preferably 2% by mass or more. The total content of the surfactant is preferably 8% by mass or less, more preferably 6% by mass or less.

[0089] The resin composition of this embodiment preferably includes an anionic surfactant or a nonionic surfactant in the aforementioned surfactant. The resin composition of this embodiment particularly preferably includes an anionic surfactant. Specifically, 50% by mass or more of the surfactant contained in the resin composition is preferably an anionic surfactant, more preferably 75% by mass or more of the anionic surfactant, and even more preferably 90% by mass or more of the anionic surfactant. The surfactant contained in the resin composition may be substantially only anionic surfactants.

[0090] The fatty acid compound in this embodiment can be contained in the resin composition as a lubricant or the antistatic agent. Examples of the fatty acid compound include fatty acids, fatty acid metal salts, fatty acid amides, and fatty acid esters.

[0091] Specific examples of fatty acids include saturated fatty acids such as lauric acid, palmitic acid, stearic acid, and behenic acid, and unsaturated fatty acids such as oleic acid, erucic acid, linoleic acid, and linolenic acid. In addition to these monocarboxylic acids, dicarboxylic acids such as dimer acid can also be mentioned. Metals constituting fatty acid metal salts include calcium, magnesium, aluminum, and zinc.

[0092] Fatty acid amide refers to an acid amide derived from a fatty acid. Examples of the fatty acid amide include those derived from aliphatic amines.

[0093] Specific examples of fatty acid amides include stearic acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, and ethylene bishydroxystearic acid amide.

[0094] Specific examples of fatty acid esters include butyl stearate, stearic acid monoglyceride, oleic acid monoglyceride, behenic acid monoglyceride, linoleic acid monoglyceride, ricinoleic acid monoglyceride, hydroxystearic acid triglyceride, sorbitan fatty acid ester, polyoxyethylene (5) glyceryl monostearate, polyoxyethylene (20) glyceryl monostearate, polyoxyethylene (5) monooleate, pentaerythritol tetrastearate, polypentaerythritol adipate stearate, stearyl stearate, 1,2-hydroxystearic acid, hydrogenated castor oil, and the like.

[0095] The total content of fatty acid compounds in the resin composition constituting the resin foam sheet of this embodiment is preferably 10,000 ppm or less, more preferably 1,000 ppm or less, further preferably 100 ppm or less, and particularly preferably 10 ppm or less. The total content of fatty acid compounds may be 7 ppm or less, or 5 ppm or less. The total content of fatty acid compounds in the resin composition constituting the resin foam sheet of this embodiment may be 1 ppm or more, or 3 ppm or more. It should be noted that, in general, the total content of fatty acid compounds may be 5 ppm or more, 10 ppm or more, or 100 ppm or more.

[0096] The content of the fatty acid compound in the resin foam sheet can be measured by a known method. Examples of the method include the following method.

[0097] The aforementioned fatty acid metal salts can be measured, for example, as follows. The resin foam sheet is immersed in boiling methanol for extraction, cooled naturally, and the precipitate is filtered out. The precipitate is suspended in dilute hydrochloric acid and extracted with ether. Free fatty acids are extracted in the ether phase, and metals are extracted in the aqueous phase. Therefore, fatty acids can be identified and quantified using the methods described below, and metals can be identified and quantified using an ICP (inductively coupled plasma) emission spectrometer.

[0098] The fatty acids, fatty acid amides, and fatty acid esters can be quantitatively determined using a liquid chromatography-tandem mass spectrometer (LC-MS / MS) (for example, "ACCELA" manufactured by Termo SCIENTIFIC).

[0099] It should be noted that the standard curve used in the quantification of fatty acid compounds is prepared using five standard solutions of different concentrations (5ppm, 2ppm, 1ppm, 0.5ppm, 0.2ppm) prepared by diluting a 1000ppm concentration reference solution (methanol solution) of the quantified fatty acid compound (fatty acid, fatty acid amide, fatty acid ester) with methanol.

[0100] In addition, a sample for measurement in LC-MS / MS was prepared as follows.

[0101] The resin foam sheet was cut into approximately 2 mm square pieces, and approximately 0.15 g of an extraction sample was collected.

[0102] The extracted sample was precisely weighed, placed together with 10 ml of methanol in a PTFE (polytetrafluoroethylene) pressure-resistant container, and the pressure-resistant container was sealed.

[0103] The sealed pressure-resistant container was heated in an oven at 120°C for 2 hours, then taken out of the oven and allowed to cool naturally in a room at room temperature.

[0104] Open the pressure-resistant container that has cooled to room temperature and filter the extract in the container using filter paper (No. 5A).

[0105] The filtrate obtained by the above filtration was used as a measurement sample in LC-MS / MS.

[0106] From the measurement results, the amount of the fatty acid compound in the filtrate was calculated using the calibration curve obtained above.

[0107] The content (ppm) of the fatty acid compound in the resin foam sheet was determined from the amount of the fatty acid compound contained in the filtrate.

[0108] The resin composition is melt-kneaded together with a foaming agent and the like in an extruder, and the melt-kneaded product obtained by the melt-kneading is extruded in a sheet form from a die attached to the front end side of the extrusion direction of the extruder and foamed, thereby producing the resin foam sheet 1 of this embodiment. The width and thickness of the resin foam sheet 1 are not particularly limited, but the thickness is preferably 0.2 mm or more. The thickness of the resin foam sheet 1 is more preferably 0.5 mm or more. The thickness of the resin foam sheet 1 is preferably 2.0 mm or less, and more preferably 1.5 mm or less.

[0109] The resin foam sheet produced by the extrusion foaming method is usually hot and relatively soft just after being extruded. Usually, in order to prevent the resin foam sheet produced by the extrusion foaming method from producing unwanted deformation, it is rapidly cooled just after being extruded from the extruder. If the resin foam sheet 1 of the present embodiment is produced by this method, the polyethylene resin will be fixed in an insufficiently crystallized state. This is preferred because the concern about the resin foam sheet 1 producing attachments on the object material can be reduced, and the polyethylene resin contained therein can be fully crystallized. As to the proportion of polyethylene resin crystals contained in the resin foam sheet 1, the resin foam sheet 1 can be used as a sample and subjected to the DSC measurement as described above to determine it. It should be noted that the mass ratio of the polyethylene resin crystals contained in the resin foam sheet 1 is hereinafter referred to as "apparent crystallinity".

[0110] The apparent crystallinity of the resin foam sheet 1 can be specifically determined as follows.

[0111] That is, the apparent crystallinity can be measured using a sample collected from the resin foam sheet. The site from which the sample is collected from the resin foam sheet can be a randomly selected site.

[0112] The sampling method and temperature conditions are as follows.

[0113] 5.5±0.5 mg of the sample was filled to the bottom of an aluminum measuring container so as to leave no gaps, and then the container was capped with an aluminum lid.

[0114] Then, differential scanning calorimetry analysis was performed using a differential scanning calorimeter "DSC7000X, AS-3" manufactured by Hitachi High-Tech Corporation.

[0115] The sample was heated and cooled according to the following procedure at a nitrogen flow rate of 20 mL / min to obtain a DSC curve.

[0116] (Step 1) Cool from 30°C to -40°C and hold for 10 minutes.

[0117] (Step 2) Raise the temperature from -40°C (first temperature increase) to 220°C and maintain for 10 minutes.

[0118] In addition, heating and cooling were performed at a rate of 10°C / min.

[0119] Alumina was used as the reference substance.

[0120] The heat of fusion (J / g) was determined from the area of ​​the melting peak observed during the cooling process (step 2).

[0121] The value obtained by dividing the heat of fusion by the theoretical heat of fusion of completely crystalline polyethylene, 285.7 J / g, was defined as the apparent crystallinity.

[0122] The heat of fusion is calculated using analysis software included with the device from a straight line connecting a point where the DSC curve deviates from the low-temperature baseline and a point where the DSC curve returns to the high-temperature baseline, and the area of ​​the portion enclosed by the DSC curve.

[0123] The apparent crystallinity can be calculated according to the following formula.

[0124] Apparent crystallinity (%) = (heat of fusion (J / g) / 285.7 (J / g)) × 100 (%)

[0125] The apparent crystallinity of the resin foam sheet 1 in this embodiment preferably has the same value as the crystallinity of the polyethylene resin contained in the resin foam sheet 1. The apparent crystallinity of the resin foam sheet 1 is preferably 44% or greater, more preferably 45% or greater. The apparent crystallinity of the resin foam sheet 1 is more preferably greater than 45%. The apparent crystallinity of the resin foam sheet 1 is preferably 58% or less, more preferably 51% or less. The apparent crystallinity of the resin foam sheet 1 is more preferably 47% or less.

[0126] The apparent crystallinity (C1 (%)) of the resin foam sheet 1 is generally lower than the crystallinity (C2 (%)) of the polyethylene resin. Specifically, the ratio (C1 / C2) of the apparent crystallinity (C1) of the resin foam sheet 1 to the crystallinity (C2) of the polyethylene resin is generally 1.0 or less. This ratio (C1 / C2) is preferably 0.8 or greater. It can be 0.9 or greater.

[0127] To achieve an apparent crystallinity close to that of polyethylene resin, the resin foam sheet 1 extruded from the extruder can be made to avoid a sudden drop in temperature. Methods for preventing a sudden drop in temperature of the resin foam sheet 1 include slowing the speed of the extruded resin foam sheet 1 or blowing hot air onto the moving resin foam sheet 1. Furthermore, to achieve an apparent crystallinity close to that of polyethylene resin, the resin composition forming the resin foam sheet 1 may contain a crystallization nucleating agent or a crystallization accelerator.

[0128] The thickness of the resin foam sheet 1 can be determined by measuring the thickness at a plurality of randomly selected locations (eg, 20 locations) using a thickness gauge (eg, "Dial Thickness Gauge SM-112" manufactured by Teclock) and calculating the arithmetic mean.

[0129] The apparent density of the foam layer 10 in this embodiment is preferably 10 kg / m 3 More preferably, the apparent density is 15 kg / m 3 The apparent density of the foam layer 10 is preferably 200 kg / m 3The apparent density is more preferably 150 kg / m 3 Below, more preferably 100 kg / m 3 the following.

[0130] The apparent density of the foam layer 10 can be determined as follows.

[0131] [Determination of apparent density]

[0132] The apparent density of the foam layer 10 can be measured by the method described in JIS K7222:2005 "Cellular plastics and rubber - Determination of apparent density". Specifically, a foam layer 10 having an apparent volume of 100 cm 3 The above test pieces are cut and their mass is measured. It should be noted that when cutting the test pieces from the resin foam sheet, the original cell structure should not be changed as much as possible. In addition, it is not possible to prepare 100cm 3 When preparing the above test pieces, prepare as large a volume as possible. Then, calculate the apparent density using the following formula.

[0133] Apparent density (kg / m 3 ) = mass of test piece (g) / volume of test piece (mm 3 )×10 6

[0134] It should be noted that, in principle, the test piece is collected after more than 72 hours have passed since the resin foam sheet was produced, and after being placed in an atmosphere of temperature 23±2°C and relative humidity 50±10% for more than 16 hours for state conditioning, the mass and volume are measured under the same conditions.

[0135] The resin foam sheet 1 of this embodiment is as follows Figure 2 As shown, it is an extruded foam sheet having a single-layer structure with only a foam layer 10. Therefore, the surface of the foam layer 10 will abut the object material abutted by the resin foam sheet 1. In order to ensure that the retention amount of the fatty acid compound in the surface layer of the resin foam sheet 1 is above the specified level, it is preferred that the surface layer of the foam layer 10 has a larger amount of resin than the central portion in the thickness direction. Specifically, for the resin foam sheet 1, when the foam layer 10 is divided into three parts along the thickness direction, and divided into a sheet in the central portion in the thickness direction and two sheets including the surface layer, the apparent density of the sheet including the surface layer is preferably 1.1 times or more, more preferably 1.2 times or more, of the apparent density of the sheet including the surface layer. The apparent density of the sheet including the surface layer can be 1.3 times or more, or 1.5 times or more, of the apparent density of the sheet including the surface layer. In addition, the apparent density of the sheet including the surface layer is preferably 3 times or less of the apparent density of the sheet including the surface layer.

[0136] In the above, a single-layer structure having only the foam layer 10 is exemplified as the resin foam sheet 1, but the resin foam sheet 1 of this embodiment may also be a multi-layer structure. Figure 3 As shown, it can also be an extruded foam sheet having a non-foamed layer 20 on one side of the foam layer 10. The resin foam sheet 1 of the multi-layer structure is as shown in FIG. Figure 4 As shown, an extruded foam sheet may also have non-foamed layers 20 on both sides of the foam layer 10. The resin foam sheet 1 of this embodiment is not necessarily an extruded foam sheet.

[0137] The non-foamed layer 20 in the multi-layered resin foam sheet 1 can generally have a thickness of 5 μm or more and 500 μm or less.

[0138] When the resin foam sheet 1 includes a non-foamed layer 20, the surface of the non-foamed layer 20 becomes the contact surface with the object material. Figure 2 It should be noted that when the surface of the resin foam sheet 1 of this embodiment that contacts the object material is composed of the above-mentioned resin composition, it is effective in suppressing the migration of fatty acid compounds. Therefore, Figure 4 In the resin foam sheet 1 having the non-foamed layer 20 on both sides of the foamed layer 10, the material forming the foamed layer 10 is not particularly limited. Figure 3 The resin foam sheet 1 shown has a non-foamed layer 20 provided only on one side of the foamed layer 10. The other side of the foamed layer 10 becomes the contact surface with the target material. Therefore, it is preferred that the foamed layer 10 and the non-foamed layer 20 are formed separately from the resin composition as described above.

[0139] It should be noted that Figure 4 In the resin foam sheet 1 shown, the resin composition constituting the non-foamed layer 20 on one side and the resin composition constituting the non-foamed layer 20 on the other side may be the same resin composition or different resin compositions. Figure 3 In the resin foam sheet 1 shown, the resin composition constituting the foam layer 10 and the resin composition constituting the non-foam layer 20 may be the same resin composition or different resin compositions.

[0140] The resin foam sheet 1 of this embodiment has at least one foam layer, and has a single-layer structure of only the foam layer, or a multi-layer structure in which the foam layer and other layers are laminated. At least one surface is composed of a resin composition containing a polyethylene resin, and the polyethylene resin contained in the resin composition has a density of 928 kg / m 3 Above 933kg / m 3The resin foam sheet 1 has a density of 44% or less and a crystallinity of 58% or less. Therefore, even if a fatty acid compound is unintentionally contained in the resin composition, migration of the fatty acid compound to a target material in contact with the resin foam sheet 1 can be suppressed.

[0141] The resin foam sheet 1 of this embodiment has the above-mentioned functions and is therefore preferably used as a backing paper. However, the use of the resin foam sheet 1 is not limited to backing paper and can be used for various purposes. That is, the resin foam sheet of the present invention is not limited to the above-mentioned examples.

[0142] Example

[0143] Next, the present invention will be described in further detail with reference to Examples, but the present invention is not limited to these.

[0144] First, as polyethylene resins, four types represented by the following abbreviations "PE1" to "PE4" were prepared.

[0145] PE1: Low-density polyethylene resin produced by high-pressure polymerization, density: 931kg / m 3 、MFR=1.1g / 10min

[0146] PE2: Low-density polyethylene resin produced by high-pressure polymerization, density: 934kg / m 3 、MFR=3.0g / 10min

[0147] PE3: Low-density polyethylene resin produced by high-pressure polymerization, density: 921kg / m 3 、MFR=0.4g / 10min

[0148] PE4: Low-density polyethylene resin produced by high-pressure polymerization, density: 926kg / m 3 、MFR=3.5g / 10min

[0149] Furthermore, as the polymeric antistatic agent, one indicated by the following abbreviation "AS1" was prepared.

[0150] AS1: A polymer antistatic agent comprising a polyolefin block composed of polyolefin and a hydrophilic block composed of polyoxyalkylene.

[0151] Furthermore, as a surfactant, one type represented by the following abbreviation "SA1" was prepared.

[0152] SA1: Sodium alkyl sulfonate

[0153] Furthermore, as a fatty acid compound, one type represented by the following abbreviation "FA1" was prepared.

[0154] FA1: stearic acid amide

[0155] In addition, as a bubble control agent, one type represented by the following abbreviation "NA1" was prepared.

[0156] NA1: Masterbatch containing azodicarbonamide

[0157] (Example 1)

[0158] (Production of Resin Foam Sheet)

[0159] (Manufacturing Example a)

[0160] Polyethylene resin "PE1", polymer antistatic agent "AS1", surfactant "SA1", and bubble regulator "NA1" were blended in the proportions shown in Table 1 to prepare a mixture.

[0161] A circular die with an outlet diameter of 100 mm (slit width of 0.2 mm) was attached to the front end of a tandem extruder (front end of the second extruder) in which two extruders, a first extruder and a second extruder, were sequentially connected in the extrusion direction.

[0162] The mixture was supplied to the first extruder of a tandem extruder and melt-kneaded in the first extruder. A butane mixture (isobutane / n-butane = 50 / 50 (molar ratio)) as a foaming agent was injected from the middle of the first extruder and melt-kneaded further.

[0163] The injection amount of the mixed butane was adjusted to 18 parts by mass relative to 100 parts by mass of the polyethylene resin.

[0164] After melt kneading in the first extruder, the melt kneaded product was cooled to a temperature range suitable for foaming (111° C.) in a second extruder connected to the first extruder. The melt kneaded product was then extruded from the circular die in air into a cylindrical shape and foamed.

[0165] The resin temperature at this time was 116°C.

[0166] After cooling the extruded cylindrical foam by blowing air, the foam was placed on a cooling mandrel with a diameter of 380 mm and a length of 500 mm and cooled. The cylindrical foam was cut along the extrusion direction using a cutter located on the rear side of the cooling mandrel. The resulting strip of foamed sheet was then wound at a speed of 20 m / min to produce a long strip of foamed sheet. This produced the resin foam sheet (single foam layer) of Production Example (a) of Example 1.

[0167] (Manufacturing Example b)

[0168] A resin foam sheet was produced in the same manner as in Production Example (a) except that the fatty acid compound "FA1" was contained in the ratio shown in Table 1 below.

[0169] (Examples 2 to 4)

[0170] A resin foam sheet having a single foam layer was prepared in the same manner as in Example 1 except that the materials used were changed to those shown in Table 1 below.

[0171] (Example 5)

[0172] Using the same resin composition as in Example 1, a resin foam sheet having a three-layer structure including non-foamed layers on both sides of the foamed layer was produced.

[0173] Specifically, a resin foam sheet was produced as follows.

[0174] The raw materials for forming the foam layer are supplied to one of two extruders connected to a converging die, while the raw materials for forming the non-foam layer are supplied to the other extruder. These two raw materials are co-extruded through a single die to produce a three-layer resin foam sheet consisting of non-foam layer / foam layer / non-foam layer.

[0175] It should be noted that, in Example 1, the amount of mixed butane used was 18 parts by mass, but when forming the foamed layer of Example 5, the amount of mixed butane used was changed to 6 parts by mass.

[0176] In Production Example b of Example 5, the fatty acid compound (FA1) was added only to the non-foamed layer.

[0177] [Table 1]

[0178]

[0179] (Comparative Examples 1 to 4)

[0180] A resin foam sheet having a single foam layer was prepared in the same manner as in Example 1 except that the materials used were changed to those shown in Table 2 below.

[0181] [Table 2]

[0182]

[0183] (Preparation of Glass for Migration Evaluation)

[0184] According to the following procedure, a fatty acid compound and a surfactant were allowed to migrate from the resin foam sheet obtained by the above-described production method to glass to prepare glass for evaluating the migration amount.

[0185] Two test pieces of 60 mm×80 mm were cut out from randomly selected positions of the resin foam sheets obtained by the production methods of Examples and Comparative Examples.

[0186] Prepare a glass plate of 50 mm × 75 mm in size, and sandwich the glass plate from top to bottom with two test pieces cut out from the resin foam sheet to form a Figure 5 The stack shown.

[0187] The laminate L was produced so that both the upper surface and the lower surface of the glass plate G were entirely covered with the test piece S.

[0188] The laminate L was placed in a high-temperature, high-humidity tank manufactured by Isuzu Corporation and maintained at 50°C and 90% RH for 240 hours to allow the stearic acid amide and surfactant contained in the test piece to migrate to the glass plate.

[0189] At this time, an iron weight W weighing 2 kg and measuring 50 mm in width, 100 mm in length, and 50 mm in height was placed on the laminate L to prevent the test piece from shifting in the high-temperature, high-humidity tank.

[0190] The weight W is placed on the laminate L so that a load is applied to the entire surface of the glass plate G and the longitudinal direction thereof is aligned with the longitudinal direction of the glass plate G.

[0191] Then, the glass plate G after 240 hours had passed was used as glass for evaluating the migration amount.

[0192] (Measurement method)

[0193] Using the glass for migration evaluation obtained by the above method, the migration amounts of fatty acid compounds and surfactants were measured.

[0194] The measurement was performed by the LC / MS / MS method shown below.

[0195] (LC / MS / MS method)

[0196] The migration of fatty acid compounds (stearic acid amide) and surfactants (sodium alkyl sulfonate) into the migration evaluation glass were measured by extracting stearic acid amide and sodium alkyl sulfonate adhering to the migration evaluation glass with methanol. The measurements were performed using a liquid chromatography linear ion trap mass spectrometer (LC / MSn).

[0197] In addition, the amounts of stearic acid amide and sodium alkylsulfonate were measured using "UHPLC ACCELA" manufactured by Thermo Fisher Scientific and "Linear Ion Trap LC / MSn LXQ" manufactured by Thermo Fisher Scientific as LC / MSn apparatuses.

[0198] In addition, the amount of stearic acid amide was measured by the method shown below.

[0199] (Evaluation of Migration Amount of Fatty Acid Compound (Stearic Acid Amide))

[0200] (Measurement method)

[0201] A piece of glass for migration evaluation was placed in a 120 mm x 170 mm sealed bag (manufactured by ASKUL), 5 mL of methanol was further injected, and the bag was sealed.

[0202] The sealed bag containing the glass for migration evaluation and methanol was shaken about 50 times, and the methanol in the bag was collected.

[0203] The collected methanol was measured by the above-mentioned LC / MSn.

[0204] The concentration (µg / mL) of stearic acid amide in methanol was determined from the peak area values ​​on the chromatogram using a previously prepared calibration curve.

[0205] It should be noted that the method for preparing the standard curve is as follows.

[0206] After preparing an approximately 1000 ppm intermediate standard solution (methanol solution) of stearic acid amide, the solution was further diluted stepwise with methanol to prepare standard solutions for preparing a calibration curve at 5 ppm, 2 ppm, 1 ppm, 0.5 ppm, and 0.2 ppm.

[0207] The standard solution for preparing the calibration curve at each concentration was measured under the following conditions to obtain the peak area value on the chromatogram of the monitoring ion (m / z) n = 284.3 → n2 = 102.0.

[0208] Each concentration and area value were plotted, and an approximate curve (quadratic curve) was obtained by the least squares method, which was used as a standard curve for quantification.

[0209] LC measurement conditions are as follows.

[0210] ·Measurement device: UHPLC ACCELA (manufactured by Thermo Fisher Scientific)

[0211] Column: Thermo Fisher Scientific Hypersil GOLD C18 1.9 μm (inner diameter 2.1 mm, length 100 mm)

[0212] Column temperature: 40°C

[0213] Mobile phase conditions: (A: 10 mM ammonium acetate / B: acetonitrile = 25 / 75)

[0214] Volume: 0.3 mL / min

[0215] Pump temperature: room temperature (25°C)

[0216] Injection volume: 2 μL

[0217] Measurement time: 8 minutes

[0218] MS measurement conditions are as follows.

[0219] ·Measurement apparatus: Linear Ion Trap LC / MSn LXQ (manufactured by Thermo Fisher Scientific)

[0220] Ionization method: (ESI / positive)

[0221] Sheath Gas: 35arb

[0222] Auxiliary gas (AUX Gas): 10arb

[0223] Sweep Gas: 0arb

[0224] Spray Voltage: 5.0kV

[0225] Capillary temperature: 350°C

[0226] Capillary voltage: 20V

[0227] Tube lens voltage: 100V

[0228] Monitoring Mass (m / z): Oleamide (n = 282.2 → n² = 265.1), stearamide (n = 284.3 → n² = 102.0)

[0229] The concentration (μg / mL) of stearic acid amide in methanol and the amount of methanol (5 mL) obtained by the above measurement were accumulated to calculate the mass (μg) of stearic acid amide adhering to the glass for evaluating the migration amount.

[0230] Then, the amount of stearamide adhered per unit area (fatty acid compound migration amount (mg / m 2 )).

[0231] (Evaluation of Migration Amount of Anionic Surfactant (Sodium Alkyl Sulfonate))

[0232] (Measurement method)

[0233] A piece of glass for migration evaluation was placed in a 120 mm x 170 mm sealed bag (manufactured by ASKUL), 5 mL of methanol was further injected, and the bag was sealed.

[0234] The sealed bag containing the glass for migration evaluation and methanol was shaken about 50 times, and the methanol in the bag was collected.

[0235] The collected methanol was measured by the above-mentioned LC / MSn.

[0236] Using a pre-prepared calibration curve, sodium alkylsulfonate (µg / mL) in methanol was determined from the peak area values ​​on the chromatogram.

[0237] It should be noted that the method for preparing the standard curve is as follows.

[0238] After preparing an approximately 1000 ppm intermediate standard solution (methanol solution) of sodium alkylsulfonate, the solution was further diluted stepwise with methanol to prepare standard solutions for preparing a calibration curve at 5 ppm, 2 ppm, 1 ppm, 0.5 ppm, and 0.2 ppm.

[0239] The standard solution for preparing a calibration curve at each concentration was measured under the following conditions to obtain the peak area value on the chromatogram of the monitoring ion (m / z) n=291.3.

[0240] Each concentration and area value were plotted, and an approximate curve (quadratic curve) was obtained by the least squares method, which was used as a standard curve for quantification.

[0241] LC measurement conditions are as follows.

[0242] ·Measurement device: UHPLC ACCELA (manufactured by Thermo Fisher Scientific)

[0243] Column: Thermo Fisher Scientific Hypersil GOLD C18 1.9 μm (inner diameter 2.1 mm, length 100 mm)

[0244] Column temperature: 40°C

[0245] Mobile phase conditions: (A: 10 mM ammonium acetate / B: acetonitrile = 25 / 75)

[0246] Flow rate: 0.3mL / min

[0247] Pump temperature: room temperature (25°C)

[0248] Injection volume: 5μL

[0249] Measurement time: 3 minutes

[0250] MS measurement conditions are as follows.

[0251] ·Measurement apparatus: Linear Ion Trap LC / MSn LXQ (manufactured by Thermo Fisher Scientific)

[0252] Ionization method: (ESI / positive)

[0253] Sheath Gas: 30arb

[0254] Auxiliary gas (AUX Gas): 10arb

[0255] Sweep Gas: 0arb

[0256] Spray Voltage: 5.0kV

[0257] Capillary temperature: 260°C

[0258] Capillary voltage: -20V

[0259] Tube lens voltage: -100V

[0260] Monitoring Mass (m / z): Sodium alkylsulfonate (n=291.3)

[0261] The concentration (μg / mL) of sodium alkylsulfonate in methanol and the amount of methanol (5 mL) obtained in the above measurement were accumulated to calculate the mass (μg) of sodium alkylsulfonate adhering to the glass for evaluating migration amount.

[0262] Then, the amount of sodium alkyl sulfonate attached per unit area (anionic surfactant migration amount (mg / m 2 )).

[0263] The crystallinity of the polyethylene resin used in each of Examples and Comparative Examples was measured using a differential scanning calorimeter "DSC7000X, AS-3" manufactured by Hitachi High-Tech.

[0264] In addition, the resin foam sheet was used as a sample and the crystallinity was measured.

[0265] The specific measurement method is as described above.

[0266] These evaluation results are shown together in Tables 1 and 2.

[0267] From the above results, it is understood that the present invention can provide a resin foam sheet with little concern for the generation of deposits on a counterpart material.

[0268] Description of Reference Numerals

[0269] 1: Resin foam sheet, 2: Glass plate, 10: Foam layer, 20: Non-foam layer

Claims

1. A resin foam sheet having a single-layer structure having only one foam layer, The resin foam sheet is composed of a resin composition containing a polyethylene resin. The density of the polyethylene resin contained in the resin composition is 928 kg / m 3 Above 933kg / m 3 The polyethylene resin has a crystallinity of 44% to 58%. 2 . The resin foam sheet according to claim 1 , which is a spacer paper to be interposed between glass plates.

3. The resin foam sheet according to claim 1, wherein The resin composition includes an anionic surfactant.

4. The resin foam sheet according to claim 1, wherein The density is 930 kg / m 3 Above 932kg / m 3 Hereinafter, the crystallinity is 45% or more and 51% or less.

5. The resin foam sheet according to claim 1, wherein The crystallinity exceeds 45% and is 47% or less. The resin foam sheet according to claim 1 , having a thickness of 0.2 mm or more and 2.0 mm or less.

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