Manufacturing method of laminated foam sheets

Abstract

To provide a manufacturing method of a laminated foam sheet which forms an adhesive layer expressing excellent adhesiveness even when an apparent density is low.SOLUTION: A manufacturing method of an adhesive laminated foam sheet which has an apparent density of 20 kg / m3 or more and 200 kg / m3 or less includes co-extruding a foam layer, an adhesive layer and an intermediate layer adhering the foam layer and the adhesive layer. In the manufacturing method, the foam layer contains a low-density polyethylene and a physical foaming agent; the adhesive layer contains an acrylic thermoplastic elastomer and a volatility plasticizer; the acrylic thermoplastic elastomer is a block-copolymer of a hard segment comprising a methacrylic ester-based polymer, and a soft segment comprising an acrylic ester-based polymer; a durometer hardness of the acrylic thermoplastic elastomer is 50 or less; a volatility plasticizer in an adhesive layer-forming molten material is one or more kinds selected from the group consisting of an alcohol and a dialkyl ether; and the volatility plasticizer is 0.5 mol or more and 6.5 mol or less based on 1 kg of a polymer in the adhesive layer-forming molten material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an adhesive laminated foam sheet. [Background technology]

[0002] Polyethylene-based foam sheets, which use polyethylene-based resins as the base resin, are highly flexible and have excellent shock absorption properties, making them suitable for use as cushioning materials and protective sheets. Among these, laminated foam sheets with adhesive properties can be attached to surfaces without the need for separate adhesive materials such as tape, and are therefore used in a wide range of applications, including simple protective coverings.

[0003] As examples of adhesive laminated foam sheets, Patent Documents 1 and 2 disclose the following. In Patent Document 1, an adhesive laminated foam sheet is manufactured by transferring an adhesive layer-forming film, obtained by coating an acrylic adhesive composition onto a release film, to the surface of a foam sheet that has been subjected to corona discharge treatment. In Patent Document 2, an adhesive laminated foam sheet is manufactured by applying an acrylic adhesive solution to the surface of a foam sheet. However, these methods require steps such as transferring the adhesive layer-forming film to the foam sheet and applying and drying the acrylic adhesive solution to the foam sheet, resulting in a complex manufacturing process. Furthermore, the use of solvents to dissolve the acrylic adhesive raises concerns about increased environmental impact.

[0004] On the other hand, Patent Document 3 discloses a technology for manufacturing a laminated foam sheet with adhesive properties by laminating a foam layer and an adhesive layer using a co-extrusion method. The method of Patent Document 3 is superior in terms of productivity compared to the methods shown in Patent Documents 1 and 2, in that it involves fewer manufacturing steps. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-185310 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2010-215906 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2011-6624 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, in the technique of Patent Document 3, when attempting to produce a foamed sheet with low apparent density, there is room for improvement from the viewpoint of obtaining a laminated foamed sheet having good adhesiveness.

[0007] An object of the present invention is to provide a method for producing a laminated foamed sheet that exhibits good adhesiveness even when the apparent density is low. [Means for Solving the Problems]

[0008] The gist of the present invention is the invention shown in the following (1) to (10).

[0009] (1) By coextruding a foam layer-forming melt for forming a foam layer, an adhesive layer-forming melt for forming an adhesive layer, and an intermediate layer-forming melt for forming an intermediate layer that bonds the foam layer and the adhesive layer, a laminated structure in which the foam layer, the intermediate layer, and the adhesive layer are laminated in this order is obtained, and the apparent density is 20 kg / m 3 or more and 200 kg / m 3 or less, which is a method for producing an adhesive laminated foamed sheet, wherein the foam layer-forming melt contains low-density polyethylene and a physical foaming agent, the adhesive layer-forming melt contains an acrylic thermoplastic elastomer and a volatile plasticizer, the acrylic thermoplastic elastomer is a block copolymer of a hard segment composed of a methacrylic ester polymer and a soft segment composed of an acrylic ester polymer, the acrylic thermoplastic elastomer has a type A durometer hardness of 50 or less, The volatile plasticizer contained in the melt for forming the adhesive layer is one or more selected from the group consisting of alcohols and dialkyl ethers, A method for producing a laminated foam sheet, wherein the blending amount of the volatile plasticizer is 0.5 mol or more and 6.5 mol or less per 1 kg of the polymer contained in the adhesive layer. (2) The laminated foam sheet is non-crosslinked, The method for producing a laminated foam sheet according to (1) above. (3) The acrylic thermoplastic elastomer has a type A durometer hardness of 20 or less, The method for producing a laminated foam sheet according to (1) or (2) above. (4) The melt mass flow rate of the acrylic thermoplastic elastomer measured under conditions of 230°C and a load of 2.16 kg is 50 g / 10 min or more and 300 g / 10 min or less, The method for producing a laminated foam sheet according to any one of (1) to (3) above. (5) The melting point (Tm) of the low-density polyethylene is 100°C or more and 130°C or less, and the difference [(Tm) - (TgH)] between the melting point (Tm) of the low-density polyethylene and the glass transition temperature (TgH) of the hard segment of the acrylic thermoplastic elastomer is -30°C or more and 20°C or less, The method for producing a laminated foam sheet according to any one of (1) to (4) above. (6) The volatile plasticizer contained in the melt for forming the adhesive layer is one or more selected from the group consisting of ethanol and dimethyl ether, The method for producing a laminated foam sheet according to any one of (1) to (5) above. (7) The melt for forming the intermediate layer contains an ethylene-based copolymer, comprising, as structural units of the ethylene-based copolymer, a first structural unit derived from ethylene and a second structural unit derived from a monomer having a polar group, The method for producing a laminated foam sheet according to any one of (1) to (6) above. (8) The content ratio of the second structural unit in the ethylene-based copolymer is 10% or more and 30% or less, A method for manufacturing a laminated foam sheet as described in (7) above. (9) The basis weight of the adhesive layer is 4 g / m² 2 More than 20g / m 2 The following is: A method for manufacturing a laminated foam sheet as described in any one of (1) to (8) above. (10) The basis weight of the intermediate layer is 0.5 g / m² 2 More than 10g / m 2 The following is: A method for manufacturing a laminated foam sheet as described in any one of (1) to (9) above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for manufacturing a laminated foam sheet that enables the formation of an adhesive layer that exhibits good tackiness even when the apparent density is low. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a diagram illustrating one embodiment of a method for manufacturing a laminated foam sheet. [Figure 2] Figure 2 is a cross-sectional view illustrating one embodiment of a laminated foam sheet. [Modes for carrying out the invention]

[0012] An example of an embodiment of the present invention is described below.

[0013] However, the present invention is not limited to the embodiments described below.

[0014] [1. Method for manufacturing laminated foam sheets] The present invention relates to a method for manufacturing an adhesive laminated foam sheet (hereinafter simply referred to as a laminated foam sheet). According to the manufacturing method of the present invention, as shown in Figure 2, the laminated foam sheet 1 has a structure in which a foam layer 10, an intermediate layer 11, and an adhesive layer 12 are laminated in that order, and has an apparent density of 30 kg / m³. 3 More than 200kg / m 3The following adhesive foam sheet is obtained. Figure 2 is a cross-sectional view showing one embodiment of a laminated foam sheet obtained by the manufacturing method according to the present invention. Such a laminated foam sheet is manufactured by co-extruding (applying a co-extrusion method) a molten material for forming a foam layer, a molten material for forming an adhesive layer, and a molten material for forming an intermediate layer that adheres the foam layer and the adhesive layer. When the molten material for forming the foam layer, the molten material for forming the intermediate layer, and the molten material for forming the adhesive layer are not distinguished, they are simply referred to collectively as molten materials. Furthermore, the method of forming a laminated structure by co-extruding the molten materials is referred to as the co-extrusion method below.

[0015] (Co-extrusion method) This section describes a co-extrusion method for manufacturing laminated foam sheets. The apparatus used to carry out the co-extrusion method is not particularly limited. As an apparatus for forming a laminated foam sheet having a structure in which three layers, a foam layer, an intermediate layer, and an adhesive layer, are laminated, for example, a co-extrusion extruder (co-extrusion apparatus) as shown in Figure 1 is used. Figure 1 is a schematic diagram showing one embodiment of the configuration of a co-extrusion apparatus. The co-extrusion apparatus 100 shown in the example of Figure 1 comprises a foam layer forming extruder 40, an intermediate layer forming extruder 41, an adhesive layer forming extruder 42, and a co-extrusion die 43. The discharge ports of the foam layer forming extruder 40, the intermediate layer forming extruder 41, and the adhesive layer forming extruder 42 are connected to the co-extrusion die 43. When the foam layer forming extruder, the intermediate layer forming extruder, and the adhesive layer forming extruder are not distinguished, they are simply referred to collectively as extruders. In the example shown in Figure 1, the foam layer forming extruder 40 is a tandem extruder comprising a first extruder 40A and a second extruder 40B connected in series, while the intermediate layer forming extruder 41 and the adhesive layer forming extruder 42 are sub-extruders connected to a co-extrusion die 43 attached to the tandem extruder that forms the foam layer forming extruder 40.

[0016] In the example using the co-extrusion apparatus 100 shown in Figure 1, the co-extrusion method can be achieved by guiding the molten material for forming the foam layer, the molten material for forming the intermediate layer, and the molten material for forming the adhesive layer, which are formed inside each extruder, to the co-extrusion die 43 and simultaneously extruding them from the extrusion port of the co-extrusion die 43. In the example in Figure 1, an annular die with an annular extrusion port is used as the co-extrusion die 43. However, a flat die with a linear extrusion port may also be used as the co-extrusion die.

[0017] In the example of the co-extrusion apparatus 100 shown in Figure 1, a laminate of molten material for forming a foamed layer, molten material for forming an intermediate layer, and molten material for forming an adhesive layer is extruded in a cylindrical shape from the extrusion port of the co-extrusion die 43. When the molten material for forming the foamed layer is extruded into the atmosphere from the extrusion port of the co-extrusion die 43, it expands while foaming, forming a foamed layer, and thus a cylindrical laminated foam body 13 is formed. The cylindrical laminated foam body 13 has a structure in which a foamed layer, a layer made of molten material for forming an intermediate layer, and a layer made of molten material for forming an adhesive layer are laminated. Furthermore, as the layer made of molten material for forming the foamed layer expands, the layer made of molten material for forming an adhesive layer and the layer made of molten material for forming an intermediate layer are stretched. The cylindrical laminated foam 13 extruded from the extrusion port is cooled while being expanded from the inside with compressed air, etc., and pulled up by rollers 53, 54, etc. along a mandrel or other expanding device, thereby solidifying the foam layer, the layer composed of the molten material for forming the adhesive layer, and the layer composed of the molten material for forming the intermediate layer. This largely fixes the cellular structure formed in the foam layer. Then, the cylindrical laminated foam 13 is cut open on the expanding device. In this way, a laminated foam sheet 1 having at least a three-layer structure is obtained, with the foam layer, intermediate layer, and adhesive layer laminated in this order. The layer composed of the molten material for forming the adhesive layer and the layer composed of the molten material for forming the intermediate layer correspond to the adhesive layer and the intermediate layer, respectively, in the laminated foam sheet 1. When an annular die is used as the co-extrusion die, it is easy to manufacture wide laminated foam sheets, for example, those with a width of 1000 mm or more. Also, when an annular die is used, it is easy to manufacture thin laminated foam sheets, for example, those with an overall thickness of 3 mm or less.

[0018] When the co-extrusion die is a flat die, a laminate of a melt layer for forming a foam layer, a melt layer for forming an intermediate layer and a melt for forming an adhesive layer is extruded in a sheet form from the extrusion outlet of the flat die. When the laminate is extruded from the extrusion outlet into the atmosphere, the melt for forming a foam layer expands while foaming. Along with this, the melt layer for forming an intermediate layer and the melt layer for forming an adhesive layer are stretched. Then, the laminated foam is cooled while being taken along a width-expanding device. Thereby, a laminated foam sheet can be obtained.

[0019] From the viewpoint of stably producing a laminated foam sheet by the co-extrusion method, it is preferable that none of the melt for forming a foam layer, the melt for forming an intermediate layer and the melt for forming an adhesive layer contains a crosslinking agent.

[0020] (Melt for Forming Foam Layer) The melt for forming a foam layer contains at least low-density polyethylene and a physical foaming agent. The melt for forming a foam layer can be obtained, for example, by the following process. Low-density polyethylene and additives such as a cell regulator added as necessary are supplied to an extruder for forming a foam layer, and are melt-kneaded. Next, a physical foaming agent is press-fitted (supplied while applying pressure) into the extruder for forming a foam layer. A physical foaming agent is supplied to the melt containing the melted low-density polyethylene-based resin inside the extruder for forming a foam layer, and the melt is further kneaded, whereby the melt for forming a foam layer is obtained. The polymer contained in the melt for forming a foam layer is referred to as a first polymer.

[0021] (Low-Density Polyethylene) Low-density polyethylene (PE-LD) has a long-chain branched structure, and has a density of 910 kg / m 3 or more and 930 kg / m 3This refers to polyethylene with a density of less than 60% by mass. Low-density polyethylene is the main component of the first polymer in the molten material for forming the foamed layer. When low-density polyethylene is the main component of the first polymer, it means that the mass percentage of low-density polyethylene in the first polymer is 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and it is particularly preferable that the molten material for forming the foamed layer contains only low-density polyethylene as a polymer component at 100% by mass. By including low-density polyethylene as the main component of the first polymer, the resulting laminated foamed sheet has excellent cushioning properties.

[0022] The melting point of the low-density polyethylene is preferably between 100°C and 130°C. In this case, a foamed layer with excellent extrusion foaming properties and excellent buffering properties can be stably formed. From this viewpoint, the melting point of the low-density polyethylene contained in the foamed layer is preferably between 102°C and 125°C, more preferably between 105°C and 120°C, and even more preferably between 108°C and 115°C.

[0023] The melting point of low-density polyethylene can be measured as follows using the method for measuring the transition temperature of plastics specified in JIS K7121:2012. First, the test specimen is conditioned by setting the heating rate and cooling rate to 10°C / min, in accordance with the procedure for "measuring the melting temperature after a certain heat treatment." Then, a heat flux DSC (i.e., differential scanning calorimetry) is performed with the heating rate set to 10°C / min, and a DSC curve is obtained. The peak temperature of the endothermic peak in the obtained DSC curve is taken as the melting point. If multiple endothermic peaks appear in the DSC curve, the peak temperature of the melting peak with the largest area is taken as the melting point, with the high-temperature baseline as the reference.

[0024] (Physical foaming agent) Examples of physical blowing agents include organic and inorganic physical blowing agents. Examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, chloride hydrocarbons such as methyl chloride and ethyl chloride, and fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane. Examples of inorganic physical blowing agents include nitrogen, carbon dioxide, air, and water. The physical blowing agent used for the molten material for forming the foam layer may consist of one compound or may contain two or more compounds.

[0025] From the viewpoint of compatibility between low-density polyethylene and the physical blowing agent, and the foaming properties of the molten material for forming the foamed layer, organic physical blowing agents are preferred as the physical blowing agents used for the molten material for forming the foamed layer, and among organic physical blowing agents, n-butane, isobutane, or mixtures thereof are more preferred.

[0026] The amount of physical blowing agent can be appropriately set according to the type of blowing agent and the desired apparent density. For example, when the physical blowing agent is a mixed butane, the amount of physical blowing agent is preferably 3 to 30 parts by mass, more preferably 4 to 25 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the first polymer contained in the foam layer forming molten material. An example of a mixed butane is a mixture consisting of 30% by mass of isobutane and 70% by mass of normal butane.

[0027] (Other polymers) The molten material for forming the foamed layer may contain other polymers other than low-density polyethylene, to the extent that it does not impair the effects of the present invention. Examples of other polymers other than low-density polyethylene include thermoplastic resins such as linear low-density polyethylene (PE-LLD), high-density polyethylene (PE-HD), ethylene-vinyl acetate copolymer (EVA), and polystyrene resins, as well as elastomers such as ethylene propylene rubber and styrene-butadiene-styrene block copolymer. The content of other polymers in the molten material for forming the foamed layer is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 0 parts by mass, meaning that the polymer component constituting the molten material for forming the foamed layer consists only of low-density polyethylene. When these "other polymers" are contained in the molten material for forming the foamed layer, these "other polymers" are components constituting the first polymer.

[0028] (Additives) The molten material for forming the foam layer may contain additives. Examples of additives include foam regulators, antioxidants, heat stabilizers, weathering agents, UV absorbers, flame retardants, fillers, and antibacterial agents. As foam regulators, inorganic or organic foam regulators can be used. Examples of inorganic foam regulators include metal borate salts such as zinc borate, magnesium borate, and borax, as well as sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, and sodium bicarbonate. Examples of organic foam regulators include sodium 2,2-methylenebis(4,6-tert-butylphenyl) phosphate, sodium benzoate, aluminum benzoate, and sodium stearate. The foam regulator added to the molten material for forming the foam layer may be one compound or two or more compounds. The amount of additives included in the foaming layer forming molten material is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the first polymer included in the foaming layer forming molten material.

[0029] (Molten material for forming adhesive layer) The molten material for forming the adhesive layer contains an acrylic thermoplastic elastomer and a volatile plasticizer. The molten material for forming the adhesive layer can be obtained, for example, by the following process: The acrylic thermoplastic elastomer and the volatile plasticizer are supplied to an extruder for forming the adhesive layer and melt-kneaded. This yields the molten material for forming the adhesive layer. The polymer contained in the molten material for forming the adhesive layer is called the second polymer.

[0030] (Acrylic thermoplastic elastomer) The acrylic thermoplastic elastomer contained in the molten material for forming the adhesive layer is the main component of the second polymer in the molten material for forming the adhesive layer. The fact that the acrylic thermoplastic elastomer is the main component of the second polymer means that the mass percentage of the acrylic thermoplastic elastomer in the second polymer is 60% by mass or more, preferably 70% by mass or more, and more preferably 75% by mass or more. There is no particular upper limit to the mass percentage of the acrylic thermoplastic elastomer in the second polymer; it may be 100% by mass or 90% by mass.

[0031] Acrylic thermoplastic elastomers are block copolymers of a hard segment made of a methacrylate ester polymer and a soft segment made of an acrylic acid ester polymer.

[0032] The methacrylate ester monomers constituting the methacrylate ester polymer that forms the hard segments are preferably alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, t-butyl methacrylate, and 2-ethylhexyl methacrylate, with methyl methacrylate being more preferred. In the alkyl methacrylate ester monomers, the alkyl group may be linear or branched. When the acrylic thermoplastic elastomer has hard segments made of a methyl methacrylate copolymer, the cohesive force of the adhesive layer of the resulting laminated foam sheet can be further increased.

[0033] The acrylic ester monomers constituting the acrylic ester polymer that forms the soft segments are preferably alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate, more preferably butyl acrylate and / or 2-ethylhexyl acrylate, and even more preferably butyl acrylate. In the alkyl acrylate monomers, the alkyl group may be linear or branched. When the acrylic thermoplastic elastomer has soft segments made of a butyl acrylate copolymer, the tackiness of the resulting laminated foam sheet can be further enhanced.

[0034] Examples of the block copolymer include acrylic triblock copolymers represented by the general formula ABA and acrylic diblock copolymers represented by the general formula AB. Here, the polymer block represented by A means a hard segment made of a methacrylic ester polymer, and the copolymer block represented by B means a soft segment made of an acrylic ester polymer. From the viewpoint of further improving the adhesiveness of the resulting laminated foam sheet, an acrylic triblock copolymer is preferred. In this specification, the polymer block represented by A may be referred to as a hard segment (A). The polymer block represented by B may be referred to as a soft segment (B).

[0035] In the aforementioned acrylic thermoplastic elastomer, the mass ratio (mass%) of the hard segment (A) and the soft segment (B) is preferably 5:95 to 50:50, and more preferably 10:90 to 40:60, in the ratio of (mass ratio of hard segment (A)):(mass ratio of soft segment (B)), from the viewpoint of enhancing adhesive strength and cohesive strength in a well-balanced manner.

[0036] As an example of such an acrylic thermoplastic elastomer, a triblock copolymer of methyl methacrylate (MMA), n-butyl acrylate (nBA), MMA polymer (PMMA), n-nBA polymer (PnBA), and MMA polymer (PMMA) can be cited. In this triblock copolymer, PMMA forms the hard segment and PnBA forms the soft segment.

[0037] The weight-average molecular weight of the acrylic thermoplastic elastomer is preferably between 30,000 and 300,000, and more preferably between 50,000 and 200,000, from the viewpoint of balancing adhesiveness and cohesiveness. The weight-average molecular weight of the acrylic thermoplastic elastomer is measured as polystyrene-equivalent molecular weight by gel permeation chromatography (GPC).

[0038] (Glass transition temperature) The hard segment preferably has a glass transition temperature (TgH) of 100°C to 140°C, and more preferably 110°C to 130°C. The soft segment preferably has a glass transition temperature (TgS) in the range of -40°C to -60°C. The glass transition temperature is a value measured in accordance with the method described in JIS K7121:1987 "Method for Measuring the Transition Temperature of Plastics". Specifically, it refers to the midpoint glass transition temperature measured by differential scanning calorimetry (DSC) at a heating rate of 10°C / min after conditioning as described in 3.(3) of JIS K7121:1987. However, if a clear transition temperature is not observed in the DSC curve, the heating rate should be set to 2°C / min.

[0039] ([(Tm)-(TgH)]) Furthermore, the difference between the melting point (Tm) of the low-density polyethylene constituting the foam layer and the glass transition temperature (TgH) of the hard segment of the acrylic thermoplastic elastomer constituting the adhesive layer, [(Tm)-(TgH)], is preferably -30°C or higher from the viewpoint of suppressing excessively high extrusion temperatures, making it easier to obtain a laminated foam sheet with a low apparent density more stably, and from the viewpoint of making it easier to obtain a laminated foam sheet with high adhesiveness even when the amount of volatile plasticizer added to the molten material for forming the adhesive layer is smaller. On the other hand, from the viewpoint of further increasing the cohesive force of the obtained laminated foam sheet, it is preferably 20°C or lower. From the above viewpoint, [(Tm)-(TgH)] is more preferably -20°C or higher and 10°C or lower, even more preferably -15°C or higher and 5°C or lower, and particularly preferably -10°C or higher and 0°C or lower.

[0040] (hardness) The Type A durometer hardness (sometimes referred to as hardness) of acrylic thermoplastic elastomers is 50 or less. Hardness is determined according to ISO 7619-1 (Type A). When measuring Type A durometer hardness, the Type A durometer should be pressed firmly against the surface of the sample and the reading should be taken 15 seconds later. The measurement should be performed in an atmosphere of 23°C and 50% relative humidity.

[0041] As described later, when laminated foam sheets are manufactured by co-extrusion, the acrylic thermoplastic elastomer is affected by stretch orientation when the molten material for forming the adhesive layer is stretched, which tends to reduce the tackiness of the adhesive layer. On the other hand, in the present invention, by setting the type A durometer hardness of the acrylic thermoplastic elastomer to 50 or less, the effect of stretch orientation can be mitigated, and the tackiness of the laminated foam sheet can be improved. From the above viewpoint, the type A durometer hardness of the acrylic thermoplastic elastomer is preferably 30 or less, more preferably 25 or less, and particularly preferably 20 or less. There is no particular lower limit to the type A durometer hardness of the acrylic thermoplastic elastomer, but it is generally 5.

[0042] (Meltmass Flowrate) The melt mass flow rate (MFR) of the acrylic thermoplastic elastomer is preferably 30 g / 10 min or more and 500 g / 10 min or less. The MFR of the acrylic thermoplastic elastomer is a value measured under conditions of 230°C and a load of 2.16 kg, based on the method specified in JIS K7210-1 (2014).

[0043] When the MFR of the acrylic thermoplastic elastomer is within the above range, when a laminated foamed sheet having a foamed layer mainly composed of low-density polyethylene is manufactured by co-extrusion, even if extrusion foaming is performed at low temperatures, the molten material for forming the adhesive layer exhibits appropriate fluidity, and the adhesiveness of the laminated foamed sheet can be further enhanced. From the above viewpoint, it is preferable that the MFR of the acrylic thermoplastic elastomer is 50 g / 10 min or more and 300 g / 10 min or less, and more preferably 55 g / 10 min or more and 200 g / 10 min or less.

[0044] (Volatile plasticizer) The molten material for forming the adhesive layer contains a volatile plasticizer. The volatile plasticizer has the effect of reducing the melt viscosity of the molten material for forming the adhesive layer, and is configured to not remain in the adhesive layer of the laminated foam sheet, that is, to volatilize from the adhesive layer after co-extrusion.

[0045] The volatile plasticizer contained in the molten material for forming the adhesive layer is one or more selected from the group consisting of alcohols and dialkyl ethers. These volatile plasticizers have appropriate polarity and can appropriately plasticize the thermoplastic elastomer, improving the melt elongation of the molten material for forming the adhesive layer. As a result, the layer of the molten material for forming the adhesive layer becomes more elongated in response to the expansion of the molten material for forming the foamed layer due to foaming. Therefore, even if the extrusion temperature of the molten material for forming the adhesive layer is brought close to that of the molten material for forming the foamed layer, the risk of cracking or other damage to the adhesive layer can be suppressed. As a result, it becomes possible to stably manufacture laminated foamed sheets with a good adhesive layer and low apparent density by co-extrusion. Furthermore, the adhesiveness of the resulting laminated foamed sheets can be improved.

[0046] Examples of alcohols include aliphatic alcohols having 1 to 4 carbon atoms. Specifically, examples of alcohols include methyl alcohol, ethyl alcohol (ethanol), n-propyl alcohol, i-propyl alcohol, and butyl alcohol. Among these, ethanol is preferred because of its excellent handling and safety, as well as its ability to further enhance the adhesiveness of the laminated foam sheet. Examples of dialkyl ethers include aliphatic dialkyl ethers having 2 to 8 carbon atoms. Specifically, examples of dialkyl ethers include dimethyl ether, diethyl ether, diisopropyl ether, and dibutyl ether. Among these, dimethyl ether is preferred from the viewpoint of handling and safety. The volatile plasticizer added to the molten material for forming the adhesive layer may be one of the above-mentioned compounds or a combination of two or more.

[0047] The boiling point of the volatile plasticizer is preferably 120°C or lower, and more preferably 80°C or lower. Volatile plasticizers having a boiling point within this range tend to volatilize naturally from the adhesive layer after co-extrusion and are easily removed from the adhesive layer. The lower limit of the boiling point of the volatile plasticizer is preferably approximately -50°C.

[0048] (Amount of volatile plasticizer added) In the molten material for forming the adhesive layer, the amount of volatile plasticizer is 0.5 mol or more and 6.5 mol or less per 1 kg of the second polymer contained in the molten material. The second polymer contained in the molten material for forming the adhesive layer refers to all polymers contained in the molten material. For example, if the molten material for forming the adhesive layer contains the acrylic thermoplastic elastomer and the tackifying resin as polymers, the amount of volatile plasticizer is 0.5 mol or more and 6.5 mol or less per 1 kg of the total of the acrylic thermoplastic elastomer and the tackifying resin. By keeping the amount of volatile plasticizer within this range, it becomes easy to ensure sufficient adhesive strength of the adhesive layer. If the amount of volatile plasticizer added to the molten material for forming the adhesive layer is excessive, the adhesive layer is likely to foam due to the plasticizer, which may cause a decrease in the contact area between the adhesive layer and the object to be bonded, potentially reducing the adhesiveness. If the amount of volatile plasticizer added to the molten material for forming the adhesive layer is insufficient, the adhesive layer tends to harden easily when the molten material is stretched, due to the excessive influence of the stretch orientation of the acrylic thermoplastic elastomer. This can lead to a decrease in the adhesiveness of the resulting laminated foam sheet. Furthermore, the adhesive layer may be prone to tearing, making it impossible to obtain a good laminated foam sheet.

[0049] From the viewpoint of ensuring sufficient adhesive strength of the adhesive layer as described above, it is preferable that the amount of volatile plasticizer blended is 1.0 mol or more and 6.0 mol or less per 1 kg of the second polymer contained in the molten material for forming the adhesive layer, and more preferably 2.0 mol or more and 5.0 mol or less.

[0050] (Other polymers) The molten material for forming the adhesive layer may contain other polymers other than the acrylic thermoplastic elastomer, to the extent that it does not impair the effects of the present invention. Examples of other polymers other than the acrylic thermoplastic elastomer include tackifying resins described later, thermoplastic resins such as low-density polyethylene (PE-LD), linear low-density polyethylene (PE-LLD), and ethylene-vinyl acetate copolymer (EVA), and elastomers such as olefin-based thermoplastic elastomers. The content of other polymers in the adhesive layer is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the acrylic thermoplastic elastomer. When these "other polymers" are included in the molten material for forming the adhesive layer, these "other polymers" are components constituting the second polymer.

[0051] Examples of the tackifying resin include rosin resin, rosin ester resin, hydrogenated rosin resin, terpene resin, terpene phenol resin, petroleum-based resin, xylene resin, and styrene resin. The amount of tackifying resin added is preferably 1 to 40 parts by mass, more preferably 5 to 35 parts by mass, and particularly preferably 10 to 30 parts by mass, per 100 parts by mass of the acrylic thermoplastic elastomer.

[0052] (Additives) The molten material for forming the adhesive layer may contain additives. Examples of additives include antioxidants, heat stabilizers, weathering agents, ultraviolet absorbers, flame retardants, fillers, antibacterial agents, and lubricants. The amount of additives included in the molten material for forming the adhesive layer is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of polymer contained in the molten material for forming the adhesive layer.

[0053] (Molten material for forming the intermediate layer) The molten material for forming the intermediate layer is not particularly limited as long as it contains at least a polymer that adheres the foamed layer and the adhesive layer. The molten material for forming the intermediate layer can be obtained, for example, by the following process: A polymer is supplied to an extruder for forming the intermediate layer and melt-kneaded. This yields the molten material for forming the intermediate layer. The polymer contained in the molten material for forming the intermediate layer is called the third polymer. The third polymer preferably contains an ethylene copolymer, and the mass percentage of the ethylene copolymer in the third polymer is preferably 50% by mass or more, and more preferably 60% by mass or more.

[0054] Ethylene copolymers preferably comprise structural units derived from ethylene (first structural units) and structural units derived from monomers having polar groups (second structural units). Examples of monomers having polar groups include vinyl acetate. Structural units represent the structural parts corresponding to the monomers in the molecular structure constituting the polymer. Examples of such ethylene copolymers include copolymers of ethylene and monomers having polar groups, and copolymers of ethylene and monomers having polar groups with other monomers.

[0055] Examples of ethylene copolymers include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA), ethylene-methacrylic acid copolymer (EMAA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl methacrylate copolymer (EEMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA). From the viewpoint of making the intermediate layer difficult to peel off from both the adhesive layer and the foamed layer (from the viewpoint of improving the adhesion between the intermediate layer and the adhesive layer and between the intermediate layer and the foamed layer), the ethylene copolymer is preferably ethylene-vinyl acetate copolymer.

[0056] In ethylene copolymers, the content of structural units derived from monomers having polar groups (the content of the second structural unit) is preferably 10% by mass or more and 35% by mass or less. Having a content of 10% by mass or more and 35% by mass or less of structural units derived from monomers having polar groups in an ethylene copolymer can further improve the adhesion between the intermediate layer and the adhesive layer, and between the intermediate layer and the foamed layer in a laminated foamed sheet. From this viewpoint, it is even more preferable that the content of structural units derived from monomers having polar groups in an ethylene copolymer is 10% by mass or more and 30% by mass or less.

[0057] From the viewpoint of more stably producing laminated foam sheets with low apparent density, the melting point of the ethylene polymer is preferably 40°C to 130°C, more preferably 45°C to 110°C, even more preferably 50°C to 105°C, and particularly preferably 55°C to 90°C. The melting point of the ethylene polymer is measured by the same method as the melting point of the low-density polyethylene constituting the foam layer.

[0058] Examples of ethylene copolymers include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA), ethylene-methacrylic acid copolymer (EMAA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl methacrylate copolymer (EEMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA). From the viewpoint of making the intermediate layer difficult to peel off from both the adhesive layer and the foamed layer (from the viewpoint of improving the adhesion between the intermediate layer and the adhesive layer and between the intermediate layer and the foamed layer), the ethylene copolymer is preferably ethylene-vinyl acetate copolymer.

[0059] (Volatile plasticizer) In the molten material for forming the intermediate layer, a volatile plasticizer may be added, similar to the molten material for forming the adhesive layer. As volatile plasticizers that can be added to the molten material for forming the intermediate layer, in addition to those similar to those added to the molten material for forming the adhesive layer described above, saturated hydrocarbons with 3 to 5 carbon atoms can be used. When a volatile plasticizer is added to the molten material for forming the intermediate layer, its melt viscosity can be reduced. Therefore, by adding a volatile plasticizer to the molten material for forming the intermediate layer, it can follow the molten material for forming the foamed layer without increasing the extrusion resin temperature of the molten material, and laminated foamed sheets with low apparent density can be manufactured more stably. The volatile plasticizer added to the molten material for forming the intermediate layer is preferably a saturated hydrocarbon with 3 to 5 carbon atoms. The amount of volatile plasticizer in the molten material for forming the intermediate layer is preferably 1.0 mol to 6.0 mol, and more preferably 2.0 mol to 5.0 mol, per 1 kg of the third polymer contained in the molten material for forming the intermediate layer.

[0060] [2-Layer Foam Sheet] By the manufacturing method described above, a laminated foam sheet 1, such as the one shown in Figure 2, can be obtained. The laminated foam sheet 1 is an adhesive foam sheet having a structure in which a foam layer 10, an intermediate layer 11, and an adhesive layer 12 are laminated in that order, as described above. At least the adhesive layer is located on the outermost surface of the laminated foam sheet.

[0061] (Foam layer) The foamed layer has a structure in which a layer of foamed foam-forming molten material is foamed, and is composed of a polymer (first polymer) contained in the foam-forming molten material. In the foamed layer, low-density polyethylene is the main component of the foamed layer. Low-density polyethylene being the main component of the foamed layer means that the mass ratio of low-density polyethylene in the foamed layer is 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. There is no particular upper limit to the mass ratio of low-density polyethylene in the foamed layer, but it is generally around 95% by mass.

[0062] In the example manufacturing method described above, as shown in Figure 2, the laminated foam sheet 1 has a multilayer structure in which an intermediate layer 11 and an adhesive layer 12 are laminated in order on one surface 10A of the foam layer 10. However, a different layer from the foam layer 10 may be laminated on the other surface opposite to the other surface (in Figure 2, the surface 10B opposite to the surface 10A facing the intermediate layer 11). The other layer may be the intermediate layer 11 or the adhesive layer 12 as described above, or it may be a different layer from the intermediate layer 11 or the adhesive layer 12. Furthermore, as will be described later, the intermediate layer may have a multilayer structure as long as it is located between the foam layer and the adhesive layer and can bond the foam layer and the adhesive layer together.

[0063] (Adhesive layer) The adhesive layer is composed of a polymer (second polymer) contained in the molten material for forming the adhesive layer. In the adhesive layer, an acrylic thermoplastic elastomer is the main component. The fact that an acrylic thermoplastic elastomer is the main component of the adhesive layer means that the mass percentage of the acrylic thermoplastic elastomer in the adhesive layer is 60% by mass or more, preferably 70% by mass or more, and more preferably 75% by mass or more. There is no particular upper limit to the mass percentage of the acrylic thermoplastic elastomer in the adhesive layer, but it is generally around 90% by mass.

[0064] (Area of ​​coverage of the adhesive layer) In laminated foam sheets, the basis weight of the adhesive layer is 2 g / m². 2 It is preferable that the above conditions are met. In this case, the adhesive layer can exhibit sufficient tackiness. From this viewpoint, the basis weight of the adhesive layer is 3 g / m². 2 It is more preferable that the amount be greater than or equal to 4 g / m 2 It is even more preferable that it be 5g / 2 It is particularly preferable that the above conditions are met. Furthermore, in the case of laminated foam sheets, the basis weight of the adhesive layer is 25 g / m². 2 The following is preferable. In this case, foaming of the adhesive layer and the formation of a cellular structure are more easily suppressed, and the risk of a decrease in adhesiveness can be more reliably reduced. From this viewpoint, the basis weight of the adhesive layer is 20 g / m². 2 More preferably, the following is true: 15 g / m 2It is even more preferable that the following conditions apply: 10 g / m 2 The following is particularly preferable. Note that if the adhesive layer is laminated on both sides of the laminated foam sheet, the basis weight of the adhesive layer refers to the basis weight per side.

[0065] (Measurement of basis weight) One possible method for measuring the basis weight of the adhesive layer is as follows: First, measure the average thickness of the adhesive layer. After converting the units of the average thickness of the adhesive layer, calculate the density of the adhesive layer (g / m³). 3 By multiplying by ), the basis weight of the adhesive layer (unit: g / m²) is calculated. 2 ) can be obtained. The method for measuring the average thickness of the adhesive layer is as follows: First, the laminated foam sheet is cut with a plane perpendicular to the extrusion direction. At the cut surface formed at this time, 10 measurement positions are set by dividing the length of the longitudinal direction of the cut surface (i.e., the direction perpendicular to both the extrusion direction and the thickness direction) into 11 equal parts. The cross-section of the laminated foam sheet at these measurement positions is observed using a microscope, and the thickness of the adhesive layer at each measurement position is measured. The arithmetic mean of these thicknesses is taken as the average thickness of the adhesive layer (unit: μm).

[0066] Furthermore, the basis weight of the adhesive layer can also be determined by conditions such as the discharge rate of the molten material used when carrying out the manufacturing method according to the present invention. Specifically, using the discharge rate of the molten material for forming the adhesive layer as X1 (kg / hour), the width of the laminated foam sheet (in the case of cutting open a tubular laminated foam to form a laminated foam sheet, this refers to the total circumference of the tubular laminated foam) W (unit: m), and the take-up speed of the tubular laminated foam L (m / hour), the basis weight of the adhesive layer per side (kg / m) can be determined from the formula shown in equation (1) below. 2 It is also possible to calculate the basis weight. Note that basis weight is expressed in g / m². 2 It may be converted to the appropriate unit.

[0067]

number

[0068] (Middle class) The intermediate layer is interposed between the foam layer and the adhesive layer, and adheres the foam layer and the adhesive layer together. The intermediate layer is composed of a polymer (third polymer) contained in the intermediate layer forming molten material. The intermediate layer may have a multilayer structure as long as it is located between the foam layer and the adhesive layer and can adhere the foam layer and the adhesive layer together. For example, the intermediate layer may be composed of a laminate of a first intermediate layer and a second intermediate layer formed from molten materials with different compositions. Such a laminated foam sheet can be manufactured, for example, by the following method. Specifically, a laminated foam sheet can be manufactured in which the foam layer, the first intermediate layer, the second intermediate layer and the adhesive layer are laminated in this order by co-extruding a molten material for forming a foam layer, a molten material for forming an adhesive layer, a molten material for forming the first intermediate layer, and a molten material for forming the second intermediate layer.

[0069] (Area of ​​mass in the middle layer) In laminated foam sheets, the basis weight of the intermediate layer is 0.5 g / m². 2 More than 10g / m 2 The following is preferable. If the basis weight of the intermediate layer is within this range, the risk of delamination between the foam layer and the adhesive layer can be more reliably reduced. From this viewpoint, the basis weight of the intermediate layer is 1 g / m². 2 More than 9g / m 2 More preferably, the following is true: 3 g / m 2 More than 8g / m 2 The following is even more preferable. Note that if the intermediate layer is laminated on both sides of the laminated foam sheet, the basis weight of the intermediate layer refers to the basis weight per side.

[0070] (Measurement of basis weight) The same method as the method for measuring the basis weight of the adhesive layer described above can be used to measure the basis weight of the intermediate layer.

[0071] (non-crosslinked) The laminated foam sheet obtained by the manufacturing method according to the present invention is preferably non-crosslinked. Non-crosslinked laminated foam sheet means that the foam layer, intermediate layer, and adhesive layer are all non-crosslinked. Specifically, non-crosslinked laminated foam sheet means that the insoluble matter of the laminated foam sheet obtained by the thermal xylene extraction method is 5% by mass or less. From the viewpoint of facilitating the recycling of the laminated foam sheet and further improving the cushioning properties of the resulting laminated foam sheet, the proportion of insoluble matter of the laminated foam sheet obtained by the thermal xylene extraction method is preferably 3% by mass or less, and most preferably 0%.

[0072] (Thermal xylene extraction method) The xylene-insoluble content (mass%) of laminated foam sheets by thermal xylene extraction is determined by cutting a test piece of approximately 1 g (whose exact weight is denoted as Wp(g)) from the laminated foam sheet, placing it in a 150 mL round-bottom flask, adding 100 mL of xylene, heating with a mantle heater under reflux for 6 hours, separating any remaining residue by filtering through a 100-mesh wire mesh, drying in a vacuum dryer at 80°C for at least 8 hours, measuring the weight Wm(g) of the dried material obtained, and calculating the xylene-insoluble content using the formula shown in equation (2) below. It is preferable to filter the residue quickly using a wire mesh.

[0073]

number

[0074] (Apparent density) The laminated foam sheet obtained by the manufacturing method according to the present invention has an apparent density of 20 kg / m³. 3 More than 200kg / m 3 A low-apparent adhesive foam sheet can be obtained as follows. From the viewpoint of balancing lightness, cushioning properties, etc. with mechanical strength, the apparent density of the laminated foam sheet is 30 kg / m³. 3 More than 150kg / m 3 Preferably, it is 45 kg / m 3 More than 100kg / m 3 The following is more preferable:

[0075] (Method for calculating apparent density) Apparent density of laminated foam sheets (kg / m³) 3 ) is calculated by dividing the basis weight of the laminated foam sheet by the total thickness of the laminated foam sheet, and then converting the unit to kg / m 3 It can be calculated by converting to [a certain value]. Furthermore, the overall thickness and basis weight of the laminated foam sheet can be determined using the measurement method shown below.

[0076] (Overall thickness of laminated foam sheet) A laminated foam sheet was cut perpendicular to the extrusion direction to obtain a cut surface. Ten locations were selected on this cut surface to measure the thickness. These measurement locations were determined so that they were equally spaced in the longitudinal direction of the cut surface (perpendicular to the extrusion direction of the laminated foam sheet and perpendicular to the thickness direction of the laminated foam sheet). The thickness was measured at each measurement location. The arithmetic mean of the thicknesses measured at each measurement location was calculated. This calculated value was considered to be the total thickness of the laminated foam sheet.

[0077] (Basis weight of laminated foam sheet) The basis weight of the laminated foam sheet is 1 m² 2 Mass per unit (unit: g / m³) 2 The following is determined: A square test specimen with sides of 25 mm is cut from the laminated foam sheet. The mass (g) of the test specimen is measured. Based on the dimensions and mass of the test specimen, the basis weight of the laminated foam sheet is calculated.

[0078] [3. Action and Effects] Conventional technologies for manufacturing adhesive laminated foam sheets require steps such as applying an adhesive solution, such as an acrylic adhesive solution, to the foam sheet and drying the adhesive solution (for example, Patent Documents 1 and 2 mentioned above). Therefore, the numerous manufacturing steps are problematic, and the solvent treatment used to dissolve the acrylic adhesive also increases the environmental burden. To address this, a technology has been proposed for manufacturing adhesive laminated foam sheets by laminating a foam layer and an adhesive layer using a co-extrusion method (for example, Patent Document 3 mentioned above). However, conventional laminated foam sheets manufactured using co-extrusion methods have low foaming ratios, ranging from approximately 1.1 to 3.0 times, and have only achieved a high apparent density.

[0079] In this invention, by lowering the extrusion resin temperature during co-extrusion foaming compared to conventional methods, it is possible to prevent the destruction of the bubble structure when a high foaming ratio is achieved. On the other hand, setting the extrusion resin temperature low causes the molten material for forming the adhesive layer to be stretched at a low temperature, resulting in a decrease in the adhesiveness of the adhesive layer in the resulting laminated foamed sheet, and also making the adhesive layer more prone to tearing during the manufacturing of the laminated foamed sheet. These problems become particularly pronounced when manufacturing laminated foamed sheets with low apparent density, as the layer of molten material for forming the adhesive layer is stretched more as the layer of molten material for forming the foam layer expands.

[0080] To improve the cushioning properties of a laminated foam sheet with adhesive properties, low-density polyethylene can be suitably used as the base resin constituting the foam layer. Generally, when manufacturing a laminated foam sheet with low apparent density by co-extrusion, it is preferable to set the extrusion temperature of the molten resin to a temperature close to the melting point of the base resin of the foam layer. The melting point of low-density polyethylene is relatively lower than that of high-density polyethylene or polypropylene resins.

[0081] Therefore, in a method for producing adhesive laminated foam sheets using co-extrusion, even when the base resin constituting the foam layer is a resin with a relatively low melting point, such as low-density polyethylene, in order to enable the production of low-density laminated foam sheets with adhesive properties, it is required that the adhesive layer is less prone to tearing and that the adhesive properties can be ensured even at low resin temperatures during extrusion.

[0082] According to the manufacturing method of the present invention, since the adhesive layer contains a specific acrylic thermoplastic elastomer and a specific volatile plasticizer is added to the molten material for forming the adhesive layer within a specific range, it is possible to reduce the residual stress in the adhesive layer caused by the stretch orientation of the molten material when manufacturing a laminated foam sheet with adhesive properties using the co-extrusion method. Furthermore, even when co-extrusion is performed at a low extrusion temperature, the adhesiveness of the adhesive layer can be ensured. Therefore, it is possible to stably obtain a laminated foam sheet that has excellent cushioning properties, is free from cracking in the adhesive layer even at low densities, and has sufficient adhesiveness.

[0083] Furthermore, the laminated foamed sheet obtained by the co-extrusion manufacturing method has an adhesive layer composed of the aforementioned specific acrylic thermoplastic elastomer. As described above, the thermoplastic elastomer is a block copolymer having soft segments and hard segments, and in the adhesive layer of the foamed sheet, the hard segments form a so-called pseudo-crosslinked structure through physical crosslinking called domains, so the adhesive layer is considered to be a layer with excellent cohesive force. In addition, since the soft segments exhibit tackiness under room temperature conditions, the adhesive layer is considered to exhibit excellent adhesive strength.

[0084] In the manufacturing method according to the present invention, a specific volatile plasticizer is added to the molten material for forming the adhesive layer within a specific range. Because the plasticizer is a volatile plasticizer, no plasticizer remains in the adhesive layer after it has formed, reducing the risk of contamination of the object to be adhered. Furthermore, since the acrylic thermoplastic elastomer contained in the molten material for forming the adhesive layer is polar, the plasticizer is selected to be both polar and compatible with the acrylic thermoplastic elastomer. However, if the compatibility with the acrylic thermoplastic elastomer is too high, even a slight change in the amount of plasticizer added may cause a large fluctuation in the viscosity of the molten material for forming the adhesive layer, making it impossible to stably manufacture laminated foam sheets. On the other hand, if the compatibility with the acrylic thermoplastic elastomer is too low, the molten material for forming the adhesive layer may not be sufficiently plasticized, potentially reducing its tackiness. Considering these points, one or more volatile plasticizers selected from the group consisting of alcohols and dialkyl ethers are used.

[0085] When using acrylic resin as an adhesive layer, it is generally necessary to crosslink the acrylic resin to ensure cohesive force and good adhesiveness. However, it is difficult to form an adhesive layer with a crosslinked structure by co-extrusion. In the manufacturing method according to the present invention, since a specific acrylic thermoplastic elastomer is used, the adhesive layer of the resulting laminated foam sheet forms pseudo-crosslinks in the hard segments during use, thus exhibiting sufficient cohesive force and good adhesiveness without the use of crosslinking agents. Furthermore, the migration of adhesive components to the packaged material is more easily suppressed. The above-mentioned pseudo-crosslinks can be melted and plastically deformed by melt kneading in the extruder, so the adhesive layer can be formed by co-extrusion. In addition, if the laminated foam sheet obtained by the manufacturing method according to the present invention is non-crosslinked, the recyclability of the laminated foam sheet is improved. Thus, in the manufacturing method according to the present invention, a predetermined thermoplastic elastomer is used as the resin for forming the adhesive layer. This allows for the formation of the adhesive layer by co-extrusion, the development of sufficient tackiness in the adhesive layer, the assurance of cohesive force in the adhesive layer at room temperature, and improved recyclability due to the absence of crosslinking in the adhesive layer.

[0086] Furthermore, according to the manufacturing method of the present invention, an intermediate layer is formed between the adhesive layer and the foam layer, thereby suppressing the peeling of the adhesive layer and the intermediate layer.

[0087] [4 Examples of application] The adhesive laminated foam sheet manufactured using the manufacturing method of the present invention can be attached to an object without the need for separate adhesive materials such as tape. Furthermore, because it has a foam layer with low-density polyethylene as the base resin, it is highly flexible and has excellent shock absorption, making it suitable for a wide range of applications such as cushioning materials and protective sheets for simple protective coverings.

[0088] Next, we will explain in more detail using specific examples. [Examples]

[0089] (Co-extrusion machine) The co-extrusion apparatus used consisted of a tandem extruder, which connected a first extruder and a second extruder, two sub-extruders, and a co-extrusion die to which the discharge ports of both the tandem extruder and the sub-extruders were connected. The tandem extruder was an extruder for forming the foam layer, and the two extruders were an extruder for forming the adhesive layer and an extruder for forming the intermediate layer. The co-extrusion die was an annular die with an annular extrusion port.

[0090] (The resin that makes up the adhesive layer) The elastomers shown in Table 1 were used as the resins constituting the adhesive layer of the laminated foam sheet. Each elastomer is denoted using the notation shown in the "Identification Notation" column of Table 1. Of these elastomers, those identified as LA3320, LA2330, LA2140, and LA2250 are all acrylic thermoplastic elastomers, and are ABA-type triblock copolymers with methyl methacrylate as the hard segment and butyl acrylate as the soft segment. These acrylic thermoplastic elastomers are all commercially available as grades recommended for use as adhesives. The elastomers identified as D-1320P, SIS5403, and TR2827 are all styrene thermoplastic elastomers (TPS). The elastomer identified as In-9507 is an olefin thermoplastic elastomer.

[0091] In Table 1, "Clarity," "DYNARON," and "Infuse" are trademarks.

[0092] In Table 1, the "Hardness" value represents the Type A durometer hardness. Hardness was measured according to ISO 7619-1 (Type A). Specifically, the Type A durometer was pressed against the surface of the test specimen and the reading was taken 15 seconds later. The test specimens were prepared by placing pelletized raw material (elastomer) into a mold measuring 30 mm in length, 30 mm in width, and 10 mm in thickness, and then heat-pressing it. The measurements were performed in an atmosphere of 23°C and 50% relative humidity. In addition, "MFR" in Table 1 is the melt mass flow rate (g / 10min) measured at 230°C and under a load of 2.16 kg, based on the method specified in JIS K7210-1 (2014). However, the melt mass flow rate for olefin-based thermoplastic elastomers is the value measured at 190°C and under a load of 2.16 kg. Furthermore, in Table 1, "Glass transition temperature (TgS)" refers to the glass transition temperature of the soft segment constituting the acrylic thermoplastic elastomer, and "Glass transition temperature (TgH)" refers to the glass transition temperature of the hard segment constituting the acrylic thermoplastic elastomer. The glass transition temperature is the intermediate point glass transition temperature measured by differential scanning calorimetry (DSC) in accordance with the method described in JIS K7121:1987 "Method for measuring transition temperatures of plastics". However, in measuring the glass transition temperature, the heating rate was set to 2°C / min.

[0093] (The resins that make up the foamed layer and the intermediate layer, respectively) Low-density polyethylene (PE-LD) (manufactured by ENEOS NUC, grade: NUC-8321) was prepared as the base resin for the foam layer. When describing the prepared PE-LD (manufactured by ENEOS NUC, grade: NUC-8321), 8321 may be used as an identifying designation. Low-density polyethylene (NUC-8321) has a density of 922 kg / m³. 3The melting point is 112°C, and the MFR (190°C, load 2.16 kg) is 2.4 g / 10 min. As the base resins constituting the intermediate layer, ethylene-vinyl acetate copolymer (EVA) (manufactured by Mitsui Dow Polychemicals, trade name: EV250) and EVA (manufactured by Mitsui Dow Polychemicals, trade name: EV150) were prepared. The following resins were prepared. The prepared EVA (manufactured by Mitsui Dow Polychemicals, trade name: EV250) and EVA (manufactured by Mitsui Dow Polychemicals, trade name: EV150) are designated as EV250 and EV150, respectively, for identification. The ethylene-vinyl acetate copolymer (EV250) has a melting point of 71°C and an MFR (190°C, load 2.16 kg) of 15 g / 10 min. Ethylene-vinyl acetate copolymer (EV150) has a melting point of 61°C and a MFR (at 190°C with a load of 2.16 kg) of 30 g / 10 min.

[0094] (Degeneration rate) EV250 and EV150 have different modification rates. This modification rate indicates the content (mass%) of vinyl acetate component in 100% by mass of EVA. The modification rates of EV250 and EV150 are specified in Table 2, for example, in Examples 1 and 5.

[0095] (Plasticizer) Dimethyl ether (DME), ethanol (EtOH), polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name PEG300), mixed butane (m-Bu), and water were prepared as plasticizers to be added to the molten material for forming the adhesive layer. The mixed butane consisted of 70% by mass of n-butane and 30% by mass of isobutane. Of the above plasticizers, dimethyl ether (DME) and ethanol (EtOH) correspond to the volatile plasticizers according to the present invention used in each example. In Table 3, polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name PEG300) is abbreviated as PEG300.

[0096] [Table 1]

[0097] Examples 1 to 14 For each of Examples 1 to 14, a laminated foam sheet was manufactured as shown below.

[0098] (Manufacturing of laminated foam sheets) Low-density polyethylene (LDPE8321), which serves as the base resin for forming the foamed layer shown in Tables 1 and 2, was supplied to the first extruder of a tandem extruder. The LDPE was then heated, melted, and kneaded within the first extruder to form a molten resin. During the formation of the molten resin, a foam regulator was also added to the first extruder. The amount of foam regulator added was 1 part by mass per 100 parts by mass of low-density polyethylene. A mixture of citric acid and sodium bicarbonate (FineCell Master PO217K, manufactured by Dainichi Seika Kogyo Co., Ltd.) was used as the foam regulator. "FineCell Master" is a trademark.

[0099] A mixture of molten low-density polyethylene and a foam regulator (molten resin) was supplied under pressure to the mixture in the first extruder, and the mixture was further kneaded in the first extruder. This yielded a molten material for forming a foamed layer. As the physical blowing agent, a mixed butane consisting of 70% by mass of n-butane and 30% by mass of isobutane was used. The amount of physical blowing agent used is shown in Table 2. In Table 2, "m-Bu" in the physical blowing agent column refers to the mixed butane described above. The same applies to Table 3. Furthermore, in the volatile plasticizer columns for the adhesive layer and intermediate layer in Table 2, and in the plasticizer column for the adhesive layer and the volatile plasticizer column for the intermediate layer in Table 3, where "m-Bu" is listed, m-Bu refers to the mixed butane described above. In each example in Table 2, a volatile plasticizer is used as the plasticizer during the formation of the adhesive layer and intermediate layer; therefore, the column name is indicated as "volatile plasticizer" in the plasticizer column. In each comparative example in Table 3, a volatile plasticizer is used as the plasticizer during the formation of the intermediate layer; therefore, the column for the plasticizer related to the intermediate layer is labeled "Volatile Plasticizer" and the column name is indicated. Furthermore, in Table 3, for the adhesive layer column, the column corresponding to the volatile plasticizer column in Table 2 is labeled "Plasticizer" and the column name is indicated.

[0100] The molten material for forming the foam layer obtained in the first extruder was transferred to the second extruder, where it was adjusted to a predetermined temperature.

[0101] For the extruder used to form the adhesive layer, the acrylic thermoplastic elastomers shown in Tables 1 and 2 were supplied. Additionally, the plasticizers shown in Table 2 (volatile plasticizers in Examples 1 to 14) were supplied to the extruder in the proportions shown in Table 2. These were kneaded inside the extruder to obtain a molten material for forming the adhesive layer.

[0102] For the intermediate layer formation extruder, the resin (EV250 or EV150) shown in Table 2 for forming the intermediate layer was supplied. In addition, the volatile plasticizer shown in Table 2 was supplied to the intermediate layer formation extruder in the proportions shown in Table 2. m-Bu was used as the volatile plasticizer. The m-Bu added to the intermediate layer formation molten material consisted of 70% by mass of n-butane and 30% by mass of isobutane, similar to the m-Bu described for the plasticizer added to the adhesive layer formation molten material. The intermediate layer formation molten material was obtained by kneading these together inside the intermediate layer formation extruder. In Example 14, no volatile plasticizer was added to the intermediate layer formation molten material.

[0103] The molten materials obtained from the foam layer formation extruder, the adhesive layer formation extruder, and the intermediate layer formation extruder are supplied to the co-extrusion die. At this time, the molten materials merge inside the co-extrusion die so that layers of foam layer formation molten material, intermediate layer formation molten material, and adhesive layer formation molten material are stacked from the inside out. Then, the foam layer formation molten material, adhesive layer formation molten material and adhesive layer formation molten material are discharged from the extrusion port of the co-extrusion die to obtain a tubular laminated foam. The resin temperatures (extrusion resin temperatures) at the time of discharge of the foam layer formation molten material, intermediate layer formation molten material, and adhesive layer formation molten material are shown in Table 2. The obtained tubular laminated foam was cooled by inserting a mandrel inside it and pulling the tubular laminated foam along the mandrel. At this time, the tubular laminated foam was cut open, and laminated foam sheets were obtained for each of Examples 1 to 14.

[0104] The laminated foam sheets obtained in each of Examples 1 to 14 are all laminated foam sheets having a three-layer laminated structure in which a foam layer, an intermediate layer, and an adhesive layer are laminated in that order. For the laminated foam sheets obtained in Examples 1 to 14, the percentage of insoluble matter (mass%) obtained by thermal xylene extraction was 0. That is, the foam layer, intermediate layer, and adhesive layer are all non-crosslinked.

[0105] The total thickness (mm) of the laminated foam sheets obtained in each of Examples 1 to 14 was measured. The measurement method used was the one described above. The results are shown in Table 2. Table 2 also lists the basis weights of the foam layer, intermediate layer, and adhesive layer of the laminated foam sheet. The basis weight of each layer was determined using the following formulas (3), (4), and (5) based on the amount of molten material discharged (discharge rate), the take-up rate of the laminated foam sheet, and the width of the laminated foam sheet during the manufacturing process of the laminated foam sheet (kg / m²). 2 ) g / m 2The units were converted accordingly. Note that equation (5) is the same as equation (1) above, but for the sake of explanation, it is also shown below. In Table 2, the total basis weight of the laminated foam sheet is also listed. The total basis weight of the laminated foam sheet is the sum of the basis weights of the foam layer, the intermediate layer, and the adhesive layer. Furthermore, the apparent density of the laminated foam sheet was determined from the total basis weight and total thickness of the laminated foam sheet.

[0106]

number

number

number

[0107] In equations (3), (4), and (5) above, X2 is the discharge rate of the molten material for forming the foam layer (unit: kg / hour), X3 is the discharge rate of the molten material for forming the intermediate layer, X1 is the discharge rate of the molten material for forming the adhesive layer, L is the take-up speed of the laminated foam sheet (unit: m / hour), and W is the width of the laminated foam sheet (unit: m).

[0108] The adhesive strength of the laminated foam sheets obtained in each of Examples 1 to 14 was measured as follows.

[0109] (Adhesive strength) The adhesive strength of the laminated foam sheet can be determined by measuring the peel strength. The peel strength (N / 25mm) can be determined based on a test (90° peel test) in accordance with JIS Z0237. Specifically, a test piece was prepared by punching out a rectangular shape with a width of 25 mm, a length of 100 mm, and a thickness of the total thickness from near the center of the obtained laminated foam sheet. Next, the surface on which the adhesive layer was formed was attached to the surface of the stainless steel plate (SUS304 plate) to be adhered. The attachment was performed by pressing a 2 kg roller at a speed of 600 mm / min for two back-and-forth movements under conditions of 23°C. After that, the test piece was peeled 90° using a tensile testing machine within 1 minute, and its peel strength (N / 25mm) was determined. The tensile test speed was 300 mm / min. The results are shown in Table 2. The adhesive strength of the laminated foam sheet was evaluated according to the following criteria. In all of Examples 1 to 14, it was observed that the adhesive strength of the laminated foam sheet was exhibited.

[0110] (Evaluation criteria for adhesive strength) ◎ (Excellent): Peel strength is 0.5 N / 25 mm or better. ○ (Good): The peel strength is 0.1 N / 25 mm or more and less than 0.5 N / 25 mm. × (Defective): Peel strength is less than 0.1 N / 25 mm.

[0111] Furthermore, the film formation status of the adhesive layer was evaluated for each of the laminated foam sheets obtained in Examples 1 to 14. The evaluation of the film formation status of the adhesive layer is shown below as evaluations of cracking, foaming, and delamination of the adhesive layer. The results are shown in Table 2. For all of Examples 1 to 14, the cracking, foaming, and delamination of the foam layer were evaluated as good or very good.

[0112] (Tear in the adhesive layer) The resulting laminated foam sheet was visually inspected to evaluate the degree of tearing in the adhesive layer. Specifically, a 20mm x 20mm square observation area was determined at an arbitrary position in the center of the laminated foam sheet in the width direction, and the number of tears observed within this observation area was counted. This observation was performed at five observation areas determined at equal intervals along the extrusion direction, and the arithmetic mean of the number of tears observed was used to determine the degree of tearing in the adhesive layer over 400mm. 2 The number of cracks was determined. The degree of cracking in the adhesive layer was evaluated based on this number of cracks according to the following criteria. Note that a crack in the adhesive layer refers to a hole in the adhesive layer that is 0.5 mm or longer (regardless of whether it is a through hole or not).

[0113] (Criteria for evaluating the degree of tearing in the adhesive layer) ◎ (Excellent): Adhesive layer 400mm 2 The number of successful cracks is less than one. 〇(Good): Adhesive layer 400mm 2 The number of winning tears is between 1 and 5. × (defective): Adhesive layer 400mm 2 The number of winning tears is 5 or more.

[0114] (Foaming of the adhesive layer) A scanning electron microscope (SEM) "HITACHI Miniscope TM-1000" was used to take photographs of the surface of the adhesive layer at a magnification of 100x. The foaming of the adhesive layer was evaluated based on the presence or absence of foamed areas within the observation area of ​​the photograph, and, if foamed areas were observed, the area percentage of the foamed areas, according to the following criteria. The area percentage of the foamed areas represents the proportion of the observation area occupied by the foamed areas and can be determined using image analysis of the photographs.

[0115] (Evaluation criteria for the degree of foaming of the adhesive layer) ◎ (Excellent): The area ratio of the foamed portion to the observation area of ​​the adhesive layer is less than 10%. ○ (Good): The area ratio of the foamed portion to the observation area of ​​the adhesive layer is 10% or more and less than 70%. × (Defective): The area ratio of the foamed portion to the observation area of ​​the adhesive layer is 70% or more.

[0116] (Peeling off the adhesive layer) Two rectangular test pieces were prepared by punching out a rectangle with a width of 24 mm, a length of 100 mm, and a thickness equal to the total thickness from near the center of the obtained laminated foam sheet. Next, the adhesive layers of the two test pieces were bonded together, and a 2 kg roller was applied to them at a speed of 600 mm / min for two back-and-forth passes under conditions of 23°C. After that, the test pieces were delaminated by 90° using a tensile testing machine within 1 minute. The tensile test speed was set to 300 mm / min. Subsequently, the delamination of the adhesive layers of the two test pieces was observed and evaluated according to the following criteria.

[0117] (Evaluation criteria for the degree of delamination of the adhesive layer) ◎ (Excellent): No delamination was observed in the adhesive layer of any of the test specimens. ○ (Good): Peeling is observed in at least one part of the adhesive layer. × (Defective): Complete delamination is observed in at least one of the adhesive layers.

[0118] Comparative Example 1 Comparative Example 1 is an example of manufacturing a laminated foamed sheet without forming an intermediate layer. For the molten material for forming the foamed layer, the resin and physical foaming agent shown in Table 3 were used in the proportions shown in Table 3, and a foamed layer was formed. For the molten material for forming the adhesive layer, the elastomer and plasticizer shown in Table 3 were used in the proportions shown in Table 3, and an adhesive layer was formed. Co-extrusion was performed using the molten material for forming the foamed layer and the molten material for forming the adhesive layer in the same manner as shown in Example 1, but the foamed layer and adhesive layer separated immediately after extrusion, and a laminated foamed sheet could not be obtained. Therefore, sheet properties and various evaluations (measurement of adhesive strength, evaluation of adhesive strength, and evaluation of film formation status) were not performed, and the symbol "-" is shown in Table 3.

[0119] Comparative Example 2 In Comparative Example 2, the addition of a volatile plasticizer to the molten material for forming the adhesive layer was omitted. The elastomer shown in Table 3 was used for the molten material for forming the adhesive layer. The resin and physical blowing agent shown in Table 3 were used for the molten material for forming the foamed layer in the proportions shown in Table 3. The resin and volatile plasticizer shown in Table 3 were used for the molten material for forming the intermediate layer in the proportions shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer, in the same manner as shown in Example 1, to obtain a laminated foamed sheet having a three-layer structure in which the foamed layer, intermediate layer, and adhesive layer were laminated in that order. In Table 3 and in the description herein, for the sake of convenience, even if the tackiness of the layer of the molten material for forming the adhesive layer is insufficient, the layer of the molten material for forming the adhesive layer will be referred to as the adhesive layer.

[0120] For the laminated foam sheet obtained in Comparative Example 2, the overall thickness, overall basis weight, apparent density, and adhesive strength were measured and evaluated in the same manner as in Example 1. Furthermore, for the laminated foam sheet obtained in Comparative Example 2, the tearing, foaming, and delamination of the adhesive layer were evaluated in the same manner as in Example 1. The results are shown in Table 3. The laminated foam sheet of Comparative Example 2 showed frequent tearing in the adhesive layer. It was also found that sufficient adhesive strength was not achieved.

[0121] Comparative Examples 3 and 4 Comparative Examples 3 and 4 are examples in which the amount of volatile plasticizer blended into the molten material for forming the adhesive layer was changed. Specifically, in Comparative Examples 3 and 4, the molten material for forming the adhesive layer used the elastomer and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. The molten material for forming the foamed layer used the resin and physical blowing agent shown in Table 3 in the amounts shown in Table 3. The molten material for forming the intermediate layer used the resin and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer, in the same manner as shown in Example 1. This resulted in a laminated foamed sheet having a three-layer structure in which the foamed layer, intermediate layer, and adhesive layer were laminated in that order.

[0122] For the laminated foam sheets obtained in Comparative Examples 3 and 4, the overall thickness, overall basis weight, apparent density, and adhesive strength were measured and evaluated in the same manner as in Example 1. In addition, the cracking, foaming, and peeling of the adhesive layer of the obtained laminated foam sheets were evaluated in the same manner as in Example 1. The results are shown in Table 3. In Comparative Example 3, where the amount of volatile plasticizer blended into the molten material for forming the adhesive layer was too low, cracking occurred frequently in the adhesive layer. Furthermore, it was found that sufficient adhesive strength was not obtained. In Comparative Example 4, where the amount of volatile plasticizer blended into the molten material for forming the adhesive layer was too high, the adhesive layer foamed. Furthermore, it was found that sufficient adhesive strength was not obtained.

[0123] Comparative Example 5 Comparative Example 5 is an example in which the type of volatile plasticizer blended into the molten material for forming the adhesive layer is mixed butane. Specifically, in Comparative Example 5, the molten material for forming the adhesive layer used the elastomer and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. The molten material for forming the foamed layer used the resin and physical blowing agent shown in Table 3 in the amounts shown in Table 3. The molten material for forming the intermediate layer used the resin and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer in the same manner as shown in Example 1, but the adhesive layer was not formed, and the desired laminated foamed sheet could not be obtained. Therefore, in Comparative Example 5, as in Comparative Example 1, sheet properties and various evaluations were not performed, and the symbol "-" is shown in Table 3.

[0124] Comparative Example 6 Comparative Example 6 is an example in which the elastomer blended into the molten material for forming the adhesive layer is a high-hardness acrylic thermoplastic elastomer. Specifically, in Comparative Example 6, the molten material for forming the adhesive layer used the elastomer and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. The molten material for forming the foamed layer used the resin and physical blowing agent shown in Table 3 in the amounts shown in Table 3. The molten material for forming the intermediate layer used the resin and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer, in the same manner as shown in Example 1. This resulted in a laminated foamed sheet having a three-layer structure in which the foamed layer, intermediate layer, and adhesive layer were laminated in that order.

[0125] For the laminated foam sheet obtained in Comparative Example 6, the overall thickness, overall basis weight, apparent density, and adhesive strength were measured and the adhesiveness was evaluated in the same manner as in Example 1. In addition, for the laminated foam sheet obtained in Comparative Example 6, tearing, foaming, and delamination of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 3. The laminated foam sheet of Comparative Example 6 showed frequent tearing in the adhesive layer. Furthermore, it was found that sufficient adhesive strength was not obtained.

[0126] Comparative Example 7 Comparative Example 7 is an example in which the type of plasticizer blended into the molten material for forming the adhesive layer is non-volatile PEG300. Specifically, in Comparative Example 7, the molten material for forming the adhesive layer used the elastomer and plasticizer shown in Table 3 in the amounts shown in Table 3. The molten material for forming the foamed layer used the resin and physical blowing agent shown in Table 3 in the amounts shown in Table 3. The molten material for forming the intermediate layer used the resin and volatile plasticizer shown in Table 3 in the amounts shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer, in the same manner as shown in Example 1. This resulted in a laminated foamed sheet having a three-layer structure in which the foamed layer, intermediate layer, and adhesive layer were laminated in that order.

[0127] For the laminated foam sheet obtained in Comparative Example 7, the overall thickness, overall basis weight, apparent density, and adhesive strength were measured and the adhesiveness was evaluated in the same manner as in Example 1. In addition, for the laminated foam sheet obtained in Comparative Example 7, tearing, foaming, and peeling of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 3. It was found that the laminated foam sheet of Comparative Example 7 had almost no adhesive strength.

[0128] Comparative Examples 8 to 11 Comparative Examples 8 to 11 are examples in which the type of elastomer blended into the molten material for forming the adhesive layer is an elastomer other than an acrylic thermoplastic elastomer. Specifically, the molten material for forming the adhesive layer used the elastomers and plasticizers shown in Table 3 in the amounts shown in Table 3. In Comparative Examples 8 to 10, a styrene thermoplastic elastomer was used as the resin contained in the adhesive layer. In Comparative Example 11, an olefin thermoplastic elastomer was used as the resin contained in the adhesive layer. The molten material for forming the foamed layer used the resins and physical blowing agents shown in Table 3 in the amounts shown in Table 3. The molten material for forming the intermediate layer used the resins and volatile plasticizers shown in Table 3 in the amounts shown in Table 3. By co-extrusion using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer, in the same manner as shown in Example 1, a laminated foamed sheet having a structure in which the foamed layer, the intermediate layer, and the adhesive molten material are stacked in this order was obtained. In Comparative Example 8, the foam layer and the adhesive layer did not separate even without forming an intermediate layer, so the formation of the intermediate layer was omitted.

[0129] For the laminated foam sheets obtained in Comparative Examples 8 to 11, the total thickness, total basis weight, apparent density, and adhesive strength were measured in the same manner as in Example 1, and the adhesiveness was evaluated. In addition, for the laminated foam sheets obtained in Comparative Examples 8 to 11, tearing, foaming, and peeling of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Table 3. It was found that the laminated foam sheets of Comparative Examples 8 to 11 had almost no adhesive strength.

[0130] Comparative Example 12 Comparative Example 12 is an example in which water was used as the plasticizer in the molten material for forming the adhesive layer. Specifically, in Comparative Example 12, the elastomer and plasticizer shown in Table 3 were used in the molten material for forming the adhesive layer in the amounts shown in Table 3. The resin and physical blowing agent shown in Table 3 were used in the molten material for forming the foamed layer in the amounts shown in Table 3. The resin and volatile plasticizer shown in Table 3 were used in the molten material for forming the intermediate layer in the amounts shown in Table 3. Co-extrusion was carried out using the molten material for forming the foamed layer, the molten material for forming the adhesive layer, and the molten material for forming the intermediate layer in the same manner as shown in Example 1, but the adhesive layer was not formed, and the desired laminated foamed sheet could not be obtained. Therefore, in Comparative Example 12, as in Comparative Example 1, sheet properties and various evaluations were not performed, and the symbol "-" is shown in Table 3.

[0131] [Table 2]

[0132] [Table 3]

[0133] The manufacturing method of the laminated foam sheet, the laminated foam sheet, and application examples according to the present invention have been described in detail above. However, these are merely examples, and various modifications are possible based on the technical concept of the present invention.

[0134] For example, the configurations, methods, processes, shapes, materials, and numerical values ​​mentioned above are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed. Furthermore, the configurations, methods, processes, shapes, materials, and numerical values ​​of the embodiments described above can be combined with each other, as long as they do not depart from the spirit of the present invention. [Explanation of Symbols]

[0135] 1: Laminated foam sheet 10: Foam layer 10A: Surface 10B: Surface 11: Middle Class 12: Adhesive layer 13: Cylindrical laminated foam 40: Extruder for forming foamed layers 40A: First extruder 40B: Second extruder 41: Extruder for forming intermediate layers 42: Extruder for forming adhesive layer 43: Co-extrusion die 53: Laura 54: Laura 100: Co-extruder

Claims

1. A foaming layer-forming molten material for forming a foamed layer, an adhesive layer-forming molten material for forming an adhesive layer, and an intermediate layer-forming molten material for forming an intermediate layer that adheres the foamed layer and the adhesive layer are co-extruded to form a laminated structure in which the foamed layer, the intermediate layer and the adhesive layer are stacked in this order, and the apparent density is 20 kg / m³. ３ More than 200kg / m ３ The following is a method for producing an adhesive laminated foam sheet: The molten material for forming the foamed layer comprises low-density polyethylene and a physical foaming agent. The molten material for forming the adhesive layer comprises an acrylic thermoplastic elastomer and a volatile plasticizer. The acrylic thermoplastic elastomer is a block copolymer of a hard segment made of a methacrylic acid ester polymer and a soft segment made of an acrylic acid ester polymer. The aforementioned acrylic thermoplastic elastomer has a Type A durometer hardness of 50 or less. The volatile plasticizer contained in the molten material for forming the adhesive layer is one or more selected from the group consisting of alcohols and dialkyl ethers. The amount of the volatile plasticizer blended is 0.5 mol or more and 6.5 mol or less per 1 kg of polymer contained in the molten material for forming the adhesive layer. A method for manufacturing a laminated foam sheet, wherein the mass ratio of the acrylic thermoplastic elastomer to the polymer contained in the molten material for forming the adhesive layer is 60% by mass or more.

2. The aforementioned laminated foam sheet is non-crosslinked. A method for manufacturing a laminated foam sheet according to claim 1.

3. The aforementioned acrylic thermoplastic elastomer has a Type A durometer hardness of 20 or less. A method for manufacturing a laminated foam sheet according to claim 1 or 2.

4. The melt mass flow rate of the aforementioned acrylic thermoplastic elastomer, measured at 230°C and a load of 2.16 kg, is 50 g / 10 min or more and 300 g / 10 min or less. A method for manufacturing a laminated foam sheet according to claim 1 or 2.

5. The melting point (Tm) of the low-density polyethylene is 100°C or higher and 130°C or lower, and the difference between the melting point (Tm) of the low-density polyethylene and the glass transition temperature (TgH) of the hard segment of the acrylic thermoplastic elastomer [(Tm) - (TgH)] is -30°C or higher and 20°C or lower. A method for manufacturing a laminated foam sheet according to claim 1 or 2.

6. The volatile plasticizer contained in the molten material for forming the adhesive layer is one or more selected from the group consisting of ethanol and dimethyl ether. A method for manufacturing a laminated foam sheet according to claim 1 or 2.

7. The molten material for forming the intermediate layer includes an ethylene copolymer. The ethylene copolymer comprises a first structural unit derived from ethylene and a second structural unit derived from a monomer having a polar group. A method for manufacturing a laminated foam sheet according to claim 1 or 2.

8. The content ratio of the second structural unit in the ethylene copolymer is 10% by mass or more and 30% by mass or less. A method for manufacturing a laminated foam sheet according to claim 7.

9. The basis weight of the adhesive layer is 4 g / m². ２ 20g / m or more ２ The following is: A method for manufacturing a laminated foam sheet according to claim 1 or 2.

10. The basis weight of the aforementioned intermediate layer is 0.5 g / m². ２ 10g / m or more ２ The following is: A method for manufacturing a laminated foam sheet according to claim 1 or 2.

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