Laminated material for lid, lid, and package using lid

Abstract

The utility model relates to a laminated material for a cover, the cover and a packaging body using the cover. Provided is a laminated material for a lid, which is capable of suppressing a decrease in pressure resistance required for the lid even if an abnormal roll acts on a package using the lid thus manufactured. The laminated material (1) for lids is formed from a composite material in which a protective resin layer (11), a barrier layer (12) comprising an aluminum foil, an anchor coat layer (13), a stress relaxation layer (14), and a heat seal layer (15) are laminated in this order from one surface side of the laminated material (1) for lids. The stress relaxation layer (14) contains a mixture of a linear low-density polyethylene resin and a low-density polyethylene resin, and relaxes stress acting on the barrier layer (12).

Description

Technical Field

[0001] The utility model relates to a laminated material for a cover, a cover and a packaging body using the cover, and more specifically, to a laminated material for a cover used in a packaging body for sealing and packaging contents such as food and medicines, a cover made from the laminated material for a cover, and a packaging body using the cover.

[0002] In this specification, the term "aluminum" includes not only pure aluminum but also aluminum alloys. Background Art

[0003] Conventionally, as a package for sealing and packaging the above-mentioned content, a package including: a container with an upper opening; and a lid whose outer peripheral edge is heat-sealed to the peripheral edge of the opening of the container so as to cover the opening of the container has been widely used.

[0004] As a laminated material for a lid for making the lid of the above-mentioned packaging body, a laminated material for a lid is known that comprises the following composite material, wherein an aluminum foil, an anchor coating, a stress relief layer formed by low-density polyethylene, and a hot-melt adhesive layer as a heat-sealing layer are laminated in sequence from one side of the laminated material for the lid (see patent document 1, paragraph

[0070] ).

[0005] The lid formed of the lid laminate material described in Patent Document 1 is heat-sealed to the opening periphery of a synthetic resin container that has an opening at the top and contains contents by, for example, high-frequency induction heating, thereby obtaining a packaging body. That is, after the lid is covered on the periphery of the opening of the container filled with contents in a manner of covering the opening, the aluminum foil of the lid is heated by a high-frequency induction heating sealing device, and the hot-melt resin adhesive layer is melted by the heat, so that the opening periphery of the container and the lid are heat-sealed. In addition, the aluminum foil of the lid formed of the lid laminate material described in Patent Document 1 also functions as a barrier layer for protecting the contents from gas, water vapor, light, etc.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-95142 Utility Model Content

[0009] Issues to be Solved by Utility Models

[0010] However, for a package obtained by heat-sealing a cover made of the cover laminate material described in Patent Document 1 to a container, there is a concern that the pressure resistance of the cover may decrease when a plurality of packages are transported over long distances in a packed state. The applicant speculates that the reason is as follows. That is, the aforementioned package in the packed state is subjected to long-term vibration during transportation, and especially when subjected to abnormal rolling, the packages collide with or are compressed against each other. At this time, the internal pressure of each package rises and falls, and the cover repeatedly expands and contracts. It is also believed that due to the repeated expansion and contraction of the cover, repeated stress continuously acts on the aluminum foil, accumulating periodic deformation fatigue in the aluminum foil, thereby causing cyclic fatigue, and as a result, the pressure resistance of the entire cover decreases.

[0011] The utility model provides a laminated material for a cover which can suppress a decrease in the pressure resistance required as a cover even if an abnormal rolling motion acts on a package body using the produced cover.

[0012] Means for solving problems

[0013] To achieve the above object, the present invention includes the following aspects.

[0014] 1) A laminated material for a lid, characterized in that it comprises a barrier layer formed of a metal foil and a heat seal layer formed on one side of the barrier layer, and the lid is produced by heat-sealing the heat seal layer to the peripheral edge of the opening of the container so as to cover the opening of the container containing the contents.

[0015] A stress relaxation layer is formed between the barrier layer and the heat seal layer. The layer contains a mixture of a linear low-density polyethylene resin and a low-density polyethylene resin and relaxes stress acting on the barrier layer.

[0016] 2) The laminated material for a lid according to 1) above, wherein the content of the linear low-density polyethylene resin in the mixture forming the stress relaxation layer is 5 to 40% by mass.

[0017] 3) The laminated material for lid according to 1) above, wherein the density of the linear low-density polyethylene resin is 0.87 to 0.93 g / cm 3， The density of the low-density polyethylene resin is 0.90 to 0.92 g / cm 3 .

[0018] 4) The laminate for lid according to 1) above, wherein the linear low-density polyethylene resin has a melting point of 80° C. or less as measured by differential scanning calorimetry.

[0019] 5) The laminate material for lids according to 1) above, wherein the linear low-density polyethylene resin is a metallocene-based linear low-density polyethylene resin obtained by polymerization using a metallocene catalyst.

[0020] 6) The laminated material for lid according to 1) above, wherein the stress relaxation layer is formed of a film having a tensile elongation at break (E (MD) ) is 200 to 500%, and the tensile elongation at break in the width direction (TD) perpendicular to the flow direction (E (TD) ) is 200~700%.

[0021] 7) The laminate material for a cover as described in 1) above, wherein an anchor coating is present between the barrier layer and the stress relaxation layer.

[0022] 8) The laminate material for a cover according to 1) above, wherein a protective resin layer is formed on the surface of the barrier layer opposite to the surface on the stress relaxation layer side.

[0023] 9) The laminated material for lids according to 1) above, wherein the metal foil constituting the barrier layer has a tensile strength at break of 20 to 200 MPa and a tensile elongation at break of 5 to 50%.

[0024] 10) The laminate material for a cover as described in 1) above is characterized in that the heat sealing layer is composed of a heat melting layer and a base material layer, the heat melting layer is formed of a heat-melting resin, the base material layer is formed on the surface of the stress relief layer side of the heat melting layer and is formed of a synthetic resin, and the base material layer of the heat sealing layer is bonded to the stress relief layer.

[0025] 11) The laminate material for a cover as described in 10) above, characterized in that the melt flow rate of the heat-fusible resin of the heat-fusible layer serving as the heat-sealing layer is 2 to 15 g / 10 min as measured at 190°C and a load of 2.16 kg according to JIS K7210-1 (2014).

[0026] 12) The laminated material for a cover as described in 10) above is characterized in that the heat-sealing layer is formed by a heat-sealing resin film, and the tensile strength at break in the flow direction (MD) and the tensile strength at break in the width direction (TD) perpendicular to the flow direction obtained according to JIS K7161-1 (2014) of the heat-sealing resin film are both 40 to 100 MPa.

[0027] 13) The laminate material for a lid as described in 10) above, wherein the heat-sealing layer of the heat-sealing layer is formed of a heat-sealing resin film, and under the conditions of 160 °C, 0.2 MPa, and 1 second, the heat-sealing layer is heat-sealed to a 0.3-mm-thick sheet formed of the same heat-sealing resin film as the heat-sealing resin film of the heat-sealing layer of the heat-sealing layer, and in the T-peel test in accordance with JIS K6854-3, when the laminate material for a lid and the sheet are peeled from each other under the condition of a tensile speed of 300 mm / minute, the strength is 5 to 15 N / 15 mm.

[0028] 14) The laminate material for a lid as described in 1) above, wherein the heat-sealing layer is formed of a hot-melt adhesive coated so as to cover the surface of the stress-relieving layer on the side opposite to the barrier layer.

[0029] 15) A lid, characterized in that it is formed of the laminate material for a lid according to any one of 1) to 14) above.

[0030] 16) A package, characterized in that the lid according to 15) above covers the opening peripheral portion of a container filled with contents, and the lid is heat-sealed to the opening peripheral portion of the container by the heat-sealing layer.

[0031] Effect of the utility model

[0032] In the laminate material for a lid of 1) above, a stress-relieving layer formed of a mixture of linear low-density polyethylene resin (hereinafter referred to as LLPDE) and low-density polyethylene resin (hereinafter referred to as LPDE) is formed between the barrier layer and the heat-sealing layer, and the stress acting on the barrier layer is relieved. Therefore, even when packages using lids formed of this laminate material for a lid collide with each other or are pressed due to abnormal rolling, causing the lids to repeatedly expand and contract, the repeated stress continuously acting on the metal foil as the barrier layer can be relieved by the stress-relieving layer. Therefore, the occurrence of cyclic fatigue of the metal foil as the barrier layer is suppressed, and as a result, the decrease in the pressure resistance of the entire lid is suppressed. That is, by mixing LDPE with LLDPE having a linear molecular chain with high tensile strength and rigidity, the molecular chains in the amorphous part become longer, so the stress-relieving layer becomes a layer that is not easily broken even when stretched, and the durability of the stress-relieving layer against elongation fracture (Japanese:伸び破断) is improved. As a result, the decrease in the pressure resistance of the lid due to changes in the internal pressure and external stress during the transportation of the package is suppressed, and the risk of the lid itself being damaged is greatly reduced. In addition, since the stress-relieving layer is a layer that is not easily broken even when stretched, even if fine cracks are generated in the metal foil as the barrier layer due to repeated stress, the fine cracks can be filled by the stretching of the stress-relieving layer.

[0033] According to the laminated material for lids described in 2), since the mixture forming the stress relaxation layer contains 5% by mass or more of LLDPE, the stress relaxation layer becomes a layer that is easy to stretch reliably and is not easily damaged, compared with the case where the stress relaxation layer is formed of LDPE alone. In addition, since the content of LLDPE in the mixture forming the stress relaxation layer is 40% by mass or less, in a package body in which the opening of a container is heat-sealed by a lid made of the laminated material for lids, when a straw or the like is inserted into the lid, fibrous resin is not likely to remain around the pierced hole, which is hygienic.

[0034] According to the laminated material for lids of 3), since the density of LLDPE in the mixture forming the stress relaxation layer is 0.87 to 0.93 g / cm 3 Therefore, the stress relief layer has a molecular chain of appropriate length, and as a result, it is prevented from becoming too hard, and the stress relief layer is not easily damaged even if it is stretched. That is, by making the density of LLDPE within the above range, the dispersibility with LDPE is good and it is not easily damaged. From the perspective of improving the resistance to straw penetration, the density of LLDPE is preferably 0.87 to 0.90 g / cm 3 In addition, by setting the lower limit of the density of LDPE in the mixture forming the stress relaxation layer to 0.90 g / cm 3 , it is possible to suppress the breakage due to excessive low molecular weight components. Similarly, by making the upper limit 0.92 g / cm 3 , it is possible to prevent the stress relaxation layer from becoming too hard and difficult to stretch. Therefore, it is possible to provide sufficient strength and rigidity to the stress relaxation layer.

[0035] According to the laminated material for lids described in 4), since the melting point of LLDPE in the mixture forming the stress relaxation layer is 80°C or less, a soft and easily stretchable stress relaxation layer can be obtained. That is, since the melting point of LLDPE is 80°C or less, the crystalline component is small and the amorphous component is large, and the stress relaxation layer is soft rather than a hard stress relaxation layer. As a result, even if stress is applied, the stress relaxation layer can be stretched without breaking.

[0036] According to the laminated material for lids described in 5), the molecular weight distribution of the metallocene-based LLDPE in the mixture forming the stress relief layer becomes smaller, the low molecular weight components become less, and the components with short molecular chains become less, so that the molecules with long linear molecular chains are entangled with each other. As a result, the elasticity of the stress relief layer is improved, and even when the packaging body of the lid formed by the laminated material for lids is transported and stress is applied to the lid due to changes in the internal pressure of the packaging body, the stress relief layer becomes a layer that is not easily damaged even when stretched, and the durability of the stress relief layer against stretching fracture is improved. Therefore, the stress acting on the lid due to changes in the internal pressure during transportation and external forces is relieved, and the pressure resistance of the lid is suppressed, and the risk of damage to the lid itself is greatly reduced.

[0037] According to the cover laminate material described in 6), the stress relief layer stretches while following the metal foil as the barrier layer, so even if microcracks occur in the metal foil, damage to the stress relief layer caused by the broken end surface of the metal foil facing the cracks can be suppressed.

[0038] According to the laminated material for the cover described in 7) above, the bonding strength between the stress relief layer and the barrier layer is improved due to the action of the anchor coating, and the adhesion between the stress relief layer and the metal foil serving as the barrier layer is improved. Therefore, the endurance of the metal foil, which is higher than that of the stress relief layer, is maintained until the metal foil breaks, thereby improving the endurance to the stress acting on the cover as a whole.

[0039] According to the laminated material for a cover described in 8), the pressure resistance of the entire cover is further improved due to the effect of the protective resin layer, and the cover is not easily damaged.

[0040] According to the laminated material for a cover of 9), since the tensile strength at break and the tensile elongation at break of the metal foil as the barrier layer are within the prescribed ranges, the cover becomes more flexible to the stress acting on the cover and can be prevented from being damaged.

[0041] According to the cover laminate material of 10), the heat sealing strength between the cover formed by the cover laminate material and the container can be improved, or the strength and cushioning of the cover itself can be improved. In addition, the cover has good sealing performance against the internal pressure of the package body including the container and the cover, and the cover has good pressure resistance against the internal pressure.

[0042] If a lid formed of the lid laminate material of 11) is used, it can be more reliably heat-sealed to the opening peripheral edge of the container filled with the content in a short time during high-frequency induction heating sealing. In addition, the sealing performance of the lid against the internal pressure of the package body including the container and the lid and the crack resistance of the lid against the internal pressure are further improved, and the seal retreat, peeling of the heat-sealed portion, and the generation of micro cracks in the metal foil are more effectively suppressed.

[0043] As for the cover laminate material mentioned above 12), the overall strength is improved. In addition, if a cover formed from the cover laminate material is used, the sealing performance of the cover to the internal pressure of the packaging body including the container and the cover, and the crack resistance of the cover to the internal pressure are further improved, and the seal retreat, peeling of the heat-sealed part, and the generation of micro cracks in the metal foil are more effectively suppressed. In addition, the cover formed from the cover laminate material mentioned above 12) also has sufficient tear strength and good resistance to straw penetration. If the resistance to straw penetration is good, for example, the resistance when a straw is penetrated into the cover laminate material and the cover formed therefrom becomes small, and the straw will not bend or break.

[0044] The package formed by heat-sealing the lid formed of the lid laminate of 13) to the peripheral edge of the opening of the container does not suffer from accidental opening, lid peeling, seal backing, etc. during transportation. In addition, the opening operation can be easily performed by peeling the lid. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] [ Figure 1 ]

[0046] This is a vertical cross-sectional view showing an enlarged view of the laminate material for a cover of the present invention.

[0047] [ Figure 2 ]

[0048] This is a perspective view showing a specific example of a cover formed of the laminated material for a cover of the present invention.

[0049] [ Figure 3 ]

[0050] To show the use of Figure 2 A vertical cross-sectional view of a specific example of a packaging body of a cover.

[0051] [ Figure 4 ]

[0052] This is a vertical cross-sectional view showing another specific example of a package body using a cap formed of the laminated material for a cap of the present invention.

[0053] [ Figure 5 ]

[0054] To show Figure 3 Schematic diagram of an evaluation device for pressure resistance of a packaging body.

[0055] Description of Reference Numerals

[0056] 1: Laminated material for cover

[0057] 2, 20: Cover

[0058] 3.30: Container

[0059] 31: Opening periphery

[0060] 301: Flange

[0061] 4: Packaging

[0062] 11: Protective resin layer

[0063] 12: Barrier layer

[0064] 13: Anchor coating

[0065] 14: Stress relief layer

[0066] 15: Heat seal layer DETAILED DESCRIPTION

[0067] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the technical scope of the present invention is not limited to the embodiments shown in the accompanying drawings.

[0068] Figure 1 The laminated material for lid of the present invention is shown. Figure 2 Shown by Figure 1 A specific example of a cover formed of a laminated material, Figure 3 Shows the use of Figure 2 A specific example of a packaging body of the cover.

[0069] Figure 1 In the embodiment, the cover laminate material 1 is formed of a composite material in which a protective resin layer 11, a barrier layer 12, an anchor coating layer 13, a stress relaxation layer 14 and a heat seal layer 15 are laminated in this order from one side of the cover laminate material 1.

[0070] Figure 2 A specific example of a cover formed of the cover laminate material 1 is shown.

[0071] like Figure 2 As shown, the cover 2 made of the cover laminate material 1 is cap-shaped, including a roughly horizontal main body 2a and a skirt 2b extending in a hanging state from the periphery of the main body 2a, a protective resin layer 11 is located on the outer surfaces of the main body 2a and the skirt 2b, and a heat sealing layer 15 is located on the inner surfaces of the main body 2a and the skirt 2b.

[0072] Figure 3 Shows the use of Figure 2 The packaging body of the cover 2.

[0073] Figure 3 In the embodiment, the package body 4 includes: a bottle-shaped container 3 with an upper opening and filled with content C; and a lid 2. Preferably, at least the opening peripheral portion 31 of the container 3, for example, the entire container 3 is formed of a heat-fusible resin of the same type as the heat-fusible layer of the heat-sealing layer 15 of the lid laminate 1. The lid 2 is covered on the upper end of the container 3 in a manner of plugging the opening, and is high-frequency heat-sealed to the opening peripheral portion 31 of the container 3 by high-frequency induction heating using the heat-sealing layer 15 and the opening peripheral portion 31 of the container 3.

[0074] Figure 4 Modifications of a lid formed of the lid laminate material 1 and a package using the lid are shown.

[0075] Figure 4In the embodiment, the package body 40 includes: a cup-shaped container 30 having an outwardly facing flange 301 at the periphery of the opening and containing the content C; and a lid 20 that plugs the opening of the container 30. A heat-sealing layer containing the same type of heat-sealing resin as the heat-sealing layer 15 of the lid laminate material 1 is preferably formed on at least the upper surface of the flange 301 of the container 30. The lid 20 is in the form of a sheet as a whole, and the heat-sealing layer 15 is located on the lower surface. The outer peripheral edge of the lid 20 is placed on the flange 301 of the container 30 in a manner covering the opening of the container 30, and is high-frequency heat-sealed to the flange 301 by high-frequency induction heating using the heat-sealing layer 15 or the heat-sealing layer 15 and the heat-sealing layer on the upper surface of the flange 301.

[0076] To prevent peeling of the heat seal during transportation, Figure 3 and Figure 4 The sealing strength of the packages 4, 40 shown is preferably 15 kPa or more.

[0077] Hereinafter, each layer 11 to 15 of the laminated material 1 for a lid will be described in detail.

[0078] [Protective resin layer 11]

[0079] The protective resin layer 11 constitutes the outermost surface of the cover 2, 20 formed of the cover laminate material 1 and improves its strength, durability, weather resistance, chemical resistance, etc., and is composed of various known coating agents and / or synthetic resin films.

[0080] As the coating agent, for example, acetate resin (cellulose resin) such as nitrocellulose, acrylic resin, epoxy resin, shellac resin, polyurethane resin, etc. are used. The coating amount of the coating agent is preferably 0.5 to 1.0 g / m 2 .

[0081] As the synthetic resin film, for example, an unstretched film or a biaxially stretched film formed of polyolefin, polyester, polyamide, etc. is used. As polyolefin, examples include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), homopolypropylene (hPP), propylene-ethylene random copolymer (rPP), propylene-ethylene block copolymer (bPP), etc. As polyester, examples include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT). As polyamide, PA6 is exemplified. The wall thickness of the synthetic resin film is preferably 9 to 25 μm. The protective resin layer 11 formed by the synthetic resin film is sometimes formed by a single-layer synthetic resin film, and sometimes by a multilayer synthetic resin film in which two or more synthetic resin films of the same or different kinds are combined. The protective resin layer 11 formed by a single-layer synthetic resin film and a multilayer synthetic resin film is formed by a known method, such as an extrusion molding method (inflation, T-die, etc.), a stretching method, a lamination method, etc.

[0082] The protective resin layer 11 may be formed by combining an overcoat agent and a synthetic resin film. In this case, it is preferred that the overcoat agent is applied to the outside of the synthetic resin film, and the outermost surface of the protective resin layer 11 is formed by the overcoat layer.

[0083] A printed ink layer may be formed between the protective resin layer 11 and the barrier layer 12. The printed ink layer is formed of at least any one of characters, graphics, symbols, and patterns, and displays information about the contents of the package 4, 40 using the cap 2, 20 formed of the cap laminate material, or improves the design. When the printed ink layer is formed between the barrier layer 12 and the protective resin layer 11, a transparent protective resin layer 11 is used so that it can be visually recognized from the outside.

[0084] [Barrier layer 12]

[0085] The barrier layer 12 is a layer that protects the content C of the package 4, 40 using the cover 2, 20 made of the cover laminate material 1 from the influence of gas, water vapor, light, etc., and includes a metal foil formed of a metal such as aluminum, copper, iron (stainless steel), titanium, nickel, etc. In consideration of the barrier function, processability, cost, etc., aluminum foil is preferably used. As the aluminum foil, it is particularly preferred to use a foil formed of a soft material (O material) of 1000 series and 8000 series aluminum specified in JIS H4160:1994. Specifically, A8021H-O material, A8079H-O material, and A1N30H-O material are preferably used. The content of Si as an impurity in the A8021H-O material is preferably 0.10% by mass or less.

[0086] In addition, when the lid 2, 20 formed by the lid laminate material 1 is high-frequency heat-sealed to the opening peripheral edge portion 31 of the container 3 and the flange portion 301 of the container 30, the barrier layer 12 formed by the metal foil becomes a heating element heated by high-frequency induction. When considering the high-frequency heat sealability, the volume resistivity of the metal foil that becomes the barrier layer 12 at 25°C and the volume resistivity at 100°C are preferably both 1 to 5μΩ·cm. In this case, the heat generation during high-frequency heat sealing using high-frequency induction heating becomes good. Through high-frequency heat sealing, the heat sealing layer 15 of the lid laminate material 1 and the heat-sealing resin possessed by the container 3, 30 are fused at the molecular level, and the sealing strength is excellent. In addition, compared with the method of heating from the surface by a hot plate and heat sealing by heat conduction, since the influence of unnecessary heat is also suppressed to a minimum, the appearance of the sealed part is good, and there is no drawing or burning of the resin when opening, and the finished product is beautiful.

[0087] Furthermore, when the barrier layer 12 is formed of aluminum foil, the mass ratio of the aluminum foil to the cover laminate 1 and the cover 2, 20 formed of the cover laminate 1 is preferably 50 mass % or more. In this case, high-frequency heat sealing properties using high-frequency induction heating are improved, recycling is possible, and environmental performance is improved.

[0088] The barrier layer 12 can control the tensile strength at break and the tensile elongation at break by adjusting the type, composition, and grain structure of the metal used, and preferably has a tensile strength at break of 20 to 200 MPa and a tensile elongation at break of 5 to 50%. In this case, the package 4 or 40 using the lid 2 or 20 formed of the lid laminate 1 is more flexible to the stress acting on the lid 2 or 20, and can be prevented from being damaged.

[0089] [Anchor coating 13]

[0090] The anchor coating 13 is an optional layer formed between the barrier layer 12 and the stress relaxation layer 14 as needed. By interposing the anchor coating 13 between the barrier layer 12 and the stress relaxation layer 14, the interlayer adhesion can be improved and delamination can be prevented. The anchor coating 13 may be formed by coating a known anchor coating agent such as a polyurethane adhesive, or may be formed by subjecting the surface of the barrier layer 12 to a chemical conversion treatment. The thickness of the anchor coating 13 is not particularly limited, but is preferably 10 to 40 μm.

[0091] [Stress Relaxation Layer 14]

[0092] The stress relaxation layer 14 relaxes the stress acting on the barrier layer 12 and is formed of a mixture of LLDPE and LDPE. It should be noted that the stress relaxation layer 14 may contain inevitable impurities in addition to LLDPE and LDPE.

[0093] As the LLDPE used in the mixture forming the stress relief layer 14, it is preferred to use a metallocene-based LLPDE obtained by polymerization using a metallocene catalyst (single-site catalyst). The molecular weight distribution of the metallocene-based LLDPE is small, there are few low molecular weight components, and there are few components with short molecular chains, so the molecules with linear long molecular chains are entangled with each other. As a result, the elasticity of the stress relief layer 14 is improved. Even when the packaging body 4, 40 of the cover 2, 20 formed by the cover laminate material 1 is transported, the stress relief layer 14 becomes a layer that is not easily damaged even if stretched, and the durability of the stress relief layer 14 to stretch fracture is improved. Therefore, the stress acting on the cover 2, 20 due to the change of internal pressure and external force during transportation is relieved, and the pressure resistance of the cover 2, 20 is suppressed. As a result, the risk of damage to the cover 2, 20 itself is greatly reduced. The LLDPE used is preferably an elastomer or a plastomer. This is because the LLDPE easily returns to its original shape even when deformed by an external force.

[0094] The content of LLDPE in the mixture forming the stress relaxation layer 14 is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and desirably about 20% by mass. When the content of LLDPE in the mixture forming the stress relaxation layer 14 is 5% by mass or more, the performance that is obtained by mixing LDPE and LLDPE and is not easily broken even when stretched can be reliably obtained. In addition, if the content of LLDPE in the mixture forming the stress relaxation layer 14 is 40% by mass or less, in the packaging body 4, 40 obtained by heat-sealing the lid 2, 20 formed by the lid laminate material 1 to the opening peripheral portion 31 of the container 3 and the flange portion 301 of the container 30, when the lid 2, 20 is opened, it is not easy to produce fibrous resin residues on the opening peripheral portion 31 of the container 3 and the flange portion 301 of the container 30.

[0095] Preferably, the density of LLDPE in the mixture forming the stress relaxation layer 14 is 0.87 to 0.93 g / cm 3 Similarly, the density of LDPE is 0.90-0.92 g / cm 3 If the density of LLDPE in the mixture forming the stress relaxation layer 14 is 0.87 to 0.93 g / cm 3 , the stress relief layer 14 can have appropriate molecular chains, so it will not become too hard, and the stress relief layer 14 will not be easily damaged even if stretched. From the perspective of improving the resistance to straw penetration, the density of LLDPE is preferably 0.87 to 0.90 g / cm 3 In addition, by setting the lower limit of the density of LDPE in the mixture forming the stress relaxation layer 14 to 0.90 g / cm 3, thereby suppressing the damage caused by excessive low molecular weight components. Similarly, by making the upper limit 0.92g / cm 3 , it is possible to prevent the stress relaxation layer 14 from becoming too hard and difficult to stretch, so that a sufficient certain strength and rigidity can be given to the stress relaxation layer 14.

[0096] The melting point of LLDPE in the mixture forming the stress relief layer 14 measured by differential scanning calorimetry is below 80°C, for example, preferably 45 to 80°C, and desirably around 55°C. In this case, a soft and easily stretchable stress relief layer 14 can be made. That is, since the aforementioned melting point of LLDPE is below 80°C, it has less crystalline components and more amorphous components, resulting in a soft stress relief layer 14 rather than a hard stress relief layer 14. As a result, even if stress is applied, the stress relief layer 14 can stretch without breaking. It should be noted that, considering the sealing temperature after filling the contents, the preferred melting point range of LDPE is 90 to 120°C.

[0097] Preferably, the tensile elongation at break (E (MD) ) is 200 to 500%, and the tensile elongation at break in the width direction (TD) perpendicular to the flow direction (E (TD) ) is 200 to 700%. In this case, the stress relief layer 14 stretches while following the metal foil that becomes the barrier layer 12, so even if a microcrack is generated in the metal foil, it is possible to suppress the damage of the stress relief layer 14 caused by the broken end surface of the metal foil facing the crack. In addition, if the tensile elongation at break (E (MD) ) and the tensile elongation at break in the width direction (TD) perpendicular to the flow direction (E (TD) ) are each below the lower limit, the stress relief layer may be easily damaged by external force, and if it exceeds the upper limit, when a straw is inserted into the lid to drink the contents, the straw may be difficult to penetrate, or the stretched resin may easily become fibrous and exist around the penetration hole, thereby causing concerns about unsanitary conditions.

[0098] The thickness of the stress relief layer 14 is not particularly limited, but is preferably 10 to 50 μm. If the thickness of the stress relief layer 14 is 10 μm or more, even when the package 4 or 40 using the cover 2 or 20 formed by the cover laminate material 1 is transported and stress is applied to the cover 2 or 20 due to changes in the internal pressure of the package 4 or 40, the stress relief layer 14 suppresses damage to the cover 2 or 20 by stretching. In addition, if the thickness of the stress relief layer 14 is 50 μm or less, when the cover 2 or 20 formed by the cover laminate material 1 is heat-sealed to the container 3 or 30, the heat sealing layer 15 and the container 3 or 30 can be more reliably heat-sealed.

[0099] The stress relief layer 14 is preferably formed on the anchor coating 13 by extrusion coating. When considering the influence on the tensile elongation at break of the stress relief layer 14, the extrusion temperature is preferably in the range of 250 to 350°C. The higher the extrusion temperature, the greater the temperature difference during cooling (when the cooling rollers are in contact), so the crystalline component decreases and the amorphous component increases through the rapid cooling and solidification of the resin, and the stress relief layer 14 becomes softer, so even if stress acts, the stress relief layer 14 stretches and is not easily damaged. In addition, the stress relief layer 14 not only makes the cover 2, 20 itself formed by the cover laminate material 1 difficult to be damaged, but also has an effect on stress relief during the processing or transportation of the cover 2, 20, including the bonding and heat sealing of the heat sealing layer 15 formed by the heat-welding resin film and the metal foil that becomes the barrier layer 12.

[0100] [Heat seal layer 15]

[0101] The heat seal layer 15 is a layer for heat-sealing the lid 2, 20 formed by the lid laminate material 1 to the opening peripheral portion 31 of the container 3 and the flange portion 301 of the container 30, and is formed of a resin film having heat-fusible properties and a hot-melt adhesive. The thickness of the heat seal layer 15 is preferably 10 to 40 μm. The heat seal layer 15 is melted by the Joule heat generated in the metal foil that becomes the barrier layer 12 during high-frequency heat sealing based on high-frequency induction heating, thereby heat-sealing the lid 2 and the opening peripheral portion 31 of the container 3 and the lid 20 and the flange portion 301 of the container 30.

[0102] As the resin film forming the heat seal layer 15, for example, a multilayer film formed of different kinds of synthetic resins, a single layer film formed of one kind of synthetic resin, or a multilayer film in which a plurality of layers of the same kind of single layer film are laminated is preferably used.

[0103] As a multilayer film formed of different types of synthetic resins, a coextruded multilayer film is preferably used, which includes: a synthetic resin film as a substrate layer; and a heat-welding resin film as a heat-welding layer covering one side of the substrate layer. In the multilayer film, the substrate layer is bonded to the barrier layer 12 via the stress relaxation layer 14.

[0104] The substrate layer of the multilayer film formed by different types of synthetic resins is composed of various known synthetic resins. As the synthetic resin, for example, polyolefins and polyesters can be cited. Among these, from the aspect of the adhesion between the substrate layer and the stress relaxation layer 14, it is preferred to use a resin whose main component is the same as the stress relaxation layer 14.

[0105] The heat-sealing layer of the multilayer film formed of different types of synthetic resins preferably has as its main component the same type of heat-sealing resin as the heat-sealing resin forming the opening peripheral portion 31 of the container 3 to be heat-sealed with the lid 2, 20 formed of the lid laminate material 1 and the heat-sealing resin forming the heat-sealing layer on the upper surface of the flange portion 301 of the container 30. For example, when the heat-sealing layers formed on the opening peripheral portion 31 and the upper surface of the flange portion 301 are formed of polystyrene, the heat-sealing layers are also formed of polystyrene.

[0106] The heat-sealed layer of the multilayer film formed of different types of synthetic resins is preferably formed of a resin having a good followability and a melt flow rate of 2 to 15 g / 10 minutes measured at 190°C and a load of 2.16 kg according to JIS K7210-1 (2014). If the melt flow rate is too low, it is difficult to form a film, and if it is too high, the molecular weight is reduced, and there is a concern that the impact strength is reduced. The melt flow rate is preferably 4 to 13 g / 10 minutes. In this case, by high-frequency induction heating sealing, the lid 2, 20 formed by the lid laminate 1 can be more reliably heat-sealed to the opening peripheral portion 31 of the container 3 filled with the content and the flange portion 301 of the container 30 in a short time. In addition, the sealing performance of the lid 2, 20 to the internal pressure of the package 4, 40 containing the container 3, 30 and the lid 2, 20, and the crack resistance of the lid 2, 20 to the internal pressure are further improved, and the seal retreat, the peeling of the heat-sealed portion, and the generation of micro cracks in the metal foil are more effectively suppressed.

[0107] In addition, when the heat-welding layer of the multilayer film formed by different types of synthetic resins is formed by a heat-welding resin film, the tensile strength at break in the flow direction (MD) obtained based on JIS K7161-1 (2014) and the tensile strength at break in the width direction (TD) perpendicular to the flow direction of the heat-welding resin film are preferably both 40 to 100 MPa. The reason is that if the above two tensile strengths at break are too small, there is a concern that the strength is insufficient to prevent breakage, and if they are too large, there is sometimes a problem with the blanking adaptability when blanking into the desired shape. In this case, the overall strength is improved. In addition, if the lid 2, 20 formed by the lid laminate 1 is used, the sealing performance of the lid 2, 20 to the internal pressure of the package 4, 40 containing the container 3, 30 and the lid 2, 20, and the crack resistance of the lid 2, 20 to the internal pressure are further improved, and the seal retreat, the peeling of the heat-sealed portion, and the generation of micro cracks of the metal foil that becomes the barrier layer 12 are effectively suppressed. In addition, the lids 2 and 20 formed of the lid laminate material 1 have sufficient tear strength and good straw penetration resistance. If the straw penetration resistance is good, for example, the resistance when a straw is inserted into the lid laminate material 1 and the lids 2 and 20 formed therefrom is small, and the straw will not bend or break.

[0108] Furthermore, the heat-melting resin film of the heat-melting layer of the heat-melting layer 15 of the cover laminate 1 (which has a multilayer film formed of different kinds of synthetic resins as the heat-melting layer 15) is heat-melted to a sheet with a thickness of 0.3 mm formed of the same heat-melting resin as the heat-melting resin film under the conditions of 160°C, 0.2 MPa and 1 second, and then the strength when the cover laminate 1 and the sheet are peeled off from each other at a tensile speed of 300 mm / min in a T-peel test in accordance with JIS K6854-3 is preferably 20 N / 15 mm or less, for example, 5 to 15 N / 15 mm. In this case, the package 4, 40 formed by heat-sealing the cover 2, 20 formed of the cover laminate 1 to the opening peripheral portion 31 of the container 3 and the flange portion 301 of the container 30 does not cause accidental opening, peeling of the cover 2, 20, seal retreat, etc. during transportation. In addition, the opening operation can be easily performed by peeling off the covers 2 and 20 .

[0109] An embossed pattern having a plurality of independent convex portions can be formed on the inner surface of the cover laminate material 1. In this case, even if there are foreign objects between the cover 2, 20 and the container 3, 30 when the contents are sealed, the contents can easily escape from the sealing surface during sealing. In addition, when the cover 2, 20 formed by the cover laminate material 1 is heat-sealed to the opening peripheral portion 31 of the container 3 and the flange portion 301 of the container 30, the gas in the container 3, 30 can be discharged to the outside of the container 3, 30 through the gaps between the convex portions of the embossed pattern, so that the resistance to internal pressure cracking and the resistance to internal pressure sealing become good. In addition, the expansion of the cover 2, 20 during heat sealing can be prevented in advance, and the cover 2, 20 can be kept flat in the packaging body 4, 40.

[0110] The unsealing strength of the package 4, 40 is not particularly limited, but is preferably 20 N or less at a peeling speed of 100 mm / min and a peeling angle of 45 degrees in consideration of achieving both sealing properties and easy opening properties.

[0111] Next, examples and comparative examples of the present invention will be described.

[0112] [Examples 1 to 19]

[0113] On one side of an aluminum foil (barrier layer) having a thickness of 25 μm and formed of the A8079-O material specified in JIS H4160, a coating amount of 0.7 g / m 2 The protective resin layer is formed by coating nitrocellulose (nitrocellulose) in a manner.

[0114] On the other side of the aluminum foil, a coating amount of 0.1 g / m 2A polyurethane adhesive is applied in a manner and dried, and then a stress relief layer-forming resin comprising a mixture of Examples 1 to 19 shown in Table 1 below is extrusion-coated at the extrusion temperature shown in Table 1 to form a stress relief layer, and a multilayer film comprising a base layer (layer thickness 30 μm) formed of LDPE and a heat-sealing layer (layer thickness 30 μm) formed of a heat-sealing resin mainly composed of polystyrene is laminated on the surface of the stress relief layer by a heat lamination method to form a heat-sealing layer.

[0115] In this manner, laminated materials for lids of Examples 1 to 19 were produced.

[0116] [Comparative Examples 1-2]

[0117] On one side of an aluminum foil having a thickness of 25 μm and made of A8079-O material specified in JIS H4160, the coating amount was 0.7 g / m 2 The method is to coat nitrocellulose (nitrocellulose) to form a protective resin layer.

[0118] In addition, the coating amount was 0.1 g / m 2 A polyurethane adhesive is applied in a manner and dried, and then the stress relief layer forming resin of Comparative Examples 1 and 2 shown in Table 1 below is extrusion coated at the extrusion temperature shown in Table 1 to form a stress relief layer, and a multilayer film including a base layer (layer thickness 30 μm) formed of LDPE and a heat-sealing layer (layer thickness 30 μm) formed of a heat-sealing resin mainly composed of polystyrene is laminated on the surface of the stress relief layer by a heat lamination method to form a heat sealing layer.

[0119] In this manner, the laminated materials for lids of Comparative Examples 1 and 2 were produced.

[0120] The composition of the stress relaxation layer forming resin in the cover laminated materials of Examples 1 to 19 and Comparative Examples 1 to 2, and the extrusion temperature when the stress relaxation layer is formed on the aluminum foil are shown in Table 1. The LLDPE in the stress relaxation layer forming resin in the cover laminated materials of Examples 1 to 18 and Comparative Example 2 is a metallocene-based linear low-density polyethylene resin obtained by polymerization using a metallocene catalyst, and the LLDPE in the stress relaxation layer forming resin in the cover laminated material of Example 19 is a Ziegler-based linear low-density polyethylene resin obtained by polymerization using a Ziegler catalyst.

[0121] [Evaluation test]

[0122] Breaking tensile elongation

[0123] Test pieces with a size of 15 mm in width and 100 mm in length were prepared from extruded films with a thickness of 30 μm formed from a mixture of LDPE and LLDPE forming the stress relaxation layer of Examples 1 to 19, an extruded film formed from LDPE forming the stress relaxation layer of Comparative Example 1, and an extruded film formed from LLDPE forming the stress relaxation layer of Comparative Example 2. The tensile test of the test pieces was carried out at a tensile speed of 200 m / min using a Strograph (AGS-5kNX) manufactured by Shimadzu Corporation, and the measurement was performed.

[0124] The tensile elongation at break (E (MD) ) and the tensile elongation at break in the width direction (TD) perpendicular to the flow direction (E (TD) ) are shown in the following Table 1.

[0125] Elmendorf tear strength (Japanese: "エレメンドルフ引裂強度")

[0126] Test pieces of 75 mm in length and 63 mm in width were prepared from extruded films of 30 μm thick formed from a mixture of LDPE and LLDPE forming the stress relaxation layer of Examples 1 to 19, an extruded film of LDPE forming the stress relaxation layer of Comparative Example 1, and an extruded film of LLDPE forming the stress relaxation layer of Comparative Example 2. Four test pieces were overlapped and measured in accordance with JIS K7028-2 under the conditions of a cut distance of 2 mm, a clamp depth of 15 mm, and a load of 16 N.

[0127] The Elmendorf tear strength in the flow direction (MD) and the width direction (TD) perpendicular to the flow direction of the film forming the stress relaxation layer is shown in the following Table 1. Table 1 shows the values ​​obtained by converting the measurement results into 16 overlapping sheets. It should be noted that the "unmeasurable" in Comparative Example 2 means that it cannot be torn even at 4000 mN converted to 16 sheets.

[0128] The Elmendorf tear strength is preferably in the range of 2000 to 2500 mm in terms of a value converted to 16 sheets because it is not easily broken and can be easily processed when cutting the lid material for the lid to form the lid.

[0129] [Table 1]

[0130]

[0131] Melt flow rate of the heat-sealable layer's hot melt adhesive layer

[0132] The melt flow rates of the heat-adhesive resins forming the heat-seal layers of Examples 1 to 19 and Comparative Examples 1 and 2 were measured at 190° C. and a load of 2.16 kg in accordance with JIS K7210-1 (2014). The results are shown in Table 2 below.

[0133] Breaking tensile strength of the heat-sealable layer's hot melt adhesive layer

[0134] Based on JIS K7161-1 (2014), the tensile strength at break in the flow direction (MD) and in the width direction (TD) perpendicular to the flow direction of the heat-sealing resin films forming the heat-sealing layers of Examples 1 to 19 and Comparative Examples 1 to 2 were measured. The results are shown in Table 2 below.

[0135] Peel strength

[0136] The heat-fusible resin film, which is to be the heat-fusible layer of the heat-sealing layer 15 of Examples 1 to 19 and Comparative Examples 1 to 2, and a sheet having a thickness of 0.3 mm formed of the same heat-fusible resin as the heat-fusible resin film were heat-fused under the conditions of 160°C, 0.2 MPa, and 1 second, and then the sheets were peeled off from each other at a tensile speed of 300 mm / min in a T-peel test in accordance with JIS K6854-3, and the strength at this time was measured. The results are shown in Table 2 below.

[0137] [Table 2]

[0138]

[0139] Internal pressure resistance test

[0140] The cover laminated materials of Examples 1 to 19 and the cover laminated materials of Comparative Examples 1 to 2 were cut into test pieces of 50 mm in length and 50 mm in width. Figure 2 The cover 2 is made into the shape shown.

[0141] A polystyrene container 3 having an opening inner diameter of 36 mm, an opening outer diameter of 40 mm, an opening peripheral edge portion 31 having a thickness of 2 mm and a height of 80 mm was prepared.

[0142] Next, add 60cc of water into the container 3, then place the lid 2 on the upper end of the container 3, and high-frequency heat seal the lid 2 to the opening edge 31 of the container 3 under the conditions of an output power of 850w, a pressure of 0.2MPa, and a time of 1.0 second to obtain the packaging body 4.

[0143] Next, prepare Figure 5The evaluation device shown in the figure comprises: a storage portion 51 having a concave cross-section for setting the package body 4; a side wall portion 52 rising in a standing shape from the lower wall periphery of the storage portion 51; and a pair of abutment members 53 provided at the middle of the height of the left and right side wall portions 52. In the evaluation device 5, the storage portion 51 is connected to a driving motor not shown in the figure, and when the motor is started, the abutment member 53 of the storage portion 51 presses the package body 4 in the left and right directions shown in the figure by 6.5 mm at a predetermined number of times (e.g., 120 times / minute) within one minute.

[0144] Then, the package 4 was placed in the storage section 51 of the evaluation device 5, and the package 4 was pressed in the left and right directions shown in the figure by the contact member 53 at a frequency of 120 times / minute so that the pressing amount was 6.5 mm, and the internal pressure resistance test was performed. In the internal pressure resistance test, five sets of five package 4 were prepared, and each set was tested 10,000 times to check whether there was leakage. The results are shown in Table 3 below.

[0145] In Table 3, after the internal pressure resistance test, the case where no leakage was observed in the five packages 4 of the five groups was indicated by ◎, the case where no leakage was observed in the five packages 4 of four of the five groups was indicated by ○, the case where no leakage was observed in the five packages 4 of three of the five groups was indicated by △, and the cases other than the above were indicated by ×. The cases other than × were considered acceptable.

[0146] By meeting the qualified conditions, the packaging material containing the contents can be transported without damaging the lid even during long-distance truck transportation.

[0147] Blanking test

[0148] Ten sheets of 100 mm x 100 mm in size were prepared from the cover laminate materials of Examples 1 to 19 and Comparative Examples 1 to 2, and the ten sheets were stacked and placed in a Punch was used to punch out and 10 test pieces were made.

[0149] Then, the cut end surface of each test piece was visually inspected to confirm whether burrs were generated in the stress relaxation layer. The results are shown in Table 3.

[0150] In Table 3, the case where no burr was generated in all 10 test pieces was indicated by ◎, the case where no burr was generated in 8 to 9 test pieces was indicated by ○, the case where no burr was generated in 6 to 7 test pieces was indicated by △, and the case where no burr was generated in 5 or less test pieces was indicated by ×. The test pieces other than × were considered acceptable.

[0151] If the resin forming the stress relaxation layer is soft and easily stretched, it is not easily damaged. However, if it is too soft, it is difficult to punch out when manufacturing the cap, and the produced cap has poor penetration properties of a straw or the like.

[0152] Sealing strength

[0153] The cover laminated materials of Examples 1 to 19 and the cover laminated materials of Comparative Examples 1 to 2 were cut into test pieces of 50 mm in length and 50 mm in width. Figure 2 The cover 2 is made into the shape shown.

[0154] In addition, a polystyrene container 3 having an opening inner diameter of 36 mm, an opening outer diameter of 40 mm, an opening peripheral edge portion 31 having a thickness of 2 mm and a height of 80 mm was prepared.

[0155] Next, the lid 2 is placed on the upper end of the container 3 and the lid 2 is high frequency heat-sealed to the opening peripheral edge 31 of the container 3 under the conditions of an output of 850 W, a pressure of 0.05 MPa, and a time of 1.4 seconds to obtain a package 4 .

[0156] Next, a hole was opened in the lid 2, and air was allowed to flow in at a certain flow rate using FKT-100 manufactured by SUN CHEMICAL CO., LTD. so that the air would not leak from the hole, so that the internal pressure of the package 4 increased at a pressure increase rate of 13.3 kPa / 10 seconds. The internal pressure at the time of rupture was measured and the value was taken as the sealing strength.

[0157] The results are shown in Table 3 below. As can be seen from Table 3, all packages using lids formed of the lid laminate materials of Examples 1 to 19 and Comparative Examples 1 to 2 had a sealing strength of 15 kPa or more, and all packages except the package using the lid formed of the lid laminate material of Example 17 had a sealing strength of 100 kPa or more, and thus it can be seen that the sealing properties are sufficient. Therefore, even in long-distance truck transportation, the package can be transported without the lid 2 being peeled off from the container 3.

[0158] Opening strength

[0159] The package body 4 is obtained in the same manner as in the case of the sealing strength described above.

[0160] Next, according to JIS K6854-3 (1999), using a strograph (AGS-5kNX) manufactured by Shimadzu Corporation, the lid 2 was clamped and fixed with a chuck, the container 3 was fixed at an angle of 45°, and the peeling was performed in the vertical direction at a tensile speed of 100 mm / min to measure the peel strength at this time. The measured peel strength was taken as the unsealing strength.

[0161] The results are shown in the following Table 3. When the lid 2 is removed from the container 3 to open the package 4, it is easy to open when the opening strength is 20N or less, which is preferred, and 17N or less is more preferred. As can be seen from Table 3, in all the packages 4 using the lid 2 formed of the lid laminated materials of Examples 1 to 19 and Comparative Examples 1 to 2, the opening strength is 17N or less.

[0162] [Table 3]

[0163]

[0164] Industrial Applicability

[0165] The laminated material for a cover of the utility model is suitable for use as a cover of a package body that seals and packages food, medicines, etc. as contents.

Claims

1. A laminate material for a cover, characterized in that: A barrier layer formed of a metal foil and a heat seal layer formed on one side of the barrier layer are provided, and a lid is heat-sealed to the peripheral edge of the opening of the container by the heat seal layer so as to cover the opening of the container containing the contents. A stress relaxation layer is formed between the barrier layer and the heat seal layer. The stress relaxation layer includes a linear low-density polyethylene resin and a low-density polyethylene resin and relaxes stress acting on the barrier layer.

2. The laminate material for a cover according to claim 1, wherein: The density of the linear low-density polyethylene resin is 0.87 to 0.93 g / cm 3 The density of the low-density polyethylene resin is 0.90 to 0.92 g / cm 3 .

3. The laminate material for a cover according to claim 1, wherein: The linear low-density polyethylene resin has a melting point of 80° C. or less as measured by differential scanning calorimetry.

4. The laminate material for a cover according to claim 1, wherein: The linear low-density polyethylene resin is a metallocene-based linear low-density polyethylene resin obtained by polymerization using a metallocene catalyst.

5. The laminate material for a cover according to claim 1, wherein: The stress relaxation layer is formed of a film, and the tensile elongation at break E in the flow direction MD of the film is (MD) The tensile elongation at break in the width direction TD perpendicular to the flow direction is 200-500%. (TD) It is 200 to 700%.

6. The laminate material for a cover according to claim 1, wherein: An anchor coating is present between the barrier layer and the stress relaxation layer.

7. The laminate material for a cover according to claim 1, wherein: A protective resin layer is formed on a surface of the barrier layer opposite to a surface on the stress relaxation layer side.

8. The laminate material for a cover according to claim 1, wherein: The metal foil serving as the barrier layer has a tensile strength at break of 20 to 200 MPa and a tensile elongation at break of 5 to 50%.

9. The laminate material for a cover according to claim 1, wherein: The heat sealing layer is composed of a heat-melting layer and a base layer, the heat-melting layer is formed of a heat-melting resin, the base layer is formed on the surface of the stress relief layer side of the heat-melting layer and is formed of a synthetic resin, and the base layer of the heat sealing layer is bonded to the stress relief layer.

10. The laminate material for a cover according to claim 9, wherein: The heat-welding resin of the heat-welding layer serving as the heat-sealing layer has a melt flow rate of 2 to 15 g / 10 min as measured at 190° C. and under a load of 2.16 kg in accordance with JIS K7210-1 (2014).

11. The laminate material for a cover according to claim 9, wherein: The heat-sealing layer of the heat-sealing layer is formed of a heat-sealing resin film, and the tensile strength at break in the flow direction MD and the tensile strength at break in the width direction TD perpendicular to the flow direction obtained according to JIS K7161-1 (2014) are both 40 to 100 MPa.

12. The laminate material for a cover according to claim 9, wherein: The heat-melting layer of the heat-sealing layer is formed of a heat-melting resin film. After the heat-melting layer is heat-melted to a sheet with a thickness of 0.3 mm formed of the same heat-melting resin film as the heat-melting layer of the heat-melting layer, under the conditions of 160°C, 0.2 MPa and 1 second, the strength of the cover laminated material and the sheet when peeled off from each other at a tensile speed of 300 mm / min in a T-peel test in accordance with JIS K6854-3 is 5 to 15 N / 15 mm.

13. The laminated material for a cover according to claim 1, wherein: The heat seal layer is formed of a hot melt adhesive applied so as to cover the surface of the stress relaxation layer that faces the opposite side to the barrier layer.

14. A cover, characterized in that The cover is formed from the laminated material for a cover according to any one of claims 1 to 13.

15. A packaging body, characterized in that The cap according to claim 14 is applied to the peripheral edge of the opening of the container in which the contents are placed so as to cover the opening, and the cap is heat-sealed to the peripheral edge of the opening of the container by the heat-sealing layer.

Images