Laminated material for lids and packaging containers

Abstract

Disclosed is a multilayer body for cover members, the multilayer body comprising an easily releasable layer and a sealant layer that is adjacent to the easily releasable layer, wherein: the easily releasable layer contains a high-pressure method low density polyethylene (A1), a propylene homopolymer (B) and a tackifying resin (C); the sealant layer contains a high-pressure method low density polyethylene (A2); the content of the high-pressure method low density polyethylene (A2) in the sealant layer is 50% by mass or more relative to the total mass of the sealant layer; and the sealant layer forms the outermost layer on the side where the multilayer body for cover members is in contact with an object to be bonded. Also disclosed are: a cover member which uses this multilayer body for cover members; and a packaging container which uses this cover member.

Description

[Technical Field]

[0001] This disclosure relates to laminates for lids and packaging containers. [Background technology]

[0002] For containers used for food products, pharmaceuticals, etc., paper containers (hereinafter also referred to as paper cups) in which the surface of a paper base is coated with polyethylene, impact-resistant polystyrene sheets, expanded polystyrene sheets, or those made by laminating impact-resistant polystyrene film onto these materials are widely used. Generally, containers and lids are sealed by heat-sealing them using a sealant resin composition, thereby protecting the contents. Among packaging containers, paper cups coated with polyethylene are excellent in terms of reducing environmental impact by reducing plastic usage, and also have excellent heat insulation, heat retention, and design features, making them widely used in instant noodle containers, dessert containers, beverage containers, and more.

[0003] The lid material of a packaging container requires high airtightness to protect the contents, and also requires ease of opening. For example, Japanese Patent Publication No. 2010-94860 discloses a multilayer film suitable for use as a lid material for packaging containers, addressing the issues of transparency, ease of opening, and sealability. This multilayer film has a sealant layer mainly composed of polyethylene resin and a support layer containing a propylene resin with a melting point of 155°C or higher and a polyethylene resin. Furthermore, Japanese Patent Publication No. 2004-195955 discloses a sealant film having a base layer containing a polyolefin resin and a tackifier, and a sealant layer formed from a polyolefin resin composition. Japanese Patent Publication No. 2013-111811 discloses an easily peelable film that is a two-layer film consisting of an adhesive layer made of a mixture of high-density polyethylene and low-density polyethylene, and a foamed support layer made of a mixed resin composition of high-density polyethylene, low-density polyethylene and polypropylene homopolymer. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The required level of technology for lid materials that provide easy opening for paper cups with a polyethylene coating on the surface of paper containers is becoming increasingly high. Specifically, the requirements include high sealing strength to prevent the lid from opening and the contents from leaking out during transport or storage, and easy peeling so that the lid can be easily opened when in use. Furthermore, stringing can occur when peeling the lid off a paper cup coated with polyethylene. Stringing is a phenomenon in which thin, thread-like resin forms at the peeled-off area. When stringing occurs, it can lead to a decrease in appearance, contamination of food contents with thread fragments when removing them, and a decrease in the feel of the cup's rim, significantly damaging the impression of the packaging container.

[0005] The laminated film described in Japanese Patent Publication No. 2010-94860 is said to have good transparency and good impermeability to inert gases, and the film described in Japanese Patent Publication No. 2013-111811 is said to have good peelability, but neither of these documents addresses the aspect of suppressing stringing when opening the lid. The sealant film described in Japanese Patent Publication No. 2004-195955 addresses the issues of easy peelability and suppression of stringing, but there is still room for improvement.

[0006] The problem that one embodiment of the present invention aims to solve is to provide a laminate for lids that, when used as a lid material for a container, has high sealing strength, good peelability, and suppresses stringing when opened, and a lid material including the above-mentioned laminate for lids. Another embodiment of the present invention aims to solve the problem of using the above-mentioned laminate for lid material as a lid material, which has high sealing strength, good peelability, and suppressed stringing when opened. [Means for solving the problem]

[0007] The following embodiments are included as specific means to solve the above problems. <1> A laminate for lid material comprising an easily peelable layer and a sealant layer adjacent to the easily peelable layer, wherein the easily peelable layer comprises high-pressure low-density polyethylene (A1), propylene homopolymer (B), and tackifying resin (C), the sealant layer comprises high-pressure low-density polyethylene (A2), the content of high-pressure low-density polyethylene (A2) in the sealant layer is 50% by mass or more with respect to the total mass of the sealant layer, the thickness of the easily peelable layer is 5 μm or more and 12 μm or less, and the sealant layer is the outermost layer on the side of the laminate for lid material that is in contact with the object to be adhered.

[0008] <2> The high-pressure low-density polyethylene (A1) contained in the easily peelable layer conforms to JIS K 7210-1:2014, and has a melt flow rate of 3.0 g / 10 min or more and 100 g / 10 min or less, measured under conditions of 190°C and a 2160 g load. <1> Laminate for lid material as described above. <3> The high-pressure low-density polyethylene (A2) contained in the sealant layer conforms to JIS K 7210-1:2014, and has a melt flow rate of 3.0 g / 10 min or more and 50 g / 10 min or less, measured under conditions of 190°C and a 2160 g load. <1> or <2> Laminate for lid material as described above. <4> The content of the propylene homopolymer (B) in the easily peelable layer is greater than 0% by mass and less than 40% by mass, relative to the total mass of the easily peelable layer. <1> ~ <3> A laminate for lid material as described in any one of the following.

[0009] <5> The ratio of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B) contained in the easily peelable layer ((A1):(B)=) is 80:20 to 50:50 on a mass basis. <1> ~ <4> A laminate for lid material as described in any one of the following. <6> The content of the high-pressure low-density polyethylene (A1) in the easily peelable layer is greater than 0% by mass and less than 70% by mass, relative to the total mass of the easily peelable layer. <1> ~ <5> A laminate for lid material as described in any one of the following.

[0010] <7> The total content of the high-pressure low-density polyethylene (A1), the propylene homopolymer (B), and the tackifying resin (C) in the easily peelable layer is greater than 98% by mass and less than or equal to 100% by mass, relative to the total mass of the resin components contained in the easily peelable layer. <1> ~ <6> A laminate for lid material as described in any one of the following. <8> The sealant layer further comprises an antiblocking agent. <1> ~ <7> A laminate for lid material as described in any one of the following. <9> The content of the antiblocking agent is 0.1% by mass or more and 5.0% by mass or less, relative to the total mass of the sealant layer. <8> Laminate for lid material as described above.

[0011] <10> On the side opposite to the side of the easily peelable layer that has the sealant layer, there is at least one substrate layer adjacent to the easily peelable layer. <1> ~ <9> A laminate for lid material as described in any one of the following. <11> The aforementioned substrate layer contains high-pressure low-density polyethylene (A1). <10> Laminate for lid material as described above. <12> When the laminated lid material is heat-sealed to the surface of a paper container coated with polyethylene at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, the sealing strength of the laminated lid material to the paper container exceeds 30 kPa. <1> ~ <11> A laminate for lid material as described in any one of the following. <13> When the laminate for the lid material is heat-sealed to the surface of a paper container coated with polyethylene at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, the peel strength when peeling the laminate for the lid material from the paper container is 5N or more and 20N or less. <1> ~ <12> A laminate for lid material as described in any one of the following.

[0012] <14> <1> ~ <13> A lid material including a laminate for lid materials as described in any one of the following. <15> <14> The lid material described above, and the cylindrical body, one end of which is closed and the other end of which has an opening. A packaging container comprising a container, wherein the opening is covered with the lid material through a sealant layer by heat-sealing the lid material to the opening. <16> The packaging container according to <15>, wherein the container is a paper container in which the surface of the paper base material on the side in contact with the lid material is coated with polyethylene.

Effects of the Invention

[0013] According to an embodiment of the present invention, when used as a lid material for a container, a laminate for a lid material having high sealing strength, good peelability, and suppressed stringing during opening, and a lid material including the laminate for a lid material can be provided. According to another embodiment of the present invention, a packaging container using the above lid material, having high sealing strength, good peelability, and suppressed stringing during opening can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic configuration diagram showing an example of the laminate for a lid material of the present disclosure. [Figure 2] It is a schematic configuration diagram showing another example of the laminate for a lid material of the present disclosure. [Figure 3] It is a schematic configuration diagram showing an example of a packaging container including the lid material of the present disclosure.

Modes for Carrying Out the Invention

[0015] Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0016] In the present disclosure, the numerical range indicated using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple substances. If multiple substances exist for each component, the content or amount of each component means the total content or amount of those multiple substances unless otherwise specified. In this disclosure, the terms "layer" and "film" include not only the configuration of shapes formed on the entire surface when viewed as a plan view, but also the configuration of shapes formed on only a part of the surface. Components indicated by the same reference numeral in each drawing are considered to be the same component. The drawings are schematic diagrams, and the dimensional ratios shown in the drawings do not necessarily represent the ratios of the actual dimensions.

[0017] In this disclosure, high-pressure low-density polyethylene (hereinafter sometimes referred to as LDPE) is synthesized by radical polymerization under high pressure of 100 MPa to 400 MPa and has a density of 910 kg / m³. 3 More than 930kg / m 3 This refers to polyethylene less than a certain size. LDPE is synthesized by a high-pressure method and has a structure in which repeating ethylene units are randomly branched and linked together. Therefore, compared to linear low-density polyethylene (hereinafter sometimes referred to as L-LDPE), which is a copolymer produced by copolymerizing ethylene with α-olefins such as 1-butene using a metallocene catalyst, LDPE has a lower melting point and superior flexibility.

[0018] [Laminated material for lids] The laminate for lid material of the present disclosure comprises an easily peelable layer and a sealant layer adjacent to the easily peelable layer, wherein the easily peelable layer contains high-pressure low-density polyethylene (A1), a propylene homopolymer (B), and a tackifying resin (C), the sealant layer contains high-pressure low-density polyethylene (A2), the content of high-pressure low-density polyethylene (A2) in the sealant layer is 50% by mass or more with respect to the total mass of the sealant layer, the thickness of the easily peelable layer is 5 μm or more and 12 μm or less, and the sealant layer is the outermost layer on the side of the laminate for lid material that is in contact with the object to be adhered. The laminated lid material of this disclosure is suitably used as a lid material for containers and seals the opening of a container by being bonded to a flange provided at the opening of the container via the sealant layer. The laminated lid material of this disclosure is suitably used as a lid material for various containers, particularly paper cup containers, and has high sealing strength, good peelability, and suppresses stringing when opened.

[0019] The laminate for lids of this disclosure contains high-pressure low-density polyethylene (A1) and (A2) in both the easily peelable layer and the sealant layer adjacent to the easily peelable layer, resulting in good interlayer adhesion. Furthermore, the easily peelable layer contains a propylene homopolymer (B) with low compatibility with high-pressure low-density polyethylene (A1), forming a sea-island structure of the two resins within the easily peelable layer. This achieves a moderately low peel strength due to cohesive failure and suppresses stringing at the peeled surface. In addition, the easily peelable layer further contains a tackifying resin (C), which is compatible with the high-pressure low-density polyethylene (A1), further improving the sealing strength. Combined, these advantages are considered to result in a laminate for lids of this disclosure that has high sealing strength, is easily peelable, and suppresses stringing when opened.

[0020] <Easily peelable layer> The easily peelable layer (hereinafter also simply referred to as the easily peelable layer) in the laminate for lid material of this disclosure comprises high-pressure low-density polyethylene (A1) (LDPE(A1)), propylene homopolymer (B), and tackifying resin (C). The easily peelable layer can be formed by forming an easily peelable layer-forming resin composition containing LDPE (A1), propylene homopolymer (B), and tackifying resin (C), and further containing other components which may be used in combination if desired. The following describes each component contained in the easily peelable layer.

[0021] -High-pressure low-density polyethylene (A1) (LDPE(A1))- The LDPE(A1) used in the easily peelable layer of this disclosure is polyethylene polymerized by a high-pressure radical method using ethylene.

[0022] Polymerization of LDPE can be carried out by known methods. Examples of reactors used for polymerization include autoclave reactors and tubular reactors, and either may be used.

[0023] The LDPE(A1) that may be included in the easily peelable layer in this disclosure has a density of 910 kg / m³, measured in accordance with "Measurement of density and specific gravity of non-foamed plastics" in JIS K7112:1999. 3 More than 930kg / m 3 The following is preferable: 915 kg / m 3 More than 925kg / m 3 It is within the following range. By using LDPE(A1) with a density within the above range in a resin composition for easily peelable layer formation, a resin composition with excellent extrusion processability can be obtained.

[0024] Furthermore, the LDPE(A1) contained in the easily peelable layer is preferably, from the viewpoint of sealing strength, ease of peeling, and suppression of stringing upon opening, has a melt flow rate (hereinafter sometimes referred to as MFR) measured under the conditions of 190°C and 2160g load in accordance with JIS K 7210-1:2014, where MFR is preferably 1.0g / 10 min to 100g / 10 min, more preferably 3.0g / 10 min to 100g / 10 min, even more preferably 5.0g / 10 min to 70g / 10 min, and particularly preferably 20g / 10 min to 60g / 10 min. By using LDPE(A1) with a melt flow rate within the above range in a resin composition for forming an easily peelable layer, the extrusion processability when forming the easily peelable layer is improved.

[0025] The LDPE(A1) content in the easily peelable layer is preferably more than 0% by mass and less than 70% by mass, more preferably 20% by mass or more and 65% by mass or less, and even more preferably 35% by mass or more and 65% by mass or less, based on the total mass of the easily peelable layer. When the LDPE content in the easily removable layer is within the above range, the easily removable layer exhibits better heat resistance and stain resistance to the substrate, and it becomes easier to control the adhesive strength to the substrate within an appropriate range.

[0026] -Propylene homopolymer (PP(B))- The easily peelable layer contains a propylene homopolymer (hereinafter sometimes referred to as PP) (B). PP(B) can be any propylene homopolymer. PP(B) may consist of only one type, or it may consist of two or more types with different molecular weights. For PP(B), a crystallinity of 30% or higher as determined by X-ray is preferred. Of the above PP(B), polymers with a melting peak of 120°C to 170°C based on differential scanning calorimeter (DSC) are preferred from the viewpoint of heat resistance, and polymers with a melting peak of 150°C to 170°C are more preferred.

[0027] The above-mentioned PP(B) can be produced by polymerizing propylene in the presence of a stereoregular olefin polymerization catalyst containing a transition metal compound component such as titanium-based or metallocene-based, an organoaluminum component, and optionally an electron donor, a support, etc.

[0028] The melt flow rate (MFR) of PP(B) measured at a load of 2.16 kg and a temperature of 230°C is preferably 1 g / 10 min to 500 g / 10 min, more preferably 5 g / 10 min to 100 g / 10 min, and even more preferably 7 g / 10 min to 50 g / 10 min from the viewpoints of moldability and impact resistance. The MFR of PP(B) is a value measured under the conditions of a test load of 2.16 kg and a temperature of 230°C in accordance with JIS K 7210-1:2014.

[0029] The density of PP(B) is preferably 870 kg / m 3 ~930 kg / m 3 from the viewpoint of excellent impact resistance and a reduced linear expansion coefficient, more preferably 880 kg / m 3 ~920 kg / m 3 and even more preferably 890 kg / m 3 ~910 kg / m 3 The density of PP(B) is a value measured by the water displacement method in accordance with JIS K 7112:1999.

[0030] The content of PP(B) in the easily peelable layer is preferably more than 0% by mass and less than 40% by mass, more preferably 20% by mass or more and 39% by mass or less, and even more preferably 25% by mass or more and 38% by mass or less based on the total mass of the easily peelable layer.

[0031] It is considered that the easily peelable layer contains PP(B) having low compatibility with the aforementioned LDPE(A1), so that the balance between the sealing strength and the easy peelability (sealing strength) in the easily peelable layer is good. As peeling mechanisms when peeling the lid material from the container, there are three forms: interfacial peeling, interlayer peeling, and cohesive peeling. In the laminate for the lid material in the present disclosure, it is considered that the peeling of the lid body heat-sealed through the easily peelable layer from the container is performed by cohesive failure of the easily peelable layer. Although the mechanism of action in this disclosure is not clear, in the easily peelable layer, LDPE(A1) and PP(B), which has low compatibility with LDPE(A1), are mixed to form a resin composition for forming an easily peelable layer. When the easily peelable layer is formed, a sea-island structure is created in which the mutually incompatible LDPE(A1) forms the sea and PP(B) forms the islands. For the container, high sealing strength is achieved due to the flexible function of LDPE(A1). Furthermore, when the lid material is peeled from the container, cohesive peeling occurs from the interface between the PP(B) and LDPE(A1) that form the islands, resulting in good peelability, and it is thought that stringing during opening is suppressed due to the flexible properties of LDPE(A1).

[0032] From the viewpoint of enabling suitable cohesive failure, the content ratio ((A1):(B)=) of LDPE (A1) and PP (B) contained in the easily peelable layer is preferably 80:20 to 50:50 by mass, and more preferably 75:25 to 55:45 by mass.

[0033] -Tackifying resin (C)- The easily peelable layer contains a tackifying resin (C). The tackifying resin (C) has the function of imparting tackiness to the resin. Therefore, it is possible to easily adjust the adhesive strength of the resin composition for forming an easily peelable layer. The tackifying resin (C) is thought to be compatible with the LDPE (A1) and, by being included in the sea portion of the sea-island structure in the easily peelable layer, has the function of improving sealing strength. The tackifying resin (C) is selected from resins that have the function of imparting tackiness. Examples of tackifying resins (C) include aromatic hydrocarbon resins, alicyclic hydrocarbon resins, aliphatic hydrocarbon resins, terpene resins, rosins, styrene resins, and coumarone-indene resins.

[0034] Examples of aromatic hydrocarbon resins include resins obtained by polymerizing a fraction containing at least one vinyl aromatic hydrocarbon having 8 to 10 carbon atoms, such as vinyltoluene, indene, and α-methylstyrene, and resins obtained by copolymerizing these fractions with aliphatic hydrocarbon fractions. Examples of alicyclic hydrocarbon resins include resins obtained by cyclization-dimerizing and polymerizing the diene component in the spent C4-C5 fraction, resins obtained by polymerizing cyclic monomers such as cyclopentadiene, and resins obtained by intranuclear hydrogenation of aromatic hydrocarbon resins (e.g., hydrogenated petroleum resins). Examples of aliphatic hydrocarbon resins include resins obtained by polymerizing a fraction containing at least one mono- or diolefin having 4 to 5 carbon atoms, such as 1-butene, isobutene, butadiene, 1,3-pentadiene, and isoprene. Examples of terpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, terpene-phenol copolymers, α-pinene-phenol copolymers, and hydrogenated versions thereof. Examples of rosins include gum rosin, wood rosin, tall oil, and other rosins and their modified products. Modified products include those that have been modified by hydrogenation, disproportionation, dimerization, esterification, and other processes. Examples of styrene-based resins include low molecular weight resinous polymers obtained by polymerizing styrene monomers such as styrene, vinyltoluene, α-methylstyrene, and isopropyltoluene.

[0035] The tackifying resin (C) is preferably a resin with a softening point of 85°C to 130°C, more preferably a resin with a softening point of 100°C to 125°C, and even more preferably a resin with a softening point of 110°C to 120°C. Generally, a softening point of 85°C or higher tends to exhibit excellent heat resistance, while a softening point of 130°C or lower tends to exhibit excellent tackiness. The softening point of the tackifying resin (C) can be determined using the value obtained by measuring the softening point according to the softening point test method (ring-ball method) in accordance with JIS K 2207:2006.

[0036] The content of the tackifying resin (C) is preferably more than 0% by mass and less than 25% by mass, relative to the total mass of the resin composition for forming the easily peelable layer. When the content of the tackifying resin (C) exceeds 0% by mass relative to the total mass of the resin composition for forming the easily peelable layer, variations in adhesive strength to the adherend are suppressed. From the viewpoint of uniform adhesive strength, it is more preferable that the content of the tackifying resin (C) be 3% by mass or more, even more preferable that it be 5% by mass or more, and particularly preferable that it be 7% by mass or more, relative to the total mass of the resin composition for forming the easily peelable layer. Furthermore, from the viewpoint of achieving a good balance between adhesion and peelability, the content of the tackifying resin (C) is preferably less than 25% by mass, more preferably 20% by mass or less, even more preferably 18% by mass or less, and particularly preferably less than 16% by mass, based on the total mass of the resin composition for forming the easily peelable layer. Specifically, the content of the tackifying resin (C) is more preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 18% by mass or less, and particularly preferably 7% by mass or more and less than 16% by mass, based on the total mass of the resin composition for forming an easily peelable layer.

[0037] The tackifying resin (C) in the easily peelable layer may be a commercially available product. Examples of commercially available tackifying resins (C) include hydrogenated alicyclic resins such as Alcon (registered trademark: hereinafter the same) P140 (manufactured by Arakawa Chemical Industries, Ltd., softening point 140°C), Alcon P125 (manufactured by Arakawa Chemical Industries, Ltd., softening point 125°C), Alcon P115 (manufactured by Arakawa Chemical Industries, Ltd., softening point 115°C), Alcon P100 (manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C), and Alcon P90 (manufactured by Arakawa Chemical Industries, Ltd., softening point 90°C).

[0038] -Other ingredients- The easily peelable layer, more specifically the resin composition for forming the easily peelable layer, may contain, in addition to the above-mentioned LDPE (A1), PP (B), and tackifying resin (C), other components (also referred to as other components) to the extent that they do not impair the effects of the present invention. Other components are not limited to those mentioned above, but examples include antistatic agents, antiblocking agents, slip agents, antioxidants, heat stabilizers, light stabilizers, pigments, dyes, and the like. Other ingredients may be used individually or in combination of two or more.

[0039] Examples of antistatic agents include conductive polymers, nonionic surfactants, and anionic surfactants. Examples of antiblocking agents include silica and aluminosilicates (such as zeolites). Examples of slip agents include polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and hydrogenated castor oil. When the easily peelable layer contains a slip agent, the slip agent content is preferably less than 1% by mass, and more preferably 0.5% by mass or less, relative to the total mass of the resin composition.

[0040] The content of the above-mentioned other components is preferably less than 2% by mass in total, relative to the total mass of the easily peelable layer. In other words, the total content of LDPE (A1), PP (B), and the tackifying resin (C) in the easily peelable layer is preferably more than 98% by mass and 100% by mass or less, more preferably 99% by mass or more and 100% by mass or less, and even more preferably 99.5% by mass or more and 100% by mass or less, relative to the total mass of the resin components contained in the easily peelable layer.

[0041] From the viewpoint of balancing sealing strength and ease of peeling (peel strength), the thickness of the easily peelable layer is preferably 3 μm or more and less than 20 μm, more preferably 4 μm to 15 μm, and even more preferably 5 μm to 12 μm.

[0042] <Sealant layer> The laminate for lid material of this disclosure has a sealant layer adjacent to an easily peelable layer. The sealant layer is a layer that provides heat-sealing properties to the laminate for lid materials. In the laminate for lid materials, the sealant layer is the outermost layer on the side that comes into contact with the object to be adhered, such as a container. In other words, in the laminate for lid materials, the sealant layer is the layer that comes into direct contact with the object to be adhered, such as a container.

[0043] -High-pressure low-density polyethylene (A2)- The sealant layer contains high-pressure low-density polyethylene (A2) (hereinafter also referred to as LDPE(A2)). The inclusion of LDPE(A2) in the sealant layer provides high sealing strength for the laminated lid material. LDPE(A2), like LDPE(A1) contained in the previously described easily removable layer, is a low-density polyethylene resin obtained by a high-pressure method. Furthermore, the LDPE(A1) contained in the easily peelable layer and the LDPE(A2) contained in the sealant layer may be the same or different from each other.

[0044] The LDPE(A2) contained in the sealant layer has a density of 910 kg / m³ to 930 kg / m³, as measured in accordance with "Measurement of density and specific gravity of non-foamed plastics" in JIS K7112:1999. 3 The following is preferable: 915 kg / m 3 More than 925kg / m 3 It is within the following range. Having a density within the above range improves the adhesion of the sealant layer to the paper container, which is preferable from the viewpoint of the stability of the sealing strength.

[0045] The LDPE(A2) contained in the sealant layer, in terms of suppressing stringing upon opening, preferably has a melt flow rate (hereinafter sometimes referred to as MFR) of 1.0 g / 10 min to 100 g / 10 min, more preferably 3.0 g / 10 min to 50 g / 10 min, even more preferably 3.0 g / 10 min to 40 g / 10 min, and particularly preferably 5.0 g / 10 min to 30 g / 10 min, measured in accordance with JIS K 7210-1:2014 under conditions of 190°C and a 2160 g load.

[0046] The LDPE(A2) content in the sealant layer is 50% by mass or more of the total mass of the sealant layer. A LDPE(A2) content of 50% by mass or more in the sealant layer indicates that LDPE(A2) is the main component of the layer. The LDPE(A2) content in the sealant layer is preferably 50% to 100% by mass, more preferably over 60% to 100% by mass, even more preferably between 70% and 100% by mass, particularly preferably between 90% and 100% by mass, and even more preferably over 95% and 100% by mass, based on the total mass of the sealant layer.

[0047] The LDPE(A2) content in the sealant layer is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, even more preferably 70% by mass to 100% by mass, particularly preferably 90% by mass to 100% by mass, and even more preferably 95% by mass and 100% by mass or less, based on the total amount of resin in the sealant layer.

[0048] -Antiblocking agent- The sealant layer preferably contains an antiblocking agent. The inclusion of an antiblocking agent in the sealant layer reduces blocking in the laminate for the lid material.

[0049] Examples of antiblocking agents include silica, aluminosilicates (such as zeolites), talc, calcium carbonate, and starch. From the viewpoint of efficiently exhibiting an antiblocking effect with small amounts and from the viewpoint of transparency, silica and zeolites are preferred. The sealant layer may contain only one type of antiblocking agent, or it may contain two or more types. When the sealant layer contains an antiblocking agent, the content of the antiblocking agent is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.1% by mass or more and 4.0% by mass or less, and even more preferably 0.1% by mass or more and 3.0% by mass or less, based on the total mass of the sealant layer. By keeping the antiblocking agent content in the sealant layer within the above range, stickiness of the sealant layer is suppressed, blocking is inhibited, and the transparency of the film is maintained at a high level.

[0050] -Other ingredients- The sealant layer may further contain other components in addition to LDPE(A2) and the aforementioned antiblocking agent, which is a preferred co-component, to the extent that it does not impair the effect. Other components include, for example, thermoplastic resins other than LDPE(A2), thermosetting resins, plasticizers, antioxidants, UV absorbers, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, inorganic fillers, organic fillers, impact resistance modifiers, slip agents, crosslinking agents, crosslinking aids, tackifiers, silane coupling agents, processing aids, mold release agents, hydrolysis inhibitors, heat stabilizers, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, dispersants, etc. Other components may be a single type or a combination of two or more types.

[0051] Examples of thermoplastic resins other than LDPE(A2) that may be included in the sealant layer (also referred to as other thermoplastic resins) include polyolefins, ethylene-unsaturated carboxylic acid copolymers or their ionomers, ethylene-vinyl acetate copolymers (EVA), and ethylene-α-olefin copolymer elastomers. Examples of the above α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene. Other thermoplastic resins may be commercially available. Furthermore, the resin contained in the sealant layer may be LDPE(A2) only.

[0052] The thickness of the sealant layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and even more preferably 5 μm to 12 μm.

[0053] <Layer structure of laminated material for lid> The laminate for lid material of this disclosure is not particularly limited in its layer configuration as long as it has the easily peelable layer and sealant layer described above, and may further have any other layers, such as a base layer. The structure of the laminated body for the lid material will be explained with reference to the drawings.

[0054] Figure 1 is a schematic diagram showing one embodiment of the laminate for lid material of the present disclosure. The laminate for lid material 10 shown in Figure 1 has an easily peelable layer 14 and a sealant layer 12 provided adjacent to the easily peelable layer 14. In the laminate for lid material 10 shown in Figure 1, the sealant layer 12 is the outermost surface and is the layer that comes into contact with the object to be adhered, such as a container.

[0055] Figure 2 is a schematic diagram showing another embodiment of the laminate for lid material of the present disclosure. The laminate for lid material 20 shown in Figure 2 further has a base layer 16. That is, an easily peelable layer 14 and a sealant layer 12 are provided on the surface of the base layer 16 in this order. The presence of the base layer 16 further improves the strength and stability of the lid. In the laminate for lid material 20 shown in Figure 2, the sealant layer 12 is the outermost layer and is in contact with the object to be adhered, such as a container.

[0056] -Base material layer- The laminate for lid material of this disclosure may further have at least one base layer. When the laminate for lid material of this disclosure has a base layer, it is preferable that the base layer be provided adjacent to the easily peelable layer on the side opposite to the side of the easily peelable layer that has the sealant layer. The base layer may be provided for the purpose of improving the handling, mechanical properties, heat resistance, etc., of the laminated lid material having an easily peelable layer. The base layer can be a sheet, film, or other plate-like material. Examples of materials for the base layer include paper such as fine paper, medium-quality paper, pure white roll paper, coated paper, single-sided art paper, double-sided art paper, blended paper, synthetic paper, and cardboard; metals such as aluminum foil; polyesters such as polyethylene terephthalate; polyethylenes such as high-pressure low-density polyethylene; polypropylenes such as polypropylene homopolymers and polypropylene copolymers; and resins such as polyamides. Furthermore, depending on the purpose of more effectively suppressing gas permeability, materials combining different materials, such as aluminum-deposited polyester, aluminum-deposited polypropylene, and silica-deposited polyester, may also be used. From the viewpoint of reducing environmental impact, the base layer preferably includes a paper base material. Furthermore, from the viewpoint of processability, it is preferable to include a film or sheet made of polyethylene or polyester.

[0057] In particular, it is preferable that the base layer contains LDPE(A1). Including LDPE(A1) in the base layer improves the adhesive strength between the base layer and the easily peelable layer adjacent to the base layer. The base layer may be a single-layer structure, or a laminated structure of two or more layers, depending on the purpose.

[0058] When a base layer is provided, the thickness of the base layer can be, for example, 5 μm to 100 μm, and preferably 10 μm to 50 μm, from the viewpoint of mechanical strength and workability. To further improve the adhesive strength with the easily removable layer, the surface of the substrate layer that is laminated with the easily removable layer may be subjected to corona treatment, plasma treatment, flame treatment, ozone treatment, or an anchor coat treatment.

[0059] -Other layers- Other optional layers provided in the laminate for lid material of this disclosure, in addition to the base material layer described above, include barrier layers for purposes such as gas barrier properties, water vapor barrier properties, and odor blocking properties; adhesive layers for improving adhesion between different layers; foam layers; inorganic material layers; hard coat layers; anti-reflective layers; anti-fouling layers; anchor coat layers, etc.

[0060] As the barrier layer, metal foils such as aluminum foil, aluminum-deposited polyester, aluminum-deposited polypropylene, silica-deposited polyester, etc. may be used. The thickness of the barrier layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and even more preferably 5 μm to 15 μm.

[0061] From the viewpoint of increasing the adhesive strength with adjacent layers, the surface of the barrier layer on which other resin layers are laminated, or the surface on which an adhesive layer (any layer) is laminated, may be surface-treated. Examples of surface treatments include physical treatments such as corona treatment, plasma treatment, and flame treatment, and chemical treatments such as anchor coating. Among these, it is preferable that the surface of the barrier layer on which the adhesive layer is laminated is corona-treated.

[0062] The adhesive layer is a layer that improves the adhesion between two adjacent layers, for example, the barrier layer and sealant layer described above. If the laminate for lid material of this disclosure has an adhesive layer, the adhesive layer may be one layer or two or more layers. The adhesive layer may include known adhesives. For example, the adhesive layer may include an ionomer of an ethylene-unsaturated carboxylic acid copolymer. The thickness of the adhesive layer is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm, and even more preferably 10 μm to 20 μm.

[0063] Within the scope of achieving the effects of this disclosure, the location of the other layers is not particularly limited. The other layers may be one layer or two or more layers.

[0064] <Preferred physical properties of laminated materials for lids> When used as a lid material for a container, the laminate for lids of the present disclosure preferably has strong sealing strength and easy peelability, i.e., low peel strength. The preferred physical properties of the laminate for lids of the present disclosure regarding sealing strength and peel strength, which is an indicator of easy peelability, are listed below.

[0065] -Sealing strength- The laminated lid material of this disclosure preferably has a sealing strength of 30 kPa or more, more preferably 31 kPa or more, and even more preferably 32 kPa or more, when the laminated lid material is heat-sealed to the surface of a paper container (e.g., a paper cup container) whose surface is coated with polyethylene, at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second. When the sealing strength achieved by the test method described below exceeds 30 kPa, the seal of the container is suitably maintained against, for example, vibration, temperature conditions, and stress during transport, resulting in good protection of the contents.

[0066] The method for testing sealing strength will be explained in more detail. First, a paper cup container (with a flange diameter of 11 cm) coated with polyethylene is placed in a cup holder. A sample of the laminated lid material of this disclosure, cut to a size of 100 mm x 100 mm, is placed on the flange of the paper cup container with the sealant layer facing the center of the opening of the paper cup container and the center of the sample. Next, the sample is heat-sealed under the following heat-sealing conditions to obtain a test sample of the easily peelable layer / sealant layer / paper cup container. After that, the test sample is left for 24 hours in an environment of 23°C and 50% RH. (Heat sealing conditions) • Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by A-Shin Pack Industries Co., Ltd.) • Sealing temperature: 160℃ • Sealing time: 1.0 seconds • Seal pressure (gauge pressure): 0.1 MPa

[0067] Next, a constant amount of air is introduced into the test sample under the following conditions until the laminate for the lid material peels off, and the maximum pressure at which the laminate for the lid material peels off is measured. The average of the maximum pressures measured three times is taken as the sealing strength (kPa). (Air supply conditions) • Testing equipment: Bursting strength tester manufactured by Sun Science Co., Ltd. ·Flow rate: 0.8L / min ·Temperature: 23℃ ·Humidity: 50%RH

[0068] -Peel strength- The laminate for lid material of the present disclosure preferably has a peel strength of 5N or more and 20N or less when peeling the laminate for lid material from a paper container (e.g., a paper cup container) whose surface is coated with polyethylene, when the laminate for lid material is heat-sealed to the surface of the paper cup container at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, and is more preferably 5N or more and 15N or less. A peel strength of 5N or higher, as determined by the following test method, prevents the container lid from easily opening due to vibration or stress during transport, thus reducing the protection of the contents. Furthermore, a peel strength of 20N or lower allows for easy opening of the lid and suppresses the occurrence of stringing at the peeled area.

[0069] The test method for peel strength will be explained in more detail. First, a paper cup container (with a flange diameter of 11 cm) coated with polyethylene is placed in a cup holder. A sample of the laminated lid material of this disclosure, cut to a size of 100 mm x 100 mm, is placed on the flange of the paper cup container with the sealant layer facing the center of the opening of the paper cup container and the center of the sample. Next, the sample is heat-sealed under the following heat-sealing conditions to obtain a test sample of the easily peelable layer / sealant layer / paper cup container. After that, the test sample is left for 24 hours in an environment of 23°C and 50% RH. (Heat sealing conditions) • Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by A-Shin Pack Industries Co., Ltd.) • Sealing temperature: 160℃ • Sealing time: 1.0 seconds • Seal pressure (gauge pressure): 0.1 MPa

[0070] Next, the laminated lid material is peeled from the corner of the test sample under the following peeling conditions, and the maximum peel strength is measured. The average of the maximum peel strengths measured three times is defined as the peel strength (N). (Peeling conditions) • Peeling test equipment: Peeling test machine manufactured by Imada Corporation. • Test speed: 500 mm / min • Peeling angle: 45° ·Temperature: 23℃ ·Humidity: 50%RH

[0071] [Lid material] The lid material of this disclosure includes the laminate for lid material of this disclosure as described above. The lid material of this disclosure includes the laminate for lid material of this disclosure described above, and is used as a lid material for a packaging container. The lid material of this disclosure may use the laminate for lid material of this disclosure described herein as is, or it may be composed of a support and the laminate for lid material of this disclosure described herein, or it may further have other layers. Examples of lid material structures include laminated structures such as a base material / easily peelable layer / sealant layer, and configurations having different types of resin films as base materials, such as a laminated structure of stretched polyester film / polyethylene film / laminate layer / easily peelable layer / sealant layer, or a laminated structure of paper base material layer / laminate layer / easily peelable layer / adhesive layer / sealant layer. In the above layer configurations, the "stretched polyester film / polyethylene film" functions as the resin base material layer of the lid. Furthermore, if the laminate for lid material of this disclosure includes a base material layer, it may or may not have a separate support. Furthermore, to improve water vapor barrier properties and odor blocking properties, the lid material may have an additional barrier layer.

[0072] When manufacturing the laminate for lid material according to this disclosure, and furthermore, a lid material including the laminate for lid material, known methods for manufacturing laminates can be appropriately applied, such as a method of applying a coating liquid for forming each layer constituting the laminate to a support or substrate layer in multiple layers, or a method of forming a film of molten resin for forming each layer constituting the laminate by co-extrusion. In particular, from the viewpoint of ease of manufacturing, a method of forming a laminate by co-extrusion onto a support or substrate layer is preferred. Suitable applications of the lid material include lids that are adhered to storage containers to seal their openings.

[0073] [Packaging container] The packaging container of the present disclosure comprises a lid material of the present disclosure as described above, and a container having one end of a cylindrical body closed and the other end having an opening, wherein the opening is covered by the lid material by heat sealing the opening, for example, the surface of the periphery of the opening, via a sealant layer. In packaging containers, the container to which the lid material is attached, which is a cylindrical body with one end closed and the other end open, may hereafter be referred to as the "bottom material."

[0074] There are no particular restrictions on the bottom material of the packaging container described herein; any bottom material can be used as long as the surface in contact with the sealant layer of the lid material is heat-sealable. A container having a bottom material with an opening and a storage compartment, applicable to the packaging container of this disclosure, is preferably a container in which at least the outermost surface, i.e., the outermost surface that contacts the sealant layer of the lid material, is molded from a resin material. In particular, from the viewpoint of reducing environmental impact, it is preferable that the bottom material is a paper container (e.g., a paper cup container) in which the surface that contacts the lid material is coated with polyethylene. The packaging container described herein has a suitable peel strength and good peelability when the heat-sealed lid is removed, and the occurrence of stringing during peeling is suppressed. Furthermore, it has stable sealing strength when sealed, suppresses unwanted peeling during storage or transportation, and provides excellent protection of the contents.

[0075] <Paper containers> This disclosure describes a paper container, which is a suitable base material for the packaging container of this disclosure. A paper container is a paper container in which the surface of a paper base material, which is heat-sealed via a sealant layer of a lid material, is coated with polyethylene. A paper container may also be a paper cup container in which a paper base material with a polyethylene-coated surface is molded into a cup shape. The paper substrate for molding paper cup containers is not particularly limited as long as it allows for the molding of the paper cup container. The paper cup container may have other layers on the side of the paper substrate opposite to the side coated with polyethylene, other than the polyethylene-coated paper substrate. Other layers include, for example, a polyethylene layer, a paper substrate, a base layer, an adhesive layer, and an anti-fouling layer. The other layers may consist of one layer or two or more layers.

[0076] The polyethylene coated on the heat-sealed surface of the paper cup container is not particularly limited as long as it is an ethylene polymer mainly containing ethylene-derived structural units. The ethylene polymer is preferably an ethylene homopolymer or an ethylene copolymer containing 50% by mass or more of ethylene-derived structural units relative to the total polymer, and more preferably an ethylene homopolymer. The heat-sealed surface of the paper cup container may be coated with components other than polyethylene.

[0077] The paper cup container may have a flange portion that is heat-sealed via a sealant layer of the lid material. If a flange portion is present, it is preferable that the surface of the flange portion is also coated with polyethylene.

[0078] The packaging container can be suitably used as a packaging container for, for example, food, beverages, liquids other than beverages, pharmaceuticals, industrial products, daily necessities, cosmetics, etc., and is particularly suitably used as a packaging container for food and pharmaceuticals. The paper cup container may contain food, beverages, liquids other than beverages, pharmaceuticals, industrial products, daily necessities, cosmetics, etc., or it may contain food, beverages, or pharmaceuticals.

[0079] An example of the packaging container described herein will be explained below with reference to the drawings.

[0080] Figure 3 is a schematic diagram showing an example of a packaging container using a laminated lid material 20, which includes the base material layer 16 shown in Figure 2, as the laminated lid material. The packaging container 30 shown in Figure 3 uses the laminated lid material 20 described in Figure 2 as the lid material 20. The packaging container 30 comprises a paper cup container 18 and a lid material 20, and the contents such as food can be stored in the void corresponding to the storage area of ​​the paper cup container 18. The paper cup container 18 has a polyethylene layer formed by coating the surface of a paper base material with polyethylene. The paper cup container 18 has a flange portion at the opening. The opening is covered by the lid material 20 by heat sealing the sealant layer 12 of the lid material 20 to the polyethylene layer on the surface of the flange portion. When peeling the lid material 20 from the packaging container 30, stringing is suppressed, which prevents foreign matter such as resin from being mixed into the contents, and prevents a decrease in tactile sensation when eating the contents by putting the mouth to the flange portion. [Examples]

[0081] The following describes in more detail, with specific examples, packaging containers using the laminated lid material of this disclosure, based on the examples provided below. However, the following examples are merely examples of the lid material and packaging container of this disclosure, and it goes without saying that this disclosure includes various modifications.

[0082] The following materials were used in the examples and comparative examples shown below. <High-pressure low-density polyethylene (A2) (LDPE(A2))> • HP-LDPE1 (manufactured by Mitsui Dow Polychemicals, MFR (190℃, 2160g load): 23g / 10min, density: 918kg / m³) 3 (Melting point: 106℃) • HP-LDPE2 (manufactured by Mitsui Dow Polychemicals, MFR (190℃, 2160g load): 7.2g / 10min, density: 918kg / m³) 3 (Melting point: 108℃) • HP-LDPE3 (manufactured by Mitsui Dow Polychemicals, MFR (190℃, 2160g load) 4.5g / 10min, density 923kg / m³) 3 (Melting point: 111℃) • HP-LDPE4 (manufactured by Mitsui Dow Polychemicals, MFR (190℃, 2160g load): 70g / 10min, density: 916kg / m³) 3 (Melting point: 104℃)

[0083] <Propylene alone polymer (B) (PP(B))> • Homo PP1 (manufactured by Prime Polymer, Prime Polypropylene (registered trademark) F113G, MFR (230℃, 2160g load): 3.0g / 10min, Density: 910kg / m³) 3 )

[0084] <Tackifying resin (C)> • Tackifying resin 1: Alicyclic hydrocarbon resin (manufactured by Arakawa Chemical Industries, Ltd., Alcon® P115)

[0085] <Other resins> • Linear low-density polyethylene (L-LDPE, manufactured by Prime Polymer, Evolu® SP2540), MFR (190℃, 2160g load): 3.8g / 10min, Density: 924kg / m³ 3 (Melting point: 120℃)

[0086] <Additives> • Antiblocking agent: Aluminum silicate (manufactured by Mizusawa Chemical Co., Ltd., Silton® JC-50) • Release agent: Erucic acid amide (ELA, manufactured by NOF Corporation) • Slip agent: Polyethylene glycol (PEG, manufactured by Nippon Seika Co., Ltd.)

[0087] [Examples 1-6 and Comparative Example 1] <Preparation of resin composition for sealant layer formation> A resin composition (P) for forming a sealant layer was prepared by pre-mixing the materials in the proportions shown in Table 1 (the units of materials in Table 1 represent parts by mass) to a total volume of 10 kg, and then dry-blending the mixture.

[0088] <Preparation of resin compositions for easily peelable layer formation> A resin composition for easily peelable layer formation (hereinafter also referred to as EZP) was prepared by pre-mixing the materials in the following proportions: 17 parts by mass of HP-LDPE1 (LDPE(A1)), 33 parts by mass of HP-LDPE4 (LDPE(A1)), 34.8 parts by mass of PP(B), 15 parts by mass of tackifying resin (C), 0.1 parts by mass of release agent, and 0.1 parts by mass of slip agent, with a total weight of 10 kg. The mixture was then fed into a single-screw extruder with a screw diameter of 65 mmφ (effective screw length: L / D=28) and melt-kneaded at a processing temperature of 240°C. In EZP, the total content of LDPE(A1), PP(B), and tackifying resin(C) was 99.8% by mass, and the ratio of PP(B) to LDPE(A1) was 1:0.696.

[0089] <Fabrication of laminates> A molten film consisting of a laminate layer, an easily removable layer, and a sealant layer was fabricated using a multilayer cast film molding machine. The previously described HP-LDPE1 was used to form the laminate layer. The resin composition for forming the easily peelable layer (EZP) described above was used to form the easily peelable layer, and the resin composition for forming the sealant layer (P) described above was used to form the sealant layer, with a processing temperature of 220°C, and the thickness configuration of each layer was set to laminate layer / easily peelable layer / sealant layer = 15 μm / 7 μm / 7 μm. A base layer, which was prepared by laminating a 12 μm stretched polyester film (Toray Industries, Ltd., Lumirror®) with a 15 μm low-density polyethylene (Mitsui Dow Polychemicals, Mirason® 11P) layer onto the laminate layer side of the molten film, was laminated by extrusion lamination so as to be bonded to the low-density polyethylene side of the base layer, thereby producing a laminate for lid material. The layer structure and thickness of the laminate for the lid material are as follows: stretched polyester film (base layer) / polyethylene (base layer) / laminate layer / easily removable layer / sealant layer = 12 μm / 15 μm / 15 μm / 7 μm / 7 μm. The multilayer cast film molding machines used above are three-layer, three-type multilayer cast molding machines manufactured by Tanabe Plastics Machinery Co., Ltd., and all molding machines are single-screw extruders with a screw diameter of 40 mmφ and a die width of 500 mm. The co-extrusion feed block is manufactured by EDI.

[0090] [Evaluation of sealing strength] A paper cup container with a polyethylene-coated surface (polyethylene-coated cup, flange diameter 11 cm) was set in a cup holder, and a sample of laminate material for the lid, cut to a size of 100 mm x 100 mm, was placed on the flange of the paper cup container with the sealant layer side facing the center of the opening of the paper cup container and the center of the sample. Next, it was heat-sealed under the following heat-sealing conditions to obtain a test sample having a layer structure of stretched polyester film / polyethylene / laminate layer / easily peelable layer / sealant layer / polyethylene-coated cup. After that, it was left for 24 hours in an environment of 23°C and 50% RH. <Heat sealing conditions> • Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by A-Shin Pack Industries Co., Ltd.) • Sealing temperature: 160℃ • Sealing time: 1.0 seconds • Seal pressure (gauge pressure): 0.1 MPa

[0091] Next, a constant amount of air was introduced into the test sample prepared above under the following conditions until the laminate peeled off, and the maximum pressure at which the laminate peeled off was measured. The average of the maximum pressures measured three times was taken as the sealing strength (kPa). <Air supply conditions> • Testing equipment: Bursting strength tester manufactured by Sun Science Co., Ltd. ·Flow rate: 0.8L / min ·Temperature: 23℃ ·Humidity: 50%RH

[0092] The sealing strength was evaluated according to the following criteria. <Evaluation Criteria> A: The maximum pressure at which the laminate delaminates exceeded 30kPa. B: The maximum pressure at which the laminate delaminated was 30 kPa or less.

[0093] [Evaluation of peel strength (cup seal strength)] A paper cup container with a polyethylene-coated surface (polyethylene-coated cup, flange diameter 11 cm) was set in a cup holder, and a lid material sample cut from a laminate for lid material to a size of 100 mm x 100 mm was placed on the flange of the paper cup container so that the center of the opening of the paper cup container and the center of the sample faced each other. Next, it was heat-sealed under the following heat-sealing conditions to obtain a test sample having a layer structure of stretched polyester film / polyethylene / laminate layer / easily peelable layer / sealant layer / polyethylene-coated cup. After that, it was left for 24 hours in an environment of 23°C and 50% RH. <Heat sealing conditions> • Sealing device: Cup sealer (PACH SEALER Model 0L, manufactured by A-Shin Pack Industries Co., Ltd.) • Sealing temperature: 160℃ • Sealing time: 1.0 seconds • Seal pressure (gauge pressure): 0.1 MPa

[0094] Next, the laminated lid material was peeled from the polyethylene-coated cup at the corner of the test sample prepared above under the following peeling conditions, and the maximum peel strength was measured. The average of the maximum peel strengths measured three times was defined as the peel strength (N). <Peel Conditions> • Peeling test equipment: Peeling test machine manufactured by Imada Corporation. • Test speed: 500 mm / min • Peeling angle: 45° ·Temperature: 23℃ ·Humidity: 50%RH

[0095] The peel strength was evaluated according to the following criteria. <Evaluation Criteria> A: The peel strength was between 5N and 15N. B: Peel strength is less than 5N or greater than 15N

[0096] [Evaluation of the delamination state] A skilled technician observed the sealant layer side surface of the laminate (a sample from which the sealant layer and polyethylene coated cup had been separated) after the peel strength measurement used in the above peel strength measurement. In some cases, thin, thread-like resin may form in the delamination area. This is commonly known as the "stringing phenomenon." The presence or absence of stringing was recorded visually. The stringing phenomenon is undesirable not only because it degrades the appearance, but also because it can lead to foreign matter contamination, such as string fragments adhering to the contents when removing food or other items. The peeling condition was evaluated according to the following criteria. Ratings AA to B represent a level that poses no practical problems, and ratings AA and A are preferred levels. <Evaluation Criteria> AA: No string pulling was observed at all. A: Almost no string pulling was observed. B: Slight string pulling was observed. C: Thread-pulling was observed occasionally.

[0097] [Table 1]

[0098] As is clear from Table 1, compared to Comparative Example 1, Examples 1 to 5 showed higher sealing strength and lower peel strength. Furthermore, stringing after peeling was suppressed, and the peeling state in all cases was at a level that posed no practical problems. From the above, it was confirmed that, according to this embodiment, when the resulting laminated lid material is used as a lid material for a packaging container, it achieves both high sealing strength and low peel strength, i.e., both sealing strength and easy peelability, and also suppresses the occurrence of stringing when opened.

[0099] [Explanation of symbols] 10 Laminate for lid material 12. Sealant layer 14. Easily Peelable Layer 16 Base material layer 18 paper cup containers 20 Laminated material for lid (lid material) 30 Packaging containers

[0100] The disclosure of Japanese Patent Application No. 2022-186014, filed on 21 November 2022, is incorporated into this disclosure by reference. All documents, patent applications, and technical specifications described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical specification were specifically and individually noted to be incorporated by reference.

Claims

1. An easily peelable layer, The easily peelable layer comprises a sealant layer adjacent to the aforementioned peelable layer, The easily peelable layer comprises high-pressure low-density polyethylene (A1), propylene homopolymer (B), and tackifying resin (C). The sealant layer comprises high-pressure low-density polyethylene (A2), The content of the high-pressure low-density polyethylene (A2) in the sealant layer is 50% by mass or more of the total mass of the sealant layer. The thickness of the easily peelable layer is 5 μm or more and 12 μm or less. Furthermore, the sealant layer is the outermost layer on the side of the laminate for lid material that is in contact with the object to be adhered.

2. The laminate for lid material according to claim 1, wherein the high-pressure low-density polyethylene (A1) contained in the easily peelable layer has a melt flow rate of 3.0 g / 10 min or more and 100 g / 10 min or less, as measured under conditions of 190°C and a 2160 g load, in accordance with JIS K 7210-1:2014.

3. The laminate for lid material according to claim 1, wherein the high-pressure low-density polyethylene (A2) contained in the sealant layer conforms to JIS K 7210-1:2014 and has a melt flow rate of 3.0 g / 10 min or more and 50 g / 10 min or less, as measured under conditions of 190°C and a 2160 g load.

4. The laminate for lid material according to claim 1, wherein the content of the propylene homopolymer (B) in the easily peelable layer is greater than 0% by mass and less than 40% by mass with respect to the total mass of the easily peelable layer.

5. The laminate for lid material according to claim 1, wherein the content ratio ((A1):(B)=) of the high-pressure low-density polyethylene (A1) and the propylene homopolymer (B) contained in the easily peelable layer is 80:20 to 50:50 on a mass basis.

6. The laminate for lid material according to claim 1, wherein the content of the high-pressure low-density polyethylene (A1) in the easily peelable layer is greater than 0% by mass and less than 70% by mass with respect to the total mass of the easily peelable layer.

7. The laminate for lid material according to claim 1, wherein the total content of the high-pressure low-density polyethylene (A1), the propylene homopolymer (B), and the tackifying resin (C) in the easily peelable layer is greater than 98% by mass and less than or equal to 100% by mass of the total mass of the resin components contained in the easily peelable layer.

8. The laminate for lid material according to claim 1, wherein the sealant layer further comprises an antiblocking agent.

9. The laminate for lid material according to claim 8, wherein the content of the antiblocking agent is 0.1% by mass or more and 5.0% by mass or less with respect to the total mass of the sealant layer.

10. The laminate for lid material according to claim 1, having at least one base material layer adjacent to the easily peelable layer on the side opposite to the side of the easily peelable layer that has the sealant layer.

11. The laminate for lid material according to claim 10, wherein the base material layer comprises high-pressure low-density polyethylene (A1).

12. The laminate for lid material according to claim 1, wherein when the laminate for lid material is heat-sealed to the surface of a paper container whose surface is coated with polyethylene at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, the sealing strength of the laminate for lid material to the paper container exceeds 30 kPa.

13. The laminate for lid material according to claim 1, wherein when the laminate for lid material is heat-sealed to the surface of a paper container whose surface is coated with polyethylene at a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, the peel strength when peeling the laminate for lid material from the paper container is 5 N or more and 20 N or less.

14. A lid material comprising a laminate for lid material as described in any one of claims 1 to 13.

15. The lid material according to claim 14, A container comprising a cylindrical body with one end closed and the other end having an opening, A packaging container in which the opening is covered by the lid material by heat-sealing the lid material to the opening via a sealant layer.

16. The packaging container according to claim 15, wherein the container is a paper container in which the surface of the paper substrate on the side in contact with the lid material is coated with polyethylene.

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