Laminate for cover material and packaging container

Abstract

The present invention provides a laminate for a lid material, a lid material using the laminate for a lid material, and a packaging container using a lid material, the laminate for a lid material comprising an easily peelable layer and a sealant layer adjacent to the easily peelable layer, the easily peelable layer comprising a high pressure process low density polyethylene (A1), a propylene homopolymer (B), and an adhesion 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 mass% or more with respect to the total mass of the sealant layer, and the sealant layer is the outermost layer on the side of the laminate for lid material that is in contact with the adherend.

Description

Technical Field

[0001] The present disclosure relates to a laminate for a lid material and a packaging container. Background Art

[0002] As raw materials for containers such as foods and pharmaceuticals, paper containers (hereinafter also referred to as paper cups) obtained by coating the surface of a paper substrate with polyethylene, impact-resistant polystyrene sheets, expanded polystyrene sheets, or products obtained by laminating an impact-resistant polystyrene film thereon are widely used.

[0003] Generally, a container and a lid material are sealed by heat-sealing using a resin composition for a sealant to protect the contents. Among packaging containers, paper cups having a polyethylene-coated surface are excellent from the viewpoint of reducing the environmental load due to the reduction in the use of plastics, and also have excellent heat insulation, heat retention, designability, etc., and are used in a wide range of applications such as cup noodle containers, dessert containers, and beverage containers.

[0004] Regarding the lid material of a packaging container, high sealing properties are required to protect the contents, and easy-openability is required at the time of opening.

[0005] For example, in Japanese Unexamined Patent Application Publication No. 2010-94860, a co-extruded multilayer film suitable as a lid material for a packaging container is disclosed as a multilayer film having a sealant layer mainly composed of a polyethylene-based resin and a support layer containing a propylene-based resin having a melting point of 155°C or higher and a polyethylene-based resin, in view of transparency, openability, and sealing properties.

[0006] In addition, Japanese Unexamined Patent Application Publication No. 2004-195955 discloses a sealant film having a base material layer containing a polyolefin resin and a tackifier, and a sealant layer formed of a polyolefin resin composition.

[0007] In Japanese Unexamined Patent Application Publication No. 2013-111811, an easily peelable film is disclosed, which is a two-layer film of an adhesive layer (formed of a mixture of high-density polyethylene and low-density polyethylene) and a support layer (formed of a mixed resin composition of high-density polyethylene, low-density polyethylene, and polypropylene homopolymer and foamed). Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Regarding a lid material that exhibits easy-openability with respect to a paper cup in which the surface of a paper container is coated with polyethylene, the required technical level is getting higher and higher.

[0010] Specifically, high sealing strength is required so that the lid does not open during transportation, storage, etc., and the contents do not leak, and easy peelability is required so that the lid can be easily opened during use.

[0011] In addition, when peeling off the cover material from the paper cup with the polyethylene coating on the surface, stringing may occur. Stringing refers to the phenomenon that thin thread-like resin is formed at the peeled portion. If stringing occurs, there are problems such as poor appearance, foreign matter is mixed into the food due to the string when taking out the contents as food, and the touch of the edge of the cup is reduced, which significantly damages the impression of the packaging container.

[0012] The laminated film described in Japanese Patent Application Publication No. 2010-94860 is considered to have good transparency and good impermeability to inert gas, and the film described in Japanese Patent Application Publication No. 2013-111811 is considered to have good peelability, but neither document contains a viewpoint related to suppressing stringing when the lid is opened.

[0013] The sealant film described in Japanese Patent Application Laid-Open No. 2004-195955 aims to improve tearability and suppress stringing, but there is still room for improvement.

[0014] An embodiment of the present invention aims to provide a lid material laminate and a lid material including the lid material laminate. When the lid material laminate is used as a lid material for a container, the lid material laminate has high sealing strength, good peelability, and suppresses stringing during opening.

[0015] Another embodiment of the present invention aims to provide a packaging container using the above-mentioned cover material laminate as a cover material, which has high sealing strength, good peelability, and suppresses stringing when opening.

[0016] Means for solving problems

[0017] Specific means for solving the above-mentioned problems include the following aspects.

[0018] <1> A laminate for a covering material, comprising an easily peelable layer and a sealant layer adjacent to the easily peelable layer, wherein the easily peelable layer comprises a high-pressure process low-density polyethylene (A1), a propylene homopolymer (B), and a tackifier resin (C), and the sealant layer comprises a high-pressure process low-density polyethylene (A2), the content of the high-pressure process low-density polyethylene (A2) in the sealant layer is 50% by mass or more relative to the total mass of the sealant layer, the thickness of the easily peelable layer is 5 μm to 12 μm, and the sealant layer is the outermost layer of the side of the laminate for a covering material in contact with an adherend.

[0019] <2> The laminate for a lid material as described in <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 to 100 g / 10 min as measured at 190°C and a load of 2160 g in accordance with JIS K 7210-1:2014.

[0020] <3>The laminate for a lid material as described in <1> or <2>, wherein the high-pressure low-density polyethylene (A2) contained in the sealant layer has a melt flow rate of 3.0 g / 10 minutes or more and 50 g / 10 minutes or less as measured according to JIS K 7210-1:2014 under the conditions of 190 °C and a load of 2160 g.

[0021] <4>The laminate for a lid material as described in any one of <1> to <3>, wherein the content of the propylene homopolymer (B) in the peelable layer is more than 0% by mass and less than 40% by mass with respect to the total mass of the peelable layer.

[0022] <5>The laminate for a lid material as described in any one of <1> to <4>, wherein the content ratio of the high-pressure low-density polyethylene (A1) to the propylene homopolymer (B) ((A1):(B)=) contained in the peelable layer is 80:20 to 50:50 in terms of mass conversion.

[0023] <6>The laminate for a lid material as described in any one of <1> to <5>, wherein the content of the high-pressure low-density polyethylene (A1) in the peelable layer is more than 0% by mass and less than 70% by mass with respect to the total mass of the peelable layer.

[0024] <7>The laminate for a lid material as described in any one of <1> to <6>, wherein the total content of the high-pressure low-density polyethylene (A1), the propylene homopolymer (B), and the tackifying resin (C) in the peelable layer is more than 98% by mass and 100% by mass or less with respect to the total mass of the resin components contained in the peelable layer.

[0025] <8>The laminate for a lid material as described in any one of <1> to <7>, wherein the sealant layer further contains an anti-blocking agent.

[0026] <9>The laminate for a lid material as described in <8>, wherein the content of the anti-blocking 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.

[0027] <10>The laminate for a lid material as described in any one of <1> to <9>, wherein at least one substrate layer is provided adjacent to the peelable layer on the side opposite to the side having the sealant layer of the peelable layer.

[0028] <11>The laminate for a lid material as described in <10>, wherein the substrate layer contains high-pressure low-density polyethylene (A1).

[0029] <12>The laminate for a lid material according to any one of <1> to <11>, wherein when the laminate for a lid material is heat-sealed to the surface of a paper container whose surface is coated with polyethylene under the conditions of a gauge pressure of 0.1 MPa, a heating temperature of 160°C, and a sealing time of 1.0 second, the sealing strength between the laminate for a lid material and the paper container is greater than 30 kPa.

[0030] <13>The laminate for a lid material according to any one of <1> to <12>, wherein when the laminate for a lid material is heat-sealed to the surface of a paper container whose surface is coated with polyethylene under the conditions of 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 the laminate for a lid material is peeled from the paper container is 5 N or more and 20 N or less.

[0031] <14>A lid material comprising the laminate for a lid material according to any one of <1> to <13>.

[0032] <15>A packaging container comprising: the lid material according to <14>; and a container in which one side of a cylindrical body is closed and an opening is provided on the other side.

[0033] The opening is sealed with the lid material by heat-sealing the lid material through a sealant layer at the opening.

[0034] <16>The packaging container according to <15>, wherein the container is a paper container whose surface of a paper base material on the side in contact with the lid material is coated with polyethylene.

[0035] Effects of the Invention

[0036] According to one embodiment of the present invention, it is possible to provide a laminate for a lid material and a lid material including the laminate for a lid material, which have high sealing strength, good peelability, and suppress wire drawing during opening when used as a lid material for a container.

[0037] According to another embodiment of the present invention, it is possible to provide a packaging container that uses the above lid material, has high sealing strength, good peelability, and suppresses wire drawing during opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic configuration diagram showing an example of the laminate for a lid material of the present disclosure text.

[0039] Figure 2 is a schematic configuration diagram showing another example of the laminate for a lid material of the present disclosure text.

[0040] Figure 3 is a schematic configuration diagram showing an example of a packaging container including the lid material of the present disclosure text. DETAILED DESCRIPTION OF THE INVENTION​​​

[0041] Hereinafter, the embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0042] In this disclosure, a numerical range indicated by "~" represents a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.

[0043] In the numerical ranges described stepwise in this disclosure, the upper limit value or the lower limit value described in one numerical range can be replaced with the upper limit value or the lower limit value of other stepwise described numerical ranges. Additionally, in the numerical ranges described in this disclosure, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the examples.

[0044] In this disclosure, each component may contain a plurality of corresponding substances. In the case where there are a plurality of substances corresponding to each component, unless otherwise specified, the content rate or content of each component refers to the total content rate or content of the plurality of substances.

[0045] In this disclosure, the so-called "layer" and "film", when viewed from a top view, in addition to the configuration of the shape formed over the entire surface, also include the configuration of the shape formed on a part.

[0046] In each of the drawings, the constituent elements denoted by the same reference numeral represent the same constituent elements.

[0047] The drawings are schematic diagrams, and the ratio of the dimensions in the drawings does not necessarily represent the actual dimensional ratio.

[0048] In this disclosure, high-pressure low-density polyethylene (hereinafter sometimes referred to as LDPE) refers to polyethylene having a density of 910 kg / m 3 or more and less than 930 kg / m 3 synthesized by radical polymerization under a high pressure of 100 Mpa to 400 MPa.

[0049] LDPE is synthesized by the high-pressure method and has a structure in which the repeating unit ethylene is randomly bonded in a branched form. Therefore, compared with linear low-density polyethylene (hereinafter sometimes referred to as L-LDPE), which is a copolymer usually synthesized using a metallocene catalyst and copolymerizing an α-olefin such as 1-butene with ethylene, it has the characteristics of a lower melting point and more excellent flexibility.

[0050] [Laminated body for lid material]

[0051] The laminate for a lid material of the present disclosure includes a peelable layer and a sealant layer adjacent to the peelable layer. The peelable layer contains a high-pressure low-density polyethylene (A1), a propylene homopolymer (B), and a tackifying resin (C). The sealant layer contains a 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 based on the total mass of the sealant layer. The thickness of the 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 a lid material that contacts the adherend.

[0052] The laminate for a lid material of the present disclosure is suitable for use as a lid material for a container. By bonding through the sealant layer to a flange provided at an opening of the container, the opening of the container is sealed. The laminate for a lid material of the present disclosure is suitable for use as a lid material for various containers, particularly paper cup containers, has a high sealing strength, good peelability, and suppresses stringing during opening.

[0053] Regarding the laminate for a lid material of the present disclosure, high-pressure low-density polyethylenes (A1) and (A2) are included in any layer of the peelable layer and the sealant layer adjacent to the peelable layer, so the interlayer adhesion is good. In addition, since the peelable layer contains a propylene homopolymer (B) that has low compatibility with the high-pressure low-density polyethylene (A1), a sea-island structure composed of two resins is formed in the peelable layer, achieving a moderate reduction in the peel strength due to cohesive failure and suppressing the occurrence of stringing at the peeling surface. Further, since the peelable layer also contains a tackifying resin (C), the tackifying resin (C) is compatible with the high-pressure low-density polyethylene (A1), and the sealing strength is further improved. It is considered that these advantages complement each other, and the laminate for a lid material of the present disclosure has a high sealing strength, is peelable, and suppresses stringing during opening.

[0054] <Peelable layer>

[0055] The peelable layer (hereinafter, also simply referred to as the peelable layer) in the laminate for a lid material of the present disclosure contains a high-pressure low-density polyethylene (A1) (LDPE(A1)), a propylene homopolymer (B), and a tackifying resin (C).

[0056] The peelable layer can be formed by film-forming a resin composition for forming a peelable layer that contains LDPE(A1), a propylene homopolymer (B), a tackifying resin (C), and other components used as desired.

[0057] Hereinafter, each component contained in the peelable layer will be described.

[0058] - High-pressure low-density polyethylene (A1) (LDPE(A1)) -

[0059] The LDPE (A1) used in the peelable layer of the present disclosure is polyethylene obtained by polymerizing ethylene using the high-pressure free radical method.

[0060] The polymerization of LDPE can be carried out by known methods. As the reactor used in the polymerization, for example, an autoclave type reactor and a tubular reactor can be cited, and any reactor can be used.

[0061] The density of the LDPE (A1) that can be contained in the peelable layer in the present disclosure, measured according to "Determination of Density and Specific Gravity of Non-Foamed Plastics" in JIS K7112:1999, is 910 kg / m 3 to 930 kg / m 3 Hereinafter, it is preferably in the range of 915 kg / m 3 to 925 kg / m 3 or less.

[0062] By using LDPE (A1) with a density in the above range in the resin composition for forming the peelable layer, a resin composition with excellent extrusion processability is obtained.

[0063] In addition, from the viewpoints of sealing strength, peelability, and suppression of wire drawing during opening, the melt flow rate (hereinafter sometimes referred to as MFR) of the LDPE (A1) contained in the peelable layer, measured according to JIS K 7210-1:2014 under the conditions of 190 °C and a load of 2160 g, is preferably 1.0 g / 10 minutes or more and 100 g / 10 minutes or less, more preferably 3.0 g / 10 minutes or more and 100 g / 10 minutes or less, further preferably 5.0 g / 10 minutes or more and 70 g / 10 minutes or less, and particularly preferably 20 g / 10 minutes or more and 60 g / 10 minutes or less.

[0064] By using LDPE (A1) with a melt flow rate in the above range in the resin composition for forming the peelable layer, the extrusion processability during the formation of the peelable layer becomes better.

[0065] Relative to the total mass of the peelable layer, the content of LDPE (A1) in the peelable layer is preferably greater than 0% by mass and less than 70% by mass, more preferably 20% by mass or more and 65% by mass or less, and further preferably 35% by mass or more and 65% by mass or less.

[0066] When the content of LDPE in the peelable layer is in the above range, the heat resistance of the peelable layer and the stain resistance to the adherend become better, and it is easy to control the adhesion strength to the adherend within an appropriate range.

[0067] - Polypropylene homopolymer (PP (B)) -

[0068] The peelable layer contains a propylene homopolymer (hereinafter sometimes referred to as PP) (B).

[0069] As the PP (B), any propylene homopolymer may be used. The PP (B) may contain only one kind, or may contain two or more kinds having different molecular weights from each other.

[0070] As the PP (B), a substance having an X-ray crystallinity of 30% or more is preferred.

[0071] From the viewpoint of heat resistance, the above-mentioned PP (B) is preferably a polymer having a melting peak of 120°C to 170°C based on a differential scanning calorimeter (DSC), and more preferably a polymer having a melting peak of 150°C to 170°C.

[0072] 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 a titanium-based or metallocene-based compound, an organoaluminum component, an electron donor as required, a carrier, etc.

[0073] From the viewpoints of moldability and impact resistance, the melt flow rate (MFR) of the PP (B) measured under the conditions of 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 further preferably 7 g / 10 min to 50 g / 10 min. It should be noted that the MFR of the 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.

[0074] From the viewpoints of excellent impact resistance and reduced linear expansion coefficient, the density of the PP (B) is preferably 870 kg / m 3 ~930 kg / m 3 and more preferably 880 kg / m 3 ~920 kg / m 3 and further preferably 890 kg / m 3 ~910 kg / m 3 . It should be noted that the density of the PP (B) is a value measured by the water displacement method in accordance with JIS K 7112:1999.

[0075] With respect to the total mass of the peelable layer, the content of the PP (B) in the peelable layer is preferably greater than 0% by mass and less than 40% by mass, more preferably 20% by mass or more and 39% by mass or less, and further preferably 25% by mass or more and 38% by mass or less.

[0076] It is considered that the peelable layer contains PP (B) which has low compatibility with the aforementioned LDPE (A1), so that the sealing strength of the peelable layer and the balance with peelability (sealing strength) are improved.

[0077] As the peeling mechanism when the lid material is peeled from the container, there are three forms: interfacial peeling, interlayer peeling, and cohesive peeling. In the laminate for lid material of the present disclosure, it is considered that the peeling of the lid heat-sealed through the peelable layer from the container is carried out by cohesive failure of the peelable layer.

[0078] The effect of the present disclosure is not yet clear. It is considered that in the peelable layer, LDPE (A1) and PP (B) with low compatibility with LDPE (A1) are mixed to form a resin composition for forming the peelable layer. When the peelable layer is formed into a film, a sea-island structure is formed in which LDPE (A1) with low mutual compatibility forms the sea and PP (B) forms the island. Through the function of the soft LDPE (A1), high sealing strength to the container is achieved. In addition, when the lid material is peeled from the container, cohesive peeling occurs at the interface between the island-forming PP (B) and LDPE (A1), presenting good peelability, and the drawing during opening is suppressed due to the characteristics of the soft LDPE (A1).

[0079] From the viewpoint of being able to appropriately carry out cohesive failure, the content ratio of LDPE (A1) and PP (B) contained in the peelable layer ((A1):(B)=) is preferably 80:20 to 50:50 in terms of mass conversion, and more preferably 75:25 to 55:45 in terms of mass conversion.

[0080] - Tackifying resin (C)-

[0081] The peelable layer contains a tackifying resin (C).

[0082] The tackifying resin (C) has a function of imparting adhesiveness to the resin. Therefore, it is easy to adjust the adhesive strength of the resin composition for forming the peelable layer.

[0083] It is considered that the tackifying resin (C) is compatible with the above-mentioned LDPE (A1) and is contained in the sea part of the sea-island structure in the peelable layer, thereby having a function of improving the sealing strength.

[0084] The tackifying resin (C) is selected from resins having a function of imparting adhesiveness. As the tackifying resin (C), for example, aromatic hydrocarbon resins, alicyclic hydrocarbon resins, aliphatic hydrocarbon resins, terpene resins, rosins, styrene resins, and benzofuran-indene resins can be cited.

[0085] As an aromatic hydrocarbon resin, for example, resins obtained by polymerizing a fraction containing at least one of vinyl aromatic hydrocarbons having 8 to 10 carbon atoms such as vinyltoluene, indene, and α-methylstyrene, resins obtained by copolymerizing these fractions with an aliphatic hydrocarbon fraction, etc. can be cited.

[0086] As an alicyclic hydrocarbon resin, for example, resins obtained by subjecting a diene component in a waste C4 - C5 fraction to cyclodimerization and then polymerizing it, resins obtained by polymerizing cyclic monomers such as cyclopentadiene, resins obtained by subjecting an aromatic hydrocarbon resin to intra-ring hydrogenation (for example, hydrogenated petroleum resin, etc.) can be cited.

[0087] As an aliphatic hydrocarbon resin, for example, resins obtained by polymerizing a fraction containing at least one or more of mono- or di-olefins having 4 to 5 carbon atoms such as 1-butene, isobutene, butadiene, 1,3-pentadiene, and isoprene can be cited.

[0088] As a terpene resin, for example, α-pinene polymers, β-pinene polymers, dipentene polymers, terpene-phenol copolymers, α-pinene-phenol copolymers, their hydrides, etc. can be cited.

[0089] As rosin, for example, ester rosin, wood rosin, tall oil, etc. and their modified products can be cited. As modified products, substances subjected to modification such as hydrogenation, disproportionation, dimerization, and esterification can be cited.

[0090] As a styrene resin, for example, low-molecular-weight resinous polymers obtained by polymerizing styrene monomers such as styrene, vinyltoluene, α-methylstyrene, and cymene can be cited.

[0091] The tackifying resin (C) is preferably a resin having a softening point of 85°C to 130°C, more preferably a resin having a softening point of 100°C to 125°C, and further preferably a resin having a softening point of 110°C to 120°C.

[0092] Generally, when the softening point is 85°C or higher, there is a tendency to exhibit excellent heat resistance, and when it is 130°C or lower, there is a tendency to exhibit excellent effects in terms of imparting adhesiveness.

[0093] The softening point of the tackifying resin (C) can be a value measured based on the softening point test method (ring and ball method) according to JIS K 2207:2006.

[0094] Relative to the total mass of the resin composition for forming the easily peelable layer, the content of the tackifying resin (C) is preferably greater than 0% by mass and less than 25% by mass.

[0095] By making the content of the tackifying resin (C) greater than 0% by mass relative to the total mass of the resin composition for forming the easily peelable layer, the deviation of the adhesive strength to the adherend is suppressed. From the viewpoint of homogenizing the adhesive strength, the content of the tackifying resin (C) is more preferably 3% by mass or more, further preferably 5% by mass or more, and particularly preferably 7% by mass or more relative to the total mass of the resin composition for forming the easily peelable layer.

[0096] In addition, from the viewpoint of achieving good balance between adhesiveness and peelability, the content of the tackifying resin (C) is preferably less than 25% by mass, more preferably 20% by mass or less, further preferably 18% by mass or less, and particularly preferably less than 16% by mass relative to the total mass of the resin composition for forming the easily peelable layer.

[0097] That is, the content of the tackifying resin (C) is more preferably 3% by mass or more and 20% by mass or less, further 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 relative to the total mass of the resin composition for forming the easily peelable layer.

[0098] Commercially available products can be used as the tackifying resin (C) in the easily peelable layer. As commercially available products of the tackifying resin (C), for example, ARKON (registered trademark: the same hereinafter) P140 (manufactured by Arakawa Chemical Industries, Ltd., softening point 140 °C), ARKON P125 (manufactured by Arakawa Chemical Industries, Ltd., softening point 125 °C), ARKON P115 (manufactured by Arakawa Chemical Industries, Ltd., softening point 115 °C), ARKON P100 (manufactured by Arakawa Chemical Industries, Ltd., softening point 100 °C), ARKON P90 (manufactured by Arakawa Chemical Industries, Ltd., softening point 90 °C), etc., hydrogenated alicyclic resins can be cited.

[0099] - Other components -

[0100] In addition to containing the above-mentioned LDPE (A1), PP (B) and tackifying resin (C), the easily peelable layer, specifically the resin composition for forming the easily peelable layer, may contain components other than the above (also referred to as other components) within the range that does not impair the effects of the present invention.

[0101] There is no particular limitation on other components. For example, antistatic agents, antiblocking agents, slip agents, antioxidants, heat stabilizers, light stabilizers, pigments, dyes, etc. can be cited.

[0102] Other components can be used alone or in combination of two or more.

[0103] As antistatic agents, for example, conductive polymers, nonionic surfactants, and anionic surfactants can be cited.

[0104] As an anti-blocking agent, for example, silica, aluminosilicate (such as zeolite), etc. can be cited.

[0105] As a slip agent, for example, polyalkylene glycols such as polyethylene glycol and polypropylene glycol; hydrogenated castor oil, etc. When the easy-peeling layer contains a slip agent, the content of the slip agent is preferably less than 1% by mass, more preferably 0.5% by mass or less, based on the total mass of the resin composition.

[0106] As the content of the above other components, based on the total mass of the easy-peeling layer, the total amount is preferably less than 2% by mass.

[0107] In other words, the total content of LDPE (A1), PP (B) and the aforementioned tackifying resin (C) in the easy-peeling 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 still more preferably 99.5% by mass or more and 100% by mass or less, based on the total mass of the resin components contained in the easy-peeling layer.

[0108] From the viewpoint of the balance between the sealing strength and the easy-peeling property (peeling strength), the thickness of the easy-peeling layer is preferably 3 μm or more and less than 20 μm, more preferably 4 μm to 15 μm, and still more preferably 5 μm to 12 μm.

[0109] <Sealing agent layer>

[0110] In the laminate for a lid material of the present disclosure, a sealing agent layer is provided adjacent to the easy-peeling layer.

[0111] The sealing agent layer is a layer for imparting heat-sealability to the laminate for a lid material. In the laminate for a lid material, the sealing agent layer is the outermost layer on the side in contact with an adherend such as a container. That is, in the laminate for a lid material, the sealing agent layer is a layer in direct contact with an adherend such as a container.

[0112] - High-pressure low-density polyethylene (A2)-

[0113] The sealing agent layer contains high-pressure low-density polyethylene (A2) (hereinafter, also referred to as LDPE (A2)). By making the sealing agent layer contain LDPE (A2), high sealing strength of the laminate for a lid material can be obtained.

[0114] LDPE (A2) is the same low-density polyethylene resin obtained by the high-pressure method as LDPE (A1) contained in the aforementioned easy-peeling layer.

[0115] It should be noted that LDPE (A1) contained in the easy-peeling layer and LDPE (A2) contained in the sealing agent layer may be the same as each other or different.

[0116] The density of LDPE (A2) contained in the sealant layer, as measured in accordance with "Determination of Density and Specific Gravity of Non-Cellular Plastics" in JIS K7112:1999, is 910 kg / m 3 or more and 930 kg / m 3 or less, preferably in the range of 915 kg / m 3 or more and 925 kg / m 3 or less.

[0117] By setting the density within the above range, the adhesion of the sealant layer to the paper container is improved, which is preferable from the viewpoint of the stability of the sealing strength.

[0118] From the viewpoint of suppressing draw at the time of opening, the melt flow rate (hereinafter sometimes referred to as MFR) of LDPE (A2) contained in the sealant layer, as measured in accordance with JIS K 7210-1:2014 under the conditions of 190 °C and a load of 2160 g, is preferably 1.0 g / 10 min or more and 100 g / 10 min or less, more preferably 3.0 g / 10 min or more and 50 g / 10 min or less, further preferably 3.0 g / 10 min or more and 40 g / 10 min or less, and particularly preferably 5.0 g / 10 min or more and 30 g / 10 min or less.

[0119] Relative to the total mass of the sealant layer, the content of LDPE (A2) in the sealant layer is 50% by mass or more. The content of LDPE (A2) in the sealant layer being 50% by mass or more indicates that LDPE (A2) is the main component in the layer.

[0120] Relative to the total mass of the sealant layer, the content of LDPE (A2) in the sealant layer is preferably 50% by mass or more and 100% by mass or less, more preferably greater than 60% by mass and 100% by mass or less, further preferably 70% by mass to 100% by mass, particularly preferably 90% by mass to 100% by mass, and more preferably greater than 95% by mass and 100% by mass or less.

[0121] Relative to the total resin amount of the sealant layer, the content of LDPE (A2) in the sealant layer is preferably 50% by mass or more and 100% by mass or less, more preferably greater than 60% by mass and 100% by mass or less, further preferably 70% by mass to 100% by mass, particularly preferably 90% by mass to 100% by mass, and more preferably greater than 95% by mass and 100% by mass or less.

[0122] - Anti-blocking agent -

[0123] The sealant layer preferably contains an anti-blocking agent. By containing an anti-blocking agent in the sealant layer, the adhesion of the laminate for the lid material is alleviated.

[0124] As an anti-blocking agent, for example, silica, aluminosilicate (such as zeolite), talc, calcium carbonate, starch, etc. can be cited. From the viewpoints of efficiently exhibiting the anti-blocking effect with a small amount of compounding and transparency, silica and zeolite are preferred.

[0125] The sealant layer may contain only one anti-blocking agent or may contain two or more kinds.

[0126] As the content of the anti-blocking agent when the sealant layer contains the anti-blocking agent, based on the total mass of the sealant layer, the content of the anti-blocking 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 still more preferably 0.1% by mass or more and 3.0% by mass or less.

[0127] By making the content of the anti-blocking agent in the sealant layer within the above range, the stickiness of the sealant layer is suppressed, blocking is suppressed, and the transparency of the film is maintained at a high level.

[0128] - Other components -

[0129] Within the range not impairing the effects, the sealant layer may contain other components in addition to LDPE (A2) and the above-mentioned anti-blocking agent as a preferred co-component.

[0130] As other components, for example, thermoplastic resins other than LDPE (A2), thermosetting resins, plasticizers, antioxidants, ultraviolet absorbers, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retardants, catalyst deactivators, inorganic fillers, organic fillers, impact resistance improvers, 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, mildew-proof agents, dispersants, etc. can be cited.

[0131] Other components may be a single kind alone or a combination of two or more kinds.

[0132] As the thermoplastic resin other than LDPE (A2) that the sealant layer may contain (also referred to as other thermoplastic resins), for example, polyolefins, ethylene - unsaturated carboxylic acid copolymers or their ionomers, ethylene - vinyl acetate copolymers (EVA), ethylene - α-olefin copolymer elastomers, etc. can be cited. As the above-mentioned α-olefin, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc. can be cited. Other thermoplastic resins can use commercially available products.

[0133] It should be noted that the resin contained in the sealant layer may be only LDPE (A2).

[0134] The thickness of the sealant layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and still more preferably 5 μm to 12 μm.

[0135] <Layer structure of the laminate for the lid material>

[0136] The laminate for the lid material of the present disclosure is not particularly limited in layer structure as long as it has the aforementioned peelable layer and sealant layer, and may further have other layers, such as a base material layer or any other layer.

[0137] The structure of the laminate for the lid material will be described with reference to the accompanying drawings.

[0138] Figure 1 It is a schematic configuration diagram showing one embodiment of the laminate for the lid material of the present disclosure. Figure 1 The laminate for the lid material 10 has a peelable layer 14 and a sealant layer 12 provided adjacent to the peelable layer 14. Figure 1 In the shown laminate for the lid material 10, the sealant layer 12 becomes the outermost surface and is the layer in contact with an adherend such as a container.

[0139] Figure 2 It is a schematic configuration diagram showing another embodiment of the laminate for the lid material of the present disclosure. Figure 2 In the shown laminate for the lid material 20, it further has a base material layer 16. That is, a peelable layer 14 and a sealant layer 12 are sequentially provided on the surface of the base material layer 16. By further having the base material layer 16, the strength and stability of the lid are further improved. Figure 2 In the shown laminate for the lid material 20, the sealant layer 12 also serves as the outermost surface and becomes the layer in contact with an adherend such as a container.

[0140] -Base material layer-

[0141] The laminate for the lid material of the present disclosure may further have at least one base material layer.

[0142] When the laminate for the lid material of the present disclosure has a base material layer, it is preferable to provide the base material layer adjacent to the aforementioned peelable layer on the side opposite to the side having the sealant layer.

[0143] The base material layer may be provided for the purpose of improving the operability, mechanical properties, heat resistance, etc. of the laminate for the lid material having the peelable layer.

[0144] The base material layer may be a sheet material, a film or other plate-like material.

[0145] Examples of the raw material for the base material layer include papers such as high-grade paper, medium-grade paper, pure white roll paper, coated paper, single-sided coated paper, double-sided coated paper, mixed paper, synthetic paper, and board paper; metals such as aluminum foil; resins such as polyethylene terephthalate; polyethylenes such as high-pressure low-density polyethylene; polypropylenes such as polypropylene homopolymer and polypropylene copolymer; and polyamides. In addition, for the purpose of more effectively suppressing gas permeability and the like, raw materials combining different materials can be used, such as aluminum-vapor-deposited polyester, aluminum-vapor-deposited polypropylene, and silicon-dioxide-vapor-deposited polyester.

[0146] From the viewpoint of reducing the environmental load, the base material layer preferably contains a paper base material. In addition, from the viewpoint of processability, it preferably contains a film or sheet made of polyethylene or polyester.

[0147] Among them, the base material layer preferably contains LDPE (A1). By making the base material layer contain LDPE (A1), the adhesive strength between the base material layer and the easily peelable layer adjacent to the base material layer becomes further good.

[0148] The base material layer can not only be a single-layer structure, but also a laminated structure of two or more layers according to the purpose.

[0149] When the base material layer is provided, from the viewpoints of mechanical strength and workability, the thickness of the base material layer can be set, for example, to be 5 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less.

[0150] Regarding the base material layer, for the purpose of further improving the adhesive strength with the easily peelable layer, the surface on the side laminated with the easily peelable layer can be subjected to corona treatment, plasma treatment, flame treatment, ozone treatment, etc., or anchor coating treatment can also be carried out.

[0151] -Other Layers-

[0152] As any other layer optionally provided in the laminate for the lid material of the present disclosure text in addition to the aforementioned base material layer, there can be mentioned a barrier layer for the purpose of gas barrier property, water vapor barrier property, odor barrier property, etc., an adhesive layer for the purpose of improving the adhesion between different layers, a foamed layer, an inorganic layer, a hard coat layer, an antireflection layer, an antifouling layer, an anchor coating layer, etc.

[0153] As the barrier layer, metal foils such as aluminum foil, aluminum-vapor-deposited polyester, aluminum-vapor-deposited polypropylene, silicon-dioxide-vapor-deposited polyester, etc. can be used.

[0154] The thickness of the barrier layer is preferably 3 μm to 20 μm, more preferably 4 μm to 15 μm, and further preferably 5 μm to 15 μm.

[0155] From the viewpoint of improving the adhesion strength with an adjacent layer, a surface treatment may be performed on the surface of the barrier layer on the side where another resin layer is laminated or on the surface of the side where an optional adhesive layer is laminated. As the surface treatment, for example, physical treatments such as corona treatment, plasma treatment, and flame treatment, and chemical treatments such as anchor coating treatment can be mentioned. Among them, corona treatment is preferably performed on the surface of the barrier layer on the side where the adhesive layer is laminated.

[0156] The adhesive layer is a layer for improving the adhesion between two adjacent layers, such as the aforementioned barrier layer and the sealant layer.

[0157] When the laminate for a lid material of the present disclosure has an adhesive layer, the adhesive layer may be one layer or two or more layers.

[0158] The adhesive layer may contain a known adhesive. For example, the adhesive layer may contain an ionomer of an ethylene - unsaturated carboxylic acid copolymer.

[0159] The thickness of the adhesive layer is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm, and further preferably 10 μm to 20 μm.

[0160] Within the range where the effects of the present disclosure are exhibited, the positions of other layers are not particularly limited. The other layers may be one layer or two or more layers.

[0161] <Preferred Physical Properties of the Laminate for a Lid Material>

[0162] When the laminate for a lid material of the present disclosure is used as a lid material for a container, it preferably has strong sealing strength and easy peelability, that is, low peel strength. Hereinafter, preferred physical properties of the sealing strength of the laminate for a lid material of the present disclosure and the peel strength as an index of easy peelability are given.

[0163] - Sealing Strength -

[0164] Regarding the laminate for a lid material of the present disclosure, when the laminate for a lid material is heat - sealed to the surface of a paper container (for example, a paper cup container) whose surface is coated with polyethylene under the conditions of a gauge pressure of 0.1 MPa, a heating temperature of 160 °C, and a sealing time of 1.0 second, the sealing strength between the laminate for a lid material and the paper container is preferably greater than 30 kPa, more preferably 31 kPa or more, and further preferably 32 kPa or more.

[0165] By making the sealing strength based on the test method shown below greater than 30 kPa, the seal of the container is appropriately maintained under conditions such as vibration, temperature conditions, and stress application during, for example, the transportation of the container, and the protection of the contents is good.

[0166] The test method for the sealing strength will be described in more detail.

[0167] First, place a paper cup container with its surface coated with polyethylene (flange diameter 11 cm) in a cup holder, and place the sample (obtained by cutting the laminate for the lid material of the present disclosure into a size of 100 mm × 100 mm) on the flange of the paper cup container with the center of the opening of the paper cup container aligned with the center of the sample, with the sealant layer side facing down. Then, perform heat sealing under the following heat sealing conditions to produce a test sample of the peelable layer / sealant layer / paper cup container. Then, leave the test sample in an environment of 23°C and 50% RH for 24 hours.

[0168] (Heat sealing conditions)

[0169] · Sealing device: Cup sealer (PACH SEALER Model 0L manufactured by ESHIN PACKIND.CO.,LTD.)

[0170] · Sealing temperature: 160°C

[0171] · Sealing time: 1.0 second

[0172] · Sealing pressure (gauge pressure): 0.1 MPa

[0173] Next, send a certain amount of air into the above test sample under the following conditions until the laminate for the lid material peels off, and measure the maximum pressure when the laminate for the lid material peels off. Take the average value of the maximum pressures measured three times as the sealing strength (kPa).

[0174] (Air supply conditions)

[0175] · Test device: Burst strength tester manufactured by SUN SCIENTIFIC CO.,LTD.

[0176] · Flow rate: 0.8 L / min

[0177] · Temperature: 23°C

[0178] · Humidity: 50% RH

[0179] -Peel strength-

[0180] For the laminate for the lid material of the present disclosure, when the laminate for the lid material is heat-sealed to the surface of a paper container (e.g., a paper cup container) with its surface coated with polyethylene under the conditions of 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 the laminate for the lid material is peeled off from the paper cup container is preferably 5 N or more and 20 N or less, more preferably 5 N or more and 15 N or less, further preferably 7 N or more and 15 N or less, and particularly preferably 8 N or more and 15 N or less.

[0181] By making the peel strength based on the test method shown below 5 N or more, it is possible to suppress the easy opening of the lid material of the container and the reduction of the protection of the contents due to, for example, vibration or stress application during the transportation of the container. In addition, by making the peel strength 20 N or less, for example, it is possible to easily open the lid and suppress the occurrence of wire drawing or the like at the peeled portion.

[0182] The test method for the peel strength will be described in more detail.

[0183] First, a paper cup container (flange diameter 11 cm) with a polyethylene-coated surface is placed in a cup holder, and a sample (obtained by cutting the laminate of the lid material of the present disclosure into a size of 100 mm × 100 mm) is placed on the flange of the paper cup container with the center of the opening of the paper cup container facing the center of the sample on the side of the sealant layer. Then, heat sealing is performed under the following heat sealing conditions to produce a test sample of the peelable layer / sealant layer / paper cup container. Then, the test sample is left in an environment of 23 °C and 50% RH for 24 hours.

[0184] (Heat sealing conditions)

[0185] · Sealing device: Cup sealer (PACH SEALER Model 0L manufactured by ESHIN PACKIND.CO.,LTD.)

[0186] · Sealing temperature: 160 °C

[0187] · Sealing time: 1.0 second

[0188] · Sealing pressure (gauge pressure): 0.1 MPa

[0189] Next, from the corner of the above test sample, the laminate of the lid material is peeled from the paper cup container under the following peeling conditions, and the maximum value of the peel strength at the time of peeling is measured. The average value of the maximum values of the peel strength in the three measurements is taken as the peel strength (N).

[0190] (Peeling conditions)

[0191] · Peeling test device: Peel tester manufactured by IMADA CO.,LTD.

[0192] · Test speed: 500 mm / min

[0193] · Peeling angle: 45°

[0194] · Temperature: 23 °C

[0195] · Humidity: 50% RH

[0196] 〔Lid material〕

[0197] The lid material of the present disclosure includes the laminate for the lid material of the present disclosure described above.

[0198] The lid material of the present disclosure includes the laminate for the lid material of the present disclosure described above and is used as the lid material of a packaging container.

[0199] The lid material of the present disclosure can directly use the laminate for the lid material of the present disclosure described above as the lid material, or can be constituted by including a support body and the laminate for the lid material of the present disclosure described above, and can also have other layers.

[0200] As a structural example of the lid material, for example, a laminated structure including a substrate layer / peelable layer / sealant layer can be cited, and it can also be made into a structure having different resin films as the substrate. For example, a laminated structure of a stretched polyester film / polyethylene film / laminated layer / peelable layer / sealant layer, a laminated structure of a paper substrate layer / laminated layer / peelable layer / adhesive layer / sealant layer, etc. It should be noted that the "stretched polyester film / polyethylene film" in the above layer structure functions as the resin substrate layer of the lid body.

[0201] It should be noted that when the laminate for the lid material of the present disclosure includes a substrate layer, it may not have a support body separately, or may have a support body separately.

[0202] In addition, in order to improve the water vapor barrier property and the odor barrier property, the lid material can also have a barrier layer.

[0203] When manufacturing the laminate for the lid material of the present disclosure and the lid material including the laminate for the lid material, known laminate manufacturing methods such as a method of multi-layer coating a coating liquid for forming each layer constituting the laminate on a support body or a substrate layer, and a method of co-extruding molten resins for forming each layer constituting the laminate to form a film can be appropriately applied to obtain.

[0204] Among them, from the viewpoint of ease of manufacturing, a method of forming a film on a support body or a substrate layer by co-extrusion to form a laminate is preferably used.

[0205] As a usage example of applying the lid material, a lid material that is bonded to a storage container to close an opening can be suitably cited.

[0206] 〔Packaging container〕

[0207] The packaging container of the present disclosure is a container in which one side of a cylinder is closed and the other side has an opening, and the opening is sealed by the lid material by heat-sealing the lid material to the opening, such as the surface of the periphery of the opening, etc.

[0208] Hereinafter, a "container in which one side of the cylindrical body is closed and the other side has an opening" in the packaging container is sometimes referred to as a "bottom material".

[0209] There is no particular limitation on the bottom material of the packaging container of the present disclosure text, and any bottom material can be applied as long as the surface in contact with the sealant layer of the lid material can be heat-sealed.

[0210] The container having a bottom material with an opening and a receiving portion applied in the packaging container of the present disclosure text is preferably a container in which at least the outermost surface, that is, the outermost surface in contact with the sealant layer of the lid material, is formed of a resin material. Among them, from the viewpoint of reducing the environmental load, the aforementioned bottom material is preferably a paper container (for example, a paper cup container) whose surface on the side in contact with the lid material is coated with polyethylene.

[0211] The packaging container of the present disclosure text is a container that has an appropriate peel strength and good peelability when the heat-sealed lid material is peeled off, can suppress the occurrence of drawing during peeling, and has a stable sealing strength during sealing, can suppress undesired peeling during storage or transportation, and has excellent protection for the contents.

[0212] <Paper container>

[0213] A paper container, which is a suitable bottom material for the packaging container of the present disclosure text, will be described.

[0214] The paper container is a paper container in which the surface of a paper substrate heat-sealed through the sealant layer of the lid material is coated with polyethylene. The paper container can be a paper cup container obtained by forming a paper substrate whose surface is coated with polyethylene into a cup shape.

[0215] There is no particular limitation on the paper substrate for forming the paper cup container as long as it can be formed into a paper cup container. The paper cup container can have other layers on the side opposite to the surface coated with polyethylene of the paper substrate in addition to the paper substrate coated with polyethylene.

[0216] As the other layers, for example, a polyethylene layer, a paper substrate, a substrate layer, an adhesive layer, an antifouling layer, etc. can be cited.

[0217] The other layers can be one layer or two or more layers.

[0218] 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 containing structural units derived from ethylene as the main body.

[0219] As the ethylene polymer, an ethylene homopolymer or an ethylene copolymer containing 50% by mass or more of structural units derived from ethylene relative to the whole polymer is preferred, and an ethylene homopolymer is more preferred.

[0220] The heat-sealed surface of the paper cup container may be coated with components other than polyethylene.

[0221] The paper cup container may have a flange portion heat-sealed via a sealant layer of a lid material. In the case of having a flange portion, the surface of the flange portion is also preferably coated with polyethylene.

[0222] The packaging container can be suitably used as, for example, a packaging container for packaging foods, beverages, liquids other than beverages, pharmaceuticals, industrial supplies, daily necessities, cosmetics, etc., and can be particularly suitably used as a packaging container for foods and pharmaceuticals. In the paper cup container, foods, beverages, liquids other than beverages, pharmaceuticals, industrial supplies, daily necessities, cosmetics, etc. can be accommodated, and foods, beverages, or pharmaceuticals can be accommodated.

[0223] Hereinafter, an example of the packaging container of the present disclosure will be described with reference to the drawings.

[0224] Figure 3 To show the use of Figure 2 A schematic configuration diagram of an example of a packaging container using the laminate 20 for lid material having the base material layer 16 shown as the laminate for lid material.

[0225] Figure 3 The packaging container 30 shown directly uses Figure 2 The laminate 20 for lid material described as the lid material 20. The packaging container 30 includes a paper cup container 18 and a lid material 20, and can accommodate contents such as foods in the space corresponding to the accommodating portion of the paper cup container 18. The paper cup container 18 has a polyethylene layer formed by coating polyethylene on the surface of the paper substrate. The paper cup container 18 has a flange portion at the opening. By heat-sealing the sealant layer 12 of the lid material 20 to the polyethylene layer on the surface of the flange portion, the opening is sealed with the lid material 20. When the lid material 20 is peeled off from the packaging container 30, the occurrence of wire drawing is suppressed, so that the mixing of foreign substances such as resin into the contents and the reduction of the touch when the mouth touches the flange portion to eat the contents are suppressed.

[0226] Examples

[0227] Hereinafter, based on the examples, specific examples will be given to further describe in detail the packaging container using the laminate for lid material of the present disclosure. However, the following examples are merely examples of the lid material and packaging container of the present disclosure, and it goes without saying that the present disclosure includes various modification examples.

[0228] In the following examples and comparative examples, the following materials are used.

[0229] <High-pressure low-density polyethylene (A2) (LDPE (A2))>

[0230] · HP-LDPE1 (manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD., MFR (at 190°C, 2160 g load): 23 g / 10 min, density: 918 kg / m 3 , melting point: 106°C)

[0231] · HP-LDPE2 (manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD., MFR (at 190°C, 2160 g load): 7.2 g / 10 min, density: 918 kg / m 3 , melting point: 108°C)

[0232] · HP-LDPE3 (manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD., MFR (at 190°C, 2160 g load) 4.5 g / 10 min, density 923 kg / m 3 , melting point: 111°C)

[0233] · HP-LDPE4 (manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD., MFR (at 190°C, 2160 g load): 70 g / 10 min, density: 916 kg / m 3 , melting point: 104°C)

[0234] <Propylene homopolymer (B) (PP(B))>

[0235] · Homogeneous PP1 (manufactured by Prime Polymer Co., Ltd., Prime Polypro (registered trademark) F113G, MFR (at 230°C, 2160 g load): 3.0 g / 10 min, density: 910 kg / m 3 )

[0236] <Tackifying resin (C)>

[0237] · Tackifying resin 1: Alicyclic hydrocarbon resin (manufactured by Arakawa Chemical Industries, Ltd., ARKON (registered trademark) P115)

[0238] <Other resins>

[0239] · Linear low density polyethylene (L-LDPE, manufactured by Prime Polymer Co., Ltd., Evolue (registered trademark) SP2540), MFR (at 190°C, 2160 g load): 3.8 g / 10 min, density: 924 kg / m 3 , melting point: 120°C)

[0240] <Additives>

[0241] · Anti - blocking agent: Aluminum silicate (manufactured by Mizusawa Chemical Co., Ltd., SILTON (registered trademark) JC - 50)

[0242] · Release agent: Erucamide (ELA, manufactured by NOF Corporation)

[0243] · Slip agent: Polyethylene glycol (PEG, manufactured by Nippon Fine Chemical Co., Ltd.)

[0244] [Examples 1 - 6 and Comparative Example 1]

[0245] <Production of resin composition for forming sealant layer>

[0246] The materials were premixed in the mixing ratio shown in Table 1 (the unit of the materials in Table 1 represents parts by mass) so that the charging amount became 10 kg, and dry blending was carried out to produce a resin composition (P) for forming a sealant layer.

[0247] <Production of resin composition for forming easily peelable layer>

[0248] The materials were premixed in the mixing ratio of 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 part by mass of release agent, and 0.1 part by mass of slip agent so that the charging amount became 10 kg, and then were put into a single - screw extruder with a screw diameter of 65 mmφ (screw effective length: L / D = 28), and melt - kneaded at a processing temperature of 240 °C to produce a resin composition for forming an easily peelable layer (hereinafter, also referred to as EZP).

[0249] Among all the components in EZP, the total content of LDPE(A1), PP(B) and tackifying resin (C) is 99.8% by mass, and the content ratio of PP(B) to LDPE(A1) is 1:0.696.

[0250] <Production of laminate>

[0251] A multilayer casting film forming machine was used to produce a molten film formed of a laminated layer / easily peelable layer / sealant layer.

[0252] The aforementioned HP - LDPE1 was used in the formation of the laminated layer.

[0253] In the formation of the easily peelable layer, the aforementioned resin composition for forming the easily peelable layer (EZP) is used. In the formation of the sealant layer, the aforementioned resin composition for forming the sealant layer (P) is used. At a processing temperature of 220°C, the thickness of each layer is configured such that the laminate layer / easily peelable layer / sealant layer = 15 μm / 7 μm / 7 μm. A base material layer (which is formed by laminating 15 μm of low-density polyethylene (manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD., MIRASON (registered trademark) 11P) on a prefabricated 12-μm stretched polyester film (manufactured by Toray Industries, Inc., Lumirror (registered trademark))) is laminated on the laminate layer side of the above-mentioned molten film by extrusion lamination in such a way that the low-density polyethylene side of the base material layer is adhered, to produce a laminate for a lid material.

[0254] The layer constitution and thickness of the laminate for a lid material are a stretched polyester film (base material layer) / polyethylene (base material layer) / laminate layer / easily peelable layer / sealant layer = 12 μm / 15 μm / 15 μm / 7 μm / 7 μm.

[0255] The multi-layer casting film forming machine used above is a 3-layer multi-layer casting forming machine manufactured by TANABE PLASTICS MACHINERY CO., LTD. All the forming machines are single-screw extruders with a screw diameter of 40 mmφ and a die width of 500 mm. The co-extrusion feed head is manufactured by EDI Corporation.

[0256] [Evaluation of Sealing Strength]

[0257] A paper cup container with its surface coated with polyethylene (polyethylene-coated cup, diameter of the flange part 11 cm) is placed on a cup holder, and a sample (obtained by cutting the laminate for a lid material into a size of 100 mm × 100 mm) is placed on the flange of the aforementioned 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 being opposite. Then, heat sealing is performed under the following heat sealing conditions to obtain a test sample having a layer constitution of a stretched polyester film / polyethylene / laminate layer / easily peelable layer / sealant layer / polyethylene-coated cup. Then, it is left in an environment of 23°C and 50% RH for 24 hours.

[0258] <Heat Sealing Conditions>

[0259] · Sealing device: Cup sealer (PACH SEALER Model 0L manufactured by ESHIN PACKIND.CO., LTD.)

[0260] · Sealing temperature: 160°C

[0261] · Sealing time: 1.0 second

[0262] · Sealing pressure (gauge pressure): 0.1 MPa

[0263] Next, a certain amount of air is sent into the test sample prepared above under the following conditions until the laminate is peeled off, and the maximum pressure at the time of laminate peeling is measured. The average value of the maximum pressures in the three measurements is taken as the sealing strength (kPa).

[0264] <Air supply conditions>

[0265] · Test device: Rupture strength testing machine manufactured by SUN SCIENTIFIC CO., LTD.

[0266] · Flow rate: 0.8 L / min

[0267] · Temperature: 23 °C

[0268] · Humidity: 50% RH

[0269] The sealing strength is evaluated according to the following criteria.

[0270] <Evaluation criteria>

[0271] A: The maximum pressure at the time of laminate peeling is greater than 30 kPa

[0272] B: The maximum pressure at the time of laminate peeling is 30 kPa or less

[0273] [Evaluation of peel strength (cup seal strength)]

[0274] A paper cup container with a polyethylene-coated surface (polyethylene-coated cup, flange diameter 11 cm) is placed on the cup holder, and the sealant layer side of the lid material sample (obtained by cutting the lid material laminate into a size of 100 mm × 100 mm) is placed on the flange of the aforementioned paper cup container with the center of the opening of the paper cup container facing the center of the sample. Next, heat sealing is performed under the following heat sealing conditions to obtain a test sample having a layer structure of stretched polyester film / polyethylene / laminated layer / easy-peeling layer / sealant layer / polyethylene-coated cup. Then, it is left in an environment of 23 °C and 50% RH for 24 hours.

[0275] <Heat sealing conditions>

[0276] · Sealing device: Cup sealer (PACH SEALER Model 0L manufactured by ESHIN PACK IND.CO., LTD.)

[0277] · Sealing temperature: 160 °C

[0278] · Sealing time: 1.0 second

[0279] · Sealing pressure (gauge pressure): 0.1 MPa

[0280] Next, from the corner of the test sample prepared above, the laminate for the lid material was peeled off from the polyethylene-coated cup under the following peeling conditions, and the maximum value of the peeling strength at the time of peeling was measured. The average value of the maximum values of the peeling strength in the three measurements was defined as the peeling strength (N).

[0281] <Peeling conditions>

[0282] · Peeling test device: Peeling tester manufactured by IMADA CO., LTD.

[0283] · Test speed: 500 mm / minute

[0284] · Peeling angle: 45°

[0285] · Temperature: 23°C

[0286] · Humidity: 50% RH

[0287] The peeling strength was evaluated according to the following criteria.

[0288] <Evaluation criteria>

[0289] A: The peeling strength is 5 N or more and 15 N or less

[0290] B: The peeling strength is less than 5 N or greater than 15 N

[0291] [Evaluation of peeling state]

[0292] A skilled technician observed the side surface of the sealant layer of the laminate after the peeling strength measurement used in the above peeling strength measurement (the sample from which the sealant layer and the polyethylene-coated cup were peeled).

[0293] Sometimes, fine filamentous resin is formed at the peeling part. This is generally called the wire drawing phenomenon. The occurrence or non-occurrence of wire drawing was recorded visually.

[0294] The wire drawing phenomenon not only deteriorates the appearance, but is also undesirable from the viewpoint of foreign matter mixing such as the attachment of filament pieces to the contents when taking out food and other contents.

[0295] The peeling state was evaluated according to the following criteria. Evaluations AA to B are levels that are practically problem-free, and evaluations AA and A are preferred levels.

[0296] <Evaluation criteria>

[0297] AA: No wire drawing was confirmed at all

[0298] A: Almost no wire drawing was confirmed

[0299] B: Slight wire drawing was confirmed

[0300] C: Scattered into filaments

[0301] [Table 1]

[0302]

[0303] As can be seen from Table 1, compared with Comparative Example 1, the sealing strength of Examples 1 to 5 is high, and the peel strength is suppressed to be low. In addition, the filaments after peeling are suppressed, and the peeling state is at a level that is practically no problem.

[0304] From the above, it can be confirmed that according to the present embodiment, when the obtained laminate for lid material is used as the lid material of a packaging container, high sealing strength and low peel strength, that is, sealing strength and easy peelability, can be achieved simultaneously, and the occurrence of filaments during opening can be suppressed.

[0305] Explanation of reference numerals

[0306] 10 Laminate for lid material

[0307] 12 Sealing agent layer

[0308] 14 Easy peelability layer

[0309] 16 Base material layer

[0310] 18 Paper cup container

[0311] 20 Laminate for lid material (lid)

[0312] 30 Packaging container

[0313] The disclosure of Japanese Patent Application No. 2022-186014 filed on November 21, 2022 is incorporated herein by reference.

[0314] All documents, patent applications, and technical standards described in this disclosure text are incorporated herein by reference, and the degree to which each document, patent application, and technical standard is incorporated by reference is the same as the degree of the case where it is specifically and separately described.

Claims

1. A laminate for a lid material, comprising: A peelable layer; and A sealant layer adjacent to the peelable layer, The peelable layer contains low density polyethylene by high pressure method (A1), polypropylene homopolymer (B), and a tackifying resin (C), The sealant layer contains low density polyethylene by high pressure method (A2), Relative to the total mass of the sealant layer, the content of the low density polyethylene by high pressure method (A2) in the sealant layer is 50% by mass or more, The thickness of the 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 lid material laminate that contacts the adherend.

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

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

4. The laminate for lid materials according to claim 1, wherein, Relative to the total mass of the peelable layer, the content of the polypropylene homopolymer (B) in the peelable layer is more than 0% by mass and less than 40% by mass.

5. The laminate for lid material according to claim 1, wherein, The content ratio of the low density polyethylene by high pressure method (A1) and the polypropylene homopolymer (B) contained in the peelable layer ((A1):(B)=) is 80:20 to 50:50 in terms of mass conversion.

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

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

8. The laminate for lid material according to claim 1, wherein, The sealant layer further contains an anti-blocking agent.

9. The laminate for a lid material according to claim 8, wherein, Relative to the total mass of the sealant layer, the content of the anti-blocking agent is 0.1% by mass or more and 5.0% by mass or less.

10. The laminate for lid material according to claim 1, wherein, On the side of the peelable layer opposite to the side having the sealant layer, at least one substrate layer is provided adjacent to the peelable layer.

11. The laminate for lid material according to claim 10, wherein, The substrate layer contains low density polyethylene by high pressure method (A1).

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

13. The laminate for lid material according to claim 1, wherein, When the lid material laminate is heat-sealed to the surface of a paper container whose surface is coated with polyethylene under the conditions of 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 the lid material laminate is peeled from the paper container is 5 N or more and 20 N or less.

14. A lid material, comprising the laminate for lid material according to any one of claims 1 to 13.

15. A packaging container, comprising: the lid material according to claim 14; and a container having one side of the cylindrical body closed and an opening on the other side, wherein the opening is sealed with the lid material by heat-sealing the lid material through a sealant layer at the opening.

16. The packaging container according to claim 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.

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