Easily-openable lid member and lid-provided container having easily-openable lid member

Abstract

As shown in fig. 1, an easily-openable lid member (100) according to the present invention includes a base material layer (102), an inorganic particle-containing layer (104), and a sealant layer (106). The inorganic particle-containing layer (104) contains a polyethylene-based resin and inorganic particles dispersed in the polyethylene-based resin. The percentage content of the inorganic particles is 25 mass% or more with respect to the mass of the inorganic particle-containing layer (104). The sealant layer (106) contains a polyethylene-based resin and a polypropylene-based resin. The polyethylene-based resin and the polypropylene-based resin are compatible to each other.

Description

Easy-to-open lid material and lidded container having easy-to-open lid material

[0001] The present invention relates to an easy-open lid material, and more particularly to an easy-open lid material having an inorganic particle-containing layer.

[0002] Lid materials have been proposed in the past, the inner layer of which contains a functional material such as an oxygen absorber or a moisture absorber, particularly inorganic particles. These lid materials generally consist of a heat seal layer, a resin layer containing a functional material such as an oxygen absorber, and a gas barrier layer, and this functional lid material is tightly integrated with the upper surface of the flange of the container body by heat sealing.

[0003] In such lid materials, the melting point of the resin in the functional material layer, such as the oxygen absorber layer, is usually close to the melting point of the resin in the heat-sealable layer. Therefore, when such a lid material is heat-sealed to the upper surface of the flange of the container body to form an intimate and integrated unit, the heat and pressure during heat-sealing melt not only the resin in the heat-sealable layer but also the resin in the functional material layer, causing the resins in the heat-sealable layer and the functional material layer to mix together in a compatible or incompatible state, which can result in the functional material in the functional material layer being mixed into the heat-sealable layer. If the functional material is mixed into the heat-sealable layer in this way, the functional material may be exposed when the container is opened, damaging the aesthetic appearance.

[0004] In order to solve such problems, Patent Document 1 discloses an easy-open lid member having a functional resin layer, which is formed from a laminated film material having at least a barrier layer, a functional resin layer, and a heat-seal layer, and is characterized in that a high-melting point resin layer is provided between the functional resin layer and the heat-seal layer.

[0005] JP 2009-12787 A

[0006] Although Patent Document 1 can mitigate to some extent the problem of the exposure of the functional material when the lid is opened, if the content of the functional material is increased, the layer containing the functional material becomes brittle, and as a result, this layer may break when the lid is opened, exposing the functional material.

[0007] In addition, in order to ensure sufficient sealing strength of the resulting lidded container, it is sometimes preferable to perform heat sealing at a relatively high temperature and / or pressure. When such heat sealing conditions are adopted, the inorganic particles tend to dissolve in the sealant layer, and therefore the problem of exposure of the functional material can become significant.

[0008] The present invention provides a novel easy-to-open lid material that can suppress the problem of exposure of inorganic particles when opened, even when the inorganic particle content of the inorganic particle-containing layer is relatively high and heat sealing is performed under conditions that result in relatively high sealing strength.

[0009] After extensive research, the present inventors have found that the above-mentioned problems can be solved by the following means, and have thus completed the present invention. Specifically, the present invention is as follows: <Aspect 1> An easily openable lid material comprising at least a substrate layer, an inorganic particle-containing layer, and a sealant layer, wherein the inorganic particle-containing layer contains a polyethylene-based resin and inorganic particles dispersed in the polyethylene-based resin, the content of the inorganic particles being 25% by mass or more relative to the mass of the inorganic particle-containing layer, and the sealant layer containing a polyethylene-based resin and a polypropylene-based resin, the polyethylene-based resin and the polypropylene-based resin being compatible with each other. <Aspect 2> The easily openable lid material according to Aspect 1, wherein the polypropylene-based resin is block polypropylene and / or random polypropylene. <Aspect 3> The easily openable lid material according to Aspect 1 or 2, wherein the inorganic particles are an oxygen absorber and the substrate layer is a barrier substrate layer. <Aspect 4> The easily openable lid material according to Aspect 3, wherein the oxygen absorber is iron powder. <Aspect 5> The easy-open lid according to Aspect 3 or Aspect 4, wherein the barrier substrate layer is composed of a substrate resin layer and a barrier layer. <Aspect 6> The easy-open lid according to Aspect 5, wherein the barrier layer is an inorganic vapor deposition film or an organic coating film. <Aspect 7> The easy-open lid according to any one of Aspects 1 to 6, wherein the inorganic particle-containing layer has a skin layer on the surface thereof facing the substrate layer. <Aspect 8> The easy-open lid according to Aspect 7, wherein the skin layer, the inorganic particle-containing layer, and the sealant layer are fused to one another. <Aspect 9> The easy-open lid according to Aspect 8, wherein the skin layer, the inorganic particle-containing layer, and the sealant layer are a three-layer inflation film. <Aspect 10> A lidded container comprising: a container having a flange portion and a storage portion; and the easy-open lid according to any one of Aspects 1 to 9 heat-sealed to the flange portion of the container, wherein the surface of the container heat-sealed to the easy-open lid is composed of a polypropylene-based resin. <Aspect 11> A lidded container with contents, having contents accommodated in the accommodation portion of the lidded container according to Aspect 10. <Aspect 12> A lidded container with contents according to Aspect 11, wherein the contents are cooked rice.

[0010] According to the present invention, a novel easy-open lid material can be provided that can suppress the problem of exposure of inorganic particles when opened, even when the inorganic particle content of the inorganic particle-containing layer is relatively high and heat sealing is performed under conditions that result in relatively high sealing strength.

[0011] Fig. 1 is a side cross-sectional view of the easy-open lid material of the present invention. Fig. 2(a) is a top view of the lidded container of the present invention. Fig. 2(b) is a side cross-sectional view taken along line IIb-IIb in Fig. 2(a).

[0012] <<Easy-open Lidding Material>> As shown in FIG. 1 , the easy-open lid material 100 of the present invention contains at least a base layer 102, an inorganic particle-containing layer 104, and a sealant layer 106, wherein the inorganic particle-containing layer 104 contains a polyethylene-based resin and inorganic particles dispersed in the polyethylene-based resin, the content of the inorganic particles is 25 mass% or more relative to the mass of the inorganic particle-containing layer 104, and the sealant layer 106 contains a polyethylene-based resin and a polypropylene-based resin, and the polyethylene-based resin and the polypropylene-based resin are compatible with each other.

[0013] In this specification, a polyethylene-based resin refers to a resin that contains more than 50 mol%, 60 mol% or more, 70 mol% or more, or 80 mol% or more of repeating units of ethylene groups in the main chain of the polymer, and is selected from the group consisting of, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), derivatives thereof, and mixtures thereof.

[0014] In this specification, a polypropylene-based resin refers to a resin containing repeating units of propylene groups in the main chain of the polymer in an amount of more than 50 mol%, 60 mol% or more, 70 mol% or more, or 80 mol% or more, and examples thereof include polypropylene (PP) homopolymer, random polypropylene (random PP), block polypropylene (block PP), chlorinated polypropylene, acid-modified polypropylene, derivatives thereof, and mixtures thereof.

[0015] Furthermore, among the above-mentioned "polypropylene-based resins," "polypropylene homopolymer" refers to a homopolymer obtained by polymerizing only propylene, "random polypropylene" refers to a random copolymer obtained by polymerizing propylene in the presence of a comonomer such as ethylene, and "block polypropylene" refers to a block copolymer obtained by polymerizing propylene and then further polymerizing it in the presence of a comonomer such as ethylene.

[0016] When the content of inorganic particles in the inorganic particle-containing layer is increased, the inorganic particle-containing layer becomes brittle, and as a result, the inorganic particle-containing layer may break when the lid is opened, exposing the inorganic particles. In particular, when heat sealing is performed at a relatively high temperature and / or pressure to ensure sufficient sealing strength of the resulting lidded container, the problem of inorganic particle exposure may become significant.

[0017] In response to this, the present inventors have found that the above-described configuration can suppress the problem of exposure of inorganic particles even when the inorganic particle-containing layer has a relatively high inorganic particle content, particularly when the inorganic particle-containing layer has a relatively high inorganic particle content and heat sealing is performed under conditions that result in relatively high sealing strength.

[0018] Without wishing to be bound by theory, it is believed that when a sealant layer in which a polyethylene-based resin and a polypropylene-based resin are compatible is heat-sealed to a surface of a container, particularly the surface of the container made of a polypropylene-based resin, under conditions that provide sufficient sealing strength, the sealant layer and the container are bonded via the portion of the polypropylene-based resin that is made of a propylene monomer. On the other hand, it is believed that sufficient adhesive strength is also obtained between the inorganic particle-containing layer and the sealant layer via the polyethylene resin that constitutes the inorganic particle-containing layer and the polyethylene resin that constitutes the sealant layer.

[0019] When peeling the lid from the container to open it, it is believed that the polyethylene resin present at the interface between the sealant layer and the container is the trigger for peeling the lid. At this time, because the polyethylene resin and polypropylene resin in the sealant layer are compatible, the sealant layer itself has sufficient strength, making it less likely to break. This resistance to breakage of the sealant layer itself is thought to promote peeling at the interface between the container and the sealant layer, thereby preventing the problem of exposure of inorganic particles when opening the container.

[0020] In this specification, "easy-open lid material" generally means a lid material that can be easily opened by hand when attached to a container, and is sometimes referred to as an "easy-peel lid material" by those skilled in the art. Whether a lid material is easy to open or not can be evaluated by sensory evaluation. Furthermore, the opening strength of a lidded container using such an easy-open lid material can generally be 30 N / 15 mm or less, 25 N / 15 mm or less, 20 N / 15 mm or less, 15 N / 15 mm or less, or 10 N / 15 mm or less. This opening strength can be measured, for example, at a temperature of 150°C and a pressure of 3 kgf / cm. －２ The peel strength can be obtained by heat-sealing the sample to a polypropylene film under conditions of 1.5 seconds, 180° peeling at 300 mm / min for a peeling time of 1.5 seconds, and then peeling the portion corresponding to the heat-sealed portion at an angle of 180° using a measuring device at a peel speed of 300 mm / min and a peel length of 35 mm, and calculating the average peel strength over a peel length of 10 to 30 mm in the portion corresponding to the heat-sealed portion.

[0021] Although not shown in Fig. 1, the easy-open lid material of the present invention may have a skin layer on the surface of the inorganic particle-containing layer facing the base layer, i.e., on the surface opposite the sealant layer. In this case, the skin layer, the inorganic particle-containing layer, and the sealant layer may be fused to one another.

[0022] In this case, the skin layer, the inorganic particle-containing layer, and the sealant layer can be produced by simultaneously forming and laminating the skin layer, the inorganic particle-containing layer, and the sealant layer by a three-layer inflation method, i.e., the skin layer, the inorganic particle-containing layer, and the sealant layer may be a three-layer inflation film.

[0023] Although not shown in FIG. 1, the easy-open lid material of the present invention may have a tab that can be grasped and pulled up when opening.

[0024] The easily openable lid material of the present invention may be a lid material for heat sealing to the surface of a container made of a polypropylene-based resin.

[0025] Each component of the present invention will be described below.

[0026] <Base layer> The easy-open lid material has a base layer. The base layer may be a base layer having at least a barrier layer. In particular, when the inorganic particles are a gas absorbent, it is preferable that the base layer be a barrier base layer from the viewpoint of suppressing absorption of gas from the outside.

[0027] The barrier substrate layer may have a substrate resin layer and a barrier layer. The substrate resin layer and the barrier layer may each be present in one or more layers, and these layers may be laminated via an adhesive layer.

[0028] In particular, from the viewpoint of protecting the barrier layer, it is preferable that the barrier substrate layer has a first substrate resin layer, a barrier layer, and a second substrate resin layer in this order. In particular, in this embodiment, it is preferable that at least one of the first and second substrate resin layers is a polyamide resin, particularly nylon, from the viewpoint of puncture resistance.

[0029] (Base resin layer) The base resin layer may be composed of a thermoplastic resin having excellent impact resistance, abrasion resistance, etc., such as a vinyl resin, a polyester resin, a polyamide resin, a polypropylene resin, etc. The base resin layer may be a single layer or a laminate.

[0030] Examples of vinyl resins include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polychlorotrifluoroethylene, polytetrafluoroethylene, and polyacrylonitrile (PAN).

[0031] Examples of polyester resins include polyethylene terephthalate (PET) and polybutylene terephthalate.

[0032] Examples of polyamide resins include nylons such as Nylon (registered trademark) 6 and Nylon MXD6.

[0033] As the polypropylene-based resin, the resins mentioned below in relation to the inorganic particle-containing layer can be used.

[0034] The thickness of the substrate resin layer is preferably 7 μm or more or 10 μm or more from the viewpoint of the mechanical strength of the packaging laminate. From the viewpoint of the flexibility of the substrate resin layer, the thickness is preferably 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. That is, the substrate resin layer may be a soft substrate resin layer.

[0035] The resin constituting the base resin layer may be one type or a blend of two or more types, and additives for imparting functionality, etc. may be blended as necessary.

[0036] The base resin layer is preferably produced from a preformed film. The film to be the base resin layer may be any film formed from the above-mentioned resins, and may be unstretched or uniaxially or biaxially stretched. Of these, a biaxially stretched film is preferred.

[0037] (Barrier Layer) As the barrier layer, a material can be used that can prevent moisture, organic gases, inorganic gases, etc. from permeating from the barrier substrate layer side to the sealant layer side, and / or, particularly when the inorganic particles are oxygen absorbers, prevent oxygen from permeating from the outside, thereby deactivating the inorganic particle-containing layer. Examples of such barrier layers that can be used include metal foil layers, inorganic vapor deposition films, organic coating films, and barrier resin layers. In particular, when the contents are microwaveable foods, inorganic vapor deposition films, organic coating films, and barrier resin layers can be used as the barrier layer.

[0038] As the metal foil layer, for example, a simple metal foil layer such as copper foil or aluminum foil, or an alloy foil layer such as stainless steel foil can be used.

[0039] Examples of inorganic vapor-deposited films that can be used include aluminum vapor-deposited films, silica vapor-deposited films, alumina vapor-deposited films, and silica-alumina binary vapor-deposited films. In particular, examples of such inorganic vapor-deposited films that can be used include commercially available films that are vapor-deposited on a film, such as "vapor-deposited PET."

[0040] As the organic coating film, for example, a polyvinylidene chloride coating film, a polychlorotrifluoroethylene coating film, or a polyvinylidene fluoride coating film can be used.

[0041] As the barrier resin layer, for example, ethylene-vinyl alcohol copolymer (EVOH), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), or the like can be used.

[0042] When an inorganic vapor deposition film or an organic coating film is used as the barrier layer, the thickness of the barrier layer is preferably 100 nm or more, 200 nm or more, 300 nm or more, 500 nm or more, 700 nm or more, or 1 μm or more from the viewpoint of ensuring strength and barrier properties, and is preferably 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less from the viewpoint of reducing the overall thickness of the easy-open lid material.

[0043] When a metal foil layer or a barrier resin layer is used as the barrier layer, the thickness of the barrier layer is preferably 5 μm or more, or 7 μm or more, from the viewpoint of ensuring strength and barrier properties, and is preferably 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less, from the viewpoint of reducing the overall thickness of the easy-open lid material.

[0044] (Adhesive Layer) As the adhesive layer, for example, a dry laminating adhesive, a hot laminating adhesive, or the like can be used.

[0045] <Inorganic Particle-Containing Layer> The inorganic particle-containing layer contains inorganic particles and a polyethylene resin. The content of the inorganic particles is 25% by mass or more.

[0046] The inorganic particle-containing layer may be fused to the sealant layer. In addition, when the easily peelable lid material has a skin layer, the inorganic particle-containing layer may be fused to the skin layer.

[0047] The thickness of the inorganic particle-containing layer may be 5 to 100 μm. This thickness may be 5 μm or more, 7 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more, or may be 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 33 μm or less, less than 30 μm, 25 μm or less, 20 μm or less, or 18 μm or less. In particular, a thickness of less than 30 μm is preferred from the viewpoint of obtaining good heat seal strength.

[0048] In particular, when the inorganic particles are iron powder, the inorganic particle-containing layer may further contain an oxidation promoter.

[0049] In particular, when the inorganic particles are iron powder, the inorganic particle-containing layer may further contain an oxygen absorber other than iron powder.

[0050] (Polyethylene Resin) As the polyethylene resin, those mentioned above can be used.

[0051] The density of polyethylene resin is 0.900 g / cm ３ 0.950g / cm or more ３ or less, for example 0.900 g / cm ３ Above, 0.905g / cm ３ Above, 0.910g / cm ３ Above, 0.915g / cm ３ or more, or 0.920 g / cm ３ or more, and may be 0.950 g / cm ３ Below, 0.945g / cm ３ Below, 0.940g / cm ３ Below, 0.935g / cm ３or less, or 0.930 g / cm ３ In particular, the density may be 0.930 g / cm or less. ３ From the viewpoint of heat seal strength, it is preferable that the above-mentioned value is as follows.

[0052] When a polyethylene resin is used as the polyolefin resin, the melting point of the polyethylene resin may be 95°C or higher and 130°C or lower, for example, 95°C or higher, 100°C or higher, or 105°C or higher, or 130°C or lower, 125°C or lower, 120°C or lower, 115°C or lower, or 110°C or lower.

[0053] In this specification, the melting point means the melting point measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121:1987.

[0054] (Inorganic Particles) The inorganic particles are inorganic particles dispersed in a thermoplastic resin.

[0055] As the inorganic particles, for example, gas absorbents, inorganic pigments, etc. can be used.

[0056] Examples of gas absorbents that can be used include oxygen absorbents such as iron powder and organic gas absorbents such as hydrophobic zeolite. Examples of iron powder that can be used include reduced iron powder, atomized iron powder, activated iron powder, etc. Commercially available masterbatches can be used as such iron powders.

[0057] Examples of inorganic pigments that can be used include known inorganic color pigments, flaky metal pigments such as aluminum powder, and luster pigments such as pearl pigments.

[0058] The content of inorganic particles in the inorganic particle-containing layer may be 25 to 80% by mass, and may be 25% by mass or more, 28% by mass or more, 30% by mass or more, 33% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 48% by mass or more, or 50% by mass or more, and may be 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less, based on the mass of the inorganic particle-containing layer.

[0059] (Prooxidant) As the prooxidant, alkali metal chlorides such as sodium chloride, alkaline earth metal oxides such as calcium chloride and magnesium chloride, and the like can be used.

[0060] The content of the pro-oxidant may be 1 to 30% by mass relative to the mass of the iron powder, and may be 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, or 10% by mass or more, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less, relative to the mass of the iron powder.

[0061] (Other Oxygen Absorbers) As oxygen absorbers other than iron powder, iron compounds such as ferrous oxide and ferrous salts, metal halides such as calcium chloride and magnesium chloride, and metal oxides such as cerium oxide can be used.

[0062] The content of the other oxygen absorbent may be 10% by mass or less, 7% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, or 0% by mass relative to the mass of the inorganic particle-containing layer.

[0063] <Sealant Layer> The sealant layer contains a polyethylene resin and a polypropylene resin. The polyethylene resin and the polypropylene resin are compatible with each other. This compatibility may be achieved by a compatibilizer.

[0064] The thickness of the sealant layer may be greater than 10 μm and less than or equal to 100 μm. The thickness may be greater than 10 μm, greater than or equal to 12 μm, or greater than or equal to 15 μm, or may be less than or equal to 100 μm, less than or equal to 90 μm, less than or equal to 80 μm, less than or equal to 70 μm, less than or equal to 60 μm, less than or equal to 50 μm, less than or equal to 45 μm, less than or equal to 40 μm, less than or equal to 35 μm, less than or equal to 30 μm, less than or equal to 25 μm, or less than or equal to 23 μm.

[0065] (Polyethylene Resin) As the polyethylene resin, the polyethylene resins described in relation to the inorganic particle-containing layer can be used.

[0066] The content of the polyethylene resin may be 5% by mass or more and 45% by mass or less, relative to the mass of the sealant layer. This content may be 5% by mass or more, or 7% by mass or more, and may be 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 22% by mass or less.

[0067] (Polypropylene-based resin) Examples of polypropylene-based resins that can be used include polypropylene (PP) homopolymer, random polypropylene (random PP), block polypropylene (block PP), chlorinated polypropylene, acid-modified polypropylene, and derivatives thereof, as well as mixtures thereof.

[0068] Among these, it is preferable to use random PP and / or block PP as the polypropylene-based resin from the viewpoint of suppressing exposure of inorganic particles when opening the package. Without wishing to be bound by theory, it is thought that this is because the monomers other than the propylene monomer that constitute these polypropylene-based resins contribute to improving the adhesive strength between the inorganic particle-containing layer and the sealant layer.

[0069] From the viewpoint of adhesiveness, the content of the polypropylene resin is preferably 35% by mass or more and 85% by mass or less, relative to the mass of the sealant layer, and may be 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, or 55% by mass or more, and may be 85% by mass or less, 80% by mass or less, or 75% by mass or less.

[0070] The ratio of the mass of the polypropylene-based resin to the mass of the polyethylene-based resin in the sealant layer may be, for example, 0.5 or more and 8.0 or less. This ratio may be 0.5 or more, 0.6 or more, 0.8 or more, 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, or 2.7 or more, and may be 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.3 or less.

[0071] The density of polypropylene resin is 0.880 g / cm ３ 0.920g / cm or more ３or less, for example 0.880 g / cm ３ Above, 0.885g / cm ３ Above, 0.890g / cm ３ or more, or 0.895 g / cm ３ or more, and 0.920 g / cm ３ Below, 0.915g / cm ３ Below, 0.910g / cm ３ or less, or 0.905 g / cm ３ It may be the following:

[0072] The melting point of the polypropylene-based resin may be 120°C or higher and 180°C or lower, for example, 120°C or higher, 130°C or higher, 135°C or higher, 140°C or higher, 145°C or higher, 150°C or higher, or 155°C or higher, and may be 180°C or lower, 175°C or lower, 170°C or lower, or 165°C or lower.

[0073] (Compatibilizer) As the compatibilizer, for example, an α-olefin copolymer is preferably used from the viewpoint of compatibilizing the polyethylene-based resin and the polypropylene-based resin, since the repeating units of the α-olefin group contained therein contain a mixture of a portion that imparts affinity to the polyethylene-based resin and a portion that imparts affinity to the polypropylene-based resin.

[0074] The content of the compatibilizer may be 5% by weight or more and 45% by weight or less, based on the weight of the sealant layer. This content may be 5% by weight or more, 7% by weight or more, 10% by weight or more, 15% by weight or more, or 18% by weight or more, and may be 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, or 22% by weight or less.

[0075] The ratio of the mass of the compatibilizer to the mass of the polyethylene resin in the sealant layer may be, for example, 0.3 or more and 5.0 or less. This ratio may be 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.8 or more, or 1.0 or more, or may be 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less. In particular, a ratio of 1.0 or more is preferred from the viewpoint of suppressing iron residue.

[0076] <Skin Layer> The skin layer may be made of a polyolefin resin, such as the polyolefin resins listed for the inorganic particle-containing layer, particularly polyethylene resins.

[0077] The thickness of the skin layer may be greater than 10 μm and less than or equal to 100 μm. The thickness may be greater than 10 μm, greater than or equal to 12 μm, or greater than or equal to 15 μm, or may be less than or equal to 100 μm, less than or equal to 90 μm, less than or equal to 80 μm, less than or equal to 70 μm, less than or equal to 60 μm, less than or equal to 50 μm, less than or equal to 45 μm, less than or equal to 40 μm, less than or equal to 35 μm, less than or equal to 30 μm, less than or equal to 25 μm, or less than or equal to 23 μm.

[0078] <<Container with Lid>> As shown in Figures 2(a) and (b), the container with lid 300 of the present invention comprises a container 200 having a flange portion 202 and a storage portion 204, and the above-mentioned easy-open lid material 100 that is heat-sealed at the flange portion 202 of the container 200, thereby hermetically sealing the container 200, and the surface of the container that is heat-sealed to the easy-open lid material is made of a polypropylene-based resin.

[0079] The above-mentioned easy-open lid material may have a tab 110 that can be grasped and pulled up when opening.

[0080] The lidded container of the present invention may be a lidded container containing a content, which has a content accommodated in the accommodation portion of the lidded container.

[0081] <Container> The container has a flange and a storage portion. The surface of the container that is heat-sealed to the easy-open lid is made of a polypropylene resin.

[0082] The container is not particularly limited as long as the easily openable lid can be heat-sealed. For example, a paper container whose surface is coated with a polypropylene resin, or a polypropylene resin container can be used.

[0083] (Flange) The flange is a peripheral portion of the container housing, and may be a brim-shaped portion. The shape of the outer periphery of the flange can be selected depending on the shape of the lid.

[0084] (Storage section) The storage section is the section in which the contents are stored. The shape of this section can be, for example, a substantially rounded truncated pyramid, a substantially truncated cone, a truncated polygonal pyramid, a rectangular parallelepiped, a cube, or the like.

[0085] The contents are contained in the container. Examples of such contents include room temperature microwaveable foods such as soup, instant noodles, and cooked rice, microwaveable foods such as chilled foods and frozen foods, and non-heatable foods such as snacks and gummy candies.

[0086] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0087] <<Preparation of Lidded Containers>> <Example 1>> A multilayer film consisting of a 20 μm thick skin layer, a 30 μm thick inorganic particle-containing layer, and a 20 μm thick sealant layer was produced using an inflation film-forming machine. The skin layer was made of linear low-density polyethylene (LLDPE1, density 0.925 g / cm ３ The inorganic particle-containing layer was made of a polyethylene masterbatch containing 60% by mass of iron powder (iron powder MB, density 2.76 g / cm). ３ A 50:50 blend of block polypropylene (block PP, density 0.900 g / cm3) and LLDPE1 (melting point 109°C) was used as the sealant layer. ３ , melting point 160 ° C) and low-density polyethylene (LDPE, density 0.920 g / cm ３ , melting point 107°C) and a compatibilizer (α-olefin copolymer, density 0.885 g / cm ３ , melting point 66°C) in a mass ratio of 70:10:20 was used.

[0088] Next, a biaxially oriented nylon film (thickness 15 μm) was dry laminated to the aluminum vapor deposition layer side of the aluminum vapor deposition polyethylene terephthalate (thickness 12 μm), and the skin layer side of the prepared multilayer film was dry laminated to the other side of this biaxially oriented nylon film to obtain the lid material laminate of Example 1.

[0089] Examples 2 to 11 and Comparative Examples 1 to 4 Lidding laminates of Examples 2 to 11 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that the type and content of each component was changed as shown in Tables 1 and 2. Details of each component shown in Tables 1 and 2 are as follows: LLDPE2: Linear low-density polyethylene, density 0.903 g / cm ３ , melting point 98 ° C. Random PP: random polypropylene, density 0.900 g / cm ３ , melting point 132 ° C. Homo PP: homo polypropylene, density 0.900 g / cm ３ , melting point 159 ° C. Modified PO: acid-modified polyolefin, density 0.907 g / cm ３ , melting point 118 ° C. EP resin: commercially available easy-peel resin film, density 0.85 to 1.05 g / cm ３

[0090] <Evaluation> The obtained lid material laminate was cut to fit the size of a container to obtain a lid material, which was then heat-sealed to the flange of a polypropylene container by adjusting the heat-sealing temperature so as to obtain a sealing strength of 15 to 18 kPa to obtain a lidded container. Note that this sealing strength was obtained by using a seal tester (FKT-100, Sun Scientific Co., Ltd.) to attach a rubber seal to the bottom of the lidded container, pierce it with a needle, blow air into it, and measure the maximum pressure at the moment the sample ruptured.

[0091] <Ease of opening> The lids of the produced lidded containers were opened by hand, and the ease of opening was evaluated by sensory evaluation. The evaluation criteria are as follows: A: Opening was possible without any particular stress. B: Opening was somewhat stressful. C: Opening was very stressful.

[0092] <Iron Remaining> After opening, the state of iron powder remaining on the flange was visually confirmed. The evaluation criteria are as follows: A: No iron powder was present on the flange. B: A small amount of iron powder remained on the flange. C: A large amount of iron powder remained on the flange.

[0093] The configurations and evaluation results of the examples and comparative examples are shown in Tables 1 and 2.

[0094]

[0095]

[0096] From Tables 1 and 2, it can be seen that the easy-open lid materials of the examples, in which the sealant layer contains a polyethylene-based resin and a polypropylene-based resin, and the polyethylene-based resin and the polypropylene-based resin are compatible with each other, are able to prevent inorganic particles from remaining when opened, even when heat sealing is performed under conditions in which the inorganic particle content of the inorganic particle-containing layer is 25 mass% or more and the sealing strength is 15 to 18 kPa.

[0097] REFERENCE SIGNS LIST 100 Easy-open lid material 102 Base layer 104 Inorganic particle-containing layer 106 Sealant layer 110 Tab 200 Container 202 Flange portion 202a Flange seal portion 204 Storage portion 250 Contents

Claims

1. An easily openable lid material comprising at least a base layer, an inorganic particle-containing layer, and a sealant layer, wherein the inorganic particle-containing layer contains a polyethylene resin and inorganic particles dispersed in the polyethylene resin, the inorganic particle content is 25 mass% or more relative to the mass of the inorganic particle-containing layer, and the sealant layer contains a polyethylene resin and a polypropylene resin, and the polyethylene resin and the polypropylene resin are compatible with each other.

2. The easy-open lid material according to claim 1, wherein the polypropylene resin is block polypropylene and / or random polypropylene.

3. The easy-open lid material according to claim 1 or 2, wherein the inorganic particles are an oxygen absorber and the substrate layer is a barrier substrate layer.

4. The easy-open lid material according to claim 3, wherein the oxygen absorber is iron powder.

5. The easy-open lid material according to claim 3, wherein the barrier substrate layer is composed of a substrate resin layer and a barrier layer.

6. The easy-open lid material according to claim 5, wherein the barrier layer is an inorganic vapor deposition film or an organic coating film.

7. The easy-open lid material according to any one of claims 1 to 6, wherein the inorganic particle-containing layer has a skin layer on the surface facing the base material layer.

8. The easy-open lid material according to claim 7, wherein the skin layer, the inorganic particle-containing layer, and the sealant layer are fused together.

9. The easy-open lid material according to claim 8, wherein the skin layer, the inorganic particle-containing layer, and the sealant layer are a three-layer inflation film.

10. A lidded container comprising a container having a flange portion and a storage portion, and an easy-open lid material according to any one of claims 1 to 9 heat-sealed to the flange portion of the container, wherein the surface of the container that is heat-sealed to the easy-open lid material is made of a polypropylene-based resin.

11. A lidded container containing a content, the content being contained in the container storage section of the lidded container according to claim 10.

12. The container with lid containing the contents according to claim 11, wherein the contents is cooked rice.

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