Food packaging sheets, easy-open packaging

Abstract

The present invention provides a food packaging sheet having an easily openable resin layer containing a polypropylene resin, which, when used as a packaging material, exhibits good crackability and easy opening properties. [Solution] A food packaging sheet having an easily openable resin layer (I) containing a polypropylene resin (A) and a petroleum resin tackifier (B), The tensile modulus of the aforementioned easily openable resin layer (I), measured in accordance with JIS K7127 (1999), was 2.2 × 10⁻⁶. 9 Food packaging sheets with a Pa rating of 1.5 or higher.

Description

[Technical Field]

[0001] The present invention relates to a food packaging sheet, and more specifically, to a food packaging sheet that exhibits excellent crackability and openability when used as a package. [Background technology]

[0002] Traditionally, plastic sheets have been used as packaging for various contents, including liquids, solids, and powders. The aforementioned plastic sheets are used by layering them to provide moldability, rigidity, barrier properties, sealing properties, etc., depending on the required performance. Furthermore, the packaging forms are diverse, including deep-draw packaging, skin pack packaging, pouch packaging, and blister packaging. In these packaging forms, providing easy opening for removing the contents is also an important challenge. As a method for providing the aforementioned easy-open properties, for example, when the contents are packaged by heat-sealing the bottom material and lid material and then the seal is peeled off to open the package, a method of blending an incompatible resin into the seal layer is known (see, for example, Patent Document 1). Furthermore, in cup containers (such as those for jelly or milk portions), a notch is provided for opening, and the contents can be removed by bending and breaking at the notch. Styrene-based resins are used for packaging containers with such opening notches (including half-cuts) to provide breakability (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-146636 [Patent Document 2] International Publication No. 2015 / 012012 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, from an environmental perspective, there has been a demand to convert multilayer sheets into monomaterials to improve recyclability and other aspects. However, the packaging materials described in Patent Documents 1 and 2 contain a mixture of polyolefin resins and other resins, and therefore are not monomaterial and have poor recyclability.

[0005] The present invention aims to provide a food packaging sheet having an easily openable resin layer containing a polypropylene resin, which, when used as a packaging material, exhibits good crackability and easy opening properties. [Means for solving the problem]

[0006] As a result of diligent research to solve the aforementioned problems, the inventors have found that the aforementioned problems can be solved by providing a sheet having an easily detachable resin layer containing a polypropylene resin and a petroleum resin tackifier, wherein the tensile modulus of elasticity is within a specific range, and have completed the present invention.

[0007] In other words, the present invention has the following aspects. [1] A food packaging sheet having an easy-open resin layer (I) containing a polypropylene resin (A) and a petroleum resin tackifier (B), The tensile modulus of the aforementioned easily openable resin layer (I), measured in accordance with JIS K7127 (1999), was 2.2 × 10⁻⁶. 9 Food packaging sheets with a Pa rating of 1.5 or higher. [2] The food packaging sheet according to [1], wherein the polypropylene resin (A) is homopolypropylene. [3] A food packaging sheet according to [1] or [2], further comprising a barrier layer (II). [4] The food packaging sheet according to [3], wherein the barrier layer (II) comprises an ethylene-vinyl alcohol resin as the main component. [5] A food packaging sheet according to [3] or [4], having an outer layer (III) on the outermost layer side of the barrier layer (II). [6] The food packaging sheet according to [5], wherein the outer layer (III) contains a polyolefin resin as a main component. [7] The food packaging sheet according to any one of [3] to [6], wherein the ratio of the thickness of the barrier layer (II) to the total thickness of the food packaging sheet is 0.5 to 15%. [8] The oxygen transmission rate measured in accordance with JIS K7126-1 (2006) is 10.0 cc / m 2 ·24 hr or less, and the food packaging sheet according to any one of [3] to [7]. [9] The food packaging sheet according to any one of [1] to [8], which is provided with a half cut or a notch.

[10] The food packaging sheet according to any one of [3] to [8], wherein the half cut or the notch is provided from the side of the easy-opening resin layer (I).

[11] An easy-opening package using the food packaging sheet according to any one of [1] to

[10] .

Advantages of the Invention

[0008] The food packaging sheet of the present invention has good cracking properties and easy-opening properties when used as a package.

Modes for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described based on examples of modes for carrying out the present invention. However, the present invention is not limited to the embodiments described below.

[0010] In this specification, "x and / or y (x and y are arbitrary components)" means at least one of x and y, and means three cases: only x, only y, and x and y. In this specification, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it means "X or more and Y or less", and also includes the meaning of "preferably larger than X" or "preferably smaller than Y". In this specification, when we use the expressions "X or greater" (where X is any number) or "Y or less" (where Y is any number), we also mean "preferably greater than X" or "preferably less than Y." In this specification, the numerical ranges described in stages may be arbitrarily combined with the upper or lower limits of the numerical ranges in any stage. Furthermore, in the numerical ranges described herein, the upper or lower limits may be replaced with the values ​​shown in the examples.

[0011] In this specification, "sheet" includes "film" and "tape." In this specification, "(meth)acrylic" means acrylic and / or methacrylic. In this specification, "main component" means a component that has a significant effect on the properties of the object, and the content of the component is usually 50% by mass or more in the object, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0012] A food packaging sheet according to one embodiment of the present invention (hereinafter referred to as "the sheet") has an easy-open resin layer (I). Furthermore, it is preferable that the sheet has a barrier layer (II) and a sealing layer (III) in addition to the easy-open resin layer (I). This sheet can be suitably used as a bottom material or lid material for packaging, and is particularly suitable for use as a lid material. The following describes each layer of this sheet.

[0013] <Easy-to-open resin layer (I)> The aforementioned easily detachable resin layer (I) contains a polypropylene resin (A) and a petroleum resin tackifier (B).

[0014] [Polypropylene resin (A)] The polypropylene resin (A) is not particularly limited as long as it is a resin in which propylene is the main monomer component. For example, it may be a homopolymer of propylene [homopolypropylene (hPP)] or a copolymer of propylene and another copolymerizable monomer component. Furthermore, the polypropylene resin may be used alone, or two or more types with different copolymerizable monomer components, compositions, and physical properties may be used in combination. In this specification, "main monomer component" refers to the monomer component that accounts for 50 to 100% by mass in the resin.

[0015] There are no particular restrictions on the polymerization method of the polypropylene resin (A), and it can be carried out by conventionally known methods. Similarly, there are no particular restrictions on the catalyst used for polymerization, and conventionally known catalysts can be used.

[0016] Examples of the other copolymerizable monomer components include ethylene, α-olefins having 2 to 20 carbon atoms excluding propylene, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, dienes such as 1,4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, and ethylidene norbornene, divinylbenzene, vinyl acetate, (meth)acrylic acid, (meth)acrylic acid esters, glycidyl (meth)acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, and cyclic olefins. These can be used individually or in combination of two or more. That is, the polypropylene resin may be a polypolymer containing two or more of the other copolymerizable monomer components. Among these, α-olefins having 2 to 20 carbon atoms are preferred, more preferably α-olefins having 2 to 8 carbon atoms, and particularly preferably ethylene.

[0017] The content of the other copolymerizable monomer components is usually 0.5% by mass or more, preferably 1.0% by mass or more, and more preferably 1.5% by mass or more, based on the total mass of the polypropylene resin. Furthermore, the content of the other copolymerizable monomer components is usually 40% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less, based on the total mass of the polypropylene resin.

[0018] Furthermore, if the polypropylene resin is a copolymer, the polypropylene resin may be a block copolymer, a random copolymer, or a graft copolymer.

[0019] As the polypropylene resin (A), it is preferable to use a resin with high rigidity in order to provide good ease of opening. For this reason, the polypropylene resin (A) preferably contains homopolypropylene, more preferably contains homopolypropylene as the main component, and is particularly preferably homopolypropylene.

[0020] The melt flow rate (hereinafter also referred to as "MFR") of the polypropylene resin (A), measured in accordance with JIS K7210 (2014) (230°C, load 2.16 kg), is preferably 0.3 g / 10 min or more, more preferably 0.5 g / 10 min or more, and even more preferably 0.8 g / 10 min or more. Furthermore, the melt flow rate is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less. The range of the MFR is, for example, 0.3 to 30 g / 10 min. If the MFR of the polypropylene resin (A) is within the above range, stable film formation is more easily obtained.

[0021] The density of the aforementioned polypropylene resin (A), measured in accordance with JIS K7112 (1999), is 0.850 to 0.950 g / cm³. 3 Preferably, it is 0.870 to 0.930 g / cm³. 3 More preferably 0.890 to 0.910 g / cm³3 By setting the density of the polypropylene resin (A) within the aforementioned range, the ease of opening tends to be excellent.

[0022] The number-average molecular weight (Mn) of the polypropylene resin (A) is preferably 30,000 or more, and more preferably 50,000 or more. While there is no particular upper limit to the number-average molecular weight (Mn) of the polypropylene resin (A), from the viewpoint of extrusion moldability, it is preferably 200,000 or less, and more preferably 150,000 or less. The range of the number-average molecular weight is, for example, 30,000 to 200,000. By setting the number-average molecular weight (Mn) of the polypropylene resin (A) within this range, stable film formation tends to be more easily achieved.

[0023] The weight-average molecular weight (Mw) of the polypropylene resin (A) is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. Furthermore, the weight-average molecular weight (Mw) of the polypropylene resin (A) is preferably 1,500,000 or less, and more preferably 1,000,000 or less. The range of the weight-average molecular weight is, for example, 200,000 to 1,500,000. By setting the weight-average molecular weight (Mw) of the polypropylene resin (A) within the above range, there is a tendency for excellent film-forming properties.

[0024] The molecular weight distribution (Mw / Mn) calculated from the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polypropylene resin is preferably 3.5 or higher, more preferably 4.0 or higher, and even more preferably 4.5 or higher. Furthermore, the molecular weight distribution (Mw / Mn) is preferably 20 or lower, and more preferably 15 or lower. The range of the molecular weight distribution is, for example, 3.5 to 20. Setting the molecular weight distribution (Mw / Mn) above the lower limit tends to improve the moldability of the film. Furthermore, setting the molecular weight distribution (Mw / Mn) below the upper limit can suppress the presence of extremely low molecular weight components, which tends to suppress bleeding of extremely low molecular weight components and prevent extremely high molecular weight components from becoming unmelted during molding.

[0025] The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the aforementioned polypropylene resin (A) can be calculated by measuring them using a high-temperature GPC system from Malvern Instruments (Viscotek Triple Detector HT-GPC Model SG system), with a detector: RI (reference flow method), using orthodichlorobenzene as the solvent, and measuring at a temperature of 140°C, and then converting them to polystyrene equivalents.

[0026] The content of the polypropylene resin (A) in the easily openable resin layer (I) is usually 50% by mass or more, preferably 65% ​​by mass or more, more preferably 70% by mass or more, and particularly preferably 75% by mass or more. The upper limit is usually 95% by mass or less, preferably 90% by mass or less, and particularly preferably 85% by mass or less. The range of the content is, for example, 50 to 95% by mass.

[0027] [Petroleum resin-based tackifier (B)] The aforementioned easily detachable resin layer (I) contains a petroleum resin-based tackifier (B). This sheet has improved crackability and ease of opening due to the inclusion of a petroleum resin-based tackifier (B) in the easily openable resin layer (I). The reason for these effects is presumed to be that the petroleum resin-based tackifier (B) is compatible with the aforementioned polypropylene resin (A), and the petroleum resin-based tackifier (B) penetrates the amorphous portion of the polypropylene resin (A), reducing the mobility of the amorphous portion, which in turn embrittles the easily detachable resin layer (I), thereby improving crackability and detachability.

[0028] The petroleum resin-based tackifier (B) is not particularly limited as long as it is an amorphous resin, and examples include hydrocarbon resins such as aromatic hydrocarbon resins (C9 hydrocarbon resins), aliphatic hydrocarbon resins (C5 hydrocarbon resins), aliphatic-aromatic hydrocarbon resins (C5-C9 hydrocarbon resins), unsaturated hydrocarbon copolymers, and hydrogenated derivatives of these resins (e.g., alicyclic hydrocarbon resins, aliphatic-alicyclic hydrocarbon resins, etc.); phenolic resins such as phenol-formaldehyde resins and xylene-formaldehyde resins; and chroman resins such as chroman-indene resins. One or more of these can be used in combination.

[0029] In particular, the hydrogenated derivative exhibits good compatibility with polypropylene resin (A) and is preferred from the viewpoint of further improving color tone, thermal stability, barrier properties, etc. The hydrogenated derivative is preferably one in which the hydrogenation rate is 95% or more and which is substantially free of polar groups such as hydroxyl groups, carboxyl groups, halogens, or unsaturated bonds such as double bonds. "Substantially free" means that the content of unsaturated bonds is 3% or less, preferably 1% or less, relative to the hydrogenated derivative.

[0030] The petroleum-based tackifier (B) is preferably at least one selected from the group consisting of aromatic hydrocarbon resins (C9 hydrocarbon resins), aliphatic hydrocarbon resins (C5 hydrocarbon resins), aliphatic-aromatic hydrocarbon resins (C5-C9 hydrocarbon resins), and hydrogenated derivatives thereof, from the viewpoint of improving crackability and ease of opening, and is particularly preferably a hydrogenated derivative of aromatic hydrocarbon resins (C9 hydrocarbon resins) (alicyclic hydrocarbon resins).

[0031] The weight-average molecular weight of the petroleum resin-based tackifier (B) is not particularly limited, but is usually 1,000 to 30,000, and preferably 3,000 to 15,000.

[0032] The softening point of the petroleum resin-based tackifier (B) is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. Furthermore, the softening point of the petroleum resin-based tackifier (B) is preferably 150°C or lower. The range of the softening point is, for example, 80 to 150°C. When the softening point of the petroleum resin-based tackifier (B) is within the above range, its compatibility with the polypropylene resin (A) increases, and it tends to have excellent openability. Also, when the softening point of the petroleum resin-based tackifier (B) is within the above range, it is possible to prevent the raw materials from blocking during the formation of the easily openable resin layer (I), which tends to result in good productivity.

[0033] Commercially available petroleum resin-based tackifiers (B) can also be used. Examples of commercially available products include the "Alcon" series manufactured by Arakawa Chemical Industries, Ltd., the "iMarb" series manufactured by Idemitsu Kosan Co., Ltd., and the "Hi-Lets" series and "Petrozine" series manufactured by Mitsui Chemicals, Inc.

[0034] The content of the petroleum resin-based tackifier (B) in the easy-open resin layer (I) is preferably 2 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 8 to 25% by mass. Setting the content of the petroleum resin-based tackifier (B) above the lower limit tends to make the easy-open resin layer (I) moderately brittle and improve its openability, while setting it below the upper limit tends to make the easy-open resin layer (I) sufficiently strong for practical use, and also improves the film-forming properties of the easy-open resin layer (I) and improves productivity.

[0035] [Nuclear agent] The easily detachable resin layer (I) preferably contains a nucleating agent in addition to the polypropylene resin (A) and petroleum resin tackifier (B). By including a nucleating agent in the easy-open resin layer (I), the crystallinity of the polypropylene resin (A) can be controlled, and the crackability and ease of opening of the easy-open resin layer (I) can be effectively improved. Furthermore, the inclusion of a nucleating agent in the easily detachable resin layer (I) improves transparency, making it easier to use in applications where the visibility of the contents is required.

[0036] Examples of the nucleating agents include fatty acid metal salts, phosphates, aromatic phosphonates, polyhydric alcohols, fatty acid amides, copolymers of olefins and maleic acid, metal salts of carboxylic acids, and triaminobenzene derivatives. These nucleating agents can be used individually or in combination of two or more.

[0037] Examples of the fatty acid metal salts include lithium stearate, barium stearate, zinc stearate, sodium stearate, calcium stearate, magnesium stearate, aluminum stearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, magnesium 12-hydroxystearate, aluminum 12-hydroxystearate, barium 12-hydroxystearate, lithium 12-hydroxystearate, sodium 12-hydroxystearate, sodium montana, calcium montana, lithium montana, zinc montana, magnesium montana, aluminum montana, calcium laurate, barium laurate, zinc laurate, lithium laurate, sodium laurate, calcium ricinoleate, barium ricinoleate, zinc ricinoleate, potassium caprylate, sodium caprylate, calcium caprylate, magnesium caprylate, aluminum octoate, zinc myristate, zinc palmitate, and sodium dimethyl sulfoisophthalate.

[0038] Examples of the phosphate salts include inorganic phosphates such as sodium phosphate, potassium phosphate, calcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, iron phosphate, and ammonium phosphate, as well as aromatic phosphate esters such as sodium 2,2'-methylenebis(4,6-di-t-butylphenyl) phosphate, aluminum 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, and lithium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.

[0039] Examples of the aromatic phosphonate include zinc phenylphosphonate, a composition containing the sodium salt of 2-hydroxy-2-oxo-4,6,10,12-tetra-tert-butyl-1,3,2-dibenzo[d,g]perhydrodioxaphosphalosine, and aluminum=bis(4,4',6,6'-tetra-tert-butyl-2,2'-methylenediphenyl=phosphate)=hydroxyl.

[0040] Examples of the aforementioned polyhydric alcohols include sorbitol compounds such as dibenzylidene sorbitol, 1,3,2,4-di-(methylbenzylidene) sorbitol, 1,3,2,4-(ethylbenzylidene) sorbitol, 1,3,2,4-(methoxybenzylidene) sorbitol, 1,3,2,4-(ethoxybenzylidene) sorbitol, and 1,2,3-trideoxy-4,6-5,7-bis-o-[(4-propylphenyl)methylene]nonitol, as well as trimethylolpropane, inositol, and pentaerythritol.

[0041] Examples of the aforementioned fatty acid amides include N-stearyloleamide, N-stearylerucamide, N-oleylstearateamide, laurateamide, N-stearylstearateamide, palmitamide, stearamide, hydroxystearamide, N-methylolstearateamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, ethylenebisoleamide, ethylenebiserucamide, hexamethylenebishydroxystearamide, hexamethylenebisstearateamide, N,N'-distearyladipamide, methylenebisstearateamide, hexamethylenebisbehenamide, ethylenebisstearateamide, ethylenebishydroxystearamide, ethylenebislaurateamide, ethylenebiscaprateamide, erucamide, and the like.

[0042] Examples of copolymers of olefin and maleic acid include copolymers of olefin and maleic anhydride, as well as copolymers of styrene and maleic anhydride.

[0043] Examples of metal salts of the carboxylic acid include sodium adipate, potassium adipate, aluminum adipate, sodium sebacate, potassium sebacate, aluminum sebacate, sodium benzoate, aluminum benzoate, di-para-t-butylaluminum benzoate, di-para-t-butyltitanium benzoate, di-para-t-butylchromium benzoate, and hydroxy-di-t-butylaluminum benzoate.

[0044] Examples of the triaminobenzene derivative include 1,3,5-tris(2,2-dimethylpropanamide)benzene.

[0045] As the nucleating agent, fatty acid metal salts, polyhydric alcohols, and triaminobenzene derivatives are preferred, more preferably higher fatty acid magnesium salts having 10 or more carbon atoms, 1,3,5-tris(2,2-dimethylpropanamide)benzene, and particularly preferably magnesium stearate and 1,3,5-tris(2,2-dimethylpropanamide)benzene, as these allow for better control of the crystallinity of the polypropylene resin (A) and more effectively enhance the crackability and openability of the easily tamper-evident resin layer (I).

[0046] Commercially available products can also be used as the nucleating agent. Examples of commercially available products include the nucleating agent masterbatch "Rikemaster FC-2" manufactured by Riken Vitamin Co., Ltd., and the nucleating agent masterbatch "Clearmaster R200" manufactured by Dainichi Seika Kogyo Co., Ltd.

[0047] The nucleating agent content in the easily openable resin layer (I) is preferably 0.010% by mass or more, more preferably 0.015% by mass or more. Furthermore, the nucleating agent content in the easily openable resin layer (I) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The range of the content is, for example, 0.010 to 20% by mass. By setting the nucleating agent content within the above range, it tends to be possible to further improve crackability and openability by imparting rigidity.

[0048] [Thermoplastic resin] The easily openable resin layer (I) may contain polyolefin resins other than the polypropylene resin (for example, polyethylene resins, α-olefin copolymers, cyclic polyolefin resins, modified polyolefin resins, etc.), as well as thermoplastic resins such as ethylene-vinyl alcohol resins (hereinafter referred to as "EVOH") and polyamide resins, in an amount that does not impede the effects of the present invention [for example, 10% by mass or less, preferably 5% by mass or less of the easily openable resin layer (I)].

[0049] [Additives] The easy-open resin layer (I) may contain additives such as tackifiers other than petroleum resin-based tackifiers (B) (e.g., rosin-based resins, terpene-based resins, etc.), heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, antibacterial / antifungal agents, antistatic agents, lubricants, etc., in an amount that does not impair the effects of the present invention [for example, 30% or less by mass of the easy-open resin layer (I), preferably 10% or less by mass]. These may be used individually or in combination of two or more.

[0050] The thickness of the easily detachable resin layer (I) is preferably 10 to 1,000 μm, more preferably 20 to 800 μm, more preferably 30 to 500 μm, and particularly preferably 50 to 350 μm. Setting the thickness of the easily detachable resin layer (I) within this range tends to result in good crackability.

[0051] <Barrier layer (II)> The sheet preferably has a barrier layer (II) in addition to the easy-open resin layer (I). That is, the sheet preferably has at least an easy-open resin layer (I) and a barrier layer (II).

[0052] The aforementioned barrier layer (II) is a layer that exhibits gas barrier properties such as oxygen barrier properties and water vapor barrier properties. From the viewpoint of exhibiting the gas barrier properties described above, the barrier layer (II) is preferably a layer mainly composed of a polyamide resin and / or EVOH, and from the viewpoint of monomaterialization, it is more preferably a layer mainly composed of EVOH.

[0053] If the sheet has a barrier layer (II), the barrier layer (II) may be a single layer or consist of two or more layers. For example, the barrier layer (II) may be a single layer mainly composed of polyamide resin and / or EVOH, or it may be two or more layers mainly composed of polyamide resin and / or EVOH.

[0054] [Polyamide resin] When the barrier layer (II) contains a polyamide resin, the barrier properties and pinhole resistance of the sheet can be improved, making the sheet particularly suitable for deep drawing applications. Examples of the polyamide resins include polyamide 4, polyamide 6, polyamide 7, polyamide 11, polyamide 12, polyamide 46, polyamide 66, polyamide 69, polyamide 610, polyamide 611, polyamide 6T, polyamide 6I, polyamide MXD6, polyamide 6-66, polyamide 6-610, polyamide 6-611, polyamide 6-12, polyamide 6-612, polyamide 6-6T, polyamide 6-6I, polyamide 6-66-610, polyamide 6-66-12, polyamide 6-66-612, polyamide 66-6T, polyamide 66-6I, polyamide 6T-6I, and polyamide 66-6T-6I. Among these, polyamide 6 and polyamide 6-66 are preferred from the viewpoint of pinhole resistance. Furthermore, as mentioned above, two or more barrier layers (II) may be provided, in which case each layer may be made of a different type of polyamide resin.

[0055] [EVOH] If the barrier layer (II) contains EVOH, the gas barrier properties of the sheet, such as oxygen barrier properties, can be enhanced.

[0056] The aforementioned EVOH is a thermoplastic resin obtained by saponifying a copolymer of ethylene and vinyl acetate with an alkaline catalyst or the like, and is mainly composed of vinyl alcohol structural units, having vinyl alcohol structural units corresponding to the degree of saponification and vinyl acetate structural units in the unsaponified portion.

[0057] The ethylene content in the EVOH is not particularly limited, but from the viewpoint of film formation stability, it is usually 23 mol% or more, preferably 25 mol% or more, and from the viewpoint of gas barrier properties, it is usually 47 mol% or less, preferably 44 mol% or less. The range of the ethylene content is, for example, 23 to 47 mol%. Furthermore, the degree of saponification of EVOH is preferably 90 mol% or higher from the viewpoint of thermal stability, preferably 95% or higher, and more preferably 99 mol% or higher from the viewpoint of gas barrier properties. Maintaining the ethylene content and degree of saponification in EVOH within the aforementioned range tends to maintain good gas barrier properties. Note that EVOH is not limited to those produced by saponification, as long as its chemical structure is similar.

[0058] The melting point of the aforementioned EVOH is not particularly limited, but from the viewpoint of deep-drawn formability, it is usually 150 to 210°C, preferably 152 to 205°C, and more preferably 155 to 200°C.

[0059] The MFR (at 210°C, with a load of 2.16 kg) of the aforementioned EVOH is not particularly limited, but from the viewpoint of film formation properties, it is preferably 0.1 to 80 g / 10 min, more preferably 0.5 to 50 g / 10 min, and more preferably 1.0 to 25 g / 10 min.

[0060] [Thermoplastic resin] The barrier layer (II) may contain thermoplastic resins other than the polyamide resin and EVOH (for example, polyethylene resins, polypropylene resins, α-olefin copolymers, cyclic polyolefin resins, modified polyolefin resins, and other polyolefin resins) in an amount that does not impair the effects of the present invention [for example, 10% by mass or less of the barrier layer (II), preferably 5% by mass or less]. One or more of these can be used in combination.

[0061] [Additives] Furthermore, the barrier layer (II) may contain, as appropriate, the additives described for the easily detachable resin layer (I) in an amount that does not significantly impair the effects of the present invention [for example, 10% by mass or less of the barrier layer (II), preferably 5% by mass or less], for the purpose of improving and adjusting various properties such as moldability and productivity. These can be used individually or in combination of two or more types.

[0062] The thickness (single layer) of the barrier layer (II) is usually 5 to 50 μm, preferably 7 to 40 μm or more, and more preferably 10 to 35 μm. If the thickness of the barrier layer (II) is greater than or equal to the above values, good gas barrier properties tend to be obtained, and if the thickness is less than or equal to the above values, moldability tends to be good.

[0063] Furthermore, the ratio of the thickness of the barrier layer (II) to the total thickness of the sheet (if there are two or more barrier layers (II), the sum of the thicknesses of all barrier layers (II)) is preferably 0.5 to 15%, more preferably 1.0 to 12%, and even more preferably 1.0 to 10%. When the ratio of the barrier layer (II) thickness is within the above range, the sheet tends to have excellent gas barrier properties and ease of opening.

[0064] <Outer layer (III)> This sheet preferably has an outer layer (III) as its outermost layer. The aforementioned outer layer (III) is a layer that can also function as a sealing layer. Therefore, when using this sheet as packaging, the outer layer (III) can be heat-sealed in contact with the mating material. In particular, in this sheet, it is preferable to have an outer layer (III) on the outermost layer side of the barrier layer (II).

[0065] From the viewpoint of heat sealability, the outer layer (III) is preferably composed mainly of a polyolefin resin.

[0066] [Polyolefin resins] Examples of the polyolefin resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), polypropylene resins (PP), ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ionomer resins, ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of 8 to 40 mol%, hot melt resins (HM), and resins obtained by modifying these polyolefin resins with unsaturated carboxylic acids or their derivatives. These polyolefin resins are appropriately selected according to the shape of the molded article and the shape and type of the contents. Furthermore, these polyolefin resins may be used alone or blended in known formulations to impart easy-peel properties. Known formulations for imparting the aforementioned easy-peel properties include, for example, a mixture of low-density polyethylene and polybutene resin.

[0067] Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and their esters and anhydrides. These may be used individually or in combination of two or more.

[0068] Furthermore, examples of derivatives of the unsaturated carboxylic acid include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylamide, sodium (meth)acrylate, and derivatives to which vinyl acetate or the like has been added. These may be used individually or in combination of two or more.

[0069] The aforementioned polyolefin resin is selected as appropriate according to the shape of the packaging and the shape and type of the contents.

[0070] The melting point of the polyolefin resin is preferably 80 to 175°C, more preferably 90 to 170°C, and even more preferably 100 to 168°C. By having the melting point of the polyolefin resin within the aforementioned range, superior heat-sealing properties can be provided.

[0071] [Thermoplastic resin] The outer layer (III) may contain a thermoplastic resin such as a polyamide resin or EVOH in an amount that does not impede the effects of the present invention [for example, 10% by mass or less of the outer layer (III), preferably 5% by mass or less].

[0072] [Additives] The outer layer (III) may contain, as appropriate, the additives described in the description of the easily openable resin layer (I) in an amount that does not significantly impede the effects of the present invention [for example, 10% by mass or less of the outer layer (III), preferably 5% by mass or less], for the purpose of improving and adjusting various properties such as moldability and productivity. These can be used individually or in combination of two or more.

[0073] The thickness (single layer) of the outer layer (III) is preferably 1 to 100 μm, more preferably 2 to 80 μm, and even more preferably 5 to 60 μm. Setting the thickness of the outer layer (III) within this range tends to provide film formation stability and sufficient sealing performance.

[0074] In addition to layers (I) to (III) mentioned above, this sheet may also have other layers, such as an intermediate layer, a base layer, an adhesive layer, etc. Furthermore, this sheet may have two or more of these intermediate layers, adhesive layers, etc.

[0075] <Middle class> The aforementioned intermediate layer is excluding layers (I) to (III) and is placed between the sheets to improve film strength, heat resistance, and thickness. It is not particularly limited, but from a monomaterial viewpoint, it is preferable to contain a polyolefin resin as the main component.

[0076] [Polyolefin resins] As the polyolefin resin, the polyolefin resin described in the outer layer (III) may be used. The polyolefin resin may be used alone or in combination of two or more types. Furthermore, the polyolefin resin used in the intermediate layer may be the same as or different from the polyolefin resin used in the outer layer (III).

[0077] [Thermoplastic resin] The intermediate layer may contain, for example, thermoplastic resins such as EVOH or polyamide resins, in a range that does not hinder the effects of the present invention (for example, 10% by mass or less of the resin composition, preferably 5% by mass or less).

[0078] [Additives] The aforementioned intermediate layer may contain, as appropriate, the additives described in the section on the easily detachable resin layer (I) for the purpose of improving and adjusting various properties such as moldability and productivity, in a range that does not significantly impede the effects of the present invention [for example, 10% by mass or less of the intermediate layer, preferably 5% by mass or less]. These can be used individually or in combination of two or more types.

[0079] The thickness of the intermediate layer is typically 3 to 30 μm, preferably 4 to 25 μm, and more preferably 5 to 20 μm. Setting the thickness of the intermediate layer within this range tends to provide film formation stability. Note that the thickness of the intermediate layer is the total thickness of all intermediate layers in the sheet.

[0080] <Base material layer> The aforementioned base material layer is placed as the outermost layer of this sheet. In particular, in this sheet, it is preferable to place the base material layer on the outermost layer on the side of the easily openable resin layer (I). The aforementioned substrate layer is appropriately selected according to the application and required characteristics of the film and is not particularly limited, but it is preferable that it contains a thermoplastic resin as its main component.

[0081] [Thermoplastic resin] Examples of the thermoplastic resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), polypropylene resins (PP), ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ionomer resins, ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of 8-40 mol%, hot melt resins (HM), and unsaturated polyolefin resins. Examples include polyolefin resins in a broad sense, including resins modified with polyvinyl acid or its derivatives, cyclic olefin resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polyester resins, polyamide resins (including copolymerized polyamides), polyvinyl chloride, polyvinylidene chloride, acrylic resins, polystyrene, vinyl ester resins, polyester elastomers, polyurethane elastomers, halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, aromatic or aliphatic polyketones, or combinations thereof.

[0082] In particular, polyolefin resins are preferred from the viewpoint of monomaterials, polypropylene resins are more preferred, and homopolypropylene (hPP) is especially preferred.

[0083] Furthermore, the melting point of the thermoplastic resin is usually 140°C or higher, preferably 145°C or higher, and the upper limit of the melting point is usually 280°C or lower. When the sheet has an outer layer (III), it is preferable that the melting point of the thermoplastic resin is higher than the melting point of the resin used in the outer layer (III), as this tends to result in good heat sealability of the outer layer (III).

[0084] [Additives] The base layer may contain, as appropriate, the additives described in the section on the easily detachable resin layer (I) for the purpose of improving and adjusting various properties such as moldability and productivity, in a range that does not significantly impede the effects of the present invention [for example, 10% by mass or less of the base layer, preferably 5% by mass or less]. These can be used individually or in combination of two or more types.

[0085] The thickness of the substrate layer (single layer) is preferably 1 to 100 μm, more preferably 2 to 80 μm, and even more preferably 5 to 60 μm. Setting the thickness of the substrate layer within this range tends to provide film formation stability.

[0086] <Adhesive layer> The aforementioned adhesive layer is provided for the purpose of improving the adhesion between each layer, and mainly contains an adhesive resin.

[0087] As the adhesive resin, a resin obtained by modifying the polyolefin resin described in this sheet with the aforementioned unsaturated carboxylic acid or its derivative can be used. Furthermore, the adhesive resin may be used alone or in combination of two or more types.

[0088] [Additives] The adhesive layer may contain, as appropriate, the additives described in the section on the easily detachable resin layer (I) for the purpose of improving and adjusting various properties such as moldability and productivity, in a range that does not significantly impede the effects of the present invention [for example, 10% by mass or less, preferably 5% by mass or less, of the intermediate layer]. These can be used individually or in combination of two or more types.

[0089] The thickness of the adhesive layer is typically 3 to 30 μm, preferably 4 to 25 μm, and more preferably 5 to 20 μm. By setting the thickness of the adhesive layer within this range, film formation stability and sufficient adhesion can be provided. Note that the thickness of the adhesive layer is the total thickness of all adhesive layers present in this sheet.

[0090] [Recycled raw materials] From a recycling perspective, this sheet may contain recycled materials as raw materials for each layer, including this sheet, molded products using this sheet, scraps generated during the manufacturing process of this sheet, and other resin sheets or molded products as starting materials.

[0091] While the aforementioned other resin sheets and molded articles are not particularly limited, from the viewpoint of recyclability, resin sheets and molded articles containing polyolefin resin as the main component are preferred.

[0092] In particular, from the standpoint of recyclability and transparency, it is preferable to include the sheet, molded articles using the sheet, and recycled materials starting from scraps generated during the manufacturing process of the sheet.

[0093] Furthermore, if the sheet contains recycled materials, the recycled materials may be included in any layer, but from the viewpoint of transparency, it is preferable that they be included in at least one selected from the group consisting of the outer layer (III), the intermediate layer, and the adhesive layer. From the viewpoint of maintaining the impact resistance, moldability, sealing properties, transparency, gas barrier properties, etc., of the sheet, it is more preferable that they be included in the intermediate layer or the adhesive layer, and it is particularly preferable that they be included in the intermediate layer.

[0094] As the recycled raw material, the sheets or molded bodies can be used as they are, or they can be processed into fluff or refelletized materials. Among these, it is preferable to use them in the form of fluff or refelletized materials from the standpoint of workability.

[0095] The aforementioned "fluff" refers to a film that has been crushed, while "repellet" refers to a sheet or molded body that has been melt-kneaded and processed into a pellet shape.

[0096] When the recycled material is included in each layer, its content is usually 40% by mass or less, preferably 30% by mass or less, in each layer.

[0097] <How to manufacture this sheet> This sheet can be manufactured by preparing raw materials for forming an easily detachable resin layer (I) and using known methods, such as the extrusion inflation method or the extrusion T-die method. Furthermore, if the sheet is a laminated sheet having a barrier layer (II) or an outer layer (III), it can be manufactured by preparing the raw materials for each layer and using known methods, such as co-extrusion, extrusion lamination, or thermocompression bonding. Furthermore, this sheet may be an unstretched film or a stretched film, but it is usually unstretched.

[0098] [Layer structure of this sheet] The following is an example of the layer structure of this sheet, but this sheet is not limited to this layer structure. (1) Layer (I) / Layer (III) (2) Layer (I) / Layer (II) / Layer (III) (3) Layer (I) / Adhesive layer / Layer (II) / Adhesive layer / Layer (III) (4) Layer (I) / intermediate layer / adhesive layer / layer (II) / adhesive layer / intermediate layer / layer (III) (5) Base layer / layer (I) / intermediate layer / adhesive layer / layer (II) / adhesive layer / intermediate layer / layer (III) (6) Base layer / adhesive layer / layer (I) / intermediate layer / adhesive layer / layer (II) / adhesive layer / intermediate layer / layer (III) (7) Base layer / layer (I) / adhesive layer / layer (II) / adhesive layer / layer (III) Base layer / layer (I) / adhesive layer / layer (II) / adhesive layer / intermediate layer / layer (III) (8) Base layer / layer (I) / intermediate layer / adhesive layer / layer (II) / adhesive layer / layer (III) Furthermore, from the viewpoint of monomaterialization, it is even more preferable that all layers of this sheet contain polyolefin resin (including EVOH) as the main component.

[0099] Furthermore, if the sheet contains recycled raw materials starting from the aforementioned sheet, it can be obtained by a manufacturing method comprising the steps of producing recycled raw materials such as fluff and pellets from the starting raw materials, and obtaining the sheet from raw materials containing the recycled raw materials.

[0100] The thickness (total thickness) of this sheet is typically 20 to 1000 μm, preferably 30 to 700 μm, and more preferably 50 to 500 μm, from the viewpoint of processability, moldability, and ease of opening.

[0101] In addition to the layers described above, this sheet may also include functional layers. Examples of the functional layers include an antistatic layer, a release layer, an ultraviolet degradation prevention layer, a hydrophilic layer, an anti-fogging layer, and a moisture-proof layer. These functional layers can be provided on the sheet by coating them using a known method.

[0102] [Half cut] From the viewpoint of ease of opening, it is preferable that this sheet be provided with a half-cut. The aforementioned "half-cut" refers to a perforation line that does not penetrate the sheet completely. By adding a half-cut, when the sheet is used as packaging, it tends to tear at the half-cut portion, making it easier to open.

[0103] The aforementioned half-cut can be attached by known methods, such as using a cutter or a laser.

[0104] When the aforementioned half-cut is attached, it is preferable that it does not extend beyond the easily openable resin layer (I) of the sheet.

[0105] Furthermore, if the sheet has a barrier layer (II), it is preferable that the half-cut be attached to the side of the easily openable resin layer (I), more preferably that the half-cut be made in the easily openable resin layer (I), and even more preferably that the half-cut does not extend beyond the easily openable resin layer (I). Attaching the half-cut to the side of the easily openable resin layer (I) tends to maintain the gas barrier properties of the barrier layer (II).

[0106] The depth of the half-cut is preferably 3-60% of the total sheet depth, and more preferably 5-45%. In addition, the depth of the half cut with respect to the easily peelable resin layer (I) is usually 1 to 99%, preferably 2 to 80%, more preferably 5 to 60%, and particularly preferably 7 to 40%.

[0107] 〔Notch〕 From the viewpoint of peelability, it is preferable that this sheet is provided with a notch (cutout). By providing the notch, when this sheet is made into a package, there is a tendency that the sheet is easily cracked and opened at the notch portion during opening.

[0108] <Physical properties of this sheet> This sheet can have the following physical properties.

[0109] 〔Tensile modulus〕 The easily peelable resin layer (I) of this sheet has a tensile modulus measured in accordance with JIS K7127 (1999) of 9 2.2×10 9 Pa or more, preferably 2.3×10 9 Pa or more, more preferably 2.4×10 9 Pa or more, and particularly preferably 2.5×10 9 Pa or more. Also, the upper limit of the tensile modulus is usually 3.0×10 To make the tensile modulus of the easily peelable resin layer (I) within the above range, for example, as the polypropylene resin (A), a method of using homopolypropylene, a method of using a petroleum resin-based tackifier (B), a method of combining these methods, etc. can be mentioned.

[0110] In addition, this sheet has a tensile modulus measured in accordance with JIS K7127 (1999) of usually 2.2×10 9 Pa or more, preferably 2.3×10 9 Pa or more, more preferably 2.4×10 9 Pa or more, and particularly preferably 2.5×10 9 Pa or more. Also, the upper limit of the tensile modulus is usually 3.0×10 9The value is Pa. Because the tensile modulus of the easily detachable resin layer (I) is within the aforementioned range, it tends to exhibit excellent crack resistance and ease of opening.

[0111] [Elongation at break] The easily openable resin layer (I) of this sheet preferably has a break elongation of 8% or less, more preferably 7.8% or less, and particularly preferably 7.0% or less, as measured in accordance with JIS K7127 (1999). Having a break elongation of the easily openable resin layer (I) within this range tends to result in excellent crack resistance and ease of opening.

[0112] [Hayes] The easy-open resin layer (I) of this sheet has a total haze of 80% or less, preferably 75% or less, and more preferably 70% or less, as measured in accordance with JIS K7136 (2000). Having a total haze of the easy-open resin layer (I) within this range tends to result in superior visibility, aesthetics, and design of the contents when used as packaging.

[0113] [Oxygen permeability] If this sheet has a barrier layer (II), the oxygen permeability of this sheet at a temperature of 23°C and 0RH%, as measured according to JIS K7126-1(2006) Method B, is 10.0 cc / m². 2 It is preferable that it is 24 hours or less, and more preferably 8.0 cc / m³ 2 • 24 hours or less, more preferably 6.0 cc / m³ 2 • Less than 24 hours, particularly preferably 4.0 cc / m³ 2 • Less than 24 hours. Because the oxygen permeability is within the aforementioned range, oxygen penetration can be suppressed, which tends to prevent corrosion and spoilage of the contents, allowing for long-term storage.

[0114] <Easy-to-open packaging> This sheet can be suitably used as a base material or lid material for food packaging. Furthermore, by heat-sealing the base material or lid material of a deep-drawn packaging body formed from this sheet with a film (lid material) or container made of thermoplastic resin, an easily openable packaging body can be created. In particular, this sheet is preferably used as a lid material for an easily openable packaging body.

[0115] The easily openable packaging obtained in this way is useful for packaging food products because it is easy to open, but it is also useful for packaging various other items such as daily necessities, general merchandise, medical supplies, and more. [Examples]

[0116] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. In the examples, "parts" and "%" refer to mass. Furthermore, in the examples, "MD direction" refers to the flow direction of the sheet, and "TD direction" refers to the direction perpendicular to the flow direction.

[0117] First, the following ingredients were prepared. <Easy-to-open resin layer (I)> [Polypropylene resin (A)] Homopolypropylene 1 (hPP1): MFR 11.2g / 10 min, melting point 165.7℃ Homopolypropylene 2 (hPP2): MFR 2.1g / 10 min, melting point 167.7℃ [Petroleum resin-based tackifier (B)] • Petroleum resin 1: Hydrogenated derivative of C9-type petroleum resin, softening point 100°C • Petroleum resin 2: Hydrogenated derivative of C9-type petroleum resin, softening point 125°C • Petroleum resin 3: Hydrogenated derivative of C9-type petroleum resin, softening point 140°C [Nuclear agent] • Nuclear agent 1: PP resin-based nuclear agent masterbatch (containing 0.7% nuclear agent component [trisaminobenzene derivative]) • Nuclear agent 2: PP resin-based nuclear agent masterbatch (containing nuclear agent component [magnesium stearate])

[0118] <Barrier layer (II)> [EVOH] • EVOH: Ethylene content 32 mol%, MFR 3.8 g / 10 min (manufactured by Mitsubishi Chemical Corporation)

[0119] <Outer layer (III)> A mixture of random PP [MFR 7.0g / 10 min (230℃), melting point 144℃ (manufactured by Prime Polymer Co., Ltd.)] and LDPE [MFR 0.7g / 10 min, melting point 114℃ (manufactured by Nippon Polyethylene Co., Ltd.)] in a mass ratio of random PP:LDPE = 85:15.

[0120] <Middle class> • Polypropylene resin (PP resin) <Adhesive layer> • Adhesive resin: Maleic anhydride-modified polypropylene adhesive resin

[0121] <Examples 1-3, Comparative Examples 2-3> The mixture was melted at 240°C using a co-direction twin-screw extruder (φ25mm) to achieve the mixing ratio shown in Table 1 below. Subsequently, it was cast at 90°C using a die set to 240°C to produce an easily openable resin layer (I) [food packaging sheet] with a thickness of 280 μm.

[0122] <Examples 4-8, Comparative Example 1> A masterbatch was prepared by melt-kneading hPP2 / petroleum resin 3 in a mass ratio of 1 / 1. Next, this masterbatch was melted at 240°C using a single-screw extruder (φ40mm) to the blending ratio shown in Table 1 below. Subsequently, a 280 μm thick easy-open resin layer (I) [food packaging sheet] was formed by casting at 110°C using a die set to 240°C.

[0123] The easily detachable resin layers (I) obtained from Examples 1-8 and Comparative Examples 1-3 were evaluated as follows. The results are shown in Table 1 below.

[0124] [Compression Test 1 (Cutability)] From the obtained easily openable resin layer (I), strip-shaped test pieces with a width of 25 mm in the TD direction and a length of 100 mm in the MD direction were prepared. A half-cut (half-cut TD) was made in the width direction at the center of the length direction of these test pieces using a cutter, and these were prepared as samples for the MD direction. Furthermore, strip-shaped test pieces with a width of 25 mm in the MD direction and a length of 100 mm in the TD direction were prepared from the easily opened resin layer (I). A half-cut (half-cut MD) was made in the width direction at the center of the length direction of these test pieces using a cutter, and these were used as samples for the TD direction. The cross-sections of these samples were observed using a digital microscope (PerkinElmer, "VHX-6000") to measure the depth of the half-cut. Subsequently, these samples were subjected to compression tests using a universal material testing machine (Shimadzu Corporation, "Autograph AGS-X") at a temperature of 23°C and a speed of 50 mm / min, with the side with the half-cut facing outwards when bent. They were then evaluated according to the following evaluation criteria. [Evaluation Criteria (Compression Test)] ○: Complete destruction ×: Non-destructive [Evaluation Criteria (Half Cut)] ○: Compression test results are "○", and the maximum test force of the compression test is 10N or less. △: Compression test result is "○", and the maximum test force of the compression test is greater than 10N. ×: Compression test is "×"

[0125] [Tensile test] From the obtained easily openable resin layer (I), a dumbbell-shaped test specimen with a width of 6 mm in the TD direction and an initial length of 80 mm in the MD direction was prepared and used as a sample for MD measurement. In addition, dumbbell-shaped test specimens with a width of 6 mm in the MD direction and an initial length of 80 mm in the TD direction were prepared from food packaging sheets and used as samples for TD measurement. Subsequently, these samples were subjected to tensile testing using a universal material testing machine (Shimadzu Corporation, "Autograph AGS-X") at a temperature of 23°C and a speed of 200 mm / min, and evaluated according to the following evaluation criteria. [Evaluation Criteria] ○: Elongation at break in both the MD and TD directions is 8% or less. △: Elongation at break in either the MD direction or the TD direction is greater than 8% or less than 10%. ×: Elongation at break exceeds 10% in either the MD direction or the TD direction.

[0126] [Tensile modulus of elasticity] From the obtained easily openable resin layer (I), strip-shaped test pieces with a width of 4 mm in the TD direction and a length of 80 mm in the MD direction were prepared and used as samples for the MD direction. Furthermore, strip-shaped test pieces with a width of 4 mm in the MD direction and a length of 80 mm in the TD direction were prepared from the easily openable resin layer (I) and used as samples for the TD direction. Subsequently, these samples were subjected to measurement of the storage modulus E'(Pa) at 25°C in tensile mode with a chuck distance of 20 mm, a frequency of 10 Hz, and a dynamic viscoelasticity measuring device (TA Instruments, "DiscoveryHR2") based on JIS K7244-4 (1999), and evaluated according to the following evaluation criteria. [Evaluation Criteria] ○: 2.2 × 10 9 More than Pa △: 2.0 × 10 9 Pa or more, 2.2×10 9 Less than Pa ×: 2.0 × 10 9 Less than Pa

[0127] [DSC] The melting point and heat of fusion of the obtained easy-open resin layer (I) were calculated from the reheating process when the material was heated, cooled, and reheated at a heating rate of 10°C / min using a differential scanning calorimetry analyzer (PerkinElmer, "DSC8000").

[0128] [Transparency] Using a turbidimeter (NDH 5000, manufactured by Nippon Denshoku Industries Co., Ltd.), light was shone onto food packaging sheets, and the total haze was measured in accordance with JIS K7136 (2000).

[0129] [Table 1]

[0130] <Examples 9-13, Comparative Examples 4, 5> A food packaging sheet was prepared by laminating the intermediate layer 1 (PP-based resin layer) of a laminated sheet having an easily openable resin layer (I) as shown in Table 2 below and a barrier layer (II) with the configuration shown below, using a vacuum laminator (Nisshinbo Mechatronics Co., Ltd., "PVL050S", lamination temperature 170°C). The food packaging sheet consists of an easy-open resin layer (I), an intermediate layer 1 (PP-based resin layer), an intermediate layer 2 (PP-based resin layer), an adhesive layer, a barrier layer (II), an adhesive layer, an intermediate layer 3 (PP-based resin layer), and an outer layer (III), with the thickness of each layer (μm) being 280 / 4 / 12 / 4 / 5 / 4 / 5 / 6.

[0131] The food packaging sheets obtained from Examples 9-13 and Comparative Examples 4 and 5 were evaluated as follows. The results are shown in Table 2 below.

[0132] [Compression Test 2 (Cutability)] From the obtained food packaging sheet, strip-shaped test pieces with a width of 25 mm in the TD direction and a length of 100 mm in the MD direction were prepared. A half-cut (half-cut TD) was made in the width direction at the center of the length direction of this test piece using a cutter, and this was used as the sample for the MD direction. Furthermore, strip-shaped test pieces with a width of 25 mm in the MD direction and a length of 100 mm in the TD direction were prepared from the easily opened resin layer (I). A half-cut (half-cut MD) was made in the width direction at the center of the length direction of these test pieces using a cutter, and these were used as samples for the TD direction. Half-cut samples were placed on both the easily-opened resin layer (I) side and the outer layer (III) side, and each was used as a sample. The cross-sections of these samples were observed using a digital microscope (PerkinElmer, "VHX-6000") to measure the depth of the half-cut. Subsequently, these samples were subjected to compression tests using a universal material testing machine (Shimadzu Corporation, "Autograph AGS-X") at a temperature of 23°C and a speed of 50 mm / min, with the side with the half-cut facing outwards when bent. They were then evaluated according to the following evaluation criteria. [Evaluation Criteria (Compression Test)] ○: Complete destruction ×: Non-destructive [Evaluation Criteria (Half Cut)] ○: Compression test results are "○", and the maximum test force of the compression test is 10N or less. △: Compression test result is "○", and the maximum test force of the compression test is greater than 10N. ×: Compression test is "×"

[0133] [Oxygen permeability] The outer layer (III) of the obtained food packaging sheet was cut in half using a cutter to create a sample for oxygen permeability [outer layer (III) side sample]. Furthermore, a half-cut was made using a cutter on the easily-open resin layer (I) side of the food packaging sheet to create a sample for oxygen permeability [easily-open resin layer (I) side sample]. For these samples, the oxygen permeability (cc / m³) at 23°C and 0%RH was measured using a gas barrier test apparatus (MOCON, "OX-TRAN 2 / 21 SH") in accordance with JIS K-7126-2. 2 The measurement was taken (24 hours atm).

[0134] [Tensile modulus of elasticity] From the obtained food packaging sheet, strip-shaped test pieces with a width of 4 mm in the TD direction and a length of 80 mm in the MD direction were prepared and used as samples for the MD direction. In addition, strip-shaped test pieces with a width of 4 mm in the MD direction and a length of 80 mm in the TD direction were prepared from food packaging sheets and used as samples for the TD direction. Subsequently, these samples were subjected to measurement of the storage modulus E'(Pa) at 25°C in tensile mode with a chuck distance of 20 mm, a frequency of 10 Hz, and a dynamic viscoelasticity measuring device (TA Instruments, "DiscoveryHR2") based on JIS K7244-4 (1999), and evaluated according to the following evaluation criteria. [Evaluation Criteria] ○: 2.2 × 10 9 More than Pa △: 2.0 × 10 9 Pa or more, 2.2×10 9 Less than Pa ×: 2.0 × 10 9 Less than Pa

[0135] [Table 2]

[0136] From the results in Tables 1 and 2, the food packaging sheet of the example having an easy-open resin layer (I) containing a polypropylene resin (A) and a petroleum resin tackifier (B), with a tensile modulus within a specific range, exhibited excellent crack resistance and ease of opening. On the other hand, the food packaging sheets of Comparative Examples 1 to 5, which did not contain petroleum resin-based tackifiers (B), had poor cutability and inferior crackability. [Industrial applicability]

[0137] Because this sheet has excellent crackability and ease of opening, it can be suitably used as a bottom or lid material for easy-open packaging for food products.

Claims

1. A food packaging sheet having an easily openable resin layer (I) containing a polypropylene resin (A) and a petroleum resin tackifier (B), The tensile modulus of the aforementioned easily openable resin layer (I), measured in accordance with JIS K7127 (1999), was 2.2 × 10⁻⁶. ９ Food packaging sheets with a strength of Pa or higher.

2. The food packaging sheet according to claim 1, wherein the polypropylene resin (A) is homopolypropylene.

3. Furthermore, the food packaging sheet according to claim 1, further comprising a barrier layer (II).

4. The food packaging sheet according to claim 3, wherein the barrier layer (II) mainly comprises an ethylene-vinyl alcohol resin.

5. The food packaging sheet according to claim 3, wherein the outermost layer on the side of the barrier layer (II) is an outer layer (III).

6. The food packaging sheet according to claim 5, wherein the outer layer (III) mainly contains a polyolefin resin.

7. The food packaging sheet according to claim 3, wherein the ratio of the thickness of the barrier layer (II) to the total thickness of the food packaging sheet is 0.5 to 15%.

8. The oxygen permeability measured in accordance with JIS K7126-1 (2006) was 10.0 cc / m³. ２ - A food packaging sheet according to claim 3, wherein the shelf life is 24 hours or less.

9. A food packaging sheet according to claim 1, wherein a half-cut or notch is provided.

10. The food packaging sheet according to claim 3, wherein a half-cut or notch is provided on the side of the easily openable resin layer (I).

11. An easily openable package using a food packaging sheet according to any one of claims 1 to 10.

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