JP7810040B2 - Easy-to-open laminate - Google Patents

Description

The present invention relates to an easy-to-open laminate.

Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH), which has excellent gas barrier properties, aroma retention, and solvent resistance, is used in a variety of applications as a thermoplastic resin packaging material for foods, beverages, pharmaceuticals, etc., to prevent deterioration of the contents. Films and laminates (see, for example, Patent Document 1) made by co-extrusion of polyethylene resin, acid-modified polyolefin, and EVOH are also produced.

However, such films and laminates do not have the easy-to-open (easy-peel) properties required for container lids. This requires the use of so-called easy-peel resins in the sealing layer of the lid, which is cost-inefficient.

Given this background, there has long been a demand for laminates with excellent gas barrier properties, adhesive properties, and ease of opening.

Japanese Patent Application Laid-Open No. 1992-234645

The present invention has been developed in consideration of the above-mentioned circumstances, and aims to provide a laminate that exhibits excellent gas barrier properties, adhesive properties, and easy-open properties.

As a result of extensive research to solve the above-mentioned problems, the inventors discovered that a specific laminate exhibits excellent gas barrier properties, adhesive properties, and ease of opening, leading to the completion of the present invention.

The embodiments of the present invention are [1] to [8] shown below.
[1] An easy-open laminate comprising at least a base layer and a (C) layer/(B) layer/(A) layer adjacent to each other from the base layer side, wherein the (A) layer is composed of polyethylene (a), the (B) layer is composed of acid-modified polypropylene (b) satisfying (i) to (ii), and the (C) layer is composed of an ethylene-vinyl alcohol copolymer (c) satisfying (iii), and the laminate satisfies (iv) to (v).

(i) a melt mass flow rate (MFR _ADD ) at 230°C measured according to JIS 7210 (1999) of 2.0 g/10 min or more and 20.0 g/10 min or less; (ii) an acid content of 0.02 wt% or more and 1.0 wt% or less; (iii) an ethylene content _C2 of 50 mol% or less; (iv) a thickness of the (A) layer of 1 μm or more and 15 μm or less; and (v) an adhesive strength between the (A) layer and the (B) layer of 0.1 N/15 mm or more and 3.0 N/15 mm or less [2] The easy-open laminate according to the above [1], wherein the acid content of the acid-modified polypropylene (b) is 0.05 wt% or more and 0.40 wt% or less.
[3] The easy-open laminate according to any one of the above [1] or [2], wherein the acid-modified polypropylene (b) is maleic anhydride-grafted modified polypropylene.
[4] The easy-open laminate according to any one of the above [1] to [3], wherein the polyethylene (a) satisfies (vi) to (viii).

(vi) a melt mass-flow rate (MFR _PE ) measured according to JIS K6922-1 (1997) of 1.0 g/10 min or more and 10.0 g/10 min or less; (vii) a melt tension (MS _PE ) measured at a temperature of 190°C and a take-up speed of 10 m/min of 3 mN or more and 50 mN or less; and (viii) a product MFR _PE × MS _PE of MFR _PE (g/10 min) and MS _PE (mN) of 70 or more and 250 or less. [5] The easy-open laminate according to any one of the above [1] to [4], wherein the polyethylene (a) comprises an ethylene-α-olefin copolymer and/or a high-pressure low-density polyethylene.
[6] The easy-open laminate according to any one of the above [1] to [5], wherein the C ₂ (mol %) of the ethylene-vinyl alcohol copolymer (c) and its density D _EVOH (kg/m ³ ) at 20°C measured according to ISO1183-3 satisfy the following formula (1):

D _EVOH <-4.265×C ₂ +1325 (1)
[7] The easy-open laminate according to any one of the above [1] to [6], further comprising an (E) layer/a (D) layer between the base material layer and the (C) layer, the (E) layer being adjacent to the base material layer, the (D) layer being adjacent to the (C) layer, the (E) layer being polyethylene (e), and the (D) layer being acid-modified polypropylene (d).
[8] The method for producing the easy-open laminate according to any one of the above [1] to [7], wherein the (C) layer/(B) layer/(A) layer or the (E) layer/(D) layer/(C) layer/(B) layer/(A) layer are simultaneously formed by co-extrusion lamination molding.

The present invention makes it possible to provide a laminate with excellent gas barrier properties, adhesive properties, and easy-open properties.

FIG. 2 is a diagram showing formulas (1) and (2).

Each aspect of the present invention is described in detail below.

An easy-open laminate, one embodiment of the present invention, is a laminate including at least a base layer and a (C) layer, a (B) layer, and an (A) layer adjacent to each other from the base layer side, in which the (A) layer is composed of polyethylene (a), the (B) layer is composed of acid-modified polypropylene (b) that satisfies (i) to (ii), and the (C) layer is composed of an ethylene-vinyl alcohol copolymer (c) that satisfies (iii), and satisfies (iv) to (v).

(i) a melt mass flow rate (MFR _ADD ) at 230°C measured according to JIS 7210 (1999) of 2.0 g/10 min or more and 20.0 g/10 min or less; (ii) an acid content of 0.02 wt% or more and 1.0 wt% or less; (iii) an ethylene content _C2 of 50 mol% or less; (iv) a thickness of the (A) layer of 1 μm or more and 15 μm or less; and (v) an adhesive strength between the (A) layer and the (B) layer of 0.1 N/15 mm or more and 3.0 N/15 mm or less. The (A) layer is composed of polyethylene (a).

The polyethylene (a) is not particularly limited, and examples thereof include ethylene homopolymers, copolymers of ethylene with α-olefins having 2 to 12 carbon atoms, such as propylene or 1-butene, and copolymers of ethylene with vinyl esters and/or acrylic esters. More specific examples include ethylene homopolymers such as high-pressure low-density polyethylene and high-density polyethylene, ethylene-α-olefin copolymers such as ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and ethylene-4-methyl-1-pentene copolymer, and ethylene polymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and ethylene-methacrylic ester copolymer. Polyethylene (a) may be used alone or in a composition of two or more types. Among these, high-pressure low-density polyethylene and ethylene-α-olefin copolymers are preferred due to their excellent moldability. Furthermore, from the standpoint of moldability, it is preferable that the ethylene-α-olefin copolymer contain high-pressure low-density polyethylene.

High-pressure radical polymerization is an example of a method for producing high-pressure low-density polyethylene, and such resins can be conveniently selected from commercially available products, such as those sold by Tosoh Corporation under the trade name Petrothene.

Ethylene-α-olefin copolymers can be obtained by copolymerizing ethylene and α-olefins using high-, medium-, or low-pressure ionic polymerization methods with Ziegler-Natta catalysts, Phillips catalysts, or metallocene catalysts.

Examples of the α-olefins that make up the ethylene-α-olefin copolymer include propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene, and one or more of these may be used. Among these α-olefins, α-olefins with 5 or fewer carbon atoms are preferred because of their superior ease of opening.

Such ethylene-α-olefin copolymers can be conveniently selected from commercially available products. For example, they are commercially available from Tosoh Corporation under the trade names Nipolon-L, Nipolon-Z, and Lumitac.

The melt mass flow rate (hereinafter abbreviated as "MFR _PE ") of the polyethylene (a) measured in accordance with JIS K6922-1 (1997) is preferably in the range of 1.0 g/10 min or more and 10.0 g/10 min or less, more preferably 1.0 g/10 min or more and 6.0 g/10 min or less, and most preferably 3.0 g/10 min or more and 5.0 g/10 min or less, in order to provide excellent co-extrusion lamination processability (migration) with acid-modified polypropylene and ethylene-vinyl alcohol copolymer.

Furthermore, the melt tension of the polyethylene (a) measured at a temperature of 190°C and a take-up speed of 10 m/min (hereinafter abbreviated as "MS _PE ") is preferably in the range of 3 mN or more and 50 mN or less, more preferably 10 mN or more and 45 mN or less, and most preferably 15 mN or more and 40 mN or less, in order to achieve excellent productivity.

The MS _PE in the present invention is a value measured under conditions where a capillary viscometer having a barrel diameter of 9.55 mm is equipped with a die having a length of 8 mm, a diameter of 2.095 mm, and an inlet angle of 90°, and a heat-retaining chamber, at an extrusion speed of 10 m/min, a take-up speed of 10 m/min, and a set temperature of 190°C.

The product MFR _PE × MS _PE of the polyethylene (a) of MFR _PE (g/10 min) and MS _PE (mN) is preferably in the range of 70 or more and 250 or less, more preferably in the range of 70 or more and 200 or less, and most preferably in the range of 90 or more and 160 or less, in view of excellent productivity. Such MFR _PE × MS _PE is a value that correlates with the ratio of melt elasticity to melt viscosity of polyethylene, that is, the nonlinearity of polyethylene during melt deformation.

The density of the polyethylene (a) measured in accordance with JIS K6922-1 (1997) (hereinafter simply referred to as density) is not particularly limited, and is preferably in the range of 880 to 970 kg/ ^m3 , more preferably in the range of 900 to 950 kg/ ^m3 , and most preferably in the range of 905 to 940 kg/ ^m3 , in order to achieve excellent moldability and easy opening.

The polyethylene (a) in the present invention may be blended with other thermoplastic resins as long as the intended purpose is achieved.

When mixing polyethylene (a) with a thermoplastic resin, a pellet mixture of polyethylene pellets and thermoplastic resin pellets in a solid state may be used, but a mixture melt-kneaded using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, etc. is preferred, as it produces a product of consistent quality. When using a melt-kneading device, the melting temperature should preferably be between the melting point of polyethylene and approximately 300°C.

Additionally, if necessary, additives commonly used in polyolefin resins, such as antioxidants, light stabilizers, antistatic agents, lubricants, and antiblocking agents, may be added to polyethylene (a) to the extent that the objectives of the present invention are not impaired.

Layer (B) is composed of acid-modified polypropylene (b).

The polypropylene constituting the acid-modified polypropylene (b) of the present invention is not particularly limited as long as the objective is achieved, and examples include a propylene homopolymer or a copolymer of propylene and 50 mol% or less of an α-olefin such as ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, or 1-octene.

Examples of acid-modified polypropylene (b) include copolymers of the above-mentioned polypropylene with an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid, or acrylic acid ionomer, or an ionomer thereof; copolymers of the above-mentioned polypropylene with an unsaturated dicarboxylic acid such as maleic acid or maleic anhydride, or an anhydride thereof; polypropylenes graft-modified with the above-mentioned polypropylene with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, or maleic anhydride, or an anhydride thereof, an ionomer, or a boronic acid; and copolymers of the above-mentioned polypropylene with glycidyl methacrylate. These acid-modified polypropylenes (b) may be used alone or in combination of two or more.

Among these, from the standpoint of adhesiveness and cost, it is preferable to use at least maleic anhydride-grafted polypropylene (hereinafter sometimes abbreviated as "MAH-PP") or a copolymer of polypropylene and maleic anhydride, and more preferably MAH-PP.

Such maleic anhydride-modified polypropylene can be conveniently selected from commercially available products. For example, maleic anhydride-grafted modified polypropylene is commercially available from Mitsui Chemicals, Inc. under the trade name ADMER, Mitsubishi Chemical Corporation under the trade name MODIC, Dow Chemical Japan Co., Ltd. under the trade name FUSABOND, SK GeoCentric Japan Co., Ltd. under the trade name OREVAC G, Addivant Japan LLC under the trade name POLYBOND, Riken Vitamin Co., Ltd. under the trade name RIKEAID, and Sanyo Chemical Co., Ltd. under the trade name UMEX. Furthermore, a copolymer of polypropylene and maleic anhydride is commercially available from Honeywell Japan Inc. under the trade name Honeywell A-C Polyolefin Wax.

The melt mass flow rate (hereinafter abbreviated as "MFR _ADD ") of the acid-modified polypropylene (b) at 230°C measured according to JIS 7210 (1999) is in the range of 2.0 g/10 min to 20.0 g/10 min, more preferably 2.0 g/10 min to 12.0 g/10 min, and most preferably 4.0 g/10 min to 10.0 g/10 min, in order to obtain excellent coextrusion lamination processability (migration) and moldability with polyethylene ethylene and ethylene-vinyl alcohol copolymer. _{MFR ADD} (g/10 min) in the range of less than 2.0 g/10 min or more than 20.0 g/10 min is not preferred because it results in poor coextrusion lamination processability and moldability.

The acid content of such acid-modified polypropylene (b) is in the range of 0.02 to 1.0% by weight, more preferably 0.05 to 0.40% by weight, and most preferably 0.10 to 0.25% by weight, since this provides excellent appearance upon opening and film appearance. An acid content of less than 0.02% by weight is undesirable because it results in poor appearance upon opening, and an acid content of more than 1.0% by weight is undesirable because it results in poor film appearance.

From the standpoints of moldability and film appearance, the acid-modified polypropylene (b) is preferably a polypropylene composition containing at least an unmodified polyolefin and MAH-PP.

From the standpoint of adhesiveness and film appearance, the polypropylene composition preferably contains 50 to 90 parts by weight of polyolefin and 10 to 50 parts by weight of MAH-PP (total of polyolefin and MAH-PP is 100 parts by weight), and more preferably contains 65 to 85 parts by weight of polyolefin and 15 to 35 parts by weight of MAH-PP (total of polyolefin and MAH-PP is 100 parts by weight).

Such polyolefins are not particularly limited, and examples include homopolymers of α-olefins having 2 to 12 carbon atoms, such as ethylene, propylene, and 1-butene, or copolymers thereof, and copolymers of ethylene with vinyl esters and/or acrylic esters.

Examples of suitable polyolefins include ethylene homopolymers such as high-pressure low-density polyethylene and high-density polyethylene; ethylene-based polymers such as ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, and ethylene-methacrylic acid ester copolymers; propylene homopolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, poly-1-butene, poly-1-hexene, and poly-4-methyl-1-pentene. Polyolefins may be used alone or in combinations of two or more. Among these, at least one selected from the group consisting of high-pressure low-density polyethylene, ethylene-vinyl acetate copolymers, high-density polyethylene, ethylene-1-butene copolymers, ethylene-1-hexene copolymers, and polypropylene is preferred from the standpoint of moldability, and these compositions are most preferred due to their excellent moldability.

Other thermoplastic resins may be blended with the acid-modified polypropylene (b) as long as the intended purpose is achieved. When mixing the thermoplastic resin with the acid-modified polypropylene (b), a pellet mixture in which pellets of saponified ethylene-vinyl ester copolymer and pellets of the thermoplastic resin are mixed in a solid state may be used. However, a mixture melt-kneaded using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, etc. is preferred, as it produces a product of consistent quality. When using a melt-kneading device, the melting temperature is preferably between the melting point of the polyolefin composition and approximately 300°C.

Additionally, if necessary, additives commonly used in polyolefin resins, such as antioxidants, light stabilizers, antistatic agents, lubricants, and antiblocking agents, may be added to the acid-modified polypropylene (b) to the extent that the objectives of the present invention are not impaired.

The ethylene content (hereinafter sometimes abbreviated as _C2 ) of the ethylene-vinyl alcohol copolymer (c) is 50 mol % or less, preferably 20 to 35 mol %, because it has excellent gas barrier properties. This further improves the gas barrier properties. Here, _C2 (mol %) refers to the content of ethylene components in the monomer units contained in the ethylene-vinyl alcohol copolymer (c).

There are no particular limitations on the method for producing the ethylene-vinyl alcohol copolymer (c). For example, a copolymer of ethylene and a fatty acid vinyl ester can be produced according to a known method, and then this can be hydrolyzed (saponified) to produce EVOH.

The degree of saponification of such ethylene-vinyl alcohol copolymer (c) is preferably in the range of 80% by weight or more, as this provides excellent gas barrier properties.

In addition to ethylene units and vinyl alcohol units, EVOH may also contain small amounts of other structural units.

Such resins can be conveniently selected from commercially available products, such as those sold by Kuraray Co., Ltd. under the trade names EVAL and Mitsubishi Chemical Corporation under the trade names Soarnol and G-Soarnol.

The melt mass flow rate of the ethylene-vinyl alcohol copolymer (c) at 190°C (temperature 190°C, load 2.16 kg, hereinafter abbreviated as "MFR _EVOH ") measured in accordance with ISO 1133 is preferably in the range of 1.0 g/10 min to 8.0 g/10 min, more preferably 1.0 g/10 min to 6.0 g/10 min, and most preferably 1.0 g/10 min to 3.0 g/10 min, from the viewpoints of moldability and film appearance. Furthermore, the melt mass flow rate of the ethylene-vinyl alcohol copolymer (c) at 210°C (temperature 210°C, load 2.16 kg) measured in accordance with ISO 1133 is preferably in the range of 2.5 to 20.0 g/10 min, more preferably 2.5 to 15.0 g/10 min, and most preferably 2.5 to 7.5 g/10 min, from the viewpoints of moldability and film appearance.

The density of the ethylene-vinyl alcohol copolymer (c) at 20°C measured in accordance with ISO 1183-3 (hereinafter abbreviated as "D _EVOH ") is preferably less than 1190 kg/ ^m3 , more preferably 1100 to 1180 kg/ ^m3 , and most preferably 1140 to 1180 kg/ ^m3 , from the viewpoints of film appearance and adhesiveness.

In addition, in order to obtain excellent film appearance and adhesiveness, it is preferable that the C ₂ (mol %) and D _EVOH (kg/m ³ ) of the ethylene-vinyl alcohol copolymer (c) satisfy the following formula (1), and more preferably the following formula (2):

D _EVOH <-4.265×C ₂ +1325 (1)
D _EVOH <-4.265×C ₂ +1315 (2)
The substrate layer is not particularly limited and may be selected appropriately depending on the application. Examples of suitable materials include films, woven fabrics, and nonwoven fabrics formed from synthetic polymers, as well as metal foils, paper, and cellophane. Examples of suitable synthetic polymers include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6 and nylon 66, polyethylene resins such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and ionomers, polypropylene resins, polybutene, acrylic resins, polyvinyl alcohol, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polycarbonate, polyurethane, and cellulose resins. The synthetic polymer constituting the substrate layer may be the same as or different from the polyethylene (a). Furthermore, these polymer films and sheets may be further treated with aluminum vapor deposition, alumina vapor deposition, silicon dioxide vapor deposition, or acrylic. These polymer films and sheets may also be printed with urethane ink, etc. Examples of metal foils include aluminum foil and copper foil, and examples of paper include kraft paper, fine paper, stretched paper, glassine paper, and paperboard such as cup base paper and photographic paper base paper. These substrates may be used alone or in combination of two or more.

One embodiment of the laminate of the present invention is characterized by comprising at least a substrate layer and, from the substrate layer side, a (C) layer, a (B) layer, and a (A) layer. It may be composed solely of these four components or may also contain other components, such as a (D), (E), or (F) layer. Specific examples include substrate layer/(C) layer/(B) layer/(A) layer, (D) layer/substrate layer/(C) layer/(B) layer/(A) layer, substrate layer/(D) layer/(C) layer/(B) layer/(A) layer, (E) layer/substrate layer/(D) layer/(C) layer/(B) layer/(A) layer, substrate layer/(E) layer/(D) layer/(C) layer/(B) layer/(A) layer, and (F) layer/substrate layer/(E) layer/(D) layer/(C) layer/(B) layer/(A) layer. The symbol / between layers indicates that the layers are adjacent.

Examples of layers (D), (E), and (F) include layers formed from synthetic polymers, woven fabrics, nonwoven fabrics, metal foils, paper, cellophane, etc. Examples include layers formed from synthetic polymers such as polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon 6 and nylon 66; polyethylene resins such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and ionomer; polypropylene resins, polybutene, acrylic resins, polyvinyl alcohol, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polycarbonate, polyurethane, and cellulose resins. Furthermore, these polymer films and sheets may be further treated with aluminum vapor deposition, alumina vapor deposition, silicon dioxide vapor deposition, or acrylic. These polymer films and sheets may also be printed with urethane inks, etc. Examples of metal foil include aluminum foil and copper foil, and examples of paper include kraft paper, fine paper, stretch paper, glassine paper, and paperboard such as cup base paper and photographic paper base paper.

Among these laminates, from the viewpoint of excellent productivity and gas barrier properties, a laminate comprising at least adjacent base layer/(E) layer/(D) layer/(C) layer/(B) layer/(A) layer is preferred, that is, a laminate further comprising an (E) layer/(D) layer between the base layer and the (C) layer, the (E) layer being adjacent to the base layer, the (D) layer being adjacent to the (C) layer, the (E) layer being polyethylene (e), and the (D) layer being acid-modified polypropylene (d).Here, the polyethylene (a) constituting the (A) layer and the polyethylene (e) constituting the (E) layer may be the same or different, but from the viewpoint of productivity, it is more preferred that they are the same component.In addition, the acid-modified polypropylene (b) constituting the (B) layer and the acid-modified polypropylene (e) constituting the (D) layer may be the same or different, but from the viewpoint of productivity, it is more preferred that they are the same component.
The extrusion lamination method for obtaining a laminate is not particularly limited, and examples include various extrusion lamination methods such as tandem lamination, in which each layer is laminated in order, and coextrusion lamination, in which several layers are laminated simultaneously. Among these, from the viewpoint of cost, it is preferable to simultaneously form (C) layer/(B) layer/(A) layer or (E) layer/(D) layer/(C) layer/(B) layer/(A) layer by coextrusion lamination. Furthermore, the most preferred method is a three-kind five-layer extrusion lamination method in which the (A) layer and the (E) layer are made of the same component, and the (B) layer and the (D) layer are made of the same component. In such an extrusion lamination method, the resin temperature is preferably in the range of 180 to 280°C, and the surface temperature of the cooling roll is preferably in the range of 10 to 50°C.

In addition, in extrusion lamination, a method is preferably used in which, immediately after forming a layer from a thermoplastic resin constituting a layer adjacent to a substrate layer in a molten state into an extruded layer, the substrate adhesive surface of the layer is exposed to an oxygen-containing gas or an ozone-containing gas, and then the layer is laminated to the substrate, since this method provides excellent adhesion to the substrate layer. When improving the adhesion between the thermoplastic resin and the substrate using an ozone-containing gas, it is preferable to spray 0.5 mg or more of ozone per ^m2 of film made of thermoplastic resin extruded from a die.

To further improve adhesion between the thermoplastic resin layer and the substrate layer, the extrusion lamination method used to obtain the laminate can be heat-treated for 10 hours or more at a temperature that does not cause the resin of each layer to foam, such as 30°C to 60°C. If necessary, the adhesive surface of the substrate layer may be subjected to a known surface treatment such as corona treatment, flame treatment, or plasma treatment. If necessary, an anchor coating agent may also be applied to the substrate layer.

The thickness of the (A) layer is in the range of 1 μm or more and 15 μm or less, more preferably 3 μm or more and 10 μm or less, and most preferably 3 μm or more and 6 μm or less, in order to achieve excellent ease of opening, appearance after opening, and sealing properties. A thickness of the (A) layer less than 1 μm is undesirable because sealing properties will be poor, and a thickness of more than 15 μm is undesirable because ease of opening and appearance after opening will be poor.

The adhesive strength between Layer (A) and Layer (B) is in the range of 0.1 N/15 mm or more and 3.0 N/15 mm or less, and more preferably 0.5 N/15 mm or more and 2.0 N/15 mm or less, in order to achieve excellent ease of opening, appearance after opening, and sealability. Adhesion strength between Layer (A) and Layer (B) of less than 0.1 N/15 mm is undesirable because sealability will be poor, and adhesion strength exceeding 3.0 N/15 mm is undesirable because ease of opening and appearance after opening will be poor.

This adhesive strength was measured using a laminate cut into a 15 mm width after peeling the interface between layers (A) and (B). The value was measured using a tensile tester, Tensilon RTE-1210 (manufactured by Orientec Co., Ltd.), at a tensile speed of 300 mm/min and a peel angle of 180°.

The easy-open laminate of the present invention has excellent film appearance, adhesiveness, and gas barrier properties against oxygen and other gases, and also has excellent ease of opening, making it suitable for use in packaging materials and containers made from thermoplastic resins for foods, beverages, pharmaceuticals, and other products that require these properties.

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.
(1) Melt Mass Flow Rate (MFR)
The MFR was measured in accordance with JIS K6922-1 (1997), JIS K7210 (1999), or ISO1133.
(2) Density The density was measured in accordance with JIS K6922-1 (1997), JIS K7210 (1999), or ISO1183-3.
(3) Melt tension (MS)
In a thermostatic chamber set to 23°C, the temperature was set to 190°C, and 18 g of polyolefin was filled into a capillary viscometer (Toyo Seiki Seisaku-sho, trade name: Capilograph) with a barrel diameter of 9.55 mm, equipped with a die having a length of 8 mm, a diameter of 2.095 mm, and an inlet angle of 90°, and a heat-retaining chamber. The piston descending speed was set to 10 mm/min, and the take-up speed was set to 10 m/min, and the load (mN) required for take-up was measured as the melt tension (MS).
(6) Migration The rotation speed of each extruder was set so as to obtain the thickness described in the examples at a processing speed of 50 m/min, and the molten film extruded from the T-die was visually measured. The molten film immediately below the die was observed, and the width of the EVOH layer generated on both ends of the molten film that had not been wrapped around was measured, and the sum of the widths at both ends of the molten film was taken as the migration (mm). The smaller the migration, the better the productivity.
(7) Maximum Processing Speed/Stretchability The maximum processing speed was determined by increasing the rotation speed of each extruder and the processing speed in conjunction with each other so that the thickness of the easy-open laminate would be the thickness described in the Examples, and the processing speed at which film breakage occurred was defined as the maximum processing speed (m/min). The higher the maximum processing speed, the better the stretchability and productivity.
(8) Preparation of Sealant Film High-pressure low-density polyethylene (manufactured by Tosoh Corporation under the trade name Petrothene 203, hereinafter abbreviated as LDPE) having an MFR of 8 g/10 min and a density of 919 kg/ ^m3 was fed into a single-screw extruder (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a screw diameter of 40 mm and set at 330°C, and extruded through a T-die at a temperature of 330°C. Single-layer extrusion lamination molding was carried out on a PET/PE substrate (manufactured by Howa Sangyo Co., Ltd.) consisting of 25 μm of PET, an anchor coating agent, and 15 μm of polyethylene laminated in that order, at a processing speed of 50 m/min, with an air gap length of 110 mm, so that the thickness of the LDPE was 15 μm, to obtain a sealant film consisting of PET, anchor coating agent, polyethylene, and LDPE laminated in that order.
(9) Adhesive Strength The easy-open laminate and sealant film obtained in the examples were cut into a width of 100 mm and a length of 100 mm, and the (A) layer of the easy-open laminate and the LDPE surface of the sealant film were overlapped. Using a heat seal tester TP-701B (manufactured by Tester Sangyo Co., Ltd.), the set temperature was 160 ° C., one side was heated (sealant film side), air pressure was 0.3 MPa, and the sealing time was 2 seconds. Heat sealing was performed with a seal bar having a width of 10 mm and a length of 300 mm. This test piece was peeled by hand to peel the interface between the (A) layer and the (B) layer, and then cut into a width of 15 mm. A peel test was performed using a tensile tester Tensilon RTE-1210 (manufactured by Orientec Co., Ltd.) at a tensile speed of 300 mm / min and a peel angle of 180 °, and the adhesive strength (N / 15 mm) was measured.
(10) Opening Strength/Opening Appearance The (A) layer of the easy-open laminate and the LDPE surface of the sealant film were overlapped, and heat-sealed using a heat seal tester TP-701B (manufactured by Tester Sangyo Co., Ltd.) with a set temperature of 160°C, single-sided heating (sealant film side), air pressure of 0.3 MPa, and a sealing time of 2 seconds, using a seal bar 10 mm wide and 300 mm long. This test piece was cut into a width of 15 mm, and a peel test was performed using a tensile tester Tensilon RTE-1210 (manufactured by Orientec Co., Ltd.) at a tensile speed of 300 mm/min and a peel angle of 180° to measure the opening strength (N/15 mm).

With regard to ease of opening, an opening strength (N/15mm) of 20 or more was rated as "X", 15 or more but less than 20 was rated as "△", 10 or more but less than 15 was rated as "〇", and less than 10 was rated as "◎". An opening strength (N/15mm) of less than 20 was rated as good ease of opening.

Next, regarding the appearance after opening, after measuring the opening strength, the seal on the easy-open laminate side was visually observed, and if the edge tear where layer (A) broke was good at both the peel start and end points, it was rated as ◎; if the edge tear was good at either the peel start or end points, it was rated as ○; if the edge tear was poor at both the peel start and end points, it was rated as △; and if no edge tear occurred but triangular peeling occurred, where interlayer peeling between layers (A) and (B) and interfacial peeling between layer (A) and the LDPE of the sealant film occurred simultaneously, it was rated as ×. The appearance after opening was rated as good if triangular peeling did not occur.

Example 1
Layers (A) and (E) were composed of 30 parts by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation, trade name: Petrothene 225) having an MFR of 3.7 g/10 min and a density of 923 kg/m ³ , and 70 parts by weight of an ethylene-1-butene copolymer (manufactured by Tosoh Corporation, trade name: Nipolon-L08C52C) having an MFR of 2.4 g/10 min and a density of 920 kg/m ³ , and the resulting mixture was melt-kneaded at a resin temperature of 160°C in a single-screw extruder (manufactured by Placo Corporation, caliber 40 mm) to obtain a low-density polyethylene composition (A1) (MFR _PO 2.7 g/10 min, density 921 kg/m ³ , MS _PE 32 mN). Layers (B) and (D) were composed of acid-modified polypropylene (A1) having an MFR of 15.0 g/10 min at 230°C and a density of 900 kg/m 3. A polypropylene composition (B1) (MFR ADD 11.0 g/10 min, density 900 kg/m ³ , MAH content 0.12 wt %) obtained by blending ⁶⁰ parts by weight of polypropylene (trade name Novatec PP MG2T, manufactured by Japan Polypropylene Corporation) (B6) and 40 parts by weight of maleic anhydride graft-modified polypropylene (trade name Orevac G 18722, manufactured by SK Geo Centric Japan Co., Ltd.) (B4) having an MFR of 7.0 g/10 min at 230°C, a density of 900 kg/m ³ , and an MAH content of 0.30 wt % at 230°C in a resin temperature of 200°C in a single-screw extruder (manufactured by Placo Corporation, caliber 40 mm) was prepared. The resulting polypropylene composition (MFR _ADD 11.0 g/10 min, density 900 kg/m 3 , MAH content 0.12 wt %) was used as an ethylene-vinyl _alcohol copolymer constituting the (C) layer. An ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., product name EVAL SP482B) (C1) having 32 mol% of _EVOH , 1160 kg/ ^m3 of D _EVOH , and an MFR at 210°C of 4.1 g/ ¹⁰ min, and a paperboard (manufactured by Nippon Paper Industries Co., Ltd., uncoated cup base paper) having a basis weight of 300 g/m2 were used as the base layer.

First, (A1) was supplied to a single-screw extruder (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a screw with a diameter of 40 mm and set at 260°C, (B1) was supplied to a single-screw extruder (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a screw with a diameter of 40 mm and set at 260°C, and (C1) was supplied to a single-screw extruder (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.) having a screw with a diameter of 40 mm and set at 260°C. They were extruded through a T-die at a temperature of 260°C, and the extrusion speed was set to 50 m/min, and the extrusion rotation speed was set so that the thicknesses of (A1), (B1), (C1), (B1), and (A1) became 5 μm, 5 μm, 5 μm, 5 μm, and 5 μm, respectively, and migration was evaluated from the molten film produced. Next, a three-kind, five-layer extrusion laminate molding was started on a 25 μm thick PET film (manufactured by Toyobo Co., Ltd., product name Toyobo Polyester Film E5100) at a processing speed of 20 m/min and an air gap length of 110 mm so that (A1), (B1), (C1), (B1), and (A1) had thicknesses of 5 μm, 5 μm, 5 μm, 5 μm, and 5 μm, respectively, and the extrusion rotation speed and processing speed were increased in conjunction to evaluate the maximum processing speed. Then, immediately before the three-kind five-layer extrusion laminate molding, the adhesive surface with (A1) was subjected to corona treatment at a treatment strength of 31 W min / m ² on the paperboard, and (A1), (B1), (C1), (B1), (A1) were subjected to a processing speed of 50 m / min and an air gap length of 110 mm so that the thicknesses of (A1), (B1), (C1), (B1), and (A1) were 5 μm, 5 μm, 5 μm, 5 μm, respectively. Three-kind five-layer extrusion laminate molding was performed, and further, the three-kind five-layer film in a molten state immediately after extrusion from the T-die was subjected to ozone treatment at a treatment strength of 78 mg / m ² on the surface of the (A1) layer that adheres to the paperboard. A laminate was obtained in this order: paperboard, polyethylene (A1) ((E) layer), acid-modified polypropylene (B1) ((D) layer), ethylene-vinyl alcohol copolymer (C1) ((C) layer), acid-modified polypropylene (B1) ((B) layer), polyethylene (A1) ((A) layer). The obtained laminate was evaluated for adhesive strength, opening strength, and appearance after opening. The results are shown in Table 1.

Example 2
The acid-modified polypropylene constituting layers (B) and (D) was a polypropylene composition (B2) (MFR _ADD 13.0 g/10 min, density 900 kg/m 3 , MAH content 0.06 wt %) prepared by blending 80 parts by weight of polypropylene (B6) and 20 parts by weight of maleic anhydride graft-modified polypropylene (B4) and melt-kneading the mixture in a single-screw extruder (manufactured by Placo Corporation, diameter 40 mm) at a resin temperature of 200° ^C . Migration and maximum processing speed were evaluated in the same manner as in Example 1, and a laminate was then obtained. The adhesive strength, unsealing strength, and unsealed appearance of the resulting laminate were evaluated. The results are shown in Table 1.

Example 3
The acid-modified polypropylene constituting layers (B) and (D) was a polypropylene composition (B3) (MFR _ADD 8.0 g/10 min, density 900 kg/m3, MAH content 0.24 wt%) prepared by blending 20 parts by weight of polypropylene (B6) and 80 parts by weight of maleic anhydride graft-modified polypropylene (B4) and melt-kneading the mixture in ^a single-screw extruder (manufactured by Placo Corporation, diameter 40 mm) at a resin temperature of 200°C. Migration and maximum processing speed were evaluated in the same manner as in Example 1, and a laminate was then obtained. The resulting laminate was evaluated for adhesive strength, unsealing strength, and unsealed appearance. The results are shown in Table 1.

Example 4
The migration and maximum processing speed were evaluated in the same manner as in Example 1, except that maleic anhydride-grafted modified polypropylene (B4) was used as the acid-modified polypropylene constituting the (B) layer and the (D) layer, and then a laminate was obtained. The adhesive strength, opening strength, and opening appearance of the obtained laminate were evaluated. The results are shown in Table 1.

Example 5
The polyethylene constituting Layer (A) and Layer (E) was a low-density polyethylene composition (A2) (MFR PO 3.9 g/10 min, density 922 kg/m ³ , MS PO 33 mN) prepared by blending 30 parts by weight of a high-pressure low-density polyethylene (manufactured by Tosoh Corporation, product name Petrothene 225) having an MFR of 3.7 g/10 min and a density of 923 kg/m ³ and 70 parts by weight of a high-pressure low-density polyethylene (manufactured by Tosoh Corporation, product name Petrothene 190) having _{an MFR of} 4.0 g/10 min and a density of 922 kg/m ³ in a single-screw extruder (manufactured by Placo Corporation, _nozzle diameter 40 mm) at a resin temperature of 160°C. Migration and maximum processing speed were evaluated in the same manner as in Example 1, and a laminate was then obtained. The resulting laminate was evaluated for adhesive strength, unsealing strength, and unsealed appearance. The results are shown in Table 1.

Example 6
The polyethylene constituting Layer (A) and Layer (E) was a low-density polyethylene composition (MFR 3.0 g/10 min, density 910 kg/m ³⁾ obtained by blending 30 parts by weight of a high-pressure low-density polyethylene (manufactured by Tosoh Corporation, trade name: Petrothene 225) having an MFR of 3.7 g/10 min and a density of 923 kg/m ³ , 40 parts by weight of an ethylene/1-butene copolymer (manufactured by Tosoh Corporation, trade name: Nipolon-L08L52C) having an MFR of 2.4 g/10 min and a density of 920 kg/m ³ , and 30 parts by weight of an ethylene/1-butene copolymer (manufactured by Tosoh Corporation, trade name: Nipolon-L08L55B) having an MFR _of 3.5 g/10 min and a density of 885 kg/m ³ in a single-screw extruder (manufactured by Placo Corporation, caliber 40 mm) at a resin temperature of 160°C. The migration and maximum processing speed were evaluated in the same manner as in Example 1, except that MS _PE 31 mN (A3) was used, and then a laminate was obtained. The obtained laminate was used to evaluate the adhesive strength, opening strength, and opening appearance. The results are shown in Table 1.

Example 7
Except for the thickness of each of the (A) layer and the (E) layer being 3 μm, migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was used to evaluate adhesive strength, opening strength, and opening appearance. The results are shown in Table 1.

Example 8
Except for the thickness of each of the (A) layer and the (E) layer being 8 μm, migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was used to evaluate adhesive strength, opening strength, and opening appearance. The results are shown in Table 1.

Example 9
Except for the thickness of each of the (A) layer and the (E) layer being 15 μm, migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was used to evaluate adhesive strength, opening strength, and opening appearance. The results are shown in Table 1.

Example 10
A laminate was obtained after evaluating migration and maximum processing speed in the same manner as in Example 1, except that a high-pressure low-density polyethylene (Petrothene 225, product name, manufactured by Tosoh Corporation) (A4) having an MFR _PE of 3.7 g/10 min, a density of 923 kg/m ³ , and an MS _PE of 105 mN was used as the polyethylene constituting Layer (A) and Layer (E). The obtained laminate was evaluated for adhesive strength, opening strength, appearance after opening, and resealability. The results are shown in Table 2.

Example 11
A laminate was obtained after evaluating migration and maximum processing speed in the same manner as in Example 1, except that a high-pressure low-density polyethylene (Petrothene 212, product name, manufactured by Tosoh Corporation) (A5) having an MFR _PE of 13.0 g/10 min, a density of 919 kg/m ³ , and an MS _PE of 13 mN was used as the polyethylene constituting Layer (A) and Layer (E). The obtained laminate was evaluated for adhesive strength, opening strength, and appearance after opening. The results are shown in Table 2.

Example 12
The migration and maximum processing speed were evaluated in the same manner as in Example 1, except that an ethylene-vinyl alcohol _copolymer (manufactured by Mitsubishi Chemical Corporation, trade name G-Soarnol GC3304B ₎ (C2) having an MFR of 1.9 g/10 min for EVOH, 33 mol% for ^C2 , 1180 kg/m3 for D _EVOH , and an MFR of 4.0 g/10 min at 210°C was used as the ethylene-vinyl alcohol copolymer constituting Layer (C). The laminate was then obtained after evaluating the adhesive strength, opening strength, and appearance after opening using the obtained laminate. The results are shown in Table 2.

Example 13
The migration and maximum processing speed were evaluated in the same manner as in Example _{1, except that an ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., trade name EVAL F171B) (C3) having an MFR of 1.7 g/10 min for EVOH, 32 mol% for C2 ,} 1190 kg/ ^m3 for D _EVOH , and an MFR of 4.1 g/10 min at 210°C was used as the ethylene-vinyl alcohol copolymer constituting Layer (C). A laminate was then obtained after evaluating the migration and maximum processing speed in the same manner as in Example 1. The adhesive strength, opening strength, and appearance after opening were evaluated using the obtained laminate. The results are shown in Table 2.

Example 14
The acid-modified polypropylene constituting Layer (B) and Layer (D) was a polypropylene composition (MFR ADD 10.0 g/10 min, density 900 kg/m 3, MAH content 0.09 wt %) (B5) obtained by blending 60 parts by weight of polypropylene (B6) and 40 parts by weight of maleic anhydride graft-modified polypropylene (B4), and blending 30 parts by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation, trade name Petrothene 225) having an MFR of 3.7 g/10 min and a density of 923 kg/m ³ with a total of 100 parts by weight of polypropylene (B6) and maleic anhydride graft-modified polypropylene (B4). The polypropylene composition was melt-kneaded at a resin temperature of 200° ^C in a single-screw extruder (manufactured by Placo _Corporation , caliber 40 mm). Migration and maximum processing speed were evaluated in the same manner as in Example 1, and a laminate was then obtained. The obtained laminate was evaluated for adhesive strength, opening strength, and appearance after opening. The results are shown in Table 2.

Comparative Example 1
Except for using polypropylene (B6) as the acid-modified polypropylene constituting the (B) layer and the (D) layer, migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was evaluated for adhesive strength, opening strength, and opening appearance. The results are shown in Table 2. The opening appearance was poor.

Comparative Example 2
The acid-modified polypropylene constituting the (B) layer and the (D) layer was a polypropylene composition (MFR ADD 26.0 g/10 min, density 900 kg/m ³ , MAH content 0.30 wt %) obtained by blending 60 parts by weight of polypropylene (trade name Novatec PP MA1B, manufactured by Japan Polypropylene Corporation) having an MFR of 21 g/10 min at 230°C and a density of 900 kg/m ³ and 40 parts by weight of maleic anhydride-grafted polypropylene (trade name Orevac G 18751, manufactured by SK Geo Centric Japan Co., Ltd.) having an MFR of 35.0 g/10 min at 230°C, a density of 900 kg/m ³ , and an MAH content of 0.30 wt % and melt-kneading the mixture in a single-screw extruder (manufactured by Placo _Corporation , caliber 40 mm) at a resin temperature of 200°C. Except for using 0.12 wt%) (B7), migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was used to evaluate adhesive strength, opening strength, and opening appearance. The results are shown in Table 2. The film formation was unstable, and a sample could not be prepared.

Comparative Example 3
The polyethylene constituting Layer (A) and Layer (E) was a low-density polyethylene composition (MFR PE 3.6 g/10 min, density 896 kg/m ³ , MS PE 30 mN) (A6) prepared by blending 30 parts by weight of a high-pressure low-density polyethylene (manufactured by Tosoh Corporation, product name Petrothene 225) having an MFR of 3.7 g/10 min and a density of 923 kg/m ³ with 70 parts by weight of an ethylene-1-butene copolymer (manufactured by Tosoh Corporation, product name Nipolon-L08L55B) having an MFR _of 3.5 g/10 min and a density of 885 kg/m ³ and melt-kneading the mixture at a resin temperature of 160°C in a single-screw extruder (manufactured by Placo Corporation, _{nozzle diameter} 40 mm). Migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The resulting laminate was used to evaluate adhesive strength, opening strength, and opening appearance. The adhesive strength was high, but the ease of opening and appearance after opening were poor.

Comparative Example 4
Except for the thickness of the (A) layer and the (E) layer being 20 μm, migration and maximum processing speed were evaluated in the same manner as in Example 1, and then a laminate was obtained. The obtained laminate was evaluated for adhesive strength, opening strength, and opening appearance. The results are shown in Table 2. The opening appearance was poor.

The relationship between the ethylene content _C2 (mol%) and density _DEVOH (kg/ ^m3 ) of the ethylene-vinyl alcohol copolymer (c) described in the Examples is shown in Figure 1. As shown in this figure, Example 12, which satisfies formula (1) described in the specification, is superior in appearance upon opening and sealing properties to Example 13, which does not satisfy formula (1). Furthermore, Example 1, which satisfies formula (2), is even more superior in sealing properties.

The slopes of the formulas (1) and (2) were calculated using standard grade and semi-standard grade _C2 and D _EVOH of ethylene-vinyl alcohol copolymers manufactured by Kuraray. Specifically, an ethylene-vinyl alcohol copolymer having 27 mol% of _C2 and 1210 kg/ ^m3 of D _EVOH (trade name: EVAL L171B, manufactured by Kuraray Co., Ltd.), an ethylene-vinyl alcohol copolymer (C3) having 32 mol% of _C2 and 1190 kg/ ^m3 of D _EVOH , an ethylene-vinyl alcohol copolymer having 35 mol% of _{C2 and} 1180 kg/ ^m3 of D _EVOH (trade name: EVAL C109B, manufactured by Kuraray Co., Ltd.), an ethylene-vinyl alcohol copolymer having 38 mol% of _C2 and 1170 kg/ ^m3 of D _EVOH (trade name: EVAL H171B, manufactured by Kuraray Co., Ltd.), an ethylene-vinyl alcohol copolymer having 44 mol% of _C2 and 1140 kg/ ^m3 of D _EVOH (trade name: EVAL E105B, manufactured by Kuraray Co., Ltd.), an ethylene-vinyl alcohol copolymer having ₄₈ ...44 mol% The calculation was based on the correlation between _C2 and D _EVOH of an ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., trade name EVAL G156B) with an _EVOH content of 1120 kg/ ^m3 .

The easy-open properties of the present invention can be used for laminates that require adhesiveness, gas barrier properties, and ease of opening, and are particularly suitable for use in laminates used as packaging materials for foods, beverages, pharmaceuticals, etc.

Claims (8)

An easily openable laminate comprising at least a base layer and a (C) layer/(B) layer/(A) layer adjacent to each other from the base layer side, wherein the (A) layer is composed of polyethylene (a), the (B) layer is composed of acid-modified polypropylene (b) that satisfies (i) to (ii), and the (C) layer is composed of an ethylene-vinyl alcohol copolymer (c) that satisfies (iii), and the laminate satisfies (iv) to (v).
(i) A melt mass flow rate (MFR _ADD ) at 230°C measured according to JIS 7210 (1999) is 2.0 g/10 min or more and 20.0 g/10 min or less. (ii) An acid content is 0.02 wt% or more and 1.0 wt% or less. (iii) An ethylene content _C2 is 50 mol% or less. (iv) A thickness of the (A) layer is 1 μm or more and 15 μm or less. (v) An adhesive strength between the (A) layer and the (B) layer is 0.1 N/15 mm or more and 3.0 N/15 mm or less. The easy-open laminate according to claim 1, wherein the acid content of the acid-modified polypropylene (b) is 0.05% by weight or more and 0.40% by weight or less. The easy-open laminate according to claim 1 or 2, wherein the acid-modified polypropylene (b) is maleic anhydride-grafted modified polypropylene. The easy-open laminate according to any one of claims 1 to 3, wherein the polyethylene (a) satisfies (vi) to (viii).
(vi) the melt mass flow rate (MFR _PE ) measured according to JIS K6922-1 (1997) is 1.0 g/10 min or more and 10.0 g/10 min or less; (vii) the melt tension (MS _PE ) measured at a temperature of 190°C and a take-up speed of 10 m/min is 3 mN or more and 50 mN or less; and (viii) the product MFR _PE (g/10 min) and MS _PE (mN), MFR _PE × MS _PE , is 70 or more and 250 or less. The easy-open laminate according to any one of claims 1 to 4, wherein the polyethylene (a) comprises an ethylene-α-olefin copolymer and/or a high-pressure low-density polyethylene. The easy-open laminate according to any one of claims 1 to 5, wherein C ₂ (mol %) of the ethylene-vinyl alcohol copolymer (c) and a density D _EVOH (kg/m ³ ) at 20°C measured according to ISO1183-3 satisfy the following formula (1):
D _EVOH <-4.265×C ₂ +1325 (1) The easy-open laminate according to any one of claims 1 to 6, further comprising an (E) layer/(D) layer between the base layer and the (C) layer, the (E) layer being adjacent to the base layer, the (D) layer being adjacent to the (C) layer, the (E) layer being polyethylene (e), and the (D) layer being acid-modified polypropylene (d). The method for producing an easy-open laminate according to any one of claims 1 to 7, wherein the (C) layer/(B) layer/(A) layer or the (E) layer/(D) layer/(C) layer/(B) layer/(A) layer are simultaneously formed by co-extrusion lamination molding.