Laminate and packaging bag

Abstract

The present invention provides: a laminate in which delamination can be suppressed even in mono-material container packaging constituted of a polyethylene-based resin layer containing a polyethylene-based resin as a single resin; and a packaging bag formed from said laminate. More specifically, the present invention is a laminate 10 comprising at least two polyethylene-based resin layers 11, 12, and adhesive layers 13 respectively provided between the polyethylene-based resin layers 11, 12. At least one of the adhesive layers 13 has a hardness of 0.2 GPa or greater, and at least one of the two polyethylene-based resin layers 11, 12 from among the two polyethylene layers 11, 12 that are adjacent to the adhesive layer 13 having a hardness of 0.2 GPa or greater has a hardness of 0.07 GPa or greater.

Description

Laminates and packaging bags

[0001] This invention relates to laminates and packaging bags.

[0002] Paragraph 0010 of Patent Document 1 describes a laminated film, which has been conventionally used for packaging bags, in which a polyolefin resin such as low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or polypropylene is laminated as a sealant to a base film such as biaxially oriented polypropylene, biaxially oriented polyamide, or biaxially oriented polyester. Furthermore, dry lamination, extrusion lamination, and co-extrusion are given as examples of methods for manufacturing the laminated film.

[0003] Japanese Patent Application Publication No. 2013-039932

[0004] To facilitate recycling, monomaterial containers and packaging using a single resin have been proposed. Polyethylene resins are inexpensive and easy to process as a single resin, but they have the problem of being prone to delamination (exfoliation) in the interlayer adhesive of polyethylene resin layers.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a laminate that can suppress delamination even in monomaterial container packaging consisting of a polyethylene resin layer containing a polyethylene resin as a single resin, and a packaging bag formed from said laminate.

[0006] To solve the above problems, the present invention has the following configuration: [1] A laminate having at least two polyethylene resin layers and adhesive layers provided between each of the at least two polyethylene resin layers, wherein at least one of the adhesive layers has a hardness of 0.2 GPa or more, and at least one of the two polyethylene resin layers adjacent to the adhesive layer having a hardness of 0.2 GPa or more has a hardness of 0.07 GPa or more. [2] A laminate having at least a base layer, an intermediate layer, and a sealant, wherein at least two of the base layer, the intermediate layer, and the sealant are polyethylene resin layers, and the laminate has, as adhesive layers, a first adhesive layer between the base layer and the intermediate layer, and a second adhesive layer between the intermediate layer and the sealant, wherein at least one of the adhesive layers has a hardness of 0.2 GPa or more, and at least one of the two polyethylene resin layers adjacent to the adhesive layer having a hardness of 0.2 GPa or more has a hardness of 0.07 GPa or more. [3] The laminate according to [1] or [2], wherein the adhesive layer having a hardness of 0.2 GPa or more includes at least one selected from epoxy adhesives or urethane adhesives. [4] A packaging bag formed using the laminate according to any one of [1] to [3].

[0007] According to the present invention, delamination can be suppressed in a monomaterial packaging bag formed from a laminate having a polyethylene resin layer containing a polyethylene resin as a single resin.

[0008] This is a cross-sectional view showing a laminate according to a first embodiment that can be used for packaging bags. This is a cross-sectional view showing a laminate according to a second embodiment that can be used for packaging bags. This is a front view illustrating a packaging bag.

[0009] The present invention will be described below based on preferred embodiments.

[0010] Figures 1 and 2 are cross-sectional views illustrating laminates that can be used in packaging bags according to this embodiment. The laminate 10 according to the first embodiment shown in Figure 1 has two polyethylene resin layers 11 and 12 and an adhesive layer 13 provided between the layers. The number of polyethylene resin layers 11 and 12 included in the laminate 10 is not limited to two layers, but may be three or more layers.

[0011] The laminate 20 according to the second embodiment shown in Figure 2 comprises a base layer 21, an adhesive layer 24, an intermediate layer 22, an adhesive layer 25, and a sealant 23. At least two of the base layer 21, the intermediate layer 22, and the sealant 23 are polyethylene resin layers. The adhesive layer 24 is a first adhesive layer between the base layer 21 and the intermediate layer 22. The adhesive layer 25 is a second adhesive layer between the intermediate layer 22 and the sealant 23.

[0012] In the laminate 10 according to the first embodiment, the adhesive layer 13 provided between the two polyethylene resin layers 11 and 12 has a hardness of 0.2 GPa or more. In the laminate 20 according to the second embodiment, at least one of the adhesive layers 24 provided between the base layer 21 and the intermediate layer 22, and the adhesive layer 25 provided between the intermediate layer 22 and the sealant 23, has a hardness of 0.2 GPa or more. In the following description, an adhesive layer having a hardness of 0.2 GPa or more may be referred to as a "Type 1 adhesive layer," and an adhesive layer having a hardness of less than 0.2 GPa may be referred to as a "Type 2 adhesive layer."

[0013] As shown in Figure 1, in a laminate 10 having two polyethylene resin layers 11 and 12, the adhesive layer 13 between the layers is a Type 1 adhesive layer. As shown in Figure 2, in a laminate 20 having two or more adhesive layers 24 and 25, at least one of the adhesive layers 24 and 25 is a Type 1 adhesive layer. In the laminate 20, if adhesive layer 24 is a Type 1 adhesive layer, adhesive layer 25 may be a Type 2 adhesive layer. If adhesive layer 25 is a Type 1 adhesive layer, adhesive layer 24 may be a Type 2 adhesive layer. Two or more adhesive layers 24 and 25 may be Type 1 adhesive layers.

[0014] The adhesive included in the first adhesive layer may be, for example, at least one selected from epoxy adhesives or urethane adhesives. The hardness of the first adhesive layer may be, for example, within a range where two different values ​​are arbitrarily selected from the group consisting of 0.2 GPa, 0.25 GPa, 0.3 GPa, 0.35 GPa, 0.4 GPa, 0.45 GPa, and 0.5 GPa, with the larger value being the upper limit and the smaller value being the lower limit.

[0015] In the laminates 10 and 20 usable for packaging bags of this embodiment, at least one of the two polyethylene resin layers adjacent to the first adhesive layer has a hardness of 0.07 GPa or more. This suppresses delamination of the laminate used in packaging bags. In the following description, the polyethylene resin layer having a hardness of 0.07 GPa or more may be referred to as the "first PE layer," and the polyethylene resin layer having a hardness of less than 0.07 GPa may be referred to as the "second PE layer." These polyethylene resin layers 11 and 12 may be polyethylene resin films that have been pre-formed before bonding with the adhesive layers 13, 24, and 25. The polyethylene resin film may be either a stretched resin film or an unstretched resin film, as will be described in detail later.

[0016] As shown in Figure 1, in a laminate 10 having two polyethylene resin layers 11 and 12, at least one of the polyethylene resin layers 11 and 12 is a Type 1 PE layer. As shown in Figure 2, when the laminate 20 has two or more adhesive layers 24 and 25, the hardness of the two polyethylene resin layers adjacent to the Type 1 adhesive layer is taken into consideration. The Type 2 adhesive layer may be adjacent to either the Type 1 PE layer or the Type 2 PE layer.

[0017] If adhesive layer 24 is a Type 1 adhesive layer, then at least one of the polyethylene resin layers (base layer 21 or intermediate layer 22) adjacent to adhesive layer 24 is a Type 1 PE layer. If adhesive layer 25 is a Type 1 adhesive layer, then at least one of the polyethylene resin layers (intermediate layer 22 or sealant 23) adjacent to adhesive layer 25 is a Type 1 PE layer. If both adhesive layers 24 and 25 are Type 1 adhesive layers, then at least one of the polyethylene resin layer (intermediate layer 22) or other polyethylene resin layers (base layer 21 and sealant 23) between them is a Type 1 PE layer.

[0018] If the sealant 23 is a Type 2 PE layer, then at least one of the polyethylene resin layers other than the sealant 23 (base layer 21 or intermediate layer 22) adjacent to the Type 1 adhesive layer is a Type 1 PE layer. The laminates 10 and 20 of this embodiment do not have a structure (Type 2 PE layer / Type 1 adhesive layer / Type 2 PE layer) that bonds two Type 2 PE layers via a Type 1 adhesive layer.

[0019] The hardness of the polyethylene resin layer may be, for example, in the range of 0.02 to 0.25 GPa, and within that range, it may be within the range where two different values ​​are arbitrarily selected from the group consisting of 0.02 GPa, 0.025 GPa, 0.03 GPa, 0.04 GPa, 0.05 GPa, 0.06 GPa, 0.07 GPa, 0.08 GPa, 0.09 GPa, 0.1 GPa, 0.15 GPa, 0.2 GPa, with the larger value being the upper limit and the smaller value being the lower limit.

[0020] The hardness of the first type PE layer described above is exemplified by a range of 0.07 to 0.25 GPa, and within that range, it may be a range where two different values ​​are arbitrarily selected from the group consisting of 0.07 GPa, 0.08 GPa, 0.09 GPa, 0.1 GPa, 0.15 GPa, 0.2 GPa, and 0.25 GPa, with the larger value being the upper limit and the smaller value being the lower limit.

[0021] The hardness of the Type 2 PE layer described above is exemplified by a range of 0.02 GPa or more and less than 0.07 GPa, and within that range, it may be a range where two different values ​​are arbitrarily selected from the group consisting of 0.02 GPa, 0.025 GPa, 0.03 GPa, 0.04 GPa, 0.05 GPa, 0.06 GPa, and 0.065 GPa, with the larger value being the upper limit and the smaller value being the lower limit.

[0022] The hardness (GPa) of the adhesive layer and the polyethylene resin layer can be measured, for example, by an indentation test using a nanoindenter (see, for example, ISO 14577). A predetermined indenter is pressed into the surface of each layer, and the hardness can be calculated from the relationship between the load applied from the indenter to the surface of each layer and the displacement (depth) of the indenter (load-displacement curve).

[0023] Of the adhesive layers 13, 24, and 25, the first type adhesive layer may be selected from adhesives suitable for applications requiring a hard and dense film, such as gas barrier properties. The first type PE layer may be selected from resin films suitable for applications requiring mechanical strength, such as transportability, such as stretched resin films or relatively high-density resin films.

[0024] Of the adhesive layers 13, 24, and 25, the second adhesive layer can be constructed by applying an appropriate adhesive, and a general-purpose adhesive may also be used. Specific examples of these adhesives include urethane adhesives, epoxy adhesives, isocyanate adhesives, polyethyleneimine, and organic titanium compounds such as titanium alkoxide. Extruded resin can also be used as the adhesive, and the second adhesive layer may be an extruded polyethylene layer. A polyethylene resin is preferred as the extruded resin, but a polyethylene adhesive resin may also be used. If the extruded resin is a polyethylene resin, it may have a hardness of less than 0.02 GPa, for example, or 0.005 GPa or more and less than 0.02 GPa.

[0025] The thickness of the adhesive layers 13, 24, and 25 applied by coating can be, for example, about 0.1 to 10 μm, about 1 to 6 μm, and about 3 to 4 μm. Lamination of polyethylene resin layers in laminates 10 and 20 via adhesive layers 13, 24, and 25 can be carried out, for example, by a dry lamination method. Examples of adhesive compositions when the adhesive is applied include organic solvent type, aqueous solvent type, and solvent-free type. Examples of adhesive layers using extruded resin can be, for example, about 3 to 30 μm, about 5 to 25 μm, and about 7 to 20 μm.

[0026] Epoxy adhesives are adhesives that provide an adhesive film obtained by curing a compound containing epoxy groups. Examples of epoxy adhesives include compositions containing at least an epoxy main component. The epoxy main component is not particularly limited, but examples include compounds (low molecular weight epoxy compounds) having epoxy groups in various molecules such as aromatic compounds, aliphatic compounds, alicyclic compounds, and heterocyclic compounds. Alternatively, epoxy group-containing copolymers (high molecular weight epoxy compounds) containing epoxy group-containing vinyl monomers may also be used as the epoxy main component.

[0027] Specific examples of epoxy-based main components include bisphenol-type epoxy resins, novolac-type epoxy resins, glycidylamine-type epoxy resins, glycidyl ether-type epoxy resins, glycidyl ester-type epoxy resins, modified epoxy resins, and triglycidyl isocyanurate. Examples of epoxy group-containing vinyl monomers include glycidyl esters such as glycidyl (meth)acrylate, glycidyl ethers such as allyl glycidyl ether, and epoxy alkenes such as epoxy butene. Examples of comonomers for epoxy group-containing copolymers include olefins such as ethylene and propylene, acrylic monomers such as (meth)acrylic acid esters, and vinyl monomers such as vinyl acetate.

[0028] A curing agent may be used with epoxy adhesives. Examples of curing agents include amine-based curing agents, acid anhydride-based curing agents, imidazole compounds, and amide-based curing agents. Examples of amine-based curing agents include primary amines, secondary amines, tertiary amines, aliphatic amines, and aromatic amines. Examples of acid anhydride-based curing agents include aromatic acid anhydrides, aliphatic acid anhydrides, and alicyclic acid anhydrides. Imidazole compounds may have substituents such as alkyl groups, or they may be salts such as carboxylate salts.

[0029] Urethane adhesives are adhesives that provide an adhesive film containing urethane bonds (-O-CO-NH-) formed by the reaction of a hydroxyl group (-OH) and an isocyanate group (-NCO). In addition to urethane bonds, the adhesive film formed from a urethane adhesive may also contain various functional groups derived from the dimerization or trimerization of isocyanate groups, or from the reaction of isocyanate groups with active hydrogen groups (hydroxyl groups, amino groups, etc.).

[0030] Specific examples of urethane adhesives include two-component urethane adhesives that use a compound having a hydroxyl group (active hydrogen group), such as a polyol compound, as the main component and an isocyanate compound as the curing agent; and one-component urethane adhesives that contain a polyurethane precursor or prepolymer. Examples of polyol compounds include polyester polyols, polyether polyols, acrylic polyols, and urethane-modified polyols. Examples of isocyanate compounds include compounds having isocyanate groups in various molecules, such as aromatic compounds, aliphatic compounds, alicyclic compounds, and heterocyclic compounds.

[0031] The base layer 21 and the intermediate layer 22 may be stretched polyethylene resin layers or unstretched polyethylene resin layers. Examples of materials for the base layer 21 and the intermediate layer 22 include relatively high-density polyethylene resins such as medium-density polyethylene (MDPE) and high-density polyethylene (HDPE). The base layer 21 or the intermediate layer 22 may be formed from one type of polyethylene resin or may be a resin layer containing two or more types of polyethylene resins. The thickness of the base layer 21 or the intermediate layer 22 is not particularly limited, but examples include about 10 to 50 μm.

[0032] The sealant 23 may be a single-layer sealant layer or a multi-layer sealant layer. Examples of materials for the sealant 23 include relatively low-density polyethylene resins such as linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), or unstretched polyethylene resins. The sealant 23 may be formed from one type of polyethylene resin, or it may be a resin layer containing two or more types of polyethylene resins. The thickness of the sealant 23 is not particularly limited, but for example, it may be about 50 to 180 μm.

[0033] As shown in Figure 1, if the laminate 10 has two polyethylene resin layers 11 and 12, one of the polyethylene resin layers 11 and 12 may be a sealant, and the other layer may be a base layer (a polyethylene resin layer other than a sealant). As shown in Figure 2, if the laminate 20 has a base layer 21 and an intermediate layer 22, the base layer 21 and the intermediate layer 22 may be the same type of polyethylene resin layer, or the base layer 21 and the intermediate layer 22 may be different polyethylene resin layers.

[0034] The sealant is used for bonding inner surfaces of a laminate when manufacturing a packaging bag from the laminate. That is, the sealant is the innermost layer of the laminate. The base material layer may be the outermost layer of the laminate, but a thin layer that is not a polyethylene-based resin layer, such as a printing layer, a coating layer, or a vapor deposition layer, may be included on the outer side of the base material layer. When the laminate includes three or more polyethylene-based resin layers, the intermediate layer is a polyethylene-based resin layer that is neither the innermost layer nor the outermost layer among the three or more polyethylene-based resin layers and is located in the middle in the thickness direction.

[0035] The base material layer or the intermediate layer may be formed from a uniaxially or biaxially stretched polyethylene-based resin film. Although the stretching direction is not particularly limited, stretching may be performed in the machine direction (MD) and / or the transverse direction (TD). The stretching ratio is preferably in the range of 2 to 10 times in both the MD direction and the TD direction. The stretching ratio in the MD direction and the stretching ratio in the TD direction may be equal to or different from each other.

[0036] When the intermediate layer adjacent to the sealant is a biaxially stretched polyethylene-based resin film, good hand tearability can be obtained. Furthermore, when a base material layer made of a uniaxially stretched polyethylene-based resin film is laminated on the outer side of the intermediate layer, tearing along the stretching direction is facilitated, and straight cutting performance can be improved.

[0037] The polyethylene-based resin used for the polyethylene-based resin layers of the laminates 10 and 20 may be a homopolymer of ethylene, or a copolymer mainly composed of ethylene. Examples of monomers (comonomers) other than ethylene include one or more selected from α-olefins such as 1-butene, 1-hexene and 1-octene, cyclic olefins such as norbornene, and vinyl monomers such as vinyl acetate, vinyl chloride and acrylic acid. When a comonomer is used in the polyethylene-based resin, one or two or more comonomers may be used.

[0038] The polyethylene-based resin used for the polyethylene-based resin layer of the laminates 10 and 20 preferably contains 50% by weight or more of ethylene among constituent monomers, and may contain, for example, 80 to 100% by weight of ethylene. Ethylene or a comonomer used for the polyethylene-based resin may be a compound derived from a fossil resource such as petroleum, or may be a compound derived from biomass such as plants. The resin contained in the polyethylene-based resin layer may consist of only the polyethylene-based resin. A material forming the polyethylene-based resin layer may be one type of polyethylene-based resin, or may be a blend of two or more types of polyethylene-based resins.

[0039] The polyethylene-based resin layer may contain recycled polyethylene. The recycled polyethylene may be a chemically recycled resin obtained by decomposing a used polyethylene-based resin into monomers such as ethylene and then polymerizing the decomposed product again, or may be a mechanically recycled resin obtained by regenerating a used polyethylene-based resin in the form of a polymer through steps such as pulverization and sorting. Recycled polyethylene may be used by being mixed or laminated with a virgin polyethylene-based resin.

[0040] The resin contained in the polyethylene-based resin layer of the laminates 10 and 20 may consist of only the polyethylene-based resin. The polyethylene-based resin layer may contain a resin other than the polyethylene-based resin. It is desirable that the content of the polyethylene-based resin in the entire laminates 10 and 20 is not less than a predetermined ratio. The predetermined ratio of the polyethylene-based resin is, for example, preferably 80% by weight or more, and may be 90 to 100% by weight.

[0041] The polyethylene-based resin layer of the laminates 10 and 20 may contain additives other than resins as optional components. The additives are not particularly limited, and examples thereof include antioxidants, lubricants, antiblocking agents, flame retardants, ultraviolet absorbers, light stabilizers, antistatic agents, colorants (pigments, dyes, etc.), crosslinking agents, inorganic fillers, wood flour and the like. The additive may be a component compatible with the resin, or may be a component incompatible with the resin.

[0042] As described above, for example, a printed layer, a coating layer, a vapor deposited layer or the like may be provided as a layer other than the polyethylene-based resin layer of the laminates 10 and 20.

[0043] The printed layer may be formed on the outer or inner surface of the substrate layer or intermediate layer. The printed layer may be formed from solvent-containing ink or from solvent-free ink. The printed layer may include a solid print layer covering an area equivalent to that of the polyethylene resin layer, or it may include a pattern print layer covering a portion of the area of ​​the polyethylene resin layer. The pattern print layer may cover a predetermined area with a geometric shape such as a polygon, or it may be formed only on predetermined characters, symbols, figures, patterns, dots, stripes, etc.

[0044] The coating layer may be formed from a functional resin such as a barrier resin or a heat-resistant resin. The vapor-deposited layer may be formed from a metal such as aluminum, or a metal oxide (inorganic compound) such as silica or alumina. The coating layer or vapor-deposited layer may be formed on the outer surface, inner surface, or both sides of a polyethylene-based resin layer other than a sealant (substrate layer or intermediate layer).

[0045] The laminates 10 and 20 of the embodiment can be used to manufacture packaging bags. The use of the packaging bags is not particularly limited and can be for disposable use, refilling, storage, or for storing goods. It is particularly suitable for use in refilling a main container with contents once or multiple times, which is used when the contents are consumed. In this case, the main container can be made durable for long-term use, the packaging of the refill container can be simplified, and recycling of the refill container after the contents have been used up can be easily done.

[0046] Examples of packaging bag forms include three-side sealed bags, four-side sealed bags, pillow bags, gusset bags, and standing pouches. The packaging bag 100 illustrated in Figure 3 has a pair of body members 101 and a bottom member 102 that is folded in half along a fold line 103. The bottom member 102 is sandwiched between the body members 101. Above the fold line 103, the front and rear body members 101 are joined via the left and right body seal portions 104. Below the fold line 103, the bottom member 102 is joined to the body members 101 via the bottom seal portion 105. The configuration of the bottom member 102 is not limited to laminates 10 and 20 and can be any configuration. Although not specifically shown, in the case of flat bags such as three-side sealed bags and four-side sealed bags, the bottom member 102 can be omitted, and the packaging bag can be made with only the pair of body members 101.

[0047] The packaging bag may have a filling opening, a dispensing opening, etc. For example, the top of the packaging bag may have an opening between the front and rear body members, which can be used for filling or dispensing the contents. In the packaging bag 100 shown in Figure 3, a space for storing contents is formed from the unsealed portion secured between the left and right body seal portions 104, and the top of the storage space is open to form a filling opening. The filling opening is closed after the contents are filled via a seal portion (not shown).

[0048] Although not specifically shown in the illustrations, if the packaging bag has a spout, the spout may be formed from a film such as a body member, or from a molded product such as a spout. In the case of a film-molded spout, the spout formed from the body member may be formed in a shape that protrudes thinly from the top or corner of the packaging bag. In the case of a spout made from a molded product such as a spout, the molded product such as a spout may be fixed between a pair of body members.

[0049] It is preferable that the portion for opening or tearing the packaging bag is formed in the film of the body member or the like. The portion for opening or tearing may have a structure processed in the thickness direction of the film, such as perforations, notches, or half-cut grooves, or it may have a shape that suggests opening or tearing within the surface of the film, such as a thinly protruding spout, or it may be indicated by arrows, lines, dots, etc., printed on it.

[0050] The dimensions of the packaging bag are not particularly limited, but for example, for use as a refillable container, the height in the vertical direction is about 100-500 mm, the width in the horizontal direction is about 70-300 mm, and the filling volume is about 100 cm. ３ ~5000cm ３ The degree can be mentioned. The state of the contents can be fluids such as liquids, powders, and granules. The type of contents is not particularly limited, but examples include detergents, chemicals, cosmetics, pharmaceuticals, beverages, seasonings, inks, paints, and fuels.

[0051] The present invention will be described in more detail below as examples, but it is not limited to these examples.

[0052] Laminates were fabricated with the configurations shown in Tables 1-4. Among the adhesive layers (AD), "rigid AD" represents a Type 1 adhesive layer with a hardness of 0.2 GPa or higher, "general-purpose AD" represents a coating-curing type adhesive layer among the Type 2 adhesive layers with a hardness of less than 0.2 GPa, and "extruded PE" represents an extruded PE resin among the Type 2 adhesive layers. The "base layer," "intermediate layer," and "sealant" are all made of polyethylene (PE) resin film.

[0053] The following materials were used as adhesives. Rigid AD has oxygen barrier properties. Epoxy adhesive-1: Hardness 0.33 GPa (Rigid AD1) Urethane adhesive-1: Hardness 0.26 GPa (Rigid AD2) Urethane adhesive-2: Hardness 0.34 GPa (Rigid AD3) Urethane adhesive-3: Hardness 0.39 GPa (Rigid AD4) Urethane adhesive-4: Hardness 0.46 GPa (Rigid AD5) General-purpose adhesive: Hardness 0.025 GPa (General-purpose AD) Extruded polyethylene: Hardness 0.018 GPa (Extruded PE)

[0054] The following polyethylene resin was used. The melting point was measured using the heat flux DSC method according to JIS K 7121 at a heating rate of 10°C / min. Polyethylene resin film-1 (PE1): hardness 0.028 GPa, melting point 103°C, density 0.9162 g / cm³ ３ 60 μm thick, unstretched (Type 2 PE layer) Polyethylene resin film-2 (PE2): Hardness 0.055 GPa, melting point 126°C, density 0.936 g / cm³３ , Polyethylene resin film-3 (PE3): thickness 25 μm, biaxially stretched (type 2 PE layer), hardness 0.08 GPa, melting point 132°C, density 0.956 g / cm ３ , Polyethylene resin film-4 (PE4): thickness 30 μm, biaxially stretched (type 1 PE layer), hardness 0.11 GPa, melting point 132°C, density 0.947 g / cm ３ , Polyethylene resin film-5 (PE5): thickness 25 μm, biaxially stretched (type 1 PE layer), hardness 0.157 GPa, melting point 133°C, density 0.95 g / cm ３ , Polyethylene resin film-6 (PE6): thickness 25 μm, uniaxially stretched (type 1 PE layer), hardness 0.191 GPa, melting point 130°C, density 0.95 g / cm ３ , Non-stretched polyethylene resin film (sealant) (type 1 PE layer): thickness 25 μm, hardness 0.033 GPa, melting point 114°C, density 0.918 g / cm ３ , Thickness 150 μm, non-stretched (type 2 PE layer)

[0055] Similar to the laminate 20 shown in FIG. 2, the configurations shown in Tables 1 to 4 are basically laminates stacked in the order of "base material layer / first adhesive layer / intermediate layer / second adhesive layer / sealant". A configuration of "base material layer / hard AD / intermediate layer / general-purpose AD / sealant" in order from the top indicates that the first adhesive layer is hard AD and the second adhesive layer is general-purpose AD. A configuration of "base material layer / general-purpose AD / intermediate layer / hard AD / sealant" in order from the top indicates that the first adhesive layer is general-purpose AD and the second adhesive layer is hard AD. A configuration of "base material layer / hard AD / intermediate layer / extruded PE / sealant" in order from the top indicates that the first adhesive layer is hard AD and the second adhesive layer is extruded PE.

[0056] A configuration consisting of "base layer / printed layer / hard adhesive / intermediate layer / general-purpose adhesive / sealant" from top to bottom indicates that the base layer has a printed layer (not shown) on its inner surface (between the base layer and the first adhesive layer). A configuration consisting of "base layer / printed layer / general-purpose adhesive / intermediate layer / general-purpose adhesive / sealant" from top to bottom indicates that the first and second adhesive layers are general-purpose adhesives, and the base layer has a printed layer (not shown) on its inner surface (between the base layer and the first adhesive layer).

[0057] In Tables 1-4, the hardness (GPa) of the substrate layer, first adhesive layer, intermediate layer, second adhesive layer, and sealant was measured in accordance with ISO 14577 by nanoindentation using a Berkovich-type diamond indenter with a nanoindenter. The hardness of the adhesive layer can be measured after the adhesive has cured, and this measurement is not limited to cases where the adhesive is cured between layers; it may also be cured with one side of the adhesive in contact with air.

[0058] Delamining was evaluated using the following method. [Sample conditions] Packaging bag size: 150 mm wide x 200 mm high Packaging bag type: Four-sided sealed bag Packaging bag contents: Water Packaging bag volume: 400 g Packaging bag condition: Cooled at 5°C [Evaluation conditions] Drop height: 1.5 m Number of times: 20 vertical drops [Judgment] ○: No separation between layers (no delamination). ×: Separation between layers (delamination occurs).

[0059] Barrier assessment is performed by measuring oxygen permeability (cm²) using the following method. ３ / m ２ The day-atm was evaluated. One day corresponds to 24 hours, and 1 atm corresponds to 101325 Pa. [Evaluation conditions] Temperature 30°C, humidity 70% RH [Judgment] ○: Oxygen permeability is 350 (cm ３ / m ２ It is less than 350 (cm²) of the day atm. ×: Oxygen permeability is 350 (cm²). ３ / m ２ It exceeds the daily ATM limit.

[0060]

[0061]

[0062]

[0063]

[0064] The laminates and packaging bags of Examples 1 to 12 were able to suppress delamination even in monomaterial container packaging, and also exhibited high barrier properties.

[0065] Although the laminate and packaging bag of Comparative Example 1 had a hardness of 0.2 GPa or more in the second adhesive layer, the two polyethylene resin layers adjacent to the second adhesive layer (intermediate layer and sealant) both had a hardness of less than 0.07 GPa, and therefore, delamination could not be suppressed.

[0066] In Comparative Example 2, both the first and second adhesive layers of the laminate and packaging bag had a hardness of less than 0.2 GPa, making it impossible to suppress delamination, and because they were made of general-purpose adhesives, their barrier properties were poor.

[0067] 10, 20... Laminate, 11, 12... Polyethylene resin layer, 13, 24, 25... Adhesive layer, 21... Base material layer, 22... Intermediate layer, 23... Sealant, 100... Packaging bag, 101... Body member, 102... Bottom member, 103... Fold line, 104... Body seal part, 105... Bottom seal part.

Claims

A laminate comprising at least two polyethylene resin layers and adhesive layers provided between each of the at least two polyethylene resin layers, At least one of the adhesive layers has a hardness of 0.2 GPa or more. A laminate characterized in that, of the two polyethylene resin layers adjacent to the adhesive layer having a hardness of 0.2 GPa or more, at least one of the polyethylene resin layers has a hardness of 0.07 GPa or more. 　 A laminate comprising at least a base layer, an intermediate layer, and a sealant, At least two of the base layer, the intermediate layer, and the sealant are polyethylene resin layers. The laminate has, as adhesive layers, a first adhesive layer between the base layer and the intermediate layer, and a second adhesive layer between the intermediate layer and the sealant, At least one of the adhesive layers has a hardness of 0.2 GPa or more. A laminate characterized in that, of the two polyethylene resin layers adjacent to the adhesive layer having a hardness of 0.2 GPa or more, at least one of the polyethylene resin layers has a hardness of 0.07 GPa or more. 　 The laminate according to claim 1 or 2, characterized in that the adhesive layer having a hardness of 0.2 GPa or more includes at least one selected from epoxy adhesives or urethane adhesives. 　 A packaging bag formed using the laminate described in any one of claims 1 to 3.

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