JP2022165191A - Laminate and packaging material - Google Patents

Abstract

To provide a laminate that has strength, heat sealability, and recyclability, and can be suitably used as a packaging material.SOLUTION: A laminate includes a base material and a heat seal layer, in which the base material and the heat seal layer are made of the same resin materials, the base material has a multilayer structure, the base material is a base material subjected to drawing processing, and the heat seal layer is a layer not subjected to drawing processing.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to laminates and packaging materials.

Conventionally, packaging materials and the like are manufactured using resin films made of resin materials. The packaging material comprises, for example, a substrate and a heat seal layer. For example, a resin film made of polyolefin is used as a heat-sealing layer in packaging materials because it has appropriate flexibility and transparency and excellent heat-sealing properties.

In general, resin films made of polyolefin are inferior in terms of strength and heat resistance, so they cannot be used as base materials for constituting packaging materials, etc. As base materials for packaging materials, polyester films and polyamide films are used. It is common to use a resin film that is excellent in strength and heat resistance such as. Therefore, different types of resin films are used for the substrate and the heat seal layer in ordinary packaging materials (see, for example, Patent Document 1).

JP 2009-202519 A

In recent years, attempts have been made to recycle and use packaging materials, along with growing calls for building a recycling-oriented society. However, it is difficult to separate each type of resin material in a laminate including two or more different types of resin films as described above, and it is not suitable for recycling.

The problem to be solved by the present disclosure is to provide a laminate that has strength, heat-sealability and recyclability and can be suitably used as a packaging material, and a packaging material comprising the laminate.

The laminate of the present disclosure includes a substrate and a heat-sealing layer, the substrate and the heat-sealing layer are made of the same type of resin material, the substrate has a multilayer structure, and the substrate is , the base material subjected to the stretching treatment, and the heat-sealing layer is the layer not subjected to the stretching treatment.

A packaging material of the present disclosure includes the laminate described above.

According to the present disclosure, it is possible to provide a laminate that has strength, heat sealability, and recyclability and can be suitably used as a packaging material, and a packaging material comprising the laminate.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the laminate of the present disclosure. FIG. 2 is a cross-sectional schematic diagram illustrating one embodiment of the laminate of the present disclosure.

[Laminate]
A laminate of the present disclosure comprises a substrate and a heat seal layer.
In the laminate of the present disclosure, the substrate and the heat seal layer are made of the same resin material. That is, the base material is made of a resin material, and the heat seal layer is made of the same resin material as that of the base material. By using a laminate having such a configuration, for example, a packaging material with excellent recyclability can be produced.

A resin material of the same kind means a resin material having a common basic structure, and is not limited to a completely identical resin material. The resin material of the same type includes a resin material having a common main monomer among the monomers forming the resin material. For example, when the main monomer is described as a monomer A, the homopolymer of the monomer A, the copolymer of the monomer A and the monomer B, and the copolymer of the monomer A, the monomer B and the monomer C are the same type. It is classified as a resin material.

For example, polyethylene includes high-density polyethylene and linear low-density polyethylene, which are classified into the same type of resin material. Examples of polyester include polyethylene terephthalate and polyethylene naphthalate, which are classified as the same type of resin material.

The content of the same kind of resin material in the entire laminate of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. Since such a laminate uses the same kind of resin material, it can be classified as a so-called monomaterial material, and the recyclability of the laminate can be improved.

In one embodiment, the homogeneous resin material is polyolefin. In this case, the polyolefin content in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. In one embodiment, the content of polyethylene or polypropylene in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

In one embodiment, the homogeneous resin material is polyester. In this case, the polyester content in the entire laminate is preferably 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more.

In one embodiment, laminate 10 of the present disclosure comprises substrate 12 and heat seal layer 14, as shown in FIG. In one embodiment, the laminate 10 of the present disclosure further comprises a printing layer (not shown) on the base material 12 . The printed layer is usually formed on the surface layer of the substrate on which the heat seal layer is provided. In one embodiment, the laminate 10 of the present disclosure comprises an adhesive layer 16 between the substrate 12 and the heat seal layer 14, as shown in FIG. The substrate 12 has a multilayer structure, which is not shown.

<Base material>
The substrate constituting the laminate of the present disclosure is a stretched substrate and has a multilayer structure. Hereinafter, such a substrate is also referred to as a "stretched multilayer substrate".

The stretching treatment can remarkably improve the heat resistance and strength of the substrate, and such a stretched multilayer substrate can satisfy the physical properties required as an outer layer of, for example, a packaging material. Stretching may be uniaxial stretching or biaxial stretching.

In one embodiment, the draw ratio in the longitudinal direction (MD) of the stretched multilayer substrate is preferably 2 times or more and 10 times or less, more preferably 3 times or more and 7 times or less. In one embodiment, the draw ratio in the transverse direction (TD) of the stretched multilayer substrate is preferably 2 times or more and 10 times or less, more preferably 3 times or more and 7 times or less.

When the draw ratio is 2 times or more, for example, the rigidity, strength and heat resistance of the substrate can be improved, the printability of the substrate can be improved, and the transparency of the substrate can be improved. If the draw ratio is 10 times or less, for example, the film can be stretched satisfactorily without causing breakage or the like.

The stretched multilayer substrate that constitutes the laminate of the present disclosure is, in one embodiment, a uniaxially stretched film, more specifically a uniaxially stretched film that has been stretched in the machine direction (MD).

A stretched multilayer substrate has a multilayer structure of two or more layers. In one embodiment, the number of layers of the stretched multilayer substrate is preferably 2 to 7 layers, more preferably 3 to 5 layers. When the stretched multilayer base material has a multilayer structure, the balance of rigidity, strength, heat resistance, printability and stretchability of the base material can be improved. Each layer of the stretched multilayer substrate is also composed of the same kind of resin material.

Examples of resin materials that constitute the stretched multilayer substrate include polyolefins such as polyethylene, polypropylene and polymethylpentene; and polyesters. Among these, polyolefins are preferred, and polyethylene and polypropylene are more preferred.

Polyethylene includes, for example, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and ultra low density polyethylene. Among these, high-density polyethylene and medium-density polyethylene are preferable from the viewpoint of strength and heat resistance of the substrate, and medium-density polyethylene is more preferable from the viewpoint of stretchability.

The density of high density polyethylene is preferably above 0.945 g/ ^cm3 . The upper limit of the density of high density polyethylene is, for example, 0.965 g/cm ³ . The density of medium density polyethylene is preferably greater than 0.925 g/cm ³ and less than or equal to 0.945 g/cm ³ . The density of the low density polyethylene is preferably greater than 0.900 g/cm ³ and less than or equal to 0.925 g/cm ³ . The density of the linear low-density polyethylene is preferably greater than 0.900 g/cm ³ and less than or equal to 0.925 g/cm ³ . The density of the ultra-low density polyethylene is preferably 0.900 g/cm ³ or less. The lower limit of the density of ultra-low density polyethylene is, for example, 0.860 g/cm ³ . The density of polyethylene is measured according to JIS K7112 (1999).

The melt flow rate (MFR) of polyethylene is preferably 0.1 g/10 min or more and 50 g/10 min or less, more preferably 0.3 g/10 min or more and 30 g, from the viewpoint of film formability and substrate processability. /10 minutes or less. In the present disclosure, the MFR of polyethylene is measured according to ASTM D1238 under conditions of a temperature of 190° C. and a load of 2.16 kg.

Polypropylene may be any of propylene homopolymer, propylene random copolymer and propylene block copolymer. A propylene homopolymer is a polymer of propylene only. A propylene random copolymer is a random copolymer of propylene and an ethylenically unsaturated monomer other than propylene (for example, an α-olefin such as ethylene, 1-butene, 4-methyl-1-pentene, etc.). A propylene block copolymer is a polymer block composed of propylene and a polymer block composed of ethylenically unsaturated monomers other than propylene (for example, α-olefins such as ethylene, 1-butene, and 4-methyl-1-pentene). It is a copolymer with For example, it is preferable to use a homopolymer when emphasizing the rigidity and heat resistance of the packaging material, and to use a random copolymer when emphasizing the impact resistance of the packaging material.

The MFR of polypropylene is preferably 0.1 g/10 min or more and 50 g/10 min or less, more preferably 0.3 g/10 min or more and 30 g/10 min or less, from the viewpoint of film-forming properties and substrate processability. be. In the present disclosure, the MFR of polypropylene is measured according to ASTM D1238 under conditions of a temperature of 230° C. and a load of 2.16 kg.

Examples of polyolefins include copolymers of ethylene and ethylenically unsaturated monomers other than ethylene, and copolymers of propylene and ethylenically unsaturated monomers other than propylene (however, the above polyethylene and polypropylene (excluding applicable copolymers).

Examples of the ethylenically unsaturated monomers include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. , 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene and 6-methyl-1-heptene, α-olefins having 2 to 20 carbon atoms; vinyls such as vinyl acetate and vinyl propionate monomers; and (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate.

Polyolefins with different densities or branches can be obtained by appropriately selecting the polymerization method. For example, using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as a polymerization catalyst, one-stage polymerization is performed by any of gas phase polymerization, slurry polymerization, solution polymerization and high-pressure ion polymerization. Alternatively, it is preferable to carry out the polymerization in two or more stages.

A single-site catalyst is a catalyst capable of forming uniform active species, and is usually prepared by contacting a metallocene-based transition metal compound or a non-metallocene-based transition metal compound with an activating cocatalyst. A single-site catalyst has a more uniform structure of active sites than a multi-site catalyst, and is therefore preferable because a polymer having a high molecular weight and a highly uniform structure can be obtained.

A metallocene catalyst is preferred as the single-site catalyst. The metallocene catalyst is a catalyst containing a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, optionally an organometallic compound, and optionally a carrier.

Examples of transition metals in transition metal compounds include zirconium, titanium and hafnium, with zirconium and hafnium being preferred.

The cyclopentadienyl skeleton in the transition metal compound is a cyclopentadienyl group or a substituted cyclopentadienyl group. Substituted cyclopentadienyl groups include, for example, hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl-substituted alkyl groups, silyl-substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, and haloalkyl groups. , and halosilyl groups. A substituted cyclopentadienyl group has one or more substituents, and the substituents are bonded to each other to form a ring, an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenation product thereof. may be formed. A ring formed by combining substituents with each other may further have a substituent.

A transition metal compound usually has two ligands having a cyclopentadienyl skeleton. Each ligand having a cyclopentadienyl skeleton is preferably linked to each other by a bridging group. Examples of the cross-linking group include an alkylene group having 1 to 4 carbon atoms, a silylene group, a substituted silylene group such as a dialkylsilylene group and a diarylsilylene group, and a substituted germylene group such as a dialkylgermylene group and a diarylgermylene group. . Among these, substituted silylene groups are preferred.

A co-catalyst is a component that allows a transition metal compound of group IV of the periodic table to function effectively as a polymerization catalyst, or a component that balances ionic charges in a catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes, benzene-insoluble organoaluminumoxy compounds, ion-exchange layered silicates, boron compounds, and ions composed of cations containing or not containing active hydrogen groups and non-coordinating anions. lanthanide salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing fluoro groups.

Optional organometallic compounds include, for example, organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Among these, organoaluminum compounds are preferred.

The transition metal compound may be supported on an inorganic or organic compound carrier before use. As the support, porous oxides of inorganic or organic compounds are preferred, and specific examples include ion _- exchange layered silicates such as montmorillonite, _SiO2 , _{Al2O3 ,} MgO, ZrO2, _TiO2 , and _B2O . ₃ , CaO, ZnO, BaO, _ThO2 , or mixtures thereof.

As the polyolefin, a biomass-derived polyolefin may be used. That is, as a raw material for obtaining polyolefin, olefins derived from biomass may be used instead of olefins obtained from fossil fuels. Biomass-derived polyolefin is a carbon-neutral material, so it can reduce the environmental impact of packaging materials. Biomass-derived polyolefins (eg, polyethylene) can be produced, for example, by the method described in JP-A-2013-177531. Commercially available biomass-derived polyolefins (eg, Green PE available from Braskem) may be used.

Polyolefins recycled by mechanical recycling may be used as polyolefins. Mechanical recycling generally involves pulverizing the collected polyolefin film, washing it with alkali to remove dirt and foreign matter from the surface of the film, and then drying it for a certain period of time under high temperature and reduced pressure until it remains inside the film. In this method, contaminants are diffused and decontaminated, the dirt on the polyolefin film is removed, and the film is returned to polyolefin.

Examples of the polyester as the resin material constituting the stretched multilayer base material include copolymers of dicarboxylic acid compounds and diol compounds. If necessary, monomers other than the dicarboxylic acid compound and the diol compound may be used as the monomers forming the copolymer.

Dicarboxylic acid compounds include, for example, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid and ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexanedicarboxylic acid, decalinedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1, 8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthenedicarboxylic acid, 9,9'-bis (4-Carboxyphenyl)fluoric acid and their ester derivatives.

Examples of diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, and cyclohexane. diethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecanediethanol, decalindimethanol, decalindiethanol, 5 -methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxy cyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamandiol , paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane and pentaerythritol.

Among these, polyethylene terephthalate, which is a copolymer of terephthalic acid or its ester derivative and ethylene glycol, is preferred.

As the polyester, biomass-derived polyester may be used. In this polyester, the diol compound, which is a copolymer component, is derived from biomass, so that the amount of fossil fuel used can be greatly reduced, and the environmental impact of laminate production can be effectively reduced.

A biomass-derived diol compound, for example, a biomass-derived ethylene glycol is produced from biomass-derived ethanol (biomass ethanol) as a raw material. Biomass-derived ethylene glycol can be obtained from biomass ethanol by a conventionally known method, such as a method of producing ethylene glycol via ethylene oxide. Alternatively, commercially available biomass ethylene glycol may be used. For example, biomass ethylene glycol sold by India Glycol can be preferably used.

As the polyester, recycled polyester may be used. Recycled polyesters include, for example, chemically recycled polyesters and mechanically recycled polyesters. Chemically recycled polyester means polyester obtained by decomposing a polyester container down to the level of monomers and polymerizing the monomers again. Mechanically recycled polyester removes contaminants and foreign matter by sorting, pulverizing, and washing polyester containers to obtain flakes, which are further treated at high temperature and under reduced pressure for a certain period of time to remove contaminants inside the resin. means a polyester obtained by

The content of the same resin material in each layer constituting the stretched multilayer substrate is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

The content of the same resin material in the stretched multilayer substrate is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

The stretched multilayer substrate may contain one or more additives. Examples of additives include cross-linking agents, anti-blocking agents, slip agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, dyes and modifying resins. is mentioned. Each layer constituting the stretched multilayer base material can contain the above additives independently.

The haze value of the stretched multilayer substrate is preferably 25% or less, more preferably 15% or less, and even more preferably 10% or less. A smaller haze value is more preferable, but in one embodiment, the lower limit may be 0.1% or 1%. The haze value of the stretched multilayer substrate is measured according to JIS K7136.

The total thickness of the stretched multilayer substrate is preferably 10 μm or more and 60 μm or less, more preferably 15 μm or more and 50 μm or less. When the thickness of the stretched multilayer substrate is 10 μm or more, the rigidity and strength of the laminate can be improved. When the thickness of the stretched multilayer substrate is 60 μm or less, the workability of the laminate can be improved.

The stretched multilayer substrate is preferably surface-treated. This makes it possible to improve the adhesion between the surface layer of the stretched multilayer substrate and the layer laminated on the stretched multilayer substrate. Examples of surface treatment methods include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using gases such as oxygen gas and nitrogen gas, glow discharge treatment; and oxidation treatment using chemicals. Chemical treatment can be mentioned. Further, an anchor coat layer may be formed on the surface of the stretched multilayer substrate using a conventionally known anchor coat agent.

A stretched multilayer base material can be produced, for example, by film-forming a plurality of resin materials or resin compositions by an inflation method or a T-die method to form a laminate, and stretching the obtained laminate. The stretching treatment can improve the transparency, rigidity, strength and heat resistance of the base material, and the base material can be suitably used as, for example, a base material for packaging materials.

In one embodiment, the stretched multilayer substrate is obtained by stretching a laminate (precursor) having a multilayer structure. Specifically, each layer can be co-extruded into a tubular shape to form a film to produce a laminate. Alternatively, a laminate can be produced by coextrusion of each layer into a tubular shape and then pressing the opposing layers together with a rubber roll or the like. By manufacturing a laminate by such a method, the number of defective products can be significantly reduced, and production efficiency can be improved.

For example, when the stretched multilayer base material is made of polyethylene and the multilayer base material is produced by the T-die method, the melt flow rate (MFR) of the polyethylene constituting each layer of the multilayer base material is determined by the film formability, And from the viewpoint of processability of the multilayer base material, it is preferably 3 g/10 minutes or more and 20 g/10 minutes or less.

For example, when the stretched multilayer base material is made of polyethylene and the multilayer base material is produced by the inflation method, the MFR of the polyethylene constituting each layer of the multilayer base material depends on the film formability and the processing of the multilayer base material. From the viewpoint of suitability, it is preferably 0.5 g/10 minutes or more and 5 g/10 minutes or less.

A stretched multilayer base material is obtained, for example, by stretching the laminate described above. Preferred draw ratios are as described above. In addition, in the inflation film forming machine, the laminate can also be stretched. As a result, a stretched multilayer base material can be produced, and production efficiency can be further improved.

Several examples of embodiments of the stretched multilayer substrate are described below. Hereinafter, a layer made of polyethylene will be referred to as a "polyethylene layer".
The stretched multilayer substrate of the first embodiment includes a medium density polyethylene layer, a high density polyethylene layer, a blend layer of medium density polyethylene and high density polyethylene, a high density polyethylene layer, and a medium density polyethylene layer. Prepare in this order in the vertical direction. Such a configuration can improve the printability of the base material, improve the strength and heat resistance, and improve the stretchability of the pre-stretching laminate.

In the blend layer of medium density polyethylene and high density polyethylene, the mass ratio of medium density polyethylene to high density polyethylene (medium density polyethylene/high density polyethylene) is preferably 0.25 or more and 4 or less, more preferably 0.4. 2.4 or less.

The stretched multilayer substrate of the second embodiment includes a medium density polyethylene layer, a medium density polyethylene layer, a blend layer of medium density polyethylene and linear low density polyethylene, a medium density polyethylene layer, and a medium density polyethylene layer. are provided in this order in the thickness direction. Such a configuration can improve the printability of the base material, improve the strength and heat resistance, and improve the stretchability of the pre-stretching laminate.

In the blend layer of medium density polyethylene and linear low density polyethylene, the mass ratio of medium density polyethylene to linear low density polyethylene (medium density polyethylene/linear low density polyethylene) is preferably 0.25 or more. 4 or less, more preferably 0.4 or more and 2.4 or less.

The stretched multi-layer substrate of the third embodiment includes a blend layer of medium density polyethylene and high density polyethylene, a blend layer of medium density polyethylene and linear low density polyethylene, a linear low density polyethylene layer, and a medium density A blend layer of polyethylene and linear low density polyethylene and a blend layer of medium density polyethylene and high density polyethylene are provided in this order in the thickness direction. Such a configuration can improve the printability of the base material, improve the strength and heat resistance, and improve the stretchability of the pre-stretching laminate.

In the blend layer of medium density polyethylene and high density polyethylene, the mass ratio of medium density polyethylene to high density polyethylene (medium density polyethylene/high density polyethylene) is independently preferably 0.25 or more and 4 or less, more preferably is 0.4 or more and 2.4 or less.
In the blend layer of medium density polyethylene and linear low density polyethylene, the mass ratio of medium density polyethylene to linear low density polyethylene (medium density polyethylene/linear low density polyethylene) is preferably 0.25 or more. 4 or less, more preferably 0.4 or more and 2.4 or less.

The stretched multilayer substrate of the fourth embodiment includes a blend layer of high-density polyethylene and medium-density polyethylene, a medium-density polyethylene layer, a blend layer of linear low-density polyethylene and medium-density polyethylene, and a medium-density polyethylene layer. , a blend layer of high density polyethylene and medium density polyethylene in this order in the thickness direction. Such a configuration can improve the printability of the base material, improve the strength and heat resistance, and improve the stretchability of the pre-stretching laminate.

The mass ratio of medium density polyethylene to high density polyethylene (medium density polyethylene/high density polyethylene) in the blend layer of high density polyethylene and medium density polyethylene is independently preferably 0.25 or more and 4 or less, more preferably is 0.4 or more and 2.4 or less.
The mass ratio of linear low density polyethylene to medium density polyethylene (linear low density polyethylene/medium density polyethylene) in the blend layer of linear low density polyethylene and medium density polyethylene is preferably 0.25 or more. Below, it is more preferably 0.4 or more and 2.4 or less.

In the stretched multilayer substrates of the first to fourth embodiments, the thickness of each of the two surface layers is preferably 0.5 μm or more and 10 μm or less, more preferably 1 μm or more and 8 μm or less, and even more preferably It is 1 μm or more and 5 μm or less. Thereby, the heat resistance and printability of the substrate can be further improved.

In the stretched multilayer substrates of the first to fourth embodiments, the thickness of each of the two surface layers is preferably less than the total thickness of the inner three layers (multilayer intermediate layers). The ratio of the thickness of each of the two surface layers to the total thickness of the multilayer intermediate layer (surface layer/multilayer intermediate layer) is preferably 0.05 or more and 0.8 or less, more preferably 0.1 or more and 0.7. Below, it is more preferably 0.1 or more and 0.4 or less. Thereby, the rigidity, strength and heat resistance of the substrate can be further improved.

The stretched multilayer base material of the fifth embodiment comprises a high-density polyethylene layer and a medium-density polyethylene layer in this order in the thickness direction. By using a high-density polyethylene layer as the surface layer of the base material, the strength and heat resistance of the base material can be improved. By including the medium-density polyethylene layer in the base material, the stretching aptitude of the pre-stretching laminate can be improved.

The stretched multilayer base material of the sixth embodiment comprises a high-density polyethylene layer, a medium-density polyethylene layer, and a high-density polyethylene layer in this order in the thickness direction. With such a configuration, the strength and heat resistance of the base material can be improved, the occurrence of curling in the base material can be suppressed, and the stretching aptitude of the unstretched laminate can be improved.

In the stretched multilayer substrates of the fifth and sixth embodiments, the thickness of the high-density polyethylene layer is preferably equal to or less than the thickness of the medium-density polyethylene layer. The ratio of the thickness of the high-density polyethylene layer to the thickness of the medium-density polyethylene layer is preferably 0.1 or more and 1 or less, more preferably 0.2 or more and 0.5 or less.

The stretched multilayer substrate of the seventh embodiment includes a high density polyethylene layer, a medium density polyethylene layer, a low density polyethylene layer, a linear low density polyethylene layer or an ultra low density polyethylene layer (for simplicity of description, these The three layers are collectively described as "a low-density polyethylene layer, etc."), a medium-density polyethylene layer, and a high-density polyethylene layer are provided in this order in the thickness direction. With such a configuration, the stretchability of the laminate before stretching can be improved, the strength and heat resistance of the substrate can be improved, and the occurrence of curling in the substrate can be suppressed.

In the stretched multilayer base material of the seventh embodiment, the thickness of the high-density polyethylene layer is preferably equal to or less than the thickness of the medium-density polyethylene layer. The ratio of the thickness of the high-density polyethylene layer to the thickness of the medium-density polyethylene layer is preferably 0.1 or more and 1 or less, more preferably 0.2 or more and 0.5 or less.

In the stretched multilayer base material of the seventh embodiment, the thickness of the high-density polyethylene layer is preferably equal to or greater than the thickness of the low-density polyethylene layer and the like. The ratio of the thickness of the high density polyethylene layer to the thickness of the low density polyethylene layer is preferably 1 or more and 4 or less, more preferably 1 or more and 2 or less.

As a stretched multilayer substrate of another embodiment, a high-density polyethylene layer, a high-density polyethylene layer, a blend layer of medium-density polyethylene and high-density polyethylene, a high-density polyethylene layer, and a high-density polyethylene are arranged in the thickness direction. A substrate provided in this order in the thickness direction; a medium density polyethylene layer, a high density polyethylene layer, a linear low density polyethylene layer, a high density polyethylene layer, and a medium density polyethylene layer in this order in the thickness direction is also mentioned.

<Barrier layer>
In one embodiment, the laminate of the present disclosure comprises a barrier layer between the stretched multilayer substrate and the heat seal layer. Thereby, the gas barrier property of the laminate, specifically, the oxygen barrier property and the water vapor barrier property can be improved.

A barrier layer is formed, for example, on the surface of the stretched multilayer substrate.
Also, a barrier layer may be provided between the stretched multilayer substrate and the heat seal layer via an adhesive or the like. For example, a barrier film comprising a second substrate and a barrier layer formed on the second substrate may be provided between the stretched multilayer substrate and the heat seal layer via an adhesive or the like. good. In this aspect, from the viewpoint of recyclability, the second substrate in the barrier film is preferably made of the same resin material as the resin material forming the stretched multilayer substrate. The content of the same resin material in the second substrate is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

In one embodiment, the barrier layer is a deposited layer. The deposited layer is composed of, for example, metals such as aluminum and inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide and barium oxide. Among these, an aluminum deposition layer is preferable.

The thickness of the deposited layer is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and still more preferably 10 nm or more and 40 nm or less. By setting the thickness of the deposited layer to 1 nm or more, the oxygen barrier properties and water vapor barrier properties of the laminate can be further improved. By setting the thickness of the vapor deposition layer to 150 nm or less, the generation of cracks in the vapor deposition layer can be suppressed and the recyclability of the laminate can be improved.

Examples of methods for forming the deposited layer include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering and ion plating; and plasma chemical vapor deposition, thermal chemical vapor deposition and photochemical vapor deposition. A chemical vapor deposition method (CVD method) such as a phase growth method can be used. The deposited layer may be a composite film including two or more deposited layers of different kinds of inorganic oxides, which is formed using both physical vapor deposition and chemical vapor deposition.

The degree of vacuum in the vapor deposition chamber is preferably about 10 ^-2 to 10 ^-8 mbar before introducing oxygen, and about 10 ^-1 to 10 ^-6 mbar after introducing oxygen. The amount of oxygen to be introduced varies depending on the size of the vapor deposition machine. Inert gases such as argon gas, helium gas and nitrogen gas may be used as a carrier gas for oxygen to be introduced as long as there is no problem. The conveying speed of the stretched multilayer substrate is, for example, about 10 to 800 m/min.

The surface of the deposited layer is preferably subjected to the surface treatment described above. This can improve the adhesion between the deposited layer and the adjacent layers.

When the deposited layer is composed of inorganic oxides such as aluminum oxide and silicon oxide, a barrier coat layer may be provided on the surface of the deposited layer to form a barrier layer comprising the deposited layer and the barrier coat layer. In one embodiment, the laminate of the present disclosure includes a stretched multilayer base material, an inorganic oxide deposition layer, a barrier coat layer, and a heat seal layer in this order in the thickness direction. With such a configuration, for example, the oxygen barrier property and water vapor barrier property of the laminate can be improved, and the occurrence of cracks in the inorganic oxide deposition layer can be effectively suppressed.

In one embodiment, the barrier coat layer is composed of a gas barrier resin. Examples of gas barrier resins include polyamide resins such as ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol, polyacrylonitrile, nylon 6, nylon 6,6 and polymetaxylylene adipamide (MXD6), polyester resins, Polyurethane resins as well as (meth)acrylic resins can be mentioned.

The thickness of the barrier coat layer is preferably 0.01 μm or more and 10 μm or less, more preferably 0.1 μm or more and 5 μm or less. By setting the thickness of the barrier coat layer to 0.01 μm or more, the gas barrier property can be further improved. By setting the thickness of the barrier coat layer to 10 μm or less, the workability of the laminate can be improved. In addition, it can be a laminate that can be suitably used for manufacturing a mono-material packaging container.

The barrier coat layer can be formed by, for example, dissolving or dispersing a material such as a gas barrier resin in water or a suitable organic solvent, applying the obtained coating liquid, and drying.

In another embodiment, the barrier coat layer is obtained by polycondensing a mixture of a metal alkoxide and a water-soluble polymer by a sol-gel method in the presence of a sol-gel catalyst, water, an organic solvent, and the like. It is a gas barrier coating film formed from a composition containing a decomposition product or a hydrolytic condensate of a metal alkoxide.
By providing such a barrier coat layer on the vapor deposition layer, the generation of cracks in the vapor deposition layer can be effectively prevented.

In one embodiment, the metal alkoxide is represented by the following general formula.
R ¹ _n M (OR ² ) _m
In the above formula, R ¹ and R ² each independently represent an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, and m represents an integer of 1 or more. , n+m represents the valence of M.

Examples of organic groups represented by R ¹ and R ² include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and isobutyl group. Metal atoms M include, for example, silicon, zirconium, titanium and aluminum.

Metal alkoxides satisfying the general formula include, for example, tetramethoxysilane (Si(OCH ₃ ) ₄ ), tetraethoxysilane (Si(OC ₂ H ₅ ) ₄ ), tetrapropoxysilane (Si(OC ₃ H ₇ ) ₄ ), and tetrabutoxysilane (Si(OC ₄ H ₉ ) ₄ ).

It is preferable to use a silane coupling agent together with the metal alkoxide. A known organic reactive group-containing organoalkoxysilane can be used as the silane coupling agent.

Polyvinyl alcohol and ethylene-vinyl alcohol copolymers are preferred as the water-soluble polymer. Either one of polyvinyl alcohol and ethylene-vinyl alcohol copolymer may be used, or both may be used in combination, depending on desired physical properties such as oxygen barrier properties, water vapor barrier properties, water resistance, and weather resistance. Alternatively, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using an ethylene-vinyl alcohol copolymer may be laminated.

As the sol-gel process catalyst, an acid or amine compound is suitable.

The composition may further contain an acid. Acids are used as catalysts for hydrolysis of sol-gel process catalysts, mainly metal alkoxides and silane coupling agents. Acids include, for example, mineral acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as acetic acid and tartaric acid.

The composition may contain an organic solvent. Organic solvents include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and n-butanol.

The thickness of the gas barrier coating film is preferably 0.01 μm or more and 100 μm or less, more preferably 0.1 μm or more and 50 μm or less. Thereby, gas barrier property can be improved more. By setting the thickness of the gas barrier coating film to 0.01 μm or more, the oxygen barrier property and water vapor barrier property of the laminate can be improved, and the occurrence of cracks in the deposited layer can be prevented. By setting the thickness of the gas-barrier coating film to 100 μm or less, it is possible to obtain a laminate that can be suitably used for manufacturing a mono-material packaging container.

The gas barrier coating film is formed by applying a composition containing the above materials by conventionally known means such as roll coating such as gravure roll coater, spray coating, spin coating, dipping, brush, bar coating, and applicator. The composition can be formed by polycondensation by a sol-gel method.

An embodiment of a method for forming a gas barrier coating film will be described below.
First, a composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel process catalyst, water, an organic solvent, and optionally a silane coupling agent. A polycondensation reaction proceeds gradually in the composition.

Next, the above composition is applied onto the deposited layer by the above-described conventionally known means and dried. By this drying, the polycondensation reaction of the metal alkoxide and the water-soluble polymer (and the silane coupling agent when the composition contains a silane coupling agent) further proceeds to form a composite polymer layer. Finally, a gas barrier coating film can be formed by heating.

In the case of an adhesive layer adjacent to a barrier layer such as an aluminum deposition layer, the adhesive layer is preferably composed of a cured resin composition containing a polyester polyol, an isocyanate compound and a phosphoric acid-modified compound. Such a configuration of the adhesive layer can further improve the oxygen barrier properties and water vapor barrier properties of the laminate of the present disclosure.

<Print layer>
The laminate of the present disclosure, in one embodiment, further comprises a printed layer formed on the stretched multilayer substrate described above. In one embodiment, it is preferable that the printed layer is formed on the side of the stretched multilayer base material on which the heat seal layer is provided, because this can suppress deterioration of the image over time. If the laminate comprises a barrier layer on the stretched multilayer substrate, for example, a printed layer may be provided on the barrier layer. In this case, the laminate of the present disclosure includes, for example, a stretched multilayer substrate, a barrier layer, a print layer, and a heat seal layer in this order in the thickness direction.

The print layer includes, for example, an image. Images include, for example, characters, graphics, symbols, and combinations thereof. Examples of methods for forming the printed layer include gravure printing, offset printing, and flexographic printing. In one embodiment, the flexographic printing method is preferred from the viewpoint of reducing environmental load. Moreover, from the viewpoint of reducing the environmental load, a printed layer may be formed on the surface of the stretched multilayer base material using ink derived from biomass.

<Heat seal layer>
The laminate of the present disclosure comprises a heat seal layer. The heat seal layer in the present disclosure is a layer that has not been stretched. The heat seal layer is made of the same resin material as the resin material that forms the stretched multilayer substrate. A laminate having such a structure has both heat sealability and recyclability.

For example, when the stretched multilayer substrate is made of polyolefin, the heat seal layer is made of polyolefin, which is the same resin material as the stretched multilayer substrate. Among the polyolefins mentioned above, polyethylene and polypropylene are preferred.

In an embodiment in which the stretched multilayer substrate is made of polyethylene, examples of polyethylene that makes up the heat seal layer include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene. Low density polyethylene, linear low density polyethylene and ultra-low density polyethylene are preferred from the viewpoint of heat-sealability. From the viewpoint of reducing environmental load, biomass-derived polyethylene and/or recycled polyethylene may be used.

In an embodiment in which the stretched multilayer substrate is made of polyethylene, the content of polyethylene in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

In embodiments in which the oriented multilayer substrate is composed of polypropylene, the polypropylene that makes up the heat seal layer includes, for example, propylene homopolymers, propylene random copolymers, and propylene block copolymers. From the viewpoint of heat sealability, the density of polypropylene is preferably 0.88 g/cm ³ or more and 0.92 g/cm ³ or less, more preferably 0.90 g/cm ³ or more and 0.91 g/cm ³ or less. From the viewpoint of reducing environmental load, biomass-derived polypropylene and/or recycled polypropylene may be used.

In an embodiment in which the stretched multilayer substrate is composed of polypropylene, the content of polypropylene in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

For example, when the stretched multilayer substrate is made of polyester, the heat seal layer is made of polyester, which is the same resin material as the stretched multilayer substrate. Among the above polyesters, polyethylene terephthalate is preferred. From the viewpoint of reducing the burden on the environment, biomass-derived polyester and/or recycled polyester may be used.

In an embodiment in which the stretched multilayer substrate is made of polyester, the heat-sealable layer is preferably made of low-crystalline or amorphous polyester from the viewpoint of heat-sealability. The crystallinity of the polyester constituting the heat seal layer is preferably 12% or less, more preferably 10% or less. Thereby, the heat-sealing property can be further improved.

The crystallinity of polyester is obtained by dividing the heat of fusion when melting a low-crystalline or amorphous polyester by the heat of fusion of a complete crystal (140 J/g for polyethylene terephthalate) using a differential scanning calorimeter. Obtained by multiplying by 100.

The glass transition temperature (Tg) of the polyester constituting the heat seal layer is preferably 60°C or higher and 90°C or lower, more preferably 63°C or higher and 80°C or lower. When the Tg is 90°C or less, the heat sealability of the heat seal layer can be improved. If the Tg is 60°C or higher, blocking can be suppressed. Tg is a value determined by differential scanning calorimetry in accordance with JIS K7121.

In an embodiment in which the stretched multilayer substrate is made of polyester, the polyester content in the heat seal layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Thereby, the recyclability of the laminate can be improved.

The heat seal layer may contain one or more additives. Examples of additives include cross-linking agents, anti-blocking agents, slip agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, dyes and modifying resins. is mentioned. Each layer constituting the heat-sealable layer can contain the above additives independently.

The heat-seal layer may be a single layer or may have a multi-layer structure of two or more layers. In one embodiment, the number of heat-seal layers is 2 or more and 7 or less in the case of a multi-layer structure. Each layer of the heat seal layer is also made of the same kind of resin material.

The heat seal layer, in one embodiment, is a multilayer resin film made of the same resin material as the resin material that constitutes the stretched multilayer substrate. This multilayer resin film is an unstretched resin film. This provides excellent heat-sealability. The resin film can be produced by using, for example, a casting method, a T-die method, an inflation method, or the like.

The heat seal layer, in one embodiment, is a multilayer melt-extruded layer composed of the same type of resin material as the resin material that constitutes the stretched multilayer substrate.

For example, the heat-sealing layer can be formed by laminating an unstretched film onto a stretched multilayer substrate via an adhesive layer, if necessary, or by melt extruding a heat-sealable resin material onto the stretched multilayer substrate. . Examples of the adhesive layer include an adhesive layer to be described later.

The thickness of the heat seal layer is preferably 10 μm or more and 300 μm or less, more preferably 15 μm or more and 250 μm or less. It is preferable that the thickness of the heat seal layer is appropriately changed according to the mass of the contents to be filled in the packaging material produced by the laminate of the present disclosure, from the viewpoint of the strength of the heat seal layer and the processability of the laminate. .

For example, when the packaging material is a sachet, the thickness of the heat seal layer is preferably 20 μm or more and 60 μm or less. In this case, for example, the contents of 1 g or more and 200 g or less are satisfactorily filled in the pouch.

For example, when the packaging material is a stand pouch, the thickness of the heat seal layer is preferably 40 μm or more and 200 μm or less. In this case, for example, the contents of 50 g or more and 2000 g or less can be satisfactorily filled in the stand pouch.

In the laminate of the present disclosure, the stretched multilayer base material satisfies the rigidity, strength and heat resistance required as the outer layer film of the packaging material, and the heat seal layer enables packaging. Furthermore, the stretched multilayer base material and the heat seal layer are made of the same kind of resin material. Therefore, the laminate is suitable as a material constituting a packaging material that requires recyclability.

The laminate of the present disclosure, in one embodiment, consists only of a stretched multilayer substrate optionally formed with a printed layer, and a heat seal layer. The laminate of the present disclosure, in one embodiment, consists only of a stretched multilayer substrate optionally formed with a printed layer, an adhesive layer, and a heat seal layer. Thereby, in the laminate of the present disclosure, each resin layer is made of the same kind of resin material, so that the recyclability can be particularly improved.

<Adhesive layer>
Laminates of the present disclosure, in one embodiment, include any interlayer between the stretched multilayer substrate and the heat seal layer, between the stretched multilayer substrate and the barrier film, between the barrier film and the heat seal layer, and the like. is provided with an adhesive layer. This makes it possible to improve the adhesion between the stretched multilayer base material and the heat seal layer and the adhesion between other layers.

The adhesive layer contains one or more adhesives. Examples of adhesives include one-component curing adhesives, two-component curing adhesives, and non-curing adhesives.

The adhesive may be a non-solvent type adhesive or a solvent type adhesive, and from the viewpoint of environmental load, a non-solvent type adhesive is preferable. Solvent-free adhesives include, for example, polyether-based adhesives, polyester-based adhesives, silicone-based adhesives, epoxy-based adhesives, and urethane-based adhesives. Among these, a two-liquid curing type urethane adhesive is preferable. Examples of solvent-based adhesives include rubber-based adhesives, vinyl-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and olefin-based adhesives.

In one embodiment, from the viewpoint of recyclability, when the stretched multi-layer substrate and the heat seal layer constituting the laminate of the present disclosure are each composed of polyolefin, the adhesive layer is composed of an olefin adhesive.

In one embodiment, from the viewpoint of recyclability, when the stretched multilayer base material and the heat seal layer constituting the laminate of the present disclosure are each made of polyester, the adhesive layer is made of a polyester-based adhesive.

The adhesive layer may contain one or more additives. Additives include, for example, pigments, dyes, lubricants, colorants, wetting agents, thickeners, coagulants, gelling agents, anti-settling agents, softeners, hardening agents, plasticizers, leveling agents, antioxidants, UV absorbers, light stabilizers and flame retardants are included.

The thickness of the adhesive layer is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and still more preferably 1 μm or more and 4.5 μm or less, from the viewpoint of adhesiveness of the adhesive layer and processability of the laminate. is.

The adhesive layer is applied and dried on the stretched multilayer base material by methods such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, fonten method and transfer roll coating. can be formed by

[Use]
The laminate of the present disclosure can be suitably used for packaging materials such as packaging bags.
A packaging material of the present disclosure comprises a laminate of the present disclosure.

For example, the laminate of the present disclosure can be folded in two so that the stretched multilayer substrate is on the outside and the heat-seal layer is on the inside, and the ends and the like are heat-sealed to produce a packaging material. . Also, a packaging material can be produced by stacking a plurality of laminates of the present disclosure so that the heat-seal layers face each other and heat-sealing the edges and the like. The entire packaging material may be composed of the laminate, or part of the packaging material may be composed of the laminate.

The forms of heat sealing in packaging materials include, for example, a side seal type, a two-side seal type, a three-side seal type, a four-side seal type, an envelope pasting seal type, a joining hands pasting seal type (pillow seal type), a pleated seal type, and a flat bottom. Examples include seal type, square bottom seal type, and gusset type. Self-supporting packaging bags (stand pouches) are also possible. Methods of heat sealing include, for example, bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

For example, a standing pouch with a body and bottom can be manufactured as follows. First, one or more laminates of the present disclosure are formed into a tubular shape and heat-sealed so that the heat-seal layer is on the inside to form a body. A further laminate of the present disclosure is then folded into a V-shape with the heat seal layer on the outside. A bottom portion is formed by sandwiching the V-shaped laminate at one end of the trunk portion and heat-sealing.

In stand-up pouches, only the body may be formed of the laminate of the present disclosure, only the bottom may be formed of the laminate of the present disclosure, and both the body and the bottom may be formed of the laminate of the present disclosure. may be formed by

Contents filled in packaging materials include, for example, liquids, powders, and gels, and may be foods or non-foods. After filling the contents in the packaging material, the opening of the packaging material is heat-sealed to obtain the package.

The present disclosure relates to, for example, the following [1] to [12].
[1] A laminate comprising a substrate and a heat-sealing layer, wherein the substrate and the heat-sealing layer are made of the same type of resin material, the substrate has a multilayer structure, and the substrate is a substrate that has been stretched, and the heat-sealable layer is a layer that has not been stretched.
[2] The laminate according to [1] above, wherein the similar resin material is polyolefin.
[3] The laminate according to [1] or [2] above, wherein the similar resin material is polyethylene or polypropylene.
[4] The laminate according to [1] above, wherein the similar resin material is polyester.
[5] The laminate according to any one of [1] to [4] above, further comprising a printed layer formed on the substrate.
[6] The laminate according to any one of [1] to [5] above, wherein the heat seal layer has a multilayer structure.
[7] The laminate according to any one of [1] to [6] above, wherein the heat seal layer is an unstretched resin film or a melt-extruded layer of the resin material.
[8] The laminate according to any one of [1] to [7] above, further comprising a barrier layer formed on the substrate.
[9] The above [1], wherein the laminate further comprises a barrier film comprising a second substrate and a barrier layer formed on the second substrate between the substrate and the heat seal layer. The laminate according to any one of to [7].
[10] The laminate according to any one of [1] to [9] above, wherein the content of the same kind of resin material in the entire laminate is 90% by mass or more.
[11] The laminate according to any one of [1] to [10] above, which is a laminate for packaging materials.
[12] A packaging material comprising the laminate according to any one of [1] to [11] above.

The laminate of the present disclosure will be described more specifically based on examples, but the laminate of the present disclosure is not limited to the examples. Hereinafter, "mass part" is simply described as "part".

The polyethylene used in the following examples is described.
-Medium density polyethylene (hereinafter referred to as "MDPE"):
Product name Elite5538G
Density: 0.941 g/cm ³ Melting point: 129°C MFR: 1.3 g/10 minutes
High-density polyethylene manufactured by Dowchemical (hereinafter referred to as “HDPE”):
Product name Elite5960G
Density: 0.960 g/cm ³ Melting point: 134°C MFR: 0.8 g/10 minutes
Linear low-density polyethylene manufactured by Dowchemical (hereinafter referred to as "LLDPE"):
Product name Elite5400G
Density: 0.916 g/cm ³ Melting point: 123°C MFR: 1.3 g/10 minutes
Blend polyethylene A manufactured by Dowchemical
50 parts of MDPE and 50 parts of HDPE were mixed to obtain a blended polyethylene A (hereinafter referred to as "blended PE (A)") having an average density of 0.951 g/cm ³ .
・Blended polyethylene B
50 parts of MDPE and 50 parts of LLDPE were mixed to obtain a blended polyethylene B (hereinafter referred to as “blended PE (B)”) having an average density of 0.929 g/cm ³ .
・Blend polyethylene B1
70 parts of MDPE and 30 parts of LLDPE were mixed to obtain a blended polyethylene B1 (hereinafter referred to as “blended PE (B1)”) having an average density of 0.934 g/cm ³ .
・Blended polyethylene C
70 parts of MDPE and 30 parts of HDPE were mixed to obtain a blended polyethylene C (hereinafter referred to as "blended PE (C)") having an average density of 0.947 g/cm ³ .
・Blended polyethylene D
30 parts of MDPE and 70 parts of HDPE were mixed to obtain blended polyethylene D (hereinafter referred to as "blended PE (D)") having an average density of 0.954 g/cm ³ .

[Example 1]
MDPE, HDPE and blended PE (A) are formed into MDPE layer (15 μm)/HDPE layer (22.5 μm)/blended PE (A) layer (50 μm)/HDPE layer (22.5 μm)/MDPE layer by inflation molding method. Five layers were co-extruded at a layer thickness ratio of (15 µm) to form a tubular film to obtain a polyethylene film having a total thickness of 125 µm. Numbers in parentheses indicate layer thicknesses.
The polyethylene film prepared above is stretched in the longitudinal direction (MD) at a draw ratio of 5 times, and the MDPE layer (surface layer) on one side is subjected to corona discharge treatment, and then the end is slit. A stretched multilayer base material having a thickness of 25 μm was obtained by dividing into sheets.

A first linear low-density polyethylene (SP2520, manufactured by Prime Polymer Co., density: 0.925 g/cm ³ , melting point: 122° C.) and a second linear low-density polyethylene (SP1520, manufactured by Prime Polymer Co., Ltd., Density: 0.913 g/cm ³ , Melting point: 116° C.) is formed into a multilayer extrusion film by an inflation molding method, and a first linear low-density polyethylene layer with a thickness of 20 μm and a second linear low-density polyethylene layer with a thickness of 20 μm An unstretched polyethylene film having a multilayer structure comprising a linear low density polyethylene layer of . An unstretched polyethylene film having this multilayer structure was used as a heat seal layer as described below.

The first linear low-density polyethylene layer side of the unstretched polyethylene film (heat seal layer) having a multilayer structure prepared above and the stretched multi-layer substrate prepared above were bonded together with a two-component curable urethane adhesive. (Ru-77T/H-7 manufactured by Rock Paint Co.) was dry-laminated to obtain a laminate.

[Examples 2 to 7]
A laminate was obtained in the same manner as in Example 1, except that the layer structure of the stretched multilayer substrate was changed as shown in Table 1.

[Recyclability evaluation]
The content ratio of polyethylene in the entire laminate produced above was determined, and the recyclability was evaluated based on the following evaluation criteria.

(Evaluation criteria)
AA: The content of polyethylene in the entire laminate was 90% by mass or more.
BB: The content of polyethylene in the entire laminate was 80% by mass or more and less than 90% by mass.
CC: The content of polyethylene in the entire laminate was less than 80% by mass.

[Heat-sealability evaluation]
The laminate produced above was cut into a size of 220 mm long×130 mm wide. The two laminates cut in this way are superimposed so that the heat seal layers face each other, and the laminate prepared above is folded in a V shape so that the heat seal layer is on the outside. tucked into one end. Then, the two vertical sides and the side where the V-shaped laminate was sandwiched were heat-sealed (140° C., 1 kgf, 1 second). The resulting packaging bag was filled with 300 mL of liquid detergent, and the remaining side was heat-sealed (140° C., 1 kgf, 1 second) to obtain a package.

The package was allowed to freely fall from a height of 100 cm onto a hard floor 10 times with the body of the package horizontal to the ground. The test was conducted 10 bags at a time, the presence or absence of breakage was visually observed, and the heat sealability was evaluated based on the following evaluation criteria.

(Evaluation criteria)
AA: No damage was confirmed in all 10 bags.
NG: Breakage was confirmed in 1 or more bags out of 10 bags, and there was a problem in practical use.

[Haze evaluation]
The haze value of the stretched multilayer substrate prepared above was measured according to JIS K7136.

[Rigidity evaluation]
The stretched multilayer base material prepared above was cut into test pieces having a width of 10 mm, and the rigidity of the test pieces was measured using a loop stiffness measurement tester (manufactured by Toyo Seiki Seisakusho, trade name: Loop Stiffness Tester). The loop length was 60 mm.

[Strength evaluation]
A dumbbell-shaped test piece with a width of 10 mm was cut out from the stretched multilayer substrate prepared above. The tensile strength of this test piece in the MD direction was measured with a tensile tester (RTC-1310A manufactured by Orientec). The chuck-to-chuck distance was 10 mm, and the tensile speed was 300 mm/min.

As is clear from the results in Table 1, according to the laminate of the present disclosure, it is possible to produce a packaging bag having excellent strength, heat-sealing properties, and recyclability.

10: Laminate 12: Base material (stretched multilayer base material)
14: Heat seal layer 16: Adhesive layer

Claims (12)

A laminate comprising a substrate and a heat seal layer,
The base material and the heat seal layer are made of the same resin material,
The base material has a multilayer structure,
The base material is a base material subjected to stretching treatment,
The heat seal layer is a layer that has not been stretched,
laminate. 2. The laminate according to claim 1, wherein said homogeneous resin material is polyolefin. 3. The laminate according to claim 1, wherein said resin material of the same kind is polyethylene or polypropylene. 2. The laminate according to claim 1, wherein said homogeneous resin material is polyester. The laminate according to any one of claims 1 to 4, further comprising a print layer formed on the substrate. The laminate according to any one of claims 1 to 5, wherein the heat seal layer has a multilayer structure. The laminate according to any one of claims 1 to 6, wherein the heat seal layer is an unstretched resin film or a melt extruded layer of the resin material. The laminate according to any one of claims 1 to 7, wherein the laminate further comprises a barrier layer formed on the substrate. Claim 1, wherein the laminate further comprises a barrier film comprising a second substrate and a barrier layer formed on the second substrate between the substrate and the heat seal layer. 8. The laminate according to any one of items 1 to 7. 10. The laminate according to any one of claims 1 to 9, wherein the content of the same kind of resin material in the entire laminate is 90% by mass or more. The laminate according to any one of claims 1 to 10, which is a laminate for packaging materials. A packaging material comprising the laminate according to any one of claims 1-11.

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