Gas barrier laminate, packaging material, packaging bag and tube container

Abstract

This gas barrier layered body comprises a base material layer containing a polyolefin-based resin, a layer containing a metal oxide, and an overcoat layer containing a polyvinyl alcohol-based resin, wherein the surface of the overcoat layer has a softening temperature of 100 to 170°C as measured by local modulated thermal analysis.

Description

[Technical Field]

[0001] The present disclosure relates to a gas barrier laminate, a packaging material, a packaging bag, and a tube container. [Background technology]

[0002] BACKGROUND ART Gas barrier films in which a gas barrier layer is laminated on a polyolefin film are known as packaging materials used for packaging foods and the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-335273 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional barrier films generally use heat-resistant substrates such as polyester film or nylon film, which can be further laminated with polypropylene, polyethylene, etc. to form bags. However, with the recent trend toward monomaterials, attempts have been made to use polyolefin-based substrates such as polypropylene and polyethylene, as shown in Patent Document 1.

[0005] However, when a barrier film is produced using a polyolefin resin such as polypropylene or polyethylene as a substrate in the same manner as a polyester film or nylon film, there is a risk that the resistance to heat sterilization treatment (hot water treatment) such as boiling treatment and the resistance to bending may be insufficient.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide a gas barrier laminate that uses a polyolefin substrate and can achieve good hot water resistance and flex resistance. Another aim of the present disclosure is to provide a packaging material, a packaging bag, and a tube container that include the gas barrier laminate. [Means for solving the problem]

[0007] As a result of extensive research, the inventors discovered that adjusting the softening temperature of the overcoat layer surface within a predetermined range is an important factor in solving the above-mentioned problems, and have thus completed the gas barrier laminate according to the present disclosure.

[0008] The present disclosure provides a gas barrier laminate comprising a substrate layer containing a polyolefin-based resin, a layer containing a metal oxide, and an overcoat layer containing a polyvinyl alcohol-based resin, wherein the softening temperature of the surface of the overcoat layer measured by local modulation thermal analysis is 100 to 170°C.

[0009] In one embodiment, the layer comprising a metal oxide may be a vacuum deposited layer and may have a thickness of 5 to 100 nm.

[0010] In one embodiment, the overcoat layer may include Si.

[0011] In one embodiment, the gas barrier laminate may further include an anchor coat layer between the substrate layer and the layer containing a metal oxide.

[0012] In one embodiment, the thickness of the overcoat layer may be 100 to 800 nm.

[0013] The present disclosure provides a packaging material comprising the gas barrier laminate and a sealant layer.

[0014] The present disclosure provides a packaging bag including the above packaging material.

[0015] The present disclosure provides a tube container including the above packaging material. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to provide a gas barrier laminate that uses a polyolefin substrate and that can achieve good hot water resistance and flex resistance. Furthermore, according to the present disclosure, it is possible to provide a packaging material, a packaging bag, and a tube container that include the gas barrier laminate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a gas barrier laminate according to one embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a packaging material according to one embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a packaging material according to one embodiment. [Figure 4] FIG. 4 is a perspective view showing a packaging bag according to one embodiment. [Figure 5] FIG. 5 is a front view showing a tube container according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present disclosure will be described in detail below, with reference to the drawings where appropriate. In the drawings, identical or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional ratios of the drawings are not limited to those shown.

[0019] <Gas barrier laminate> Fig. 1 is a schematic cross-sectional view showing a gas barrier laminate according to one embodiment. The gas barrier laminate 10 shown in Fig. 1 includes a substrate layer 1, a metal oxide-containing layer 2, and an overcoat layer 3, in this order.

[0020] (base material layer) The substrate layer is a film that serves as one of the supports and contains a polyolefin resin.

[0021] Examples of polyolefin resins include polyethylene (PE), polypropylene (PP), polybutene (PB), and cycloolefin polymers. Other examples of polyolefin resins include acid-modified polyolefins obtained by graft-modifying polyolefins with unsaturated carboxylic acids, acid anhydrides of unsaturated carboxylic acids, esters of unsaturated carboxylic acids, and the like. Small amounts of secondary and tertiary components such as ethylene and butene may be used as raw material monomers in polypropylene synthesis. From the viewpoint of excellent heat resistance, a propylene monopolymer film can be used as the substrate layer.

[0022] The polyolefin resin may be a recycled resin or a resin obtained by polymerizing raw materials derived from biomass such as plants. These resins may be used alone or in combination with resins polymerized from ordinary fossil fuels.

[0023] The film constituting the base layer may be a stretched film or a non-stretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the film constituting the base layer may be a stretched film. The stretching method is not particularly limited, and any method may be used, such as inflation stretching, uniaxial stretching, or biaxial stretching, as long as it can provide a dimensionally stable film.

[0024] The thickness of the substrate layer is not particularly limited, but from the viewpoint of obtaining excellent impact resistance and excellent gas barrier properties, it can be 9 to 100 μm, and may be 15 to 30 μm.

[0025] The film constituting the base layer may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment on the lamination surface of other layers, as long as the barrier performance is not impaired, or a coating layer such as an easy-adhesion layer may be provided.

[0026] The film constituting the substrate layer may contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants, if necessary.

[0027] (Layer containing metal oxide) The metal oxide-containing layer is a layer that imparts gas barrier properties to the substrate layer. By using the metal oxide-containing layer, high gas barrier properties can be obtained while keeping the thickness low. The metal oxide-containing layer can be formed on the substrate by vacuum film formation, so it can also be called a vacuum film-formed layer.

[0028] From the viewpoint of transparency and barrier properties, specific examples of metal oxides include silicon oxide (SiOx), aluminum oxide (AlOx), etc. From the viewpoint of excellent tensile elongation during processing, silicon oxide can be used as the constituent material of the metal oxide.

[0029] The thickness of the layer containing a metal oxide can be 5 to 100 nm. When the layer thickness is 5 nm or more, sufficient gas barrier properties are easily obtained. Furthermore, when the layer thickness is 100 nm or less, cracks caused by deformation due to internal stress in the thin film are suppressed, and deterioration of gas barrier properties is easily suppressed. Note that a layer thickness exceeding 100 nm is undesirable from an economic standpoint, as costs tend to increase due to an increase in the amount of material used and a longer film formation time. From the above standpoint, the layer thickness of the layer containing a metal oxide may be 5 to 80 nm, 10 to 50 nm, or 20 to 40 nm.

[0030] (Overcoat layer) The polyvinyl alcohol resin may be any resin having a vinyl alcohol unit formed by saponifying a vinyl ester unit, such as polyvinyl alcohol (PVA) or ethylene-vinyl alcohol copolymer (EVOH). From the viewpoint of the stability and flexibility of the coating liquid, PVA is preferably used.

[0031] Examples of PVA include resins obtained by homopolymerizing vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate, followed by saponification.

[0032] The PVA may be a copolymerized or post-modified modified PVA. Copolymerized modified PVA can be obtained, for example, by copolymerizing a vinyl ester with an unsaturated monomer copolymerizable with the vinyl ester, followed by saponification. Post-modified PVA can be obtained by copolymerizing PVA obtained by polymerizing a vinyl ester and then saponifying the copolymer with an unsaturated monomer in the presence of a polymerization catalyst. The amount of modification in the modified PVA can be less than 50 mol % in order to achieve sufficient gas barrier properties, and can be 10 mol % or more in order to obtain the effect of modification.

[0033] Examples of the unsaturated monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-pentyn-1-ol, and 5-hexen-1-ol; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid; nitriles such as acrylonitrile and methacrylonitrile; amides such as diacetone acrylamide, acrylamide, and methacrylamide; and olefins such as ethylene glycol, propylene glycol, propylene glycol, propylene glycol esters ... Examples of suitable unsaturated monomers include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid; vinyl compounds such as alkyl vinyl ether, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; vinylidene chloride, 1,4-diacetoxy-2-butene, vinylene carbonate, polyoxypropylene, and polyoxypropylene vinylamine. From the viewpoint of gas barrier properties, the unsaturated monomer may be an olefin, and in particular, ethylene.

[0034] Examples of the polymerization catalyst include radical polymerization catalysts such as azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide, etc. The polymerization method is not particularly limited, and bulk polymerization, emulsion polymerization, solvent polymerization, etc. can be used.

[0035] The degree of polymerization of PVA is preferably 300 to 3000. When the degree of polymerization is 300 or more, the barrier property is likely to be good, and when it is 3000 or less, it is easy to prevent a decrease in coatability due to excessively high viscosity. The saponification degree of PVA is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 98 mol% or more. The saponification degree of PVA may be 100 mol% or less, or may be 99.9 mol% or less. The polymerization degree and saponification degree of PVA can be measured in accordance with the method described in JIS K 6726 (1994).

[0036] Saponification can be carried out using an alkali or an acid, but alkali can be used from the viewpoint of saponification rate. Examples of alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal alkoxides such as sodium ethylate, potassium ethylate, and lithium methylate.

[0037] The overcoat layer may contain Si (elemental Si). Specifically, the overcoat layer may be a cured product of an overcoat layer-forming raw material containing a polyvinyl alcohol resin and a silane compound. Examples of the silane compound include tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, and silazanes such as hexamethyldisilazane. Examples of the silane compound include compounds commonly used as silane coupling agents and polysiloxane compounds having siloxane bonds. The use of a silane coupling agent further improves the strength of the overcoat layer, and is likely to improve barrier properties and water resistance. Examples of silane coupling agents include epoxysilanes (glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, etc.), (meth)acrylicsilanes (acryloxypropyltrimethoxysilane, etc.), aminosilanes, ureidosilanes, isocyanatesilanes, isocyanuratesilanes (tris(3-trialkoxysilylpropyl)isocyanurate, etc.), and mercaptosilanes.

[0038] When forming the overcoat layer, the amount of the silane compound in the overcoat layer-forming raw material can be 0 to 0.75 parts by mass, or alternatively 0.05 to 0.5 parts by mass, or alternatively 0.1 to 0.4 parts by mass, per part by mass of the polyvinyl alcohol-based resin, from the viewpoint of maintaining adhesion to the metal oxide-containing layer and gas barrier properties.

[0039] The overcoat layer may contain a polyurethane resin from the viewpoint of flex resistance and gas barrier properties. That is, the overcoat layer may be a cured product of an overcoat layer-forming raw material containing a polyvinyl alcohol-based resin, a polyurethane resin, and a silane compound. Examples of the polyurethane resin include an aqueous polyurethane resin.

[0040] The aqueous polyurethane resin is a resin formed from an acid group-containing polyurethane resin and a polyamine compound. That is, the polyurethane resin can be said to be a reaction product of an acid group-containing polyurethane and a polyamine compound, or a resin formed by crosslinking an acid group-containing polyurethane with a polyamine compound. The use of an aqueous polyurethane resin makes it easy to impart flexibility and gas barrier properties, particularly oxygen barrier properties, to the overcoat layer. The aqueous polyurethane resin exhibits gas barrier properties by bonding the acid groups of the acid group-containing polyurethane resin with a polyamine compound acting as a crosslinker. The bond between the acid groups of the acid group-containing polyurethane resin and the polyamine compound may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group) or a covalent bond (e.g., an amide bond).

[0041] The acid group-containing polyurethane resin constituting the aqueous polyurethane resin has anionic properties and self-emulsifying properties due to the presence of acid groups, and is also referred to as an anionic self-emulsifying polyurethane resin. The acid groups of the acid group-containing polyurethane resin can bond with amino groups (primary amino groups, secondary amino groups, tertiary amino groups, etc.) of the polyamine compound constituting the aqueous polyurethane resin. Examples of the acid groups include carboxyl groups and sulfonic acid groups. The acid groups can usually be neutralized with a neutralizing agent (base) and may form a salt with the base. The acid groups may be located at the terminal or side chain of the acid group-containing polyurethane resin, but are preferably located at least on the side chain.

[0042] The acid value of the acid group-containing polyurethane resin can be selected within a range that ensures water dispersibility of the acid group-containing polyurethane resin, but is typically 5 to 100 mgKOH / g, preferably 10 to 70 mgKOH / g, and more preferably 15 to 60 mgKOH / g. If the acid value of the acid group-containing polyurethane resin is below the lower limit of the above range, the water dispersibility of the acid group-containing polyurethane resin may be insufficient, potentially resulting in a decrease in the uniform dispersion of the aqueous polyurethane resin with other materials and a decrease in the dispersion stability of the coating agent. If the acid value of the acid group-containing polyurethane resin exceeds the upper limit of the above range, the water resistance and gas barrier properties of the overcoat layer may be reduced. By keeping the acid value of the acid group-containing polyurethane resin within the above range, it is easier to avoid a decrease in dispersion stability, water resistance, and gas barrier properties. The acid value of the acid group-containing polyurethane resin is measured using a method in accordance with JIS K 0070.

[0043] The number-average molecular weight of the acid group-containing polyurethane resin can be selected appropriately, but is preferably 800 to 1,000,000, more preferably 800 to 200,000, and even more preferably 800 to 100,000. If the number-average molecular weight of the acid group-containing polyurethane resin exceeds the upper limit of the above range, the viscosity of the coating agent increases, which is undesirable. If the number-average molecular weight of the acid group-containing polyurethane resin is below the lower limit of the above range, the gas barrier properties of the overcoat layer may be insufficient. The number-average molecular weight of the acid group-containing polyurethane resin is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0044] The acid group-containing polyurethane resin may be crystalline to enhance gas barrier properties. The glass transition temperature of the acid group-containing polyurethane resin is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. If the glass transition temperature of the acid group-containing polyurethane resin is lower than 100°C, the gas barrier properties of the overcoat layer may be insufficient. The glass transition temperature of the acid group-containing polyurethane resin is typically 200°C or lower, further preferably 180°C or lower, or even 150°C or lower. It is virtually unlikely that the glass transition temperature of an acid group-containing polyurethane resin that satisfies the above-mentioned preferred ranges will be higher than the upper limit. Therefore, the glass transition temperature of the acid group-containing polyurethane resin is preferably 100 to 200°C, more preferably 110 to 180°C, and even more preferably 120 to 150°C. The glass transition temperature of the acid group-containing polyurethane resin is measured by differential scanning calorimetry (DSC).

[0045] The polyamine compound constituting the aqueous polyurethane resin is a compound having two or more basic nitrogen atoms. The basic nitrogen atom is a nitrogen atom that can bond with the acid group of the acid group-containing polyurethane resin, and examples thereof include nitrogen atoms in amino groups such as primary amino groups, secondary amino groups, and tertiary amino groups. The polyamine compound is not particularly limited as long as it can bond with the acid group of the acid group-containing polyurethane resin and improve the gas barrier property, and various compounds having two or more basic nitrogen atoms can be used. The polyamine compound is preferably a polyamine compound having two or more amino groups of at least one type selected from the group consisting of primary amino groups, secondary amino groups, and tertiary amino groups.

[0046] Specific examples of polyamine compounds include alkylenediamines, polyalkylenepolyamines, and silicon compounds having multiple basic nitrogen atoms. Examples of alkylenediamines include alkylenediamines having 2 to 10 carbon atoms, such as ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, and 1,6-hexamethylenediamine. Examples of polyalkylenepolyamines include tetraalkylenepolyamine. Examples of silicon compounds having multiple basic nitrogen atoms (including nitrogen atoms such as amino groups) include silane coupling agents having multiple basic nitrogen atoms, such as 2-[N-(2-aminoethyl)amino]ethyltrimethoxysilane and 3-[N-(2-aminoethyl)amino]propyltriethoxysilane.

[0047] In the aqueous polyurethane resin, the amount of polyamine compound used is preferably such that the molar ratio of acid groups in the acid group-containing polyurethane resin to basic nitrogen atoms in the polyamine compound (acid groups / basic nitrogen atoms) is 10 / 1 to 0.1 / 1, more preferably 5 / 1 to 0.2 / 1. When the acid group / basic nitrogen atom ratio is within the above range, the crosslinking reaction between the acid groups in the acid group-containing polyurethane and the polyamine compound occurs appropriately, and the overcoat layer exhibits excellent oxygen barrier properties.

[0048] Aqueous polyurethane resins are usually used in a state dispersed in an aqueous medium (in the form of an aqueous dispersion). Examples of aqueous media include water, water-soluble or hydrophilic organic solvents, and mixtures thereof. Examples of water-soluble or hydrophilic organic solvents include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; cellosolves; carbitols; and nitriles such as acetonitrile. Water or a medium containing water as the main component is preferred. The water content of the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. The aqueous medium may or may not contain a neutralizing agent (base) that neutralizes the acid groups of the acid group-containing polyurethane resin. A neutralizing agent is usually included.

[0049] In the aqueous dispersion of the aqueous polyurethane resin, the average particle size of the dispersed particles (polyurethane resin particles) is not particularly limited, but is preferably 20 nm to 500 nm, more preferably 25 nm to 300 nm, and even more preferably 30 nm to 200 nm. If the average particle size of the dispersed particles exceeds the upper limit of the above range, the uniform dispersion of the dispersed particles with other materials and the dispersion stability of the coating agent may be reduced, potentially resulting in insufficient gas barrier properties of the overcoat layer formed from the coating agent. If the average particle size of the dispersed particles is below the lower limit of the above range, the dispersion stability of the coating agent and the gas barrier properties of the overcoat layer formed from the coating agent cannot be expected to be further improved. Furthermore, obtaining such a dispersion is practically difficult. The average particle size is measured using a concentrated particle size analyzer (FPAR-10, manufactured by Otsuka Electronics Co., Ltd.) at a solids concentration of 0.03 to 0.3% by mass (diluted with water).

[0050] The aqueous polyurethane resin may be commercially available or produced by a known production method. Examples of commercially available products include Takelac WPB-341 (manufactured by Mitsui Chemicals, Inc.) and Hydran HW350 (manufactured by DIC Corporation). The production method for the aqueous polyurethane resin is not particularly limited, and conventional techniques for converting polyurethane resins to water, such as the acetone method and the prepolymer method, can be used. The urethanization reaction may use a urethanization catalyst, such as an amine catalyst, a tin catalyst, or a lead catalyst, as needed. For example, an acid group-containing polyurethane resin can be prepared by reacting a polyisocyanate compound with a polyhydroxy acid and, optionally, at least one of a polyol component and a chain extender component, in an inert organic solvent, such as a ketone such as acetone, an ether such as tetrahydrofuran, or a nitrile such as acetonitrile. More specifically, an aqueous dispersion of an acid group-containing polyurethane resin can be prepared by reacting a polyisocyanate compound, a polyhydroxy acid, and a polyol component in an inert organic solvent (particularly a hydrophilic or water-soluble organic solvent) to produce a prepolymer having isocyanate groups at its terminals. This prepolymer is then neutralized with a neutralizing agent and dissolved or dispersed in an aqueous medium. A chain extender component is then added and reacted, and the organic solvent is removed. A polyamine compound is added to the aqueous dispersion of the acid group-containing polyurethane resin obtained in this manner, and the mixture is heated as needed to prepare an aqueous polyurethane resin in the form of a water dispersion. When heating, the heating temperature is preferably 30 to 60°C.

[0051] When forming the overcoat layer, the amount of polyurethane resin in the raw material for forming the overcoat layer can be 0.9 to 4.0 parts by mass, or alternatively 1.1 to 3.0 parts by mass, or alternatively 1.2 to 2.5 parts by mass, per part by mass of the polyvinyl alcohol-based resin, from the viewpoint of flex resistance and gas barrier properties.

[0052] The thickness of the overcoat layer is not particularly limited, but from the viewpoint of barrier properties and flex resistance, it can be 50 to 1000 nm, or may be 100 to 800 nm, 100 to 600 nm, or 200 to 500 nm.

[0053] The softening temperature of the overcoat layer surface (the surface of the overcoat layer opposite to the metal oxide-containing layer) measured by local modulation thermal analysis is 100 to 170°C. This makes it possible to achieve both good hot water resistance and flex resistance, even when using a polyolefin substrate. The inventors speculate that the reason for this is as follows: A softening temperature of 100°C or higher provides sufficient heat resistance, thereby suppressing softening during heat sterilization treatment such as boiling, and maintaining interlayer adhesion and gas barrier properties. Furthermore, a softening temperature of 170°C or lower prevents the overcoat layer from becoming too hard, thereby reducing stress with other layers during lamination and other processes, thereby suppressing degradation of barrier properties due to layer breakage. This allows for good hot water resistance and flex resistance. From this perspective, the softening temperature may be 110°C or higher, or may be 120°C or higher, 130°C or higher, or 160°C or lower, 150°C or lower, or 140°C or lower. The softening temperature of the overcoat layer surface can be adjusted by the type and amount of polyvinyl alcohol resin, the type and amount of silane compound (TEOS or silane coupling agent), the type and amount of urethane resin, etc. For example, the softening temperature can be increased by selecting a material with a high melting point. In the examples described below, in the urethane / PVA / silane coupling agent formulation, the softening temperature can be increased by reducing the amount of PVA or increasing the amount of silane coupling agent.

[0054] The softening temperature is determined by measuring the softening behavior of a sample using localized modulation thermal analysis (LTA). The softening temperature of an overcoat layer is measured by evaluating its softening point using an atomic force microscope (AFM) equipped with a nanothermal microscope consisting of a cantilever with a heating mechanism. The cantilever is placed in contact with the surface of a solid sample fixed to a sample stage. A constant force (contact pressure) is applied to the cantilever in contact mode. Applying a voltage generates heat at the tip of the cantilever, which heats the sample, causing the sample surface to thermally expand and the cantilever to rise. Further heating of the cantilever softens the sample surface, significantly changing its hardness, causing the cantilever to descend and penetrate (penetrate) into the sample. This sudden displacement is detected. From these behaviors, the softening temperature of the local sample in the nanoscale region can be determined. While the measurement temperature varies depending on the type of resin being measured, the measurement typically begins at room temperature (25°C) and ends at around 400°C. The temperature range for calculating the softening temperature is preferably 25 to 300°C.

[0055] The contact pressure of the cantilever needs to be such that the cantilever contacts the sample but does not destroy the surface. From this perspective, the contact pressure can be set to 0.1 to 3.0V.

[0056] The temperature rise rate of the cantilever depends on the heating mechanism provided in the cantilever, but can generally be 0.1 to 10 V / sec, or may be 0.2 to 5 V / sec. The temperature rise rate is preferably constant.

[0057] The penetration depth of the cantilever needs to be deep enough to recognize the peak top of the softening curve, but if the penetration depth is too large, the cantilever may be damaged. From this perspective, the penetration depth can be set to 3 to 500 nm, and may be 5 to 300 nm.

[0058] Although not particularly limited to these, a method may be employed in which the expansion curve and the softening curve are respectively approximated by functions as needed, and the softening temperature is determined by calculating the intersection point between them.

[0059] (Anchor coat layer) The gas barrier laminate may have an anchor coat layer (adhesion layer) on the substrate layer to improve adhesion with the metal oxide-containing layer and thereby exhibit superior barrier properties. Examples of materials for the anchor coat layer include polyester resins, polyamide resins, acrylic urethane resins, polyester polyurethane resins, polyether polyurethane resins, epoxy resins, phenolic resins, (meth)acrylic resins, polyvinyl acetate resins, ethylene-vinyl alcohol copolymers, polyolefin resins such as polyethylene and polypropylene, and cellulose resins. The anchor coat layer may contain Si derived from a silane coupling agent. Specifically, the anchor coat layer may be a cured product of raw materials containing the above resin and a silane coupling agent. Among these, acrylic urethane resins and polyester polyurethane resins are preferred from the viewpoints of heat resistance and interlayer adhesive strength.

[0060] The thickness of the anchor coat layer can be set to 0.01 to 2 μm, and may be 0.05 to 0.5 μm, from the viewpoint of the uniformity and flexibility of the layer.

[0061] <Method of manufacturing gas barrier laminate> The gas barrier laminate can be produced, for example, by a production method including a step of forming a layer containing a metal oxide on a base layer, and a step of forming an overcoat layer on the layer containing the metal oxide.

[0062] (Step of forming a layer containing a metal oxide) The layer containing a metal oxide can be formed by, for example, a vacuum film-forming method. Examples of the vacuum film-forming method include physical vapor deposition and chemical vapor deposition. Examples of the physical vapor deposition method include vacuum deposition, sputtering, and ion plating. Examples of the chemical vapor deposition method include thermal CVD, plasma CVD, and photo CVD. However, the process for forming the layer containing a metal oxide is not limited to these.

[0063] (Step of forming an overcoat layer) In this process, a coating liquid containing a polyvinyl alcohol-based resin and a liquid medium can be used. The coating liquid can be obtained, for example, by dissolving a powder of a polyvinyl alcohol-based resin obtained by synthesis in a liquid medium. Examples of liquid media include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, alcohols such as isopropanol, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination. From the perspective of reducing environmental impact, water can be used as the liquid medium. In this case, the coating liquid can be obtained by dissolving a powder of a polyvinyl alcohol-based resin in water at a high temperature (e.g., 80°C).

[0064] The content of solids including the polyvinyl alcohol resin in the coating liquid can be set to 3 to 20% by mass in order to maintain good coating properties.

[0065] The coating liquid may contain the above-mentioned silane compound, polyurethane resin, other components, etc. The content of the silane compound, etc. in the coating liquid may be adjusted so that a desired amount of the silane compound, etc. is contained relative to the amount of the polyvinyl alcohol-based resin.

[0066] The coating liquid may contain additives such as isocyanate and polyethyleneimine to improve adhesion, as well as preservatives, plasticizers, surfactants, and other additives.

[0067] The coating liquid can be applied onto the metal oxide-containing layer by any appropriate method. The coating liquid can be applied by a wet film-forming method using, for example, a gravure coater, a dip coater, a reverse coater, a wire bar coater, or a die coater. The application temperature and drying temperature of the coating liquid are not particularly limited and can be, for example, 50°C or higher.

[0068] The overcoat layer may be formed on the metal oxide layer by extrusion. In the case of extrusion, multilayer extrusion using a T-die can be used. Examples of adhesives that can be used during extrusion include maleic anhydride-modified polypropylene resins.

[0069] The adhesive may be applied to the layer containing a metal oxide and then dried to form an adhesive layer on the layer containing a metal oxide in advance.

[0070] The thickness of the adhesive layer can be set to 0.1 to 50 μm, and may be 0.5 to 20 μm, from the viewpoints of adhesiveness, followability, processability, and the like.

[0071] (Step of forming anchor coat layer) When forming an anchor coat layer, this step can be carried out prior to the step of forming a layer containing a metal oxide. The anchor coat layer can be formed on the substrate layer by a coating method or an extrusion method using the material of the anchor coat layer, similar to the overcoat layer.

[0072] <Packaging material> The packaging material comprises the gas barrier laminate and a sealant layer. Examples of the sealant layer include a layer containing a polyolefin resin or a polyester resin. The thickness of the sealant layer can be determined appropriately depending on the purpose, but can be, for example, 15 to 200 μm.

[0073] The gas barrier laminate and the sealant layer may be laminated via an adhesive layer. Examples of adhesives constituting the adhesive layer include polyurethane resins in which a bifunctional or higher isocyanate compound is reacted with a base material such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. Various polyols may be used singly or in combination of two or more. For the purpose of promoting adhesion, the adhesive layer may contain a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, or the like blended with the polyurethane resin. The coating amount of the adhesive layer is, for example, 0.5 to 10 g / m2, from the viewpoint of obtaining the desired adhesive strength, followability, processability, and the like. 2 From the viewpoint of environmental consideration, the adhesive layer may use a polymer component derived from biomass or having biodegradability. Also, an adhesive having barrier properties may be used for the adhesive layer.

[0074] 2 and 3 are schematic cross-sectional views showing a packaging material according to one embodiment.

[0075] The packaging material 100 shown in Fig. 2 comprises a gas barrier laminate 10 and a sealant layer 4 provided on an overcoat layer 3 of the gas barrier laminate 10. For example, if the base layer 1 and the sealant layer 4 are both made of polyolefin-based resin, the content of the polyolefin-based resin can be 90% by mass or more (preferably 95% by mass or more) based on the total mass of the packaging material 100. Such a packaging material 100 can be realized as a mono-material.

[0076] In the above embodiment, the packaging material 100 is exemplified, in which the sealant layer 4 is bonded to the surface of the gas barrier laminate 10 facing the overcoat layer 3, but the packaging material 200 may be one in which the sealant layer 4 is bonded to the surface of the gas barrier laminate 10 facing the base layer 1 (see FIG. 3 ). Alternatively, as described below, the packaging material may be one in which the sealant layer 4 is bonded to the surface of the gas barrier laminate 10 facing the overcoat layer 3 and the surface of the gas barrier laminate 10 facing the base layer 1.

[0077] The packaging material may include another substrate layer in addition to the gas barrier laminate 10 and the sealant layer 4. The other substrate layer may contain a polyolefin resin, similar to the substrate layer in the gas barrier laminate 10. Depending on the purpose, the other substrate layer may be a heat-resistant film, an easily tearable film such as a uniaxially oriented film, or a puncture-resistant film having a co-extruded nylon layer. The packaging material may have a configuration in which the sealant layer 4 is bonded to one side of the gas barrier laminate 10 and another substrate layer is bonded to the other side. The packaging material may have a configuration in which the surface of the gas barrier laminate 10 facing the overcoat layer 3 is bonded to one side of the other substrate layer, and the sealant layer 4 is bonded to the other side.

[0078] <Packaging bag> The packaging bag of this embodiment includes the packaging material described above. The packaging bag of this embodiment can be obtained by forming the packaging material into a bag shape.

[0079] The packaging bag may be formed by folding one sheet of packaging material in half with the sealant layers facing each other and then heat-sealing three sides to form a bag shape, or by stacking two sheets of packaging material with the sealant layers facing each other and then heat-sealing four sides to form a bag shape. The packaging bag can contain contents such as food, medicine, etc. The packaging bag may also have a shape with a bent portion (folded portion) such as a standing pouch. The packaging bag of this embodiment can maintain high barrier properties even in a shape with a bent portion.

[0080] Another form of packaging bag is a packaging bag with a stopper. Examples of the structure of a packaging bag with a stopper include a structure in which the stopper is sandwiched and fixed between two sheets of packaging material that form the packaging bag, or a structure in which a hole is drilled in one side of the packaging bag and a spout is glued and fixed. The spout can be provided on the top surface of the packaging bag, or diagonally above the packaging bag, or on the side or bottom surface of the packaging bag. When the content is a liquid or gel-like food, a straw that reaches the bottom of the container can be provided in addition to the spout (so-called spout) so that the content can be directly poured into the mouth and sucked out.

[0081] Fig. 4 is a perspective view showing a packaging bag according to one embodiment. The packaging bag shown in the figure is a spouted packaging bag (a spouted gusset bag). In the spouted packaging bag 400 shown in Fig. 4, the sealant layers of the packaging material are bonded together at the seal section 130, and the spout 104 is sandwiched and fixed in the seal section 130. The spout 104 is provided with a straw 105 that reaches the bottom of the container. The spouted packaging bag 400 can be sealed by closing the spout cap 104a. The packaging bag 140 constituting the spouted packaging bag 400 may be a gusset bag that can stand on its own by expanding the lower part of the bag when filled with contents, resulting in a bulging shape.

[0082] The packaging material of this embodiment is flexible and maintains high gas barrier properties even after bending, so it can also be used suitably as a squeeze pouch. The squeeze pouch may be provided with a resealable stopper, or may be configured so that a disposable pouch has a pouring outlet that can be cut off.

[0083] Another form of packaging bag with a spout is a bag-in-box, in which a bag (inner bag) containing a liquid such as a soft drink or alcoholic beverage is placed in a carton (outer box). The packaging material of this embodiment can be used for the bag in the bag-in-box, particularly for the bag body equipped with a spout (tube) for pouring.

[0084] In the case of any of the above-mentioned packaging bags with a stopper, it is preferable to use the same resin for the stopper portion or the entire stopper including the cap as for the base layer and sealant layer of the packaging material, from the viewpoint of improving recyclability.

[0085] <Tube container> The packaging material of this embodiment can be used for the body of a tube container. That is, the tube container of this embodiment includes the packaging material.

[0086] Fig. 5 is a front view showing a tube container according to one embodiment. The tube container 500 shown in Fig. 5 includes a body 510 made of a packaging material, a spout 520 attached to one end of the body 510, and a cap 530 attached to the spout 520. The body 510 is a tubular member formed by bonding the sealant layers of the packaging material together at a seal 513 and by closing a bottom 511 located at the other end opposite the end to which the spout 520 is attached, thereby allowing the contents to be contained. The spout 520 is composed of a spout 522 for discharging the contents and a shoulder 521 that is held by the body 510 and guides the contents to the spout 522. The cap 530 is a member that allows the opening of the spout 522 to be closed and opened.

[0087] The layer structure of the body of a laminated tube, which is a type of tube container, can be, for example, from the innermost layer, a first sealant layer, an adhesive layer, a gas barrier laminate, an adhesive layer, and a second sealant layer. The substrate layer in the gas barrier laminate may face either the first sealant layer side or the second sealant layer side. The printed layer may be provided on one side of the second sealant layer and bonded to the gas barrier laminate via an adhesive layer, or may be provided on one side of the first sealant layer and bonded to the gas barrier laminate via an adhesive layer.

[0088] Alternatively, the outermost second sealant layer may be replaced with a resin layer similar to the base layer that is not intended for heat sealing. In this case, the innermost sealant layers can be bonded together at the end (sealed portion) of the packaging material to form a cylindrical body. In this case, the outermost layer does not need to be a sealant layer, so high-density polyethylene or polypropylene resin can be selected as the outermost layer, improving the durability and aesthetic appeal of the tube container. Furthermore, since the sealant layer can be approximately 200 μm thick, using a resin layer (approximately 20–30 μm thick) that is not a sealant layer as the outermost layer can significantly reduce the amount of plastic used in the entire container.

[0089] By using a base layer as the outermost layer without providing a second sealant layer, the amount of plastic used in the entire tube container can be further reduced. In this case, a printed layer may be formed on the outermost base layer and protected with an overprint varnish. In a tube container without a second sealant layer, the thickness of the packaging material in the body is thinner than in a tube container with a second sealant layer. Therefore, it is thought that the stress applied to the packaging material when bending is relatively large. However, the packaging material of this embodiment has gas barrier properties and maintains high gas barrier properties even after bending, so it can be preferably used.

[0090] The shape of the tube container can be such that the shoulder is not tapered but is perpendicular to the body so that the contents can be squeezed out to the last drop. The materials for the spout and cap of the tube container are not particularly limited, but using the same resin as the base layer and sealant layer can further improve recyclability. In tube containers, an easily peelable film is sometimes attached to the outside of the spout to close the opening, ensuring a seal until the first opening. The packaging material of this embodiment can also be used as a lid material for sealing such an opening, in combination with an easily peelable sealant. [Example]

[0091] Hereinafter, the present disclosure will be explained in more detail using experimental examples, but the present disclosure is not limited to these experimental examples.

[0092] (Preparation of composition for forming anchor coat layer) Acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and the mixture was diluted with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. β-(3,4-epoxycyclohexyl)trimethoxysilane was further added to the diluted mixture in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and these were mixed to prepare a composition for forming an anchor coat layer (anchor coat material).

[0093] (Preparation of Overcoat Layer-Forming Composition L1) Polyurethane resin (Takelac WPB-341, manufactured by Mitsui Chemicals, Inc.) and 5% PVA aqueous solution (PVA124, manufactured by Kuraray Co., Ltd.) were mixed to a solids ratio of 50:50, and then diluted with water and isopropanol to a solids concentration of 5% by mass. At this time, the isopropanol accounted for 10% by mass of the total. This prepared an overcoat layer-forming composition (overcoat material) L1.

[0094] (Preparation of Overcoat Layer-Forming Composition L2) Polyurethane resin, 5% PVA aqueous solution, and silane coupling agent (3-glycidoxypropyltriethoxysilane) were mixed to a solids ratio of 50:45:5, and then diluted with water and isopropanol to a solids concentration of 5% by mass. At this time, isopropanol was used to prepare overcoat layer-forming composition L2.

[0095] (Preparation of Overcoat Layer-Forming Composition L3) The following liquids A, B, and C were mixed in a mass ratio of 65 / 25 / 10 to prepare an overcoat layer-forming composition L3. Solution A: A hydrolysis solution with a solid content of 5% by mass (SiO2 equivalent) obtained by adding 72.1 g of 0.1 N hydrochloric acid to 17.9 g of tetraethoxysilane (TEOS: Shin-Etsu Chemical Co., Ltd., KBE-04) and 10 g of methanol and stirring for 30 minutes to hydrolyze the solution. Solution B: 5% by mass of polyvinyl alcohol in water / methanol (water:methanol mass ratio 95:5). Liquid C: A hydrolysis solution prepared by diluting 1,3,5-tris(3-trialkoxysilylpropyl) isocyanurate with a water / isopropyl alcohol mixture (water:isopropyl alcohol mass ratio 1:1) to a solids content of 5 mass%.

[0096] (Preparation of Overcoat Layer-Forming Composition L4) Composition L4 for forming an overcoat layer was prepared in the same manner as composition L1 for forming an overcoat layer, except that the polyurethane resin and a 5% aqueous solution of PVA were mixed so that the solid content ratio was 65:35.

[0097] (Preparation of base layer) OPP film: Mitsui Chemicals Tocello Co., Ltd., U-1, thickness 20 μm PE film: Tokyo Ink Co., Ltd., SMUQ, thickness 25 μm

[0098] Example 1 Using a vacuum deposition apparatus with electron beam heating, a transparent metal oxide layer (layer containing metal oxide) made of silicon oxide (SiOx) with a thickness of 50 nm was formed on the OPP film. The overcoat layer-forming composition L1 was applied onto the metal oxide layer by gravure roll coating, and the coating was dried by heating at 60°C for 1 minute to form an overcoat layer with a thickness of 400 nm, thereby obtaining a barrier film.

[0099] Example 3 The composition for forming the anchor coat layer is applied to an OPP film by gravure roll coating, and the coating film is dried and cured at 60°C, resulting in a coating amount per unit area of ​​0.1 g / m. 2 An anchor coat layer having a thickness of 40 nm was formed. Next, a metal oxide layer was formed on the anchor coat layer in the same manner as in Example 1. An overcoat layer was formed on the metal oxide layer in the same manner as in Example 1, except that the overcoat layer-forming composition L2 was used, thereby obtaining a barrier film.

[0100] (Other Examples and Comparative Examples) Barrier films were obtained in the same manner as in Example 1 or 3, except that the substrate layer, anchor coat layer, metal oxide layer, and overcoat material were changed as shown in Table 1. In Examples 4 and 5, a transparent metal oxide layer made of aluminum oxide (AlOx) with a thickness of 50 nm was formed on the anchor coat layer using a vacuum deposition apparatus using an electron beam heating system.

[0101] (Softening temperature measurement) The softening temperature of the overcoat layer was measured by local modulation thermal analysis (LTA) using the following measuring equipment. Measurement equipment: Atomic force microscope (AFM) MFP-3D-SA, manufactured by Oxford Instruments LTA option: Ztherm system (product name) Cantilever: Anasys Instruments, AN2-200

[0102] First, the cantilever was brought close to the overcoat layer surface, and shape measurements were performed within a 5 μm × 5 μm field of view. Ten measurement points were selected from the resulting shape image. Next, LTA measurements were performed, and shape measurements were performed to confirm the measurement marks. When a voltage was applied to the cantilever to heat the overcoat layer surface while maintaining a constant contact pressure, the overcoat layer surface thermally expanded, causing the cantilever to rise. After that, when the overcoat layer surface reached a certain temperature, it softened and the cantilever descended. The temperature at which the cantilever's displacement reached its maximum was measured as the softening temperature of the overcoat layer surface. The contact pressure was 1 V, the heating rate was 0.5 V / s, and the cantilever was heated until it penetrated 50 nm from the maximum displacement.

[0103] The cantilever temperature was calibrated in advance using four standard samples with known softening temperatures. The four standard samples used were polycaprolactone (melting point: 56°C), low-density polyethylene (LDPE, melting point: 111°C), polypropylene (PP, melting point: 164°C), and polyethylene terephthalate (PET, melting point: 253°C). Each measurement was performed twice at different positions, and the average value was used as the surface softening temperature to create a calibration curve. Using this calibration curve, the voltage applied to the cantilever was converted to temperature, and the softening temperature of the overcoat layer was determined. The results are shown in Table 1.

[0104] [Table 1]

[0105] (Oxygen barrier evaluation) A laminate film was produced by attaching a CPP film (Torayfan ZK207, 60 μm thick) manufactured by Toray Advanced Film Co., Ltd. or an LLDPE film (TUX MC-S, 60 μm thick) manufactured by Mitsui Chemicals Tocello Co., Ltd. to the overcoat layer side of the barrier film obtained in each example using an adhesive (A-525 / A-52 manufactured by Mitsui Chemicals, Inc.). A CPP film was used when the substrate was OPP, and an LLDPE film was used when the substrate was PE.

[0106] The obtained laminated film was used to prepare a three-sided pouch, which was filled with tap water and boiled at 95° C. for 30 minutes, thereby obtaining a boiled sample.

[0107] The resulting laminate film was attached to the fixed head of a Gelbo Flex Tester manufactured by Tester Sangyo Co., Ltd., forming a cylinder with a diameter of 87.5 mm and a length of 210 mm. Both ends of the attached laminate film were held, with an initial gripping distance of 175 mm, and a 440° twist was applied over a stroke of 87.5 mm. This reciprocating motion was repeated 10 times at a speed of 40 times per minute. This resulted in a sample that had been subjected to a flex test.

[0108] The oxygen permeability of the resulting boiled samples and flexion-tested samples was measured using an oxygen permeability measuring device (OX-TRAN2 / 20 manufactured by MOCON) at a temperature of 30°C and a relative humidity of 70% (JIS K-7126-2). The results are shown in Table 2.

[0109] [Table 2] [Explanation of symbols]

[0110] 1...base material layer, 2...layer containing metal oxide, 3...overcoat layer, 4...sealant layer, 10...gas barrier laminate, 100, 200...packaging material, 104...spark plug, 104a...spark plug cap, 105...straw, 130...seal portion, 140...packaging bag, 400...packaging bag with spout, 510...body portion, 511...bottom, 513...seal portion, 520...pouring outlet portion, 521...shoulder portion, 522...spark plug portion, 530...cap, 500...tube container.

Claims

1. The film comprises a substrate layer containing a polyolefin resin, a layer containing a metal oxide, and an overcoat layer containing a polyvinyl alcohol resin and a polyurethane resin, the polyurethane resin is a resin formed from an acid group-containing polyurethane resin and a polyamine compound, the amount of the polyurethane resin is 0.9 to 4.0 parts by mass per 1 part by mass of the polyvinyl alcohol-based resin; the overcoat layer has a thickness of 50 to 1000 nm; The gas barrier laminate has a softening temperature of the surface of the overcoat layer measured by local modulation thermal analysis of 130 to 170°C.

2. 2. The gas barrier laminate according to claim 1, wherein the layer containing a metal oxide is a vacuum-formed layer and has a thickness of 5 to 100 nm.

3. The gas barrier laminate according to claim 1 or 2, wherein the overcoat layer contains Si.

4. 4. The gas barrier laminate according to claim 1, further comprising an anchor coat layer between the substrate layer and the metal oxide-containing layer.

5. 5. The gas barrier laminate according to claim 1, wherein the overcoat layer has a thickness of 100 to 800 nm.

6. A packaging material comprising the gas barrier laminate according to any one of claims 1 to 5 and a sealant layer.

7. A packaging bag comprising the packaging material according to claim 6.

8. A tube container comprising the packaging material according to claim 6.

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