Laminate for packaging, and packaging bag

Abstract

This laminate for packaging comprises, in the order given: a base material layer; a gas barrier layer comprising an inorganic oxide layer; and a sealant layer. The base material layer is a biaxially stretched polypropylene-based resin film. The sealant layer is a polypropylene-based resin film. The laminate contains 90 mass% or more of a polypropylene-based resin with reference to the total amount thereof, and has a thermal shrinkage rate in an MD direction of less than 5% and a thermal shrinkage rate in a TD direction of less than 10% after heated in an oven at 150°C for 15 minutes, as determined by formulas (1) and (2).　(1) MD-direction thermal shrinkage rate (%) = (MD-direction length before heating - MD-direction length after heating) / MD-direction length before heating × 100 (2) TD-direction thermal shrinkage rate (%) = (TD-direction length before heating - TD-direction length after heating) / TD-direction length before heating × 100

Description

Packaging laminate and packaging bag

[0001] The present disclosure relates to a packaging laminate and a packaging bag.

[0002] BACKGROUND ART Laminates are known that include a biaxially oriented PET (polyethylene terephthalate) film, which has excellent heat resistance and toughness, as a base film and a polyolefin film, such as polyethylene or polypropylene, as a sealant layer (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2017-178357

[0004] As the issue of plastic waste gains global attention, the demand for environmentally friendly packaging materials is increasing as efforts to realize a circular economy are underway. Many global companies have set goals for better plastic resource circulation and are implementing various measures regarding packaging materials. For example, in the United States, recycling routes from collection to reuse of PE (polyethylene) are beginning to be established, and global efforts toward mono-material recycling are accelerating. In other words, there is a growing demand for mono-material packaging laminates, which have traditionally been made by combining various different materials to achieve high performance.

[0005] When converting conventional multi-material packaging materials into mono-material packaging materials, it is considered to change to packaging materials made solely of PP (polypropylene) for retort packaging from the viewpoint of sealant properties. However, such PP-based mono-material packaging materials have the problem that their gas barrier properties are more likely to deteriorate after retort processing than multi-material packaging materials.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide a packaging laminate that can suppress deterioration of gas barrier properties after retort treatment even when the packaging laminate is mainly composed of polypropylene. Another aim of the present disclosure is to provide a packaging bag using the packaging laminate.

[0007] To solve the above problems, the inventors discovered that it is important to suppress thermal shrinkage in the MD and TD directions after heating at a predetermined temperature in a laminate in which both the base layer and the sealant layer are polypropylene-based resin films, and have completed the laminate of the present disclosure. Specifically, the present disclosure provides the following packaging laminate and packaging bag: [1] A laminate comprising, in this order, a base layer, a gas barrier layer including an inorganic oxide layer, and a sealant layer, wherein the base layer is a biaxially oriented polypropylene-based resin film, and the sealant layer is a polypropylene-based resin film, the packaging laminate contains 90% by mass or more of a polypropylene-based resin based on the total amount of the laminate, and the heat shrinkage of the laminate in the MD direction, calculated by the following formulas (1) and (2) after heating in an oven at 150°C for 15 minutes, is less than 5.0% and the heat shrinkage of the laminate in the TD direction is less than 10%. MD heat shrinkage (%) = (MD length before heating - MD length after heating) / MD length before heating x 100 ... (1) TD heat shrinkage (%) = (TD length before heating - TD length after heating) / TD length before heating x 100 ... (2) [2] The packaging laminate according to [1], wherein the gas barrier layer comprises, from the base layer side, an adhesion layer containing a urethane-based resin or a polyvinyl alcohol-based resin, and the inorganic oxide layer on the adhesion layer. [3] The packaging laminate according to [2], wherein the adhesion layer is formed by drying an adhesion layer-forming composition applied to the base layer at above 60°C to 130°C for 1 second to 2 minutes. [4] The packaging laminate according to [2] or [3], wherein the cross-sectional composite elastic modulus of the adhesion layer is 3.5 to 6.5 GPa. [5] The packaging laminate according to any one of [1] to [4], wherein the base material layer has a heat shrinkage rate in the MD direction calculated by the formulas (1) and (2) of 3.0% or more and less than 7.0%, and a heat shrinkage rate in the TD direction calculated by the formulas (1) and (2) of 3.0% or more and less than 10%, after heating in an oven at 150° C. for 15 minutes. [6] The packaging laminate according to any one of [1] to [5], further comprising a base material protective layer on the base material layer, wherein the heat shrinkage rate in the MD direction of the base material protective layer calculated by the formulas (1) and (2) of 150° C. is less than 7.0%, and the heat shrinkage rate in the TD direction is less than 10%, after heating in an oven at 150° C. for 15 minutes.[7] The packaging laminate according to any one of [1] to [6], wherein the sealant layer has a heat shrinkage rate in the MD direction calculated by the formulas (1) and (2) of less than 2.0% and a heat shrinkage rate in the TD direction of less than 2.0% after heating in an oven at 150°C for 15 minutes. [8] The packaging laminate according to any one of [1] to [7], wherein the inorganic oxide layer contains aluminum oxide or silicon oxide. [9] The packaging laminate according to any one of [1] to [8], wherein the gas barrier layer further comprises a gas barrier coating layer on the inorganic oxide layer, and the gas barrier coating layer is formed using a composition for forming a gas barrier coating layer containing at least one selected from the group consisting of a hydroxyl group-containing polymeric compound, a metal alkoxide, a silane coupling agent, and a hydrolysate thereof.

[10] The packaging laminate according to any one of [1] to [9], wherein the base layer has a thickness of 12 to 38 μm.

[11] The packaging laminate according to [6], wherein the ratio of the thickness of the substrate protective layer to the substrate layer (thickness of substrate layer protective layer / thickness of substrate layer) is 0.5 to 2.0.

[12] The packaging laminate according to any one of [1] to

[11] , which is for use in a retort pouch.

[13] A packaging bag produced by forming the packaging laminate according to any one of [1] to

[12] .

[0008] According to the present disclosure, there is provided a packaging laminate that can suppress deterioration of gas barrier properties after retort treatment even when the packaging laminate is mainly composed of polypropylene. Also, according to the present disclosure, there is provided a packaging bag using the packaging laminate.

[0009] Fig. 1 is a schematic cross-sectional view showing a packaging laminate according to one embodiment, and Fig. 2 is a schematic view showing a method for measuring the thermal shrinkage rate during oven heating.

[0010] 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.

[0011] <Packaging Laminate> Fig. 1 is a schematic cross-sectional view showing a packaging laminate (hereinafter also simply referred to as "laminate") according to one embodiment. The laminate 100 shown in Fig. 1 includes, in this order, a base layer 11, a gas barrier layer 12, and a sealant layer 13. The gas barrier layer 12 and the sealant layer 13 may be bonded together by an adhesive layer (not shown). The base layer and the sealant layer are both polypropylene-based resin films containing a polypropylene-based resin. From the viewpoint of improving gas barrier properties against, for example, water vapor and oxygen, the gas barrier layer 12 may include, in this order from the base layer 11 side, an adhesion layer 12a, an inorganic oxide layer 12b, and a gas barrier coating layer 12c.

[0012] The thickness ratio of the base layer 11, the gas barrier layer 12, and the sealant layer 13 to the thickness of the laminate 100 can be 50% or more, 80% or more, or 90% or more, from the viewpoint of suppressing deterioration of the gas barrier property after retort treatment, even when the laminate 100 is mainly composed of polypropylene. The laminate 100 may be substantially composed of these three layers.

[0013] [Base Layer] The base layer is a layer that serves as a support for the laminate, and is a film containing a polypropylene-based resin.

[0014] Examples of polypropylene-based resins include acid-modified polypropylene obtained by graft-modifying polypropylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, etc. Examples of polypropylene-based resins include homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer.

[0015] The polypropylene resin film constituting the base layer may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, a tackifier, and an antistatic agent.

[0016] The polypropylene-based resin film constituting the base layer is a biaxially oriented film (biaxially oriented polypropylene-based resin film) from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., and from the viewpoint of keeping the thermal shrinkage rate of the laminate in the TD direction / MD direction less than a desired value, thereby making it possible to suppress significant deterioration of the gas barrier property after retort treatment.

[0017] The thickness of the substrate layer is not particularly limited and can be set to 6 to 200 μm depending on the application, but may be 9 to 50 μm, 12 to 38 μm, or 18 to 30 μm from the viewpoint of reducing materials to reduce the environmental load and from the viewpoint of obtaining excellent heat resistance, impact resistance, and excellent gas barrier properties.

[0018] The surface of the substrate layer may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment, or may be provided with a coating layer such as an easy-adhesion layer, as long as the barrier performance is not impaired. For example, the radiation amount of corona treatment is 2 W min / m ２ or more, and 10 W min / m ２ The corona treatment may be carried out so that the wettability of the surface of the substrate layer falls within the range described below. The substrate layer may be subjected to the corona treatment on both sides.

[0019] When an adhesive layer (described later) is not provided on the base layer, the base layer may be heat-treated before the formation of the inorganic oxide layer in order to make the thermal shrinkage rate of the laminate in the TD direction / MD direction less than a desired value. This heat treatment may be performed in the same manner as for drying the adhesive layer.

[0020] From the viewpoint of interlayer adhesion, it is preferable to use a polypropylene-based resin film with a certain degree of thermal shrinkage as the base layer rather than a polypropylene-based resin film adjusted to low thermal shrinkage. When an adhesive layer is provided on the base layer, the heat treatment during the formation of the adhesive layer (heat drying of the adhesive layer) causes the base layer to thermally shrink and microscopic irregularities to form on the surface of the adhesive layer. These irregularities are expected to exert an anchoring effect, improving the adhesion between the adhesive layer and the inorganic oxide layer.

[0021] The heat shrinkage rate of the base material layer after heating in an oven at 150°C for 15 minutes is preferably 3.0% or more and less than 7.0%, and 3.0% or more and less than 10% in the MD direction, as calculated by the following formulas (1) and (2). The heat shrinkage rate of the base material layer is the heat shrinkage rate of the base material layer alone before providing an adhesive layer, or before heat treatment if no adhesive layer is provided. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 ... (1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 ... (2)

[0022] From the viewpoint of achieving both excellent adhesion and suppression of deterioration of barrier properties, the heat shrinkage percentage in the MD direction of the base material layer calculated by formula (1) after heating in an oven for 15 minutes at 150° C. is more preferably 3.5% or more, 4.0% or more, 4.5% or more, 5.0% or more, and 6.5% or less. That is, the heat shrinkage percentage in the MD direction of the base material layer may be 3.0% or more and less than 7.0%, 3.5% or more and less than 7.0%, 4.0% or more and less than 7.0%, 4.5% or more and less than 6.5%, or 5.0% or more and less than 6.5%.

[0023] The wettability is measured in accordance with JIS K6768:1999.

[0024] From the viewpoint of achieving both excellent adhesion and suppression of deterioration of barrier properties, the heat shrinkage percentage of the base material layer in the TD direction calculated by formula (2) after heating in an oven for 15 minutes at 150° C. is more preferably 4.0% or more, 5.0% or more, 6.0% or more, and 9.0% or less. That is, the heat shrinkage percentage of the base material layer in the TD direction may be 3.0% or more and less than 10%, 4.0% or more and less than 10%, 5.0% or more and 9.0% or less, or 6.0% or more and 9.0% or less.

[0025] From the viewpoint of achieving both excellent adhesion and suppression of deterioration of barrier properties, the larger of the heat shrinkage rate in the MD direction and the heat shrinkage rate in the TD direction of the base material layer is preferably less than 6.5%, and more preferably 6.4% or less, 6.3% or less, 6.2% or less, 6.1% or less, or 6.0% or less.

[0026] [Adhesion Layer] An adhesion layer (anchor coating layer) may be provided on the surface of the substrate layer on which the inorganic oxide layer is laminated, as a layer constituting the gas barrier layer. The adhesion layer is provided on the substrate layer, and can achieve two effects: improving the adhesion performance between the substrate layer and the inorganic oxide layer, and improving the smoothness of the substrate layer surface. The improved smoothness makes it easier to form the inorganic oxide layer uniformly without defects, and makes it easier to exhibit high barrier properties. The adhesion layer can be formed using a composition for forming an adhesion layer (anchor coating agent).

[0027] The anchor coating agent preferably contains a material (such as a polyol or isocyanate) that produces a urethane resin. Examples of urethane resins include polyester polyurethane resins, polyether polyurethane resins, and acrylic polyurethane resins. Of these, polyester polyurethane resins or acrylic polyurethane resins are preferred from the viewpoints of heat resistance and interlayer adhesive strength. Acrylic polyurethane resins are particularly preferred for packaging materials that undergo retort treatment. The anchor coating agent may further contain a silane coupling agent such as γ-isocyanatepropyltrimethoxysilane.

[0028] The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and particularly preferably in the range of 0.05 to 2 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, more sufficient interlayer adhesive strength tends to be obtained, while when the thickness is equal to or less than the upper limit, desired gas barrier properties tend to be easily exhibited.

[0029] The method for applying the adhesive layer onto the substrate layer can be any known application method without any particular limitation, and examples thereof include an immersion method (dipping method), and methods using a spray, a coater, a printer, a brush, etc. In addition, examples of the types of coaters and printers used in these methods and the application methods thereof include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, microgravure coaters, coaters combined with a chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters.

[0030] The amount of adhesive layer applied is 1 m after applying and drying the anchor coating agent. ２ Mass per unit is 0.01 to 5 g / m ２ It is preferable that the density is 0.03 to 3 g / m ２ If the coating amount is equal to or greater than the lower limit, a sufficient film tends to be formed, whereas if the coating amount is equal to or less than the upper limit, the film tends to be sufficiently dried and the solvent tends not to remain.

[0031] The method for drying the adhesive layer is not particularly limited, but examples thereof include a method of drying in an oven set at a predetermined temperature, and a method using a dryer attached to the coater, such as an arch dryer, floating dryer, drum dryer, or infrared dryer.

[0032] The drying temperature is preferably above 60°C, and may be 70°C or higher, or even 75°C or higher, from the viewpoint of keeping the thermal shrinkage rate of the laminate in the TD direction / MD direction below the desired value. A drying temperature above 60°C allows the base layer to shrink more appropriately than when the drying temperature is below 60°C. This suppresses thermal shrinkage of the laminate after retort treatment. The upper limit of the drying temperature is not particularly limited, but it is preferably lower than the melting point of the polypropylene resin contained in the base layer, and therefore can be 130°C. This makes it difficult for the base layer to soften, thereby suppressing wrinkles and curls. From this viewpoint, the drying temperature can be 125°C or lower. The drying time can be, for example, about 1 second to 2 minutes. That is, the adhesion layer may be formed by drying an adhesion layer-forming composition (anchor coating agent) applied to the base layer at above 60°C to 130°C for 1 second to 2 minutes.

[0033] Instead of the polyurethane resin, a polyvinyl alcohol resin can be used for the adhesive 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).

[0034] 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. The PVA may also be a modified PVA that has been copolymerized or post-modified. The modified PVA can be obtained, for example, by copolymerizing a vinyl ester with an unsaturated monomer copolymerizable with the vinyl ester, followed by saponification. Examples of unsaturated monomers copolymerizable with vinyl esters 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; diacetone acrylamide, acrylic acid, and the like. olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid; vinyl compounds such as alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate.

[0035] The degree of polymerization of PVA is preferably 300 to 3000. If the degree of polymerization is less than 300, the barrier properties tend to decrease, while if it exceeds 3000, the viscosity becomes too high and the coatability tends to decrease. The saponification degree of PVA is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 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] EVOH is generally obtained by saponifying a copolymer of ethylene and an acid vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, or vinyl versatate.

[0037] The degree of polymerization of EVOH is preferably 300 to 3000. If the degree of polymerization is less than 300, the barrier properties tend to decrease, and if it exceeds 3000, the viscosity becomes too high and the coating suitability tends to decrease. The degree of saponification of the vinyl ester component of EVOH is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more. The degree of saponification of EVOH may be 100 mol% or less, or 99.9 mol% or less. The degree of saponification of EVOH can be determined by nuclear magnetic resonance ( １ H-NMR measurement is performed, and the peak area of ​​the hydrogen atoms contained in the vinyl ester structure and the peak area of ​​the hydrogen atoms contained in the vinyl alcohol structure are used to determine the peak area.

[0038] The ethylene unit content of EVOH is 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more. The ethylene unit content of EVOH is preferably 65 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less. When the ethylene unit content is 10 mol% or more, good gas barrier properties and dimensional stability can be maintained under high humidity conditions. On the other hand, when the ethylene unit content is 65 mol% or less, good gas barrier properties can be achieved. The ethylene unit content of EVOH can be determined by NMR.

[0039] When a polyvinyl alcohol-based resin is used as the adhesive layer, the adhesive layer can be formed using a polyvinyl alcohol-based resin solution, which is applied to the substrate layer and dried as described above.

[0040] The adhesive layer can also be formed using a gas barrier coating layer-forming composition described below.

[0041] The composite elastic modulus of the cross section of the adhesion layer is preferably 3.5 to 6.5 GPa. When the composite elastic modulus is 3.5 GPa or more, the adhesion of the laminate is likely to be improved, and when it is 6.5 GPa or less, the flex resistance of the laminate is likely to be improved. From these viewpoints, the composite elastic modulus of the cross section of the adhesion layer is more preferably 3.8 GPa or more, even more preferably 4.0 GPa or more, more preferably 6.3 GPa or less, and even more preferably 6.0 GPa or less. That is, the composite elastic modulus of the cross section of the adhesion layer may be 3.5 to 6.5 GPa, 3.8 to 6.3 GPa, or 4.0 to 6.0 GPa. The composite elastic modulus of the cross section of the adhesion layer can be measured using a scanning probe microscope (SPM).

[0042] [Inorganic Oxide Layer] The inorganic oxide layer can provide high gas barrier properties at a very thin thickness that does not affect the recyclability of the laminate. Examples of inorganic oxides contained in the inorganic oxide layer include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the inorganic oxide may be aluminum oxide or silicon oxide. Furthermore, from the viewpoint of excellent tensile stretchability during processing, the inorganic oxide may be silicon oxide.

[0043] The O / Si ratio of the silicon oxide layer is desirably 1.7 or higher. When the O / Si ratio is 1.7 or higher, the content of metallic Si is suppressed, making it easier to obtain good transparency. Furthermore, the O / Si ratio is preferably 2.0 or lower. When the O / Si ratio is 2.0 or lower, the crystallinity of SiO is increased, preventing the silicon oxide layer from becoming too hard and making it easier to obtain good tensile strength. This makes it possible to suppress the occurrence of cracks in the silicon oxide layer when laminating a gas barrier coating layer. Furthermore, even after forming into a packaging bag, the base layer may shrink due to the heat during retort treatment. However, when the O / Si ratio is 2.0 or lower, the silicon oxide layer can easily follow this shrinkage, making it possible to suppress a decrease in barrier properties. From the viewpoint of more fully obtaining these effects, the O / Si ratio of the silicon oxide layer is preferably 1.75 or higher and 1.9 or lower, and more preferably 1.8 or higher and 1.85 or lower.

[0044] The O / Si ratio of the silicon oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measurement can be performed using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromated MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0045] The O / Al ratio of the aluminum oxide layer is desirably 1.4 or higher. When the O / Al ratio is 1.4 or higher, the content of dangling bonds of aluminum atoms is suppressed, making it easier to achieve good transparency. Furthermore, the O / Al ratio is preferably 2.0 or lower. When the O / Al ratio is 2.0 or lower, the crystallinity of AlO is increased, preventing the vapor deposition layer from becoming too hard and making it easier to achieve good tensile strength. This makes it possible to suppress the occurrence of cracks in the aluminum oxide layer when laminating a gas barrier coating layer. Furthermore, even after forming into a packaging bag, the substrate layer may shrink due to the heat during retort treatment. However, when the O / Al ratio is 2.0 or lower, the aluminum oxide layer easily follows this shrinkage, making it possible to suppress a decrease in barrier properties. From the viewpoint of more fully achieving these effects, the O / Al ratio is preferably 1.45 or higher and 1.9 or lower, and more preferably 1.5 or higher and 1.85 or lower.

[0046] The O / Al ratio of the aluminum oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measurement can be performed using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromated MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the O / Al ratio, relative sensitivity factors of 2.28 for O1s and 0.6 for Al2p can be used.

[0047] The thickness of the inorganic oxide layer is preferably 10 nm or more and 50 nm or less. A thickness of 10 nm or more can provide sufficient water vapor barrier properties. Furthermore, a thickness of 50 nm or less can prevent cracks from occurring due to deformation caused by internal stress in the thin film, thereby preventing a decrease in water vapor barrier properties. Note that a thickness exceeding 50 nm is undesirable from an economic standpoint, as it increases costs due to an increase in the amount of material used and a longer film formation time. From the same viewpoint as above, the thickness of the inorganic oxide layer is more preferably 20 nm or more and 40 nm or less.

[0048] The inorganic oxide layer can be formed by, for example, vacuum film formation. In vacuum film formation, physical vapor deposition or chemical vapor deposition can be used. Examples of physical vapor deposition include, but are not limited to, vacuum deposition, sputtering, and ion plating. Examples of chemical vapor deposition include, but are not limited to, thermal CVD, plasma CVD, and photo CVD.

[0049] In the vacuum film formation, resistance heating vacuum deposition, EB (Electron Beam) heating vacuum deposition, induction heating vacuum deposition, sputtering, reactive sputtering, dual magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), and the like are particularly preferably used. However, in terms of productivity, vacuum deposition is currently the most superior. As a heating means for vacuum deposition, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method.

[0050] [Gas barrier coating layer] A gas barrier coating layer may be formed on the inorganic oxide layer. The gas barrier coating layer may be a layer formed using a gas barrier coating layer-forming composition containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof.

[0051] The gas barrier coating layer is a coating layer with gas barrier properties and can be formed using a gas barrier coating layer-forming composition (hereinafter also referred to as a coating agent) containing, as a base, an aqueous solution or a water / alcohol mixed solution containing at least one selected from the group consisting of a hydroxyl-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolysates. From the viewpoint of more adequately maintaining gas barrier properties after hot water treatment such as retort treatment, the coating agent preferably contains at least a silane coupling agent or its hydrolysate, more preferably at least one selected from the group consisting of a hydroxyl-containing polymer compound, a metal alkoxide, and their hydrolysates, and a silane coupling agent or its hydrolysate, and even more preferably a hydroxyl-containing polymer compound or its hydrolysate, a metal alkoxide or its hydrolysate, and a silane coupling agent or its hydrolysate. The coating agent can be prepared, for example, by mixing a metal alkoxide and a silane coupling agent with a solution of a hydroxyl-containing polymer, which is a water-soluble polymer, dissolved in an aqueous solvent (water or a water / alcohol mixture), or by mixing them with a solution that has been previously hydrolyzed, for example.

[0052] Each component contained in the coating agent for forming the gas barrier coating layer will be described in detail. Examples of hydroxyl group-containing polymer compounds used in the coating agent include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. Among these, polyvinyl alcohol (PVA) is preferably used in the coating agent for the gas barrier coating layer because it has particularly excellent gas barrier properties.

[0053] From the viewpoint of obtaining excellent gas barrier properties, the gas barrier coating layer is preferably formed from a composition containing at least one selected from the group consisting of metal alkoxides represented by the following general formula (I) and hydrolysates thereof: M(OR １ ) ｍ (R ２ ) ｎ－ｍ ...(I) In the above general formula (I), R １ and R２ are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. １ or R ２ If there are multiple １ Comrades or R ２ They may be the same or different.

[0054] Specific examples of metal alkoxides include tetraethoxysilane [Si(OC ２ H ５ ) ４ ], triisopropoxyaluminum [Al(O-2'-C ３ H ７ ) ３ Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis.

[0055] Examples of the silane coupling agent include compounds represented by the following general formula (II): Si(OR １１ ) ｐ (R １２ ) ３－ｐ R １３ ... (II) In the above general formula (II), R １１ represents an alkyl group such as a methyl group or an ethyl group, and R １２ represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, and R １３ represents a monovalent organic functional group, and p represents an integer of 1 to 3. １１ or R １２ If there are multiple １１ Comrades or R １２ R may be the same or different. １３ Examples of the monovalent organic functional group represented by the formula (I) include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or an isocyanate group.

[0056] Specific examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0057] The silane coupling agent may also be a polymer formed by polymerization of the compound represented by the general formula (II). A trimer is preferred as the polymer, and 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is more preferred. This is a condensation polymer of 3-isocyanatoalkylalkoxysilane. It is known that 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate has no chemical reactivity in the isocyanate moiety, but the reactivity is ensured by the polarity of the nurate moiety. It is generally known as an adhesion improver added to adhesives, etc., similar to 3-isocyanatoalkylalkoxysilane. Therefore, by adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer can be improved through hydrogen bonding. While 3-isocyanate alkyl alkoxysilanes have high reactivity and low liquid stability, 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates are not water-soluble due to the polarity of the nurate moiety, but are easily dispersed in aqueous solutions and can maintain stable liquid viscosity. Furthermore, the water resistance of 3-isocyanate alkyl alkoxysilanes and 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates is equivalent.

[0058] Some 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurates are produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and may contain the raw material 3-isocyanatepropylalkoxysilane to such an extent that it does not impair the physical properties of the isocyanurate. 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate is more preferred, and 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is even more preferred. 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is advantageous in practical use because the methoxy group has a fast hydrolysis rate and those containing a propyl group are available relatively inexpensively.

[0059] Furthermore, known additives such as isocyanate compounds, dispersants, stabilizers, viscosity adjusters, and colorants may be added to the coating agent as needed, provided that the gas barrier properties are not impaired.

[0060] The thickness of the gas barrier coating layer is preferably 50 to 1,000 nm, and more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer is 50 nm or more, more sufficient gas barrier properties tend to be obtained, and when it is 1,000 nm or less, sufficient flexibility tends to be maintained.

[0061] The coating liquid for forming the gas barrier coating layer can be applied by, for example, dipping, roll coating, gravure coating, reverse gravure coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, etc. The coating film obtained by applying this coating liquid can be dried by, for example, hot air drying, heat roll drying, high frequency irradiation, infrared irradiation, UV irradiation, or a combination thereof.

[0062] The temperature at which the coating film is dried can be, for example, 50 to 150°C, and preferably 70 to 100°C. By keeping the drying temperature within the above range, the occurrence of cracks in the inorganic oxide layer and the gas barrier coating layer can be further suppressed, and excellent barrier properties can be exhibited. The drying time can be, for example, about 1 second to 2 minutes.

[0063] The gas barrier coating layer may be formed using a coating agent containing a polyvinyl alcohol resin and a silane compound. The coating agent may contain an acid catalyst, an alkali catalyst, a photopolymerization initiator, etc., as needed.

[0064] The polyvinyl alcohol resin is as described above. Examples of the silane compound include a silane coupling agent, polysilazane, and siloxane, and specific examples thereof include tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and hexamethyldisilazane.

[0065] [Substrate protective layer] The configuration of the substrate protective layer can be appropriately referred to the above description of the configuration of the substrate layer. By providing a substrate protective layer in a laminate, the substrate layer and the gas barrier layer are more easily protected from external forces and deterioration of the gas barrier property after retort treatment is more easily suppressed than in a laminate not provided with the substrate protective layer.

[0066] From the viewpoint of achieving both rigidity as a packaging material and suitability for bag formation, the thickness ratio of the substrate protective layer to the substrate layer (thickness of substrate protective layer / thickness of substrate layer) can be 0.01 to 10, but may also be 0.1 to 5, or 0.5 to 2.0. When the thickness ratio is equal to or greater than the lower limit, the function of the substrate protective layer is easily exerted, and when the thickness ratio is equal to or less than the upper limit, deterioration of the gas barrier properties of the laminate after retort treatment is easily suppressed.

[0067] The substrate protective layer preferably has a heat shrinkage rate in the MD direction calculated by the following formulas (1) and (2) of less than 7.0% and a heat shrinkage rate in the TD direction of less than 10% after heating in an oven at 150°C for 15 minutes: MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating x 100 (1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating x 100 (2)

[0068] From the viewpoint of suppressing deterioration of the barrier properties, the heat shrinkage percentage in the MD direction of the substrate protective layer calculated by formula (1) after heating in an oven for 15 minutes at 150° C. is more preferably 3.0% or more, 3.5% or more, 4.0% or more, 4.5% or more, 5.0% or more, and 6.5% or less. That is, the heat shrinkage percentage in the MD direction of the substrate protective layer may be less than 7.0%, 3.0% or more but less than 7.0%, 3.5% or more but less than 7.0%, 4.0% or more but less than 7.0%, 4.5% or more but less than 6.5%, or 5.0% or more but less than 6.5%.

[0069] From the viewpoint of simultaneously suppressing deterioration in the barrier properties of the laminate and suppressing curling, the heat shrinkage percentage in the TD direction of the substrate protective layer calculated by formula (2) after heating in an oven for 15 minutes at 150° C. is more preferably 3.0% or more, 4.0% or more, 5.0% or more, 5.5% or more, and 9.0% or less. That is, the heat shrinkage percentage in the TD direction of the substrate protective layer may be less than 10%, 3.0% or more but less than 10%, 4.0% or more but less than 10%, 5.0% or more but less than 9.0%, or 5.5% or more but less than 9.0%.

[0070] [Printed Layer] The laminate may include a printed layer. The printed layer can be provided on at least one surface of the substrate layer, on at least one surface of the substrate protective layer, or on the surface of the gas barrier coating layer. The printed layer is provided in a position visible from the outside of the laminate for the purpose of displaying information about the contents, identifying the contents, improving concealment, or improving the design of the packaging bag. The image formed as the printed layer is not particularly limited and may represent letters, patterns, symbols, or combinations thereof. The printing method and printing ink are not particularly limited and are appropriately selected from known printing methods and printing inks taking into consideration printability on the film, design such as color tone, adhesion, and safety as a food container. Examples of printing methods that can be used include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the standpoints of productivity and high-resolution images, and flexographic printing is preferred from the standpoint of environmental impact. Examples of printing inks (resins) include biomass-derived inks, urethane-based resins, copolymer resins of vinyl chloride and vinyl acetate, and acrylic resins. From the viewpoint of environmental impact, it is preferable to form the printing layer using biomass-derived ink.

[0071] To improve the adhesion of the printed layer, the surface of the layer on which the printed layer is to be formed may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment, or a coating layer such as an easy-adhesion layer may be formed.

[0072] [Adhesive Layer] The gas barrier layer and the sealant layer, and the substrate layer and the substrate protective layer can be laminated via an adhesive layer. Examples of adhesive materials that can be used include polyester-isocyanate resins, urethane resins, and polyether resins. For use of packaging bags in retort pouch applications, a two-component curing urethane adhesive that is retort-resistant can be preferably used. Examples of methods for forming and laminating adhesive layers include known methods such as dry lamination and non-solvent lamination.

[0073] In the case of the dry lamination method, the amount of adhesive applied is, for example, 0.5 to 10 g / m from the viewpoint of obtaining the desired adhesive strength, followability, processability, etc. ２ The temperature for drying the adhesive layer can be, for example, 50 to 150° C., and preferably 70 to 100° C. The drying time can be, for example, about 1 second to 2 minutes.

[0074] When using the non-solvent lamination method, the amount of adhesive applied is 0.5 to 3 g / m compared to when using the dry lamination method. ２ This allows the polypropylene content in the entire packaging laminate to be further increased. Furthermore, when heat-sealing the packaging laminate, the heat conduction from the heat seal bar is improved, making it possible to reduce the sealing time and temperature, and suppressing the occurrence of wrinkles and the like that accompany heat-sealing.

[0075] When the substrate protective layer and the substrate layer are bonded together via an adhesive layer, the wettability of the surface of the substrate protective layer on the adhesive layer side is preferably 29 dyne or more, more preferably 30 dyne or more. This tends to further improve bag breakage resistance and vibration resistance. The wettability of the surface of the substrate layer on the adhesive layer side is preferably 32 dyne or less, more preferably 31 dyne or less. This tends to make the printed layer more likely to detach during recycling.

[0076] The adhesive layer between the substrate layer and the printed layer may be formed, for example, by the following steps (1) to (4): (1) Apply an adhesive to the surface of the substrate layer to form a coating film; (2) Dry the coating film; (3) Laminate the substrate layer and the printed layer together via the dried coating film and apply pressure; (4) Curing the dried coating film to form the adhesive layer.

[0077] By drying the adhesive applied to the base layer before contacting it with the printed layer, it is possible to prevent the adhesive from diffusing into the printed layer, which tends to make the printed layer more easily detached during recycling.

[0078] [Sealant Layer] The sealant layer is a layer that imparts heat-sealing properties to the laminate, and is a film containing a polypropylene-based resin.

[0079] Examples of polypropylene-based resins include acid-modified polypropylene obtained by graft-modifying polypropylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, etc. The polypropylene-based resin may also be a homopolypropylene resin (PP), a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, a propylene-α-olefin copolymer, etc.

[0080] The polypropylene resin film constituting the sealant layer may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, a tackifier, and an antistatic agent.

[0081] The polypropylene-based resin film constituting the sealant layer is preferably a non-stretched film (non-stretched polypropylene-based resin film) from the viewpoint of improving the sealability by heat sealing.

[0082] The thickness of the sealant layer is determined depending on the mass of the contents, the shape of the packaging bag, etc., but may be approximately 30 to 150 μm thick, or may be 50 to 80 μm thick.

[0083] After heating the sealant layer in an oven at 150°C for 15 minutes, the heat shrinkage rate in the MD direction calculated by the following formulas (1) and (2) is preferably less than 2.0%, and the heat shrinkage rate in the TD direction is preferably less than 2.0%: MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating x 100 (1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating x 100 (2)

[0084] From the viewpoint of suppressing deterioration of the barrier property, the heat shrinkage percentage of the sealant layer in the MD direction calculated by formula (1) after heating in an oven for 15 minutes at 150° C. is more preferably 0% or more, 0.5% or more, and 1.5% or less. That is, the heat shrinkage percentage of the sealant layer in the MD direction may be less than 2.0%, 0% or more but less than 2.0%, or 0.5% or more and 1.5% or less.

[0085] From the viewpoint of suppressing curling of the laminate, the heat shrinkage percentage of the sealant layer in the TD direction calculated by formula (2) after heating in an oven for 15 minutes at 150° C. is more preferably 0.2% or more, 0.3% or more, 0.4% or more, and 1.5% or less. That is, the heat shrinkage percentage of the sealant layer in the TD direction may be less than 2.0%, 0.2% or more and less than 2.0%, 0.3% or more and 1.5% or less, or 0.4% or more and 1.5% or less.

[0086]

[0043] Examples of methods for forming the sealant layer include known lamination methods, such as a dry lamination method in which a film-like sealant layer made of the above-mentioned polypropylene-based resin is bonded to the gas barrier layer using an adhesive such as a one-component curing or two-component curing urethane-based adhesive, and a non-solvent dry lamination method (non-solvent lamination method) in which a film-like sealant layer is bonded to the gas barrier layer using a solvent-free adhesive.

[0087] Among the above-mentioned forming methods, the dry lamination method is preferred because it has high resistance to retort treatment, particularly high-temperature hot water treatment at 120° C. or higher. In the non-sol lamination method, a urethane adhesive that is resistant to retort can be preferably used.

[0088] [Polypropylene Content] The laminate contains 90% by mass or more of a polypropylene-based resin based on the total amount of the laminate. Even when the laminate is mainly composed of polypropylene, it can suppress deterioration of gas barrier properties after retort treatment. Furthermore, the laminate can be said to be a packaging material made of a single material (monomaterial), and has excellent recyclability. From the viewpoint of further improving recyclability, the polypropylene content in the laminate may be 92% by mass or more, or may be 95% by mass or more, based on the total amount of the laminate.

[0089] [Heat Shrinkage Percentage of Laminate] After heating the above laminate in an oven at 150°C for 15 minutes, the heat shrinkage percentage in the MD direction calculated by the following formulas (1) and (2) is less than 5.0%, and the heat shrinkage percentage in the TD direction is less than 10%. MD heat shrinkage percentage (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 ... (1) TD heat shrinkage percentage (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 ... (2) The length before heating is the length measured at room temperature (25°C), and the length after heating is the length measured at room temperature (25°C) after heating to 150°C and then cooling.

[0090] When the thermal shrinkage rate of the laminate satisfies the above condition, deterioration of the gas barrier property after retort treatment can be suppressed even when the laminate is a mono-material laminate composed mainly of polypropylene (the polypropylene content in the laminate is 90% by mass or more).

[0091] From the viewpoint of further suppressing deterioration of the gas barrier property after retort treatment, the heat shrinkage rate in the MD direction of the laminate calculated by the above formula (1) after heating in an oven at 150°C for 15 minutes may be 4.5% or less, 4.0% or less, 3.5% or less, or 3.0% or less. The lower limit of the heat shrinkage rate can be 0% or 1%, because a negative heat shrinkage rate is undesirable. That is, the heat shrinkage rate in the MD direction of the laminate is less than 5.0%, but may be 0% or more and less than 5.0%, 0% or more and 4.5%, 0% or more and 4.0% or less, 1% or more and 3.5%, or 1% or more and 3.0% or less. From the viewpoint of further suppressing deterioration of the gas barrier property after retort treatment, the heat shrinkage rate in the TD direction of the laminate calculated by the above formula (2) after heating in an oven at 150°C for 15 minutes may be 9.0% or less, 7.5% or less, less than 6.5%, or 6.0% or less. The lower limit of the heat shrinkage rate can be 0% or 1% because a negative heat shrinkage rate is undesirable. That is, the heat shrinkage rate in the TD direction of the laminate is less than 10%, but may be 0% or more and less than 10%, 0% or more and 9.0% or less, 0% or more and 7.5% or less, 1% or more and less than 6.5%, or 1% or more and 6.0% or less.

[0092] The heat shrinkage of the laminate described above can be determined by heating a measurement sample in an oven at 150°C for 15 minutes and based on the changes in the MD length and TD length before and after heating. Specifically, the heat shrinkage can be measured, for example, by the method shown in the Examples. By observing the heat shrinkage behavior of the laminate at 150°C, it is possible to understand the degree of barrier degradation of the laminate due to retort treatment. The heat shrinkage of the laminate can be adjusted by the heat treatment of the base layer, the drying conditions when forming the adhesion layer, etc., as described above.

[0093] The laminate is mainly composed of polypropylene and can be subjected to high-temperature retort treatment, and therefore can be suitably used for retort pouch applications.

[0094] <Method for Manufacturing Laminate> A method for manufacturing a laminate can include the following steps: applying an adhesion layer-forming composition to a substrate layer and then drying the composition at above 60°C to form an adhesion layer on the substrate layer; laminating an inorganic oxide layer and, optionally, a gas barrier coating layer on the adhesion layer to form a gas barrier layer; and laminating a sealant layer on the gas barrier layer. A method for manufacturing a laminate can also include the following steps: heating the substrate layer at above 60°C; laminating an inorganic oxide layer and, optionally, a gas barrier coating layer on the substrate layer to form a gas barrier layer; and laminating a sealant layer on the gas barrier layer. Thus, from the viewpoint of keeping the thermal shrinkage rate of the laminate in the TD direction / MD direction below a desired value, it is preferable to apply heat above 60°C to the substrate layer before forming the inorganic oxide layer, thereby causing the substrate layer to shrink appropriately. This can suppress thermal shrinkage of the laminate after retort treatment, and suppress deterioration of the gas barrier properties of the laminate after retort treatment.

[0095] <Packaging Bag> The packaging bag is made by making the above-mentioned laminate into a bag, and is not particularly limited in shape, but may be, for example, a bag formed by folding one laminate in half so that the sealant layers face each other and then heat-sealing three sides, or a bag formed by stacking two laminates so that the sealant layers face each other and then heat-sealing four sides, or a self-standing standing pouch formed by stacking two laminates so that the sealant layers face each other and sealing the base material between them. The packaging bag contains food, medicine, etc. as contents and can be subjected to heat sterilization treatment such as retort treatment.

[0096] Retort processing is a process that generally involves pressure sterilization of microorganisms such as mold, yeast, and bacteria in order to preserve foods, pharmaceuticals, etc. Typically, packaging bags containing food, etc. are pressure sterilized at 105-140°C, 0.15-0.30 MPa, and for 10-120 minutes. Retort equipment comes in two types: steam type, which uses heated steam, and hot water type, which uses pressurized heated water, and is used appropriately depending on the sterilization conditions of the food, etc. that will be contained.

[0097] According to the "Standards and Criteria for Foods, Food Additives, etc." (Ministry of Health and Welfare Notification No. 370, 1959) for "Packaged, Pressure-Heat Sterilized Foods," sterilization must be performed at a core temperature of 120°C for 4 minutes, or by a method with an equivalent or greater effectiveness. This is determined based on the temperature and time required to kill heat-resistant Clostridium botulinum spores. The F-value is used as an indicator of retort sterilization conditions. The F-value is a value obtained by converting the sterilization effect of all heating steps, from temperature increase to temperature decrease, into the sterilization effect at 121°C (250°F), and can be converted using the following formula: F-value: F = t × 10^((T - 121) / Z) Z-value: Temperature increase required to reduce the sterilization time to 1 / 10 (here, the Z-value, 12°C, is typically used, which is the Z-value for Clostridium botulinum spores). Even if the heating temperature and heating time are different, the same sterilization effect can be achieved if the F-value is the same. For example, from the above formula, the F value of retort treatment at 121°C for 30 minutes is 30, and if the retort treatment temperature is 130°C, it is possible to obtain an equivalent sterilization effect with treatment for 5.34 minutes, and if it is 115°C, it is possible to obtain an equivalent sterilization effect with treatment for 95 minutes.

[0098] The packaging bag is particularly suitable for use in applications where retort treatment is carried out at a temperature of 120° C. or higher. The F value of the retort package is 30 or higher, and more preferably 35 or higher.

[0099] The packaging bag is mainly made of polypropylene and has excellent recyclability and storage properties for the contents, since deterioration of the gas barrier properties after retort treatment is suppressed.

[0100] <Lid Material> The laminate described above can also be used as a lid material for cup containers and tray containers. From the viewpoint of ease of opening, it is preferable to use a polypropylene-based resin with easy-peel properties for the sealant layer. Easy-peel properties are achieved by blending a polypropylene-based resin with an incompatible resin. Examples of such resins include high-density polyethylene, medium-density polyethylene, low-density polyethylene, ethylene-α-olefin copolymer, ethylene-α,β-unsaturated carboxylic acid, ionic crosslinked products of ethylene-α,β-unsaturated carboxylic acid, various esters of ethylene-α,β-unsaturated carboxylic acid, polystyrene resin, polyester resin, and polyamide resin. Considering the stability of peel behavior, blending with polystyrene resin is preferable. To increase the mono-material ratio, it is preferable to form a multi-layer sealant layer, with some layers being blend layers. Examples of cup containers and tray containers include those obtained by vacuum molding a co-extruded sheet composed of polypropylene / maleic acid-modified polypropylene / ethylene-vinyl alcohol copolymer (EVOH) resin / maleic acid-modified polypropylene / polypropylene. In this case, the barrier properties of the entire container can be further improved. If the EVOH resin layer is designed to be less than 10% by weight, it is possible to achieve a mono-material structure for the lid material and the cup or tray.

[0101] The present disclosure will be explained in more detail by the following examples, but the present disclosure is not limited to these examples.

[0102] <Preparation of Laminate> (Preparation of Adhesion Layer-Forming Composition) γ-isocyanatepropyltrimethoxysilane and acrylic polyol were added to ethyl acetate as a dilution solvent, mixed, and stirred. GS-5756 manufactured by Mitsubishi Rayon Co., Ltd. was used as the acrylic polyol. 60 parts by mass of γ-isocyanatepropyltrimethoxysilane was added to 100 parts by mass of the acrylic polyol. Next, tolylene diisocyanate (TDI) was added as an isocyanate compound so that the number of NCO groups was equal to the number of OH groups in the acrylic polyol. The resulting mixed solution was diluted with the dilution solvent to obtain an anchor coating liquid with a solids concentration of 2% by mass as an adhesion layer-forming composition.

[0103] (Preparation of Composition for Forming Gas Barrier Coating Layer) A composition for forming a gas barrier coating layer was prepared by mixing the following liquids A, B, and C in a mass ratio of 0.5 / 0.4 / 0.1, respectively. Liquid A: 5 mass % aqueous solution of polyvinyl alcohol (trade name: "Kuraray Poval 60-98", manufactured by Kuraray Co., Ltd.). Liquid B: tetraethoxysilane (Si(OC ２ H ５ ) ４ TEOS (trade name: KBE04, solid content: 100 mass%, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter also referred to as "TEOS"), methanol (manufactured by Kanto Chemical Co., Ltd.), and 0.1N hydrochloric acid were mixed in a mass ratio of 17 / 10 / 73 to obtain a 5 mass% solids solution (SiO ２ Solution C: A hydrolysis solution prepared by diluting 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate as a silane coupling agent with a mixed solution of water and isopropyl alcohol (water:isopropyl alcohol mass ratio 1:1) to a solids content of 5 mass%.

[0104] (Example 1) The above-described adhesive layer-forming composition was applied to the corona-treated surface of a biaxially oriented polypropylene film (manufactured by A.J. Plast, product name: VPH2011, thickness 20 μm, MD heat shrinkage rate: 5.44%, TD heat shrinkage rate: 6.50%) by gravure roll coating, and dried and cured in an oven at 75°C for 10 seconds, resulting in a coating amount of 0.1 g / m ２A 0.2 μm thick adhesive layer made of acrylic polyurethane resin (composite modulus: 5.8 GPa) was then formed. Next, a 20 nm thick transparent inorganic oxide layer (alumina vapor deposition layer) made of alumina was formed using a vacuum deposition apparatus employing an electron beam heating system. The vapor deposition material type was adjusted to form a vapor deposition layer with an O / Al ratio of 1.8. The O / Al ratio was measured using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromated MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). Quantitative analysis to determine the O / Al ratio was performed using relative sensitivity factors of 2.28 for O1s and 0.6 for Al2p, respectively.

[0105] Next, the composition for forming a gas barrier coating layer was applied onto the inorganic oxide layer by gravure roll coating, and the applied composition was dried by heating in an oven under conditions of a tension of 20 N / m, a drying temperature of 100°C, and a time of 10 seconds to form a gas barrier coating layer with a thickness of 0.3 µm, thereby obtaining a gas barrier film having a laminated structure of substrate layer / adhesion layer / inorganic oxide layer / gas barrier coating layer.

[0106] Next, a non-oriented polypropylene film (manufactured by Toray Film Processing Co., Ltd., product name: ZK207, thickness 60 μm, MD heat shrinkage: 0.96%, TD heat shrinkage: 0.44%) was laminated onto the gas barrier coating layer of the gas barrier film by dry lamination using a two-component adhesive (manufactured by Mitsui Chemicals, Inc., product name: base agent A525 / curing agent A52). The adhesive was dried at 60°C for 10 seconds. This produced a laminate having a laminate structure of base layer / adhesion layer / inorganic oxide layer / gas barrier coating layer / adhesive layer / sealant layer. The polypropylene content of the resulting laminate was 90% by mass or more, and the thickness ratio of the base layer, gas barrier layer, and sealant layer to the thickness of the laminate was 95% or more.

[0107] Examples 2 and 3 Laminates were produced in the same manner as in Example 1, except that the oven temperature during the formation of the adhesive layer was 110°C or 125°C.

[0108] Example 4 An oriented polypropylene film (manufactured by Mitsui Chemicals Tocello, Inc., trade name: ME-1, thickness 20 μm, MD heat shrinkage: 5.20%, TD heat shrinkage: 5.99%) was further laminated onto the base layer of the laminate obtained in Example 1 by dry lamination via a two-component adhesive (manufactured by Mitsui Chemicals, Inc., trade name: base agent A525 / curing agent A52). The adhesive was dried at 60°C for 10 seconds. This produced a laminate having a laminate structure of substrate protective layer / adhesive layer / substrate layer / adhesion layer / inorganic oxide layer / gas barrier coating layer / adhesive layer / sealant layer. The polypropylene content in the obtained laminate was 90% by mass or more, and the thickness ratios of the base layer, gas barrier layer, and sealant layer based on the thickness of the laminate were 95% or more.

[0109] Example 5 A laminate was produced in the same manner as in Example 4, except that the oven temperature during the formation of the adhesive layer was 125°C.

[0110] Example 6 A laminate was produced in the same manner as in Example 5, except that a 20 nm-thick transparent inorganic oxide layer (silica vapor-deposited layer) made of silica was formed instead of the alumina vapor-deposited layer. The vapor-deposited silica layer was formed by adjusting the vapor-deposited material type, resulting in a vapor-deposited layer with an O / Si ratio of 1.8. The O / Si ratio was measured using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromated MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). Quantitative analysis to determine the O / Si ratio was performed using relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p, respectively.

[0111] (Example 7) A laminate was produced in the same manner as in Example 1, except that no adhesive layer was formed on a biaxially stretched polypropylene film (manufactured by A.J. Plast, product name: VPH2011, thickness 20 μm) and the film was preheated (annealed) in an oven at 75°C for 10 seconds.

[0112] Example 8 A laminate was produced in the same manner as in Example 7, except that the oven temperature during preheating was 125°C.

[0113] (Example 9) A laminate was produced in the same manner as in Example 1, except that the adhesive layer-forming composition used was a gas barrier coating layer-forming composition in which the mass ratio of liquid A, liquid B, and liquid C was changed to a mass ratio of 0.3 / 0.6 / 0.1.

[0114] Example 10 A laminate was produced in the same manner as in Example 9, except that the oven temperature during the formation of the adhesive layer was 125°C.

[0115] Comparative Example 1 A laminate was produced in the same manner as in Example 1, except that the oven temperature during the formation of the adhesive layer was set to 60°C.

[0116] Comparative Example 2 A laminate was produced in the same manner as in Example 4, except that the oven temperature during the formation of the adhesive layer was set to 60°C.

[0117] Comparative Example 3 A laminate was produced in the same manner as in Example 7, except that the oven temperature during preheating was set to 60°C.

[0118] Comparative Example 4 A laminate was produced in the same manner as in Example 9, except that the oven temperature during the formation of the adhesive layer was set to 60°C.

[0119] <Measurement of Heat Shrinkage Ratio> The heat shrinkage ratio of each laminate was measured according to the following procedure. The results are shown in Table 1. (a) As shown in FIG. 2, the laminate was cut into a 200 mm x 200 mm piece to prepare the measurement sample 500. (b) As shown in FIG. 2, two straight lines L1 and L2, each 120 mm or longer, parallel to the TD direction of the measurement sample 500 were drawn 100 mm apart. Note that the drawing of the lines and other marks was performed on the surface of the substrate layer or substrate protective layer side in all procedures. (c) As shown in FIG. 2, two straight lines L3 and L4, each 120 mm or longer, parallel to the MD direction of the measurement sample 500 were drawn 100 mm apart. (d) As shown in FIG. 2, scales N1 to N7 were drawn at seven points at 20 mm intervals on the line L1. Scales were similarly drawn on the lines L2 to L4. At this time, the positions of the scales of lines L1 and L2 were aligned so that when each of the scales N1 to N7 of line L1 was connected to each of the scales N1 to N7 of line L2, the line was parallel to the MD direction. Furthermore, the positions of the scales of lines L3 and L4 were aligned so that when each of the scales N1 to N7 of line L3 was connected to each of the scales N1 to N7 of line L4, the line was parallel to the TD direction. (e) The measurement sample 500, placed on a Teflon (registered trademark) sheet, was placed on a glass plate in an oven heated to 150°C and heated for 15 minutes. After heating, the measurement sample 500 was removed from the oven and left at room temperature (25°C) for 30 minutes. (f) The linear distance between the scale N1 on the line L1 (the intersection of L1 and N1) and the scale N1 on the line L2 (the intersection of L2 and N1) was measured as the MD length before and after heating, and the MD heat shrinkage was calculated using the following formula (1). Similarly, the MD heat shrinkage was calculated at each of the scales N1 to N7, and the average value was used as the MD heat shrinkage of the measurement sample 500. MD heat shrinkage (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 ... (1) (g) The linear distance between the scale N1 on the line L3 (the intersection of L3 and N1) and the scale N1 on the line L4 (the intersection of L4 and N1) was measured as the TD length before and after heating, and the TD heat shrinkage was calculated using the following formula (2).Similarly, the thermal shrinkage in the TD direction was determined at each of the positions of the scales N1 to N7, and the average value thereof was defined as the thermal shrinkage in the TD direction of the measurement sample 500. Thermal shrinkage in the TD direction (%) = (length in the TD direction before heating - length in the TD direction after heating) / length in the TD direction before heating × 100 (2).

[0120] The heat shrinkage of each of the substrate protective layer, the substrate layer, and the sealant layer was also measured in the same manner as above.

[0121] <Measurement of Composite Elastic Modulus of Cross Section of Adhesion Layer> The composite elastic modulus of the cross section of the adhesion layer was measured using a scanning probe microscope (SPM) by the following method.

[0122] -Cross-Section Sample Preparation- The front and back surfaces of the laminate were corona-treated. The laminate was then cut into 2 mm x 3 mm strips with a razor, and the cut film pieces were embedded in resin. A visible light-curable resin ("Aronix LCR D-800" manufactured by Toagosei Co., Ltd.) was used. The film pieces were embedded in the resin and then cured by light irradiation. After the resin cured, the embedded film pieces were fixed in an SPM sample holder insert. The fixed film pieces were then trimmed and cross-sectioned with a glass knife at room temperature (25°C). The cross-section was then cut with a diamond knife until a mirror finish was obtained, with a cutting speed of 3 mm / s and a cutting film thickness of 500 nm. An ultramicrotome (EM UC7 manufactured by Leica Microsystems) was used as the cross-section cutting device. The cutting direction was horizontal to the interfaces of the layers contained in the film pieces. Elastic modulus measurements were performed on samples with exposed cross sections (cross-section samples) while they were fixed in an insert for the SPM sample holder.

[0123] - Composite Elastic Modulus Measurement - The cross-sectional sample was subjected to shape measurement and elastic modulus measurement using an SPM (scanning probe microscope). The SPM used was a "JupiterXR (trade name)" manufactured by Oxford Instruments. Furthermore, a "biosphere B30-FM (trade name)" manufactured by nanotools (tip radius: 30 nm, spring constant: 2.8 N / m) was used as the cantilever (measurement probe) of the SPM. In measuring the cross-sectional sample and calculating the elastic modulus of the adhesive layer, the individual characteristic values ​​of the product were referenced for the cantilever tip radius, and values ​​obtained using the GetReal method, which is a calibration function of the SPM, were used for the cantilever spring constant and optical lever sensitivity. First, shape measurement was performed by scanning perpendicular to the layer interface of the cross-sectional sample using the SPM's AC mode (tapping mode) with a field of view of 1 μm × 1 μm and a scanning speed of 2 Hz. Here, the center of the field of view was set to be the center of the film thickness of the cross-section of the adhesive layer. Next, using the SPM's contact mode, a cantilever was pressed into the adhesion layer under conditions of a maximum load of 10 nN and a test speed of 500 nm / s, and a force curve (load-displacement curve) was obtained when the cantilever was pressed into and pulled out of the adhesion layer. Force curves were acquired at 10 vertical and 10 horizontal points at 100 nm intervals within the above field of view, for a total of 100 points. Force curves with a displacement of 500 nm or more were acquired during both cantilever pressing and pulling. For the cross-sectional sample, force curves were acquired at two locations per sample level, for a total of 200 points. The cantilever's elastic modulus was assumed to be 865 GPa, the Poisson's ratio was assumed to be 0.2, and the Poisson's ratio of the adhesion layer was assumed to be 0.33. The obtained force curves were analyzed using the elastic contact model of the Johnson-Kendall-Roberts (JKR) theory, and the elastic modulus of the adhesion layer was calculated. The elastic modulus was calculated using the JKR theory by fitting analysis using the SPM analysis software, with the elastic modulus of the sample, the displacement origin, and the maximum adhesive force as fitting parameters. The analysis range for each point on the force curve was the range starting from the load and displacement when the load first reached "(maximum load - minimum load) x 0.65 + minimum load" among the load changes during pull-out after reaching the maximum load, and ending with the load and displacement when the minimum load was reached.According to the above procedure, the average value of the elastic modulus of 200 points of the force curve obtained for each example was calculated.

[0124] <Evaluation of Gas Barrier Property (Oxygen Barrier Property) of Laminate> -Before Retorting- The gas barrier property of the laminate obtained in each example was measured under conditions of 30°C and 70% RH by the MOCON method. N=20, and the average value was taken as the gas barrier value (oxygen permeability: cc m ２ / day / atm). The results are shown in Table 1. -After retort- The sealant surfaces of the laminates obtained in each example were placed facing each other and heat-sealed to produce flat pouches measuring 150 mm x 150 mm. 100 ml of water was sealed in the flat pouches, and retort treatment was carried out under conditions of 121°C for 30 minutes, after which the water was discarded and the flat pouches were allowed to air-dry for 12 hours or more. The gas barrier properties of the laminates cut out from the dried flat pouches were measured using the MOCON method under conditions of 30°C and 70% RH. N=20, and the average value was taken as the gas barrier value (oxygen permeability) of the laminates. The results are shown in Table 1 (the standard deviation of the barrier values ​​for N=20 is also shown).

[0125] <Calculation of Barrier Property Deterioration Rate> Based on the above results, the degree of deterioration in barrier property before and after retorting was calculated. The results are shown in Table 1. Barrier property deterioration rate (%) = gas barrier value after retorting / gas barrier value before retorting × 100

[0126] <Evaluation of Laminate Strength of Laminate> Using the flat pouches obtained in the same manner as in the gas barrier property evaluation, after retort treatment and drying, the laminate strength between the gas barrier film and the sealant layer was measured. The measurement was performed in accordance with JIS K6854, with a test width of 15 mm, a peel speed of 300 mm / min, and a T-type peel angle (measured values ​​in units of [N / 15 mm]). A laminate strength of 2.0 [N / 15 mm] or more was evaluated as ○, and a laminate strength of less than 2.0 [N / 15 mm] was evaluated as ×. The results are shown in Table 1.

[0127]

[0128] The packaging laminate according to the present disclosure is primarily composed of polypropylene, yet is capable of suppressing deterioration of gas barrier properties after retort treatment. Such a packaging laminate can be said to be a mono-material packaging material, and is expected to have excellent recyclability.

[0129] 11...substrate layer, 12...gas barrier layer, 12a...adhesion layer, 12b...inorganic oxide layer, 12c...gas barrier coating layer, 13...sealant layer, 100...laminated body.

Claims

1. A packaging laminate comprising, in this order, a base layer, a gas barrier layer having an inorganic oxide layer, and a sealant layer, wherein the base layer is a biaxially oriented polypropylene-based resin film, and the sealant layer is a polypropylene-based resin film, the laminate contains 90% by mass or more of a polypropylene-based resin based on the total amount of the laminate, and the laminate has a heat shrinkage rate in the MD direction of less than 5.0% and a heat shrinkage rate in the TD direction of less than 10% after heating in an oven at 150°C for 15 minutes, as calculated by the following formulas (1) and (2): MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating x 100 ... (1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating x 100 ... (2) 2. The packaging laminate according to claim 1, wherein the gas barrier layer comprises, from the base layer side, an adhesion layer containing a urethane-based resin or a polyvinyl alcohol-based resin, and the inorganic oxide layer on the adhesion layer.

3. The packaging laminate according to claim 2, wherein the adhesion layer is formed by drying the adhesion layer-forming composition applied onto the base layer at a temperature of from above 60°C to 130°C for 1 second to 2 minutes.

4. The packaging laminate according to claim 2, wherein the cross-sectional composite elastic modulus of the adhesive layer is 3.5 to 6.5 GPa.

5. The packaging laminate according to claim 1, wherein the base layer has a heat shrinkage rate in the MD direction calculated by the formulas (1) and (2) of 3.0% or more and less than 7.0%, and a heat shrinkage rate in the TD direction of 3.0% or more and less than 10%, after heating in an oven at 150°C for 15 minutes.

6. The packaging laminate according to claim 1, further comprising a substrate protective layer on the substrate layer, wherein the substrate protective layer has a heat shrinkage rate in the MD direction calculated by the formulas (1) and (2) of less than 7.0% and a heat shrinkage rate in the TD direction of less than 10% after heating in an oven at 150°C for 15 minutes.

7. The packaging laminate according to claim 1, wherein the sealant layer has a heat shrinkage rate in the MD direction calculated by the formulas (1) and (2) of less than 2.0% and a heat shrinkage rate in the TD direction of less than 2.0% after heating in an oven at 150°C for 15 minutes.

8. The packaging laminate of claim 1, wherein the inorganic oxide layer comprises aluminum oxide or silicon oxide.

9. The packaging laminate according to claim 2, wherein the gas barrier layer further comprises a gas barrier coating layer on the inorganic oxide layer, and the gas barrier coating layer is formed using a gas barrier coating layer-forming composition containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and a hydrolysate thereof.

10. The packaging laminate according to claim 1, wherein the thickness of the base layer is 12 to 38 μm.

11. The packaging laminate according to claim 6, wherein the ratio of the thickness of the substrate protective layer to the substrate layer (thickness of substrate layer protective layer / thickness of substrate layer) is 0.5 to 2.

0.

12. The packaging laminate according to claim 1, which is for a retort pouch.

13. A packaging bag produced by forming the packaging laminate according to any one of claims 1 to 12.

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