Laminate, packaging material, package, and packaged article

Abstract

To realize a package in which a film constituting a laminate is made of a polyolefin film and which exhibits high resistance to retort treatment.SOLUTION: The laminate 10A comprises a first base material layer 1, a second base material layer 2 and a sealant layer 3 in this order, all of which include a polyolefin film, the first or second base material layer further includes a gas barrier deposition layer provided on at least one of the surfaces of the polyolefin film and a gas barrier coating layer covering the gas barrier deposition layer, and the thermal shrinkage rates x1, x2 and x3 of the first base material layer, the second base material layer and the sealant layer in the machine direction after heating at 120 °C for 15 minutes satisfy the relationships represented by the following formulae (1) to (3). x2 ≤ 2.5% (1) -1.0% ≤ x2 - x1 (2) - 0.2% ≤ x2 - x3 (3) SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate, a packaging material, a package, and a packaged article. [Background technology]

[0002] For example, a packaging bag for retort foods includes a base layer, an intermediate layer, and a sealant layer bonded together with an adhesive, with the base layer and the intermediate layer each made of a polyester film having a vapor-deposited layer made of an inorganic oxide on one side, and the sealant layer made of a polyolefin film (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-178357 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, growing environmental awareness stemming from the problem of marine plastic waste has led to calls for further improvements in the efficiency of the sorted collection and recycling of plastic materials. In other words, there is now a demand for mono-materialization of packaging laminates, which have traditionally been made by combining various different materials to achieve high performance.

[0005] To achieve a mono-material laminate, the films that make up the laminate must be made of the same material. However, if a laminate is made using a polyolefin film, the resulting package may not be able to withstand high-temperature retort treatment.

[0006] The present invention has been made in view of the above circumstances, and has an object to make it possible to realize a package in which the films constituting the laminate are made of polyolefin films and which exhibit high resistance to retort treatment. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a laminate comprising a first substrate layer, a second substrate layer, and a sealant layer in this order, wherein the first substrate layer, the second substrate layer, and the sealant layer all comprise a polyolefin film, and the first substrate layer or the second substrate layer further comprises a gas barrier vapor deposition layer provided on at least one surface of the polyolefin film, and a gas barrier coating layer covering the gas barrier vapor deposition layer, wherein the heat shrinkage rate x1 of the first substrate layer in the running direction after heating at 120°C for 15 minutes, the heat shrinkage rate x2 of the second substrate layer in the running direction after heating at 120°C for 15 minutes, and the heat shrinkage rate x3 of the sealant layer in the running direction after heating at 120°C for 15 minutes satisfy the relationships shown in the following formulas (1) to (3).

[0008] x2≦2.5% …(1) -1.0%≦x2-x1 …(2) -0.2%≦x2-x3 …(3) According to another aspect of the present invention, there is provided a laminate according to the above aspect, wherein the gas barrier coating layer is a cured product of a coating liquid containing a carboxyl group-containing polymer (A), polyvalent metal-containing particles (B), a surfactant (C), an organic solvent (D), and at least one silicon-containing compound (E) selected from the group consisting of a silane coupling agent represented by the following general formula (4), a silane coupling agent represented by the following general formula (5), their hydrolysates, and their condensates:

[0009] Si(OR1)3Z1 …(4) Si(R2)(OR3)2Z2 …(5) In general formula (4), R1 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z1 is a group containing an epoxy group. In general formula (5), R2 is a methyl group, R3 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z2 is a group containing an epoxy group.

[0010] Alternatively, according to another aspect of the present invention, there is provided a laminate according to the above aspect, wherein the gas barrier coating layer is a cured product of a coating liquid containing one or more selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and hydrolysates thereof.

[0011] According to yet another aspect of the present invention, there is provided the laminate according to any one of the above aspects, wherein the gas barrier vapor-deposited layer contains aluminum oxide or silicon oxide.

[0012] According to yet another aspect of the present invention, there is provided a packaging material comprising a laminate according to any of the above aspects.

[0013] According to yet another aspect of the present invention, there is provided a packaging material according to the above aspect, which is for retort use.

[0014] According to yet another aspect of the present invention, there is provided a package including a packaging material according to any of the above aspects.

[0015] According to yet another aspect of the present invention, there is provided a packaging body according to the above aspect that is bag-shaped.

[0016] According to yet another aspect of the present invention, there is provided a packaged article comprising a package according to any one of the above aspects and contents contained in the package.

[0017] According to yet another aspect of the present invention, there is provided a packaged article according to the above aspect that has been retorted. [Effects of the Invention]

[0018] According to the present invention, the film constituting the laminate is made of a polyolefin film, and it is possible to realize a package that exhibits high resistance to retort treatment. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view schematically showing a part of a laminate according to a first embodiment of the present invention. [Figure 2] FIG. 6 is a cross-sectional view schematically showing a part of a laminate according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view schematically showing a part of a laminate according to a third embodiment of the present invention. [Figure 4] 1 is a perspective view schematically showing a package according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. Elements having the same or similar functions are designated by the same reference numerals, and redundant descriptions will be omitted.

[0021] <1> First embodiment FIG. 1 is a cross-sectional view schematically showing a part of a laminate according to a first embodiment of the present invention.

[0022] 1 can be used, for example, as a packaging material or a part thereof. Preferably, the laminate 10A is a packaging material for retort pouches or a part thereof.

[0023] The laminate 10A includes, in this order, a first substrate layer 1, a second substrate layer 2, and a sealant layer 3. The laminate 10A further includes a first adhesive layer 4 that bonds the first substrate layer 1 and the second substrate layer 2 to each other, and a second adhesive layer 5 that bonds the second substrate layer 2 and the sealant layer 3 to each other.

[0024] The laminate 10A is manufactured, for example, by a roll-to-roll process. As described below, the first substrate layer 1, the second substrate layer 2, and the sealant layer 3 each include a polyolefin film. The term "film" refers to a thin layer that can be handled independently from the manufacturing stage and is flexible, or a thin layer provided on a component of the laminate by extrusion lamination, but does not refer to a thin layer formed on a component of the laminate by coating, vapor deposition, or the like.

[0025] The laminate 10A is a film containing only polyolefins, which are the first base material layer 1, the second base material layer 2, and the sealant layer 3. Such a laminate 10A can be said to be made of a single material that is highly recyclable, i.e., a mono-material laminate. From this perspective, the total mass of components other than the polyolefin component, such as adhesives and ink components, relative to the total mass of the laminate 10A is preferably 10 mass% or less, and more preferably 7.5 mass% or less. The layers included in the laminate 10A will be explained below one by one.

[0026] <1.1>First base layer <1.1.1> Polyolefin film The first base layer 1 is made of a polyolefin film. Typically, the running direction of the polyolefin film contained in the first base layer 1 during production is the same as the running direction during production of the laminate 10A.

[0027] Examples of polyolefin films include polyethylene (PE), polypropylene (PP), and polybutene (PB) films. The polyolefin film may be an acid-modified polyolefin film obtained by graft-modifying a polyolefin with, for example, an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, or an ester of an unsaturated carboxylic acid.

[0028] The polyolefin film constituting the first base layer 1 may be a stretched film or a non-stretched film. From the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the polyolefin film is preferably a stretched film. The laminate 10A in which the polyolefin film of the first base layer 1 is a stretched film is suitable for applications in which a packaged article obtained by using this laminate 10A as at least a part of a packaging material is subjected to retort treatment or boiling treatment. The stretching method is not particularly limited, and any method may be used as long as it can supply a film with stable dimensions, such as stretching by inflation and uniaxial or biaxial stretching.

[0029] The thickness of the polyolefin film is not particularly limited, and can be, for example, within a range of 6 to 200 μm depending on the application, and from the viewpoint of obtaining excellent impact resistance and excellent gas barrier properties, the thickness is preferably within a range of 9 to 50 μm, and more preferably within a range of 12 to 38 μm.

[0030] The surface of the polyolefin film facing the second base layer 2 may be subjected to a surface modification treatment such as corona treatment, plasma treatment, or flame treatment, and may be provided with a coating layer such as an easy-adhesion layer.

[0031] <1.1.2> Printing layer The first substrate layer 1 may further include a printed layer on the surface facing the second substrate layer 2. The printed layer is provided in a position visible from the outside of the package, for example, to display information about the contents of the package obtained from the laminate 10A, to identify the contents, or to improve the design of the package. 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 characteristics 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 particularly preferred from the perspectives of productivity and high-resolution image formation. To improve the adhesion of the printed layer, the surface of the substrate may be subjected to a surface modification treatment such as corona treatment, plasma treatment, or flame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0032] <1.2>Second base layer The second base layer 2 includes a polyolefin film 21, an adhesive layer 22, a gas barrier vapor deposition layer 23, and a gas barrier coating layer 24 in this order from the sealant layer 3 side.

[0033] <1.2.1> Polyolefin film As the polyolefin film 21, the polyolefin film described above for the first base layer 1 can be used.

[0034] The polyolefin film 21 may be the same as or different from the polyolefin film of the first base material layer 1 in terms of material and thickness. From the viewpoint of recycling, it is preferable that the material of the polyolefin film 21 is the same as the material of the polyolefin film of the first base material layer 1. That is, when the first base material layer 1 is a polyethylene film, it is preferable that the polyolefin film 21 is also a polyethylene film. Furthermore, when the first base material layer 1 is a polypropylene film, it is preferable that the polyolefin film 21 is also a polypropylene film.

[0035] The polyolefin film 21 may have the same crystallinity or molecular chain orientation state as or different from the polyolefin film of the first base layer 1. Typically, the machine direction (MD) of the polyolefin film 21 during production is the same as the machine direction of the polyolefin film of the first base layer 1 during production.

[0036] <1.2.2> Adhesion layer The adhesion layer 22 is a layer that is sometimes called an anchor coat layer. Although the adhesion layer 22 can be omitted, providing it on the polyolefin film 21 has two effects: improving the adhesion between the polyolefin film 21 and the gas barrier vapor deposition layer 23, and improving the surface smoothness of the polyolefin film 21. Improved surface smoothness of the polyolefin film 21 makes it easier to form the gas barrier vapor deposition layer 23 uniformly without defects, making it easier to achieve high barrier properties. The adhesion layer 22 can be formed using an anchor coat agent.

[0037] Examples of the anchor coating agent include polyester-based polyurethane resins and polyether-based polyurethane resins. From the viewpoints of heat resistance and interlayer adhesive strength, polyester-based polyurethane resins are preferred as the anchor coating agent. The anchor coating agent may further contain a solvent in addition to the above resins.

[0038] The thickness of the adhesive layer 22 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. Increasing the thickness of the adhesive layer 22 tends to result in higher interlayer adhesive strength. However, increasing the thickness of the adhesive layer 22 tends to decrease the gas barrier properties.

[0039] The method for applying the anchor coating agent to the polyolefin film 21 can be any known application method without particular limitation, and examples thereof include immersion (dipping) and methods using a spray, coater, printer, brush, etc. In addition, examples of the types of coaters and printers used in these methods and their application methods include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, microgravure coaters, coaters combined with chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters.

[0040] The anchor coating agent is applied to the 1mm of the coating film after drying. 2 Mass per unit is 0.01 to 5 g / m 2 It is preferable to coat the coating amount so that the coating amount is in the range of 0.03 to 3 g / m 2 If the amount of anchor coating agent applied is small, discontinuities are likely to occur in the adhesive layer 22. On the other hand, if the amount of anchor coating agent applied is large, the coating film does not dry completely, and the solvent is likely to remain.

[0041] The method for drying the coating film is not particularly limited, but examples include natural drying, drying in an oven set at a predetermined temperature, and using a dryer attached to the coater, such as an arch dryer, floating dryer, drum dryer, or infrared dryer. The drying conditions for the coating film can be appropriately selected depending on the drying method. For example, in the method of drying the coating film in an oven, it is preferable to dry the coating film at a temperature in the range of 60 to 100°C for about 1 second to 2 minutes.

[0042] In the anchor coating agent, a polyvinyl alcohol resin can be used instead of the polyurethane resin. The polyvinyl alcohol resin may be any resin having a vinyl alcohol unit in which a vinyl ester unit is saponified, such as polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

[0043] 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.

[0044] The PVA may 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 and then saponifying the resulting copolymer. Examples of unsaturated monomers copolymerizable with the vinyl ester include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-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; and nitriles such as acrylonitrile and methacrylonitrile. Examples of suitable vinyl compounds include amides such as diacetone acrylamide, acrylamide, and methacrylamide; 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-vinylpyrrolidone, 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.

[0045] The degree of polymerization of PVA is preferably in the range of 300 to 3,000. A lower degree of polymerization of PVA tends to reduce barrier properties. A higher degree of polymerization of PVA tends to increase viscosity and reduce coatability. 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 K6726 (1994).

[0046] 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, and vinyl versatate.

[0047] The degree of polymerization of EVOH is preferably in the range of 300 to 3,000. A lower degree of polymerization of EVOH tends to reduce barrier properties. A higher degree of polymerization of EVOH tends to increase viscosity and reduce coatability. 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 may be 99.9 mol% or less. The degree of saponification of EVOH is determined from the peak area of ​​hydrogen atoms contained in the vinyl ester structure and the peak area of ​​hydrogen atoms contained in the vinyl alcohol structure, obtained by nuclear magnetic resonance (H-NMR) measurement.

[0048] The ethylene unit content of EVOH is preferably 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. A high ethylene unit content is advantageous in maintaining good gas barrier properties or dimensional stability under high humidity conditions. On the other hand, a low ethylene unit content is advantageous in achieving high gas barrier properties. The ethylene unit content of EVOH can be determined by NMR.

[0049] <1.2.3> Gas barrier vapor deposition layer The gas barrier vapor-deposited layer 23 is a layer that imparts gas barrier properties to the laminate 10A together with the gas barrier coating layer 24. The gas barrier vapor-deposited layer 23 is a layer formed by vacuum film formation, as will be described later.

[0050] The gas barrier vapor-deposited layer 23 is made of, for example, an inorganic oxide. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the inorganic oxide is preferably selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, from the viewpoint of excellent tensile stretchability during processing, the gas barrier vapor-deposited layer 23 is preferably a layer made of silicon oxide. The gas barrier vapor-deposited layer 23 can achieve high barrier properties while maintaining a thickness within a range that does not affect the recyclability of the laminate 10A.

[0051] When the gas barrier vapor-deposited layer 23 is made of silicon oxide, the atomic ratio of oxygen atoms to silicon atoms in the gas barrier vapor-deposited layer 23, O / Si, is preferably 1.7 or more, more preferably 1.75 or more, and even more preferably 1.8 or more. A smaller atomic ratio O / Si increases the proportion of Si atoms, resulting in a decrease in transparency. The atomic ratio O / Si is preferably 2.0 or less, more preferably 1.9 or less, and even more preferably 1.85 or less.

[0052] If the atomic ratio O / Si is too large, the crystallinity of silicon oxide increases, making the gas barrier vapor-deposited layer 23 too hard and reducing its tensile strength. If the gas barrier vapor-deposited layer 23 has high tensile strength, cracks are less likely to occur in the gas barrier vapor-deposited layer 23 when the gas barrier coating layer 24 is laminated. Furthermore, if the gas barrier vapor-deposited layer 23 has high tensile strength, even if the polyolefin film shrinks due to the heat applied during retort treatment or boiling treatment, the gas barrier vapor-deposited layer 23 will sufficiently adapt to the shrinkage and will be less likely to reduce its barrier properties.

[0053] The atomic ratio O / Si can be determined by X-ray photoelectron spectroscopy (XPS). For example, an X-ray photoelectron spectrometer (JPS-90MXV manufactured by JEOL Ltd.) is used, and the X-ray source is non-monochromated MgKα (1253.6 eV), with an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the atomic ratio O / Si, relative sensitivity factors of 2.28 and 0.9 can be used for O1s and Si2p, respectively.

[0054] The thickness of the gas barrier vapor-deposited layer 23 is preferably in the range of 10 to 50 nm, and more preferably in the range of 20 to 40 nm. If the thickness of the gas barrier vapor-deposited layer 23 is reduced, the water vapor barrier property is reduced. If the thickness of the gas barrier vapor-deposited layer 23 is increased, cracks are likely to occur due to deformation caused by internal stress, which is likely to result in a reduction in the water vapor barrier property. Furthermore, if the thickness of the gas barrier vapor-deposited layer 23 is increased, costs are likely to increase due to an increase in the amount of material used and a longer film formation time, making it undesirable from an economic standpoint.

[0055] The gas barrier vapor deposition layer 23 can be formed by vacuum deposition. Vacuum deposition is performed by physical vapor deposition or chemical vapor deposition. Physical vapor deposition methods include, but are not limited to, vacuum deposition, sputtering, and ion plating. Chemical vapor deposition methods include, but are not limited to, thermal chemical vapor deposition (CVD), plasma CVD, and photo CVD.

[0056] In the vacuum film formation, resistance heating vacuum evaporation, electron beam (EB) heating vacuum evaporation, induction heating vacuum evaporation, sputtering, reactive sputtering, dual magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), and the like are particularly preferably used. In terms of productivity, vacuum evaporation is currently the most superior. As a heating means for vacuum evaporation, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method.

[0057] <1.2.4> Gas barrier coating layer The gas barrier coating layer 24 is a layer that imparts gas barrier properties to the laminate 10A together with the gas barrier vapor deposition layer 23. The gas barrier coating layer 24 is a layer formed by applying a coating liquid, as will be described later.

[0058] The thickness of the gas barrier coating layer 24 is preferably in the range of 50 to 1,000 nm, and more preferably in the range of 100 to 500 nm. Increasing the thickness of the gas barrier coating layer 24 tends to provide higher gas barrier properties. However, increasing the thickness of the gas barrier coating layer 24 reduces the flexibility of the laminate 10A.

[0059] (First coating liquid) According to one example, the gas barrier coating layer 24 is a cured product of a first coating liquid containing one or more selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and hydrolysates thereof. The first coating liquid may further contain water or a mixture of water and alcohol as a solvent.

[0060] From the viewpoint of maintaining high gas barrier properties even after hot water treatment such as retort treatment, the first coating liquid preferably contains at least a silane coupling agent or a hydrolysate thereof, more preferably contains at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, and a hydrolysate thereof, and a silane coupling agent or a hydrolysate thereof, and even more preferably contains a hydroxyl group-containing polymer compound or a hydrolysate thereof, a metal alkoxide or a hydrolysate thereof, and a silane coupling agent or a hydrolysate thereof.

[0061] The first coating liquid can be obtained, for example, by mixing a metal alkoxide and a silane coupling agent directly with a solution obtained by dissolving a hydroxyl group-containing polymer compound, which is a water-soluble polymer, in an aqueous solvent, i.e., water or a mixture of water and alcohol, or by mixing a solution that has been previously treated by hydrolysis or the like with the metal alkoxide and the silane coupling agent.

[0062] Each component contained in the first coating liquid will now be described in detail. Examples of hydroxyl group-containing polymer compounds include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. Among these, when polyvinyl alcohol (PVA) is used, particularly excellent gas barrier properties can be achieved.

[0063] From the viewpoint of obtaining excellent gas barrier properties, the first coating liquid preferably contains at least one selected from the group consisting of metal alkoxides represented by the following general formula (I) and hydrolysates thereof.

[0064] M(OR1) m (R2) n-m …(I) In the general formula (I), R1 and R2 are each independently a monovalent organic group having 1 to 8 carbon atoms, preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent atom such as Si, Ti, Al, or Zr. m is an integer of 1 to n. When there are multiple R1s or R2s, the R1s or R2s may be the same or different.

[0065] Specific examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(O-2'-C3H7)3]. Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis.

[0066] The silane coupling agent includes a compound represented by the following general formula (II).

[0067] Si(OR11) p (R12) 3-p R13 … (II) In the general formula (II), R11 represents an alkyl group such as a methyl group or an ethyl group. R12 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. R13 represents a monovalent organic functional group. p represents an integer of 1 to 3. When multiple R11 or R12 are present, the R11s or R12s may be the same or different. Examples of the monovalent organic functional group represented by R13 include a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, and a monovalent organic functional group containing an isocyanate group.

[0068] Specific examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0069] The silane coupling agent may be a polymer formed by polymerizing the compound represented by the general formula (II). As the polymer, a trimer is preferred, and 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is more preferred. 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is a condensation polymer of 3-isocyanate alkylalkoxysilane.

[0070] 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. 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is generally known as an adhesion improver added to adhesives, etc., similar to 3-isocyanate alkylalkoxysilane. Therefore, when 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is added to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer 24 can be improved by hydrogen bonding.

[0071] Furthermore, while 3-isocyanate alkyl alkoxysilanes are highly reactive and have 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 performance that can be achieved is equivalent between 3-isocyanate alkyl alkoxysilanes and 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates.

[0072] Note that 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurates are sometimes produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and therefore may contain the raw material 3-isocyanatepropylalkoxysilane. The presence of such raw material does not pose any particular problems.

[0073] The silane coupling agent is more preferably 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate, and even more preferably 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate. Silane coupling agents containing methoxy groups have a fast hydrolysis rate, and those containing propyl groups are relatively inexpensive. Therefore, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is particularly preferred.

[0074] It is also possible to add known additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity modifier, and a colorant to the first coating agent, as long as the gas barrier properties are not impaired.

[0075] The first coating liquid can be applied to the gas barrier vapor deposition layer 23 by, for example, dipping, roll coating, gravure coating, reverse gravure coating, air knife coating, comma coating, die coating, screen printing, spray coating, or gravure offset. The coating film obtained by applying the first coating liquid can be dried by, for example, hot air drying, hot roll drying, high frequency irradiation, infrared irradiation, ultraviolet (UV) irradiation, or a combination thereof.

[0076] The temperature at which the coating film is dried is preferably in the range of 50 to 150° C., and more preferably in the range of 70 to 100° C. By keeping the drying temperature within the above range, the occurrence of cracks in the gas barrier vapor deposition layer 23 and the gas barrier coating layer 24 can be further suppressed, and particularly excellent barrier properties can be achieved.

[0077] (Second coating liquid) In another example, the gas barrier coating layer 24 is a cured product of a second coating liquid containing a polyvinyl alcohol resin and a silane compound. If necessary, an acid catalyst, an alkali catalyst, or a photopolymerization initiator may be added to the second coating liquid.

[0078] Examples of the silane compound include a silane coupling agent, a polysilazane, and a siloxane. Specific examples of the silane compound include tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and hexamethyldisilazane.

[0079] (Third coating liquid) In yet another example, the gas barrier coating layer 24 is a cured product of a third coating liquid containing a carboxyl group-containing polymer (A), polyvalent metal-containing particles (B), a surfactant (C), an organic solvent (D), and at least one silicon-containing compound (E) selected from the group consisting of a silane coupling agent represented by the following general formula (4), a silane coupling agent represented by the following general formula (5), their hydrolysates, and their condensates:

[0080] Si(OR1)3Z1 …(4) Si(R2)(OR3)2Z2 …(5) In the above general formula (4), R1 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z1 is a group containing an epoxy group.

[0081] In the above general formula (5), R2 is a methyl group, R3 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z2 is a group containing an epoxy group.

[0082] [Carboxy group-containing polymer (A)] The carboxyl group-containing polymer used in the third coating liquid is a polymer having two or more carboxyl groups in its molecule, and is sometimes called a "polycarboxylic acid polymer." Representative examples of carboxyl group-containing polymers include homopolymers of carboxyl group-containing unsaturated monomers, copolymers of two or more carboxyl group-containing unsaturated monomers, copolymers of carboxyl group-containing unsaturated monomers with other polymerizable monomers, and polysaccharides containing carboxyl groups in their molecules (also called "carboxyl group-containing polysaccharides" or "acidic polysaccharides").

[0083] The carboxy group includes not only a free carboxy group but also an acid anhydride group (specifically, a dicarboxylic acid anhydride group). The acid anhydride group may be partially ring-opened to form a carboxy group. A portion of the carboxy group may be neutralized with an alkali. In this case, the degree of neutralization is preferably 20% or less.

[0084] Here, the "degree of neutralization" is a value obtained by the following method. That is, the carboxy groups in the carboxy group-containing polymer (A) can be partially neutralized by adding an alkali (F). In this case, the ratio of the number of moles (Ft) of the alkali (F) to the number of moles (At) of the carboxy groups contained in the carboxy group-containing polymer (A) is the degree of neutralization.

[0085] In addition, a graft polymer obtained by graft polymerizing a carboxyl-containing unsaturated monomer onto a polymer not containing a carboxyl group, such as a polyolefin, can also be used as the carboxyl-containing polymer. A polymer obtained by hydrolyzing a polymer having a hydrolyzable ester group such as an alkoxycarbonyl group (e.g., a methoxycarbonyl group) to convert it into a carboxyl group can also be used.

[0086] The carboxyl group-containing unsaturated monomer is preferably an α,β-monoethylenically unsaturated carboxylic acid. Therefore, the carboxyl group-containing polymer includes a homopolymer of an α,β-monoethylenically unsaturated carboxylic acid, a copolymer of two or more α,β-monoethylenically unsaturated carboxylic acids, and a copolymer of an α,β-monoethylenically unsaturated carboxylic acid with another polymerizable monomer. A typical example of the other polymerizable monomer is an ethylenically unsaturated monomer.

[0087] Examples of α,β-monoethylenically unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride; and mixtures of two or more of these. Among these, at least one α,β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid is preferred, and at least one α,β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, and maleic acid is more preferred.

[0088] Other polymerizable monomers copolymerizable with α,β-monoethylenically unsaturated carboxylic acids, particularly ethylenically unsaturated monomers, include, for example, ethylene; α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene; saturated carboxylic acid vinyl esters such as vinyl acetate; acrylic acid alkyl esters such as methyl acrylate and ethyl acrylate; methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate; chlorine-containing vinyl monomers such as vinyl chloride and vinylidene chloride; fluorine-containing vinyl monomers such as vinyl fluoride and vinylidene fluoride; unsaturated nitriles such as acrylonitrile and methacrylonitrile; aromatic vinyl monomers such as styrene and α-methylstyrene; and itaconic acid alkyl esters. These ethylenically unsaturated monomers can be used alone or in combination of two or more. Furthermore, when the carboxy group-containing polymer is a copolymer of an α,β-monoethylenically unsaturated carboxylic acid and a saturated carboxylic acid vinyl ester such as vinyl acetate, a copolymer obtained by saponifying this copolymer to convert the saturated carboxylic acid vinyl ester units into vinyl alcohol units can also be used.

[0089] Examples of carboxyl group-containing polysaccharides include acidic polysaccharides having a carboxyl group in the molecule, such as alginic acid, carboxymethylcellulose, and pectin. These acidic polysaccharides can be used alone or in combination of two or more. Acidic polysaccharides can also be used in combination with (co)polymers of α,β-monoethylenically unsaturated carboxylic acids.

[0090] When the carboxy group-containing polymer is a copolymer of an α,β-monoethylenically unsaturated carboxylic acid and another ethylenically unsaturated monomer, from the viewpoint of the gas barrier property, hot water resistance, and water vapor resistance of the resulting film, the proportion of the number of moles of the α,β-monoethylenically unsaturated carboxylic acid monomer to the total number of moles of those monomers in the copolymer is preferably 60 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

[0091] The carboxyl group-containing polymer is preferably a homopolymer or copolymer obtained by polymerization of only α,β-monoethylenically unsaturated carboxylic acid, since it is easy to obtain a film that has excellent gas barrier properties, moisture resistance, water resistance, hot water resistance, and water vapor resistance, and that also has excellent gas barrier properties under high humidity conditions. When the carboxyl group-containing polymer is a (co)polymer consisting of only α,β-monoethylenically unsaturated carboxylic acid, preferred examples include homopolymers, copolymers, and mixtures of two or more thereof obtained by polymerization of at least one α,β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Among these, homopolymers and copolymers of at least one α,β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, and maleic acid are more preferred.

[0092] As the carboxyl group-containing polymer, polyacrylic acid, polymethacrylic acid, polymaleic acid, and a mixture of two or more thereof are particularly preferred. As the acidic polysaccharide, alginic acid is preferred. Among these, polyacrylic acid is particularly preferred because it is relatively easy to obtain and can easily produce a film with excellent physical properties.

[0093] The number average molecular weight of the carboxy group-containing polymer is not particularly limited, but from the viewpoint of film formability and film physical properties, the number average molecular weight is preferably in the range of 2,000 to 10,000,000, more preferably in the range of 5,000 to 1,000,000, and even more preferably in the range of 10,000 to 500,000.

[0094] Here, the "number average molecular weight" is a value obtained by measurement using gel permeation chromatography (GPC). In GPC measurement, the number average molecular weight of a polymer is generally measured in terms of standard polystyrene.

[0095] [Polyvalent metal-containing particles (B)] The polyvalent metal-containing particles used in the third coating liquid are particles containing one or more polyvalent metals whose metal ions have a valence of 2 or more. The polyvalent metal-containing particles may be particles made of a polyvalent metal whose metal ions have a valence of 2 or more, particles made of a compound of a polyvalent metal whose metal ions have a valence of 2 or more, or a mixture thereof.

[0096] Specific examples of polyvalent metals include, but are not limited to, metals in Group 2A of the short periodic table, such as beryllium, magnesium, and calcium; transition metals, such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, and zinc; and aluminum.

[0097] The polyvalent metal is preferably a divalent metal, and the polyvalent metal preferably forms a compound.

[0098] Specific examples of polyvalent metal compounds include, but are not limited to, oxides, hydroxides, carbonates, organic acid salts, and inorganic acid salts of polyvalent metals. Examples of organic acid salts include, but are not limited to, acetates, oxalates, citrates, lactates, phosphates, phosphites, hypophosphites, stearates, and monoethylenically unsaturated carboxylates. Examples of inorganic acid salts include, but are not limited to, chlorides, sulfates, and nitrates. Alkyl alkoxides of polyvalent metals can also be used as polyvalent metal compounds. These polyvalent metal compounds can be used alone or in combination of two or more.

[0099] Among polyvalent metal compounds, from the viewpoint of the dispersion stability of the third coating liquid and the gas barrier properties of the laminate 10A, compounds of beryllium, magnesium, calcium, copper, cobalt, nickel, zinc, aluminum, and zirconium are preferred, and compounds of divalent metals such as beryllium, magnesium, calcium, copper, zinc, cobalt, and nickel are more preferred.

[0100] Preferred divalent metal compounds include, but are not limited to, oxides such as zinc oxide, magnesium oxide, copper oxide, nickel oxide, and cobalt oxide; carbonates such as calcium carbonate; organic acid salts such as calcium lactate, zinc lactate, and calcium acrylate; and alkoxides such as magnesium methoxide.

[0101] The polyvalent metal or polyvalent metal compound is used as particles, and the particle shape is maintained even in the third coating liquid. From the viewpoints of dispersion stability of the third coating liquid and the gas barrier properties of the laminate 10A, the average particle diameter of the polyvalent metal-containing particles in the third coating liquid is preferably within the range of 10 nm to 10 μm (or 10,000 nm), more preferably within the range of 12 nm to 1 μm (or 1,000 nm), even more preferably within the range of 15 to 500 nm, and particularly preferably within the range of 15 to 50 nm.

[0102] If the average particle size of the polyvalent metal-containing particles in the third coating liquid is too large, the resulting coating layer tends to have insufficient uniformity in film thickness, surface flatness, and ionic crosslinking reactivity with the carboxyl group-containing polymer. If the average particle size of the polyvalent metal-containing particles is too small, the ionic crosslinking reaction with the carboxyl group-containing polymer may proceed prematurely. Furthermore, it is difficult to uniformly disperse ultrafine particles with a particle size of less than 10 nm in the third coating liquid.

[0103] When the sample is a dry solid, the average particle size of the polyvalent metal-containing particles can be measured by measuring and counting using a scanning electron microscope or a transmission electron microscope. The average particle size of the polyvalent metal-containing particles in the third coating liquid can be measured by a light scattering method (Reference: "Fine Particle Engineering System," Vol. 1, pp. 362-365, Fuji Techno System (2001)).

[0104] The polyvalent metal-containing particles in the third coating liquid exist as primary particles, secondary particles, or a mixture thereof, but in most cases, judging from the average particle size, it is estimated that they exist as secondary particles.

[0105] [Surfactant (C)] In the third coating liquid, a surfactant is used to improve the dispersibility of the polyvalent metal-containing particles. A surfactant is a compound that has both a hydrophilic group and a lipophilic group in its molecule. Surfactants include anionic, cationic, and amphoteric ionic surfactants, as well as nonionic surfactants. Any surfactant may be used in the third coating liquid.

[0106] Anionic surfactants include, for example, carboxylic acid type, sulfonic acid type, sulfate ester type, and phosphate ester type. Examples of carboxylic acid type anionic surfactants include aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosinates, and N-acylglutamates. Examples of sulfonic acid type anionic surfactants include dialkyl sulfosuccinates, alkanesulfonates, alphaolefin sulfonates, linear alkylbenzene sulfonates, alkyl (branched)benzene sulfonates, naphthalene sulfonate-formaldehyde condensates, alkylnaphthalene sulfonates, and N-methyl-N-acyltaurates. Examples of sulfate ester type anionic surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fat sulfate esters. Examples of phosphate ester type anionic surfactants include alkyl phosphates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkylphenyl ether phosphates.

[0107] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of alkylamine salt cationic surfactants include monoalkylamine salts, dialkylamine salts, and trialkylamine salts. Examples of quaternary ammonium salt cationic surfactants include alkyltrimethylammonium halide (chloride, bromide, or iodide) salts and alkylbenzalkonium chloride.

[0108] Examples of amphoteric surfactants include carboxybetaine type, 2-alkylimidazoline derivative type, glycine type, and amine oxide type. Examples of carboxybetaine type amphoteric surfactants include alkylbetaine and fatty acid amidopropyl betaine. Examples of 2-alkylimidazoline derivative type amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine. Examples of glycine type amphoteric surfactants include alkyl or dialkyldiethylenetriaminoacetic acid. Examples of amine oxide type amphoteric surfactants include alkylamine oxide.

[0109] Nonionic surfactants include, for example, ester type, ether type, ester ether type, and alkanolamide type. Ester type nonionic surfactants include, for example, glycerin fatty acid ester, sorbitan fatty acid ester, and sucrose fatty acid ester. Ether type nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene polyoxypropylene glycol. Ester ether type nonionic surfactants include, for example, fatty acid polyethylene glycol and fatty acid polyoxyethylene sorbitan. Alkanolamide type nonionic surfactants include, for example, fatty acid alkanolamide.

[0110] Surfactants having a polymer backbone, such as styrene-acrylic acid copolymers, can also be used.

[0111] Among these surfactants, anionic surfactants such as phosphate esters and surfactants having a polymer skeleton such as styrene-acrylic acid copolymers are preferred.

[0112] [Organic solvent (D)] The third coating liquid uses an organic solvent as a solvent or dispersion medium. As the organic solvent, a polar organic solvent that dissolves the carboxyl group-containing polymer is generally used, but an organic solvent that does not have a polar group (heteroatom or atomic group having a heteroatom) may be used in combination with the polar organic solvent.

[0113] Examples of organic solvents that can be preferably used include alcohols such as methanol, ethanol, isopropanol, n-propanol, and n-butanol; and polar organic solvents such as dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, tetramethylurea, hexamethylphosphoric triamide, and γ-butyrolactone.

[0114] In addition to the polar organic solvents described above, hydrocarbons such as benzene, toluene, xylene, hexane, heptane, and octane; ketones such as acetone and methyl ethyl ketone; halogenated hydrocarbons such as dichloromethane; esters such as methyl acetate; and ethers such as diethyl ether can be used as appropriate. Hydrocarbons such as benzene that do not have a polar group are generally used in combination with a polar organic solvent.

[0115] The third coating liquid may contain only an organic solvent as a solvent or dispersion medium, or may further contain water. By adding water, the solubility of the carboxyl group-containing polymer can be improved, and the coatability and workability of the third coating liquid can be improved. The water content of the third coating liquid may be 100 ppm or more, 1,000 ppm or more, 1,500 ppm or more, or 2,000 ppm or more by mass fraction.

[0116] The water content of the third coating liquid is preferably 50,000 ppm or less, more preferably 10,000 ppm or less, and even more preferably 5,000 ppm or less, in terms of mass fraction.

[0117] [Silicon-containing compounds (E)] The third coating liquid contains a silicon-containing compound to enhance peel strength, which is at least one compound selected from the group consisting of a silane coupling agent represented by the following general formula (4), a silane coupling agent represented by the following general formula (5), their hydrolysates, and their condensates: Si(OR1)3Z1 …(4) Si(R2)(OR3)2Z2 …(5) Here, the mass of the silicon-containing compound (E) is the mass calculated as the silane coupling agent. In general formula (4), R1 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z1 is a group containing an epoxy group. In general formula (5), R2 is a methyl group, R3 may be the same or different and is an alkyl group having 1 to 6 carbon atoms, and Z2 is a group containing an epoxy group.

[0118] Silane coupling agents readily undergo hydrolysis and readily undergo condensation reactions in the presence of acid or alkali. Therefore, in the third coating liquid, the silicon-containing compound (E) rarely exists solely in the form of the silane coupling agent represented by general formula (4) or (5), solely in the form of its hydrolysate, or solely in the form of its condensate. That is, in the third coating liquid, the silicon-containing compound (E) is usually present as a mixture of at least one of the silane coupling agent represented by general formula (4) and the silane coupling agent represented by general formula (5), its hydrolysate, and its condensate.

[0119] Each of R1 and R3 may be an alkyl group having 1 to 6 carbon atoms, and is preferably a methyl group or an ethyl group. Each of Z1 and Z2 may be a group containing an epoxy group.

[0120] Specific examples of the silane coupling agent represented by general formula (4) or (5) include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane, with 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropyltrimethoxysilane being preferred. As the silane coupling agent, one type may be used, or two or more types may be used.

[0121] The hydrolysate of the silane coupling agent represented by general formula (4) or (5) may be a partial hydrolysate, a complete hydrolysate, or a mixture thereof.

[0122] The condensates contained in the third coating liquid as at least a portion of the silicon-containing compound (E) are at least two of the following: a hydrolysis condensate of a silane coupling agent represented by general formula (4), a hydrolysis condensate of a silane coupling agent represented by general formula (5), and a condensate of a hydrolysis condensate of a silane coupling agent represented by general formula (4) and a hydrolysis condensate of a silane coupling agent represented by general formula (5). These hydrolysis condensates are produced by the following reaction: First, the silane coupling agent is hydrolyzed. As a result, one or more alkoxy groups contained in the silane coupling agent molecule are replaced with hydroxyl groups, resulting in a hydrolysis product. Subsequently, these hydrolysis products are condensed to form a compound in which silicon atoms (Si) are bonded via oxygen. This condensation is repeated to obtain the hydrolysis condensate.

[0123] 〔composition〕 The third coating liquid contains a carboxy group-containing polymer (A), polyvalent metal-containing particles (B), a surfactant (C), an organic solvent (D), and a silicon-containing compound (E), and is a dispersion liquid in which the polyvalent metal-containing particles are dispersed.

[0124] The ratio (hereinafter also referred to as equivalent ratio) of the product (Bt) of the number of moles of polyvalent metal and its valence contained in the polyvalent metal-containing particles (B) to the number of moles (At) of carboxy groups contained in the carboxy group-containing polymer (A) is preferably 0.6 or more. This ratio is more preferably 0.8 or more, and particularly preferably 1.0 or more. The upper limit of this ratio is usually 10.0, preferably 2.0. If this ratio is too small, the properties of the laminate having a coating layer formed from the coating liquid, such as gas barrier properties, hot water resistance, and water vapor resistance, will be reduced.

[0125] The above equivalent ratio can be determined, for example, as follows: An example will be described in which the carboxyl group-containing polymer is polyacrylic acid and the polyvalent metal compound is magnesium oxide.

[0126] Polyacrylic acid has a molecular weight of 72 per monomer unit and one carboxy group per monomer molecule. Therefore, the amount of carboxy groups in 100 g of polyacrylic acid is 1.39 moles. An equivalent ratio of 1.0 in a coating solution containing 100 g of polyacrylic acid means that the coating solution contains enough magnesium oxide to neutralize 1.39 moles of carboxy groups. Therefore, to achieve an equivalent ratio of 0.6 in a coating solution containing 100 g of polyacrylic acid, magnesium oxide must be added to the coating solution in an amount sufficient to neutralize 0.834 moles of carboxy groups. The magnesium valence is divalent, and the molecular weight of magnesium oxide is 40. Therefore, to achieve an equivalent ratio of 0.6 in a coating solution containing 100 g of polyacrylic acid, 16.68 g (0.417 moles) of magnesium oxide must be added to the coating solution.

[0127] The organic solvent is used in an amount sufficient to uniformly dissolve the carboxyl group-containing polymer and uniformly disperse the polyvalent metal-containing particles. Therefore, the organic solvent used is one that dissolves the carboxyl group-containing polymer but does not substantially dissolve the polyvalent metal compound and can disperse it in the form of particles.

[0128] The surfactant is used in an amount sufficient to stably disperse the polyvalent metal-containing particles. The concentration of the surfactant in the third coating liquid is usually in the range of 0.0001 to 70% by mass, preferably 0.001 to 60% by mass, and more preferably 0.1 to 50% by mass.

[0129] Without the addition of a surfactant, it is difficult to disperse the polyvalent metal-containing particles in the third coating liquid to a sufficiently small average particle size, which makes it difficult to obtain a coating liquid in which the polyvalent metal-containing particles are uniformly dispersed, and therefore difficult to form a coating film with a uniform thickness when applied to a substrate.

[0130] The mass ratio of the silicon-containing compound to the carboxyl group-containing polymer (wherein the mass of the silicon-containing compound is the mass of the silane coupling agent) is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, and particularly preferably 2.0% or more.

[0131] If the amount of silicon-containing compound added is too small, the peel strength of the laminate 10A will be low, which will require careful handling to prevent delamination, leading to reduced productivity.

[0132] The mass ratio of the silicon-containing compound to the carboxyl group-containing polymer is preferably 20% or less, more preferably 15% or less, even more preferably 12% or less, and particularly preferably 7% or less.

[0133] Silicon-containing compounds do not have gas barrier properties, so if the amount of silicon-containing compound added is too large, the gas barrier properties of the laminate 10A will decrease.

[0134] [Method for producing third coating liquid] To produce the third coating liquid, first, the carboxyl group-containing polymer (A) is uniformly dissolved in the organic solvent (D), and then the silicon-containing compound (E) is added thereto to prepare a carboxyl group-containing polymer solution.

[0135] On the other hand, polyvalent metal-containing particles (B), surfactant (C), and organic solvent (D) are mixed and, if necessary, subjected to a dispersion treatment to prepare a dispersion liquid. The dispersion treatment is performed so that the average particle diameter of the polyvalent metal-containing particles (B) reaches a predetermined value. If the average particle diameter of the polyvalent metal-containing particles (B) in the mixed liquid before the dispersion treatment is 10 μm or less, the dispersion treatment is not necessary; however, even in this case, the dispersion treatment is preferable. The dispersion treatment disaggregates the polyvalent metal-containing particles (B), stabilizing the third coating liquid and improving the transparency of the laminate 10A obtained by applying the third coating liquid. Furthermore, when the third coating liquid is applied and the coating is dried, crosslinking between the carboxyl group-containing polymer and polyvalent metal ions is facilitated, making it easier to obtain a laminate 10A with good gas barrier properties.

[0136] Dispersion methods include those using a high-speed stirrer, homogenizer, ball mill, or bead mill. Dispersion using a ball mill or bead mill can achieve high dispersion efficiency, and therefore a stable third coating liquid can be obtained in a relatively short time. In this case, the diameter of the balls or beads should be small, preferably 0.1 to 1 mm.

[0137] The third coating liquid can be prepared by mixing the carboxyl group-containing polymer solution prepared as described above with the dispersion of polyvalent metal-containing particles. The silicon-containing compound (E) may be omitted from the carboxyl group-containing polymer solution. In this case, the silicon-containing compound (E) is mixed together with the carboxyl group-containing polymer solution and the dispersion of polyvalent metal-containing particles, for example, when they are mixed together.

[0138] The total concentration of the components other than the organic solvent in the third coating liquid is preferably within the range of 0.1 to 60 mass%, more preferably 0.5 to 25 mass%, and particularly preferably 1 to 20 mass%, in order to obtain a coating film and a coating layer of a desired thickness with high workability.

[0139] The third coating liquid may contain various additives, such as other polymers, thickeners, stabilizers, UV absorbers, antiblocking agents, softeners, inorganic layered compounds (e.g., montmorillonite), and colorants (dyes, pigments), as needed.

[0140] <1.3> Sealant layer The sealant layer 3 is a layer that provides heat-sealing properties to the laminate 10A and contains a polyolefin film. The sealant layer 3 is made of, for example, a polyolefin film. Typically, the running direction of the polyolefin film contained in the sealant layer 3 during production is the same as the running direction of the polyolefin film of the first base layer 1 during production.

[0141] The sealant layer 3 is made of a thermoplastic resin, such as a polyolefin resin. Specific examples of polyolefin resins include ethylene resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-(meth)acrylic acid copolymer; blends of polyethylene and polybutene; and polypropylene resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer. These thermoplastic resins can be selected appropriately depending on the application of the package and the temperature conditions in the retort and boiling treatments.

[0142] From the viewpoint of recycling, it is preferable that the material of the polyolefin film contained in the sealant layer 3 is the same as the material of the polyolefin films of the first base material layer 1 and the second base material layer 2. That is, when the polyolefin film contained in the first base material layer 1 and the second base material layer 2 is a polyethylene film, it is preferable that the polyolefin film contained in the sealant layer 3 is also a polyethylene film. Furthermore, when the polyolefin film contained in the first base material layer 1 and the second base material layer 2 is a polypropylene film, it is preferable that the polyolefin film contained in the sealant layer 3 is also a polypropylene film.

[0143] The polyolefin film contained in the sealant layer 3 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0144] The thickness of the sealant layer 3 is determined appropriately depending on the mass of the contents to be contained in the package obtained from the laminate 10A, the shape of the package, etc., but is preferably within the range of approximately 30 to 150 μm.

[0145] <1.4>Adhesive layer The first adhesive layer 4 bonds the first base material layer 1 and the second base material layer 2 to each other. The first adhesive layer 4 is made of a first adhesive. As the first adhesive, for example, a polyester-isocyanate resin, a urethane resin, or a polyether resin can be used. When using a package obtained from the laminate 10A for retort applications, from the viewpoint of retort resistance, it is preferable to bond the first base material layer 1 and the second base material layer 2 to each other by a dry lamination method using an adhesive such as a one-component curing or two-component curing urethane adhesive, particularly a two-component curing urethane adhesive, as the first adhesive.

[0146] The second adhesive layer 5 bonds the second base material layer 2 and the sealant layer 3 to each other. The second adhesive layer 5 is made of a second adhesive. The second base material layer 2 and the sealant layer 3 can be bonded to each other by, for example, a dry lamination method using an adhesive such as a one-component curing or two-component curing urethane adhesive as the second adhesive. Alternatively, the second base material layer 2 and the sealant layer 3 can be bonded to each other by a non-solvent dry lamination method using a solvent-free adhesive as the second adhesive.

[0147] Among the above methods, the dry lamination method is particularly advantageous in achieving high resistance to retort treatment, particularly high-temperature hot water treatment at 120° C. or higher. However, there are no particular restrictions on the lamination method as long as the package is used for applications where it will be treated at a temperature of 85° C. or lower.

[0148] Heating during bonding of the first base material layer 1 and the second base material layer 2 and during bonding of the second base material layer 2 and the sealant layer 3 is preferably carried out at a temperature of 85° C. or lower, more preferably at a temperature of 70° C. or lower. If high-temperature heat treatment is carried out in the production of the laminate 10A, cracks or peeling from the base material will occur in the gas barrier vapor deposition layer 23 and the gas barrier coating layer 24, resulting in a decrease in barrier performance.

[0149] Heating during bonding between the first base material layer 1 and the second base material layer 2 and between the second base material layer 2 and the sealant layer 3 is preferably carried out at a temperature of 50° C. or higher, more preferably at a temperature of 60° C. or higher. If the temperature is lowered, productivity decreases.

[0150] The sealant layer 3 may be provided on the second base material layer 2 by extrusion lamination, in which a thermoplastic resin is heated and melted, extruded in the form of a curtain onto the second base material layer 2, and then bonded to the second base material layer 2. In this case, the second adhesive layer 5 can be omitted.

[0151] <1.5> Heat shrinkage rate In the laminate 10A, the heat shrinkage rate x1 in the running direction (MD) of the first base material layer after heating at 120°C for 15 minutes, the heat shrinkage rate x2 in the running direction of the second base material layer after heating at 120°C for 15 minutes, and the heat shrinkage rate x3 in the running direction of the sealant layer after heating at 120°C for 15 minutes satisfy the relationships shown in the following formulas (1) to (3). x2≦2.5% …(1) -1.0%≦x2-x1 …(2) -0.2%≦x2-x3 …(3) Here, each of the heat shrinkage rates x1, x2, and x3 is a value obtained by multiplying the ratio (L0-L1) / L0 of the difference (L0-L1) between the running direction length L0 before heating and the running direction length L1 after heating to the running direction length L0 before heating by 100. Specifically, each of the heat shrinkage rates x1, x2, and x3 is measured by the following procedure.

[0152] First, a measurement sample having a square shape with a side length of 20 cm is cut out from the layer to be measured. Next, at room temperature, a line parallel to the running direction and 10 cm long is drawn on one side of the measurement sample. The running direction length L0 before heating is the length of this line (10 cm). Next, the measurement sample is heated at 120°C for 15 minutes. The measurement sample is cooled to room temperature, and the length of the line is measured. The running direction length L1 after heating is the length of this line. The thermal shrinkage is then calculated from the running direction lengths L0 and L1 obtained in this way.

[0153] As is clear from the above formulas (1) and (2), the heat shrinkage rate x1 is 3.5% or less. The heat shrinkage rate x1 is preferably 2% or less. The heat shrinkage rate x1 is 0% or more.

[0154] As shown in the above formula (1), the heat shrinkage rate x2 is 2.5% or less. The heat shrinkage rate x2 is preferably 2% or less. The heat shrinkage rate x2 is 0% or more, preferably 0.4% or more.

[0155] As is clear from the above formulas (1) and (3), the heat shrinkage rate x3 is 2.7% or less. The heat shrinkage rate x3 is preferably 2% or less. The heat shrinkage rate x3 is 0% or more.

[0156] The difference x2-x1 between the thermal shrinkage rate x2 and the thermal shrinkage rate x1 is -1.0% or more as shown in the above formula (2). The difference x2-x1 is preferably -0.8% or more. The difference x2-x1 is preferably 0.3% or less.

[0157] The difference x2-x3 between the thermal shrinkage rate x2 and the thermal shrinkage rate x3 is -0.2% or more as shown in the above formula (2). The difference x2-x3 is preferably 0% or more. The difference x2-x3 is preferably 1.1% or less.

[0158] A package obtained from the laminate 10A in which the heat shrinkage rates x1, x2, and x3 satisfy the above relationship maintains, after retort treatment, high adhesion between the first base material layer 1 and the second base material layer 2, and also maintains high adhesion between the second base material layer 2 and the sealant layer 3. In other words, the package obtained from the laminate 10A exhibits high resistance to retort treatment.

[0159] <2> Second embodiment FIG. 2 is a cross-sectional view schematically showing a part of a laminate according to a second embodiment of the present invention.

[0160] The laminate 10B shown in Fig. 2 is similar to the laminate 10A described with reference to Fig. 1, except for the following configuration: In the laminate 10B, the second base layer 2 includes a polyolefin film 21, an adhesion layer 22, a gas barrier vapor deposition layer 23, and a gas barrier coating layer 24, in this order from the first base layer 1 side. In other words, in the laminate 10B, the stacking order of the polyolefin film 21, the adhesion layer 22, the gas barrier vapor deposition layer 23, and the gas barrier coating layer 24 is reversed from that of the laminate 10A.

[0161] Similar to the package obtained from the laminate 10A, the package obtained from the laminate 10B employing this configuration maintains high adhesion between the first base material layer 1 and the second base material layer 2 after retort treatment, and also maintains high adhesion between the second base material layer 2 and the sealant layer 3. In other words, the package obtained from the laminate 10B exhibits high resistance to retort treatment.

[0162] <3> Third embodiment FIG. 3 is a cross-sectional view schematically showing a part of a laminate according to a third embodiment of the present invention.

[0163] The laminate 10C shown in FIG. 3 is similar to the laminate 10A described with reference to FIG. 1, except that the following configuration is employed.

[0164] That is, in the laminate 10C, the first base layer 1 includes, in this order, a polyolefin film 11, an adhesion layer 12, a gas barrier vapor deposition layer 13, and a gas barrier coating layer 14. The first base layer 1 is bonded to the second base layer 2 via a first adhesive layer 4, with the gas barrier coating layer 14 facing the second base layer 2. The polyolefin film 11 corresponds to the polyolefin film included in the first base layer 1 of the laminate 10A. The adhesion layer 12, the gas barrier vapor deposition layer 13, and the gas barrier coating layer 14 correspond to the adhesion layer 22, the gas barrier vapor deposition layer 23, and the gas barrier coating layer 24, respectively, included in the second base layer 2 of the laminate 10A.

[0165] In the laminate 10C, the first base material layer 1 is made of a polyolefin film. This polyolefin film corresponds to the polyolefin film 21 contained in the second base material layer 2 of the laminate 10A.

[0166] Similar to the package obtained from the laminate 10A, the package obtained from the laminate 10C employing this configuration maintains high adhesion between the first base material layer 1 and the second base material layer 2 after retort treatment, and also maintains high adhesion between the second base material layer 2 and the sealant layer 3. In other words, the package obtained from the laminate 10C exhibits high resistance to retort treatment.

[0167] <4> Packages and packaged articles FIG. 4 is a perspective view schematically showing a package according to one embodiment of the present invention. The package 100 shown in FIG. 4 is a bag. The package 100 is made of a packaging material 10. The packaging material 10 is any one of the laminates 10A, 10B, and 10C described above. The package 100 is manufactured so that the sealant layer 3 faces the inside of the bag. In the package 100, the sealant layers 3 are heat-sealed to each other at their edges. The package 100 can have various structures, such as a side-sealed bag, a three-side-sealed bag, and a stand-up bag.

[0168] A packaged article including this package 100 has contents placed in the package 100 and the opening of the package 100 sealed. The contents are, for example, food or medicine. A packaged article containing food as the contents is, for example, a retort food. A packaged article containing medicine as the contents is, for example, an infusion bag. The opening of the package 100 can be sealed by heat-sealing the sealant layers 3 together at the opening. This packaged article is preferably subjected to heat sterilization treatment such as retort treatment or boiling treatment.

[0169] Retort processing is generally a method of heat sterilizing microorganisms such as mold, yeast, and bacteria to enable long-term storage of foods, pharmaceuticals, etc. In retort processing, a packaged item containing food or the like is typically heat-treated at a temperature of 105 to 140°C for 10 to 120 minutes under pressure of 0.15 to 0.30 MPa. Retort apparatuses are classified into steam types that use heated steam and hot water types that use pressurized heated water, and are used appropriately depending on the sterilization conditions of the food or other contents.

[0170] Boiling is a moist heat sterilization method that enables long-term storage of foods, pharmaceuticals, etc. In boiling, a packaged item containing food or other items is typically heat-treated at atmospheric pressure at a temperature of 60 to 100°C for 10 to 120 minutes, depending on the contents. Boiling is usually carried out in a hot water bath at a temperature of 100°C or less. Boiling treatment devices include a batch type in which the packaged item is immersed in a hot water bath at a constant temperature and treated for a certain period of time before being removed, and a continuous type in which the packaged item is passed through a tunnel-type hot water bath for treatment.

[0171] The packaging body 100 described above is particularly suitable for use in applications where retort treatment is performed at temperatures of 120° C. or higher. Even when retort treatment is performed, the packaging body 100 maintains high adhesion between the first base material layer 1 and the second base material layer 2, and also maintains high adhesion between the second base material layer 2 and the sealant layer 3. In other words, the packaging body 100 exhibits high resistance to retort treatment.

[0172] Although the bag-shaped packaging body 100 is exemplified here, the packaging body obtained using the laminates 10A, 10B, and 10C is not limited to a bag-shaped body. For example, the laminates 10A, 10B, and 10C can be used as a lid material in a packaging body including a cylindrical container body with a bottom and a lid body that closes the opening of the container body. [Example]

[0173] The following describes tests carried out in connection with the present invention.

[0174] <Preparation of biaxially stretched polypropylene film> As the first or second base layer, the following biaxially oriented polypropylene film (OPP) was prepared.

[0175] OPP (heat shrinkage rate 0.6%, thickness 20 μm) OPP (heat shrinkage rate 0.7%, thickness 20 μm) OPP (heat shrinkage rate 0.8%, thickness 20 μm) OPP (heat shrinkage rate 1.0%, thickness 20 μm) OPP (heat shrinkage rate 1.1%, thickness 20 μm) OPP (heat shrinkage rate 1.2%, thickness 20 μm) OPP (heat shrinkage rate 1.3%, thickness 20 μm) OPP (heat shrinkage rate 1.4%, thickness 20 μm) OPP (heat shrinkage rate 1.5%, thickness 20 μm) OPP (heat shrinkage rate 1.7%, thickness 20 μm) OPP (heat shrinkage rate 2.2%, thickness 20 μm) OPP (heat shrinkage rate 3.2%, thickness 20 μm) OPP (heat shrinkage rate 3.3%, thickness 20 μm) OPP (heat shrinkage rate 3.4%, thickness 20 μm) Here, the "thermal shrinkage rate" refers to the thermal shrinkage rate in the running direction after heating at 120° C. for 15 minutes. These thermal shrinkage rates correspond to the above-mentioned thermal shrinkage rates x1 and x2.

[0176] <Preparing gas barrier OPP> In addition, the following gas barrier OPP was prepared as the first or second base layer.

[0177] Gas barrier OPP (heat shrinkage rate 0.4%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 0.5%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 0.6%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 0.7%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.2%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.4%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.4%, thickness 20 μm, SiO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.5%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.7%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 1.8%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 3.3%, thickness 20 μm, AlO x vapor deposition layer) Gas barrier OPP (heat shrinkage rate 3.4%, thickness 20 μm, AlO x vapor deposition layer) Here, the "thermal shrinkage rate" refers to the thermal shrinkage rate in the running direction after heating at 120° C. for 15 minutes. These thermal shrinkage rates correspond to the above-mentioned thermal shrinkage rates x1 and x2.

[0178] Each of the gas barrier OPPs described above is made up of a polypropylene film, an adhesive layer formed thereon, and a gas barrier vapor deposition layer of AlO x Deposition layer or SiO x It consists of a vapor-deposited layer and a gas-barrier coating layer formed thereon. The thickness of the gas-barrier OPP mentioned above is the total thickness of the polypropylene film, adhesive layer, gas-barrier vapor-deposited layer, and gas-barrier coating layer.

[0179] The adhesion layer was formed by applying an anchor coating agent prepared by the following method. First, 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. This mixture was then 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 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 the mixture was mixed to obtain an anchor coating agent. The adhesion layer was formed by applying this anchor coating agent to the surface of a corona-treated polypropylene film by gravure roll coating, and then drying and curing the coating at 60°C. The mass per unit area of ​​the adhesion layer was 0.1 g / m. 2 It was decided.

[0180] The gas barrier deposition layer was formed by electron beam vacuum deposition. x The thickness of the deposited layer was 10 nm. x The thickness of the deposited layer was 30 nm.

[0181] The gas barrier coating layer was formed by applying a coating liquid prepared by the following method to the gas barrier vapor deposition layer.

[0182] First, 72.1 g of 0.1 N hydrochloric acid was added to a mixture of 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol, and the mixture was stirred for 30 minutes to hydrolyze the tetraethoxysilane. This resulted in a hydrolysis solution A with a solid content of 5 mass % (SiO2 equivalent).

[0183] A solution containing 5% by mass of polyvinyl alcohol was also prepared. The solvent for this solution was an aqueous solvent containing water and methanol in a mass ratio of 95:5. This solution will be referred to as Solution B below.

[0184] Furthermore, a solution containing 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate with a solid content of 5% by mass was prepared. The solvent for this solution was an aqueous solvent containing water and isopropyl alcohol in a mass ratio of 1:1. This solution will be referred to as Liquid C below.

[0185] Next, the above-mentioned solutions A, B, and C were mixed in a mass ratio of 65:25:10 to prepare a coating solution.

[0186] This coating liquid was applied to the gas barrier deposition layer by gravure roll coating, and then heated and dried in an oven under conditions of a tension of 20 N / m and a drying temperature of 80°C to form a gas barrier coating layer with a thickness of 0.3 μm.

[0187] This produced a gas barrier OPP having a structure in which a polypropylene film, an adhesive layer, a gas barrier vapor deposition layer, and a gas barrier coating layer were laminated in this order.

[0188] <Preparing the sealant layer> As the sealant layer, the following unstretched polypropylene film (CPP) was prepared.

[0189] CPP (heat shrinkage rate 0.3%, thickness 70 μm) CPP (heat shrinkage rate 0.6%, thickness 70 μm) CPP (heat shrinkage rate 0.7%, thickness 70 μm) CPP (heat shrinkage rate 1.4%, thickness 70 μm) CPP (heat shrinkage rate 1.6%, thickness 70 μm) These heat shrinkage rates correspond to the above-mentioned heat shrinkage rate x3.

[0190] <Measurement of heat shrinkage rate> The heat shrinkage of each film, designated as the first and second substrate layers and the sealant layer, was measured according to the procedures described above for heat shrinkage x1, x2, and x3. The results are shown in Tables 1 and 2 below.

[0191] <Manufacturing of laminate> The laminates 10A, 10B and 10C described with reference to FIGS. 1 to 3 were manufactured by a roll-to-roll process.

[0192] The first and second substrate layers were laminated by dry lamination. The second substrate layer and sealant layer were also laminated by dry lamination. A two-component adhesive was used for these laminations. Mitsui Chemicals A525 was used as the main component of the two-component adhesive, and Mitsui Chemicals A52 was used as the curing agent. The heating temperature for these laminations was 60°C.

[0193] Tables 1 and 2 below show the combinations of films used for the first base layer, second base layer, and sealant layer, as well as the structures employed in the laminates. In Tables 1 and 2, laminates in which the second base layer is a gas-barrier OPP and the barrier surface faces the first base layer have the same structure as laminate 10A described with reference to FIG. 1. A laminate in which the second base layer is a gas-barrier OPP and the barrier surface faces the sealant layer has the same structure as laminate 10B described with reference to FIG. 2. A laminate in which the first base layer is a gas-barrier OPP has the same structure as laminate 10C described with reference to FIG. 3.

[0194] <Manufacturing of packaging items> Two square film pieces, each 15 cm long, were cut from each of the laminates and stacked with their sealant layers facing each other. The film pieces were then impulse sealed on three sides to form a pouch. 100 mL of tap water was placed inside, and the remaining side was impulse sealed. This resulted in a packaged article containing a four-sided sealed pouch and tap water.

[0195] <Adhesion strength evaluation> A 15 mm wide strip of test specimen was cut out from each of the laminates, and the peel strength between the first and second base layers and the peel strength between the second base layer and the sealant layer were measured using a Tensilon universal testing machine RTC-1250 manufactured by Orientec Co., Ltd.

[0196] The above-mentioned packaged articles were subjected to retort treatment in a retort apparatus under a pressure of 0.2 MPa at 121°C for 30 minutes. After that, strip-shaped test pieces with a width of 15 mm were cut out from the laminate of each packaged article, and the peel strength between the first base material layer and the second base material layer and the peel strength between the second base material layer and the sealant layer were measured using the same method as above.

[0197] The peel strength thus obtained was taken as the adhesion strength. The results are shown in Tables 1 and 2 below.

[0198] [Table 1]

[0199] [Table 2]

[0200] In Tables 1 and 2 above, an adhesion force of 2.0 N / 15 mm or more is judged as "A," an adhesion force of more than 1.5 N / 15 mm and less than 2.0 N / 15 mm is judged as "B," and an adhesion force of 1.5 N / 15 mm or less is judged as "C."

[0201] As shown in Table 1, in Examples 1 to 16, the adhesion strength both before and after the retort treatment was rated A. In contrast, in Comparative Examples 1 to 16, the adhesion strength at least either before or after the retort treatment was rated B or C. [Explanation of symbols]

[0202] 1...first base material layer, 2...second base material layer, 3...sealant layer, 4...first adhesive layer, 5...second adhesive layer, 10...packaging material, 10A...laminate, 10B...laminate, 10C...laminate, 11...polyolefin film, 12...adhesion layer, 13...gas barrier vapor deposition layer, 14...gas barrier coating layer, 21...polyolefin film, 22...adhesion layer, 23...gas barrier vapor deposition layer, 24...gas barrier coating layer, 100...packaging.

Claims

1. a first substrate layer, a second substrate layer, and a sealant layer in this order; the first substrate layer, the second substrate layer, and the sealant layer all comprise a polyolefin film; the first base layer or the second base layer further includes a gas barrier vapor deposition layer provided on at least one surface of the polyolefin film, and a gas barrier coating layer coating the gas barrier vapor deposition layer, a heat shrinkage rate x1 in the running direction of the first base material layer after heating at 120°C for 15 minutes, a heat shrinkage rate x2 in the running direction of the second base material layer after heating at 120°C for 15 minutes, and a heat shrinkage rate x3 in the running direction of the sealant layer after heating at 120°C for 15 minutes satisfy the relationships shown in the following formulas (1) to (3), x2≦2.5% … (1) -1.0%≦x2-x1...(2) -0.2%≦x2-x3...(3) The gas barrier coating layer is a laminate that is a cured product of a coating liquid containing one or more selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and hydrolysates thereof.

2. The laminate according to claim 1 , wherein the gas barrier vapor-deposited layer contains aluminum oxide or silicon oxide.

3. The laminate according to claim 1 or 2, wherein the first base material layer further includes a printed layer on a surface facing the second base material layer.

4. The laminate according to claim 1 , wherein the second base layer further comprises an adhesive layer between the polyolefin film and the gas barrier vapor-deposited layer.

5. 5. The laminate according to claim 1, wherein the heat shrinkage rate x2 is 1.5% or less.

6. A packaging material comprising the laminate according to any one of claims 1 to 5.

7. The packaging material according to claim 6, which is for retort packaging.

8. A package comprising the packaging material according to claim 6 or 7.

9. 9. The package according to claim 8, which is in the form of a bag.

10. A packaging body according to claim 8 or 9; The contents contained in the package; A packaging article comprising:

11. The packaged article of claim 10 which has been retorted.

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