JP7771601B2 - Laminate, packaging material, packaging body and packaging article - Google Patents

Description

The present invention relates to a laminate, a packaging material, a package, and a packaged article.

One example of a packaging bag for retort foods is one that has a base layer, an intermediate layer, and a sealant layer bonded together with an adhesive, with the base layer and 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).

Japanese Patent Application Laid-Open No. 2017-178357

In recent years, growing environmental awareness stemming from issues such as marine plastic waste has led to calls for more efficient sorting and recycling of plastic materials. This means that there is now a demand for mono-materialization of packaging laminates, which have traditionally been made by combining a variety of different materials to achieve high performance.

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-based film, there is a risk that the packaging obtained from such a laminate will not be able to withstand retort processing, which is a high-temperature process.

The present invention was made in consideration of the above circumstances, and aims to realize a package in which the film constituting the laminate is made of polyolefin film and which exhibits high resistance to retort treatment.

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).

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 carboxy 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:

Si(OR1) ₃ Z1...(4)
Si(R2)(OR3) ₂ Z2...(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.

Alternatively, according to another aspect of the present invention, there is provided a laminate according to the above aspect, in which 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.

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

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

According to yet another aspect of the present invention, there is provided a packaging material according to the above aspect that is for retort packaging.

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

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

According to yet another aspect of the present invention, there is provided a packaging article comprising a packaging body according to any of the above aspects and contents contained in the packaging body.

According to yet another aspect of the present invention, there is provided a packaging article according to the above aspect that has been retorted.

According to the present invention, the film that constitutes the laminate is made of polyolefin film, making it possible to realize a package that exhibits high resistance to retort treatment.

1 is a cross-sectional view schematically showing a part of a laminate according to a first embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing a part of a laminate according to a second embodiment of the present invention. FIG. 10 is a cross-sectional view schematically showing a part of a laminate according to a third embodiment of the present invention. 1 is a perspective view schematically showing a package according to an embodiment of the present invention;

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below embody one of the above aspects in more detail. Elements having the same or similar functions will be given the same reference numerals, and duplicate descriptions will be omitted.

<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.

The laminate 10A shown in FIG. 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.

Laminate 10A includes a first substrate layer 1, a second substrate layer 2, and a sealant layer 3, in this order. Laminate 10A also 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.

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 comprise polyolefin films. Note that the term "film" refers to a thin layer that can be handled independently from the manufacturing stage and is flexible, or a thin layer formed by extrusion lamination on a component of the laminate, but does not include a thin layer formed by coating, vapor deposition, or the like on a component of the laminate.

The laminate 10A is a film containing only polyolefins, which are the first substrate layer 1, the second substrate 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 described below in order.

<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.

Examples of polyolefin films include polyethylene film (PE), polypropylene film (PP), and polybutene film (PB). The polyolefin film may also 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.

The polyolefin film constituting the first base layer 1 may be a stretched film or a non-stretched film. From the standpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., it is preferable that the polyolefin film be a stretched film. A 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 the packaging material is subjected to retort processing or boiling processing. The stretching method is not particularly limited, and any method that can supply a film with stable dimensions, such as inflation stretching and uniaxial or biaxial stretching, is acceptable.

There are no particular limitations on the thickness of the polyolefin film. Depending on the application, this thickness can be, for example, within the range of 6 to 200 μm. From the perspective of achieving excellent impact resistance and excellent gas barrier properties, a thickness within the range of 9 to 50 μm is preferred, and a thickness within the range of 12 to 38 μm is even more preferred.

The polyolefin film may be subjected to surface modification treatments such as corona treatment, plasma treatment, and flame treatment on the surface facing the second substrate layer 2, and may also be provided with a coating layer such as an easy-adhesion layer.

<1.1.2> Printed 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 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 images. To improve the adhesion of the printed layer, the surface of the base 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.

<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.

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

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

The polyolefin film 21 may have the same crystallinity or molecular chain orientation as the polyolefin film of the first base layer 1, or it may have a different crystallinity or molecular chain orientation. 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.

<1.2.2> Adhesion Layer The adhesion layer 22 is a layer sometimes called an anchor coat layer. Although the adhesion layer 22 can be omitted, providing it on the polyolefin film 21 provides two effects: improved adhesion between the polyolefin film 21 and the gas barrier vapor deposition layer 23, and improved 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 and without defects, making it easier to achieve high barrier properties. The adhesion layer 22 can be formed using an anchor coat agent.

Examples of anchor coating agents include polyester-based polyurethane resins and polyether-based polyurethane resins. From the standpoints of heat resistance and interlayer adhesive strength, polyester-based polyurethane resins are preferred as anchor coating agents. In addition to the above resins, the anchor coating agent may also contain a solvent.

The thickness of the adhesion 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 adhesion layer 22 tends to result in higher interlayer adhesion strength. However, increasing the thickness of the adhesion layer 22 tends to result in a decrease in gas barrier properties.

The anchor coating agent can be applied to the polyolefin film 21 by any known coating method, without any particular limitations. Examples include immersion (dipping) and methods using a spray, coater, printer, or brush. The types of coaters and printers used in these methods and their coating methods include gravure coaters (such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure), reverse roll coaters, microgravure coaters, chamber doctor combined coaters, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters.

The anchor coating agent is preferably applied so that the mass per 1 ^m2 of the coating film after drying is in the range of 0.01 to 5 g/ ^m2 , and more preferably 0.03 to 3 g/ ^m2 . If the amount of anchor coating agent applied is small, discontinuities are likely to occur in the adhesion layer 22. On the other hand, if the amount of anchor coating agent applied is large, the coating film will not dry completely and solvent is likely to remain.

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 selected appropriately depending on the drying method. For example, when 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.

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 containing vinyl alcohol units in which vinyl ester units have been saponified, such as polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

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.

PVA may be a modified PVA that has been copolymerized or post-modified. 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 vinyl ester include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl 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; and nitriles such as acrylonitrile and methacrylonitrile. Examples 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 ether, 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.

The degree of polymerization of the PVA is preferably in the range of 300 to 3,000. A lower degree of polymerization of the PVA tends to reduce barrier properties. A higher degree of polymerization of the PVA tends to increase viscosity and reduce coatability. The degree of saponification of the PVA 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 the PVA may be 100 mol% or less, or may be 99.9 mol% or less. The degree of polymerization and degree of saponification of the PVA can be measured in accordance with the method described in JIS K6726 (1994).

EVOH is generally obtained by saponifying copolymers of ethylene and vinyl acid esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate.

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 higher, more preferably 95 mol% or higher, and even more preferably 99 mol% or higher. The degree of saponification of EVOH may be 100 mol% or lower, or 99.9 mol% or lower. 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 (1H-NMR) measurement.

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.

<1.2.3> Gas Barrier Vapor Deposition Layer The gas barrier vapor deposition 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 deposition layer 23 is a layer formed by vacuum film formation, as described below.

The gas barrier vapor deposition 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 standpoint 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 standpoint of excellent tensile stretchability during processing, the gas barrier vapor deposition layer 23 is preferably a layer made of silicon oxide. The gas barrier vapor deposition layer 23 enables high barrier properties to be obtained while maintaining a thickness within a range that does not affect the recyclability of the laminate 10A.

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.

If the atomic ratio O/Si is too high, the crystallinity of the 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 adequately accommodate this shrinkage and will be less likely to reduce its barrier properties.

The atomic ratio O/Si can be determined by X-ray photoelectron spectroscopy (XPS). For example, a JEOL JPS-90MXV X-ray photoelectron spectrometer is used, 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 atomic ratio O/Si, relative sensitivity factors of 2.28 and 0.9 can be used for O1s and Si2p, respectively.

The thickness of the gas barrier vapor deposition 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 deposition layer 23 is reduced, the water vapor barrier properties will decrease. If the thickness of the gas barrier vapor deposition layer 23 is increased, cracks will easily occur due to deformation caused by internal stress, which will likely result in a decrease in water vapor barrier properties. Furthermore, if the thickness of the gas barrier vapor deposition layer 23 is increased, costs will likely increase due to an increase in the amount of material used and a longer film formation time, making it undesirable from an economic standpoint.

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 evaporation, sputtering, and ion plating. Chemical vapor deposition methods include, but are not limited to, thermal chemical vapor deposition (CVD), plasma CVD, and photo-assisted CVD.

The most preferred vacuum deposition methods are resistance heating vacuum deposition, electron beam (EB) heating vacuum deposition, induction heating vacuum deposition, sputtering, reactive sputtering, dual magnetron sputtering, and plasma enhanced chemical vapor deposition (PECVD). Considering productivity, vacuum deposition is currently the most advantageous. The heating method used in vacuum deposition is preferably one of electron beam heating, resistance heating, or induction heating.

<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 described below.

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 result in higher gas barrier properties. However, increasing the thickness of the gas barrier coating layer 24 reduces the flexibility of the laminate 10A.

(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.

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 hydrolyzate thereof, more preferably contains at least one selected from the group consisting of hydroxyl group-containing polymer compounds, metal alkoxides, and hydrolyzates thereof, and a silane coupling agent or a hydrolyzate thereof, and even more preferably contains a hydroxyl group-containing polymer compound or a hydrolyzate thereof, a metal alkoxide or a hydrolyzate thereof, and a silane coupling agent or a hydrolyzate thereof.

The first coating liquid can be obtained, for example, by mixing a metal alkoxide and a silane coupling agent directly with a solution prepared by dissolving a hydroxyl-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, such as by hydrolysis, with the metal alkoxide and the silane coupling agent.

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.

From the perspective of achieving 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 their hydrolysates:

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

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

Examples of silane coupling agents include compounds represented by the following general formula (II):

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.

Specific examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

The silane coupling agent may be a polymer formed by polymerizing the compound represented by the above general formula (II). As a 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-isocyanatoalkylalkoxysilane.

1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is known to have no chemical reactivity in the isocyanate moiety, but the polarity of the nurate moiety ensures reactivity. 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is generally known as an adhesion improver added to adhesives, etc., similar to 3-isocyanate alkylalkoxysilane. Therefore, adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound can improve the water resistance of the gas barrier coating layer 24 through hydrogen bonding.

In addition, 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 a stable liquid viscosity. Furthermore, the water resistance that can be achieved is equivalent between 3-isocyanate alkyl alkoxysilanes and 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates.

Note that 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is sometimes produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and therefore may be contaminated with the raw material, 3-isocyanatepropylalkoxysilane. There are no particular problems with the presence of such raw materials.

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.

It is also possible to add known additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants to the first coating agent, as long as the gas barrier properties are not impaired.

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 formed 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.

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 this range, the occurrence of cracks in the gas barrier deposition layer 23 and the gas barrier coating layer 24 can be further suppressed, and particularly excellent barrier properties can be achieved.

(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.

Silane compounds include silane coupling agents, polysilazanes, and siloxanes. Specific examples of silane compounds include tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and hexamethyldisilazane.

(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:

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

[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 the carboxyl group-containing polymer include a homopolymer of a carboxyl group-containing unsaturated monomer, a copolymer of two or more types of carboxyl group-containing unsaturated monomers, a copolymer of a carboxyl group-containing unsaturated monomer and another polymerizable monomer, and a polysaccharide containing a carboxyl group in its molecule (also called a "carboxyl group-containing polysaccharide" or "acidic polysaccharide").

Carboxy groups include not only free carboxy groups but also acid anhydride groups (specifically, dicarboxylic acid anhydride groups). The acid anhydride groups may be partially ring-opened to form carboxy groups. Some of the carboxy groups may be neutralized with an alkali. In this case, the degree of neutralization is preferably 20% or less.

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

Graft polymers obtained by graft polymerizing a carboxyl-containing unsaturated monomer onto a polymer that does not contain a carboxyl group, such as a polyolefin, can also be used as carboxyl-containing polymers. Polymers containing hydrolyzable ester groups, such as alkoxycarbonyl groups (e.g., methoxycarbonyl groups), can also be used, converted to carboxyl groups by hydrolysis.

The carboxyl group-containing unsaturated monomer is preferably an α,β-monoethylenically unsaturated carboxylic acid. Therefore, carboxyl group-containing polymers include homopolymers of α,β-monoethylenically unsaturated carboxylic acids, copolymers of two or more α,β-monoethylenically unsaturated carboxylic acids, and copolymers of α,β-monoethylenically unsaturated carboxylic acids with other polymerizable monomers. Ethylenically unsaturated monomers are typical examples of other polymerizable monomers.

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 acid 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.

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.

Examples of carboxyl group-containing polysaccharides include acidic polysaccharides that have carboxyl groups in the molecule, such as alginic acid, carboxymethyl cellulose, 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.

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 properties, hot water resistance, and water vapor resistance of the resulting film, the proportion of the number of moles of 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.

The carboxyl group-containing polymer is preferably a homopolymer or copolymer obtained by polymerization of only α,β-monoethylenically unsaturated carboxylic acid, as this facilitates the production of a film that has excellent gas barrier properties, moisture resistance, water resistance, hot water resistance, and water vapor resistance, and 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.

Particularly preferred carboxyl group-containing polymers are polyacrylic acid, polymethacrylic acid, polymaleic acid, and mixtures of two or more of these. Alginic acid is preferred as an acidic polysaccharide. Among these, polyacrylic acid is particularly preferred because it is relatively easy to obtain and can easily produce a film with excellent physical properties.

There are no particular restrictions on the number average molecular weight of the carboxy group-containing polymer, but from the standpoint 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.

Here, "number average molecular weight" refers to 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.

[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.

Specific examples of polyvalent metals include, but are not limited to, metals from 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.

The polyvalent metal is preferably a divalent metal. It is also preferable that the polyvalent metal forms a compound.

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.

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.

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.

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.

If the average particle size of the polyvalent metal-containing particles in the third coating liquid is too large, the resulting coating layer is likely 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.

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)).

The polyvalent metal-containing particles in the third coating liquid exist as primary particles, secondary particles, or a mixture of these, but in most cases, judging from their average particle size, they are presumed to exist as secondary particles.

[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 having 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.

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

Cationic surfactants include, for example, alkylamine salt types and quaternary ammonium salt types. Examples of alkylamine salt type cationic surfactants include monoalkylamine salts, dialkylamine salts, and trialkylamine salts. Examples of quaternary ammonium salt type cationic surfactants include alkyltrimethylammonium halide (chloride, bromide, or iodide) salts and alkylbenzalkonium chloride.

Examples of amphoteric surfactants include carboxybetaine type, 2-alkylimidazoline derivative type, glycine type, and amine oxide type. Examples of carboxybetaine type amphoteric surfactants include alkyl betaine 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.

Nonionic surfactants include, for example, ester, ether, ester ether, and alkanolamide types. Examples of ester-type nonionic surfactants include glycerin fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters. Examples of ether-type nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polyoxypropylene glycols. Examples of ester-ether-type nonionic surfactants include fatty acid polyethylene glycols and fatty acid polyoxyethylene sorbitan. Examples of alkanolamide-type nonionic surfactants include fatty acid alkanolamides.

Surfactants with polymer backbones, such as styrene-acrylic acid copolymers, can also be used.

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

[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 (a heteroatom or an atomic group having a heteroatom) may be used in combination with the polar organic solvent.

Preferably usable organic solvents 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.

In addition to the polar organic solvents listed 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 also be used as appropriate. Hydrocarbons without polar groups, such as benzene, are generally used in combination with polar organic solvents.

The third coating liquid may contain only an organic solvent as a solvent or dispersion medium, or may further contain water. The inclusion of water improves the solubility of the carboxy group-containing polymer and improves the coatability and workability of the third coating liquid. The water content of the third coating liquid may be, in mass fraction, 100 ppm or more, 1,000 ppm or more, 1,500 ppm or more, or 2,000 ppm or more.

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, by mass fraction.

[Silicon-containing compound (E)]
The third coating liquid contains a silicon-containing compound to enhance peel strength, and the silicon-containing compound 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) ₃ Z1...(4)
Si(R2)(OR3) ₂ Z2...(5)
Here, the mass of the silicon-containing compound (E) is the mass calculated as the silane coupling agent. In addition, 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.

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) typically exists 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.

R1 and R3 may each be an alkyl group having 1 to 6 carbon atoms, preferably a methyl group or an ethyl group. Z1 and Z2 may each be a group containing an epoxy group.

Specific examples of silane coupling agents 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. One or more types of silane coupling agents may be used.

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

The condensates contained in the third coating liquid as at least a portion of the silicon-containing compound (E) are two or more of: 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. Next, these hydrolysis products are condensed to form compounds in which silicon atoms (Si) are bonded via oxygen. This condensation is repeated to obtain the hydrolysis condensate.

〔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.

The ratio (hereinafter also referred to as equivalent ratio) of the product (Bt) of the number of moles of the polyvalent metal contained in the polyvalent metal-containing particles (B) and the valence to the number of moles (At) of carboxy groups contained in the carboxy group-containing polymer (A) is preferably 0.6 or greater. This ratio is more preferably 0.8 or greater, and particularly preferably 1.0 or greater. The upper limit of this ratio is usually 10.0, preferably 2.0. If this ratio is made 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.

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

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.

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 should be one that dissolves the carboxyl group-containing polymer but does not substantially dissolve the polyvalent metal compound, allowing it to be dispersed in particle form.

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 typically within the range of 0.0001 to 70% by weight, preferably 0.001 to 60% by weight, and more preferably 0.1 to 50% by weight.

If a surfactant is not added, it becomes difficult to disperse the polyvalent metal-containing particles in the third coating liquid so that their average particle size is sufficiently small. As a result, it becomes difficult to obtain a coating liquid in which the polyvalent metal-containing particles are uniformly dispersed, and it becomes difficult to form a coating film with a uniform thickness when applied to a substrate.

The mass ratio of the silicon-containing compound to the carboxyl group-containing polymer (where the mass of the silicon-containing compound is the mass converted into that 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.

If the amount of silicon-containing compound added is too small, the peel strength of the laminate 10A will be low. As a result, careful handling will be required to prevent delamination, leading to reduced productivity.

The above 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.

Silicon-containing compounds do not have gas barrier properties. Therefore, if too much silicon-containing compound is added, the gas barrier properties of the laminate 10A will be reduced.

[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.

On the other hand, a dispersion is prepared by mixing polyvalent metal-containing particles (B), surfactant (C), and organic solvent (D) and, if necessary, performing a dispersion treatment. 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 solution 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 breaks down the aggregation of the polyvalent metal-containing particles (B), stabilizing the third coating liquid and increasing 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.

Dispersion methods include those using a high-speed stirrer, homogenizer, ball mill, or bead mill. Dispersion using a ball mill or bead mill in particular allows for highly efficient dispersion, making it possible to obtain a stable third coating liquid in a relatively short time. In this case, the diameter of the balls or beads should be small, preferably between 0.1 and 1 mm.

The third coating liquid can be prepared by mixing the carboxyl group-containing polymer solution prepared as described above with a 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 when the dispersion of polyvalent metal-containing particles is mixed with the carboxyl group-containing polymer solution.

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

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.

<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.

The sealant layer 3 is made of a thermoplastic resin, 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 during retort and boiling treatments.

From the perspective 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 film contained in the first base layer 1 and the second base layer 2. That is, if the polyolefin film contained in the first base layer 1 and the second base 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, if the polyolefin film contained in the first base layer 1 and the second base layer 2 is a polypropylene film, it is preferable that the polyolefin film contained in the sealant layer 3 is also a polypropylene film.

The polyolefin film contained in the sealant layer 3 may contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

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 it is preferably within the range of approximately 30 to 150 μm.

<1.4> Adhesive Layer The first adhesive layer 4 bonds the first substrate layer 1 and the second substrate 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 substrate layer 1 and the second substrate 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.

The second adhesive layer 5 bonds the second substrate layer 2 and the sealant layer 3 to each other. The second adhesive layer 5 is made of a second adhesive. The second substrate 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 substrate 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.

Of the above methods, the dry lamination method is particularly advantageous in achieving high resistance to retort treatment, especially 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 temperatures of 85°C or less.

When bonding the first substrate layer 1 and the second substrate layer 2 and when bonding the second substrate layer 2 and the sealant layer 3, heating is preferably performed at a temperature of 85°C or less, and more preferably at a temperature of 70°C or less. If high-temperature heat treatment is performed during the production of the laminate 10A, cracks and peeling from the substrate may occur in the gas barrier vapor deposition layer 23 and the gas barrier coating layer 24, resulting in a decrease in barrier performance.

When bonding the first substrate layer 1 and the second substrate layer 2 and when bonding the second substrate layer 2 and the sealant layer 3, heating is preferably carried out at a temperature of 50°C or higher, and more preferably at a temperature of 60°C or higher. Lowering the temperature reduces productivity.

The sealant layer 3 may also be formed 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 latter. In this case, the second adhesive layer 5 can be omitted.

<1.5> Heat Shrinkage Rate In the laminate 10A described above, 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 thermal 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 thermal shrinkage rates x1, x2, and x3 is measured by the following procedure.

First, a square measurement sample 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.

As is clear from the above formulas (1) and (2), the thermal shrinkage rate x1 is 3.5% or less. It is preferable that the thermal shrinkage rate x1 is 2% or less. The thermal shrinkage rate x1 is 0% or more.

The heat shrinkage rate x2 is 2.5% or less, as shown in the above formula (1). It is preferable that the heat shrinkage rate x2 is 2% or less. The heat shrinkage rate x2 is 0% or more, and preferably 0.4% or more.

As is clear from the above formulas (1) and (3), the heat shrinkage rate x3 is 2.7% or less. It is preferable that the heat shrinkage rate x3 is 2% or less. The heat shrinkage rate x3 is 0% or more.

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.

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.

A package obtained from laminate 10A, in which the thermal shrinkage rates x1, x2, and x3 satisfy the above relationship, 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, a package obtained from laminate 10A exhibits high resistance to retort treatment.

<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.

The laminate 10B shown in Figure 2 is similar to the laminate 10A described with reference to Figure 1, except for the following configuration. That is, in laminate 10B, the second substrate 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 substrate layer 1 side. In other words, in 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 laminate 10A.

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

<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.

The laminate 10C shown in Figure 3 is similar to the laminate 10A described with reference to Figure 1, except for the following configuration.

That is, in laminate 10C, the first substrate 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 substrate layer 1 is adhered to the second substrate layer 2 via a first adhesive layer 4, with the gas barrier coating layer 14 facing the second substrate layer 2. The polyolefin film 11 corresponds to the polyolefin film included in the first substrate layer 1 of 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 substrate layer 2 of laminate 10A.

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

Like the package obtained from laminate 10A, the package obtained from laminate 10C employing this configuration maintains high adhesion between the first base material layer 1 and the second base material layer 2 after retort processing, as well as high adhesion between the second base material layer 2 and the sealant layer 3. In other words, the package obtained from laminate 10C exhibits high resistance to retort processing.

<4> Package and Packaged Article FIG. 4 is a perspective view schematically showing a package according to one embodiment of the present invention.
The package 100 shown in Figure 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.

A packaged article containing this package 100 has contents placed in the package 100 and the opening of the package 100 sealed. The contents may be, for example, food or medicine. A packaged article containing food as the contents is, for example, a retort pouch 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 a heat sterilization process such as a retort process or a boiling process.

Retort processing is a method of heat sterilizing microorganisms such as mold, yeast, and bacteria, generally to enable long-term storage of foods, pharmaceuticals, etc. In retort processing, a packaged item containing food or other items 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 equipment comes in two types: a steam type that uses heated steam, and a hot water type that uses pressurized heated water. The appropriate type is used depending on the sterilization conditions of the food or other items contained within.

Boiling is a moist heat sterilization method that enables long-term storage of foods, pharmaceuticals, etc. In boiling, packaged items containing food or other items are 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. There are two types of boiling treatment equipment: a batch type in which packaged items are 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 packaged items are passed through a tunnel-type hot water bath for treatment.

The above-described packaging body 100 is particularly suitable for use in applications requiring retort treatment 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, as well as 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.

Note that while a bag-shaped packaging body 100 has been exemplified here, packaging bodies obtained using laminates 10A, 10B, and 10C are not limited to bag shapes. For example, laminates 10A, 10B, and 10C can be used as a lid material in a packaging body that includes a cylindrical container body with a bottom and a lid body that closes the opening of the container body.

The following describes tests conducted in connection with the present invention.

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

- 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.

<Preparation of gas barrier OPP>
Furthermore, the following gas barrier OPP was prepared as the first or second base layer.

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.

Each of the gas barrier OPPs comprises a polypropylene film, an adhesive layer formed thereon, an _AlOx vapor-deposited layer or _SiOx vapor-deposited layer as a gas barrier vapor-deposited layer formed thereon, and a gas barrier coating layer formed thereon. Note that 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.

The adhesion layer was formed by applying an anchor coating agent prepared by the following method. Specifically, acrylic polyol and tolylene diisocyanate were first 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 resulting 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, followed by drying and curing the coating at 60°C. The mass per unit area of the adhesion layer was 0.1 g/ ^m² .

The gas barrier vapor deposition layers were formed by electron beam vacuum deposition. The AlO _x vapor deposition layer had a thickness of 10 nm, and the SiO _x vapor deposition layer had a thickness of 30 nm.

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

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 produced a hydrolysis solution A with a solid content of 5 mass % ( _SiO2 equivalent).

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

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

Next, the above liquids A, B, and C were mixed in a mass ratio of 65:25:10 to prepare a coating liquid.

This coating liquid was applied to the gas barrier vapor deposition layer using the gravure roll coating method, and then heated and dried in an oven at a tension of 20 N/m and a drying temperature of 80°C to form a gas barrier coating layer 0.3 μm thick.

This resulted in 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.

<Preparation of sealant layer>
As the sealant layer, the following unstretched polypropylene film (CPP) was prepared.

-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.

<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.

<Production of Laminate>
The laminates 10A, 10B and 10C described with reference to FIGS. 1 to 3 were manufactured by a roll-to-roll process.

The first and second substrate layers were laminated using the dry lamination method. The second substrate layer and sealant layer were also laminated using the dry lamination method. 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.

Tables 1 and 2 below show the combinations of films used for the first substrate layer, second substrate layer, and sealant layer, as well as the structures employed in the laminates. In Tables 1 and 2, the laminate in an example in which the second substrate layer is a gas barrier OPP and the barrier surface faces the first substrate layer has the same structure as laminate 10A described with reference to Figure 1. The laminate in an example in which the second substrate 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 Figure 2. The laminate in an example in which the first substrate layer is a gas barrier OPP has the same structure as laminate 10C described with reference to Figure 3.

<Production of packaging articles>
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.

<Evaluation of Adhesion Strength>
A test piece having a width of 15 mm was cut out from each of the laminates, and the peel strength between the first base layer and the second base layer 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.

The above-mentioned packaged articles were also subjected to retort treatment in a retort apparatus at 121°C for 30 minutes under a pressure of 0.2 MPa. Afterwards, strip-shaped test pieces measuring 15 mm in width 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.

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

In Tables 1 and 2 above, an adhesion force of 2.0 N/15 mm or greater is rated as "A," an adhesion force of greater than 1.5 N/15 mm but less than 2.0 N/15 mm is rated as "B," and an adhesion force of 1.5 N/15 mm or less is rated as "C."

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

1...First substrate layer, 2...Second substrate 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 (10)

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 satisfying the relationships shown in the following formulas (1) to (3).
x2≦2.5% … (1)
-0.1% ≦x2-x1 ≦0.3% ...(2)
0% ≦x2-x3 ≦1.1% …(3) 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 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), a hydrolyzate thereof, and a condensate thereof:
Si(OR1) ₃ Z1...(4)
Si(R2)(OR3) ₂ Z2...(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.) The laminate according to claim 1, wherein the gas barrier coating layer is a cured product of a coating liquid containing one or more selected from the group consisting of hydroxyl group-containing polymeric compounds, metal alkoxides, silane coupling agents, and hydrolysates thereof. The laminate described in any one of claims 1 to 3, wherein the gas barrier vapor deposition layer contains aluminum oxide or silicon oxide. A packaging material comprising the laminate described in any one of claims 1 to 4. The packaging material according to claim 5, which is for retort packaging. A package containing the packaging material described in claim 5 or 6. The packaging body according to claim 7 is bag-shaped. A packaging body according to claim 7 or 8;
and a packaged article having contents contained in the package. The packaging article of claim 9, which has been retorted.