Laminate and packaging product using same

Abstract

[Problem] To provide a multilayer body capable of suppressing deterioration of barrier properties even after heat sterilization treatment. [Solution] A heat-sterilized multilayer body for use in a packaging bag containing a retorted food or a boiled food. The multilayer body includes: a barrier film in which a biaxially stretched polypropylene substrate, an inorganic oxide vapor deposition film, and a coating layer having barrier properties are laminated in this order; and a sealant layer. In the coating layer of the multilayer body, a composite elastic modulus and an indentation hardness measured by a nanoindentation method from a cross section of the coating layer are respectively from 5.0 GPa to 9.5 GPa and from 0.9 GPa to 1.7 GPa.

Description

[Technical Field]

[0001] The present invention relates to a laminate and a packaging product using the same. [Background technology]

[0002] In recent years, from the viewpoint of environmental consideration, mono-material packaging materials have been investigated with the aim of improving the recyclability of packaging materials. For example, laminates in which a polyolefin film such as biaxially oriented polypropylene film (OPP film) is used as the base material instead of the conventionally widely used polyester film (PET film), and a polyolefin film such as unoriented polypropylene film (CPP film) is used as the sealant layer to be laminated to this, are being investigated as mono-material packaging materials.

[0003] For example, Patent Document 1 below discloses a gas barrier laminate comprising a substrate layer containing a polyolefin resin, a barrier layer, and an overcoat layer containing a polyvinyl alcohol resin, wherein the surface hardness of the overcoat layer is 1.5 GPa or less as measured by nanoindentation. This laminate, comprising a biaxially oriented polypropylene substrate, a barrier film in which an inorganic oxide vapor-deposited film and a coating layer having barrier properties are laminated in this order, and a sealant layer, is known as a polyolefin-based monomaterial packaging material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2022 / 085586 International Publication Summary of the Invention [Problem to be solved by the invention]

[0005] When a laminate made of polyolefin mono-material packaging material is subjected to retort sterilization or boiling, OPP film has inferior heat resistance and strength compared to PET film, and as a result, the barrier properties of OPP film after heat sterilization are significantly reduced compared to PET film.

[0006] Patent Document 1 specifies the composite elastic modulus and hardness of the coating layer, but focuses on the "suitability for processing" of the barrier film. For this reason, Patent Document 1 only specifies the composite elastic modulus and hardness of the coating layer "before heat sterilization treatment," and makes no mention of heat sterilization treatment or the barrier properties thereafter.

[0007] According to the investigations of the present inventors, it has been found that the composite elastic modulus and hardness of the coating layer vary before and after lamination and depending on whether or not heat sterilization has been performed. Therefore, even if the composite elastic modulus and hardness of the coating layer "before heat sterilization" are specified as in Patent Document 1, it is not possible to predict the barrier properties of the laminate when it is heat sterilized. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the present inventors have discovered a range of composite elastic modulus and indentation hardness suitable for heat sterilization treatment applications such as retort treatment for a coating layer constituting a laminate, which is a polyolefin-based monomaterial packaging material, and have discovered a packaging material that can suppress a decrease in barrier property even after "heat sterilization treatment of the laminate," thereby completing the present invention. Specifically, the present invention provides the following.

[0009] (1) A heat-sterilized laminate used for packaging bags containing retort food or boiled food, The laminate comprises a biaxially oriented polypropylene substrate, a barrier film in which an inorganic oxide vapor-deposited film and a coating layer having barrier properties are laminated in this order, and a sealant layer; A laminate in which the coating layer of the laminate has a composite elastic modulus and an indentation hardness measured by a nanoindentation method from a cross section of the coating layer, the composite elastic modulus being 5.0 GPa or more and 9.5 GPa or less, and the indentation hardness being 0.9 GPa or more and 1.7 GPa or less.

[0010] (2) The laminate according to claim 1, wherein the composite elastic modulus is 6.0 GPa or more and 9.0 GPa or less, and the indentation hardness is 1.0 GPa or more and 1.5 GPa or less.

[0011] (3) The laminate according to claim 1 or 2, wherein the heat sterilization treatment is a retort treatment.

[0012] (4) The laminate according to claim 1 or 2, wherein the coating layer comprises a cured product of a resin composition containing an alkoxysilane and a hydroxyl group-containing water-soluble resin.

[0013] (5) The laminate according to claim 1 or 2, wherein the surface of the coating layer of the barrier film is laminated to another film via an adhesive layer.

[0014] (6) The packaging material after heat sterilization according to claim 1 or 2 has an oxygen permeability of 10.0 cc / m at 23°C and 90% RH according to JIS K 7126-2. 2 ·day·atm or less, laminate.

[0015] (7) The packaging material after heat sterilization according to claim 1 or 2 has an oxygen permeability of 5.0 cc / m at 23°C and 90% RH according to JIS K 7126-2. 2 ·day·atm or less, laminate.

[0016] (8) A packaging product comprising the laminate according to claim 1 or 2.

[0017] (9) Use of a heat-sterilized laminate for packaging retort or boiled foods, The laminate comprises a biaxially oriented polypropylene substrate, a barrier film in which an inorganic oxide vapor-deposited film and a coating layer having barrier properties are laminated in this order, and a sealant layer; The coating layer of the laminate has a composite elastic modulus and indentation hardness measured by nanoindentation from a cross section of the coating layer, the composite elastic modulus being 5.0 GPa or more and 9.5 GPa or less, and the indentation hardness being 0.9 GPa or more and 1.7 GPa or less. [Effects of the Invention]

[0018] The laminate of the present invention has excellent barrier properties even after heat sterilization treatment. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a cross-sectional view showing an example of a layer structure of the laminate according to the present embodiment. [Figure 2] FIG. 4 is a cross-sectional view showing another example of the layer structure of the laminate according to the present embodiment. [Figure 3] FIG. 1 is a graph showing the composite elastic modulus and indentation hardness after retort treatment at 121° C. for 30 minutes in an example. [Figure 4] FIG. 1 is a graph showing the composite elastic modulus and indentation hardness after high retort treatment at 135° C. for 30 minutes in an example. DETAILED DESCRIPTION OF THE INVENTION

[0020] Specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be practiced with appropriate modifications within the scope of the object of the present invention. Furthermore, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "at least X and at most Y."

[0021] In this specification, "laminated in this order" means that the biaxially oriented polypropylene substrate, the inorganic oxide vapor deposition film, and the coating layer having barrier properties are laminated in this order, and other layers such as an anchor coat layer or a primer layer may be laminated between these layers.

[0022] Fig. 1 is a cross-sectional view showing an example of a barrier film according to the present embodiment. The laminate 100 in Fig. 1 comprises a first biaxially oriented polypropylene substrate 10, an inorganic oxide vapor-deposited film 20, and a coating layer 30 having barrier properties, constituting a barrier film. The inorganic oxide vapor-deposited film 20 and the coating layer 30 constitute a barrier layer. The surface of the barrier film facing the first biaxially oriented polypropylene substrate 10 is laminated to a sealant layer 50 via a first adhesive layer 61, and the surface of the barrier film facing the coating layer 30 is laminated to a second biaxially oriented polypropylene substrate 40 via an adhesive layer 62. This means that the laminate has a three-layer structure of second biaxially oriented polypropylene substrate 40 / second adhesive layer 62 / barrier film / first adhesive layer 61 / sealant layer 50, with the barrier film serving as an intermediate layer.

[0023] Each layer constituting the laminate will now be described.

[0024] [First biaxially oriented polypropylene base material] The first biaxially oriented polypropylene substrate 10 is a polypropylene substrate that has been subjected to a stretching treatment. Hereinafter, except when referring to the stretching treatment, when simply referring to a "polypropylene substrate," it means a polypropylene substrate that has been subjected to a stretching treatment.

[0025] The biaxially oriented polypropylene substrate is composed of at least polypropylene, which may be any of a propylene homopolymer, a propylene random copolymer, and a propylene block copolymer, or a mixture of two or more selected from these.

[0026] A propylene homopolymer is a polymer of propylene only. A propylene random copolymer is a random copolymer of propylene and an α-olefin other than propylene. A propylene block copolymer is a copolymer having a polymer block of propylene and a polymer block of at least an α-olefin other than propylene. The latter polymer block may be a polymer block of propylene and an α-olefin other than propylene.

[0027] Examples of α-olefins include α-olefins having 2 or more and 20 or less carbon atoms, and specific examples include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene.

[0028] Among polypropylenes, it is preferable to use a random copolymer from the viewpoint of transparency. When the rigidity and heat resistance of the laminate are important, it is preferable to use a homopolymer. When the impact resistance of the laminate is important, it is preferable to use a block copolymer.

[0029] In one embodiment, the melt flow rate (MFR) of the polypropylene may be 0.1 g / 10 min or more and 50 g / 10 min or less, or 0.3 g / 10 min or more and 30 g / 10 min or less, from the viewpoint of film-forming ability and processability. The MFR of the polypropylene is measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2.16 kg.

[0030] As the polypropylene, biomass-derived polypropylene or mechanically recycled or chemically recycled polypropylene may be used.

[0031] The polypropylene content in the polypropylene base material is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0032] The polypropylene base material may contain a resin material other than polypropylene, such as polyolefins such as polyethylene, (meth)acrylic resins, vinyl resins, cellulose resins, polyamides, polyesters, and ionomer resins.

[0033] The polypropylene substrate may contain additives such as crosslinkers, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, lubricants, antistatic agents, pigments, and modifying resins.

[0034] The first biaxially oriented polypropylene substrate is a substrate that has been subjected to a biaxial stretching treatment. This can improve, for example, the heat resistance, impact resistance, water resistance, and dimensional stability of the barrier substrate. A laminate including such a barrier substrate is suitable, for example, as a packaging material that is subjected to a boiling treatment or a retort treatment.

[0035] When stretching in the machine direction (machine direction, MD, of the substrate), the stretching ratio is preferably 2 to 15, more preferably 5 to 13. When stretching in the transverse direction (direction perpendicular to the MD, TD, of the substrate), the stretching ratio is preferably 2 to 15, more preferably 5 to 13. By setting the stretching ratio to 2 or more, the strength and heat resistance of the polypropylene substrate can be further improved, and when the first biaxially oriented polypropylene substrate is used as the outermost layer, the printability of the polypropylene substrate can be improved. From the viewpoint of the breaking limit of the polypropylene substrate, the stretching ratio is preferably 15 or less.

[0036] The first biaxially oriented polypropylene substrate may include a first layer and a second layer. The first layer is the layer on one side of the biaxially oriented polypropylene substrate (the side on which a barrier layer such as a vapor-deposited film is formed), and the second layer is the layer on the other side of the biaxially oriented polypropylene substrate. The first layer and the second layer may each be a propylene random copolymer, which is a random copolymer of propylene and an α-olefin other than propylene. When the first layer and the second layer are random copolymers, the adhesion between the layer and other layers in contact with them can be improved.

[0037] The first biaxially oriented polypropylene substrate may have an intermediate layer between the first layer and the second layer. The intermediate layer is made of polypropylene, such as polypropylene containing propylene homopolymer. The intermediate layer may have a single-layer structure or a multi-layer structure.

[0038] The thickness of the first biaxially oriented polypropylene substrate is preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 15 μm or more and 25 μm or less. When the thickness is equal to or more than the lower limit, for example, the strength and heat resistance of the barrier substrate can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the barrier substrate can be further improved.

[0039] The first biaxially stretched polypropylene substrate may be a coextrusion stretched film. It can be produced by forming a laminated film using a conventionally known T-die method or inflation method, and then stretching the laminated film. When forming the film using the inflation method, the laminated film may be stretched at the same time.

[0040] The first biaxially oriented polypropylene substrate may be surface-treated. This can improve, for example, the adhesion between the polypropylene substrate and other layers. Examples of surface treatment methods include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using one or more gases selected from oxygen gas, argon gas, nitrogen gas, etc., and glow discharge treatment; and chemical treatments such as oxidation treatment using chemicals. In addition, an easy-adhesion layer may be provided on the surface of the first biaxially oriented polypropylene substrate.

[0041] When the first biaxially oriented polypropylene substrate is used as the outermost layer of the laminate, a printed layer may be provided on the second layer. The image formed on the printed layer is not particularly limited, and examples include letters, patterns, symbols, and combinations thereof. The printed layer may also be formed using ink derived from biomass, which further reduces the environmental impact.

[0042] Examples of methods for forming the printed layer include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing. Among these, flexographic printing is preferred from the viewpoint of reducing environmental impact.

[0043] The first biaxially oriented polypropylene substrate may have an anchor coat layer between it and the inorganic oxide vapor-deposited film. This increases the adhesive strength between the polypropylene substrate and the inorganic oxide vapor-deposited film, and also results in an inorganic oxide vapor-deposited film consisting of a dense, continuous layer with few gaps and excellent flexibility. Furthermore, by providing an anchor coat layer on the first layer of the polypropylene substrate, the surface of the substrate can be made smoother. This results in high gas barrier properties and can prevent breakage of the inorganic oxide vapor-deposited film and coating layer due to deformation or bending of the film, as well as the resulting deterioration of gas barrier properties. By providing an anchor coat layer, a barrier substrate with excellent heat resistance and oil resistance that can withstand boiling and retort sterilization can be obtained.

[0044] Examples of the anchor coat layer include polyurethane resins, polyamide resins, epoxy resins, phenol resins, (meth)acrylic resins, and polyvinyl acetate resins. Examples of the polyurethane resin include acrylic urethane resins and polyester urethane resins.

[0045] The first biaxially oriented polypropylene substrate may have a surface resin layer on its surface instead of the anchor coat layer.

[0046] Specifically, the barrier film may be formed by laminating, in this order, a biaxially oriented polypropylene substrate, a surface resin layer, an inorganic oxide vapor deposition film, and a coating layer having barrier properties. Alternatively, the barrier film may be formed by laminating, in this order, a biaxially oriented polypropylene substrate, an adhesive resin layer, a surface resin layer, an inorganic oxide vapor deposition film, and a coating layer having barrier properties.

[0047] (Surface resin layer) The surface resin layer contains a resin material having a melting point of 180°C or higher (hereinafter also referred to as a high-melting-point resin material). This allows a vapor-deposited film with high adhesion to be formed on the surface resin layer, improving gas barrier properties. Furthermore, packaging products produced using a laminate including the surface resin layer have high lamination strength. The surface resin layer may be provided on a biaxially oriented polypropylene substrate. That is, the surface resin layer may be adjacent to the biaxially oriented polypropylene substrate. When an adhesive resin layer is provided between the biaxially oriented polypropylene substrate and the surface resin layer, the adhesive resin layer may be provided on the biaxially oriented polypropylene substrate, and the surface resin layer may be provided on the adhesive resin layer. That is, the adhesive resin layer may be adjacent to the biaxially oriented polypropylene substrate, and the surface resin layer may be adjacent to the adhesive resin layer.

[0048] The melting point of the high-melting-point resin material is more preferably 185°C or higher, even more preferably 190°C or higher, and particularly preferably 205°C or higher. By setting the melting point of the high-melting-point resin material to 185°C or higher, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. Furthermore, the laminate strength of the packaged product can be further improved. From the viewpoint of the film-forming properties of the biaxially oriented polypropylene substrate, the melting point of the high-melting-point resin material is preferably 265°C or lower, more preferably 260°C or lower, and even more preferably 250°C or lower. In this specification, the melting point can be measured in accordance with JIS K7121:2012 (Method for measuring transition temperatures of plastics). Specifically, the melting point can be determined by measuring a DSC curve at a heating rate of 10°C / min using a differential scanning calorimetry (DSC) device.

[0049] The high-melting-point resin material contained in the surface resin layer has a melting point TA, and the polypropylene contained in the polypropylene resin layer has a melting point TB, with the difference between the melting points TA and TB preferably being 20°C or more. The difference between the melting points TA and TB is preferably 80°C or less, and more preferably 60°C or less. When the difference between the melting points TA and TB is 20°C or more, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaged product can be further improved. Furthermore, when the difference between the melting points TA and TB is 80°C or less, the film-forming properties of the biaxially oriented polypropylene substrate can be further improved.

[0050] The high-melting-point resin material preferably has a polar group. In the present invention, the polar group refers to a group containing one or more heteroatoms. Examples of polar groups include ester groups, epoxy groups, hydroxyl groups, amino groups, amide groups, carboxyl groups, carbonyl groups, carboxylic anhydride groups, sulfone groups, thiol groups, and halogen groups. Among these, from the viewpoint of the laminate strength of the packaged product, hydroxyl groups, ester groups, amino groups, amide groups, carboxyl groups, and carbonyl groups are preferred, and amide groups are more preferred.

[0051] The high-melting-point resin material is not particularly limited as long as it has a melting point of 180° C. or higher. Examples of high-melting-point resin materials include vinyl resins, polyamides, polyimides, polyesters, (meth)acrylic resins, cellulose resins, polyolefins, and ionomer resins.

[0052] The high-melting-point resin material is preferably a resin material having a melting point of 180°C or higher and containing a polar group, and is preferably a polyester or a polyamide such as nylon 6, nylon 6,6, nylon MXD6, or nylon MXD6I (a copolymer of metaxylylenediamine, adipic acid, and isophthalic acid). Amorphous nylon may be used for the surface resin layer to improve film formability. The resin material used for the surface resin layer may be a blend of two or more high-melting-point resin materials or amorphous nylons. The use of such a resin material significantly improves the adhesion of the vapor-deposited film formed on the surface resin layer, effectively improving its gas barrier properties.

[0053] In one embodiment, the high-melting-point resin material is preferably polyamide. By using polyamide as the high-melting-point resin material, it is possible to suppress the deterioration of gas barrier properties even after bending the laminate, and to improve the heat resistance of the laminate. In addition, it is possible to suppress the deterioration of gas barrier properties even after the laminate is subjected to the retort treatment and boiling treatment described below. It is more preferable that the high-melting-point resin material be nylon 6, nylon MXD6, or nylon MXD6I.

[0054] The content of the high-melting-point resin material in the surface resin layer is preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more.

[0055] The surface resin layer may contain a resin material other than the high-melting-point resin material as long as the properties of the present invention are not impaired. The surface resin layer may contain additives as long as the properties of the present invention are not impaired. Examples of additives include crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0056] The ratio of the thickness of the surface resin layer to the total thickness of the biaxially oriented polypropylene substrate is preferably 1% or more. The ratio of the thickness of the surface resin layer to the total thickness of the biaxially oriented polypropylene substrate is preferably 10% or less, and more preferably 5% or less. By making the ratio of the thickness of the surface resin layer to the total thickness of the biaxially oriented polypropylene substrate 1% or more, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaged product can be further improved. By making the ratio of the thickness of the surface resin layer to the total thickness of the biaxially oriented polypropylene substrate 10% or less, the film-forming properties and processability of the biaxially oriented polypropylene substrate can be further improved. In addition, the recyclability of packaged products produced using a laminate with a sealant layer made of polypropylene can be improved.

[0057] The thickness of the surface resin layer is preferably 0.1 μm or more. The thickness of the surface resin layer is preferably 5 μm or less, and more preferably 4 μm or less. By making the thickness of the surface resin layer 0.1 μm or more, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaged product can be further improved. Furthermore, by making the thickness of the surface resin layer 5 μm or less, the film-forming properties and processability of the biaxially oriented polypropylene substrate can be further improved. In addition, the recyclability of packaged products produced using a laminate with a sealant layer made of polypropylene can be improved.

[0058] (adhesive resin layer) In one embodiment of the present invention, an adhesive resin layer may be provided between the biaxially oriented polypropylene substrate and the surface resin layer, thereby improving the interlayer adhesion between the biaxially oriented polypropylene substrate and the surface resin layer.

[0059] The adhesive resin layer can be formed from adhesive resins such as polyether, polyester, silicone resin, epoxy resin, polyurethane, vinyl resin, phenolic resin, polyolefin, and acid-modified polyolefin. Among these, from the viewpoint of recyclability, polyolefin and its acid-modified polyolefin are preferred, and polypropylene and its acid-modified polyolefin are particularly preferred. Commercially available adhesive polypropylene can be used, for example, the Admer series manufactured by Mitsui Chemicals, Inc.

[0060] The thickness of the adhesive resin layer is not particularly limited, but can be, for example, 1 μm or more and 15 μm or less. By making the thickness of the adhesive resin layer 1 μm or more, the adhesion between the polypropylene resin layer and the surface resin layer can be further improved. By making the thickness of the adhesive resin layer 15 μm or less, the processability of the biaxially oriented polypropylene substrate can be improved.

[0061] The biaxially oriented polypropylene substrate composed of the above-mentioned layers is subjected to a stretching treatment. The stretching treatment improves the mechanical strength. The stretching treatment may be uniaxial or biaxial.

[0062] In one embodiment, the biaxially oriented polypropylene substrate is a co-extruded film. The co-extruded film can be produced by forming a film using a T-die method, an inflation method, or the like, forming a laminated film, and then stretching it. The inflation method is preferred from the viewpoint of productivity, since it allows film formation and stretching to be carried out continuously in one step.

[0063] The stretching ratio of the biaxially oriented polypropylene substrate in the machine direction (MD) and the transverse direction (TD) is preferably 2 times or more, and more preferably 5 times or more. The stretching ratio of the biaxially oriented polypropylene substrate in the machine direction (MD) and the transverse direction (TD) is preferably 15 times or less, and more preferably 13 times or less. By setting the stretching ratio to 2 times or more, the strength of the biaxially oriented polypropylene substrate can be further improved. In addition, the printability of the biaxially oriented polypropylene substrate can be improved. On the other hand, from the viewpoint of the breaking limit of the biaxially oriented polypropylene substrate, the stretching ratio is preferably 15 times or less. When the polypropylene resin layer of the biaxially oriented polypropylene substrate is made heat-sealable to produce a packaged product (e.g., a tube) that is produced by sealing an envelope, the stretching ratio is more preferably 2 times or more and 10 times or less, and particularly preferably 2.5 times or more and 7 times or less.

[0064] In one embodiment, the biaxially oriented polypropylene substrate is preferably stretched so that its tensile strength in the machine direction (MD) is greater than its tensile strength in the transverse direction (TD). This configuration allows the packaging product produced from the laminate of the present invention to be highly tearable in one direction. The tensile strength of the biaxially oriented polypropylene substrate in the machine direction (MD) is preferably 1.05 times or more, more preferably 1.10 times or more, and even more preferably 1.2 times or more, of the tensile strength in the transverse direction (TD). The tensile strength in the machine direction (MD) can be, for example, 200 MPa or more and 300 MPa or less. In this specification, the tensile strength of the biaxially oriented polypropylene substrate is measured in accordance with JIS K7127:1999. The tensile tester STA-1150 manufactured by Orientec Co., Ltd. can be used as a measuring instrument. A rectangular film 15 mm wide and 150 mm long cut from the biaxially oriented polypropylene substrate can be used as a test piece. The distance between the pair of chucks holding the test specimen at the start of the measurement was 100 mm, and the tensile speed was 300 mm / min. Unless otherwise specified, the environment during the tensile strength measurement was a temperature of 23°C and a relative humidity of 50%.

[0065] The surface resin layer constituting the biaxially oriented polypropylene substrate may be subjected to a surface treatment, which improves adhesion to the adjacent layer (deposited film). The surface treatment method is not particularly limited, and examples include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using one or more gases selected from argon gas, oxygen gas, nitrogen gas, etc., and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals.

[0066] When a surface resin layer is provided, a vapor-deposited film made of an inorganic oxide is provided on the surface resin layer. That is, the vapor-deposited film is adjacent to the surface resin layer. This can impart gas barrier properties, specifically oxygen barrier properties and water vapor barrier properties, to the laminate. Furthermore, weight loss of contents filled in a packaged product made using the laminate of the present invention can be suppressed.

[0067] The first biaxially oriented polypropylene substrate may have a surface coating layer on its surface instead of the anchor coating layer or the surface resin layer.

[0068] (surface coating layer) The biaxially oriented polypropylene substrate has a surface coating layer containing a resin material having a polar group on a polypropylene resin layer. This allows a vapor-deposited film with high adhesion to be formed on the surface coating layer, improving gas barrier properties. Furthermore, as described below, packaging products produced using a laminate with the surface coating layer have high lamination strength. In one embodiment, the surface coating layer may be provided on the polypropylene resin layer. That is, the surface coating layer may be adjacent to the polypropylene resin layer.

[0069] The surface coating layer contains a resin material having a polar group. In the present invention, the polar group refers to a group containing one or more heteroatoms. Examples of polar groups include ester groups, epoxy groups, hydroxyl groups, amino groups, amide groups, carboxyl groups, carbonyl groups, carboxylic anhydride groups, sulfone groups, thiol groups, and halogen groups. Among these, from the viewpoint of lamination properties of packaged products, carboxyl groups, carbonyl groups, ester groups, hydroxyl groups, and amino groups are preferred, and carboxyl groups and hydroxyl groups are more preferred.

[0070] Preferred resin materials having polar groups include polyester, polyethyleneimine, hydroxyl group-containing (meth)acrylic resin, polyamides such as nylon 6, nylon 6,6, nylon MXD6, and amorphous nylon, polyurethane, etc. Use of such resin materials can significantly improve the adhesion of the vapor-deposited film formed on the surface coating layer, and can effectively improve its gas barrier properties.

[0071] In one embodiment, the resin material having a polar group is preferably a hydroxyl group-containing (meth)acrylic resin, which can improve the heat resistance of the laminate and can prevent the gas barrier properties from deteriorating even after the laminate is subjected to retort treatment and boiling treatment.

[0072] In one embodiment of the present invention, the hydroxyl group-containing (meth)acrylic resin used to form the surface coating layer is a polymer of a neutral monomer and a hydroxyl group-containing (meth)acrylic monomer. Examples of the neutral monomer include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, styrene, vinyl toluene, and vinyl acetate. Examples of the hydroxyl group-containing (meth)acrylic monomer include 2-hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate.

[0073] The glass transition temperature (Tg) of the hydroxyl group-containing (meth)acrylic resin is preferably 50°C or higher, more preferably 70°C or higher. The glass transition temperature (Tg) of the hydroxyl group-containing (meth)acrylic resin is preferably 200°C or lower, more preferably 150°C or lower. By increasing the glass transition temperature (Tg) of the hydroxyl group-containing (meth)acrylic resin to 50°C or higher, blocking resistance can be improved. By increasing the glass transition temperature (Tg) of the hydroxyl group-containing (meth)acrylic resin to 200°C or lower, the reactivity of an isocyanate compound used together with the hydroxyl group-containing (meth)acrylic resin in forming a surface coating layer can be improved. In this specification, Tg can be measured in accordance with JIS K7121:2012 (Method for measuring transition temperature of plastics). Specifically, Tg can be determined by measuring a DSC curve at a heating rate of 10°C / min using a differential scanning calorimetry (DSC) device.

[0074] The number average molecular weight of the hydroxyl group-containing (meth)acrylic resin is preferably 10,000 or more. The number average molecular weight of the hydroxyl group-containing (meth)acrylic resin is preferably 100,000 or less. By making the number average molecular weight of the hydroxyl group-containing (meth)acrylic resin 10,000 or more, blocking resistance can be improved. By making the number average molecular weight of the hydroxyl group-containing (meth)acrylic resin 100,000 or more, ease of forming a surface coating layer can be improved. In this specification, the number average molecular weight can be measured by gel permeation chromatography (GPC). In GPC measurement, the number average molecular weight of the polymer is generally measured in terms of standard polystyrene.

[0075] The hydroxyl value of the hydroxyl group-containing (meth)acrylic resin is preferably 20 mg KOHL / g or more, more preferably 30 mg KOHL / g or more. The hydroxyl value of the hydroxyl group-containing (meth)acrylic resin is preferably 200 mg KOHL / g or less, more preferably 150 mg KOHL / g or less. By making the hydroxyl group value of the hydroxyl group-containing (meth)acrylic resin 20 mg KOHL / g or more, the reactivity of an isocyanate compound when used together with the hydroxyl group-containing (meth)acrylic resin to form a surface coating layer can be improved. By making the hydroxyl group value of the hydroxyl group-containing (meth)acrylic resin 200 mg KOHL / g or less, the amount of isocyanate compound used can be reduced, thereby reducing production costs. In this specification, hydroxylation can be measured in accordance with JIS K0070:1992 (Test methods for oxidation, saponification value, ester value, iodine value, hydroxyl value, and unsaponifiable matter of chemical products).

[0076] In the present invention, the surface coating layer can be formed using an aqueous emulsion or a solvent-based emulsion. Specific examples of aqueous emulsions include polyamide-based emulsions, polyethylene-based emulsions, and polyurethane-based emulsions. Specific examples of solvent-based emulsions include polyester-based emulsions.

[0077] The content of the resin material having a polar group in the surface coating layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0078] The surface coating layer may contain a resin material other than the resin material having a polar group, provided that the properties of the present invention are not impaired. In one embodiment of the present invention, the surface coating layer may contain an isocyanate compound. The surface coating layer may contain additives, provided that the properties of the present invention are not impaired. Examples of additives include crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0079] The ratio of the thickness of the surface coating layer to the total thickness of the biaxially oriented polypropylene substrate is preferably 0.08% or more, more preferably 0.2% or more, even more preferably 1% or more, and even more preferably 3% or more. The ratio of the thickness of the surface coating layer to the total thickness of the biaxially oriented polypropylene substrate is preferably 20% or less, more preferably 10% or less. By making the ratio of the thickness of the surface coating layer to the total thickness of the biaxially oriented polypropylene substrate 0.08% or more, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaged product can be further improved. By making the ratio of the thickness of the surface coating layer to the total thickness of the biaxially oriented polypropylene substrate 20% or less, the film-forming properties and processability of the biaxially oriented polypropylene substrate can be further improved. In addition, the recyclability of packaged products produced using the laminate of the present invention can be improved.

[0080] The thickness of the surface coating layer is preferably 0.02 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. The thickness of the surface coating layer is preferably 10 μm or less, more preferably 5 μm or less. By making the thickness of the surface coating layer 0.02 μm or more, the adhesion of the vapor-deposited film can be further improved, and the gas barrier properties can be further improved. In addition, the laminate strength of the packaged product can be further improved. By making the thickness of the surface coating layer 10 μm or less, the film-forming properties and processability of the biaxially oriented polypropylene substrate can be further improved. In addition, the recyclability of packaged products produced using the laminate of the present invention can be improved.

[0081] Biaxially oriented polypropylene substrates can be produced offline, specifically by forming a resin composition containing polypropylene into a film using a T-die method, inflation method, or the like, to form a resin film, stretching the film, applying a coating liquid for forming a coat onto the resin film, and drying the film. Biaxially oriented polypropylene substrates can also be produced in-line, specifically by forming a resin composition containing polypropylene into a film using a T-die method, inflation method, or the like, to form a resin film, stretching the film in the machine direction (MD), applying a coating liquid for forming a coat onto the resin film, drying the film, and then stretching the film in the transverse direction (TD). Stretching in the transverse direction may be performed first. Stretching in both the machine direction and the transverse direction may be performed before or after applying the coating liquid for forming a coat.

[0082] The first biaxially oriented polypropylene substrate is preferably transparent. Specifically, it preferably has a high total light transmittance measured in accordance with JIS K 7361-1:1997. Specifically, the total light transmittance is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

[0083] [Inorganic oxide vapor deposited film] Next, the inorganic oxide vapor-deposited film 20 formed on the surface side of the first layer of the first biaxially oriented polypropylene substrate 10 will be described.

[0084] The barrier film has a vapor-deposited film made of an inorganic oxide as a gas barrier layer. A vapor-deposited film may be provided on the anchor coat layer. This improves the gas barrier properties, specifically the oxygen barrier properties and water vapor barrier properties.

[0085] Examples of inorganic oxides include aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). Among these, silica and alumina are preferred.

[0086] The thickness of the vapor-deposited film is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 7 nm or more and 40 nm or less. When the thickness is equal to or greater than the lower limit, for example, the oxygen barrier property and water vapor barrier property of the barrier substrate can be further improved. When the thickness is equal to or less than the upper limit, for example, the occurrence of cracks in the vapor-deposited film can be suppressed, and the recyclability of the packaging material can be improved.

[0087] Examples of methods for forming a vapor-deposited film include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0088] The vapor-deposited film may be a single layer formed by a single vapor deposition process, or may be a multilayer formed by multiple vapor deposition processes. When the vapor-deposited film is a multilayer film, each layer may be composed of the same inorganic oxide or different inorganic oxides. Each layer may be formed by the same method or different methods.

[0089] [Coating layer] The coating layer 30 formed on the inorganic oxide vapor-deposited film 20 is an organic coating film (barrier coat layer) that protects the inorganic oxide vapor-deposited film mechanically and chemically and also improves the barrier performance.

[0090] The coating layer is formed by applying a barrier coating agent onto the inorganic oxide vapor deposition film and then solidifying it. The barrier coating agent is composed of a metal alkoxide, a water-soluble polymer, and optionally a silane coupling agent, a sol-gel catalyst, an acid, etc.

[0091] As the metal alkoxide, a compound represented by the general formula R1 n M(OR 2 ) m (wherein, R1 and R2 represent an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M), and examples of the metal atom represented by M in the metal alkoxide include silicon, zirconium, titanium, aluminum, and the like. For example, it is preferable to use an alkoxysilane in which M is Si.

[0092] The alkoxysilane may be, for example, one represented by the general formula Si(ORa)4 (wherein Ra represents a lower alkyl group). In the above, Ra may be a methyl group, an ethyl group, an n-propyl group, an n-butyl group, or the like. Specific examples of the alkoxysilane include tetramethoxysilane Si(OCH3)4, tetraethoxysilane Si(OC2H5)4, tetrapropoxysilane Si(OC3H7)4, tetrabutoxysilane Si(OC4H9)4, and the like. Two or more of the alkoxides may be used in combination.

[0093] Silane coupling agents having reactive groups such as vinyl, epoxy, methacryl, and amino groups can be used. Organoalkoxysilanes having epoxy groups are particularly suitable, such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyldimethylmethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethylethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The above-mentioned silane coupling agents may be used alone or in combination of two or more.

[0094] In particular, the crosslink density of the cured film of the coating layer using bifunctional compounds such as γ-glycidoxypropylmethyldimethoxysilane and γ-glycidoxypropylmethyldiethoxysilane is lower than that of systems using trialkoxysilanes. As a result, the cured film has excellent gas barrier properties and hot water treatment resistance, while also being flexible and has excellent flex resistance, so that packaging materials using this barrier film are resistant to deterioration in gas barrier properties even after Gelbo Flex testing.

[0095] The water-soluble polymer may be a polyvinyl alcohol resin or an ethylene-vinyl alcohol copolymer, either singly or in combination. In the coating layer according to the present embodiment, a polyvinyl alcohol resin is preferred.

[0096] Generally, polyvinyl alcohol resins obtained by saponifying polyvinyl acetate can be used. The polyvinyl alcohol resin may be a partially saponified polyvinyl alcohol resin in which several tens of percent of acetate groups remain, a fully saponified polyvinyl alcohol in which no acetate groups remain, or a modified polyvinyl alcohol resin in which OH groups have been modified. The polyvinyl alcohol resin must have a saponification degree that at least induces crystallization, which improves the film hardness of the gas barrier coating film. A saponification degree of 70% or higher is preferred. Furthermore, polyvinyl alcohol resins with a polymerization degree within the range used in conventional sol-gel processes (approximately 100 to 5000) can be used. Examples of such polyvinyl alcohol resins include RS resin "RS-110" (saponification degree = 99%, polymerization degree = 1,000) manufactured by Kuraray Co., Ltd., and "GOHSENOL NM-14" (saponification degree = 99%, polymerization degree = 1,400) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.

[0097] The ethylene-vinyl alcohol copolymer may be a saponified copolymer of ethylene and vinyl acetate, i.e., a product obtained by saponifying an ethylene-vinyl acetate random copolymer. For example, it may range from a partially saponified product in which several tens of mole percent of acetate groups remain to a completely saponified product in which only a few mole percent of acetate groups remain, or even no acetate groups remain, and is not particularly limited. However, from the viewpoint of barrier properties, the preferred lower limit of the degree of saponification is 80% or more, more preferably 90% or more, and even more preferably 95% or more. The upper limit is 100% or less.

[0098] As the catalyst for the sol-gel method, an acid or amine compound is suitable.

[0099] Examples of acids that can be used include mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as acetic acid and tartaric acid.

[0100] The acid content is preferably 0.001 to 0.05 mol%, more preferably 0.01 to 0.03 mol%, relative to the total molar amount of alkoxy groups in the metal alkoxide. If the acid content is less than 0.001 mol%, the catalytic effect is too weak, whereas if the acid content is more than 0.05 mol%, the catalytic effect is too strong, causing the reaction rate to become too fast and tending to become non-uniform.

[0101] As the amine compound, a tertiary amine that is substantially insoluble in water and soluble in an organic solvent is suitable. Specifically, for example, N,N-dimethylbenzylamine, tripropylamine, tributylamine, tripentylamine, etc. can be used. N,N-dimethylbenzylamine is particularly suitable.

[0102] The content of the amine compound is preferably, for example, 0.01 to 1.0 part by mass, particularly 0.03 to 0.3 part by mass, per 100 parts by mass of the metal alkoxide. If the content is less than 0.01 part by mass, the catalytic effect is too small, whereas if the content is more than 1.0 part by mass, the catalytic effect is too strong, causing the reaction rate to become too fast and tending to become non-uniform.

[0103] As the solvent, it is preferable to use water or alcohol such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropanol, or n-butanol.

[0104] The barrier coating layer 3 formed as described above has a layer thickness of 100 to 500 nm, preferably 200 to 400 nm, which is preferable because the coating film does not crack and the surface of the deposited film is sufficiently coated.

[0105] When the barrier coating agent contains a silane coupling agent, it can contain 5 to 10 parts by mass of a water-soluble polymer such as a polyvinyl alcohol resin and 1 to 10 parts by mass of the silane coupling agent per 100 parts by mass of alkoxysilane. This allows the film to maintain its flexibility. In the above case, using more than 20 parts by mass of the silane coupling agent is undesirable, as it increases the rigidity and brittleness of the resulting barrier coating film.

[0106] Furthermore, when a silane coupling agent is not contained, the amount of metal alkoxide can be reduced and the barrier properties can be improved by using 10 to 20 parts by mass of a water-soluble polymer such as a polyvinyl alcohol resin per 100 parts by mass of alkoxysilane.

[0107] In the coating layer, the lower limit of the ratio of the mass of the metal alkoxide such as tetraethoxysilane, calculated as SiO2, to the mass of the water-soluble resin such as polyvinyl alcohol is preferably 1.6 or more, more preferably 1.9 or more. The upper limit is preferably 3.9 or less, more preferably 3.5 or less. A ratio of more than 3.9 is undesirable because the barrier properties may deteriorate after post-processing or the Gelbo Flex test, while a ratio of less than 1.6 is undesirable because the barrier properties after retort treatment deteriorate.

[0108] The coating layer may be formed by applying and solidifying a resin composition containing one or more resins (gas barrier resins) selected from the group consisting of urethane resin, acrylic resin, polyvinylidene chloride resin, polyvinyl alcohol resin (PVA), ethylene-vinyl alcohol copolymer resin (EVOH), polyacrylonitrile, nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6), in addition to the above-mentioned metal alkoxide and water-soluble polymer. If necessary, the coating layer may further contain a silane coupling agent or silica fine particles.

[0109] The inclusion of a urethane resin in the coating layer provides the coating layer with appropriate elasticity or flexibility, reducing the impact on the vapor-deposited film of pressure during printing or lamination, and suppressing deterioration of the gas barrier properties. As the urethane resin, any of conventionally known polyester urethane resins and polyether urethane resins can be used. As such a urethane resin, a reaction product of a polyol, such as a polyester polyol or a polyether polyol, with a polyisocyanate can be used.

[0110] Examples of the polyester polyol include polyester polyols obtained by reacting a low-molecular-weight polyol with a polycarboxylic acid, polyester polyols obtained by ring-opening polymerization of a cyclic ester compound such as ε-caprolactone, and polyester polyols obtained by copolymerizing these. These polyester polyols can be used alone or in combination of two or more.

[0111] Examples of low-molecular-weight polyols include aliphatic polyols with a molecular weight of approximately 50 to 300, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol; polyols with an aliphatic cyclic structure, such as cyclohexanedimethanol; and polyols with an aromatic structure, such as bisphenol A and bisphenol F. Examples of polycarboxylic acids that can be used to produce polyester polyols include aliphatic polycarboxylic acids, such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic polycarboxylic acids, such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and anhydrides or esters thereof. Furthermore, polyester polyols can also be used, such as polyester polyurethane polyols having urethane bonds in their molecular structure, obtained by modifying the above polyester polyols with polyisocyanates. These polyester polyols can be used alone or in combination of two or more.

[0112] Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxides using one or more compounds having two or more active hydrogen atoms as initiators. Examples of the compounds having two or more active hydrogen atoms include propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerin, diglycerin, trimethylolethane, trimethylolpropane, water, and hexanetriol. Examples of the alkylene oxide include propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran. Polyether polyols can also be used, such as polyether polyurethane polyols having urethane bonds in their molecular structure, obtained by modifying the polyether polyols described above with polyisocyanates. These polyether polyols can be used alone or in combination of two or more.

[0113] Examples of the polyisocyanate include polyisocyanates having an aliphatic cyclic structure such as cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate; aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Among these, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, and crude diphenylmethane diisocyanate are preferred. These polyisocyanates can be used alone or in combination of two or more.

[0114] When the coating layer contains a polyvinyl alcohol resin, the oxygen barrier property and water vapor barrier property are improved, and the occurrence of cracks in the vapor-deposited film can be effectively prevented.

[0115] As the silane coupling agent, a conventionally known silane coupling agent can be used, and for example, the same silane coupling agent as that used in the gas barrier resin composition described above is preferably used. By including a silane coupling agent in the primer layer, the interlayer adhesion with the barrier coat layer can be improved.

[0116] As the silica fine particles, conventionally known silica can be used. In particular, when the urethane resin is polyether polyurethane, the inclusion of silica fine particles in the primer layer can suppress blocking during winding in the production process of the gas barrier vapor-deposited film.

[0117] The content of the gas barrier resin in the coating layer is preferably 50% by mass or more, more preferably 75% by mass or more. By making the content of the gas barrier resin in the coating layer 50% by mass or more, the oxygen barrier property and water vapor barrier property can be further improved. The content of the gas barrier resin in the coating layer is preferably 95% by mass or less, more preferably 90% by mass or less.

[0118] The thickness of the coating layer is preferably 0.01 μm or more, more preferably 0.1 μm or more. The thickness of the coating layer is preferably 10 μm or less, more preferably 5 μm or less. By making the thickness of the coating layer 0.01 μm or more, the oxygen barrier property and water vapor barrier property of the laminate can be further improved. On the other hand, by making the thickness of the coating layer 10 μm or less, the processability of the laminate can be improved. Furthermore, as long as the thickness of the coating layer is within the above range, recycling suitability is not impaired even when a different material other than polypropylene is used.

[0119] The coating layer can be formed by dissolving or dispersing the gas barrier resin in water or a suitable solvent, applying the solution, and drying. Alternatively, the coating layer can be formed by applying a commercially available coating agent and drying it.

[0120] [Adhesive layer] The surface of the barrier film facing the first biaxially oriented polypropylene substrate 10 is laminated to the sealant layer 50 via a first adhesive layer 61, and the surface of the barrier film facing the coating layer 30 is laminated to the second biaxially oriented polypropylene substrate 40 via an adhesive layer 62. This improves the adhesion between the barrier film and the sealant layer, and between the first biaxially oriented polypropylene substrate and the second substrate, and prevents the degradation of barrier properties during heat sterilization treatments such as retort and boiling.

[0121] The first adhesive layer 61 and the second adhesive layer 62 may be a one-component curing adhesive, a two-component curing adhesive, or a non-curing adhesive. The adhesive may be a solventless adhesive or a solvent-based adhesive suitable for dry lamination.

[0122] Examples of solvent-free adhesives, i.e., non-solvent lamination adhesives, include polyether adhesives, polyester adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives. Among these, urethane adhesives are preferred, and two-component curing urethane adhesives are more preferred.

[0123] Examples of solvent-based adhesives include rubber-based adhesives, vinyl-based adhesives, olefin-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and urethane-based adhesives. Among these, urethane-based adhesives are preferred, and two-component curing urethane-based adhesives are more preferred.

[0124] The thickness of the adhesive layer is, for example, 0.1 μm or more and 10 μm or less, preferably 0.2 μm or more and 8 μm or less, and more preferably 0.5 μm or more and 6 μm or less.

[0125] [Second biaxially oriented polypropylene base material] The second biaxially oriented polypropylene substrate 40 is laminated to the surface of the barrier film facing the covering layer 30 via a second adhesive layer 62. Here, the second biaxially oriented polypropylene substrate may be the same as the first biaxially oriented polypropylene substrate 10, and therefore a description thereof will be omitted.

[0126] In the case of a three-layer structure as shown in Figure 1, the printed layer (not shown) may be formed on the surface of the outermost layer of the second biaxially oriented polypropylene substrate 40, or on the surface of the second biaxially oriented polypropylene substrate 40 on the side of the second adhesive layer 62.

[0127] [Sealant layer] The sealant layer 50 contains a resin material that can be fused to each other by heat. Examples of the resin material that can be fused to each other by heat include polyolefins, and specific examples include polyethylenes such as low-density polyethylene, linear low-density polyethylene, and medium-density polyethylene, polypropylene, polybutene, methylpentene polymers, and cyclic olefin copolymers.

[0128] The sealant layer is preferably made of polypropylene. This allows the three-layer film to be made entirely of polypropylene, making it possible to achieve a mono-material packaging material. After collecting used packaging material, there is no need to separate the base material and the sealant layer, improving the recyclability of the packaging material. By making the sealant layer of polypropylene, oil resistance can also be improved, making it possible to create a sealant layer that can withstand heat sterilization treatment.

[0129] The polypropylene content in the sealant layer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, which can improve the recyclability of the packaging material, for example.

[0130] When the sealant layer is made of polypropylene, the content of polypropylene relative to the total amount of resin materials contained in the laminate is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 88% by mass or more, and particularly preferably 90% by mass or more. This allows, for example, the laminate to be used to produce a mono-material packaging material, improving the recyclability of the packaging material.

[0131] Examples of polypropylene include propylene homopolymers, propylene random copolymers such as propylene-α-olefin random copolymers, and propylene block copolymers such as propylene-α-olefin block copolymers. Details of α-olefins are as described above. From the viewpoint of heat sealability, the density of polypropylene is, for example, 0.88 g / cm. 3 More than 0.92g / cm 3 The density is measured in accordance with JIS K7112, particularly Method D (density gradient tube method, 23°C). From the viewpoint of reducing the environmental load, biomass-derived polypropylene and / or recycled polypropylene may be used.

[0132] The sealant layer may contain additives. Examples of additives include crosslinkers, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, lubricants, antistatic agents, pigments, and modifying resins. For example, the sealant layer may contain an antistatic agent. This can suppress the generation of static electricity on the surface of the laminate, thereby suppressing adhesion between laminates, for example.

[0133] The sealant layer may have a single-layer structure or a multi-layer structure. The thickness of the sealant layer is preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 150 μm or less. When the thickness is equal to or greater than the lower limit, for example, the lamination strength of a packaging material including the laminate can be further improved. When the thickness is equal to or less than the upper limit, for example, the processability of the laminate can be further improved. When a pouch (particularly a retort pouch) is produced from the laminate, the thickness of the sealant layer is more preferably 30 μm or more and 100 μm or less.

[0134] From the viewpoint of heat sealing properties, the sealant layer is preferably an unstretched resin film, more preferably an unstretched polypropylene film. The resin film can be produced by, for example, a casting method, a T-die method, or an inflation method. The sealant layer may be laminated via an adhesive layer as in the present embodiment, or may be formed by melt-extruding a resin material that can be fused to the barrier film by heat onto the barrier film.

[0135] [Other lamination examples] 2 shows an example in which the covering layer 30 of the barrier film is formed with the sealant layer 50 via the first adhesive layer 61. As described above, in the present invention, the laminate is not limited to a three-layer film structure, but may also have a two-layer structure.

[0136] [Packaging products] The laminate can be formed into a bag shape with the sealant layer facing inward, and used as a packaging product such as a packaging bag for containing contents such as food. The laminate of the present invention is a heat-sterilized laminate used for a packaging bag for containing retort foods or boiled foods.

[0137] The term "heat sterilization treatment" includes not only retort treatment but also boiling treatment, which refers to heat sterilization at 60 to 100°C for 10 to 60 minutes, for example.

[0138] Retort treatment refers to a heat-pressure sterilization treatment at 100 to 140°C. The F value, which is a concept that represents the integrated value of the heat load, is 4 or more, more specifically, a heat-pressure sterilization treatment at 121°C for 3 minutes or more, or a heat-pressure sterilization treatment at 120°C for 4 minutes or more as stipulated by the Food Sanitation Act, is preferred. More specifically, a heat-pressure sterilization treatment at 120°C for 30 to 60 minutes is most common, but semi-retort treatment at 105 to 115°C for 30 to 60 minutes or high-temperature retort (HTST) treatment at 130 to 140°C for 30 to 60 minutes is also acceptable.

[0139] [Combined elastic modulus and indentation hardness of coating layer] In the present invention, the composite modulus and indentation hardness after lamination and the above-mentioned heat sterilization treatment are measured by nanoindentation from a cross section of the coating layer of the laminate, and are 5.0 GPa to 9.5 GPa, and the indentation hardness is 0.9 GPa to 1.7 GPa. Within these ranges, the degradation of barrier properties of the laminate can be suppressed not only after boiling treatment but also after retort treatment. Preferably, the composite modulus is 5.5 GPa to 9.5 GPa, and the indentation hardness is 0.9 GPa to less than 1.5 GPa, or the composite modulus is 7.1 GPa to 8.2 GPa, and the indentation hardness is 1.5 GPa to 1.7 GPa. This allows the packaging material after heat sterilization treatment (described later) to have an oxygen permeability of 1.0 cc / m 2 at 23°C and 90% RH in accordance with JIS K 7126-2 after retort treatment. 2 ·day·atm or less.

[0140] It is more preferable that the composite elastic modulus is 6.0 GPa or more and 9.0 GPa or less and the indentation hardness is 1.0 GPa or more and 1.5 GPa or less (or the indentation hardness is 1.0 GPa or more and less than 1.5 GPa), which can suppress deterioration of the barrier properties even after high-temperature retort treatment of the laminate.

[0141] The indentation hardness of the coating layer is calculated by the following formula (1): Furthermore, the composite elastic modulus of the coating layer is calculated by the following formula (2). Indentation hardness = Pmax / A (1)

number

[0142] where: Pmax: Maximum load (unit: μN) A: Contact projection area at maximum depth (unit: μm 2 ) S: Contact stiffness is.

[0143] The composite modulus and indentation hardness of the coating layer of the barrier film alone, the dry-laminated laminate before heat sterilization, and the dry-laminated laminate after heat sterilization were measured by embedding each sample in epoxy resin or the like and processing it with a microtome to expose the cross-section of the coating layer. This allows measurements to be made using the nanoindentation method from the "cross-section" of the coating layer of the laminate. This method allows the composite modulus and indentation hardness of the coating layer to be measured without peeling the laminate to expose the coating layer. The cross-section was obtained by cutting the film in the thickness direction perpendicular to the main surface. The cross-section was prepared by embedding the film in an embedding resin to create a block, and then cutting the block using a commercially available rotary microtome at room temperature (23°C). Finishing was performed using a diamond knife.

[0144] To measure the indentation hardness and composite modulus of the cross section of the coating layer using the nanoindentation method, first, place an indenter on the cross section of the coating layer, press the indenter into the cross section to a load of 15 μN over 10 seconds, and hold that position for 5 seconds. The indenter is pressed into the exposed cross section of the coating layer, near the center of the thickness of the coating layer. The load is then released over 10 seconds. This provides the maximum load Pmax, the contact projected area A at maximum depth, and the load-displacement curve. Unless otherwise specified, measurements are performed in an environment of 50% relative humidity and 23°C. Measurements are performed at five or more locations on the same cross section, and the indentation hardness and composite modulus are reported as the arithmetic mean of the values ​​measured at five locations with good reproducibility. Further detailed measurement conditions are described in the Examples.

[0145] When the laminate is subjected to heat sterilization, the coating layer must have a certain degree of hardness to prevent destruction of the vapor-deposited layer due to thermal shrinkage of the OPP substrate during heat sterilization. On the other hand, during lamination processing of packaging materials, the OPP substrate is stretched by tension, which also causes destruction of the vapor-deposited layer and a decrease in barrier properties, but this can be prevented by imparting appropriate flexibility to the coating layer.

[0146] The inventors have discovered a range of elastic modulus and indentation hardness suitable for heat sterilization treatment applications such as retort treatment for the coating layer that constitutes a monomaterial packaging material, which is a laminate of polypropylene films, and have found a laminate that can suppress a decrease in barrier properties even after "heat sterilization treatment" of "lamination."

[0147] This has resulted in the packaging material after heat sterilization having an oxygen permeability of 10.0cc / m at 23°C and 90% RH, in accordance with JIS K 7126-2. 2 ·day·atm or less, preferably 5.0cc / m 2 ·day·atm or less has been achieved.

[0148] The composite elastic modulus and indentation hardness of the coating layer can be adjusted, for example, by the composition of the coating layer or the drying temperature during coating layer formation. [Example]

[0149] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these descriptions in any way.

[0150] Example 1 The first biaxially oriented polypropylene substrate 10 was a 20 μm thick biaxially oriented polypropylene film (the first surface layer on the vapor-deposited side was a 1.0 μm thick layer made of a copolymer of propylene, ethylene, and butene, the second surface layer on the non-vapor-deposited side was a 1.0 μm thick layer made of a copolymer of propylene, ethylene, and butene, and the middle layer was an 18.0 μm thick layer made of a polypropylene homopolymer).A 200 nm thick anchor coat layer made of a liquid mixture of a hydroxyl group-containing (meth)acrylic resin and tolylene diisocyanate was formed on one side of the first biaxially oriented polypropylene substrate 10, and a 10 nm thick inorganic oxide vapor deposition film 20 of aluminum oxide was formed on the anchor coat layer by PVD vapor deposition.

[0151] For the coating layer of Example 1, solution A was prepared by mixing a water-soluble polymer, polyvinyl alcohol with a saponification degree of 99% or more and a polymerization degree of 2400, with a liquid of water and isopropyl alcohol in a ratio of 95 / 5 to give a solids content of 4%. Water, isopropyl alcohol, and 1N hydrochloric acid were mixed in a ratio of 65 / 34 / 1 to obtain a prepared solution B. Tetraethoxysilane was used as a metal alkoxide to prepare solution C. Solution D was prepared by mixing Solution B and Solution C at an adjusted ratio, and Solution A and Solution D were mixed at an adjusted ratio to prepare a barrier coating agent. The ratio of solutions B to C and A to D was adjusted so that the solid content of the barrier coating agent after mixing was 7% and the SiO2 equivalent mass of tetraethoxysilane was 2.25 relative to the solid content of PVA. The barrier coating agent prepared above was coated by a direct gravure method onto the inorganic oxide vapor deposition film 20. Thereafter, it was dried at 100°C for 30 seconds to form a coating layer with a dry film thickness of 300 nm, and then aging treatment was performed at 40°C for 7 days to produce a barrier film.

[0152] Next, the surface of the barrier film facing the coating layer 30 was bonded to a second biaxially oriented polypropylene film 40 (thickness: 20 μm) by dry lamination using a polyurethane-based two-component curing solvent-based adhesive 1, with a second adhesive layer 62 interposed therebetween. Furthermore, the surface of the barrier film opposite the coating layer 30 was bonded to a sealant layer (unstretched polypropylene film 60 μm) by dry lamination using a two-component curing solvent-based adhesive, with a first adhesive layer 61 interposed therebetween, to produce a laminate of Example 1.

[0153] Example 2 The laminate of Example 2 was prepared in the same manner as in Example 1, except that the coating layer was a barrier coating agent prepared by mixing solutions B and C and solutions A and D in such a way that the solid content was 7% and the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 2.4, while adjusting the ratio of these two.

[0154] Example 3 The laminate of Example 3 was produced in the same manner as in Example 1, except that when solutions B and C were mixed, 5% of glycidoxypropyltrimethoxysilane was added relative to the weight of tetraethoxysilane, and then the ratios of solutions B and C and solutions A and D were adjusted to mix to form a barrier coating agent with a solid content of 7% and a SiO2-equivalent mass of tetraethoxysilane relative to the solid content of PVA of 2.5, to form a coating layer.

[0155] Example 4 The laminate of Example 4 was prepared in the same manner as in Example 1, except that the coating layer was a barrier coating agent prepared by mixing solutions B and C and solutions A and D in such a way that the solid content was 7% and the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 2.75.

[0156] Example 5 The laminate of Example 5 was produced in the same manner as in Example 1, except that silica was formed as the inorganic oxide vapor deposition film 20 to a thickness of 30 nm by the CVD method, glycidoxypropyltrimethoxysilane was added at 5% relative to the weight of tetraethoxysilane when mixing solutions B and C, and the ratio of solutions B to C and solutions A to D was adjusted to form a barrier coating agent mixed so that the solid content was 7% and the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 3.0.

[0157] Example 6 The laminate of Example 6 was produced in the same manner as in Example 5, except that when solutions B and C were mixed, 5% of glycidoxypropyltrimethoxysilane was added relative to the weight of tetraethoxysilane, and the ratios of solutions B and C and solutions A and D were adjusted to form a barrier coating agent with a solid content of 7% and a SiO2-equivalent mass of tetraethoxysilane relative to the solid content of PVA of 3.5, to form a coating layer.

[0158] Example 7 The laminate of Example 7 was produced in the same manner as Example 6, except that the surface of the barrier film facing the coating layer 30 and a second biaxially oriented polypropylene film 40 (thickness: 20 μm) were bonded together via a second adhesive layer 62 using a polyester polyurethane-based two-component curing solvent-based adhesive 2 by dry lamination.

[0159] Example 8 The laminate of Example 8 was produced in the same manner as Example 6, except that the surface of the barrier film on the coating layer 30 side and a second biaxially oriented polypropylene film 40 (thickness 20 μm) were bonded together via a second adhesive layer 62 by dry lamination using a solvent-free adhesive 3 made of a polyester polymer and a mixture of HDI and XDI as a curing agent.

[0160] Example 9 The laminate of Example 9 was produced in the same manner as in Example 6, except that the surface of the barrier film on the coating layer 30 side and a second biaxially oriented polypropylene film 40 (thickness: 20 μm) were bonded together via a second adhesive layer 62 by dry lamination using a solvent-free adhesive 4 made of a polyester polymer and a mixture of IPDI and HDI as a curing agent.

[0161] Example 10 A laminate of Example 10 was produced in the same manner as in Example 1, except that the drying temperature for the coating layer was 120°C.

[0162] Example 11 A laminate of Example 11 was produced in the same manner as in Example 6, except that the drying temperature for the coating layer was 120°C.

[0163] Example 12 A laminate of Example 12 was produced in the same manner as in Example 6, except that the drying temperature for the coating layer was 110°C.

[0164] Example 19 The barrier coating agent was prepared by adjusting the ratio of solutions B to C and the ratio of solutions A to D so that the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 2.5, and the laminate of Example 19 was prepared in the same manner as in Example 5, except that the aging treatment after drying was carried out at 55°C for 1 day.

[0165] Example 20 The barrier coating agent was prepared by adjusting the ratio of solutions B to C and the ratio of solutions A to D so that the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 2.25, and the laminate of Example 20 was prepared in the same manner as in Example 19, except that the aging treatment after drying was carried out at 55°C for 3 days.

[0166] Example 21 A laminate of Example 21 was produced in the same manner as in Example 19, except that the aging treatment after drying was carried out at 55° C. for 3 days.

[0167] Example 22 The laminate of Example 22 was produced in the same manner as in Example 6, except that a 20 μm thick biaxially oriented polypropylene film (the first surface layer on the vapor-deposited side was a 0.7 μm thick layer made of a propylene-ethylene copolymer, the second surface layer on the non-vapor-deposited side was a 0.7 μm thick layer made of a propylene-ethylene copolymer, and the intermediate layer was an 18.6 μm thick layer made of a polypropylene homopolymer) was used as the first biaxially oriented polypropylene substrate 10.

[0168] Example 23 The laminate of Example 23 was produced in the same manner as in Example 6, except that a 20 μm thick biaxially oriented polypropylene film (the first surface layer on the vapor-deposited side was a 0.7 μm polyamide layer made of a mixture of 50 mass% copolymer of metaxylenediamine and adipic acid and 50 mass% copolymer of hexamethylenediamine and a dicarboxylic acid having a molar ratio of isophthalic acid / terephthalic acid of 2 / 1, the second surface layer on the non-vapor-deposited side was a 0.7 μm thick layer made of a copolymer of propylene, ethylene, and butene, and the intermediate layer was an 18.6 μm thick layer made of polypropylene homopolymer) was used as the first biaxially oriented polypropylene substrate 10.

[0169] (Comparative Example 1) The laminate of Comparative Example 1 was produced in the same manner as in Example 1, except that when solutions B and C were mixed, 5% of glycidoxypropyltrimethoxysilane was added relative to the weight of tetraethoxysilane, and the ratios of solutions B and C and solutions A and D were adjusted to mix a barrier coating agent so that the solid content was 7% and the SiO2 equivalent mass of tetraethoxysilane relative to the solid content of PVA was 1.5, to form a coating layer.

[0170] (Comparative Example 2) A laminate of Comparative Example 2 was produced in the same manner as in Comparative Example 1, except that the drying temperature for the coating layer was 120°C.

[0171] (Comparative Example 3) The laminate of Comparative Example 3 was prepared in the same manner as in Example 5, except that when solutions B and C were mixed, 5% of glycidoxypropyltrimethoxysilane was added relative to the weight of tetraethoxysilane, and the ratios of solutions B and C and solutions A and D were adjusted to form a barrier coating agent having a solid content of 7% and a SiO2-equivalent mass of tetraethoxysilane relative to the solid content of PVA of 4.0, to form the coating layer.

[0172] Comparative Example 4 The laminate of Comparative Example 4 was produced in the same manner as in Comparative Example 3, except that when mixing solutions B and C, 15% of 1,3,5-tris(3-trialkoxysilylpropyl) isocyanurate was added relative to the weight of tetraethoxysilane, and the ratios of solutions B and C and solutions A and D were adjusted to mix to form a barrier coating agent with a solid content of 7% and a SiO2-equivalent mass of tetraethoxysilane relative to the solid content of PVA of 4.0.

[0173] Comparative Example 9 A laminate of Comparative Example 9 was produced in the same manner as in Example 6, except that the coating layer was formed by spin coating, the drying temperature for the coating layer was 80° C. for 60 seconds, and no aging treatment was performed.

[0174] (Comparative Example 10) A laminate of Comparative Example 10 was produced in the same manner as in Example 6, except that the aging treatment after drying of the coating layer was not carried out.

[0175] (Comparative Example 11) A laminate of Comparative Example 11 was produced in the same manner as in Example 6, except that the aging treatment after drying of the coating layer was carried out at 55° C. for 7 days.

[0176] Example 13 Example 13 was a laminate identical to that of Example 1, but subjected to high retort treatment at 135°C for 30 minutes.

[0177] Example 14 Example 14 was a laminate identical to that of Example 4, but subjected to high retort treatment at 135°C for 30 minutes.

[0178] Example 15 Example 15 was a laminate identical to that of Example 7, but subjected to high retort treatment at 135°C for 30 minutes.

[0179] Example 16 Example 16 was a laminate identical to that of Example 8, but subjected to high retort treatment at 135°C for 30 minutes.

[0180] Example 17 Example 17 was a laminate identical to that of Example 9, but subjected to high retort treatment at 135°C for 30 minutes.

[0181] Example 18 Example 18 was a laminate identical to that of Example 10, but subjected to high retort treatment at 135°C for 30 minutes.

[0182] (Comparative Example 5) Comparative Example 5 was a laminate identical to that of Comparative Example 1, but subjected to high retort treatment at 135°C for 30 minutes.

[0183] (Comparative Example 6) Comparative Example 6 was the same laminate as Comparative Example 3, but subjected to high retort treatment at 135°C for 30 minutes.

[0184] (Comparative Example 7) A barrier film was produced in the same manner as in Example 1, except that the drying temperature for the coating layer was set to 60°C. However, because the drying temperature was low, wrinkles occurred at the winding portion during the formation of the coating layer, and therefore a laminate was not produced.

[0185] (Comparative Example 8) A barrier film was produced in the same manner as in Example 1, except that the drying temperature for the coating layer was set to 80°C. However, because the drying temperature was low, wrinkles occurred at the winding section during the formation of the coating layer, and therefore a laminate was not produced.

[0186] [Table 1]

[0187] <Measurement of the composite elastic modulus and indentation hardness of the coating layer> The laminates of the Examples and Comparative Examples were subjected to heat sterilization treatment under the following conditions: retort treatment at 121°C for 30 minutes for Examples 1 to 12, Examples 19 to 21, Comparative Examples 1 to 4, and Comparative Examples 9 to 11; and high retort treatment at 135°C for 30 minutes for Examples 13 to 18 and Comparative Examples 5 and 6.

[0188] The composite elastic modulus (GPa) and indentation hardness (GPa) of the coating layer of the laminate after heat sterilization treatment were measured under the following conditions. The results are shown in Table 3 and Figures 3 and 4. "Ex. 1" and "Comp. 1" in Figures 3 and 4 mean "Example 1" and "Comparative Example 1," respectively. Measurement equipment: HYSITRON TI-950 Tribo Indenter Measurement point: From the cross-section side of the coating layer Measurement mode: Indentation Indenter: Cubecorner indenter, TI-0037 Measurement Profile 0→10sec:0→15μN 10→15sec: 15μN 15→25sec:15→0μN Number of data points: 200 points / sec

[0189] <Measurement of composite elastic modulus and indentation hardness before and after lamination and heat sterilization> For Examples 1 and 6, the composite elastic modulus (GPa) and indentation hardness (GPa) of the coating layer were measured under the above conditions for the barrier film alone, the laminate after dry lamination and before retort treatment, and the laminate after dry lamination and after retort treatment at 121°C for 30 minutes. All measurements were taken from the cross-sectional side of the coating layer. The results are shown in Table 2. From Table 2, it can be seen that the values ​​vary irregularly for the barrier film alone, the laminate before retort treatment, and the laminate after retort treatment. The reason for the change in values ​​is unknown, but is presumed to be due to the combination of the composition of the coating layer, the drying conditions, and the heat sterilization treatment conditions.

[0190] [Table 2]

[0191] <Oxygen permeability measurement> The oxygen permeability (cc / m) of the laminates after heat sterilization treatment in the examples and comparative examples 2 The oxygen permeability (OTR) was measured using an oxygen transmission rate measuring device (manufactured by Mocon, product name "OX-TRAN 2 / 20") at 23°C and 90% RH in accordance with JIS K 7126-2. The results are shown in Table 3.

[0192] [Table 3]

[0193] In addition, the laminates of Comparative Examples 7 and 8 were not subjected to further evaluation because wrinkles occurred at the wound portion during the formation of the coating layer due to the low drying temperature, and were therefore unsuitable from the viewpoint of processability.

[0194] From Table 3 and Figures 3 and 4, it can be seen that laminates with a composite elastic modulus of 5.0 GPa or more and 9.5 GPa or less and an indentation hardness of 0.9 GPa or more and 1.7 GPa or less have excellent oxygen barrier properties after retort treatment at 121°C for 30 minutes.

[0195] Furthermore, the barrier properties of the barrier films used in the laminates of Examples 1 to 18 were measured before and after 2% stretching using a tensile tester. As a result, the deterioration of the barrier properties before and after stretching (OTR after stretching - OTR before stretching) was 3 cc / m 2 ·day·atm or less, and it was confirmed that the deterioration of barrier properties due to stretching was suppressed. [Explanation of symbols]

[0196] 10 (first) biaxially oriented polypropylene substrate 20 Inorganic oxide vapor deposited film 30 Covering layer 40 Second biaxially oriented polypropylene substrate 50 sealant layer 61 First adhesive layer 62 Second adhesive layer 100, 200 laminate

Claims

1. A heat-sterilized laminate used for a packaging bag containing retort food or boiled food, The laminate comprises a biaxially oriented polypropylene substrate, a barrier film in which an inorganic oxide vapor-deposited film and a coating layer having barrier properties are laminated in this order, and a sealant layer; A laminate wherein the coating layer of the laminate has a composite elastic modulus and an indentation hardness, measured by a nanoindentation method from a cross section of the coating layer, of which the composite elastic modulus is 5.0 GPa or more and 9.5 GPa or less, and the indentation hardness is 0.9 GPa or more and 1.7 GPa or less.

2. The laminate according to claim 1 , wherein the composite elastic modulus is 6.0 GPa or more and 9.0 GPa or less, and the indentation hardness is 1.0 GPa or more and 1.5 GPa or less.

3. The laminate according to claim 1 or 2, wherein the heat sterilization treatment is a retort treatment.

4. The laminate according to claim 1 or 2, wherein the coating layer comprises a cured product of a resin composition containing an alkoxysilane and a hydroxyl group-containing water-soluble resin.

5. The laminate according to claim 1 or 2, wherein the surface of the coating layer of the barrier film is laminated to another film via an adhesive layer.

6. The packaging material after heat sterilization according to claim 1 or 2 has an oxygen permeability of 10.0 cc / m at 23°C and 90% RH according to JIS K 7126-2. ２ .day.atm or less.

7. The packaging material after heat sterilization according to claim 1 or 2 has an oxygen permeability of 5.0 cc / m at 23°C and 90% RH according to JIS K 7126-2. ２ .day.atm or less.

8. A packaging product comprising the laminate of claim 1 or 2.

9. Use of a heat-sterilized laminate for packaging retort food or boiled food, The laminate comprises a biaxially oriented polypropylene substrate, a barrier film in which an inorganic oxide vapor-deposited film and a coating layer having barrier properties are laminated in this order, and a sealant layer; The coating layer of the laminate has a composite elastic modulus and an indentation hardness measured by a nanoindentation method from a cross section of the coating layer, the composite elastic modulus being 5.0 GPa or more and 9.5 GPa or less, and the indentation hardness being 0.9 GPa or more and 1.7 GPa or less.

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