Packaging materials

Abstract

To provide a gas barrier laminate which is useful for achieving excellent recyclability and has excellent gas barrier property.SOLUTION: A packaging material includes a gas barrier laminate, a polypropylene-based sealant layer, and an adhesive layer provided between the gas barrier laminate and the polypropylene-based sealant layer. The gas barrier laminate includes a polypropylene-based base material layer, a first polyvinyl alcohol-based resin layer, a gas barrier layer, and a second polyvinyl alcohol-based resin layer, in this order. The thickness of the first polyvinyl alcohol-based resin layer is 0.4 to 2.0 μm, the gas barrier layer is a metal oxide layer having a thickness of 5 to 100 nm, and the thickness of the second polyvinyl alcohol-based resin layer is 0.1 to 1.0 μm. A mass ratio of the total of the polypropylene-based base material layer and the polypropylene-based sealant layer is 85 mass% or more based on the total mass of the packaging material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a gas barrier laminate and a packaging material using the same. [Background technology]

[0002] A laminate (flexible packaging material) is known that comprises a biaxially oriented PET (polyethylene terephthalate) film with excellent heat resistance and toughness as a base film, and a polyolefin film such as polyethylene or polypropylene as a sealant layer (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-178357 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, growing environmental awareness stemming from issues such as marine plastic waste has led to a demand for even greater efficiency in the sorting, collection, and recycling of plastic materials. This means that even in flexible packaging materials, where performance has traditionally been achieved by combining various dissimilar materials, there is now a growing need for monomaterial construction.

[0005] This disclosure provides a gas barrier laminate that is useful for achieving excellent recyclability of packaging materials and has excellent gas barrier properties. This disclosure also provides a packaging material using this gas barrier laminate. [Means for solving the problem]

[0006] A gas barrier laminate relating to one aspect of this disclosure has a laminated structure comprising a polypropylene substrate layer, a first polyvinyl alcohol resin layer, and a metal oxide layer in this order, wherein the mass per unit area of ​​the first polyvinyl alcohol resin layer is 0.5 to 2.5 g / m². 2 This gas barrier laminate allows for excellent gas barrier properties to be achieved even if the surface of the polypropylene substrate layer is not necessarily highly smooth, because a first polyvinyl alcohol-based resin layer is interposed between the polypropylene substrate layer and the metal oxide layer. From the viewpoint of achieving even better gas barrier properties, the surface roughness Sa of the first polyvinyl alcohol-based resin layer is preferably 0.2 μm or less, and more preferably 0.1 μm or less.

[0007] The inventors have developed a gas barrier laminate that can be used in combination with a sealant layer to constitute a packaging material, and which can realize a monomaterial packaging material with excellent recyclability. In order to realize a monomaterial packaging material that includes unoriented polypropylene film (CPP film), which is widely used as a sealant film, it is necessary to use a polypropylene film (PP film) as the base layer of the gas barrier laminate. However, considering the heat resistance of the packaging material, not just any type of PP film will do, and it is useful to use a propylene monopolymer film that has superior heat resistance compared to other PP films. Packaging materials may be subjected to heat sterilization treatments such as boiling or retorting while containing food, and heat resistance may be required.

[0008] However, according to our evaluation tests, propylene monopolymer films have the drawback of their surface tending to form a vein-like structure, and even when a metal oxide layer (gas barrier layer) is directly formed on the surface of a propylene monopolymer film, sufficient barrier properties cannot be achieved. Therefore, by interposing a polyvinyl alcohol-based resin layer between the propylene monopolymer film as the base layer and the metal oxide layer, we have developed a gas barrier laminate that is useful for obtaining a monomaterial packaging material with excellent gas barrier properties.

[0009] From the viewpoint of achieving excellent heat resistance of the gas barrier laminate, as described above, the polypropylene substrate layer is preferably a propylene monopolymer layer.

[0010] The gas barrier laminate according to this disclosure may further comprise a second polyvinyl alcohol-based resin layer sandwiching a metal oxide layer together with the first polyvinyl alcohol-based resin layer. By adopting a configuration in which the metal oxide layer is sandwiched between the first and second polyvinyl alcohol-based resin layers, even better gas barrier properties can be achieved. From the viewpoint of adhesion to the metal oxide layer and maintenance of gas barrier properties, the second polyvinyl alcohol-based resin layer may contain a silane compound. The mass ratio of the silane compound to the mass of the second polyvinyl alcohol-based resin layer is, for example, 0.05 to 0.95.

[0011] A packaging material relating to one aspect of this disclosure comprises the gas barrier laminate and a polypropylene-based sealant layer provided on the surface of the gas barrier laminate, wherein the total mass ratio of the polypropylene-based base layer and the polypropylene-based sealant layer is 85% by mass or more, and may be 90% by mass or more or 95% by mass or more depending on the thickness of the polypropylene-based sealant layer. With this packaging material, monomaterial packaging can be achieved by using the gas barrier laminate and the polypropylene-based sealant layer in combination. In this disclosure, monomaterial packaging material means packaging material in which the mass ratio of a specific material (polypropylene-based material) is 85% by mass or more (preferably 90% by mass or more or 95% by mass or more). [Effects of the Invention]

[0012] This disclosure provides a gas barrier laminate that is useful for achieving excellent recyclability of packaging materials and has excellent gas barrier properties. This disclosure also provides a packaging material using this gas barrier laminate. [Brief explanation of the drawing]

[0013] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an embodiment of a gas barrier laminate according to the present disclosure. [Figure 2] FIGS. 2(a) and 2(b) are cross-sectional views schematically showing modified examples of the gas barrier laminate shown in FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a packaging material using the gas barrier laminate shown in FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view schematically showing another embodiment of the gas barrier laminate according to the present disclosure. [Figure 5] FIG. 5 is a cross-sectional view schematically showing another embodiment of the packaging material according to the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are not limited to the ratios shown.

[0015] <Gas barrier laminate> FIG. 1 is a schematic cross-sectional view showing the gas barrier laminate according to the present embodiment. The gas barrier laminate 10 shown in FIG. 1 has a laminated structure including a base material layer 1, a first polyvinyl alcohol-based resin layer 3a, a metal oxide layer 5, and a second polyvinyl alcohol-based resin layer 3b in this order.

[0016] (Base material layer) The base material layer 1 is made of a polypropylene-based resin. Examples of the polypropylene-based resin include a homopolymer of propylene, a random copolymer, and a block copolymer. When heat resistance is required for the base material layer 1, the polypropylene-based resin is preferably a homopolymer of propylene. However, as described above, a homopolymer film of propylene has a drawback that its surface tends to be veined. The surface roughness Sa of the veined film surface is, for example, more than 0.2 μm, and may be 0.21 to 0.5 μm.

[0017] Meanwhile, in the present disclosure, the surface roughness Sa of each layer means the value measured under the following conditions using a three-dimensional non-contact surface shape measurement system (Vertscan R3300h Lite, manufactured by Hishikawa System Co., Ltd.). · Measurement mode: Phase · Scan speed: 4 μm / sec · Scan range: 10 / -20 μm · Number of scans: 1 time · Interpolation: Complete interpolation · Surface correction: Fourth order · Objective lens: 1x · Magnification lens: 5x

[0018] By using a homopolymer film of propylene as the base material layer 1, the gas barrier laminate 10 can be made resistant to heat sterilization treatments such as boiling treatment and retort treatment. The temperature of the boiling treatment is about 60 to 100°C, and the temperature of the retort treatment is about 105 to 140°C.

[0019] The film constituting the base material layer 1 may be a stretched film or an unstretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the film constituting the base material layer 1 may be a stretched film. The stretching method is not particularly limited, and any method may be used as long as a film with stable dimensions, such as stretching by inflation, uniaxial stretching, or biaxial stretching, can be supplied.

[0020] The thickness of the base layer 1 is not particularly limited, but from the viewpoint of obtaining excellent impact resistance and excellent gas barrier properties, it can be 10 to 100 μm, and may be 15 to 30 μm. The film constituting the base layer 1 may be subjected to various pretreatments such as corona treatment, plasma treatment, and flame treatment on its laminated surface F1, to the extent that it does not impair the barrier performance, or a coating layer 1a (adhesion layer) may be provided to improve adhesion (see Figure 2(a)). In addition, a copolymer layer 1b may be provided on the outer surface F2 of the base layer 1. A specific example of the resin constituting the polymer layer 1c is a copolymer of propylene and another monomer. The other monomer is, for example, at least one of ethylene and butene.

[0021] The polypropylene resin constituting the base layer 1 may contain additives such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants as needed. From the viewpoint of achieving a high degree of monomateriality for the gas barrier laminate 10 and the packaging material 50 using the same, the mass ratio of the polypropylene resin in the base layer 1 is preferably 90% by mass or more, and more preferably 95% by mass or more.

[0022] (First polyvinyl alcohol-based resin layer) The resin constituting the first polyvinyl alcohol-based resin layer 3a can be any resin having vinyl alcohol units formed by saponification of vinyl ester units, such as polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH). EVOH can be suitably used from the viewpoint of heat resistance and gas barrier properties.

[0023] Examples of PVA include resins obtained by polymerizing vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versaticate individually, and then saponifying them.

[0024] PVA may be copolymerized or post-modified modified PVA. Copolymerized modified PVA can be obtained, for example, by copolymerizing a vinyl ester with an unsaturated monomer copolymerizable with the vinyl ester, followed by saponification. Post-modified PVA can be obtained by copolymerizing the PVA obtained by saponifying a vinyl ester with an unsaturated monomer in the presence of a polymerization catalyst. The amount of modification in modified PVA can be less than 50 mol% from the viewpoint of exhibiting sufficient gas barrier properties, and can be 10 mol% or more from the viewpoint of obtaining the effect of modification.

[0025] Examples of the unsaturated monomers mentioned above 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-pentin-1-ol, and 5-hexen-1-ol; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid; nitriles such as acrylonitrile and methacrylonitrile; amides such as diacetone acrylamide, acrylamide, and methacrylamide; and Examples include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid; vinyl compounds such as alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxyquinolane, glycerol monoallyl ether, and 3,4-diacetoxy-1-butene; and vinylidene chloride, 1,4-diacetoxy-2-butene, vinylene carbonate, polyoxypropylene, and polyoxypropylene vinylamine. From the viewpoint of gas barrier properties, the unsaturated monomer can be an olefin, and ethylene may be particularly suitable.

[0026] Examples of polymerization catalysts include radical polymerization catalysts such as azobisisobutyronitrile, benzoyl peroxide, and lauryl peroxide. The polymerization method is not particularly limited, and bulk polymerization, emulsion polymerization, solvent polymerization, etc., can be employed.

[0027] The degree of polymerization of PVA is preferably 300 to 3000. If the degree of polymerization is less than 300, the barrier properties tend to decrease, and if it exceeds 3000, the viscosity becomes too high and the coating suitability tends to decrease. The degree of saponification of PVA is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more. The degree of saponification of PVA may also be 100 mol% or less, or 99.9 mol% or less. The degree of polymerization and saponification of PVA can be measured in accordance with the method described in JIS K 6726 (1994).

[0028] EVOH is generally obtained by saponifying copolymers of ethylene with vinyl acid esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate.

[0029] The degree of polymerization of EVOH is preferably 300 to 3000. If the degree of polymerization is less than 300, the barrier properties tend to decrease, and if it exceeds 3000, the viscosity becomes too high and the coating suitability tends to decrease. The degree of saponification of the vinyl ester component of EVOH is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more. The degree of saponification of EVOH may also be 100 mol% or less, or 99.9 mol% or less. The degree of saponification of EVOH is determined by nuclear magnetic resonance (1H-NMR) measurement, 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.

[0030] The ethylene unit content of EVOH is, for example, 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more. Furthermore, 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. An ethylene unit content of 10 mol% or more allows for good gas barrier properties and dimensional stability under high humidity conditions. On the other hand, an ethylene unit content of 65 mol% or less enhances gas barrier properties. The ethylene unit content of EVOH can be determined by NMR spectroscopy.

[0031] Saponification can be carried out with alkali or acid, but alkali is preferred from the standpoint of saponification rate. Examples of alkalis include alkali metal oxides such as sodium hydroxide and potassium hydroxide, and alkali metal alkoxides such as sodium ethylate, potassium ethylate, and lithium methylate.

[0032] The mass per unit area of ​​the first polyvinyl alcohol-based resin layer 3a is 0.5 to 2.5 g / m². 2 Therefore, 0.5~2.0 g / m 2 Or 0.5~1.5g / m 2 This is acceptable. This mass is 0.5 g / m 2 As described above, even if the smoothness of the laminated surface F1 of the base layer 1 is insufficient, the surface F3 of the first polyvinyl alcohol-based resin layer 3a can be formed sufficiently smooth, and a metal oxide layer 5 with excellent gas barrier properties can be formed on the surface F3. On the other hand, if this mass is 2.5 g / m 2 The following is advantageous in terms of realizing a monomaterial of polypropylene resin and reducing material costs. The thickness of the first polyvinyl alcohol-based resin layer 3a is, for example, 0.4 to 2.0 μm, and may be 0.4 to 1.7 μm or 0.4 to 1.3 μm, from the same viewpoint as the mass per unit area described above. The thickness of the resin layer can be calculated based on the mass per unit area of ​​the resin layer and the density of the resin.

[0033] The surface roughness Sa of the surface F3 of the first polyvinyl alcohol-based resin layer 3a is, for example, 0.2 μm or less, and may be 0.01 to 0.1 μm or 0.02 to 0.1 μm. When the surface roughness Sa of the surface F3 is 0.2 μm or less, a metal oxide layer 5 with excellent gas barrier properties can be formed on the surface F3. On the other hand, when the surface roughness Sa of the surface F3 is 0.01 μm or more, the adhesion between the first polyvinyl alcohol-based resin layer 3a and the metal oxide layer 5 can be improved by the anchoring effect compared to the case where the surface roughness is less than 0.01 μm.

[0034] (Metal oxide layer) The metal oxide layer 5 has gas barrier properties. Examples of metal oxides include silicon oxide (SiOx) and aluminum oxide (AlOx). By using these metal oxides, high gas barrier properties can be obtained while keeping the thickness low. From the viewpoint of excellent tensile stretchability during processing, the metal oxide layer 5 may be composed of silicon oxide.

[0035] The thickness of the metal oxide layer 5 is, for example, 5 to 100 nm, and may be 10 to 50 nm or 20 to 40 nm. If the thickness of the metal oxide layer 5 is 5 nm or more, sufficient gas barrier properties can be obtained, while if it is 100 nm or less, the occurrence of cracks due to deformation caused by internal stress in the metal oxide layer 5 is suppressed, and excellent gas barrier properties can be maintained.

[0036] (Second polyvinyl alcohol-based resin layer) Regarding the polyvinyl alcohol-based resin constituting the second polyvinyl alcohol-based resin layer 3b, you can refer to the description given for the first polyvinyl alcohol-based resin layer 3a.

[0037] The second polyvinyl alcohol-based resin layer 3b may contain a silane compound. Examples of silane compounds include tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, reactive group-containing trialkoxysilanes such as glycidoxypropyltrimethoxysilane and acryloxypropyltrimethoxysilane, and silazanes such as hexamethyldisilazane. As the silane compound, compounds commonly used as silane coupling agents or polysiloxane compounds having siloxane bonds may also be used.

[0038] The mass ratio of the silane compound to the mass of the second polyvinyl alcohol-based resin layer 3b is, for example, 0.05 to 0.95, and may be 0.1 to 0.8 or 0.3 to 0.7, from the viewpoint of adhesion to the metal oxide layer and maintaining gas barrier properties.

[0039] The thickness of the second polyvinyl alcohol-based resin layer 3b is, for example, 0.1 to 1.0 μm, and may be 0.1 to 0.8 μm or 0.2 to 0.7 μm. A thickness of 0.1 μm or more allows for excellent gas barrier properties to be achieved, and these gas barrier properties are sufficiently maintained over a long period of time. On the other hand, a thickness of 1.0 μm or less is advantageous in terms of realizing a polypropylene-based resin monomaterial and reducing material costs.

[0040] <Method for manufacturing a gas barrier laminate> The gas barrier laminate 10 is manufactured, for example, by the steps of forming a first polyvinyl alcohol-based resin layer 3a on a base layer 1, forming a metal oxide layer 5 on the first polyvinyl alcohol-based resin layer 3a, and forming a second polyvinyl alcohol-based resin layer 3b on the metal oxide layer 5.

[0041] (Step of forming the first polyvinyl alcohol-based resin layer) In this process, a coating solution containing a polyvinyl alcohol-based resin and a liquid medium can be used. This coating solution can be obtained, for example, by dissolving a powder of a polyvinyl alcohol-based resin obtained by synthesis in a liquid medium. Examples of liquid media include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used individually or in combination of two or more. From the viewpoint of reducing environmental impact, water can be used as the liquid medium. In this case, the coating solution can be obtained by dissolving the powder of the polyvinyl alcohol-based resin in water at a high temperature (e.g., 80°C).

[0042] The content of polyvinyl alcohol-based resin (solids) in the coating solution can be 3 to 20% by mass from the viewpoint of maintaining good coatability. The coating solution may contain additives such as isocyanates and polyethyleneimines to improve adhesion. The coating solution may also contain additives such as preservatives, plasticizers (alcohol, etc.), and surfactants.

[0043] The coating solution can be applied to the substrate layer 1 by any suitable method. For example, the coating solution can be applied by a wet deposition method such as a gravure coater, dip coater, reverse coater, wire bar coater, or die coater. The application temperature and drying temperature of the coating solution are not particularly limited and can be, for example, 50°C or higher.

[0044] The first polyvinyl alcohol-based resin layer 3a may be formed on the substrate layer 1 by an extrusion method. In this case, multilayer extrusion using a T-die can be employed. Examples of adhesives that can be used during extrusion include two-component curing polyurethane adhesives, which consist of a main component such as polyester polyol, polyether polyol, or acrylic polyol, and a difunctional or more aromatic or aliphatic isocyanate compound as a curing agent. An adhesive layer may be pre-formed on the substrate layer 1 by coating the above adhesive components onto the substrate layer 1 and then drying it. When using a polyurethane adhesive, after coating, aging at 40°C for 4 days or more allows the reaction between the hydroxyl groups of the main component and the isocyanate groups of the curing agent to proceed, enabling strong adhesion. The thickness of the adhesive layer can be 1 to 50 μm, or 3 to 20 μm, from the viewpoint of adhesion, conformability, and processability.

[0045] (Process for forming a metal oxide layer) The metal oxide layer 5 can be formed, for example, by vacuum deposition. For vacuum deposition, physical vapor deposition or chemical vapor deposition can be used. Examples of physical vapor deposition include vacuum evaporation, sputtering, and ion plating, but are not limited to these. Examples of chemical vapor deposition include thermal CVD, plasma CVD, and photoCVD, but are not limited to these.

[0046] In the vacuum deposition methods described above, resistance heating vacuum deposition, EB (Electron Beam) heating vacuum deposition, induction heating vacuum deposition, sputtering, reactive sputtering, dual magnetron sputtering, and plasma chemical vapor deposition (PECVD) are particularly preferred. However, considering productivity, vacuum deposition is currently the most superior method. For the heating means in vacuum deposition, it is preferable to use one of the following methods: electron beam heating, resistance heating, or induction heating.

[0047] In the sputtering method, a negative potential gradient is generated on the target, which is the cathode, and Ar + Ions receive electrical energy and collide with the target. Here, even if a plasma is generated, sputtering cannot be performed unless a negative self-bias potential is produced. Therefore, MW (Microwave) plasma is unsuitable for sputtering because it does not generate self-bias. However, in the PECVD method, the chemical reaction and deposition process proceed using gas-phase reactions in the plasma, and film formation is possible even without self-bias, thus allowing the use of MW plasma.

[0048] (Step to form a second polyvinyl alcohol-based resin layer) This process can use the same coating solution as the process for forming the first polyvinyl alcohol-based resin layer 3a. Regarding the coating solution, refer to the description in the section on the process for forming the first polyvinyl alcohol-based resin layer 3a.

[0049] The coating solution for forming the second polyvinyl alcohol-based resin layer 3b may contain a silane compound. The amount of silane compound in the coating solution should be adjusted so that the second polyvinyl alcohol-based resin layer 3b contains a desired amount of silane compound. If the coating solution contains a silane compound, the coating solution may further contain an acid catalyst, an alkali catalyst, a photoinitiator, etc.

[0050] <Packaging material> The packaging material 50 shown in Figure 3 comprises a gas barrier laminate 10 and a polypropylene-based sealant layer 20 provided on the inner surface 10F of the gas barrier laminate 10. Based on the total mass of the packaging material 50, the total mass ratio of the base layer 1 and the polypropylene-based sealant layer 20 is 85% by mass or more (preferably 90% by mass or more, or 95% by mass or more), and the packaging material 50 is a monomaterial.

[0051] The gas barrier laminate 10 can be bonded to the polypropylene sealant layer 20 using, for example, an adhesive (not shown). Examples of adhesives that can be used include those containing linear low-density polyethylene (LLDPE), polyurethane, polypropylene, ethylene-unsaturated ester copolymer resin, or polyester copolymer resin. The thickness of the adhesive layer can be, for example, about 1 to 5 μm. A specific example of the polypropylene sealant layer 20 is, for example, an unstretched polypropylene film (CPP film). The thickness of the polypropylene sealant layer 20 is, for example, 10 to 100 μm.

[0052] Although embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above embodiments. For example, in the above embodiments, a gas barrier laminate 10 comprising a second polyvinyl alcohol-based resin layer 3b was exemplified, but depending on the application of the gas barrier laminate, it may not be necessary to include the second polyvinyl alcohol-based resin layer 3b (see Figure 4).

[0053] In the above embodiment, a packaging material 50 is exemplified in which a polypropylene-based sealant layer 20 is laminated to the barrier-side surface of the gas barrier laminate 10. However, the polypropylene-based sealant layer 20 may also be laminated to the substrate layer 1 side surface of the gas barrier laminate 10 (see Figure 5). The packaging material 60 shown in Figure 5 has a configuration in which the barrier side of the gas barrier laminate 10 faces a general OPP film 8 (printing substrate, etc.), and the polypropylene-based sealant layer 20 is laminated to the substrate layer 1 side of the gas barrier laminate 10. [Examples]

[0054] The present disclosure will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0055] The following materials were prepared for the examples and comparative examples. (base material layer) • Polypropylene resin: Propylene monopolymer (monoPP) (Polyvinyl alcohol-based resin layer) • EVOH: EVAL L171B (manufactured by Kuraray Co., Ltd.) • PVA: Poval 60-98 (manufactured by Kuraray Co., Ltd.) • TEOS: KBE04 (manufactured by Shin-Etsu Chemical Co., Ltd.) (Sealant layer) • Polypropylene-based sealant film: Trefan ZK207#60 (CPP, 60μm thickness, Toray Industries, Inc.)

[0056] (Example 1) An OPP film (base layer) was fabricated using the above monoPP, and at the same time, an EVOH layer (first polyvinyl alcohol-based resin layer) was formed on the surface of the OPP film by extrusion. The mass per unit area of ​​the EVOH layer was 0.97 g / m². 2 The EVOH layer had a thickness of 0.8 μm and a surface roughness Sa of 0.08 μm. When the EVOH layer was peeled off and the surface roughness Sa of the OPP film was measured, the value was 0.23 μm. The surface roughness Sa was measured using a three-dimensional non-contact surface shape measurement system (Vertscan R3300h Lite, manufactured by Ryoka Systems Co., Ltd.) under the conditions described above.

[0057] An electron beam-heated vacuum deposition apparatus was used to form an SiOx film (metal oxide layer) on the surface of an EVOH layer. Specifically, the SiO deposition material was evaporated by electron beam heating to form an SiOx film (thickness 50 nm). Next, a layer containing PVA and TEOS (a second polyvinyl alcohol-based resin layer) was formed on the surface of the SiOx film. Specifically, TEOS, methanol, and hydrochloric acid (0.1 N) were mixed in a mass ratio of 18 / 10 / 72 to obtain a hydrolyzed solution (TEOS-containing solution). A coating solution was prepared by mixing a 5% aqueous solution of PVA and the TEOS-containing solution so that the mass ratio of PVA to TEOS was 50 / 50. After applying this coating solution to the surface of the SiOx film, a layer containing PVA and TEOS (PVA / TEOS = 50 / 50) was formed by drying.

[0058] A packaging material was prepared by bonding a polypropylene-based sealant film to the inner surface of the gas barrier laminate obtained through the above process using an adhesive (A-525, manufactured by Mitsui Chemicals, Inc.). The mass ratio of polypropylene-based resin in the packaging material was 94% by mass. The oxygen permeability of this packaging material was measured. The oxygen permeability was measured using OX-TRAN2 / 20 (manufactured by MOCON) under conditions of 30°C and 70% relative humidity in accordance with JIS K7126-2. The oxygen permeability of the packaging material after boiling was also measured in the same manner. That is, a three-side seal pouch was prepared using the packaging material, and tap water was sealed inside. After boiling this sealed body at a temperature of 90°C for 30 minutes, the oxygen permeability of the packaging material was measured. The results are shown in Table 1.

[0059] (Example 2) Gas barrier laminates and packaging materials were fabricated in the same manner as in Example 1, except that an AlOx film (50 nm) was formed as the metal oxide layer instead of an SiOx film (50 nm). Each was then evaluated. The AlOx film was formed by evaporating an aluminum ingot by electron beam heating and introducing oxygen. The results are shown in Table 1.

[0060] (Example 3) Instead of forming a layer with a mass ratio of PVA to TEOS of 50 / 50, a gas barrier laminate and a packaging material were produced in the same manner as in Example 1 except that a layer with a mass ratio of PVA to TEOS of 97 / 3 was formed, and each evaluation was performed. The results are shown in Table 1.

[0061] (Comparative Example 1) A gas barrier laminate and a packaging material were produced in the same manner as in Example 1 except that a SiOx film (50 nm) was directly formed on the surface of an OPP film without forming an EVOH layer (the first polyvinyl alcohol-based resin layer), and each evaluation was performed. The results are shown in Table 2.

[0062] (Comparative Example 2) As the first polyvinyl alcohol-based resin layer, instead of forming an EVOH layer (mass per unit area: 0.97 g / m 2 , thickness: 0.8 μm), a PVA layer (mass per unit area: 2.8 g / m 2 , thickness: 2.3 μm) was formed, and a gas barrier laminate and a packaging material were produced in the same manner as in Example 1, and each evaluation was performed. The results are shown in Table 2.

[0063] (Comparative Example 3) As the first polyvinyl alcohol-based resin layer, instead of forming an EVOH layer (mass per unit area: 0.97 g / m 2 , thickness: 0.8 μm), an EVOH layer (mass per unit area: 0.40 g / m 2 , thickness: 0.33 μm) was formed, and a gas barrier laminate and a packaging material were produced in the same manner as in Example 1, and each evaluation was performed. The results are shown in Table 2.

[0064] [Table 1]

[0065] [Table 2] [Explanation of Symbols]

[0066] 1…Base layer, 1a…Coating layer (adhesion layer), 1b…Copolymer layer, 3a…First polyvinyl alcohol-based resin layer, 3b…Second polyvinyl alcohol-based resin layer, 5…Metal oxide layer, 10…Gas barrier laminate, 10F…Inner surface, 20…Polypropylene sealant layer, 50,60…Packaging material, F1…Laminated surface of polypropylene base layer, F2…Outer surface of polypropylene base layer, F3…Surface of first polyvinyl alcohol-based resin layer

Claims

1. Gas barrier laminate and Polypropylene sealant layer, An adhesive layer is provided between the gas barrier laminate and the polypropylene-based sealant layer, and the gas barrier laminate and the polypropylene-based sealant layer are bonded together. A packaging material that has the following features: The aforementioned gas barrier laminate, Polypropylene substrate layer, A first polyvinyl alcohol-based resin layer, gas barrier layer, A second polyvinyl alcohol-based resin layer, The polypropylene-based substrate layer, the first polyvinyl alcohol-based resin layer, the gas barrier layer, and the second polyvinyl alcohol-based resin layer are provided in this order and the laminated structure consists of the polypropylene-based substrate layer, the first polyvinyl alcohol-based resin layer, the gas barrier layer, and the second polyvinyl alcohol-based resin layer. The thickness of the first polyvinyl alcohol-based resin layer is 0.4 to 2.0 μm. The aforementioned gas barrier layer is a metal oxide layer with a thickness of 5 to 100 nm. The thickness of the second polyvinyl alcohol-based resin layer is 0.1 to 1.0 μm. Based on the total mass of the packaging material, the combined mass ratio of the polypropylene-based base layer and the polypropylene-based sealant layer is 85% by mass or more. The resin constituting the first polyvinyl alcohol-based resin layer is an ethylene-vinyl alcohol copolymer. The second polyvinyl alcohol-based resin layer contains a silane compound. A packaging material in which the first polyvinyl alcohol-based resin layer is formed by an extrusion method.

2. Gas barrier laminate and Polypropylene sealant layer, An adhesive layer is provided between the gas barrier laminate and the polypropylene-based sealant layer, and the gas barrier laminate and the polypropylene-based sealant layer are bonded together. A packaging material that has the following features: The aforementioned gas barrier laminate, Polypropylene substrate layer, A first polyvinyl alcohol-based resin layer, gas barrier layer, A second polyvinyl alcohol-based resin layer, The polypropylene-based substrate layer, the first polyvinyl alcohol-based resin layer, the gas barrier layer, and the second polyvinyl alcohol-based resin layer are provided in this order and the laminated structure consists of the polypropylene-based substrate layer, the first polyvinyl alcohol-based resin layer, the gas barrier layer, and the second polyvinyl alcohol-based resin layer. The thickness of the first polyvinyl alcohol-based resin layer is 0.4 to 2.0 μm. The aforementioned gas barrier layer is a metal oxide layer with a thickness of 5 to 100 nm. The thickness of the second polyvinyl alcohol-based resin layer is 0.1 to 1.0 μm. Based on the total mass of the packaging material, the combined mass ratio of the polypropylene-based base layer and the polypropylene-based sealant layer is 85% by mass or more. The resin constituting the first polyvinyl alcohol-based resin layer is polyvinyl alcohol. The second polyvinyl alcohol-based resin layer contains a silane compound. A packaging material wherein the surface roughness Sa of the first polyvinyl alcohol-based resin layer on the side in contact with the gas barrier layer is 0.2 μm or less.

3. The packaging material according to claim 1, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 10 to 65 mol%.

4. The packaging material according to any one of claims 1 to 3, wherein the metal oxide layer contains silicon oxide.

5. The packaging material according to claim 1 or 3, wherein the surface roughness Sa of the first polyvinyl alcohol-based resin layer on the side in contact with the gas barrier layer is 0.2 μm or less.

6. The packaging material according to any one of claims 1 to 4, wherein the surface roughness Sa of the first polyvinyl alcohol-based resin layer on the side in contact with the gas barrier layer is 0.1 μm or less.

7. The packaging material according to any one of claims 1 to 6, wherein the polypropylene-based substrate layer is a propylene monopolymer layer.

8. The packaging material according to any one of claims 1 to 7, wherein the mass ratio of the silane compound to the mass of the second polyvinyl alcohol-based resin layer is 0.05 to 0.

95.

9. On the surface of the polypropylene substrate layer opposite to the side on which the first polyvinyl alcohol resin layer is provided, a copolymer layer of propylene and other monomers is further provided. The packaging material according to any one of claims 1 to 8, wherein the other monomer is at least one of ethylene and butene.

10. The packaging material according to any one of claims 1 to 9, further comprising a printing substrate, wherein the gas barrier laminate is disposed between the printing substrate and the polypropylene sealant layer.

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