Easy-to-tear laminate having barrier properties, packaging material and packaging bag

Abstract

To provide a laminate that has easy tearability, and strength and barrier properties applicable to a packaging material; a packaging material; and a packaging bag including the same.SOLUTION: An easy-to-tear laminate 20 having barrier properties includes at least a substrate layer 10 and an inorganic vapor deposition layer 5, the substrate layer 10 including polyethylene and a cyclic olefinic resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an easy-tear laminate having barrier properties, a packaging material, and a packaging bag. [Background technology]

[0002] In recent years, with the growing demand for the creation of a recycling-oriented society, attempts have been made to recycle and reuse packaging materials. Packaging materials that primarily use the same type of plastic are highly suitable for mechanical recycling, in which used packaging materials are collected, remelted, and reused as plastic.

[0003] Patent Document 1 proposes a laminate in which aluminum oxide is vapor-deposited onto a stretched polyethylene film, and a heat-sealable layer made of polyethylene is laminated thereon.

[0004] Furthermore, as an example of a packaging material made primarily of polyethylene that can be opened without using tools such as scissors, Patent Document 2 proposes a packaging material having an intermediate layer made of a blend resin of a cyclic olefin resin and a linear low-density polyethylene resin.

[0005] Furthermore, Patent Document 3 proposes providing a polyurethane layer on a packaging bag made of polyolefin to impart tearability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-171861 [Patent Document 2] Patent No. 5262134 [Patent Document 3] Special Publication No. 2020-535034 Summary of the Invention [Problem to be solved by the invention]

[0007] The stretched polyethylene described in Patent Document 1 has transparency and tearability compared to unstretched polyethylene. Providing a vapor-deposited layer of aluminum oxide, silicon oxide, or the like on the surface of a substrate is an effective technique for imparting barrier properties to gases such as oxygen and water vapor. However, as a result of studies by the present inventors, it has become clear that when vapor-deposited on a stretched polyethylene substrate, when the polyethylene substrate is made into a packaging bag and subjected to an impact such as being dropped, the vapor-deposited layer separates from the stretched polyethylene substrate, and the packaging bag does not have sufficient strength.

[0008] On the other hand, the density is 0.925 g / cm 3 When a vapor-deposited layer is provided on the unstretched polyethylene of the above-mentioned high-density polyethylene and medium-density polyethylene, although barrier properties and sufficient strength for a packaging bag are obtained, good tearability is not obtained, and there is a problem that it is difficult to open.

[0009] Furthermore, when a linear low-density polyethylene film described in Patent Document 2 was used as a substrate and a vapor-deposited layer of inorganic oxide was provided, good tearability was obtained, but cracks occurred in the vapor-deposited layer due to elongation of the substrate film, and gas barrier properties could not be obtained.

[0010] Furthermore, when a polyurethane layer is provided as a coating layer on the outer surface of the packaging bag as proposed in Patent Document 3, not only does it require an additional step of coating the outer surface, but it may also fall off due to friction during the filling and transportation steps, which could prevent the desired effect from being achieved.

[0011] As a method for solving the above problems, the present invention aims to provide a laminate, a packaging material, and a packaging bag using the same, which have tearability and strength and barrier properties suitable for use as packaging materials, by forming an inorganic vapor deposition layer on a substrate made of unstretched film made of high-density polyethylene with added cyclic olefin and medium-density polyethylene. [Means for solving the problem]

[0012] In order to solve the above problems, the first aspect of the present invention is In a laminate comprising at least a substrate layer and an inorganic vapor deposition layer, The easily tearable laminate having barrier properties is characterized in that the base layer is made of polyethylene and a cyclic olefin resin.

[0013] Moreover, a second aspect of the present invention is The density of the polyethylene forming the base layer is 0.925 g / cm 3 The easily tearable laminate having barrier properties according to claim 1 is characterized by the above.

[0014] Moreover, a third aspect of the present invention is 3. The easily tearable laminate having barrier properties according to claim 1 or 2, wherein the inorganic vapor deposition layer is made of a metal oxide.

[0015] Moreover, a fourth aspect of the present invention is A packaging material is characterized in that the easily tearable laminate having barrier properties according to any one of claims 1 to 3 is further laminated with heat-sealable polyethylene.

[0016] Moreover, a fifth aspect of the present invention is Density 0.925g / cm 3 The packaging material according to claim 4 is characterized in that a printed layer is provided on the stretched film made of the above polyethylene, the surface of this printed layer is laminated with an easy-tear laminate having barrier properties according to any one of claims 1 to 3, and further a heat-sealable polyethylene is laminated on the opposite surface of the easy-tear laminate having barrier properties.

[0017] Moreover, a sixth aspect of the present invention is 6. The packaging material according to claim 4 or 5, wherein the polyethylene content is 90% by weight or more.

[0018] Moreover, a seventh aspect of the present invention is A packaging bag using the packaging material according to any one of claims 4 to 6. [Effects of the Invention]

[0019] By using the above-mentioned means to provide an inorganic vapor deposition layer on a substrate made of high-density polyethylene with added cyclic olefin and unstretched film made of medium-density polyethylene, it is possible to provide a laminate, packaging material, and packaging bag using the same that are tearable and have strength and barrier properties suitable for use as packaging materials. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a packaging material according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present embodiment will be described with reference to the drawings, in which: Fig. 1 is a schematic cross-sectional view of a packaging material 30 used in one example of the present embodiment. <Base material layer> The base layer 1 has a density of 0.925 g / cm 3 It is made of high density polyethylene (HDPE) and medium density polyethylene (MDPE) with added cyclic olefin resin (COC). The cyclic olefin resin forms an island-sea structure with the medium density polyethylene. When torn, the tear travels along the cyclic olefin resin distributed like islands, making it easy to tear.

[0022] Polyethylenes with different densities and branching can be obtained by appropriately selecting a polymerization method, for example, using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst, and carrying out the polymerization in one or more stages using any of gas phase polymerization, slurry polymerization, solution polymerization, and high-pressure ionic polymerization.

[0023] The single-site catalyst is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene transition metal compound or a non-metallocene transition metal compound with an activating co-catalyst. Single-site catalysts are preferred because they have a more uniform active site structure than multi-site catalysts and can polymerize polymers with high molecular weights and highly uniform structures. As the single-site catalyst, it is particularly preferable to use a metallocene catalyst. The metallocene catalyst is a catalyst containing the following catalytic components: a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, and optionally an organometallic compound and a support.

[0024] In the above-mentioned transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton may be a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. The substituted cyclopentadienyl group has at least one substituent selected from hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl-substituted alkyl groups, silyl-substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, haloalkyl groups, and halosilyl groups. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may be bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenated product thereof. The rings formed by bonding the substituents to each other may further have substituents.

[0025] In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the transition metal can be zirconium, titanium, hafnium, etc., with zirconium and hafnium being particularly preferred. The transition metal compound typically contains two ligands having a cyclopentadienyl skeleton, and the cyclopentadienyl ligands are preferably bonded to each other via a bridging group. Examples of the bridging group include alkylene groups having 1 to 4 carbon atoms, silylene groups, substituted silylene groups such as dialkylsilylene groups and diarylsilylene groups, and substituted germylene groups such as dialkylgermylene groups and diarylgermylene groups. Substituted silylene groups are preferred. The above-mentioned transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component, either singly or in combination.

[0026] The co-catalyst refers to a catalyst that can effectively use the above-mentioned transition metal compound of Group IV of the periodic table as a polymerization catalyst or that can balance the ionic charge in a catalytically activated state. Examples of the co-catalyst include benzene-soluble aluminoxanes of organoaluminum oxy compounds and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of a cation with or without an active hydrogen group and a non-coordinating anion, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

[0027] The transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton may be supported on an inorganic or organic carrier. The carrier is preferably a porous oxide of an inorganic or organic compound, and specific examples include ion-exchange layered silicates such as montmorillonite, SiO2, Al2O3, MgO, ZrO2, TiO2, BO3, CaO, ZnO, BaO, ThO2, and mixtures thereof. Examples of organometallic compounds that can be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0028] Copolymers of ethylene and other monomers can also be used as long as they do not impair the properties of the present invention. Examples of ethylene copolymers include copolymers of ethylene and an α-olefin having 3 to 20 carbon atoms. Examples of α-olefins having 3 to 20 carbon atoms include propylene, 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. Furthermore, copolymers with vinyl acetate or acrylic esters may also be used as long as they do not impair the objectives of the present invention.

[0029] In the present invention, biomass-derived ethylene may be used instead of ethylene obtained from fossil fuels as a raw material for obtaining the polyethylene, etc. Such biomass-derived polyethylene is a carbon-neutral material, and therefore can be used as a packaging material with even less environmental impact.

[0030] Mechanically recycled polyethylene can also be used for the base layer. Mechanical recycling generally refers to the process of crushing recovered polyethylene film, cleaning it with an alkali to remove dirt and foreign matter from the film surface, and then drying it at high temperature and reduced pressure for a certain period of time to disperse any contaminants remaining inside the film, thereby decontaminating it and removing the dirt from the polyethylene film. The film is then melted and turned back into polyethylene resin pellets.

[0031] Cyclic olefin resins are classified into cyclic olefin copolymers (COC) and ring-opening polymerization hydrogenated resins (COP), but either is available. Cyclic olefin copolymers are synthesized by addition polymerization of cyclic olefins and α-olefins. Ring-opening polymerization hydrogenated resins are synthesized by ring-opening polymerization of cyclic olefins and adding hydrogen to the purified double bonds.

[0032] Although the cyclic olefin resin may be added to the entire base layer 10, it may appear on the surface, increasing the surface roughness and potentially causing holes in the vapor deposition layer. Therefore, it is preferable to add the cyclic olefin resin only to the intermediate layer using a multilayer extrusion technique, from the viewpoint of vapor deposition suitability.

[0033] The addition rate to the polyethylene resin is 50% by weight or less relative to the polyethylene of the layer to which it is added. If the addition rate exceeds 50% by weight, the cyclic olefin resin will be distributed in a sea-like structure rather than in islands in the polyethylene resin, making it difficult to achieve easy tearability. If the addition rate is less than 10% by weight, the cyclic olefin resin distributed in islands in the sea-island structure will separate from each other, making it difficult to achieve good tearability.

[0034] The thickness of the sealant layer 8, which will be described later, needs to be adjusted depending on the weight of the contents when the bag is made into a packaging bag. Therefore, when the sealant layer 8 is thick, the amount of cyclic olefin resin added needs to be increased to ensure easy tearing. On the other hand, when the sealant layer 8 is thin and the cyclic olefin resin content is high, the proportion of polyethylene in the entire packaging bag falls below 90% by weight, and good recyclability cannot be achieved.

[0035] The base layer 10 can be formed by an existing method such as an inflation method or a T-die method. Polyethylene and cyclic olefin are dry blended, fed into a film forming machine, heated and melted, extruded into a film, and cooled to form a film. The cyclic olefin is scattered in islands in the polyethylene, resulting in a film with tearability.

[0036] The thickness of the base layer 10 is preferably 10 μm or more and 50 μm or less, and more preferably 12 μm or more and 35 μm or less. By making the thickness of the base layer 10 10 μm or more, the strength of the laminate 20 can be improved. By making the thickness of the base layer 10 50 μm or less, the processability of the laminate 20 can be improved.

[0037] The base layer 10 may also contain additives, such as crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0038] The base layer 10 is not stretched using a stretching device called a tenter, and therefore the polyethylene of the base layer 10 has a structure in which spherical crystals (spherulites) of about 10 to 100 μm in size, which are made up of randomly folded molecular chains, are connected by amorphous molecules. The base layer 10 may be subjected to a surface treatment such as a corona treatment or a plasma treatment to improve adhesion to the anchor coat layer 4.

[0039] <Anchor coat layer> A known anchor coating agent may be used to form the anchor coating layer 4 on the surface of the base layer 10 on which the inorganic vapor deposition layer 5 is to be formed. This improves the adhesion of the inorganic vapor deposition layer 5 made of metal oxide. Examples of anchor coating agents include polyester-based polyurethane resins and polyether-based polyurethane resins.

[0040] <Vapour-deposited layer> Examples of the inorganic vapor deposition layer 5 that serves as the gas barrier layer include vapor deposition layers made of metal oxides such as aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the metal oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, from the viewpoint of cost, aluminum oxide and silicon oxide are selected. By using a vapor deposition layer made of a metal oxide as the barrier layer, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the laminate 20.

[0041] The inorganic vapor deposition layer 5 made of metal oxide has transparency, and therefore has the advantage that, compared to a vapor deposition layer made of metal, it is less likely to cause a user holding the packaging material 30 made of the laminate 20 to mistakenly believe that metal foil is used.

[0042] When aluminum oxide is selected for the inorganic vapor deposition layer 5, the O / Al ratio is preferably 1.4 or higher. An O / Al ratio of 1.4 or higher reduces the aluminum content, making it easier to achieve good transparency. Furthermore, the O / Al ratio is preferably 1.7 or lower. An O / Al ratio of 1.7 or lower increases the crystallinity of AlO, preventing the vapor deposition layer from becoming too hard and providing good tensile strength. In packaging bags using the laminate 20, the substrate 10 may shrink due to heat during the boiling process. However, an O / Al ratio of 1.7 or lower in the inorganic vapor deposition layer 5 facilitates this shrinkage, preventing degradation of barrier properties due to cracks or the like in the inorganic vapor deposition layer 5. To fully achieve these effects, the O / Al ratio of the inorganic vapor deposition layer 5 is preferably 1.4 or higher and 1.7 or lower, more preferably 1.5 or higher and 1.55 or lower.

[0043] When silicon oxide is selected for the inorganic vapor deposition layer 5, the O / Si ratio is preferably 1.7 or higher. An O / Si ratio of 1.7 or higher reduces the silicon content, making it easier to achieve good transparency. Furthermore, the O / Si ratio is preferably 2.0 or lower. An O / Si ratio of 2.0 or lower increases the crystallinity of SiO, preventing the vapor deposition layer from becoming too hard and providing good tensile strength. Furthermore, an O / Si ratio of 2.0 or lower in the inorganic vapor deposition layer 5 makes it easier to adapt to the shrinkage described above and prevents a decrease in barrier properties. To fully achieve these effects, the O / Si ratio of the inorganic vapor deposition layer 5 is preferably 1.75 or higher and 1.9 or lower, and more preferably 1.8 or higher and 1.85 or lower.

[0044] The thickness of the inorganic vapor deposition layer 5 made of aluminum oxide is preferably 5 nm or more and 30 nm or less. A thickness of 5 nm or more ensures sufficient gas barrier properties. Furthermore, a thickness of 30 nm or less can prevent cracks from occurring due to deformation caused by internal stress in the thin film, thereby preventing a decrease in gas barrier properties. Note that a thickness exceeding 30 nm is undesirable from an economic standpoint, as it increases costs due to increased material usage and longer film formation times. From the same viewpoint as above, the thickness of the inorganic vapor deposition layer 5 is more preferably 7 nm or more and 15 nm or less.

[0045] The inorganic vapor deposition layer 5 made of silicon oxide preferably has a thickness of 10 nm or more and 50 nm or less. A thickness of 10 nm or more ensures sufficient gas barrier properties. A thickness of 50 nm or less prevents cracks from occurring due to deformation caused by internal stress in the thin film, thereby preventing a decrease in gas barrier properties. A thickness exceeding 50 nm is undesirable from an economic standpoint, as it increases costs due to increased material usage and longer film formation times. From the same perspective, the thickness of the inorganic vapor deposition layer 5 is more preferably 20 nm or more and 40 nm or less.

[0046] The inorganic vapor deposition layer 5 can be formed by, for example, vacuum film formation. Vacuum film formation can be performed using physical vapor deposition or chemical vapor deposition. Physical vapor deposition methods include, but are not limited to, vacuum deposition, sputtering, and ion plating. Chemical vapor deposition methods include, but are not limited to, thermal CVD, plasma CVD, and photo CVD.

[0047] In the vacuum film formation, resistance heating vacuum evaporation, EB (Electron Beam) heating vacuum evaporation, induction heating vacuum evaporation, sputtering, reactive sputtering, dual magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), and the like are particularly preferably used. However, in terms of productivity, vacuum evaporation is currently the most superior. As a heating means for vacuum evaporation, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method.

[0048] <Overcoat layer> An overcoat layer 6 may be provided to cover the inorganic vapor deposition layer 5. The overcoat layer 6 protects the inorganic vapor deposition layer 5 and exhibits barrier properties independently of the inorganic vapor deposition layer 5. The overcoat layer 6 can be formed using a composition for forming a gas barrier coating layer (hereinafter also referred to as a coating agent) whose main component is an aqueous solution or a water / alcohol mixed solution containing at least one selected from the group consisting of hydroxyl group-containing polymer compounds, metal alkoxides, silane coupling agents, and hydrolysates thereof.

[0049] From the viewpoint of more adequately maintaining gas barrier properties after hot water treatment such as retort treatment, the coating agent preferably contains at least a silane coupling agent or a hydrolyzate thereof, more preferably contains at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, and their hydrolyzates, and a silane coupling agent or a hydrolyzate thereof, and even more preferably contains a hydroxyl group-containing polymer compound or a hydrolyzate thereof, a metal alkoxide or a hydrolyzate thereof, and a silane coupling agent or a hydrolyzate thereof. The coating agent can be prepared, for example, by mixing a metal alkoxide and a silane coupling agent directly, or after having been previously treated by hydrolysis, with a solution obtained by dissolving a hydroxyl group-containing polymer compound, which is a water-soluble polymer, in an aqueous solvent (water or a water / alcohol mixture).

[0050] Each component contained in the coating agent described above will be described in detail. Examples of hydroxyl group-containing polymer compounds used in the coating agent include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate. Using PVA in the coating agent is preferable because it provides the overcoat layer 6 with particularly excellent gas barrier properties.

[0051] From the viewpoint of obtaining excellent gas barrier properties, the overcoat layer 6 is preferably formed from a composition containing at least one selected from the group consisting of metal alkoxides represented by the following general formula (I) and hydrolysates thereof. M(OR 1 ) m (R 2 ) n-m (I) In the above general formula (I), R 1 and R 2 are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. R 1 or R 2 If there are multiple 1 Comrades or R 2 They may be the same or different.

[0052] Specific examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], etc. Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis.

[0053] The silane coupling agent includes a compound represented by the following general formula (II). Si(OR 11 ) p (R 12 ) 3-p R 13 (II) In the above general formula (II), R 11 R indicates an alkyl group such as a methyl group or an ethyl group. 12 R represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group. 13 represents a monovalent organic functional group. p represents an integer of 1 to 3. R 11 or R 12 If there are multiple, R 11 Comrades or R 12 R may be the same or different. 13 Examples of the monovalent organic functional group represented by the formula (I) include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or an isocyanate group.

[0054] Specific examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0055] The silane coupling agent may be a polymer formed by polymerization of the compound represented by the general formula (II). The polymer is preferably a trimer, more preferably 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. This is a condensation polymer of 3-isocyanatoalkylalkoxysilane. It is known that 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate has no chemical reactivity in the isocyanate moiety, but the reactivity is ensured by the polarity of the nurate moiety. It is generally added to adhesives, similar to 3-isocyanatoalkylalkoxysilane, and is known as an adhesion improver. Therefore, adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound can improve the water resistance of a gas barrier coating layer through hydrogen bonding. While 3-isocyanate alkyl alkoxysilanes are highly reactive and have low liquid stability, 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates are not water-soluble due to the polarity of the nurate moiety, but they are easily dispersed in aqueous solutions and can maintain stable liquid viscosity. Furthermore, the water resistance of 3-isocyanate alkyl alkoxysilanes and 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates is equivalent.

[0056] Some 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurates are produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and although the raw material 3-isocyanatepropylalkoxysilane may be contained, this does not pose any particular problems. 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate is more preferred, and 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is even more preferred. Because the methoxy group hydrolyzes quickly and those containing the propyl group are relatively inexpensive, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is practically advantageous.

[0057] If necessary, known additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity adjuster, a colorant, etc. may be added to the coating agent within a range that does not impair the gas barrier properties.

[0058] The thickness of the overcoat layer 6 is preferably 50 to 1000 nm, and more preferably 100 to 500 nm. If the thickness of the overcoat layer 6 is 50 nm or more, more sufficient gas barrier properties tend to be obtained, and if it is 1000 nm or less, sufficient flexibility tends to be maintained.

[0059] The coating liquid for forming the overcoat layer 6 can be applied by, for example, dipping, roll coating, gravure coating, reverse gravure coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, etc. The coating film obtained by applying this coating liquid can be dried by, for example, hot air drying, hot roll drying, high frequency irradiation, infrared irradiation, UV irradiation, or a combination thereof.

[0060] The temperature at which the coating film is dried can be, for example, 50 to 150° C., and preferably 70 to 100° C. By keeping the drying temperature within the above range, the occurrence of cracks in the inorganic vapor deposition layer 5 and the gas barrier coating layer can be further suppressed, and excellent barrier properties can be achieved.

[0061] The overcoat layer 6 may be formed using a coating agent containing a polyvinyl alcohol resin and a silane compound. If necessary, an acid catalyst, an alkali catalyst, a photopolymerization initiator, etc. may be added to this coating agent.

[0062] The polyvinyl alcohol resin may be any of those described above. Examples of the silane compound include a silane coupling agent, polysilazane, and siloxane, and specific examples thereof include tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and hexamethyldisilazane.

[0063] <Print layer> A printing layer can be provided on the inorganic vapor deposition layer 5 or the overcoat layer 6. The printing layer is provided in a position visible from the outside of the laminate 20 for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks taking into consideration printability on the film, design properties such as color tone, adhesion, and safety as a food container. Examples of printing methods that can be used include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the standpoints of productivity and high-resolution images.

[0064] <Heat seal layer> The easy-tearable laminate 20 having barrier properties obtained as described above can be further provided with a heat-seal layer 8 to form a packaging material. The heat-seal layer 8 is made of polyethylene and is bonded by thermal fusion (heat sealing) when the laminate 20 is used to form a packaging material 30 such as a packaging bag. From the viewpoint of heat-sealing properties, the polyethylene constituting the heat-seal layer 8 is preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or very low-density polyethylene (VLDPE). Furthermore, from the viewpoint of environmental impact, it is preferable to use biomass-derived polyethylene or recycled polyethylene for the heat-seal layer.

[0065] Low density polyethylene has a density of 0.900 g / cm 3 More than 0.925g / cm 3The linear low-density polyethylene may be polyethylene having a density of 0.900 g / cm. 3 More than 0.925g / cm 3 Ultra-low density polyethylene can be used with a density of 0.900 g / cm. 3 For the heat seal layer, a copolymer of ethylene and other monomers can be used as long as the properties of the easy-tearable laminate having barrier properties are not impaired.

[0066] The heat seal layer 8 may be a single layer or may have a multi-layer structure. When the heat seal layer 8 has a multi-layer structure, it may have a layer containing at least one of MDPE and HDPE. For example, it may have a three-layer structure consisting of a layer containing at least one of LDPE, LLDPE, and VLDPE, a layer containing at least one of MDPE and HDPE, and a layer containing at least one of LDPE, LLDPE, and VLDPE. This structure allows for improved bag-making suitability and strength while maintaining heat sealability.

[0067] Furthermore, a cyclic olefin resin may be added to the packaging material of the present invention, as long as the polyethylene ratio does not fall below 90% by weight. In this case, it is preferable to add the cyclic olefin resin to the intermediate layer of a multi-layer structure in view of heat sealability and adhesion to the easy-tear laminate 20.

[0068] The thickness of the heat seal layer 8 can be changed as appropriate depending on the weight of the contents to be filled into the packaging material to be produced. For example, when producing a packaging bag to be filled with contents of 1 g or more and 200 g or less, the thickness of the heat seal layer 8 is preferably 20 μm or more and 60 μm or less. A thickness of 20 μm or more can prevent the filled contents from leaking due to damage to the heat seal layer 8. A thickness of 60 μm or less can improve processability.

[0069] As another example, when producing a standing pouch to be filled with contents of 50 g or more and 2000 g or less, the thickness of the heat seal layer 8 is preferably 50 μm or more and 200 μm or less. By making the thickness 50 μm or more, it is possible to prevent the filled contents from leaking due to damage to the heat seal layer 8. Furthermore, by making the thickness 200 μm or less, it is possible to improve processability.

[0070] As a means for laminating the aforementioned easy-tear laminate 20 and the heat seal layer 8, any of the known methods can be used, such as a dry lamination method in which they are bonded together using an adhesive such as a one-component curing or two-component curing urethane adhesive, a non-solvent dry lamination method in which they are bonded together using a solvent-free adhesive, and an extrusion lamination method in which polyethylene resin is heated and melted, extruded into a curtain shape, and bonded together.

[0071] The adhesive layer 7 can also be formed using an adhesive that exhibits gas barrier properties after curing. This can further improve the gas barrier performance of the laminate 20. Examples of such gas barrier adhesives include epoxy adhesives and polyester / polyurethane adhesives. Specific examples include "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Inc. and "Paslim" manufactured by DIC Corporation.

[0072] The thickness of the adhesive layer 7 is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and even more preferably 1 μm or more and 4.5 μm or less. By making the thickness of the adhesive layer 7 0.5 μm or more, the adhesiveness of the adhesive layer 7 can be improved. By making the thickness of the adhesive layer 7 6 μm or less, the processability can be improved.

[0073] <Packaging bag> A packaging bag can be obtained by joining the heat seal layers 8 of the packaging material 30 consisting of the thus obtained easy-tear laminate 20 having barrier properties and the heat seal layer 8 together and heat sealing them. [Example]

[0074] The easy-tearable laminate 20 having barrier properties, the packaging material 30, and the packaging bag of this embodiment will be further described using examples and comparative examples. (Formation of substrate layer) Density 0.930g / cm 3 Medium density polyethylene (MDPE), density 0.950g / cm 3 High density polyethylene (HDPE), density 1.01g / cm 3 A cyclic olefin resin (COC) was prepared. It was melt-extruded from a T-die to form a mixed layer of HDPE / MDPE and COC / HDPE, producing three types of substrate films with a total thickness of 30 μm. MDPE and COC were dry-blended using resin pellets to achieve the desired mixing ratio. The layer ratio was 1:3:1. Base material 1: Ratio of COC in the intermediate layer: 30% by weight, Ratio of COC in the base material layer: approximately 19% by weight Base material 2: Ratio of COC in the intermediate layer: 10% by weight, Ratio of COC in the base material layer: approximately 6% by weight Base material 3: Ratio of COC in the intermediate layer: 5% by weight, Ratio of COC in the base material layer: approximately 3% by weight The composition of the substrate and the polyethylene content (%) are shown in Table 1.

[0075] [Table 1]

[0076] (Preparation of anchor coating agent) Acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in the tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and the mixture was diluted with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. β-(3,4-epoxycyclohexyl)trimethoxysilane was added to the diluted mixture in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and the mixture was mixed to prepare an anchor coating agent.

[0077] (Preparation of Overcoat Agent) An overcoat agent was prepared by mixing the following liquids A, B, and C in a mass ratio of 70 / 20 / 10, respectively. Solution A: A hydrolyzed solution with a solid content of 5% by mass (SiO2 equivalent) obtained by adding 72.1 g of 0.1N hydrochloric acid to 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol and stirring for 30 minutes. Solution B: 5% by mass of polyvinyl alcohol in water / methanol (water:methanol mass ratio 95:5). Liquid C: A hydrolysis solution prepared by diluting 1,3,5-tris(3-trimethoxysilylpropyl) isocyanurate with a water / isopropyl alcohol mixture (water:isopropyl alcohol mass ratio 1:1) to a solids content of 5 mass%.

[0078] (Preparation of easily tearable laminate with barrier properties) One surface of each of Substrates 1, 2, and 3 was subjected to a corona treatment. The above-described anchor coating agent was applied to this corona-treated surface by gravure coating and dried to form a 0.1 μm-thick anchor coating layer. A transparent inorganic vapor deposition layer (alumina vapor deposition layer) made of aluminum oxide with a thickness of 10 nm was formed using a vacuum deposition device with electron beam heating. The O / Al ratio of the alumina vapor deposition layer was 1.5. An overcoat agent was applied to the alumina vapor deposition layer by gravure coating and dried to form a 0.3 μm-thick overcoat layer. A 40 μm-thick sealant film made of linear low-density polyethylene (LLDPE) was laminated onto the overcoat layer by dry lamination using a urethane adhesive, yielding easily tearable laminates 1, 2, and 3 with barrier properties, respectively.

[0079] Furthermore, using substrates 1, 2, and 3, easily tearable laminates 4, 5, and 6 with barrier properties were obtained, respectively, by changing the vapor-deposited layer from aluminum oxide to a 30 nm-thick silicon oxide. The O / Si ratio of the silica vapor-deposited film was set to 1.8 by adjusting the type of vapor-deposited material. The composition and the results of evaluation of the oxygen barrier property and water vapor barrier property using the MOCON method are shown in Table 2. All laminates have good oxygen barrier property and water vapor barrier property.

[0080] [Table 2]

[0081] [Example 1] The laminate 2 and a corona-treated surface of a linear low-density polyethylene (LLDPE) film (thickness 40 μm) serving as a heat seal layer were bonded together using a urethane adhesive to produce a packaging material according to Example 1. The thickness of the adhesive layer was 3.5 μm.

[0082] [Example 2] A packaging material according to Example 2 was prepared in the same manner as in Example 1, except that the laminate was changed to Laminate 5.

[0083] [Comparative Example 1] A packaging material according to Comparative Example 1 was prepared in the same manner as in Example 1, except that the laminate was changed to Laminate 1.

[0084] Comparative Example 2 A packaging material according to Comparative Example 2 was prepared in the same manner as in Example 1, except that the laminate was changed to Laminate 3.

[0085] Comparative Example 3 A packaging material according to Comparative Example 3 was prepared in the same manner as in Example 1, except that the laminate was changed to Laminate 4.

[0086] Comparative Example 4 A packaging material according to Comparative Example 4 was prepared in the same manner as in Example 1, except that the laminate was changed to Laminate 6.

[0087] [Example 3] The laminate 1 and a corona-treated surface of a linear low-density polyethylene (LLDPE) film (thickness 120 μm) serving as a heat seal layer were bonded together using a urethane adhesive to produce a packaging material according to Example 3. The thickness of the adhesive layer was 3.5 μm.

[0088] [Example 4] A packaging material according to Example 4 was prepared in the same manner as in Example 3, except that the laminate was changed to Laminate 4.

[0089] Comparative Example 5 A packaging material according to Comparative Example 5 was prepared in the same manner as in Example 3, except that the laminate was changed to Laminate 2.

[0090] Comparative Example 6 A packaging material according to Comparative Example 6 was prepared in the same manner as in Example 3, except that the laminate was changed to Laminate 3.

[0091] Comparative Example 7 A packaging material according to Comparative Example 7 was prepared in the same manner as in Example 3, except that the laminate was changed to Laminate 5.

[0092] [Comparative Example 8] A packaging material according to Comparative Example 8 was prepared in the same manner as in Example 3, except that the laminate was changed to Laminate 6.

[0093] [Rating 1] The polyethylene content of the packaging material was determined, and packaging materials with a polyethylene content of 90% by weight or more were evaluated as recyclable.

[0094] [Rating 2] Using the packaging material according to each example, a 100 mm x 150 mm packaging bag with heat-sealed edges was produced. The tearability from the notch was evaluated sensorily. The results are shown in Table 3.

[0095] [Table 3]

[0096] As can be seen from Table 3, the packaging bags of Examples 1 to 4 were made using a laminate having barrier properties, and were found to be excellent in recyclability and easy tearability. [Explanation of symbols]

[0097] 1. High-density polyethylene (HDPE) 2. Medium-density polyethylene (MDPE) / cyclic olefin resin (COC) 3. High-density polyethylene (HDPE) 4. Anchor coat layer 5...Inorganic vapor deposition layer 6. Overcoat layer 7...adhesive layer 8. Heat seal layer 10...Base material 20...Laminate 30...Packaging material

Claims

1. In a laminate comprising at least a substrate layer and an inorganic vapor deposition layer, An easily tearable laminate having barrier properties, wherein the substrate layer is made of polyethylene and a cyclic olefin resin.

2. The density of the polyethylene forming the base layer is 0.925 g / cm ３ 2. The easily tearable laminate having barrier properties according to claim 1, wherein:

3. 3. The easily tearable laminate having barrier properties according to claim 1, wherein the inorganic vapor deposition layer is made of a metal oxide.

4. A packaging material comprising the easily tearable laminate having barrier properties according to any one of claims 1 to 3, further laminated with heat-sealable polyethylene.

5. Density 0.925g / cm ３ The packaging material according to claim 4, characterized in that a printed layer is provided on the stretched film made of the above polyethylene, the surface of the printed layer is laminated with the easy-tearable laminate having barrier properties according to any one of claims 1 to 3, and further a heat-sealable polyethylene is laminated on the surface opposite to the easy-tearable laminate having barrier properties.

6. 6. The packaging material according to claim 4, wherein the polyethylene content is 90% by weight or more.

7. A packaging bag using the packaging material according to any one of claims 4 to 6.

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