JP2023001610A - Easy-to-tear laminate having barrier properties, packaging material and packaging bag - Google Patents

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 The present invention relates to an easily tearable laminate having barrier properties, a packaging material, and a packaging bag.

In recent years, attempts have been made to recycle and use packaging materials, along with growing calls for building a recycling-oriented society. Packaging materials that mainly use the same type of plastic are excellent in mechanical recycling aptitude in which used packaging materials are collected, remelted, and reused as plastic.

Patent Literature 1 proposes a laminate obtained by depositing aluminum oxide on a stretched polyethylene film and laminating a heat seal layer made of polyethylene.

In addition, as an example of a packaging material mainly made of polyethylene that can be opened without using tools such as scissors, Patent Document 2 discloses an intermediate resin made of a blend resin of a cyclic olefin resin and a linear low-density polyethylene resin. Packaging materials with layers have been proposed.

Further, Patent Document 3 proposes to provide a polyolefin packaging bag with a polyurethane layer to impart tearability.

JP 2019-171861 A Japanese Patent No. 5262134 Japanese Patent Publication No. 2020-535034

The stretched polyethylene described in Patent Document 1 has transparency and tearability compared to unstretched polyethylene. As a technique for imparting gas barrier properties against oxygen and the like and barrier properties against water vapor, it is effective to provide a deposited layer of aluminum oxide, silicon oxide, or the like on the substrate surface. However, as a result of studies by the present inventors, when vapor deposition is performed on a stretched polyethylene base material, when a packaging bag is subjected to an impact such as being dropped, the stretched polyethylene base material and the vapor deposition layer are peeled off, resulting in packaging. It became clear that sufficient strength as a bag could not be obtained.

On the other hand, when a vapor deposition layer is provided on high-density polyethylene with a density of 0.925 g/cm ³ or more and unstretched medium-density polyethylene, although sufficient strength as a barrier and packaging bag can be obtained, good There was a problem that tearability was not obtained and it was difficult to open.

In addition, when the straight-chain low-density polyethylene film described in Patent Document 2 is used as a substrate and a vapor deposition layer of inorganic oxide is provided, good tearability was obtained, but the vapor deposition layer was affected by elongation of the substrate film. Cracks were generated, and gas barrier properties could not be obtained.

In addition, when a polyurethane layer is provided as a coating layer on the outer surface of the packaging bag proposed in Patent Document 3, not only does the process of coating the outer surface increase, but it is also less likely to fall off due to rubbing during the filling process and transportation process. There was a risk that the desired effect could not be obtained.

As a method for solving the above problems, the present invention provides an inorganic vapor deposition layer on an unstretched film made of high-density polyethylene to which a cyclic olefin is added and medium-density polyethylene as a base material, so that it has tearability and is a packaging material. It is an object of the present invention to provide a laminate, a packaging material, and a packaging bag using the same, which have strength and barrier properties applicable to the environment.

In order to solve the above problems in the present invention, a first aspect of the present invention is
At least in the laminate consisting of the base material layer and the inorganic deposition layer,
The easy-to-tear laminate having barrier properties is characterized in that the substrate layer comprises polyethylene and a cyclic olefin resin.

Moreover, the second aspect of the present invention is
2. The easily tearable laminate having barrier properties according to claim 1, wherein the density of the polyethylene forming the base material layer is 0.925 g/cm ³ or more.

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

Moreover, the fourth aspect of the present invention is
A packaging material comprising the easy-to-tear laminate having a barrier property according to any one of claims 1 to 3 and a heat-sealable polyethylene layer further laminated thereon.

Moreover, the fifth aspect of the present invention is
A stretched film made of polyethylene having a density of 0.925 g/cm ³ or more is provided with a printed layer, and the printed layer surface is laminated with the easily tearable laminate having barrier properties according to any one of claims 1 to 3, and further 5. The packaging material according to claim 4, further comprising heat-sealable polyethylene laminated on the opposite side of the easy-to-tear laminate having barrier properties.

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

Moreover, the seventh aspect of the present invention is
A packaging bag using the packaging material according to any one of claims 4 to 6.

By the above means, by providing an inorganic vapor deposition layer on an unstretched film made of high-density polyethylene to which a cyclic olefin is added and medium-density polyethylene as a base material, there is tearability, and strength and barrier properties that can be applied to packaging materials. It is possible to provide a laminate, a packaging material, and a packaging bag using the same.

1 is a schematic cross-sectional view of a packaging material according to the present invention; FIG.

This embodiment will be described based on the drawings. FIG. 1 is a schematic cross-sectional view of a packaging material 30 used in one example of this embodiment.
<Base material layer>
The base material layer 1 is made of high density polyethylene (HDPE) having a density of 0.925 g/cm ³ or more and medium density polyethylene (MDPE) to which cyclic olefin resin (COC) is added. A cyclic olefin resin forms a sea-island structure for medium-density polyethylene. At the time of tearing, it can be easily torn along the island-like distribution of the cyclic olefin resin, so that easy tearability can be obtained.

Polyethylenes having different densities and branches can be obtained by appropriately selecting the 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 as a polymerization catalyst, by any of gas phase polymerization, slurry polymerization, solution polymerization, and high pressure ion polymerization, It is preferable to carry out in one stage or in multiple stages of two or more stages.

The above single-site catalyst is a catalyst capable of forming uniform active species, and is usually prepared by contacting a metallocene-based transition metal compound or non-metallocene-based transition metal compound with an activating cocatalyst. . A single-site catalyst is preferable to a multi-site catalyst because it has a uniform active site structure and can polymerize a polymer having a high molecular weight and a highly uniform structure. As the single-site catalyst, it is particularly preferable to use a metallocene-based catalyst. The metallocene catalyst is a catalyst containing a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a cocatalyst, an organometallic compound if necessary, and each catalyst component of a carrier. be.

In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. . Substituted cyclopentadienyl groups include 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. It has at least one substituent selected from groups and the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents are bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, and hydrogenated forms thereof. may be formed. A ring formed by combining substituents with each other may further have a substituent with each other.

In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium and hafnium, with zirconium and hafnium being particularly preferred. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and each ligand having a cyclopentadienyl skeleton is preferably bonded to each other by a bridging group. The bridging group includes an alkylene group having 1 to 4 carbon atoms, a silylene group, a dialkylsilylene group, a substituted silylene group such as a diarylsilylene group, and a substituted germylene group such as a dialkylgermylene group and a diarylgermylene group. A substituted silylene group is preferred. One or a mixture of two or more of the transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component.

The co-catalyst is one that can make the above Group IV transition metal compound of the periodic table effective as a polymerization catalyst, or one that can balance the ionic charges in a catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes of organoaluminumoxy compounds, benzene-insoluble organoaluminumoxy compounds, ion-exchange layered silicates, boron compounds, cations containing or not containing active hydrogen groups, and non-coordinating anions. ionic compounds, lanthanide salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

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 compound carrier and used. As the carrier, porous oxides of inorganic or organic compounds are preferred, and specific examples include ion-exchange layered silicates such as montmorillonite, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ and B ₂ O. ₃ , CaO, ZnO, BaO, _ThO2 , and mixtures thereof. Examples of the organometallic compounds used as necessary include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organic aluminum is preferably used.

Copolymers of ethylene and other monomers can also be used as long as the characteristics of the present invention are not impaired. Ethylene copolymers include copolymers composed of ethylene and α-olefins 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. In addition, it may be a copolymer with vinyl acetate or acrylic acid ester as long as it does not impair the purpose of the present invention.

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 or the like. Since such biomass-derived polyethylene is a carbon-neutral material, it can be used as a packaging material with even less environmental impact.

Polyethylene recycled by mechanical recycling can also be used for the base material layer. Here, mechanical recycling generally means that the recovered polyethylene film or the like is pulverized and washed with alkali to remove dirt and foreign matter from the film surface, and then dried for a certain period of time under high temperature and reduced pressure to remain inside the film. In this method, contaminants are diffused and decontaminated, dirt on a polyethylene film is removed, the film is melted, and polyethylene resin pellets are returned.

Cyclic olefin resins are classified into cyclic olefin copolymers (COC) and ring-opening polymerized hydrogenated resins (COP), both of which can be selected. Cyclic olefin copolymers are synthesized by addition polymerization of cyclic olefins and α-olefins. The ring-opening polymerized hydrogenated resin is synthesized by ring-opening polymerizing a cyclic olefin and adding hydrogen to the purified double bond.

Although it may be added to the entire base material layer 10, the cyclic olefin resin may appear on the surface layer, increasing the surface roughness and causing holes in the vapor deposition layer. It is preferable to use it and add it only to the intermediate layer from the point of vapor deposition suitability.

Moreover, the addition rate to the polyethylene resin is 50% by weight or less with respect to the polyethylene of the layer to which it is added. If it exceeds 50% by weight, the cyclic olefin resin is not distributed like islands in the polyethylene resin, but becomes sea-like, so that easy tearability cannot be obtained. On the other hand, when the content is less than 10% by weight, the island-shaped cyclic olefin resins of the sea-island structure are separated from each other, so that good tearability cannot be obtained.

The thickness of the sealant layer 8, which will be described later, needs to be changed according to the weight of the contents in the packaging bag. Therefore, when the sealant layer 8 is thick, it is necessary to increase the amount of the cyclic olefin resin added in order to ensure easy tearability. On the other hand, when the sealant layer 8 is thin and the addition rate of the cyclic olefin resin is high, the proportion of polyethylene in the entire packaging bag is less than 90% by weight, and good recyclability cannot be obtained.

An existing method such as an inflation method or a T-die method can be used for forming the substrate layer 10 . Polyethylene and cyclic olefin are dry-blended, supplied to a film-forming machine, heated and melted, extruded into a film, and cooled to form a film. A tearable film is formed by the cyclic olefins interspersed in the polyethylene.

The thickness of the base material 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 setting the thickness of the base material layer 10 to 10 μm or more, the strength of the laminate 20 can be improved. By setting the thickness of the base material layer 10 to 50 μm or less, the workability of the laminate 20 can be improved.

In addition, the base layer 10 can contain additives. Examples of additives include cross-linking agents, antioxidants, anti-blocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments and modifying resins.

Since the base material layer 10 is not stretched by a stretching device called a tenter, the polyethylene of the base material layer 10 consists of spherical crystals (spherulites) of about 10 to 100 μm each composed of randomly folded molecular chains. ) has a structure connected by amorphous molecules. The substrate layer 10 may be subjected to surface treatment such as corona treatment or plasma treatment in order to improve adhesion with the anchor coat layer 4 .

<Anchor coat layer>
A known anchor coating agent may be used to form the anchor coat layer 4 on the surface of the substrate layer 10 on which the inorganic deposition layer 5 is formed. As a result, the adhesion of the inorganic deposition layer 5 made of metal oxide can be improved. Examples of anchor coating agents include polyester-based polyurethane resins and polyether-based polyurethane resins.

<Deposition layer>
The inorganic deposited layer 5 that serves as a gas barrier layer includes, for example, a deposited layer made of metal oxide such as aluminum oxide, silicon oxide, magnesium oxide, tin oxide, and the like. From the viewpoint of transparency and barrier properties, the metal oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, considering the cost, it is selected from aluminum oxide and silicon oxide. By using a vapor deposition layer made of a metal oxide as the barrier layer, a very thin layer that does not affect the recyclability of the laminate 20 can achieve high barrier properties.

Since the inorganic vapor deposition layer 5 made of metal oxide has transparency, compared to the vapor deposition layer made of metal, the user who holds the packaging material 30 made up of the laminate 20 will not be able to tell that the metal foil is being used. There is an advantage that it is difficult to cause misidentification of

When aluminum oxide is selected as the inorganic deposition layer 5, the O/Al ratio is desirably 1.4 or more. When the O/Al ratio is 1.4 or more, the aluminum element content is suppressed, and good transparency is likely to be obtained. Also, the O/Al ratio is preferably 1.7 or less. When the O/Al ratio is 1.7 or less, the crystallinity of AlO becomes high, which can prevent the deposition layer from becoming too hard, and good tensile resistance can be obtained. In the packaging bag using the laminate 20, the substrate 10 may shrink due to the heat during the boiling process. This makes it possible to suppress deterioration of the barrier properties due to cracks or the like occurring in the inorganic deposition layer 5 . From the viewpoint of sufficiently obtaining these effects, the O/Al ratio of the inorganic deposition layer 5 is preferably 1.4 or more and 1.7 or less, and more preferably 1.5 or more and 1.55 or less.

When silicon oxide is selected as the inorganic deposition layer 5, the O/Si ratio is desirably 1.7 or more. When the O/Si ratio is 1.7 or more, the silicon element content is suppressed, and good transparency can be easily obtained. Also, the O/Si ratio is preferably 2.0 or less. When the O/Si ratio is 2.0 or less, the crystallinity of SiO becomes high, and the deposited layer can be prevented from becoming too hard, and good tensile resistance can be obtained. Moreover, when the O/Si ratio of the inorganic vapor deposition layer 5 is 2.0 or less, it is easy to follow the shrinkage described above, and a decrease in barrier properties can be suppressed. From the viewpoint of sufficiently obtaining these effects, the O/Si ratio of the inorganic deposition layer 5 is preferably 1.75 or more and 1.9 or less, and more preferably 1.8 or more and 1.85 or less.

The film thickness of the inorganic deposition layer 5 made of aluminum oxide is preferably 5 nm or more and 30 nm or less. Sufficient gas-barrier property can be obtained as a film thickness is 5 nm or more. Further, when the film thickness is 30 nm or less, it is possible to suppress the occurrence of cracks due to deformation due to internal stress of the thin film, and to suppress deterioration of gas barrier properties. If the film thickness exceeds 30 nm, the cost tends to increase due to an increase in the amount of material used and an increase in film formation time, which is not preferable from an economic point of view. From the same viewpoint as above, the film thickness of the inorganic deposition layer 5 is more preferably 7 nm or more and 15 nm or less.

The film thickness of the inorganic deposition layer 5 made of silicon oxide is preferably 10 nm or more and 50 nm or less. Sufficient gas-barrier property can be obtained as a film thickness is 10 nm or more. Further, when the film thickness is 50 nm or less, it is possible to suppress the generation of cracks due to deformation due to internal stress of the thin film, and to suppress deterioration of gas barrier properties. If the film thickness exceeds 50 nm, it is not preferable from an economical point of view because the cost tends to increase due to an increase in the amount of material used and an increase in film formation time. From the same viewpoint as above, the film thickness of the inorganic deposition layer 5 is more preferably 20 nm or more and 40 nm or less.

The inorganic deposition layer 5 can be formed by, for example, vacuum deposition. A physical vapor deposition method or a chemical vapor deposition method can be used in vacuum deposition. Examples of the physical vapor deposition method include a vacuum deposition method, a sputtering method, an ion plating method, and the like, but are not limited to these. Examples of chemical vapor deposition methods include thermal CVD, plasma CVD, and optical CVD, but are not limited to these.

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

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

The coating agent preferably contains at least a silane coupling agent or a hydrolyzate thereof, from the viewpoint of more sufficiently maintaining gas barrier properties after hot water treatment such as retort treatment. It is more preferable to contain at least one selected from the group consisting of hydrolysates thereof and a silane coupling agent or a hydrolyzate thereof, a hydroxyl group-containing polymer compound or a hydrolyzate thereof, a metal alkoxide or It is more preferable to contain a hydrolyzate thereof and a silane coupling agent or a hydrolyzate thereof. The coating agent is prepared by, for example, adding a metal alkoxide and a silane coupling agent directly to a solution obtained by dissolving a hydroxyl group-containing polymer compound, which is a water-soluble polymer, in an aqueous (water or water/alcohol mixed) solvent, or by hydrolyzing it in advance. It can be prepared by mixing products that have been subjected to a treatment such as mixing.

Each component contained in the coating agent described above will be described in detail. Polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like are examples of hydroxyl group-containing polymer compounds used in coating agents. It is preferable to use PVA as the coating agent because the overcoat layer 6 has particularly excellent gas barrier properties.

From the viewpoint of obtaining excellent gas barrier properties, the overcoat layer 6 is 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. is preferred.
M (OR ¹ ) _m (R ² ) _nm (I)
In general formula (I) above, R ¹ and R ² are each independently a monovalent organic group having 1 to 8 carbon atoms, preferably an alkyl group such as methyl or ethyl. M represents an n-valent metal atom such as Si, Ti, Al, Zr. m is an integer from 1 to n. When multiple R ¹ or R ² are present, R ¹ or R ² may be the same or different.

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

Silane coupling agents include compounds represented by the following general formula (II).
Si( ^OR11 ) _p ( ^R12 ) _3- ^pR13 (II)
In general formula (II) above, R ¹¹ represents an alkyl group such as a methyl group or an ethyl group. R ¹² represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an acryloxy-substituted alkyl group, or a methacryloxy-substituted alkyl group. R ¹³ represents a monovalent organic functional group. p represents an integer of 1-3. When multiple R ¹¹ or R ¹² are present, R ¹¹ or R ¹² may be the same or different. The monovalent organic functional group represented by R ¹³ includes a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or a monovalent organic functional group containing an isocyanate group. groups.

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

The silane coupling agent may be a polymer obtained by polymerizing 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 this 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate loses chemical reactivity in the isocyanate portion, but the reactivity is ensured by the polarity of the nurate portion. In general, it is added to adhesives and the like like 3-isocyanate alkylalkoxysilane, and is known as an adhesion improver. Therefore, by adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer can be improved by hydrogen bonding. 3-Isocyanatoalkylalkoxysilane has high reactivity and low liquid stability, whereas 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurate is not water soluble due to its polarity. However, it is easy to disperse in an aqueous solution and can keep the liquid viscosity stable. Also, the water resistance is equivalent to that of 3-isocyanatoalkylalkoxysilane and 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate.

Some 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurates are produced by thermal condensation of 3-isocyanatopropylalkoxysilane, and may contain 3-isocyanatopropylalkoxysilane as a starting material. However, there is no particular problem. More preferred is 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate, and more preferred is 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate. 1,3,5-Tris(3-trimethoxysilylpropyl)isocyanurate is practically advantageous because the methoxy group has a high hydrolysis rate and those containing a propyl group are available at a relatively low cost.

Known additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants may be added to the coating agent as needed within a range that does not impair the gas barrier properties.

The thickness of the overcoat layer 6 is preferably 50-1000 nm, more preferably 100-500 nm. When the thickness of the overcoat layer 6 is 50 nm or more, it tends to be possible to obtain more sufficient gas barrier properties, and when it is 1000 nm or less, it tends to be able to maintain sufficient flexibility.

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

The temperature for drying the coating film can be, for example, 50 to 150°C, preferably 70 to 100°C. By setting the drying temperature within the above range, the occurrence of cracks in the inorganic deposition layer 5 and the gas barrier coating layer can be further suppressed, and excellent barrier properties can be exhibited.

The overcoat layer 6 may be formed using a coating agent containing a polyvinyl alcohol-based resin and a silane compound. Acid catalysts, alkali catalysts, photopolymerization initiators, etc. may be added to this coating agent, if necessary.

As the polyvinyl alcohol resin, those mentioned above can be used. Silane compounds include silane coupling agents, polysilazanes, siloxanes, etc. Specific examples include tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, hexamethyldisilazane. etc.

<Print layer>
A printed layer can be provided on the inorganic deposition layer 5 or the overcoat layer 6 . The printed layer is provided at 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 in consideration of printability on film, design properties such as color tone, adhesion, safety as a food container, etc. be. Examples of printing methods that can be used include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among them, the gravure printing method can be preferably used from the viewpoint of productivity and high definition of the pattern.

<Heat seal layer>
A heat-sealing layer 8 is further provided on the easily tearable laminate 20 having barrier properties obtained as described above to prepare a packaging material. The heat seal layer 8 is made of polyethylene, and is joined by heat sealing when the laminate 20 is used to form a packaging material 30 such as a packaging bag. Low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and very low density polyethylene (VLDPE) are preferable from the viewpoint of heat sealability. Moreover, from the viewpoint of environmental load, it is preferable to use polyethylene derived from biomass or recycled polyethylene for the heat seal layer.

As the low-density polyethylene, polyethylene having a density of 0.900 g/cm ³ or more and less than 0.925 g/cm ³ can be used. As linear low-density polyethylene, polyethylene having a density of 0.900 g/cm ³ or more and less than 0.925 g/cm ³ can be used. As ultra-low density polyethylene, polyethylene with a density of less than 0.900 g/cm ³ can be used. A copolymer of ethylene and other monomers can be used for the heat seal layer as long as the properties of the easily tearable laminate having barrier properties are not impaired.

The heat seal layer 8 may be a single layer or may have a multi-layer structure. If it has a multi-layer structure, it may have a layer containing at least one of MDPE and HDPE. For example, 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/a layer containing at least one of LDPE, LLDPE, and VLDPE can be used. . With such a configuration, it is possible to further improve bag-making aptitude and strength while maintaining heat-sealing properties.

In addition, a cyclic olefin resin may be added to the packaging material of the present invention within a range not less than 90% by weight of polyethylene. In this case, from the viewpoint of heat-sealing properties and adhesion to the easily tearable laminate 20, it is preferable to form a multi-layered structure and add it to the intermediate layer.

The thickness of the heat seal layer 8 can be appropriately changed according to the weight of the contents to be filled in the packaging material to be manufactured. For example, when manufacturing 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. By setting the thickness to 20 μm or more, it is possible to prevent the filled content from leaking due to breakage of the heat seal layer 8 . The processability can be improved by setting the thickness to 60 μm or less.

As another example, when producing a standing pouch 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 setting the thickness to 50 μm or more, it is possible to prevent the filled content from leaking due to breakage of the heat seal layer 8 . Further, by setting the thickness to 200 μm or less, the workability can be improved.

As a means for laminating the above-mentioned easily tearable laminate 20 and the heat seal layer 8, a dry lamination method of bonding with an adhesive such as a one-component curing type or two-component curing type urethane adhesive, or a non-solvent adhesive A known method such as a non-solvent dry lamination method in which polyethylene resin is heated and melted, extruded in the form of a curtain, and laminated together can be employed.

The adhesive layer 7 can also be formed using an adhesive that can exhibit gas barrier properties after curing. Thereby, the gas barrier performance of the laminate 20 can be further improved. Such gas-barrier adhesives include epoxy-based adhesives, polyester/polyurethane-based adhesives, and the like. Specific examples include "Maxieve" manufactured by Mitsubishi Gas Chemical Co., Ltd., "Paslim" manufactured by DIC Corporation, and the like.

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 setting the thickness of the adhesive layer 7 to 0.5 μm or more, the adhesiveness of the adhesive layer 7 can be improved. By setting the thickness of the adhesive layer 7 to 6 μm or less, processability can be improved.

<Packaging bag>
The packaging bag can be obtained by heat-sealing the heat-sealing layers 8 of the packaging material 30 composed of the easy-to-tear laminate 20 having barrier properties and the heat-sealing layer 8 thus obtained. .

The easily tearable laminate 20 having barrier properties, the packaging material 30 and the packaging bag of the present embodiment will be further described using examples and comparative examples.
(Film formation of base material layer)
A medium density polyethylene (MDPE) with a density of 0.930 g/cm ³ , a high density polyethylene (HDPE) with a density of 0.950 g/cm ³ and a cyclic olefin resin (COC) with a density of 1.01 g/cm ³ were prepared. Three types of base films with a total thickness of 30 μm were formed by melt extrusion from a T-die so as to form HDPE/mixed layer of MDPE and COC/HDPE. MDPE and COC were used by dry-blending resin pellets so as to obtain a desired mixing ratio. The layer ratio was 1:3:1.
Substrate 1: COC ratio in intermediate layer: 30% by weight, COC ratio in substrate layer: about 19% by weight Substrate 2: COC ratio in intermediate layer: 10% by weight, COC ratio in substrate layer: 10% by weight Proportion: about 6% by weight
Substrate 3 COC ratio in intermediate layer: 5% by weight, COC ratio in substrate layer: about 3% by weight
Table 1 shows the composition of the substrate and the polyethylene content (%).

(Preparation of anchor coating agent)
Acrylic polyol and tolylene diisocyanate are mixed so that the number of NCO groups of tolylene diisocyanate is equal to the number of OH groups of acrylic polyol, and the total solid content (total amount of acrylic polyol and tolylene diisocyanate ) was diluted with ethyl acetate to 5% by mass. β-(3,4 Epoxycyclohexyl)trimethoxysilane was further added to the mixed solution after dilution so as to be 5 parts by mass with respect to the total amount of 100 parts by mass of acrylic polyol and tolylene diisocyanate, and these were mixed. An anchor coating agent was prepared by doing so.

(Preparation of overcoat agent)
An overcoat agent was prepared by mixing the following A liquid, B liquid, and C liquid at a mass ratio of 70/20/10, respectively.
Solution _A : Solid content of ₅ % by mass ₍ SiO ₂ equivalent) hydrolysis solution.
B solution: 5 mass % water/methanol solution of polyvinyl alcohol (mass ratio of water:methanol is 95:5).
Solution C: 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was diluted with a mixture of water/isopropyl alcohol (mass ratio of water:isopropyl alcohol is 1:1) to a solid content of 5% by mass. Hydrolysis solution.

(Preparation of easily tearable laminate having barrier properties)
One surface of each of the substrates 1, 2, and 3 was subjected to corona treatment. The above anchor coating agent was applied to the corona-treated surface by gravure coating and dried to form an anchor coating layer having a thickness of 0.1 μm. A transparent inorganic vapor deposition layer (alumina vapor deposition layer) made of aluminum oxide and having a thickness of 10 nm was formed using a vacuum vapor deposition apparatus using an electron beam heating system. The O/Al ratio of the alumina deposition layer was 1.5. An overcoat agent was applied onto the alumina deposited layer by gravure coating and dried to form an overcoat layer having a thickness of 0.3 μm. An easy-to-tear laminate 1 having barrier properties obtained by laminating a 40 μm-thick sealant film made of linear low-density polyethylene (LLDPE) on the overcoat layer by a dry lamination method using a urethane-based adhesive, 2 and 3 were obtained, respectively.

Further, easily tearable laminates 4, 5 and 6 having barrier properties were obtained by using the base material 1, the base material 2 and the base material 3 and changing the deposited layer from aluminum oxide to silicon oxide with a thickness of 30 nm. rice field. The O/Si ratio of the silica deposition film was set to 1.8 by adjusting the deposition material species. Table 2 shows the composition and the evaluation results of oxygen barrier property and water vapor barrier property by the Mocon method. All laminates have good oxygen and water vapor barrier properties.

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

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

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

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

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

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

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

[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.

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

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

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

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

[Evaluation 1]
The content of polyethylene in the packaging material was determined, and those of 90% by weight or more were evaluated as recyclable.

[Evaluation 2]
Using the packaging material according to each example, a packaging bag of 100 mm×150 mm with heat-sealed peripheral edges was produced. The tearability from the notch was sensory evaluated. Table 3 shows the results.

As can be seen from Table 3, the packaging bags of Examples 1 to 4 were produced using a laminate having barrier properties, and were found to be suitable for recycling and excellent in tearability.

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 deposition layer 6 Overcoat layer 7 Adhesive layer 8 Heat seal layer 10 Substrate 20 Laminate 30 packaging material

Claims (7)

At least in the laminate consisting of the base material layer and the inorganic deposition layer,
An easy-to-tear laminate having barrier properties, characterized in that the substrate layer comprises polyethylene and a cyclic olefin resin. 2. The easy-to-tear laminate having barrier properties according to claim 1, wherein the polyethylene forming the base layer has a density of 0.925 g/cm ³ or more. 3. The easily tearable laminate having barrier properties according to claim 1 or 2, wherein the inorganic deposition layer is made of a metal oxide. A packaging material comprising the easy-to-tear laminate having barrier properties according to any one of claims 1 to 3 and a heat-sealable polyethylene layer further laminated thereon. A stretched film made of polyethylene having a density of 0.925 g/cm ³ or more is provided with a printed layer, and the printed layer surface is laminated with the easily tearable laminate having barrier properties according to any one of claims 1 to 3, and further 5. The packaging material according to claim 4, wherein heat-sealable polyethylene is further laminated on the opposite side of the easy-to-tear laminate having barrier properties. 6. The packaging material according to claim 4, wherein the content of polyethylene is 90% by weight or more. A packaging bag using the packaging material according to any one of claims 4 to 6.

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