Polyethylene laminated film

Abstract

To provide a laminate film effective as a sealant film capable of forming a package / a packaging bag excellent in drop impact resistance while being thin without requiring a complicated step such as orientation.SOLUTION: A polyethylene-based laminate film as a polyethylene-based laminate film having at least a seal layer and a main layer is such that: the seal layer contains an ethylene-α olefin copolymer and a propylene-based polymer; the main layer contains an ethylene-α olefin copolymer; and a mass ratio of the ethylene-α olefin copolymer to the propylene-based polymer in the seal layer is 95:5 to 81:19 as the ethylene-α olefin copolymer to the propylene-based polymer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyethylene-based laminate film, a laminate, a packaging bag, and a package in which contents are filled in the packaging bag. [Background technology]

[0002] Bags for food and other items often use plastic films that use polyethylene film as a sealant. From the viewpoint of consideration for the global environment, it is desirable to reduce the amount of plastic used, and it is particularly desirable to reduce the amount of sealants used, which account for a large proportion of the total. However, simply reducing the thickness of plastic film to reduce the amount used often does not meet the specifications necessary to protect food, etc. Typically, an unexpected drop impact can cause the plastic film that makes up the bag to tear, resulting in leakage of the contents.

[0003] From this viewpoint, various films are known. Patent Document 1 describes a multilayer polyethylene sealant film obtained by co-extrusion stretching a sealant layer made of a low-density polyethylene resin or a linear low-density polyethylene resin and an orientation layer made of a polyethylene resin having a melting point higher than that of the sealant layer by an inflation method at a temperature higher than the melting point of the sealant layer and higher than the Picat softening temperature and lower than the melting point of the orientation layer. Patent Document 2 describes a multilayer polyethylene sealant film formed from at least two layers, a sealant layer and an orientation layer, wherein the sealant layer and the orientation layer are both made of a linear low-density polyethylene resin obtained by single-stage polymerization, and the orientation layer is made of two or more types of linear low-density polyethylene resins, the difference between the maximum and minimum melt mass-flow rates of which is 1.0 g / 10 min or more, and the melting points of all the linear low-density polyethylene resins making up the orientation layer are higher than the melting point of the linear low-density polyethylene resin making up the sealant layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6633908 [Patent Document 2] Japanese Patent Publication No. 2020-199674 Summary of the Invention [Problem to be solved by the invention]

[0005] The sealant layer used in current packaging bags is often 20 μm to 120 μm thick, depending on the weight of the contents, etc. However, when the contents are liquids weighing 100 g or more, the sealant layer needs to be thicker. Patent Document 1 describes a multilayer polyethylene sealant film that has a thin wall but good heat seal strength due to an improved orientation of the sealant film, and further describes a package that uses this as a sealant layer and has improved strength. Patent Document 2 describes a multilayer polyethylene sealant film that is thin yet exhibits high tensile strength, impact rupture resistance, and good heat sealing properties, and further describes a packaging bag that uses the film and has excellent rigidity, appearance, and heat sealing properties. The packages and packaging bags using the sealant films described in Patent Documents 1 and 2 have improved strength in the flat areas, but there is a risk that the strength near the sealed portion formed on the periphery may be insufficient due to factors such as relaxation of orientation caused by heat during sealing, and the packages and packaging bags are not satisfactory in terms of drop impact resistance when dropped.

[0006] The problem that the present invention aims to solve is to provide a laminated film that is effective as a sealant film and can be used to form thin-walled packages and packaging bags that have excellent drop impact resistance without requiring complicated processes such as orientation. [Means for solving the problem]

[0007] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by a polyethylene-based laminate film containing at least a seal layer containing an ethylene-α-olefin copolymer and a propylene-based polymer in a mass ratio (ethylene-α-olefin copolymer to propylene-based polymer) of 95:5 to 81:19, and a main layer containing an ethylene-α-olefin copolymer, thereby completing the present invention. That is, the present invention provides the following polyethylene-based laminate film, laminate, packaging bag, and packaging body. (1) A polyethylene-based laminated film having at least a seal layer and a main layer, The sealing layer contains an ethylene-α-olefin copolymer and a propylene-based polymer, The main layer contains an ethylene-α-olefin copolymer, A polyethylene-based laminate film, characterized in that the mass ratio of ethylene-α-olefin copolymer to propylene-based polymer in the seal layer is 95:5 to 81:19, in terms of ethylene-α-olefin copolymer to propylene-based polymer. (2) The polyethylene-based laminate film according to (1), wherein the absolute value of the difference between the melt flow rate of the ethylene-α-olefin copolymer at 190°C and the melt flow rate of the propylene-based polymer at 230°C in the sealing layer is 6.0 g / 10 min or less. (3) The polyethylene-based laminate film according to (1) or (2), wherein the propylene-based polymer in the sealing layer is a block polypropylene and / or a random polypropylene. (4) The polyethylene-based laminate film according to any one of (1) to (3), wherein the crystalline melting peak temperature of the ethylene-α-olefin copolymer in the sealing layer is 100°C or higher and 125°C or lower. (5) A laminate comprising the polyethylene-based laminate film according to any one of (1) to (4). (6) A packaging bag using the polyethylene laminate film according to any one of (1) to (4) or the laminate according to (5). (7) A package in which contents are contained in the packaging bag described in (6). [Effects of the Invention]

[0008] The present invention provides a laminated film that is effective as a sealant film and can be used to form thin packaging bodies and packaging bags that have excellent drop impact resistance without requiring complicated processes such as orientation. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a polyethylene-based laminate film according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a laminate according to one embodiment of the present invention. [Figure 3] 1 is a schematic diagram of a packaging bag / packaging body according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The polyethylene-based laminate film of the present invention is a polyethylene-based laminate film having at least a seal layer and a main layer, wherein the seal layer contains an ethylene-α-olefin copolymer and a propylene-based polymer, and the main layer contains an ethylene-α-olefin copolymer, and the mass ratio of the ethylene-α-olefin copolymer to the propylene-based polymer in the seal layer is 95:5 to 81:19, in terms of ethylene-α-olefin copolymer to propylene-based polymer. The polyethylene-based laminate film of the present invention is applicable as a sealant film for packaging bags.

[0011] <Polyethylene laminated film> (Sealing layer) The seal layer in the polyethylene-based laminate film of the present invention contains an ethylene-α-olefin copolymer and a propylene-based polymer.

[0012] {Ethylene-α-olefin copolymer} The ethylene-α-olefin copolymer contained in the sealing layer is composed of ethylene and an α-olefin having 3 to 20 carbon atoms, and is a copolymer in which the ethylene ratio exceeds 50 mol %. The ethylene-α-olefin copolymer may be used alone or in combination of two or more. Examples of the α-olefin having 3 to 20 carbon atoms include one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, etc. Preferably, one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Of these, a copolymer of ethylene and 1-hexene is preferably used because it is well-balanced in terms of melt flow rate and crystalline melting peak temperature.

[0013] The catalyst used in producing the ethylene-α-olefin copolymer contained in the seal layer is not particularly limited. Examples include Ziegler-Natta catalysts and metallocene catalysts. In the present invention, it is preferable to use a metallocene catalyst, since it can easily produce an ethylene-α-olefin copolymer having a low density, a narrow molecular weight distribution, and excellent impact resistance.

[0014] -Melt flow rate- The melt flow rate (hereinafter sometimes referred to as "MFR" in this specification) of the ethylene-α-olefin copolymer contained in the sealing layer is not particularly limited. For example, it can be 0.5 g / 10 min or more, preferably 1.0 g / 10 min or more, and for example, 20.0 g / 10 min or less, preferably 15.0 g / 10 min or less. If the MFR is less than 0.5 g / 10 min, the film-forming extruder may be overloaded and unable to be discharged during production of the polyethylene-based laminate film of the present invention. On the other hand, if the MFR exceeds 20.0 g / 10 min, the melt viscosity may be significantly reduced, and when the polyethylene-based laminate film of the present invention is produced by an inflation film-forming method, bubbles discharged from a ring die may not rise. Furthermore, when the polyethylene-based laminate film of the present invention is produced by a cast film-forming method, drawdown or neck-in may occur immediately below the die.

[0015] In the present invention, the MFR of the ethylene-α-olefin contained in the seal layer can be measured in grams per 10 minutes by extruding a molten ethylene-α-olefin copolymer from the cylinder of a plastometer / melt indexer through a die at 190°C under a load of 2.16 kg in accordance with JIS K 7210. When a commercially available ethylene-α-olefin is used, the value listed in the catalog may be used. The absolute difference between the MFR of the ethylene-α-olefin copolymer and the MFR of the propylene-based polymer contained in the seal layer is preferably within 6.0 g / 10 min. When the absolute difference between the two MFRs is within this range, the difference in fluidity between the ethylene-α-olefin copolymer and the propylene-based polymer constituting the seal layer is small during heating in the production of the polyethylene-based laminate film, resulting in uniform mixing and dispersion. This ensures that the entire seal layer is in a stable, uniform state, thereby imparting stable drop impact resistance. If the absolute difference between the two MFRs is greater than 6.0 g / 10 min, the ethylene-α-olefin copolymer and propylene-based polymer constituting the seal layer tend not to be uniformly mixed and dispersed, which may make it difficult to impart good drop impact resistance. The absolute value of the MFR difference is preferably less than 4.5 g / min from the viewpoint of uniform mixing and dispersion, and more preferably less than 2.0 g / min. Furthermore, when comparing the MFR of the ethylene-α-olefin copolymer with the MFR of the propylene-based polymer, the MFR of the ethylene-α-olefin copolymer may be smaller, or the MFR of the propylene-based polymer may be smaller. In the seal layer of the polyethylene-based laminate film of the present invention, it is preferable that the MFR of the ethylene-α-olefin, which has a larger mass ratio, is smaller than the MFR of the propylene-based polymer, since this improves the suitability for production by the production method described below.

[0016] -Crystal melting peak temperature- The crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the sealing layer is not particularly limited. For example, it can be set to 100°C or higher and 125°C or lower. This allows packaging bags to be sealed at low temperatures and in a short time when produced using a polyethylene laminate film, improving the efficiency of commercial production. By setting the crystalline melting peak temperature to 100°C or higher and 115°C or lower, the low-temperature and short-time sealing properties are more pronounced and better. In the present invention, the crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the seal layer can be determined from the temperature of the endothermic peak with the greatest intensity detected during the second heating step carried out at a heating rate of 10°C / min when measured with a differential scanning calorimeter (DSC) in accordance with JIS K 7121. When a commercially available ethylene-α-olefin is used, the value listed in the catalog may be used.

[0017] -density- The density of the ethylene-α-olefin copolymer contained in the sealing layer is not particularly limited. A low density, which is advantageous in terms of impact resistance, for example, 0.900 g / cm 3 More than 0.920g / cm 3 It can be as follows:

[0018] {Propylene polymer} Examples of propylene-based polymers contained in the sealing layer include homopolypropylene as a homopolymer, and block polypropylene and random polypropylene, which are copolymers with a copolymerization monomer such as ethylene. Propylene-based polymers can be produced by various methods. For example, they can be produced using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts.

[0019] -Homopolypropylene- Homopolypropylene is a polymer made solely from propylene as a monomer. Unlike block polypropylene and random polypropylene, it does not contain copolymerized monomer components such as ethylene, making it highly crystalline. This gives it the characteristics of high rigidity and high heat resistance.

[0020] -Block polypropylene- Block polypropylene is a resin also known as heterophase polypropylene. For example, (i) an ethylene-propylene block copolymer obtained by homopolymerizing propylene monomer and then copolymerizing ethylene monomer in an amount of less than 50 mol% in a secondary polymerization vessel during the polymerization process; (ii) a resin obtained by mixing a small amount of ethylene-polypropylene copolymer (less than 50% by mass) with homopolypropylene; etc. In the present invention, the content of the ethylene component in the block polypropylene is preferably 30% by mass or more and less than 50% by mass. The block polypropylene having such a composition structure has a Charpy impact strength of 50 kJ / m at 23°C according to JIS K 7111. 2 When a block polypropylene contains an ethylene component as a copolymerization monomer or a mixed copolymer, it is preferable because it can be more easily mixed and dispersed uniformly with an ethylene-α-olefin copolymer than homopolypropylene.

[0021] -Random polypropylene- Random polypropylene refers to a propylene-based resin in which propylene monomers and ethylene monomers and / or butene-1 monomers are randomly copolymerized, and the propylene monomer content is more than 50 mol%. A suitable random polypropylene in the present invention has a copolymerization monomer content of 5 mass% or less. A random polypropylene having such a compositional structure has a Charpy impact strength of 5 kJ / m at 23°C according to JIS K 7111. 2 That's all. When random polypropylene contains ethylene as a copolymerization monomer, it is easier to mix and disperse uniformly with ethylene-α-olefin copolymers than homopolypropylene. Furthermore, compared to block polypropylene, it has superior cold resistance, making it suitable for use in packaging bags for chilled foods and other low-temperature products.

[0022] -MFR- The MFR of the propylene polymer contained in the sealing layer is not particularly limited, and can be, for example, 0.5 g / 10 min or more, preferably 1.0 g / 10 min or more, and 20.0 g / 10 min or less, preferably 15.0 g / 10 min or less. In the present invention, the MFR of the propylene polymer contained in the seal layer can be measured in grams per 10 minutes by extruding a molten propylene polymer from the cylinder of a plastometer / melt indexer through a die at 230°C under a load of 2.16 kg in accordance with JIS K 7210. When a commercially available propylene polymer is used, the value listed in the catalog may be used.

[0023] {Other ingredients} The sealing layer may contain various resins and additives within a range that does not impair the effects of the present invention (for example, less than 20% by mass, preferably less than 5% by mass). Examples of resins include resins other than ethylene-α-olefin copolymers and polypropylene-based polymers. Examples of additives include one or more selected from the group consisting of antistatic agents, antioxidants, lubricants, antiblocking agents (inorganic particles such as silica, organic resin particles such as silicone resins and (meth)acrylic resins), antifogging agents, colorants (organic pigments, inorganic pigments, etc.), UV absorbers, dispersants, fillers (talc, calcium carbonate, etc.), etc.

[0024] - Mass ratio of ethylene-α-olefin copolymer to propylene-based polymer - The mass ratio of the ethylene-α-olefin copolymer to the propylene polymer in the seal layer, in terms of ethylene-α-olefin copolymer to propylene polymer, is 95 to 5 to 81 to 19. This suggests that when the seal layers are sealed together and a partial impact stress is applied, the seal portion can peel and retreat so as to absorb the applied impact. If the mass ratio of the ethylene-α-olefin copolymer in the seal layer is less than 81, the seal may easily peel off when an impact is applied due to dropping or the like. If the mass ratio of ethylene-α-olefin copolymer in the seal layer exceeds 95, the technical significance of using a propylene-based polymer in combination becomes weaker and the adhesive strength approaches that of using ethylene-α-olefin copolymer alone. Although the adhesive strength increases, the ability to absorb the impact caused by peeling and retreat of the seal portion decreases, making the laminated film more likely to tear at the seal edge. The polyethylene-based laminate film of the present invention is configured so as to be able to absorb momentary impact stress when formed into a packaging bag, which is a difference from polyethylene-based laminate films that have been given so-called easy-peel properties.

[0025] (main layer) The main layer in the polyethylene-based laminate film of the present invention contains an ethylene-α-olefin copolymer. The ethylene-α-olefin copolymer contained in the main layer is a copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms, with the ethylene content exceeding 50 mol %. The ethylene-α-olefin copolymer may be used alone or in combination of two or more. Examples of the α-olefin having 3 to 20 carbon atoms include one or more of the monomers copolymerized with ethylene described in {Ethylene-α-olefin copolymer} in the sealing layer. Among these, a copolymer of ethylene and 1-hexene is preferably used because it is well-balanced in terms of melt flow rate and crystalline melting peak temperature.

[0026] The catalyst used in producing the ethylene-α-olefin copolymer contained in the main layer is not particularly limited. Examples include Ziegler-Natta catalysts and metallocene catalysts. In the present invention, it is preferable to use a metallocene catalyst, since it can easily produce an ethylene-α-olefin copolymer having a low density, a narrow molecular weight distribution, and excellent impact resistance.

[0027] The MFR of the ethylene-α-olefin copolymer contained in the main layer is not particularly limited and can be, for example, 0.5 g / 10 min or more, preferably 1.0 g / 10 min or more, and can be, for example, 20.0 g / 10 min or less, preferably 15.0 g / 10 min or less. In the present invention, the MFR of the ethylene-α-olefin contained in the main layer can be measured in grams per 10 minutes by extruding a molten ethylene-α-olefin copolymer from the cylinder of a plastometer / melt indexer through a die at 190°C under a load of 2.16 kg in accordance with JIS K 7210. When a commercially available ethylene-α-olefin is used, the value listed in the catalog may be used.

[0028] The crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the main layer is not particularly limited, and can be, for example, 115°C or higher and 125°C or lower. The crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the main layer is preferably higher than the crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the seal layer, which can reduce damage caused by external heating during the production of packaging bags using the polyethylene-based laminate film. In the present invention, the crystalline melting peak temperature of the ethylene-α-olefin copolymer contained in the main layer can be determined from the temperature of the endothermic peak with the greatest intensity detected during the second heating step carried out at a heating rate of 10°C / min when measured with a differential scanning calorimeter (DSC) in accordance with JIS K 7121. When a commercially available ethylene-α-olefin is used, the value listed in the catalog may be used. The density of the ethylene-α-olefin copolymer contained in the main layer is not particularly limited. A density that exhibits high strength and combines practical rigidity, self-supporting property, etc., such as 0.910 g / cm 3 More than 0.925g / cm 3 It can be as follows:

[0029] The main layer may contain various resins and additives within a range that does not impair the effects of the present invention (for example, less than 20% by mass, preferably less than 5% by mass). The resin may be a resin other than an ethylene-α-olefin copolymer.The additive may be, for example, one or more of the various additives described in (Sealing layer) {Other components}.

[0030] (Structure of polyethylene laminate film) -Layer composition- The layer structure of the polyethylene-based laminate film of the present invention is not particularly limited, and can be, for example, a two-layer structure consisting of a seal layer 1 and a main layer 2, as shown in FIG. 1. Furthermore, if necessary, a heat-resistant resin layer or an adhesive resin layer can be provided between or on these layers. Examples of heat-resistant resin layers include resin layers containing high-density polyethylene as a main component. Examples of adhesive resin layers include resin layers in which polar groups have been introduced into non-polar polyethylene or polypropylene, such as maleic anhydride-grafted polyethylene resin, to impart adhesiveness to different materials. When a packaging bag is formed using a polyethylene-based laminate film as is, the bag will have the seal layer on the inside, so the main layer will be placed on the outside, but by further arranging a heat-resistant resin layer on the outside, the range of selectable sealing temperatures during packaging bag production can be expanded toward higher temperatures. A two-layer structure consisting of a seal layer and a main layer is preferred because it makes it easier to control the thickness of the polyethylene-based laminate film and reduces the number of steps in the production process of the polyethylene-based laminate film.

[0031] -Thickness- The thickness of the polyethylene laminate film of the present invention is not particularly limited. The thickness of the polyethylene laminate film is, for example, 20 μm or more, preferably 30 μm or more, more preferably 40 μm or more, and can be, for example, 200 μm or less, preferably 100 μm or less, more preferably 70 μm or less. When the thickness is in the range of 20 μm or more and 200 μm or less, sealant films, which are widely used as flexible packaging materials, can be made thinner than conventional thicknesses without compromising the balance between flexibility and rigidity, and the resulting package can have practical sealing properties and be imparted with sufficient impact resistance. From the perspective of reducing the amount of plastic used, it is preferable to make the thickness thinner within a practical range, 20 μm or more and 50 μm or less.

[0032] In the polyethylene-based laminate film of the present invention, the thickness ratio between the seal layer and the main layer is not particularly limited. The thickness of the sealing layer, when the total thickness of the polyethylene-based laminate film is taken as 100%, is, for example, 5% or more, preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, and is preferably 50% or less, more preferably 40% or less. The thickness of the main layer, when the total thickness of the polyethylene-based laminate film is taken as 100%, can be, for example, 40% or more, preferably 50% or more, more preferably 60% or more, and can be, for example, 95% or less, preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. Increasing the ratio of the thickness of the main layer makes it easier to form the film while stably exhibiting drop impact resistance, and also improves handling properties during subsequent winding and the like.

[0033] <Laminate> The laminate of the present invention is not particularly limited as long as at least one layer thereof is made of a polyethylene-based laminate film. For example, as shown in FIG. 2, a substrate layer 4 may be provided on the side of the main layer of a polyethylene laminate film where no seal layer is formed. The substrate layer may include one or more layers made of, for example, unstretched, uniaxially stretched, or biaxially stretched films of polyester resins, polyamide resins, polyolefin resins, etc.; gas barrier films obtained by vapor-depositing aluminum, silica, alumina, etc. onto such films; paper; or metals such as aluminum foil. Furthermore, the substrate layer may have two or more substrate layers, which may be the same or different, as needed. These substrate layers can be processed, such as colored or printed, to provide packaging bags with excellent design, gas barrier properties, light-blocking properties, pinhole resistance, curl resistance, etc. If necessary, an intermediate layer may be provided between the polyethylene-based laminate film and the substrate layer or between multiple substrate layers, where the intermediate layer may be one or more layers selected from the group consisting of a printed layer, an adhesive layer, a primer layer, a vapor-deposited layer, etc.

[0034] <Method of manufacturing polyethylene-based laminate film and laminate> The method for producing the polyethylene-based laminate film and the laminate is not particularly limited. Examples of methods for producing the resin or resin composition constituting each layer of the polyethylene-based laminate film and laminate include a method of simultaneously or sequentially mixing the components, such as a method of mixing the components in a tumbler, Henschel mixer, or the like and then directly charging the components into a film-forming machine, or a method of mixing the components in a tumbler, Henschel mixer, or the like and then melt-kneading the components using a single-screw extruder, twin-screw extruder, Banbury mixer, kneader, or the like.

[0035] Examples of methods for producing a polyethylene-based laminate film include a method in which the resin components constituting the seal layer and the main layer are fed into a multilayer T-die film-forming machine or a multilayer inflation film-forming machine and co-extruded, a method in which the resin components constituting the seal layer are melt-extrusion-laminated onto at least one surface of a pre-formed main layer, a method in which the seal layer and the main layer are formed separately and then dry-laminated, etc. Among these, the co-extrusion method using a multilayer T-die or a multilayer inflation film-forming machine is preferred because it requires few steps, is simple, and can achieve sufficiently high interlayer adhesive strength.

[0036] Examples of methods for producing a laminate include a method of laminating a substrate layer onto a polyethylene-based laminate film by dry lamination, a method of laminating a substrate layer via molten polyethylene or the like by sandwich lamination, a method of laminating a polyethylene-based laminate film onto a substrate layer by multilayer coextrusion lamination, a method of coextrusion of all layers constituting the laminate, etc. Among these, the dry lamination method is preferred because it allows the substrate layer, etc. to be laminated via a thin adhesive layer.

[0037] <Packaging bags and packaging> The packaging bag of the present invention is formed by sealing the seal layers of a polyethylene-based laminate film or a laminate of polyethylene-based laminate films. The form of the packaging bag is not particularly limited, and examples thereof include three-sided bags, palm-seated bags, gusseted bags, freestanding bags with a bottom, and bags with a stopper. The package of the present invention is a packaging bag containing a content. The content is not particularly limited, and examples thereof include food, medicine, and beverages.

[0038] <Application> The polyethylene-based laminate film, laminate, packaging bag, and packaging body of the present invention are suitable for applications requiring airtightness and impact resistance, such as packaging films, packaging bags, and packaging bodies for enclosing liquid, gel, or solid foods, medicines, beverages, etc., because they can protect the contents. Furthermore, since the bags are less likely to break even if an unexpected drop impact or the like is applied during transportation, storage, use, etc. of the contents, they are even more suitable, particularly when the contents are liquid, because the contents do not contaminate the surrounding area. [Example]

[0039] Examples and comparative examples of the present invention are shown below, but the present invention is not limited to these. In each example, "parts" means "parts by mass" and "%" means "% by mass".

[0040] [Components] The components of the polyethylene-based laminate film, laminate and packaging bag according to the examples and comparative examples are as follows.

[0041] <Ethylene-α-olefin copolymer> LL1: "Kernel (registered trademark) KF283" (manufactured by Japan Polyethylene Co., Ltd., density = 0.921 g / cm 3 , MFR=2.5g / 10min, crystalline melting peak temperature=108℃): ethylene-1-hexene copolymer polymerized with a metallocene catalyst. LL2: "Evolue (registered trademark) SP1510" (manufactured by Prime Polymer Co., Ltd., density = 0.915 g / cm 3 , MFR=1.0g / 10min, crystalline melting peak temperature=118℃): ethylene-1-hexene copolymer polymerized with a metallocene catalyst.

[0042] <Propylene polymer> HECO1: PC480A (SunAllomer Co., Ltd., density = 0.900 g / cm 3 , MFR = 2.0 g / 10 min, 23°C Charpy impact strength = 68 kJ / m 2 ): Block polypropylene copolymer. RACO1: "PS320M" (SunAllomer Co., Ltd., density = 0.900 g / cm 3 , MFR = 1.2 g / 10 min, 23°C Charpy impact strength = 24 kJ / m 2 ): Random polypropylene copolymer. RACO2: "F744NP" (Prime Polymer Co., Ltd., density = 0.900 g / cm 3 , MFR = 7.0 g / 10 min, 23°C Charpy impact strength = 9 kJ / m 2 ): Random polypropylene copolymer. HOMO1: "PC600A" (SunAllomer Co., Ltd., density = 0.900 g / cm 3 , MFR = 7.5g / 10min, 23℃ Charpy impact strength = 4kJ / m 2 ): Homopolypropylene polymer.

[0043] <Adhesive layer> DL1: "LX500 / KR-90S" (DIC Graphics Corporation, two-component ester adhesive): dry laminating adhesive

[0044] <Base material layer> OPET1: "Toyobo Ester Film (registered trademark) E5100" (manufactured by Toyobo Co., Ltd., thickness 12 μm): biaxially oriented polyethylene terephthalate film

[0045] [Polyethylene laminated film] Example 1 95 parts of LL1 and 5 parts of HECO1 were mixed in a Henschel mixer for 5 minutes to prepare a sealing layer component. The seal layer component and the main layer component (LL2) were each fed into the hopper of a two-layer T-die film-making machine (the screws installed in each extruder had a diameter of 40 mm, an L / D of 31, and a full-flight shape), and the die temperature was set to 230°C to obtain a two-layer polyethylene laminated film having a total laminated film thickness of 40 μm, a seal layer thickness of 10 μm (25% of the total thickness), and a main layer thickness of 30 μm (75% of the total thickness). The surface of the obtained polyethylene laminated film that was not in contact with the main layer and the seal layer was subjected to a corona discharge treatment, and the surface wetting tension at 23°C was adjusted to 38 to 46 mN / m.

[0046] <Examples 2 to 19 and Comparative Examples 1 to 6> A polyethylene-based laminated film was obtained in the same manner as in Example 1, except that the components of the seal layer and main layer were as shown in Table 1.

[0047] [Table 1]

[0048] [Laminates and packaging bags] <Production of laminate and packaging bag> After corona discharge treatment was applied to one side of OPET1, DL1 (dry lamination adhesive) was applied to the corona discharge treated surface of OPET1 at a solid content of 3.3 g / m 2 An adhesive-coated biaxially stretched polyethylene terephthalate film was prepared. The corona discharge treated surface of the main layer of each of the polyethylene laminate films obtained in Examples 1 to 19 and Comparative Examples 1 to 6 was bonded to the adhesive layer of an adhesive-backed biaxially stretched polyethylene terephthalate film to prepare a laminate. The obtained laminate was cut to a size of 170 mm x 320 mm and folded in half so that the inner dimensions were 150 x 150 mm, with the sealing layer facing the inner surface. The two overlapping edges were heat-sealed at a pressure of 0.2 MPa, a sealing time of 1 second, a temperature of 190°C, and a sealing width of 10 mm, to produce 15 packaging bags each with an opening.

[0049] <Evaluation of packaging impact resistance> (Drop bag strength test) Each of the prepared packaging bags was filled with 250 mL of distilled water, and the opening was heat-sealed at a pressure of 0.2 MPa, a sealing time of 1 second, a temperature of 190°C, and a sealing width of 10 mm, to produce five packages each with an inner surface (horizontal surface) of 150 x 150 mm. Each of the resulting packages was dropped from a height of 200 cm so that the horizontal surface landed. If the bag broke after the drop, the evaluation was terminated. If the bag did not break, the same package was dropped again, and the number of times each package was dropped until it broke was counted. The average number of times it was dropped until it broke was taken as the bag drop strength. A bag drop strength of 10.0 or more was judged to be good (passed). The results are shown in Table 2.

[0050] (Tensile impact strength test in accordance with JIS K 7160) Two sheets of film were punched out using a Type 2 dumbbell, method B, so that the sealed portion of the produced packaging bag was in the center, and these were used as test pieces. The tensile impact tester was used with a 4J arm, load and anvil. The results are shown in Table 2. The tensile impact strength was 3000 kJ / m 2 "Super" was judged as "good" (passed).

[0051] (Compression strength test in accordance with JIS Z 0212) The resulting packaging bag was filled with 250 mL of distilled water, and the opening was heat-sealed at a pressure of 0.2 MPa, a sealing time of 1 second, a temperature of 190°C, and a sealing width of 10 mm, to obtain five packages with inner dimensions of 150 x 150 mm (horizontal surface). The resulting package was placed horizontally, a flat plate was placed on top of it to cover the entire package, and a load of 100 kg was applied from above and left for 5 minutes. If no breakage was observed after 5 minutes, a load of 130 kg was applied to the same sample and left for 5 minutes. On average, samples that did not break even at 130 kg were rated "A," those that did not break up to 100 kg were rated "B," and those that broke at 100 kg were rated "C." "A" and "B" were considered pass, and "C" was considered fail. The results are shown in Table 2.

[0052] [Table 2]

[0053] Tables 1 and 2 show that the drop bag strength and tensile impact strength are advantageous when the mass ratio of the ethylene-α-olefin copolymer to the propylene polymer in the seal layer is within the range of 95:5 to 81:19 (ethylene-α-olefin copolymer to propylene polymer). In particular, Examples 2, 3, 5, 6, 8, 9, 10, 13, 14, and 15 show that the mass ratio of the ethylene-α-olefin copolymer to the propylene polymer in the seal layer is particularly preferably within the range of 90:10 to 85:15 (ethylene-α-olefin copolymer to propylene polymer).

[0054] The results of the drop bag strength for Examples 1 to 10 and Examples 11 and 12 in Tables 1 and 2 show that block polypropylene and / or random polypropylene are particularly preferable as the propylene polymer. The bag drop strength results for Examples 1 to 6 and Examples 7 to 9 in Tables 1 and 2 show that it is particularly preferable for the difference in MFR between the ethylene-α-olefin copolymer and the propylene-based polymer constituting the sealing layer to be less than 4.5 g / 10 min. The drop bag strength results for Examples 2, 5, and 8 and Examples 13 to 15 in Tables 1 and 2 show that it is particularly preferable to use an ethylene-α-olefin copolymer having a crystalline melting peak temperature of more than 108°C as the ethylene-α-olefin copolymer constituting the main layer. From the bag drop strength results of Examples 1 to 6 and Examples 16 to 19 in Tables 1 and 2, it can be seen that it is particularly preferable to use an ethylene-α-olefin copolymer having a crystalline melting peak temperature of less than 118°C as the ethylene-α-olefin copolymer constituting the sealing layer. In Comparative Examples 1 to 5 in Tables 1 and 2, the seal peeled off after only a few drops, resulting in leakage of the contents. 2 The seal peeled off at a tensile impact strength of less than 1000 kJ / s. Comparative Example 6, which was a polyethylene film of conventional thickness that was simply made thinner, showed that the drop bag strength was not good. The results of the compressive strength were acceptable in all Examples. From the results of Examples 1, 2, 4, 5, 7, 8, etc., it can be seen that a mass ratio of the polypropylene polymer of about 5 to 10 is particularly preferable for compressive strength.

[0055] When a packaging bag as shown in Figure 3 is constructed using the polyethylene-based laminate film of the present invention or a laminate containing the same, it is possible to increase the adhesive strength of the seal portion around the periphery of the packaging bag while imparting peel back ability for shock absorption to the seal portion, thereby preventing the packaging bag from breaking when dropped, etc., and more reliably protecting the contents. [Explanation of symbols]

[0056] A: Polyethylene laminated film B: Laminate C: Packaging bag / packaging body 1: Sealing layer 2: Main layer 3: Adhesive layer 4: Base material layer

Claims

1. A polyethylene-based laminated film having at least a seal layer and a main layer, the sealing layer contains an ethylene-1-hexene copolymer and a propylene-based polymer, the main layer contains an ethylene-α-olefin copolymer, the propylene-based polymer in the sealing layer is homopolypropylene, block polypropylene, or random polypropylene, the crystalline melting peak temperature of the ethylene-1-hexene copolymer in the seal layer is 100°C or higher and 125°C or lower; a mass ratio of the ethylene-1-hexene copolymer to the propylene-based polymer in the seal layer of 95:5 to 81:19, in terms of ethylene-1-hexene copolymer to propylene-based polymer;

2. 2. The polyethylene-based laminate film according to claim 1, wherein, in the seal layer, the absolute value of the difference between the melt flow rate at 190°C of the ethylene-1-hexene copolymer and the melt flow rate at 230°C of the propylene-based polymer is 6.0 g / 10 min or less.

3. A laminate comprising the polyethylene-based laminate film according to claim 1 or 2.

4. A packaging bag using the polyethylene-based laminate film according to claim 1 or 2 or the laminate according to claim 3.

5. A package comprising the packaging bag according to claim 4 and contents housed therein.

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