Laminated film and packaging material using the same

Abstract

To provide a laminated film having excellent easy-opening property while using a polyethylene as a single material.SOLUTION: There is provided a laminated film having a base material layer, an adhesive layer and a sealant layer in this order and satisfying the following (1) and (2). (1) The base material layer is composed of a stretched polyethylene film and one of the tensile elongation at break specified by JIS K7127:1999 in the MD direction and TD direction of the base material layer is 50% or less and the other is 60% or more. (2) The sealant layer is composed of a polyethylene film and of the tensile elongation at break specified by JIS K7127:1999 in the MD direction and TD direction of the sealant layer, the tensile elongation at break in the direction where the tensile elongation at break of the base material is 50% or less is 700% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a laminated film and a packaging material using the same.

Background Art

[0002] With the global population increase, flexible packaging used for packaging food, daily necessities, etc. is expected to see an expanding demand in the future. As flexible packaging materials, laminates having a base material with excellent dimensional stability and a heat-sealing layer with heat adhesiveness are common, and often composed of different materials according to functionality. In recent years, from the perspective of global environmental protection, for various packaging materials, a method of recycling as a material (material recycling) has attracted attention, and there is a demand for monomaterial packaging materials made of the same type of material that do not require sorting during recycling.

[0003] As a packaging bag having a base material and a sealant layer, a uniaxially stretched polyethylene film having a density of 940 kg / m 3 or more and a thickness of 10 to 120 μm, characterized in that the surface of the uniaxially stretched polyethylene film has linear half-cut lines in a direction substantially orthogonal to the stretching direction, and a laminated body including a heat-adhesive resin layer as the innermost layer is heat-sealed with the peripheral edge of the heat-adhesive resin layer as a heat-sealing part to form a packaging bag (for example, see Patent Document 1), or a barrier film layer, an ink layer, an adhesive layer, and a sealant layer are laminated in this order, and the barrier film layer is a barrier film obtained by vapor-depositing a metal oxide on a high-density polyethylene resin film base material having a density of 0.940 to 0.980 g / cm 3 and a thickness of 20 to 40 μm, and the sealant layer is an easily tearable multilayer polyethylene resin film having a thickness of 50 to 80 μm and composed of three or more layers. A self-supporting packaging bag (for example, see Patent Document 2) produced from the laminate has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Packaging materials are required to have easy-openability, i.e., to be easily cut in the direction in which opening is desired. Easy-openability has aspects of being cut in the intended cutting direction and having a property of being less likely to leave folds (easy-cutability) and breaking strength. The better the easy-cutability and the lower the breaking strength, the better the easy-openability. For example, as described in Patent Document 1, providing a half-cut line in the opening direction of the base material, or as described in Patent Document 2, using an easily tearable film as the sealant layer tends to improve easy-cutability.

[0006] However, since polyethylene films have low rigidity and are prone to elongation, in a single-material packaging material using a polyethylene film, even when the easy-cutability of one of the base material or the sealant layer is improved as shown in Patent Documents 1 and 2, the other polyethylene film is prone to elongation, resulting in difficulties in maintaining easy-cutability as a packaging material and reducing breaking strength, and there has been a problem of insufficient easy-openability.

[0007] Therefore, an object of the present invention is to provide a laminated film having excellent easy-openability while using polyethylene as a single material. [Means for Solving the Problems]

[0008] <1>A laminated film having a base material layer, an adhesive layer, and a sealant layer in this order, and satisfying the following (1) and (2). (1) The base material layer is made of a stretched polyethylene film, and among the tensile break elongations defined by JIS K7127:1999 in the MD direction and TD direction of the base material layer, one is 50% or less and the other is 60% or more. (2) The sealant layer is made of a polyethylene film, and among the elongation at break specified in JIS K7127:1999 in the MD direction and TD direction of the sealant layer, the elongation at break in the direction where the elongation at break of the base material is 50% or less is 700% or less. <2> The laminated film according to <1>, wherein the stretched polyethylene film is a biaxially stretched polyethylene film. <3> The density of the base material layer is 0.955 g / cm 3 or more and 0.970 g / cm 3 or less, and the laminated film according to <1> or <2>. <4> The laminated film according to any one of <1> to <3>, wherein the base material layer is irradiated with an electron beam. <5> The laminated film according to any one of <1> to <4>, wherein the sealant layer contains 3% by mass or more and 8% by mass or less of polyvinyl alcohol and / or ethylene vinyl acetate copolymer. <6> Among the elongation at break specified in JIS K7127:1999 of the sealant layer, the elongation at break in the direction where the elongation at break of the base material is 50% or less is 300% or less, and the laminated film according to any one of <1> to <5>. <7> The laminated film according to any one of <1> to <6>, wherein the thickness of the sealant layer is 30 μm or more and 50 μm or less. <8> The laminated film according to any one of <1> to <7>, further having a printing layer adjacent to the base material layer. <9> The laminated film according to <8>, further having a protective layer on the outermost layer, and having the protective layer, printing layer, base material layer, adhesive layer, and sealant layer in this order. <10> The laminated film according to <9>, wherein the printing layer and / or the protective layer is made of a cured product of an electron beam curable ink or an electron beam curable composition. <11> A packaging material formed by joining at least a part of the sealant layer of the laminated film according to any one of <1> to <10>. <12> The packaging material according to <11>, wherein the maximum stress specified in Appendix B.1.2 of JIS S 0021-2:2018 is 15 N or less.

Advantages of the Invention

[0009] The laminated film according to the present invention is excellent in easy-openability.

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be specifically described. In the present invention, "above" means the same as or greater than the numerical value shown, and "below" means the same as or less than the numerical value shown.

[0011] In addition, the "main component" means the component contained in the largest amount on a mass basis unless otherwise specified. As a typical aspect, the case where the component exceeds 50% by mass can be mentioned, and preferably, the case where it exceeds 70% by mass can be mentioned.

[0012] The laminated film of the present invention has a base material layer, an adhesive layer, and a sealant layer in this order, and is characterized by satisfying the following (1) and (2). If necessary, a printing layer adjacent to the base material and a protective layer on the outermost layer may be further provided. (1) The base material layer is made of a stretched polyethylene film, and among the tensile elongation at break defined in JIS K7127:1999 in the MD direction and the TD direction of the base material layer, one is 50% or less and the other is 60% or more. (2) The sealant layer is made of a polyethylene film, and among the tensile elongation at break defined in JIS K7127:1999 in the MD direction and the TD direction of the sealant layer, the tensile elongation at break in the direction where the tensile elongation at break of the base material is 50% or less is 700% or less.

[0013] Here, in the present invention, the MD direction and the TD direction refer to the directions perpendicular to the flow direction at the time of laminating the base material layer and the sealant layer, and may or may not coincide with the MD direction and the TD direction of the stretched polyethylene film of the base material layer or the polyethylene film of the sealant layer.

[0014] As described above, in a single-material packaging material using a polyethylene film, even when the easy-cut property of one of the base material layer or the sealant layer is improved, there has been a problem that the easy-opening property becomes insufficient because the other polyethylene film is likely to stretch. In contrast, in the present invention, in addition to the base material layer having the property of being easily stretchable in one direction and easily breakable in the other direction (condition (1)), by reducing the elongation at break of the sealant layer in the direction in which the base material layer is easily breakable (condition (2)), the easy-opening property of the entire laminated film can be improved.

[0015] Next, each layer will be described.

[0016] (Base material layer) The base material layer is made of a stretched polyethylene film. In a laminated film of a polyethylene single material, by using a stretched polyethylene film for the base material layer, it can be easily cut in the stretching direction, and the easy-cut property can be improved. The base material may be a single layer or two or more layers laminated. When two or more base material layers are laminated, it is preferable that the entire laminated base material layer is in the following aspect.

[0017] Examples of the stretched polyethylene film include a uniaxially stretched polyethylene film and a biaxially stretched polyethylene film. Among these, a biaxially stretched polyethylene film is preferable because it is easily cut smoothly even when a force is applied in an oblique direction, and also has excellent followability of the sealant layer, so wrinkles are less likely to remain on the cut surface, and the easy-cut property can be further improved.

[0018] Of the elongation at break in the MD direction and the TD direction of the base material layer, one is 50% or less and the other is 60% or more. When opening the packaging material using the laminated film, it is assumed that breakage occurs in the direction with a smaller elongation at break. If the elongation at break in the direction with a smaller elongation at break exceeds 50%, the base material layer is likely to stretch and the easy-cutability decreases, so the easy-openability decreases. On the other hand, from the viewpoint of handleability, the elongation at break in such a direction is preferably 5% or more. Also, if the elongation at break in the direction with a larger elongation at break is less than 60%, the difference in ease of stretching in the other direction is small and it becomes easy to break in the other direction, so the easy-cutability decreases and the easy-openability decreases. The elongation at break in the direction with a larger elongation at break is preferably 70% or more. Also, the flexibility and strength as the laminated film decrease. On the other hand, from the viewpoint of handleability, the elongation at break in such a direction is preferably 500% or less.

[0019] Here, the elongation at break of the base material layer can be measured by the method specified in JIS K7127:1999. More specifically, a plate-shaped test piece with a width of 15 mm and a length of 100 mm or more is sampled from the base material layer. When sampling a plate-shaped test piece of the base material layer from the laminated film, the sealant layer and other layers are peeled off from the laminated film as necessary. The peeling of the sealant layer is performed by making a cut in a part on the base material layer side of the laminated film so that the sealant layer does not break, then attaching a double-sided tape to the base material layer side and fixing it to a desk or the like, and pulling the sealant layer from the cut portion. For the plate-shaped test piece, a tensile test is performed using a tensilon universal testing machine (RTG-1210 manufactured by Orientec Co., Ltd.) under the conditions of a chuck distance of 50 mm and a tensile speed of 300 mm / min, and the elongation at the time when the plate-shaped test piece breaks is measured. The measurement is performed three times each, and the average value is taken as the elongation at break of the base material layer.

[0020] The elongation at break of the base material layer can be made within a desired range, for example, by the stretching conditions and density of the stretched polyethylene film. Also, from commercially available stretched polyethylene films having various elongations at break, those having a desired elongation at break can be selected and used.

[0021] From the perspective of improving the rigidity as a support, the thickness of the base material layer is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, from the perspective of improving the flexibility of the laminated film, the thickness of the base material layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0022] From the perspective of excellent rigidity and strength and appropriately suppressing the elongation at break, the density of the base material layer is 0.955 g / cm 3 or more and 0.970 g / cm 3 or less is preferable.

[0023] Here, the density of the base material layer can be measured using a dry densitometer with N2 as the filling gas. The measurement is performed 5 times each, and the average value is taken as the density of the base material layer. At this time, the method of collecting the measurement sample of the base material layer from the laminated film is the same as the method of collecting the sheet test piece of the elongation at break.

[0024] It is possible to select and use a stretched polyethylene film having various commercially available densities with the desired density.

[0025] The base material layer is preferably formed by electron beam irradiation. The polyethylene film irradiated with electron beam has high rigidity due to the cross-linking reaction and is difficult to stretch. Therefore, the breaking strength can be further reduced and the easy-open property can be further improved. Also, the heat resistance and strength can be improved.

[0026] As the electron beam, an electron beam with a low acceleration voltage is preferable because no special qualification is required during use and it is easy to handle. The transmission depth of the electron beam varies depending on the acceleration voltage. From the viewpoint of sufficiently promoting the crosslinking reaction to further improve the easy peelability, heat resistance, and strength, the acceleration voltage is preferably 50 kV or higher. On the other hand, from the viewpoint of suppressing damage to the stretched polyethylene film, the acceleration voltage is preferably 300 kV or lower. Also, from the viewpoint of sufficiently promoting the crosslinking reaction to further improve the easy peelability, heat resistance, and strength, the irradiation dose of the electron beam is preferably 10 kGy or higher, and more preferably 45 kGy or higher. On the other hand, from the viewpoint of suppressing damage to the stretched polyethylene film, the irradiation dose of the electron beam is preferably 100 kGy or lower.

[0027] The stretched polyethylene film is preferably subjected to a surface treatment such as corona treatment, burning treatment, or plasma treatment on its surface, which can improve the wettability and adhesiveness with printing ink or an adhesive layer.

[0028] (2) Sealant layer The sealant layer is made of a polyethylene film. In a laminated film of a polyethylene single material, by using the polyethylene film as the sealant layer, appropriate flexibility and heat sealability can be imparted to the laminated film. The sealant layer may be a single layer or two or more layers laminated. When two or more sealant layers are laminated, it is preferable that the entire laminated sealant layer has the following aspect.

[0029] Examples of the polyethylene film include an unstretched polyethylene film, a uniaxially stretched polyethylene film, and a biaxially stretched polyethylene film. Among these, an unstretched polyethylene film is preferable as it can impart high flexibility to the sealant layer.

[0030] Examples of the polyethylene resin constituting the sealant layer include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), etc. Two or more of these may be used. From the viewpoint of recyclability, it is advisable to select a polyethylene resin common to the base material layer.

[0031] Among the elongation at break of the sealant layer, the elongation at break in the direction where the elongation at break of the base material layer is 50% or less is 700% or less. When opening the packaging material using the laminated film, it is assumed that the breakage occurs in the direction where the elongation at break of the base material layer is small. In such a direction, if the elongation at break of the sealant layer is greater than 700%, when opening, the base material layer is cut, but the sealant layer stretches, increasing the breaking strength, or even if it can be cut, wrinkles of the stretched sealant layer remain on the cut surface, reducing the easy cuttability and thus the easy - opening property deteriorates. The elongation at break in such a direction is preferably 300% or less.

[0032] Here, the elongation at break of the sealant layer can be measured by the method specified in JIS K7127:1999, similar to the base material layer. More specifically, a plate - shaped test piece with a width of 15 mm and a length of 100 mm or more is sampled from the sealant layer. When sampling the plate - shaped test piece of the sealant layer from the laminated film, the base material layer and other layers as necessary are peeled off from the laminated film. The peeling of the base material layer is performed by making a cut in a part of the laminated film on the sealant layer side so that the base material layer does not break, then attaching double - sided tape to the sealant layer side and fixing it to a desk etc., and pulling the base material layer from the cut part. For the plate - shaped test piece, the elongation at break when the plate - shaped test piece breaks under the same conditions as the base material layer is measured. The measurement is performed three times each, and the average value is taken as the elongation at break of the sealant layer.

[0033] The elongation at break of the sealant layer can be adjusted to a desired range, for example, by the stretching conditions, density, composition, etc. of the polyethylene film. Also, a polyethylene film having a desired elongation at break can be selected and used from commercially available polyethylene films having various elongations at break.

[0034] From the perspective of improving the strength of the sealant layer, the thickness of the sealant layer is preferably 30 μm or more. On the other hand, from the perspectives of moderately suppressing the breaking strength and further improving the cuttability, the thickness of the sealant layer is preferably 50 μm or less.

[0035] From the perspective of excellent rigidity and strength and moderately suppressing the tensile elongation at break, the density of the polyethylene film used for the sealant layer is 0.955 g / cm 3 or more and 0.970 g / cm 3 or less is preferable.

[0036] Here, the density of the sealant layer can be measured in the same manner as the base material layer. At this time, the method of collecting a measurement sample of the sealant layer from the laminated film is the same as the method of collecting a plate-shaped test piece for the tensile elongation at break.

[0037] It is possible to select and use a polyethylene film having a desired density from commercially available polyethylene films having various densities.

[0038] The melting point of the sealant layer is preferably lower than that of the base material layer. When manufacturing a packaging material from the laminated film, as described later, it is common to bond the sealant layers facing each other by heat sealing. By making the melting point of the sealant layer lower than that of the base material layer, it is possible to easily bond while maintaining the shape of the base material layer.

[0039] The sealant layer preferably contains polyvinyl alcohol and / or ethylene vinyl acetate copolymer, can moderately suppress the elongation at break of the sealant layer, can be easily adjusted within the above-mentioned range, and can further improve the easy-openability. Further, it has excellent gas barrier properties, particularly oxygen barrier properties, and can improve the storage stability of the contents when used as a packaging material. From the viewpoint of further improving such effects, the content of polyvinyl alcohol and ethylene vinyl acetate copolymer is preferably 3% by mass or more. On the other hand, from the viewpoint of single-materialization, the content of polyvinyl alcohol and ethylene vinyl acetate copolymer is preferably 8% by mass. Here, the content of polyvinyl alcohol and ethylene vinyl acetate copolymer means the content when containing either one of them, and the total content when containing two or more of them.

[0040] The sealant layer is preferably formed by electron beam irradiation. The polyethylene film irradiated with electron beam has high rigidity due to crosslinking reaction and is difficult to stretch. Therefore, the breaking strength can be further reduced and the easy-openability can be further improved. Also, the heat resistance and strength can be improved. The preferred mode of electron beam irradiation is the same as that of the electron beam irradiation of the base material layer.

[0041] The sealant layer is preferably subjected to surface treatment such as corona treatment, burning treatment, plasma treatment, etc. on its surface, and the wettability and adhesiveness with the adhesive layer can be improved.

[0042] (Adhesive layer) The adhesive layer preferably contains a resin as a main component. Examples of the resin include polyurethane resin, poly(meth)acrylate resin, etc. By containing polyurethane resin, flexibility can be imparted to the adhesive layer, and the adhesiveness to the base material layer and the sealant layer can be improved. Also, by containing poly(meth)acrylate resin, it can be cured by crosslinking reaction or condensation reaction by irradiation with active energy rays. Two or more of these may be contained. Here, (meth)acrylate is a general term for acrylate and methacrylate.

[0043] The polyurethane resin can be obtained by addition polymerization of a polyol compound having two or more hydroxyl groups and a polyisocyanate compound having two or more isocyanate groups.

[0044] Examples of the polyol compound include neopentyl glycol, 1,3-butanediol, 1,4-butanediol, tripropylene glycol, tetramethylene glycol, glycerin, trimethylolpropane, pentaerythritol, ditrimethylolpropane, diglycerin, dipentaerythritol, ethylene oxide adducts, propylene oxide adducts, tetraethylene oxide adducts, lactone adducts of these, polyester polyols described later, polyol compounds having a carbonate structure, and the like. Two or more of these may be used.

[0045] Examples of the polyisocyanate compound include toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-methylenebiscyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and the like, and nurate-modified products, adduct-modified products, biuret-modified products, allophanate-modified products, and the like of these. Two or more of these may be used.

[0046] The poly(meth)acrylate resin is a (co)polymer of (meth)acrylate. From the viewpoint of curability, (meth)acrylate having two or more (meth)acryloyl groups is preferable. For example, there can be mentioned polyfunctional polymerizable acrylate monomers having four or more functional groups described in International Publication No. 2014 / 156812, polyfunctional (meth)acrylates described in International Publication No. 2017 / 90663, and the like. Two or more of these may be used. From the viewpoints of safety and environment, (meth)acrylate preferably has low volatility.

[0047] From the viewpoint of improving coatability, the thickness of the adhesive layer is preferably 0.1 μm or more, more preferably 1.0 μm or more. On the other hand, the thickness of the adhesive layer is preferably 3.0 μm or less, more preferably 2.0 μm or less.

[0048] (Printing layer) From the viewpoint of design, the laminated film of the present invention preferably has a printing layer adjacent to the base material layer. Here, the printing layer refers to a state in which ink is applied and then fixed to the base material layer by drying or curing.

[0049] Typical examples of the ink include those in which pigments or dyes are mixed with a binder, such as heat-drying inks such as solvent inks and aqueous inks, oxidation-polymerization type oil-based inks, and active energy ray-curing inks that are cured by irradiation with active energy rays.

[0050] Among these, electron beam-curing inks are preferred. That is, it is preferable that the printing layer is composed of a cured product of an electron beam-curing ink. Such an ink layer has high film strength and can improve scratch resistance. In addition, since the energy required for drying is small, the environmental load can be reduced.

[0051] (Protective layer) The laminated film of the present invention further has a protective layer, and it is preferable to have the protective layer, printing layer, base material layer, adhesive layer, and sealant layer in this order. That is, it is preferable to have the protective layer on the outermost surface. The structure of the printing layer / base material layer / adhesive layer / sealant layer is a so-called surface printing structure. By having a protective layer on the surface of the printing layer, the printing layer can be physically protected, and design properties such as glossiness and matteness can be imparted to the appearance.

[0052] As the protective layer, a varnish film is preferable. For example, heat-drying varnishes such as solvent-based varnishes and water-based varnishes, and active energy ray-curable varnishes that are cured by irradiation with active energy rays can be mentioned. Examples of water-based varnishes include those containing self-emulsifying or surfactant-emulsifying acrylic resins, acrylic epoxy resins, and acrylic amino resins. Examples of active energy ray-curable varnishes include those containing (meth)acrylate oligomers such as urethane (meth)acrylate, ester (meth)acrylate, and epoxy (meth)acrylate.

[0053] Among these, an electron beam-curable varnish is preferable. That is, it is preferable that the protective layer is composed of a cured product of an electron beam-curable varnish. Such a protective layer has high film strength and can improve scratch resistance. In addition, since the energy required for drying is small, the environmental load can be reduced.

[0054] (Method for manufacturing a laminated film) Next, the method for manufacturing the laminated film of the present invention will be described with examples.

[0055] The laminated film of the present invention can be obtained, for example, by preparing a stretched polyethylene film as a base material layer and a polyethylene film as a sealant layer in advance, and laminating them via components constituting an adhesive layer. According to such a manufacturing method, the degree of freedom in designing the stretched polyethylene film as the base material layer and the polyethylene film as the sealant layer (for example, selection of materials, degree of stretching, etc.) can be increased. As described above, each of the stretched polyethylene film as the base material layer and the polyethylene film as the sealant layer may be a laminated film, a coextruded film, or a laminate of a plurality of films.

[0056] As the laminating method, for example, (i) an adhesive composition is applied to one of a stretched polyethylene film serving as a base material layer or a polyethylene film serving as a sealant layer, and after laminating the other polyethylene film on the wet coating film, it is cured; (ii) an adhesive composition curable by active energy rays is applied to one of a stretched polyethylene film serving as a base material layer or a polyethylene film serving as a sealant layer, the other polyethylene film is laminated, and then active energy rays are irradiated; (iii) an adhesive composition curable by active energy rays is applied to one of a stretched polyethylene film serving as a base material layer or a polyethylene film serving as a sealant layer, active energy rays are irradiated, and then the other polyethylene film is laminated. When the adhesive composition contains a solvent, it is preferable to remove the solvent by drying. The method of irradiating active energy rays is preferable because a laminated film can be obtained in a short time.

[0057] When the adhesive composition contains a polyol compound and a polyisocyanate compound, the curing temperature is preferably 25°C or higher and 60°C or lower, which can efficiently promote the reaction between the polyol compound and the polyisocyanate compound and improve the adhesion.

[0058] As the laminating method of irradiating active energy rays, the method (iii) is preferable. Since the active energy rays can be directly irradiated to the adhesive composition, the curability can be improved. Also, depending on the energy ray source, the influence on the other polyethylene film can be avoided.

[0059] Examples of the active energy ray source include ultraviolet rays, electron beams, gamma rays, etc. Among these, an electron beam that does not require an initiator is preferred. When irradiating with an electron beam, the acceleration voltage is preferably 50 kV or more and 300 kV or less. Also, from the viewpoint of sufficiently advancing the crosslinking reaction to further improve the easy peelability, heat resistance, and strength, the irradiation dose is preferably 10 kGy or more, more preferably 45 kGy or more. On the other hand, from the viewpoint of suppressing damage to the stretched polyethylene film, the irradiation dose of the electron beam is preferably 100 kGy or less.

[0060] When the laminated film has a printing layer, in the case of the substrate layer / printing layer / adhesive layer / sealant layer configuration, so-called reverse printing configuration, it is preferable to laminate the sealant layer via the adhesive layer after printing on the substrate layer. In such a configuration, a printing layer can be easily formed on the substrate layer to impart designability. Also, deterioration over time can be suppressed by protecting the printing layer. Also, in the case of the protective layer / printing layer / substrate layer / adhesive layer / sealant layer configuration, so-called front printing configuration, after forming a printing layer on the laminated film, a protective layer may be formed, or after forming a printing layer and a protective layer on both sides of the substrate layer, it is preferable to laminate the sealant layer via the adhesive layer. From the viewpoint of productivity, the former is preferred.

[0061] (Packaging material) The packaging material of the present invention is formed by joining at least a part of the sealant layer of the above-mentioned laminated film. For example, by facing the sealant layers of the above-mentioned laminated film and joining them by heat sealing, a packaging material of a desired shape can be obtained. For example, various shapes of packaging materials can be obtained according to the heat sealing modes such as side seal, two-side seal, three-side seal, four-side seal, pillow seal, pleated seal, flat bottom seal, corner bottom seal, gusset type, etc. For example, a self-supporting packaging material (standing pouch) etc. can also be obtained.

[0062] As a method for manufacturing a bag-shaped packaging material, for example, the laminated film of the present invention is folded in half so that the base material layer is on the outside and the sealant layer is on the inside (the content side), and the ends of the overlapped layers are heat-sealed, or two laminated films of the present invention are overlapped so that the sealant layers face each other, and the ends thereof are heat-sealed.

[0063] Examples of heat-sealing methods include bar sealing, impulse sealing, belt sealing, rotary roll sealing, high-frequency sealing, ultrasonic sealing, etc.

[0064] The packaging material of the present invention preferably has a maximum stress of 15 N or less, more preferably 5 N or less, as defined in Appendix B.1.2 of JIS S 0021-2:2018. The lower the maximum stress due to tearing, the better the easy-openability.

[0065] Here, the maximum stress can be measured by T-peel using a tensilon universal testing machine (RTG-1210 manufactured by Orientec Co., Ltd.). More specifically, when there is a notch provided in the packaging material to facilitate opening, for example, the parts on both sides sandwiching the notch at the part where the packaging material is to be opened are held by the chucks of the tensilon universal testing machine, and a tensile test of T-peel is performed under the conditions of a chuck distance of 50 mm and a tensile speed of 500 mm / min, and the maximum stress when the packaging material breaks is measured. The measurement is performed 3 times each, and the average value is taken as the maximum stress.

Examples

[0066] Hereinafter, the present invention will be described more specifically by giving examples. However, the present invention is not construed as being limited to these examples.

[0067] First, the measurement and evaluation methods in each example and comparative example will be described.

[0068] (1) Tensile elongation at break Regarding the polyethylene films used for the base material layer and the sealant layer in each of the examples and comparative examples, the elongation at break was measured by the method specified in JIS K7127:1999. That is, from each film, a plate-shaped test piece with a width of 15 mm and a length of 100 mm or more was taken, and a tensile test was conducted using a tensilon universal testing machine (RTG-1210 manufactured by Orientec Co., Ltd.) under the conditions of a chuck distance of 50 mm and a tensile speed of 300 mm / min, and the elongation at the time when the plate-shaped test piece broke was measured. The measurement was performed three times for each, and the average value was taken as the elongation at break.

[0069] (2) Density Using a dry-type automatic densitometer (AccuPycll 1345 manufactured by Micromeritics), the polyethylene films used for the base material layer and the sealant layer in each of the examples and comparative examples were placed so that more than 50% of the cell was filled, and the density was measured under the following conditions. The measurement was performed five times for each, and the average value was taken as the density. Filling gas: N2 gas Number of gas purge cycles: 5 Filling pressure during purge: 134.447 kPag Filling pressure during measurement: 134.447 kPag Criterion for pressure parallelism: 0.0345 psig / min.

[0070] (3) Ease of cutting Samples simulating the packaging materials obtained in each of the examples and comparative examples were manually cut in the long side direction from the notch portion. The cut surface was visually observed and evaluated according to the following criteria. A: Can be cut straight, and no wrinkles are observed on the cut surface B: Can be cut straight, but wrinkles are observed on the cut surface C: Cut obliquely, but no wrinkles are observed on the cut surface D: Cut obliquely, and wrinkles are observed on the cut surface.

[0071] (4) Maximum stress Cellophane tape was attached to both ends of each short side of the sample simulating the packaging materials obtained in each example and comparative example, with the notch sandwiched. Using a tensilon universal testing machine (RTG-1210 manufactured by Orientec Co., Ltd.), the cellophane tape was held by a chuck, and a tensile test for T-peel was performed under the conditions of a chuck distance of 50 mm and a tensile speed of 500 mm / min. The maximum stress when the strip-shaped test piece broke along the notch was measured. The measurement was performed three times for each, and the average value was calculated as the maximum stress specified in Appendix B.1.2 of JIS S 0021-2:2018.

[0072] Next, the materials used in each example and comparative example will be described.

[0073] [Base material layer] Base material film 1: A uniaxially stretched polyethylene (MOPE) film with a thickness of 25 μm (PE3K-H manufactured by Futamura Chemical Co., Ltd., elongation in one direction of 70%, elongation in the other orthogonal direction of 6%, density 0.963 g / cm 3 ) Base material film 2: A MOPE film with a thickness of 25 μm (PE3M-XH manufactured by Futamura Chemical Co., Ltd., elongation in one direction of 250%, elongation in the other orthogonal direction of 50%, density 0.961 g / cm 3 ) Base material film 3: A MOPE film with a thickness of 25 μm (M758XP manufactured by rkw, elongation in one direction of 118%, elongation in the other orthogonal direction of 75%, density 0.979 g / cm 3 ) Base material film 4: A biaxially stretched polyethylene (BOPE) film with a thickness of 25 μm (HD213 manufactured by Jindal, elongation in one direction of 195%, elongation in the other orthogonal direction of 48%, density 0.960 g / cm 3 ) Base material film 5: An unstretched PE film with a thickness of 40 μm (KF101M manufactured by Futamura Chemical Co., Ltd., elongation in one direction of 1080%, elongation in the other orthogonal direction of 681%, density 0.946 g / cm 3 ) Base material film 6: A BOPE film with a thickness of 25 μm (elongation in one direction of 373%, elongation in the other orthogonal direction of 48%, density 0.940 g / cm 3 ) Base film 7: BOPE film with a thickness of 25 μm (elongation in one direction of 172%, elongation in the other direction perpendicular thereto of 36%, density 0.955 g / cm 3 ) [Sealing layer] Sealant 1: Low-density polyethylene (LLDPE) film with a thickness of 40 μm (TUX-HC manufactured by Toppan Printing Co., Ltd., elongation in one direction of 844%, elongation in the other direction perpendicular thereto of 643%, containing no ethylene vinyl acetate copolymer) Sealant 2: LLDPE film with a thickness of 30 μm (V-1 manufactured by Tamapoly Co., Ltd., elongation in one direction of 568%, elongation in the other direction perpendicular thereto of 150%, containing no ethylene vinyl acetate copolymer) Sealant 3: LLDPE film with a thickness of 30 μm (SB-5 manufactured by Tamapoly Co., Ltd., elongation in one direction of 677%, elongation in the other direction perpendicular thereto of 159%, ethylene vinyl acetate copolymer content 5% by mass) Sealant 4: LLDPE film with a thickness of 80 μm (SB-5 manufactured by Tamapoly Co., Ltd., elongation in one direction of 761%, elongation in the other direction perpendicular thereto of 27%, ethylene vinyl acetate copolymer content 5% by mass) Sealant 5: LLDPE film with a thickness of 75 μm (K477 / 12 manufactured by rkw, elongation in one direction of 1090%, elongation in the other direction perpendicular thereto of 778%, containing no ethylene vinyl acetate copolymer) Sealant 6: LLDPE film with a thickness of 40 μm (TUX-UDF manufactured by Toppan Printing Co., Ltd., elongation in one direction of 987%, elongation in the other direction perpendicular thereto of 660%, containing no ethylene vinyl acetate copolymer) [Adhesive composition] Dry-mixed laminate adhesive (“Takelac” (registered trademark) A953 / “Takenate” (registered trademark) A93 manufactured by Mitsui Chemicals, Inc.), with polyurethane resin as the main component.

[0074] (Example 1) The adhesive composition was applied to Base film 1 so that the dry film thickness became 2.0 g / m 2 and dried at 80 °C for 1 minute using an oven. Sealant 1 was laminated with the MD direction of Base film 1 aligned with the MD direction of Sealant 1 as the MD direction and cured at 40 °C for 72 hours.

[0075] The obtained laminated film was folded so that the sealant layers faced each other, and the short side of a strip-shaped test piece with the long side in the high elongation direction being 100 mm and the short side in the low elongation direction being 30 mm was heat-sealed using a heat sealer (TP-701-B manufactured by Tester Sangyo Co., Ltd.). A notch with a depth (in the long side direction) of 10 mm or less was formed near the center of the heat-sealed short side to facilitate opening, and a sample simulating a packaging material was obtained.

[0076] [Examples 2 to 5] A laminated film was produced in the same procedure as in Example 1 except that the base film 1 was changed to base films 2, 4, 6 to 7, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 1.

[0077] [Examples 6 to 9] A laminated film was produced in the same procedure as in Example 1 except that the sealant 1 was changed to sealants 2 to 4, 6, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 1.

[0078] [Examples 10 to 13] A laminated film was produced in the same procedure as in Example 3 except that the sealant 1 was changed to sealants 2 to 4, 6, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 1.

[0079] [Comparative Example 1] A laminated film was produced in the same procedure as in Example 1 except that the sealant 1 was changed to sealant 5, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 2.

[0080] [Comparative Examples 2 to 3] A laminated film was produced in the same procedure as in Example 1 except that the base film 1 was changed to base films 3, 5, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 2.

[0081] [Comparative Example 4] A laminated film was produced in the same procedure as in Example 9 except that the base film 1 was changed to the base film 5, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 2.

[0082] [Example 14] A laminated film was produced in the same procedure as in Example 1 except that after the base film 1 was irradiated with electron beams under the conditions of an acceleration voltage of 110 kV and an irradiation dose of 30 kGy (Condition A) using an electron beam irradiation apparatus (EC250 / 30 / 90LS manufactured by Iwasaki Electric Co., Ltd.), an adhesive composition was applied, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 3 together with those of Example 1.

[0083] [Example 15] A laminated film was produced in the same procedure as in Example 14 except that after the sealant film 1 was irradiated with electron beams under the conditions of an acceleration voltage of 110 kV and an irradiation dose of 30 kGy (Condition B) using an electron beam irradiation apparatus (EC250 / 30 / 90LS manufactured by Iwasaki Electric Co., Ltd.), it was bonded to the base film 1, and a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 3.

[0084] [Example 16] After a laminated film was produced in the same procedure as in Example 1, electron beam irradiation was performed from the base material layer side under the conditions of an acceleration voltage of 110 kV and an irradiation dose of 30 kGy (Condition C) using an electron beam irradiation apparatus (EC250 / 30 / 90LS manufactured by Iwasaki Electric Co., Ltd.), and then a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 3.

[0085] [Example 17] After electron beam irradiation was performed on the laminated film in the same procedure as in Example 16 except that the irradiation dose of electron irradiation was changed to 90 kGy (Condition D), a sample simulating a packaging material was obtained. The results evaluated by the above-described method are shown in Table 3.

[0086] [Examples 18 to 21] A laminated film was produced in the same procedure as in Examples 14 to 17 except that Sealant 1 was changed to Sealant 3, and a sample simulating a packaging material was obtained. The results evaluated by the above method are shown in Table 3 together with those of Example 7.

[0087]

Table 1

[0088]

Table 2

[0089]

Table 3

Claims

1. A laminated film having a base material layer, an adhesive layer, and a sealant layer in this order, and satisfying the following (1) and (2). (1) The base material layer is made of a stretched polyethylene film, and among the tensile break elongations defined by JIS K7127:1999 in the MD direction and the TD direction of the base material layer, one is 50% or less and the other is 60% or more. (2) The sealant layer is made of a polyethylene film, and among the tensile break elongations defined by JIS K7127:1999 in the MD direction and the TD direction of the sealant layer, the tensile break elongation in the direction where the tensile break elongation of the base material is 50% or less is 700% or less.

2. The laminated film according to claim 1, wherein the base material layer is a biaxially stretched polyethylene film.

3. The density of the base material layer is 0.955 g / cm ３ or more and 0.970 g / cm ３ or less. The laminated film according to claim 1 or 2.

4. The laminated film according to claim 1 or 2, wherein the base material layer is irradiated with an electron beam.

5. The laminated film according to claim 1 or 2, wherein the sealant layer contains 3% by mass or more and 8% by mass or less of polyvinyl alcohol and / or an ethylene-vinyl acetate copolymer.

6. The laminated film according to claim 1 or 2, wherein among the tensile break elongations defined by JIS K7127:1999 of the sealant layer, the tensile break elongation in the direction where the tensile break elongation of the base material is 50% or less is 300% or less.

7. The laminated film according to claim 1 or 2, wherein the thickness of the sealant layer is 30 μm or more and 50 μm or less.

8. The laminated film according to claim 1 or 2, further having a printing layer adjacent to the base material layer.

9. The laminated film according to claim 8, further having a protective layer on the outermost layer, and having the protective layer, the printing layer, the base material layer, the adhesive layer, and the sealant layer in this order.

10. The laminated film according to claim 9, wherein the printing layer and / or the protective layer is made of a cured product of an electron beam curable ink or an electron beam curable composition.

11. A packaging material formed by joining at least a part of the sealant layer of the laminated film according to claim 1 or 2.

12. The packaging material according to claim 11, wherein the maximum stress defined by JIS S 0021-2:2018, Annex B.1.2 is 15 N or less.

Images