Laminate, packaging material, packaging body, and method for manufacturing laminate

Abstract

To provide a laminate that is obtained by directly bonding a resin layer and a paper base material even when the resin layer is thin, which can obtain good adhesive strength between the paper base material and the resin layer, and can suppress occurrence of curling.SOLUTION: A laminate 10 includes a paper base material 1, and a resin layer 2 provided adjacent to the paper base material 1 on one side or double sides of the paper base material 1, where the paper base material 1 has a basis weight of 10 g / m2 or more and less than 100 g / m2, the resin layer 2 contains an ethylene-unsaturated carboxylic acid-based copolymer (A), the resin layer 2 has thickness of 1 μm or more and less than 20 μm, and the laminate 10 has both TD curl a and MD curl a measured according to specific measurement conditions of less than 10 mm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate, a packaging material, a package, and a method for manufacturing a laminate. [Background technology]

[0002] Efforts to address environmental issues are spreading worldwide, with particular attention being paid to reducing the use of plastics and organic solvents. As one approach to reducing plastic use, there has been increasing consideration of using paper, a biomass material, as a packaging material. However, paper itself does not have any sealing properties, and its use as a packaging material is limited to very limited uses, purposes, and packaged items. For this reason, composite materials made by laminating paper and plastic are generally used to impart sealing properties to paper.

[0003] Because paper and plastic are generally difficult to bond, a paper substrate and a plastic film are often laminated together using an adhesive containing an organic solvent. For example, Patent Document 1 describes laminating pure white paper and a biaxially oriented polyethylene terephthalate film using a two-component curing dry lamination adhesive. Furthermore, Patent Documents 2 and 3 describe laminating a paper layer and a sealant film made of unstretched polyethylene film (LLDPE) via a gas barrier adhesive layer containing a polyester polyol and a polyisocyanate compound.

[0004] On the other hand, a technique for directly laminating paper and plastic without using an adhesive containing an organic solvent (so-called direct adhesion) is also known.

[0005] For example, Patent Document 4 describes laminating high-pressure low-density polyethylene onto a corona-treated paper substrate. Patent Document 5 describes laminating a resin composition of ethylene-α-olefin copolymer and propylene-ethylene copolymer onto kraft paper. Patent Document 6 describes laminating a resin composition of low-density polyethylene resin and polyester resin with a compatibilizer added onto pure white roll paper. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-24372 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-226186 [Patent Document 3] Japanese Patent Application Publication No. 2018-1539 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-51632 [Patent Document 5] Japanese Patent Application Laid-Open No. 2017-132134 [Patent Document 6] Japanese Patent Application Laid-Open No. 2007-276194 Summary of the Invention [Problem to be solved by the invention]

[0007] From the viewpoint of reducing the amount of organic solvent used, it is preferable to directly laminate paper and plastic without using an adhesive containing an organic solvent, as described above. Furthermore, even when directly laminating paper and plastic, it is preferable to use as little plastic as possible from the viewpoint of reducing the amount of plastic used. Therefore, it is desirable that the plastic be a thin film.

[0008] Furthermore, conventional laminates in which paper and plastic are directly laminated together are prone to curling, which can often result in defective products or problems during molding and processing.

[0009] The present invention has been made in consideration of the above circumstances, and provides a laminate in which a paper substrate and a plastic are directly laminated together, which can be made into a thin film and can suppress the occurrence of curling. [Means for solving the problem]

[0010] The inventors conducted extensive research to solve the above problems and found that when an ethylene-unsaturated carboxylic acid copolymer is used as the resin layer of a laminate, the resin layer and the paper substrate are directly bonded even when the resin layer is thin, and the resulting laminate has high adhesive strength between the paper substrate and the resin layer, good paper peeling properties, and can suppress curling. That is, according to the present invention, the following laminates and the like are provided.

[0011] [1] A paper substrate; a resin layer provided adjacent to one or both sides of the paper substrate; A laminate comprising: The paper base material has a basis weight of 10 g / m 2 More than 100g / m 2 is less than the resin layer contains an ethylene-unsaturated carboxylic acid copolymer (A), The resin layer has a thickness of 1 μm or more and less than 20 μm, The laminate has a TD curl a and an MD curl a measured under the following measurement condition (a) of less than 10 mm. Measurement condition (a): A metal frame with a 10 cm square rectangular opening was prepared and placed on the resin layer side of the laminate so that each side of the rectangular opening was parallel to the flow direction (MD) during extrusion coating of the laminate and the direction perpendicular to the flow direction (TD). The laminate exposed to the rectangular opening was then cut along the diagonals of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as vertices and each side of the rectangular opening as base. The height from each vertex of the right-angled isosceles triangle to the resin layer side surface was measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the resin layer side surface was defined as TD curl a [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the resin layer side surface of the resin layer side was defined as MD curl a [mm]. [2] [1] The laminate according to the present invention, The laminate has a TD curl b and an MD curl b measured under the following measurement condition (b) of less than 10 mm. Measurement condition (b): A metal frame with a 10 cm square rectangular opening was prepared and placed on the paper substrate side of the laminate so that each side of the rectangular opening was parallel to the flow direction (MD) during extrusion coating of the laminate and the direction perpendicular to the flow direction (TD). The laminate exposed to the rectangular opening was then cut along the diagonals of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as vertices and each side of the rectangular opening as base. The height from each vertex of the right-angled isosceles triangle to the paper substrate side surface was measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the paper substrate side surface was defined as TD curl b [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the paper substrate side surface was defined as MD curl b [mm]. [3] In the laminate according to [1] or [2], A laminate containing 1% by mass or more and 25% by mass or less of structural units derived from an unsaturated carboxylic acid relative to all structural units of the copolymer constituting the ethylene-unsaturated carboxylic acid copolymer (A). [4] [1] to [3], wherein the laminate is The laminate is a paper substrate whose surface on the resin layer side is subjected to a corona treatment. [5] [1] to [4], wherein the laminate is The laminate wherein the resin layer is an extrusion coated layer. [6] A packaging material comprising at least a layer formed from the laminate according to any one of [1] to [5]. [7] [6] A package comprising the packaging material described in [6] and an item packaged in the packaging material. [8] A method for producing a laminate comprising a paper substrate and a resin layer provided adjacent to one or both sides of the paper substrate, The paper base material has a basis weight of 10 g / m 2 More than 100g / m 2 is less than the resin layer contains an ethylene-unsaturated carboxylic acid copolymer (A), the resin layer is a laminate having a thickness of 1 μm or more and less than 20 μm, A method for producing a laminate, comprising an extrusion step of forming the resin layer on the paper substrate by melt-extrusion coating the paper substrate with a resin composition that constitutes the resin layer. [Effects of the Invention]

[0012] According to the present invention, even if the resin layer is made thin, the resin layer and the paper substrate are directly bonded, and the resulting laminate has good adhesive strength between the paper substrate and the resin layer, making it possible to provide a laminate that can suppress curling. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 2 is a diagram schematically illustrating a cross section of the laminate of the present embodiment. [Figure 2] FIG. 2 is a schematic plan view illustrating a method for measuring curl. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the numerical range "X to Y" means X or more and Y or less unless otherwise specified.

[0015] 1. About laminates As shown in Fig. 1, the laminate 10 of this embodiment includes a paper substrate 1 and a resin layer 2 provided adjacent to one surface of the paper substrate 1. The paper substrate 1 has a basis weight of 10 g / m 2 More than 100g / m 2 The resin layer 2 contains an ethylene-unsaturated carboxylic acid copolymer (A) and has a thickness of 1 μm or more and less than 20 μm. The laminate 10 has a TD curl a and an MD curl a both of less than 10 mm, as measured under the following measurement condition (a). The TD curl a and the MD curl a are both preferably 7 mm or less, and more preferably 5 mm or less. Measurement condition (a): A metal frame having a rectangular opening measuring 10 cm square was prepared and placed on the surface of the laminate 10 facing the resin layer 2 so that each side of the rectangular opening was parallel to the flow direction (MD) of the laminate 10 during extrusion coating and the direction perpendicular to the flow direction (TD) during extrusion coating. The laminate 10 exposed in the rectangular opening was then cut along the diagonals of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as the vertex and each side of the rectangular opening as the base. The height from each vertex of the right-angled isosceles triangle to the surface facing the resin layer 2 was measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the surface facing the resin layer 2 was defined as TD curl a [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the surface facing the resin layer 2 was defined as MD curl a [mm].

[0016] However, TD curl a and MD curl a are the maximum values ​​among the six heights of the vertices of six right-angled triangles obtained by measuring at any three locations of the laminate 10 under measurement condition (a), and among the twelve right-angled triangles obtained, six right-angled isosceles triangles with bases parallel to the MD direction and six right-angled isosceles triangles with bases parallel to the TD direction. In addition, if the curl is more than 90° relative to the surface of the laminate 10, the height of the curl may be lower than the maximum height that the vertex of a right-angled isosceles triangle can assume. In this case, the curl is deemed to be too large, and the TD curl a and MD curl a cannot be measured.

[0017] 2(a), first, the surface of the laminate 10 on the side of the resin layer 2 is set as the upper surface, and a metal frame material 21 is placed on top of it. At this time, the metal frame material 21 is placed so that each side of the rectangular opening inside the metal frame material 21 is parallel to the flow direction (MD direction) of the laminate 10 during extrusion coating and the direction perpendicular to the flow direction (TD direction) during extrusion coating, respectively. Next, as shown in Fig. 2(b), the laminate 10 exposed in the rectangular opening is cut along the diagonals of the rectangular opening, thereby forming four right-angled isosceles triangles with the intersections of the diagonals as vertices and each side of the rectangular opening as a base. When the laminate has a tendency to curl, the apex of each right-angled isosceles triangle rises upward. Therefore, in this embodiment, the height from the apex of the right-angled isosceles triangle to the top surface of the laminate 10, i.e., the surface on the resin layer 2 side, is measured to evaluate the curl. The reason why conventional laminates tend to curl is that, in general, laminates produced by extrusion coating processing curl due to shrinkage associated with crystallization of the extruded resin when cooled, shrinkage of the substrate, or differences in tension (strain) between the substrates. In contrast, in the laminate 10 of this embodiment, curling can be suppressed when the ethylene-unsaturated carboxylic acid copolymer (A) is used. The inventors presume the reason for this as follows: The ethylene-unsaturated carboxylic acid copolymer (A) has low crystallinity and shrinks little when cooled after extrusion coating. In addition, it has excellent stress relaxation properties and is less likely to retain strain, which is thought to be why curling can be effectively suppressed.

[0018] According to the laminate 10 of this embodiment, even if the resin layer 2 is a thin film, the resin layer 2 and the paper base material 1 are directly bonded, and good adhesive strength is obtained between the paper base material 1 and the resin layer 2, which can suppress the occurrence of curling. Furthermore, the paper peeling state can be improved. That is, if the adhesive strength between the paper substrate 1 and the resin layer 2 is good, the paper peeling state is likely to be good. A good paper peeling state means that when an attempt is made to peel the laminate 10 from the surface on the paper substrate 1 side to the surface on the resin layer 2 side, the paper substrate 1 does not peel from the resin layer 2, but rather the paper substrate 1 is broken and peeled away from the resin layer 2. That is, because the paper substrate 1 and the resin layer 2 are bonded with good adhesive strength, the paper substrate 1 peels away from the resin layer 2 in a broken state before the adhesive strength between the paper substrate 1 and the resin layer 2 reaches a level at which peeling is possible. A paper peeling state in which the paper substrate 1 does not peel away from the resin layer 2 and the paper substrate 1 is broken and peeled away from the resin layer 2 is preferable, as this can avoid problems such as poor cutting when the laminate is subjected to secondary processing such as cutting, bending, and punching holes, or when used as a packaging material. In this embodiment, an example in which the resin layer 2 is provided adjacent to one surface of the paper base material 1 will be described, but the resin layer 2 may be provided adjacent to both surfaces of the paper base material 1.

[0019] In the laminate 10 of this embodiment, the paper base material 1 and the resin layer 2 are bonded together without the use of an adhesive containing an organic solvent, and are so-called direct bonded. The overall thickness of the laminate 10 can be set appropriately depending on the application of the laminate 10, but is preferably 15 μm or more and 250 μm or less, more preferably 30 μm or more and 200 μm or less, and even more preferably 50 μm or more and 150 μm or less.

[0020] Furthermore, the laminate 10 preferably has a TD curl b and an MD curl b measured under the following measurement condition (b) of less than 10 mm, more preferably 7 mm or less, and even more preferably 5 mm or less. Measurement condition (b): A metal frame with a 10 cm square rectangular opening was prepared and placed on the paper substrate 1 side of the laminate 10 so that each side of the rectangular opening was parallel to the flow direction (MD) of the laminate 10 during extrusion coating and the direction perpendicular to the flow direction (TD) during extrusion coating. The laminate 10 exposed to the rectangular opening was then cut along the diagonals of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as vertices and each side of the rectangular opening as bases. The height from each vertex of the right-angled isosceles triangle to the surface facing the paper substrate 1 was measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD as its base to the surface facing the paper substrate 1 was defined as TD curl b [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD as its base to the surface facing the paper substrate 1 was defined as MD curl b [mm].

[0021] However, TD curl b and MD curl b are the maximum values ​​among the six heights of the vertices of six right-angled triangles obtained by measuring at any three locations of the laminate 10 under measurement condition (b), for six right-angled isosceles triangles with bases parallel to the MD direction and six right-angled isosceles triangles with bases parallel to the TD direction, out of the 12 right-angled triangles obtained. In addition, if the curl is warped at an angle of more than 90° relative to the surface of the laminate 10, the height of the curl may be lower than the maximum height that the vertex of the right-angled isosceles triangle can assume. In this case, the curl is deemed to be too large, and the TD curl b and MD curl b cannot be measured. This allows the resin layer 2 to be directly bonded to the paper base material 1 even when the resin layer 2 is a thin film, and also provides better adhesive strength between the paper base material 1 and the resin layer 2, effectively suppressing curling. Furthermore, the paper peeling condition can be improved.

[0022] The above measurement conditions (a) and (b) are an ambient temperature of 23°C and a relative humidity of 50%RH. The cutting method is not particularly limited and can be a known method, such as a method using a cutter. The metal frame material 21 is used to fix the laminate 10. The metal frame material 21 is not particularly limited and can be any material that has a rectangular opening of 10 cm square, i.e., a square opening with a side length of 10 cm.

[0023] The laminate 10 that satisfies the above TD curl a, b and MD curl a, b can be realized by adjusting the basis weight of the paper substrate 1, the resin material and thickness of the resin layer 2, or the surface treatment, etc.

[0024] Each layer constituting the laminate 10 will be described in detail below.

[0025] <Paper base material> The paper substrate 1 has a basis weight of 10 g / m 2 More than 100g / m 2 less than 20 g / m 2 More than 80g / m 2 More preferably, it is 30 g / m or less. 2 More than 60g / m 2 The following is the result. By setting the basis weight of the paper base material 1 to the above lower limit or more, an appropriate strength of the laminate can be obtained. By setting the basis weight of the paper base material 1 to the above upper limit or less, the processability of the laminate can be improved, and curl resistance can be easily obtained.

[0026] The paper substrate 1 is not particularly limited as long as it satisfies the above-mentioned basis weight, and suitable materials include, but are not limited to, fine paper, pure white roll paper, coated paper, kraft paper, single-sided art paper, double-sided art paper, and mixed paper. Furthermore, a printed layer can be provided on the outer surface of the paper substrate 1 as needed.

[0027] The paper substrate 1 may be subjected to physical treatment such as corona treatment, plasma treatment, flame treatment, or ozone treatment on the surface adjacent to the resin layer 2. Of these, corona treatment is preferred, as this can increase adhesive strength. The paper substrate 1 may also be corona treated on one or both sides.

[0028] <Resin layer> The thickness of the resin layer 2 of this embodiment is 1 μm or more and less than 20 μm, preferably 3 μm or more and 15 μm or less, and more preferably 5 μm or more and 12 μm or less. By setting the thickness of the resin layer 2 to be equal to or greater than the above lower limit, it is possible to ensure good film formation during extrusion coating. On the other hand, by setting the thickness of the resin layer 2 to be equal to or less than the above upper limit, it is possible to reduce the amount of plastic used while maintaining adhesion to the paper substrate 1. It is also possible to improve curl resistance.

[0029] The surface of the resin layer 2 adjacent to the paper substrate 1 may be subjected to physical treatment such as corona treatment, plasma treatment, flame treatment, or ozone treatment. Of these, ozone treatment is preferred, as this can increase adhesive strength.

[0030] [Ethylene-unsaturated carboxylic acid copolymer (A)] The resin layer 2 contains an ethylene-unsaturated carboxylic acid copolymer (A), which provides adhesion to the paper substrate 1. It also makes it easier to achieve curl resistance.

[0031] The content of the ethylene-unsaturated carboxylic acid copolymer (A) in the resin layer 2 is preferably 70% by mass or more, more preferably 85% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, when the entire resin layer 2 is taken as 100% by mass, from the viewpoint of adhesiveness. The upper limit of the content of the ethylene-unsaturated carboxylic acid copolymer (A) is not particularly limited, but is, for example, 100% by mass. This makes it easier to obtain curl resistance.

[0032] The ethylene-unsaturated carboxylic acid copolymer is a polymer obtained by copolymerizing at least ethylene with a monomer selected from unsaturated carboxylic acids as copolymerization components, and if necessary, a monomer other than ethylene and an unsaturated carboxylic acid may also be copolymerized.

[0033] The copolymer may be a block copolymer, a random copolymer, or a graft copolymer. However, in consideration of productivity, it is preferable to use a binary random copolymer, a ternary random copolymer, a graft copolymer of a binary random copolymer, or a graft copolymer of a ternary random copolymer, and more preferably a binary random copolymer or a ternary random copolymer. The ethylene-unsaturated carboxylic acid copolymer (A) is preferably at least one selected from the group consisting of ethylene-unsaturated carboxylic acid copolymers and ethylene-unsaturated carboxylic acid alkyl ester-unsaturated carboxylic acid terpolymers.

[0034] The ethylene-unsaturated carboxylic acid copolymer (A) is a copolymer in which at least ethylene and an unsaturated carboxylic acid are copolymerized, and may also be a ternary or higher multi-component copolymer in which a third copolymer component is further copolymerized.

[0035] In the multicomponent copolymer, in addition to ethylene and (meth)acrylic acid copolymerizable with ethylene, as a third copolymerization component, unsaturated carboxylic acid esters (e.g., (meth)acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, dimethyl maleate, and diethyl maleate), vinyl esters (e.g., vinyl acetate and vinyl propionate), unsaturated hydrocarbons (e.g., propylene, butene, 1,3-butadiene, pentene, 1,3-pentadiene, and 1-hexene), oxides such as vinyl sulfate and vinyl nitrate, halogen compounds (e.g., vinyl chloride and vinyl fluoride), vinyl group-containing primary and secondary amine compounds, carbon monoxide, sulfur dioxide, and the like may be copolymerized. Among these, as the third copolymerization component, unsaturated carboxylic acid esters are preferred, and (meth)acrylic acid alkyl esters (the alkyl moiety preferably has 1 to 4 carbon atoms) are more preferred. The content ratio of the structural units derived from the third copolymerization component in the ethylene-(meth)acrylic acid copolymer is preferably in the range of 25 mass % or less. It is preferable from the standpoint of production and mixing that the content ratio of the constitutional units derived from the third copolymerization component is equal to or less than the above upper limit.

[0036] Examples of unsaturated carboxylic acids include unsaturated carboxylic acids or half esters having 4 to 8 carbon atoms, such as acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, maleic acid, maleic anhydride, maleic acid monoesters (monomethyl maleate, monoethyl maleate, etc.), and maleic anhydride monoesters (monomethyl maleate, monoethyl maleate, etc.). Among these, the unsaturated carboxylic acid preferably includes at least one selected from acrylic acid and methacrylic acid from the viewpoint of productivity of the ethylene-unsaturated carboxylic acid copolymer (A), etc. These unsaturated carboxylic acids may be used alone or in combination of two or more.

[0037] In the ethylene-unsaturated carboxylic acid copolymer (A) according to this embodiment, the content of structural units derived from ethylene is preferably 65% ​​by mass or more and 95% by mass or less, more preferably 75% by mass or more and 93% by mass or less, and even more preferably 80% by mass or more and 92% by mass or less.

[0038] In the ethylene-unsaturated carboxylic acid copolymer (A) according to this embodiment, the content of structural units derived from unsaturated carboxylic acids (i.e., the content X of unsaturated carboxylic acids) is preferably from 1 to 25% by mass, more preferably from 2 to 20% by mass, even more preferably from 3 to 15% by mass, and particularly preferably from 4 to 12% by mass.

[0039] The content (X) of unsaturated carboxylic acid in the ethylene-unsaturated carboxylic acid copolymer (A) can be measured, for example, by Fourier transform infrared absorption spectroscopy (FT-IR).

[0040] The method for producing the ethylene-unsaturated carboxylic acid copolymer (A) is not particularly limited, and it can be produced by a known method. Alternatively, commercially available ethylene-unsaturated carboxylic acid copolymer (A) may be used.

[0041] In this embodiment, the melt flow rate (MFR) of the ethylene-unsaturated carboxylic acid copolymer (A), measured in accordance with JIS K7210:1999 at 190°C under a load of 2160 g, is preferably 0.1 g / 10 min to 50 g / 10 min, more preferably 1 g / 10 min to 30 g / 10 min, and even more preferably 2 g / 10 min to 20 g / 10 min. When the MFR is within the above range, processability is further improved.

[0042] [others] The resin layer 2 may contain components other than the ethylene-unsaturated carboxylic acid copolymer (A) as long as the object of the present invention is not impaired. These other components are not particularly limited, but may include, for example, plasticizers, antioxidants, UV absorbers, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, thermoplastic resins other than the ethylene-unsaturated carboxylic acid copolymer (A), thermosetting resins, inorganic fillers, organic fillers, impact modifiers, slip agents, crosslinking agents, crosslinking aids, tackifiers, silane coupling agents, processing aids, mold release agents, hydrolysis inhibitors, heat stabilizers, antiblocking agents, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, dispersants, and other resins. These other components may be used singly or in combination of two or more.

[0043] The resin layer 2 of this embodiment is composed of a resin composition containing an ethylene-unsaturated carboxylic acid copolymer (A) and other components. A suitable method for producing the resin layer 2 of this embodiment is extrusion lamination, in which the resin composition is melted, as will be described later in connection with the method for producing the laminate 10. In this case, the resin layer 2 is an extrusion coated layer.

[0044] <Other layers> The laminate 10 may be composed of only a paper base material 1 and a resin layer 2, or may have layers other than those mentioned above (hereinafter also referred to as other layers) in order to impart various functions to the laminate 10. Examples of the other layers include a barrier layer, a sealant layer, a foam layer, an inorganic layer, a hard coat layer, an anti-reflection layer, and an anti-fouling layer, etc. The other layers may be used singly or in combination of two or more.

[0045] <Application> The laminate 10 of this embodiment can be suitably used as a packaging material for packaging food, medicines, industrial products, daily necessities, cosmetics, and the like.

[0046] <Manufacturing method> The method for producing the laminate 10 includes at least an extrusion step of melt-extrusion coating a resin composition that constitutes the resin layer 2 onto the paper base material 1 to form the resin layer 2 on the paper base material 1. In other words, the resin layer 2 of the laminate 10 is preferably an extrusion coated layer formed by an extrusion coating method. When the extrusion coating method is used, the resin temperature during molding can be increased compared to other film-forming methods, and the resin composition containing the ethylene-unsaturated carboxylic acid copolymer (A) can be coated in a molten state onto the paper substrate 1, resulting in a good laminated state. That is, according to the method for manufacturing the laminate 10 according to this embodiment, the resin layer 2 can be formed on the paper base material 1 with high accuracy and stability.

[0047] The molding device and molding conditions in the extrusion step are not particularly limited, and conventionally known molding devices and molding conditions can be used. Examples of molding devices that can be used include T-die extruders. Furthermore, molding conditions used in known extrusion coating methods can be used.

[0048] In the method for producing the laminate 10, the extrusion coating temperature in the extrusion step is not particularly limited, as it is appropriately set depending on the type and composition of the ethylene-unsaturated carboxylic acid copolymer (A). From the viewpoint of improving film-forming properties, however, it is preferably 200°C or higher, more preferably 250°C or higher, and even more preferably 280°C or higher. The upper limit of the extrusion coating temperature in the extrusion step is not particularly limited, but is, for example, 350°C or lower.

[0049] 2. Packaging material The packaging material according to this embodiment includes a layer formed of the above-described laminate 10. The packaging material according to this embodiment may use the laminate 10 in a part thereof, or may use the laminate 10 in the entire packaging material. The shape of the packaging material according to the present embodiment is not particularly limited, but examples thereof include a sheet, a film, a bag, etc. The shape of the bag is also not particularly limited, but examples thereof include a three-sided bag, a four-sided bag, a pillow bag, a gusset bag, and a stick bag. The packaging material according to this embodiment can be suitably used as a packaging material for packaging, for example, food, pharmaceuticals, industrial products, daily necessities, cosmetics, etc., and can be even more suitably used as a food packaging material.

[0050] 3.Packaging The package according to this embodiment includes the packaging material and an article packaged in the packaging material, such as food, medicine, industrial products, daily necessities, and cosmetics.

[0051] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. [Example]

[0052] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0053] (1) Laminate material The melt flow rate (MFR) was measured in accordance with JIS K7210:1999. <Paper base material> Kraft paper (manufactured by Taiko Paper Co., Ltd., basis weight 50 g / m 2 , thickness 60 μm) High-quality paper (Kishu Paper Co., Ltd., basis weight 52 g / m 2 , thickness 63 μm) <Ethylene-unsaturated carboxylic acid copolymer> Ethylene-acrylic acid copolymer 1 (ethylene unit content 95% by mass, acrylic acid unit content 5% by mass, MFR (190°C, 2160g load) 8g / 10min, density 930kg / m 3 ) Ethylene-acrylic acid copolymer 2 (ethylene unit content 90% by mass, acrylic acid unit content 10% by mass, MFR (190°C, 2160g load) 10g / 10min, density 940kg / m 3 ) Ethylene-methacrylic acid copolymer 1 (ethylene unit content 89% by mass, methacrylic acid unit content 11% by mass, MFR (190°C, 2160g load) 8g / 10min, density 940kg / m 3 ) <Other resins> LDPE1: Low-density polyethylene (MFR (190°C, 2160g load) 7.2g / 10min, density 917kg / m 3 ) LDPE2: Low-density polyethylene (MFR (190°C, 2160g load) 23g / 10min, density 923kg / m 3 )

[0054] (2) Fabrication and evaluation of laminates Using the materials in (1) above, a laminate was produced in the following procedure.

[0055] Example 1 Using an extrusion laminator with a 65 mm diameter extruder (L / D = 28), kraft paper (paper substrate: basis weight 50 g / m) was laminated under the following processing conditions: die temperature 310°C, air gap 120 mm, processing speed 120 m / min, processing width 500 mm. 2 ) on one side, in-line corona treatment (115W·min / m 2 After that, a molten film of ethylene-acrylic acid copolymer 1 was extruded to form an extrusion coating to prepare a laminate (resin layer thickness: 10 μm). The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0056] <Example 2> Immediately after the molten film was extruded, the surface of the molten film that was in contact with the kraft paper was treated with ozone (25 g / m 2 1m 3 / m 2 A laminate was produced by extrusion coating in the same manner as in Example 1, except that the coating was performed using the same material as in Example 1. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0057] Example 3 A laminate was produced by extrusion coating in the same manner as in Example 1, except that ethylene-acrylic acid copolymer 2 was used as the melt film. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0058] Example 4 A laminate was produced by extrusion coating in the same manner as in Example 2, except that ethylene-acrylic acid copolymer 2 was used as the melt film. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0059] <Example 5> A laminate was produced by extrusion coating in the same manner as in Example 1, except that the temperature below the die was set to 288°C and ethylene-methacrylic acid copolymer 1 was used as the molten film. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0060] Example 6 A laminate was produced by extrusion coating in the same manner as in Example 2, except that the temperature below the die was set to 288°C and ethylene-methacrylic acid copolymer 1 was used as the molten film. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0061] <Comparative Example 1> A laminate was produced by extrusion coating in the same manner as in Example 1, except that the thickness of the resin layer was 20 μm. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0062] <Comparative Example 2> A laminate was produced by extrusion coating in the same manner as in Example 3, except that the thickness of the resin layer was 20 μm. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0063] <Comparative Example 3> A laminate was produced by extrusion coating in the same manner as in Example 5, except that the thickness of the resin layer was 20 μm. The obtained laminate was subjected to the following evaluation (3). The evaluation results are shown in Table 1.

[0064] <Comparative Example 4> Except for using LDPE1 as the melt film, extrusion coating was carried out in the same manner as in Example 1. However, the melt film was cut, and a laminate could not be produced.

[0065] <Comparative Example 5> Immediately after the molten film was extruded, the surface of the molten film that was in contact with the kraft paper was treated with ozone (25 g / m 2 1m 3 / m 2 Extrusion coating was carried out in the same manner as in Comparative Example 4, except that the molten film was subjected to the above-mentioned step 1. However, the molten film was cut, and a laminate could not be produced.

[0066] <Comparative Example 6> A laminate was produced by extrusion coating in the same manner as in Example 1, except that the temperature below the die was 307°C and LDPE2 was used as the molten film. The obtained laminate was used to evaluate the following (3). However, for the evaluation of adhesive strength, the adhesive strength was too low, so a sample for measuring adhesive strength could not be prepared. The evaluation results are shown in Table 1.

[0067] <Comparative Example 7> Immediately after the molten film was extruded, the surface of the molten film that was in contact with the kraft paper was treated with ozone (25 g / m 2 1m 3 / m 2 A laminate was produced by extrusion coating in the same manner as in Comparative Example 6, except that 1) was additionally applied. Using the obtained laminate, the evaluation in (3) below was performed. The evaluation results are shown in Table 1. However, since the adhesive strength was too low, a sample for measuring the adhesive strength could not be prepared.

[0068] (3) Evaluation [Workability] The workability of the laminate was evaluated according to the following criteria. (Criteria) A: During the processing of the laminate, the molten film could be laminated on the paper substrate, and a laminate could be produced. B: During the processing of the laminate, the molten film was cut and could not be laminated onto the paper substrate, and a laminate could not be produced.

[0069] [Adhesive strength] After the obtained laminate was allowed to stand and stored in an atmosphere of 23°C and 50% RH for 7 days, the adhesive strength [N / 15 mm] between the resin layer and the paper substrate was measured under the following conditions using a peel strength tester (manufactured by Intesco Co., Ltd., IM-20X-ST type tensile tester). Note that the adhesive strength [N / 15 mm] is preferably 0.7 N / 15 mm or more as a practical standard when used as a packaging material. <于 (Conditions) <于 · Shape: Strip with a width of 15 mm in the machine direction (MD direction) <于 · Peel speed: 300 mm / min <于 ]· Peel angle: T peel <于 <于

[0070] <于 [Paper peeling state] <于 The laminate after measuring the adhesive strength used above (a sample in which the resin layer and the paper substrate were peeled off) was observed with a microscope by a skilled technician. The paper peeling state was evaluated according to the following criteria. <于 (Criteria) <于 A: Peeling occurred without peeling between the paper substrate and the resin layer, and the paper substrate was broken (paper peeling). <于 B: Peeling occurred between the paper substrate and the resin layer. <于 <于

[0071] <于 [Anti-curling property] <于 <TD curl a and MD curl a; surface of the resin layer> <于 · For each of the obtained laminates, TD curl a and MD curl a were measured according to the following measurement conditions (a). Measurement conditions (a): A metallic frame material having a rectangular opening of 10 cm square was prepared, and each side of the rectangular opening was arranged on the surface of the resin layer side of the laminate so as to be parallel to the flow direction (MD direction) during the extrusion coating of the laminate and the direction perpendicular to the flow direction during the extrusion coating (TD direction), respectively. Subsequently, the laminate exposed in the rectangular opening was cut on the diagonal line of the rectangular opening, and four right-angled isosceles triangles were formed with the intersection of the diagonal lines as the apex and each side of the rectangular opening as the base. The height from each apex of the right-angled isosceles triangle to the surface of the resin layer side was measured. The measurement was carried out at three arbitrary positions of the laminate, and six data points were obtained for the height from the apex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the surface of the resin layer side and the height from the apex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the surface of the resin layer side, respectively. The maximum value among the six data points of the height from the apex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the surface of the resin layer side was defined as TD curl a [mm], and the maximum value among the six data points of the height from the apex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the surface of the resin layer side was defined as MD curl a [mm]. In addition, when the curl warps more than 90° with respect to the surface of the laminate, it may occur that the height of the curl becomes lower than the maximum height that the apex of the right-angled isosceles triangle can take. In that case, it was determined that the curl was too large, and the measurement of TD curl a and MD curl a was not possible. However, among the examples and comparative examples, there was no case where the measurement was not possible.

[0072] <TD curl b and MD curl b; surface of paper substrate> · For each of the obtained laminates, TD curl b and MD curl b were measured according to the following measurement conditions (b). Measurement condition (b): A metal frame with a 10 cm square rectangular opening was prepared and placed on the paper substrate side of the laminate so that each side of the rectangular opening was parallel to the flow direction (MD) during extrusion coating of the laminate and the direction perpendicular to the flow direction (TD). The laminate exposed to the rectangular opening was then cut along the diagonal of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as the vertex and each side of the rectangular opening as the base. The height from each vertex of the right-angled isosceles triangle to the paper substrate side surface was measured. The measurement was performed at three random locations on the laminate, and six data points were obtained for the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD as the base to the surface, and the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD as the base to the surface on the resin layer side. The maximum value of the height from the vertex of the right-angled isosceles triangle with a base parallel to the MD direction to the surface on the paper substrate side among six points was defined as TD curl b [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with a base parallel to the TD direction to the surface on the paper substrate side among six points was defined as MD curl b [mm]. In addition, when the curl is warped at an angle of more than 90° relative to the surface of the laminate, the height of the curl may be lower than the maximum height that the apex of a right-angled isosceles triangle can assume, in which case the curl is judged to be too large and the TD curl b and MD curl b cannot be measured. However, there were no examples and comparative examples in which the measurements were impossible.

[0073] [Table 1]

[0074] (4) Fabrication and evaluation of laminates Using the materials in (1) above, a laminate was produced in the following procedure.

[0075] Example 7 As the paper base material, high-quality paper (basis weight 52 g / m 2A laminate was produced by extrusion coating in the same manner as in Example 1, except that 1) was used. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0076] Example 8 A laminate was produced by extrusion coating in the same manner as in Example 2, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0077] Example 9 A laminate was produced by extrusion coating in the same manner as in Example 3, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0078] Example 10 A laminate was produced by extrusion coating in the same manner as in Example 4, except that high-quality paper was used as the paper substrate.

[0079] Example 11 A laminate was produced by extrusion coating in the same manner as in Example 5, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0080] <Comparative Example 8> A laminate was produced by extrusion coating in the same manner as in Comparative Example 1, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0081] <Comparative Example 9> A laminate was produced by extrusion coating in the same manner as in Comparative Example 2, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0082] <Comparative Example 10> A laminate was produced by extrusion coating in the same manner as in Comparative Example 3, except that high-quality paper was used as the paper substrate. The obtained laminate was subjected to the evaluation (3) above. The evaluation results are shown in Table 2.

[0083] <Comparative Example 11> Except for using high-quality paper as the paper substrate, extrusion coating was carried out in the same manner as in Comparative Example 4. However, the molten film was cut, and a laminate could not be produced.

[0084] <Comparative Example 12> Except for using high-quality paper as the paper substrate, extrusion coating was carried out in the same manner as in Comparative Example 5. However, the molten film was cut, and a laminate could not be produced.

[0085] <Comparative Example 13> A laminate was produced by extrusion coating in the same manner as in Comparative Example 6, except that high-quality paper was used as the paper substrate. The obtained laminate was used to carry out the evaluation of (3) above. However, the adhesive strength was too low to prepare a sample for measuring the adhesive strength. The evaluation results are shown in Table 2.

[0086] [Table 2]

[0087] In Examples 1 to 11, the processability was good, and the resulting laminates exhibited sufficient adhesive strength and good peeling, with little curling. In contrast, in Comparative Examples 1 to 3 and 8 to 10, the processability was good, and the resulting laminates exhibited sufficient adhesive strength and good peeling, but curling was significant. In Comparative Examples 4 to 5 and 11 to 12, the molten film was cut during processing of the laminate, making it impossible to laminate it onto the paper substrate, and no laminates could be produced. In Comparative Examples 6 to 7 and 13, laminates could be produced and curling was minimal, but the adhesive strength between the paper substrate and the resin layer was low, and they did not exhibit high adhesive strength or good peeling. [Explanation of symbols]

[0088] 10 Laminate 1 Paper base material 2 Resin layer 21 Metal frame material

Claims

1. A paper substrate; a resin layer provided adjacent to one or both sides of the paper substrate; a laminate comprising: (however, excluding a laminate comprising an aluminum foil, in which a paper base material and the aluminum foil are bonded via a resin layer, and a hologram metal vapor deposition laminate comprising: a base layer; a hologram-forming resin layer made of a copolymer resin of ethylene and an ethylenically unsaturated carboxylic acid, the hologram being formed on the surface opposite to the base layer laminated on the base layer; and a metal vapor deposition layer provided on the hologram-forming resin layer), The paper substrate has a basis weight of 10 g / m ２ More than 100g / m ２ is less than the resin layer contains an ethylene-unsaturated carboxylic acid copolymer (A), The ethylene-unsaturated carboxylic acid copolymer (A) is a polymer (excluding ionomers) obtained by copolymerizing at least ethylene and a monomer selected from unsaturated carboxylic acids as copolymerization components, the content of the ethylene-unsaturated carboxylic acid copolymer (A) in the resin layer is 70% by mass or more when the entire resin layer is taken as 100% by mass, the melt flow rate (MFR) of the ethylene-unsaturated carboxylic acid copolymer (A), measured in accordance with JIS K7210:1999 at 190°C under a load of 2160 g, is 0.1 g / 10 min or more and 50 g / 10 min or less; The resin layer has a thickness of 1 μm or more and 12 μm or less, the resin layer is an extrusion coating layer, A laminate comprising the paper base material and the resin layer disposed adjacent to the paper base material, wherein the TD curl a and MD curl a measured under the following measurement condition (a) are both less than 10 mm. Measurement condition (a): A metal frame having a rectangular opening measuring 10 cm square is prepared, and the rectangular opening is placed on the resin layer side of the laminate so that each side of the rectangular opening is parallel to the flow direction (MD direction) during extrusion coating of the laminate and the direction perpendicular to the flow direction (TD direction) during extrusion coating. The laminate exposed to the rectangular opening is then cut along the diagonal of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonal lines as vertices and each side of the rectangular opening as base. The height from each vertex of the right-angled isosceles triangle to the resin layer side surface is measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the resin layer side surface is defined as TD curl a [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the resin layer side surface is defined as MD curl a [mm].

2. The laminate according to claim 1 , A laminate comprising the paper base material and the resin layer provided adjacent to the paper base material, wherein the TD curl b and MD curl b measured under the following measurement condition (b) are both less than 10 mm. Measurement condition (b): A metal frame having a rectangular opening measuring 10 cm square is prepared, and the rectangular opening is placed on the paper substrate side of the laminate so that each side of the rectangular opening is parallel to the flow direction (MD direction) during extrusion coating of the laminate and the direction perpendicular to the flow direction (TD direction) during extrusion coating. The laminate exposed to the rectangular opening is then cut along the diagonals of the rectangular opening to form four right-angled isosceles triangles with the intersection of the diagonals as vertices and each side of the rectangular opening as base. The height from each vertex of the right-angled isosceles triangle to the paper substrate side surface is measured, and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the MD direction as the base to the paper substrate side surface is defined as TD curl b [mm], and the maximum value of the height from the vertex of the right-angled isosceles triangle with the side parallel to the TD direction as the base to the paper substrate side surface is defined as MD curl b [mm].

3. The laminate according to claim 1 or 2, A laminate comprising 1% by mass or more and 25% by mass or less of structural units derived from an unsaturated carboxylic acid relative to all structural units of the copolymer constituting the ethylene-unsaturated carboxylic acid copolymer (A).

4. The laminate according to any one of claims 1 to 3, The surface of the paper substrate facing the resin layer is subjected to a corona treatment.

5. A packaging material comprising at least a layer formed from the laminate according to any one of claims 1 to 4.

6. A package comprising the packaging material according to claim 5 and an article packaged in the packaging material.

7. A method for producing a laminate comprising a paper base material and a resin layer provided adjacent to one or both surfaces of the paper base material (excluding a laminate comprising aluminum foil in which the paper base material and the aluminum foil are bonded via a resin layer, and a hologram metal vapor deposition laminate characterized by comprising a base material layer, a hologram-forming resin layer made of a copolymer resin of ethylene and an ethylenically unsaturated carboxylic acid, with a hologram formed on the surface opposite to the base material layer laminated on the base material layer, and a metal vapor deposition layer provided on the hologram-forming resin layer), comprising: The paper substrate has a basis weight of 10 g / m ２ More than 100g / m ２ is less than the resin layer contains an ethylene-unsaturated carboxylic acid copolymer (A), The ethylene-unsaturated carboxylic acid copolymer (A) is a polymer (excluding ionomers) obtained by copolymerizing at least ethylene and a monomer selected from unsaturated carboxylic acids as copolymerization components, the content of the ethylene-unsaturated carboxylic acid copolymer (A) in the resin layer is 70% by mass or more when the entire resin layer is taken as 100% by mass, the melt flow rate (MFR) of the ethylene-unsaturated carboxylic acid copolymer (A), measured in accordance with JIS K7210:1999 at 190°C under a load of 2160 g, is 0.1 g / 10 min or more and 50 g / 10 min or less; the resin layer is a laminate having a thickness of 1 μm or more and 12 μm or less, the resin layer is an extrusion coating layer, A method for producing a laminate, comprising an extrusion step of forming the resin layer on the paper substrate by melt-extrusion coating the paper substrate with a resin composition that constitutes the resin layer.

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