Laminate

Abstract

To provide a laminate with excellent easy tearability.SOLUTION: A laminate 10 for forming a wrapping bag comprises a substrate layer 1 including a crystalline polyester film, an adhesion layer 2, and a sealant layer 3 including a polyester film in this order, where the thickness of the sealant layer 3 is 15 to 100 μm, the sealant layer 3 has a value 13% / μm or less which is obtained by dividing a rupture elongation in an MD direction measured in 15 mm width by thickness, and a draw ratio of the polyester film included in the sealant layer 3 is 1.1 times or more in the MD direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate, and more particularly to a laminate for forming a packaging bag. [Background technology]

[0002] For example, for packaging bags used for packaging food, a laminate (soft packaging material) is known that comprises a biaxially oriented PET (polyethylene terephthalate) film, which has excellent heat resistance and toughness, as a base film and a polyolefin film such as polyethylene or polypropylene as a sealant layer (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-178357 [Patent Document 2] Patent No. 5933309 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the trend toward universal design, consumer considerations are being sought for packaging bags as well, and for example, it is desirable to use laminates with easy tearability as packaging bags that are easy to open. However, laminates used in conventional packaging bags still have room for improvement in terms of easy tearability.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a laminate having easy tearability. [Means for solving the problem]

[0006] The present invention provides a laminate for forming a packaging bag, comprising, in this order, a substrate layer containing a crystalline polyester film, an adhesive layer, and a sealant layer containing a polyester film, wherein the sealant layer has a MD breaking elongation measured over a 15 mm width divided by the thickness of the sealant layer of 13% / μm or less.

[0007] The sealant layer may have a planar orientation coefficient of 0.08 or less.

[0008] The substrate layer may have a vapor-deposited layer of an inorganic oxide on at least one surface.

[0009] The laminate has a water vapor permeability of 10 g / m 2 · days or less may be used.

[0010] The laminate has an oxygen permeability of 5 cc / m 2 · days or less may be used.

[0011] The laminate may have a total mass of polyester components of 90% by mass or more based on the total mass of the laminate. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a laminate having easy tearability. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a laminate according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings where necessary, but the present invention is not limited to the following embodiments.

[0015] <Laminate> 1 is a schematic cross-sectional view of a laminate according to one embodiment. The laminate 10 according to one embodiment includes a base layer 1, an adhesive layer 2, and a sealant layer 3 in this order.

[0016] [Base material layer] The substrate layer is a film (base film) that serves as a support and includes a crystalline polyester film. The substrate layer may be made of a crystalline polyester film. The crystalline polyester film may be a stretched film or a non-stretched film.

[0017] The crystalline polyester can be obtained, for example, by polycondensing a diol and a dicarboxylic acid.

[0018] Examples of diols include aliphatic diols and alicyclic diols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, neopentyl glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. These compounds may be used alone or in combination of two or more. Biomass-derived ethylene glycol may also be used.

[0019] Examples of dicarboxylic acids include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, isophthalic acid, terephthalic acid, n-dodecylsuccinic acid, n-dedecenylsuccinic acid, cyclohexanedicarboxylic acid, and anhydrides or lower alkyl esters of these acids. These compounds may be used alone or in combination of two or more.

[0020] In order to fully exhibit the function as a base layer of a packaging material, polybutylene terephthalate, polybutylene naphthalate, polyethylene terephthalate, etc. can be used as the crystalline polyester.

[0021] The base layer may contain recycled polyester from the viewpoint of reducing the environmental load. Examples of recycled polyester include chemically recycled polyester obtained by chemically recycling a container made of polyester mainly composed of ethylene terephthalate units, and mechanically recycled polyester obtained by mechanically recycling a container made of polyester mainly composed of ethylene terephthalate units.

[0022] The substrate layer may have a vapor-deposited layer of an inorganic oxide on at least one surface to improve gas barrier properties against, for example, water vapor and oxygen. By using a vapor-deposited layer of an inorganic oxide, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the laminate. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoint of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. The thickness of the vapor-deposited layer of the inorganic oxide can be, for example, 5 nm to 100 nm, and may be 10 nm to 50 nm. A thickness of 5 nm or more facilitates the exertion of good barrier properties, while a thickness of 100 nm or less facilitates the maintenance of flexibility of the laminate. The vapor-deposited layer can be formed, for example, by physical vapor deposition, chemical vapor deposition, or the like.

[0023] The substrate layer may include a film other than a crystalline polyester film, or may include multiple layers of crystalline polyester film. When the substrate layer includes multiple layers of crystalline polyester film, the crystalline polyester films may be the same or different. When the substrate layer includes multiple layers of crystalline polyester film, at least one of the polyester films may have a vapor-deposited layer of an inorganic oxide on its surface.

[0024] The thickness of the substrate layer can be, for example, 5 μm to 1 mm, or may be 5 to 800 μm, or may be 5 to 500 μm. When the substrate layer includes a plurality of the above films, the total thickness thereof may be within the above range.

[0025] [Adhesive layer] Examples of adhesive components of the adhesive layer include two-component curing polyurethane adhesives in which a base agent such as polyester polyol, polyether polyol, or acrylic polyol is reacted with a difunctional or higher aromatic or aliphatic isocyanate compound as a curing agent.

[0026] The adhesive layer can be formed by coating the adhesive component onto the base layer and then drying. When using a polyurethane adhesive, aging the coating for at least four days at 40°C, for example, will promote the reaction between the hydroxyl groups of the base material and the isocyanate groups of the curing agent, resulting in strong adhesion.

[0027] The thickness of the adhesive layer can be set to 2 to 50 μm, and may be 3 to 20 μm, from the viewpoints of adhesiveness, followability, processability, and the like.

[0028] [Sealant layer] The sealant layer is a layer that provides heat sealing to the laminate and includes a polyester film. The sealant layer may include a plurality of polyester films or may be made of a polyester film.

[0029] In this embodiment, the sealant layer has a value of 13% / μm or less, calculated by dividing the MD breaking elongation measured over a 15 mm width by the thickness. By using a sealant layer with this value of 13% / μm or less, elongation due to the viscosity of the resin is less likely to occur when the laminate is torn apart, and as a result, the tear strength of the laminate can be reduced. From this perspective, the sealant layer preferably has a value of 12% / μm or less, and more preferably 11% / μm or less, calculated by dividing the MD breaking elongation measured over a 15 mm width by the thickness. The lower limit of the value of MD breaking elongation measured over a 15 mm width by the thickness is not particularly limited, but may be, for example, 0.1% / μm or more.

[0030] The breaking elongation can be adjusted by the material of the film constituting the sealant layer, the stretching ratio during film formation, etc. The stretching ratio during film formation can be appropriately changed depending on the material of the film, etc., and may be, for example, 1.1 times or more, or 1.5 times or more in the MD direction. The upper limit of the stretching ratio is not particularly limited, and may be, for example, 6 times or less in the MD direction.

[0031] Furthermore, the planar orientation coefficient of the sealant layer is preferably 0.08 or less. Generally, films tend to tear easily in the orientation direction but not in directions other than the orientation direction. Therefore, in the case of a laminate in which two or more oriented films are bonded together, tearing may be hindered by delamination between the films during tearing, resulting in increased splitting. "Splitting" refers to the phenomenon in which misalignment occurs between the cut edges (tear lines) of two or more films when they are torn simultaneously. If the planar orientation coefficient of the sealant layer is 0.08 or less, the influence of the orientation of the sealant layer is reduced when the laminate is torn, thereby suppressing splitting. From this perspective, the planar orientation coefficient of the sealant layer is more preferably 0.05 or less, and even more preferably 0.01 or less. The lower limit of the planar orientation coefficient of the sealant layer is not particularly limited, but may be, for example, 0 or more, or 0.001 or more.

[0032] The polyester film contained in the sealant layer can be obtained, for example, by condensation polymerization of diols and dicarboxylic acids. Examples of diols and dicarboxylic acids include the compounds exemplified for the base layer. The polyester film can be obtained, for example, by extruding a polyester film-forming resin containing diols and dicarboxylic acids by a casting method or the like, and then stretching the resin in the film transport direction at a desired stretch ratio.

[0033] In order to fully exhibit the function as a sealant layer of the packaging material, the polyester may be polybutylene terephthalate, polybutylene naphthalate, polyethylene terephthalate, or the like.

[0034] The sealant layer may contain recycled polyester resin from the viewpoint of reducing the environmental load. Examples of recycled polyester resin include chemically recycled polyester resin obtained by chemically recycling a container made of a polyester resin mainly composed of ethylene terephthalate units, and mechanically recycled polyester resin obtained by mechanically recycling a container made of a polyester resin mainly composed of ethylene terephthalate units.

[0035] The polyester film constituting the sealant layer may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0036] From the viewpoint of seal strength, the thickness of the sealant layer may be 15 to 100 μm, or 20 to 60 μm. If the thickness of the sealant layer is less than 15 μm, the seal strength tends to be insufficient depending on the size of the laminate and the amount of contents. In addition, the mass ratio of the adhesive and ink in the laminate tends to be high. When the sealant layer includes multiple layers of polyester film, the total thickness may be within the above range.

[0037] The water vapor permeability of the laminate is, for example, 10 g / m 2 The oxygen permeability of the laminate can be, for example, 5 cc / m 2 This protects the contents from deterioration due to water vapor and oxygen, making it easier to maintain quality over the long term. From this perspective, the water vapor permeability should be 7.5 g / m 2 -day or less, 5g / m 2 ・day or less, 1g / m 2 ・day or less, 0.5g / m 2 ·day or less. The oxygen permeability is 4cc / m 2 · day or less, 3cc / m 2 · day or less, 0.5cc / m 2 · day or less, 0.2cc / m 2 ·day or less is acceptable.

[0038] The laminate preferably comprises a polyester component as its main component. In other words, it is preferable that at least a portion of the constituent films of the laminate be polyester film, and it is more preferable that substantially all of the constituent films of the laminate be polyester film. Such a laminate can be called a monomaterial laminate consisting essentially of a single material, and packaging bags formed from such a laminate are expected to have excellent recyclability. Here, a laminate comprising a polyester component as its main component refers to a laminate in which the total mass of the polyester component exceeds 50% by mass, based on the total mass of the laminate. From the viewpoint of recyclability, the total mass of the polyester component may be, for example, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 92.5% by mass or more, or 95% by mass or more, based on the total mass of the laminate.

[0039] Examples of the polyester component include the crystalline polyester film contained in the base layer and the polyester film contained in the sealant layer. Examples of components other than polyester include the adhesive component in the adhesive layer and the ink component.

[0040] The laminate can be suitably used to form a packaging bag for packaging contents, such as liquids such as liquid seasonings, toiletries, soups, and liquid detergents, solids such as simmered dishes, and solid-liquid mixtures of liquids and solids such as curry. The laminate has easy tearability, making it possible to form an easily openable packaging bag.

[0041] A packaging bag can be obtained by heat-sealing the sealant layers of a laminate with the sealant layers facing each other. For example, a packaging bag can be obtained by heat-sealing three sides of the laminate with the sealant layers facing each other. A package can be obtained by filling the contents into the packaging bag and sealing the packaging bag. For example, a package can be obtained by filling the contents from the remaining side that is not heat-sealed, and then finally heat-sealing the remaining side. [Example]

[0042] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0043] [Preparation of polyester film for sealant layer] Resins 1 and 2 for polyester film formation were prepared using the monomers listed in Table 1 as starting materials. In the table, TPA stands for terephthalic acid, EG stands for ethylene glycol, NPG stands for neopentyl glycol, BDO stands for 1,4-butanediol, DEG stands for diethylene glycol, and CHDM stands for 1,4-cyclohexanedimethanol, and the values ​​in the table are in mol%.

[0044] [Table 1]

[0045] Polyester film A: The resin 1 obtained above was extruded by a casting method and then stretched in the film machine direction (hereinafter referred to as "MD") at a stretch ratio of 2 to obtain a polyester film A. The thickness after stretching was 30 μm.

[0046] Polyester film B: Polyester film B was obtained in the same manner as polyester film A, except that the stretching ratio was 1.1 times. The thickness after stretching was 30 μm.

[0047] Polyester film C: Polyester film C was obtained in the same manner as polyester film A, except that the thickness after stretching was 50 μm.

[0048] Polyester film D: Polyester film D was obtained in the same manner as polyester film A, except that the stretching ratio was 3. The thickness after stretching was 30 μm.

[0049] Polyester film E: Polyester film E was obtained in the same manner as polyester film B, except that resin 1 was changed to resin 2. The thickness after stretching was 30 μm.

[0050] (Measurement of breaking elongation of polyester film) The breaking elongation in the MD direction of the polyester film was measured in accordance with JIS K 7127. The width of the test piece was 15 mm, the initial distance between the chucks was 100 mm, and the test speed was 300 mm / min.

[0051] (Measurement of Planar Orientation Coefficient of Polyester Film) The plane orientation coefficient of the polyester film was measured and calculated as follows. First, the refractive index was measured in accordance with JIS K7142 "Plastics - Determination of refractive index" (Method A). The measuring instrument used was a KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. The refractive index in the longitudinal direction (nx), width direction (ny), and thickness direction (nz) of the film were each measured, and the plane orientation coefficient (ΔP) was calculated using the following formula. ΔP=(nx+ny) / 2-nz

[0052] [Laminate fabrication] Example 1 A 12 μm thick stretched PET film, a crystalline polyester film oriented at 30° to the MD direction, was prepared as the base film. This stretched PET film and polyester film A were bonded together by dry lamination to obtain a laminate. A general urethane resin adhesive was used as the adhesive for dry lamination. The amount of the urethane resin adhesive applied after drying was 3 g / m. 2 The thickness was adjusted to 3 μm.

[0053] Example 2 A laminate was obtained in the same manner as in Example 1, except that the polyester film B was used instead of the polyester film A.

[0054] Example 3 A laminate was obtained in the same manner as in Example 1, except that the polyester film C was used instead of the polyester film A.

[0055] Example 4 A laminate was obtained in the same manner as in Example 1, except that Polyester Film D was used instead of Polyester Film A.

[0056] Example 5 A laminate was obtained in the same manner as in Example 1, except that the polyester film E was used instead of the polyester film A.

[0057] Example 6 A laminate was obtained in the same manner as in Example 1, except that a silica vapor-deposited film was provided as a barrier layer on one surface of a stretched PET film serving as a base film to form a barrier film, and the silica vapor-deposited surface of this barrier film was bonded to polyester film A by dry lamination.

[0058] Example 7 A laminate was obtained in the same manner as in Example 6, except that the base film was changed to a stretched PET film (manufactured by Unitika Ltd., trade name "Emblet PC"), which is a crystalline polyester film.

[0059] Example 8 A 12 μm thick stretched PET film, which is a crystalline polyester film, was laminated on the barrier film, and the amount of urethane resin adhesive applied after drying was 4 g / m. 2 A laminate was obtained in the same manner as in Example 6, except that the thickness was adjusted to 4 μm. The same urethane resin adhesive was also used for laminating the stretched PET film, and the coating amount after drying was 4 g / m 2 The thickness was adjusted to 4 μm.

[0060] (Comparative Example 1) A laminate was obtained in the same manner as in Example 1, except that polyester film A was replaced with polyester film G-13 (manufactured by Kurabo Industries, Ltd.) having a thickness of 30 μm.

[0061] (Comparative Example 2) A laminate was obtained in the same manner as in Example 1, except that the polyester film A was replaced with a 60 μm thick polypropylene film ZK207 (manufactured by Toray Advanced Film Co., Ltd.).

[0062] (Comparative Example 3) A laminate was obtained in the same manner as in Example 7, except that polyester film A was replaced with polyester film G-13 (manufactured by Kurabo Industries, Ltd.) having a thickness of 30 μm.

[0063] [Various evaluations] The obtained laminate was subjected to various evaluations, and the results are shown in Tables 2 and 3.

[0064] (Tear strength measurement) The tear strength of the laminate in the MD direction was measured in accordance with the trouser method described in JIS K7128.

[0065] (Thigh gap width measurement) The laminate was cut into two 90mm square pieces, the sealant layers facing each other, and the three outer edges were sealed. 30ml of water was then poured into the pieces, and the remaining edge was sealed to create a sample. The sealing conditions were a thickness of 0.2MPa, a temperature of 190°C, and a time of 1 second. The seal width was 5mm from the outer edge.

[0066] The prepared sample was torn open by a tester in the MD direction, and the deviation between the cut edge of the top sheet and the cut edge of the bottom sheet (hereinafter referred to as the step) of the overlapping sheets was measured. The step was measured by placing a scale in the direction perpendicular to the tearing direction. The maximum step along the tear line was taken as the measured value of the crotch tear width.

[0067] (Oxygen permeability and water vapor permeability measurement) The oxygen permeability and water vapor permeability of the laminate were measured in accordance with JIS K7126B.

[0068] (Measurement of the mass ratio of polyester components) The mass proportion of the polyester component (polyester film) was calculated based on the total mass of the materials constituting the laminate.

[0069] [Table 2]

[0070] [Table 3] [Industrial Applicability]

[0071] The laminate according to the present invention has excellent tearability as a packaging material. Furthermore, the constituent films can be substantially all polyester films. Such a laminate can be called a mono-material packaging material, and is expected to have excellent recyclability. [Explanation of symbols]

[0072] 1...base material layer, 2...adhesive layer, 3...sealant layer, 10...laminated body.

Claims

1. A laminate for forming a packaging bag, A substrate layer including a crystalline polyester film, an adhesive layer, and a sealant layer including a polyester film, in this order; The thickness of the sealant layer is 15 to 100 μm, The sealant layer has a value of 13% / μm or less when the breaking elongation in the MD direction measured at a width of 15 mm is divided by the thickness, A laminate in which the stretching ratio of the polyester film contained in the sealant layer is 1.1 times or more in the MD direction.

2. The laminate of claim 1 , wherein the sealant layer has a planar orientation coefficient of 0.08 or less.

3. The polyester film contained in the sealant layer is obtained by polycondensation of a diol and a dicarboxylic acid, the diols include at least one diol selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol; The laminate according to claim 1 or 2, wherein the dicarboxylic acid comprises terephthalic acid.

4. The laminate according to any one of claims 1 to 3, wherein the crystalline polyester film contained in the base layer is made of at least one crystalline polyester selected from the group consisting of polybutylene terephthalate, polybutylene naphthalate, and polyethylene terephthalate.

5. Water vapor permeability is 10g / m ２ The laminate according to any one of claims 1 to 4, wherein the average curing time is 100 minutes or less.

6. The laminate according to any one of claims 1 to 5, wherein at least one of the substrate layer and the sealant layer comprises recycled polyester.

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