Laminate and packaging using same

Abstract

To provide a laminate excellent in thermostability, heat sealability and tear-proof property and capable of sufficiently suppressing penetration of a content such as oily food, and also to provide a package formed using the same.SOLUTION: A laminate includes at least a substrate layer, an adhesion layer and a sealant layer laminated in this order. The sealant layer includes: one outer layer (A); the other outer layer (B); and an intermediate layer interposing these. The outer layer (A) is formed on a side of the substrate layer, and the outer layer (B) is formed on a side to have contact with a content. The outer layer (A) and outer layer (B) include a polypropylene resin (C). The intermediate layer includes a resin composition containing a polypropylene resin (C) and a crystal nucleus agent (D).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate in which polypropylene is laminated onto a substrate as a sealant resin, the laminate having excellent adhesion between the sealant layer and the substrate, suppressing the penetration of oil and fat components into the inner surface, and also having excellent retort resistance and bag rupture resistance, and a package using the same. [Background technology]

[0002] Sealant films are widely used in packaging materials for food, beverages, medicines, etc. The sealant film is disposed on the innermost layer of the packaging material, and can seal the package by heat sealing. As such sealant films, polyolefin resins such as polyethylene and polypropylene, which show high sealing strength, and copolymer resins such as ionomer and EMMA are used, but as sealant films for packaging materials applied to products using edible oil such as snacks, bread, noodles, etc., and retort foods, etc., polypropylene resins, which have excellent heat resistance and oil resistance, are used.

[0003] When the laminate is used as a packaging material, various contents such as food are filled into the packaging material. In particular, when oily foods are filled as the contents and the material is retorted, the sealant film absorbs oil over time from immediately after retorting, causing the adhesive layer to swell and delamination due to a decrease in adhesive strength. This delamination can cause the bag to break due to internal or external impacts, so there is a need to suppress the penetration of oily foods and other contents into the inner surface of the packaging material.

[0004] In response to these demands, for example, Patent Document 1 discloses that a laminate film with improved laminate strength can be obtained by using an adhesive composition containing a polyester polyurethane having a structure in which a polybasic acid component and a polyhydric alcohol component are copolymerized components and a polyester polyol is chain-extended with isophorone diisocyanate, and a polyisocyanate compound.

[0005] However, while the above-mentioned improvements in adhesives improve the laminate strength, they do not adequately prevent the penetration of contents such as oily foods into the inner surface of the packaging material, and there is a problem in that the resistance to bag rupture when dropped or subjected to a large force is insufficient. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-37508 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the problems associated with the above-mentioned conventional techniques, and aims to provide a laminate that has excellent heat resistance, heat sealability, and bag-breaking resistance and can sufficiently inhibit the penetration of contents such as oily foods, and a package formed using the same. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention according to claim 1 provides a laminate comprising at least a base layer, an adhesive layer, and a sealant layer laminated in this order, The sealant layer has one outer layer (A), another outer layer (B), and an intermediate layer interposed therebetween, The outer layer (A) is formed on the base layer side, and the outer layer (B) is formed on the side that comes into contact with the contents. And, The outer layer (A) and the outer layer (B) are made of a polypropylene resin (C), The intermediate layer is a laminate characterized by being made of a resin composition containing a polypropylene resin (C) and a crystal nucleating agent (D).

[0009] By forming a layer made of a resin composition containing a polypropylene resin (C) and a crystal nucleating agent (D) as an intermediate layer between the outer layer (A) and the outer layer (B) of the sealant film, the crystallinity of the polypropylene resin (C) can be increased, and the penetration of oils and fats during retort can be suppressed by the intermediate layer, making it possible to prevent a decrease in laminate strength due to swelling of the adhesive. If this intermediate layer is formed on the outer layer (B) side that contacts the contents, the increase in crystallinity leads to a decrease in seal strength, and if it is formed on the outer layer (A) side that contacts the base layer via the adhesive layer, it is not preferable because it cannot suppress the penetration of oils and fats into the adhesive layer, leading to a decrease in laminate strength. Therefore, it is desirable that the layer made of a resin composition containing a polypropylene resin (C) and a crystal nucleating agent (D) is formed as an intermediate layer between the outer layer (A) and the outer layer (B) of the sealant film.

[0010] The present invention according to claim 2 is the laminate according to claim 1, characterized in that the content of the crystal nucleating agent (D) is 0.1 to 10.0% by mass. If the content of the crystal nucleating agent (D) is less than 0.1% by mass, the degree of crystallization does not increase, and the effect of suppressing the permeation of fats and oils is small. This leads to a decrease in laminate strength, leading to the ease of tearing of the packaging bag. If the content is more than 10.0% by mass, a difference in the degree of crystallization occurs between the outer layer and the middle layer of the sealant layer, and therefore an excessive amount of addition also leads to a decrease in laminate strength and the ease of tearing of the bag, which is not preferable.

[0011] The present invention according to claim 3 is the laminate according to claim 1 or 2, characterized in that the intermediate layer has a thickness of 5 to 15 μm. If the thickness of the intermediate layer is less than 5 μm, the effect of preventing penetration of oils and fats during retort is weakened, leading to a decrease in laminate strength, and if the thickness is more than 15 μm, an increase in crystallinity creates a difference in crystallinity between the outer layer and the intermediate layer of the sealant layer, resulting in a decrease in laminate strength, which is undesirable.

[0012] The present invention according to claim 4 is the laminate according to claims 1 to 3, in which the ratio of the intermediate layer is 10 to 30%. If the ratio is less than 10%, the intermediate layer is thin and oils and fats easily penetrate, leading to a decrease in laminate strength. If the ratio is more than 30%, an increase in crystallinity creates a difference in crystallinity between the outer layer and the intermediate layer of the sealant layer, leading to a decrease in laminate strength.

[0013] The present invention according to claim 5 provides a package formed using the laminate according to claims 1 to 4. Since such a package is formed using the laminate of the present invention, it is possible to sufficiently inhibit the penetration of oil and fat components into the inner surface of the package.

[0014] Furthermore, even when the packaging material is used for applications requiring heat treatment, it is possible to inhibit the penetration of oil and fat components into the inner surface of the packaging material even after the heat treatment. Effect of the Invention

[0015] According to the present invention, it is possible to provide a laminate that has excellent heat resistance, heat sealability, and bag rupture resistance and can sufficiently suppress the penetration of contents such as oily foods, and a package formed using the same. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention. [Diagram 2] 1 is a schematic cross-sectional view of a sealant film according to one embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram for explaining the penetration of oils and fats into a conventional sealant film. [Figure 4] FIG. 2 is a diagram for explaining the penetration of oils and fats into the sealant film of the present invention. [Diagram 5] FIG. 1 is a schematic cross-sectional view of a laminate produced in Example 1 of the present invention. [Figure 6] FIG. 2 is a front view of a pouch produced in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0018] <Laminate> Fig. 1 is a schematic cross-sectional view of a laminate 1 according to this embodiment, and Fig. 2 is a schematic cross-sectional view of a sealant film 12 according to this embodiment. As can be seen from Fig. 1, the laminate 1 has a basic configuration in which a base layer 10, an adhesive layer 11, and a sealant film 12 are laminated in this order, and has a structure in which the sealant film 12 is disposed as the innermost layer that contacts the contents. Then, the sealant films can be placed opposite each other and heat sealed to form a package that can contain the contents.

[0019] <Base material layer> The base layer 10 is a layer that functions as a support for the laminate. As a material, a film mainly made of plastic is used, and is appropriately selected depending on the conditions of use, such as the type of contents when the package is made and whether or not heat treatment is performed after filling. As a material for the base layer 10, for example, polyethylene, polypropylene, polyethylene terephthalate, nylon, etc. are used, but the material is not particularly limited, and it may be a single layer made of one of the above materials, or a layer in which a plurality of the above materials are combined by laminating these single layers. In this embodiment, the base layer 10 is a polyethylene terephthalate film.

[0020] <Sealant film> As can be seen from FIG. 2, the sealant film 12 can have a multi-layer structure with an intermediate layer 15 and polypropylene resin (C) on both sides of the intermediate layer 15 (outer layer (A) 13 and outer layer (B) 14). The outer layer (B) 14 that comes into contact with the contents may be a layer that can exhibit heat sealability when heated. The sealant film can be produced by a three-layer co-extrusion film formation method using three layers of resin: the outer layer (A) 13, the intermediate layer 15, and the outer layer (B) 14.

[0021] The thickness of the intermediate layer 15 is preferably 5 to 15 μm, and if the thickness of the intermediate layer 15 is less than 5 μm, the effect of preventing the penetration of oils and fats during retort is weakened, leading to a decrease in laminate strength. Also, if the thickness is thicker than 15 μm, the increase in crystallinity creates a difference in the crystallinity between the outer layer and the intermediate layer of the sealant layer, which is undesirable as it reduces the laminate strength.

[0022] The ratio of the intermediate layer 15 is preferably 10 to 30%, and if it is less than 10%, the intermediate layer 15 is thin and oils and fats easily penetrate it, which leads to a decrease in laminate strength, and if it is more than 30%, the increase in crystallinity creates a difference in crystallinity between the outer layer and the intermediate layer of the sealant layer, which leads to a decrease in laminate strength.

[0023] The intermediate layer 15 can be formed using a resin composition for forming an intermediate layer, which contains the following components: The resin composition for forming an intermediate layer will be described below.

[0024] <Resin composition for forming intermediate layer> The resin composition for forming an intermediate layer according to one embodiment of the present invention is a resin composition bonded to a polypropylene resin (C). It contains a crystal nucleating agent (D), and the polypropylene resin (C) is a random polypropylene resin and a block polypropylene resin used in an appropriate blend ratio.

[0025] By using such a resin composition for forming an intermediate layer, the sealant film can be suitably used for packaging applications that are subjected to heat treatment such as bathing in hot water, such as retort food packaging, and it becomes easier to prevent bag-shaped packaging materials from breaking due to heat treatment such as bathing in hot water.

[0026] The polypropylene resin (C) may be a combination of the following random polypropylene resin and block polypropylene resin. C1: Random polypropylene (Prime Polymer: F744NP). C2: Random polypropylene (made by Prime Polymer: F-300SP). C3: Block polypropylene (made by Japan Polypropylene: Novatec BC5FA). C4: Block polypropylene (made by Japan Polypropylene: Novatec BC3HF). In this example and the comparative example, the components were mixed in a ratio of C1:C3=1:1.

[0027] In addition, the resin composition for forming an intermediate layer of the present invention preferably contains a crystal nucleating agent (D). In the present invention, a crystal nucleating agent is an additive used to control the amount and orientation of crystalline components in a resin and improve functions such as rigidity, transparency, and chemical resistance. The crystal nucleating agent (D) is not particularly limited, and any agent commonly used in the relevant field may be used, but it is preferable to select from organic nucleating agents such as phosphate ester nucleating agents, nonitol nucleating agents, and sorbitol nucleating agents shown below. D1: Nonitol crystal nucleating agent (Dainichi Seikagaku: Clear Master PP-RM-SKZ R8020). D2: Nonitol-based crystal nucleating agent (Milliken: Millard NX8500). D3: Sorbitol-based crystal nucleating agent (Dainichi Seikagaku Co., Ltd.: Clear Master PP-RMH200). D4: Aluminum phosphate salt (Adeka Stab NA21, Adeka Chemical Co., Ltd.). In this example and the comparative example, D1 was used.

[0028] The intermediate layer 15 can be formed by forming a film from the above-mentioned intermediate layer forming resin composition. Specific examples of film formation conditions include line speed, film formation temperature, cooling temperature, cooling method, etc. By changing these conditions, the crystallinity can be controlled.

[0029] Methods for bonding the base material layer 10 and the sealant film 12 include, but are not limited to, lamination methods using an adhesive as described below.

[0030] <Adhesive> The adhesive 11 bonds the sealant film 12 and the base layer 10. Examples of the adhesive 11 include polyurethane resins in which a difunctional or higher isocyanate compound is allowed to react with a base material such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. The above-mentioned various polyols may be used alone or in combination of two or more.

[0031] As described above, the laminate according to the present invention can sufficiently suppress the penetration of the contents of oily foods and the like. Fig. 3 is a diagram showing the penetration of oil into a conventional sealant film, and Fig. 4 shows the case of the sealant film according to the present invention in comparison. As can be seen from Fig. 4, by forming the intermediate layer 15 as an intermediate layer between the outer layer (A) and the outer layer (B) of the sealant film, the intermediate layer can suppress the penetration of oil during retort.

[0032] <Package> The packaging body according to the present embodiment is formed using the above-mentioned laminate. As a result, the packaging material can suppress adhesion and penetration of the contents, such as oily foods, to the inner surface of the packaging material. The packaging material may also be used for applications in which heat treatment at 80° C. or higher is performed. Specifically, the packaging material may be used as a packaging material in which heat treatment such as hot water bathing is performed, such as a packaging material for retort food. According to the packaging material of this embodiment, even when used for such applications, adhesion and penetration of the contents, such as oily foods, to the inner surface of the packaging material can be suppressed even after heat treatment. EXAMPLES

[0033] EXAMPLES Hereinafter, samples will be prepared based on examples and comparative examples to explain the present invention more specifically, but the present invention is not limited to the following examples.

[0034] [Example 1] <Preparation of Resin Composition for Forming Intermediate Layer> A resin composition for forming an intermediate layer was prepared by mixing a random polypropylene resin (F744NP made by Prime Polymer) and a block polypropylene resin (Novatec BC5FA made by Nippon Polypro) as the polypropylene resin (C) component, and a nonitol-based crystal nucleating agent (Clearmaster PP-RM-SKZ R8020 made by Dainichi Seikagaku Co., Ltd.) as the crystal nucleating agent (D) component. Here, the content of each component was adjusted so that the mass ratio of random polypropylene and block polypropylene in the polypropylene resin (C) component was 1:1, and the crystal nucleating agent (D) component was 0.05 mass% based on the total amount of the polypropylene resin (C) component and the crystal nucleating agent (D) component, and the remainder was the polypropylene resin (C) component.

[0035] <Preparation of Laminate> Using a three-layer co-extruder, the resin composition for forming the intermediate layer was extruded to form a film, and a 75 μm sealant film including a 15 μm intermediate layer was obtained. Here, the outer layers (A) and (B) on both sides had the same film thickness. The obtained sealant film and a 38 μm thick PET film as a substrate were hand laminated using a two-liquid curing polyurethane adhesive (manufactured by Mitsui Chemicals, Inc.) to obtain a laminate (Figure 5). See below for drying and lamination conditions. Drying conditions: temperature 70℃, time 1min Lamination conditions: Lamination pressure: 0.4MPa Film feed speed: 1m / min Temperature: 60℃ After lamination, the laminate was subjected to an aging treatment by leaving it at 50°C for 4 days.

[0036] [Examples 2 to 5] A resin composition for forming an intermediate layer, a sealant film, and a laminate were prepared in the same manner as in Example 1, except that the crystal nucleating agent (D) component in the resin composition for forming an intermediate layer was changed as shown in Table 1. [Examples 6 to 7] A resin composition for forming an intermediate layer, a sealant film, and a laminate were prepared in the same manner as in Example 3, except that the thickness of the intermediate layer of the sealant film was changed as shown in Table 1. [Examples 8 to 9] A resin composition for forming an intermediate layer, a sealant film, and a laminate were prepared in the same manner as in Example 4, except that the thickness of the sealant film and the thickness of the intermediate layer were changed as shown in Table 1. [Comparative Example 1] A resin composition for forming an intermediate layer, a sealant film, and a laminate were produced in the same manner as in Example 1, except that the crystal nucleating agent (D) component was not added to the resin composition for forming an intermediate layer. [Comparative Example 2] An intermediate layer-forming resin composition, a sealant film, and a laminate were prepared in the same manner as in Example 1, except that the intermediate layer of Example 3 was added to the outer layer (A) (on the substrate layer side) of the sealant film. [Comparative Example 3] An intermediate layer-forming resin composition, a sealant film, and a laminate were prepared in the same manner as in Example 1, except that the intermediate layer of Example 3 was added to the outer layer (B) (contents side) of the sealant film.

[0037] [Measurement of oil swelling amount] The oil swelling amount was evaluated for the laminates obtained in the examples and comparative examples. First, two samples were prepared by cutting the laminate to 150 mm long x 138 mm wide. The two samples were stacked so that the sealant film was on the inside, and one side of the vertical end and two sides of both horizontal ends were heat-sealed over a width of 8 mm with a heat sealer to form a sealed portion, and a pouch with one side of the vertical end open was produced (see FIG. 6), and the weight (W0) of the produced pouch was measured. Next, 100 g of edible oil (Salad oil, manufactured by Nisshin Oillio Co., Ltd.) was poured from the opening of the pouch, and then the opening was heat-sealed over a width of 8 mm with a heat sealer to form a sealed portion, and the pouch was sealed. The sealed pouch was subjected to a heat-pressure sterilization treatment (retort treatment) at 121°C for 30 minutes. After the retort treatment, the injected edible oil was drained, washed with detergent, and dried, and the total weight (W1) of the pouch was measured. The amount of oil swelling (g / cm3) was calculated from the weight (W1) of the pouch after the retort treatment and the weight (W0) of the pouch before the injection of the edible oil by the following formula: 3 ) was sought. Oil swelling amount (g / cm 3 )=(W1-W0) / {13.4×12.2×(t×10 -4 )×2}.

[0038] [Laminate strength measurement] For the above pouches, the tensile properties (lamination strength) between the base layer (PET) and the sealant film of the pouches before and after retort were measured in accordance with JIS K 7127. See below for the measurement conditions and evaluation criteria for the laminate strength. <Measurement conditions> Sample width: 15mm. Peeling angle: 90° (T-type peeling) Peel speed: 300mm / min Measuring device: RTC-1250 Tensilon universal testing machine (Orientec). <Evaluation criteria> After retorting, the average value in the machine direction (MD) and transverse direction (TD) is 〇4.0 (N / 15mm) or more △3.5 (N / 15mm) or more, less than 4.0 (N / 15mm) ×Less than 3.5 (N / 15mm).

[0039] [Seal strength measurement] The tensile properties (seal strength) of the sealed parts of the above pouches before and after retort were measured in accordance with JIS Z 1707. See below for the measurement conditions and evaluation criteria for seal strength. <Measurement conditions> Sample width: 15mm. Peeling angle: 90° (T-type peeling) Peel speed: 300mm / min Measuring device: RTC-1250 Tensilon universal testing machine (Orientec). <Evaluation criteria> After retorting, the average value in the machine direction (MD) and transverse direction (TD) is 〇 35.0 (N / 15mm) or more × Less than 35.0 (N / 15mm).

[0040] [Dropped bag test] There are various methods for measuring bag rupture resistance, but the bag drop test is often used as a simple method that does not rely on machines. A completely sealable bag is made, a certain amount of water is enclosed, and the bag is dropped from a certain height to check for rupture. The above pouch was subjected to the bag drop test after retort treatment (121℃, 30min). See below for the bag drop test conditions and evaluation criteria. <Drop bag test conditions> Drop height: 100cm Number of falls: 10 Number of trials (n): 5 <Evaluation criteria> 〇 All n5 bags are intact × Of n5, a pieces are broken (→written as a / 5).

[0041] The results of the oil swelling amount measurement, lamination strength measurement, seal strength measurement, and bag drop test are shown in Table 1.

[0042] [Table 1] From the results of Examples 1 to 9 shown in Table 1, When the content of the crystal nucleating agent (D) was 0.1 to 10.0% by mass, the lamination property and the sealability were good, but when it was outside the range of 0.05% or 20%, they were insufficient. Furthermore, when the thickness of the intermediate layer is 5 to 15 μm, the laminate strength and seal strength are good, but if it is outside the range and is less than 5 μm or is thicker than 15 μm, the laminate strength decreases. Furthermore, when the ratio of the intermediate layer is 10 to 30%, the laminate strength and seal strength are good, but when it is outside the range, below 10%, or above 30%, the laminate strength decreases. In addition, from Comparative Examples 1 to 3, It was found that the intermediate layer of the sealant layer reduces the laminate strength when included in the outer layer (A) on the base layer side, and reduces the seal strength when included in the outer layer (B) on the content side. Therefore, the intermediate layer is appropriately positioned because it maintains both the laminate strength and the seal strength and also suppresses the penetration of oils and fats in the middle of the sealant layer. Furthermore, if either the laminate strength or the seal strength is insufficient, the bag rupture resistance after retort treatment is insufficient. [Explanation of symbols]

[0043] 1...Laminate 10...Base material layer 11...Adhesive layer 12. Sealant layer 13: Outer layer of sealant layer (A) (substrate layer side) 14: Outer layer of sealant layer (B) (contents side) 15. Middle class 20.... Pouch formed using laminate

Claims

1. A laminate comprising at least a base layer, an adhesive layer, and a sealant layer laminated in this order, The sealant layer has one outer layer (A), another outer layer (B), and an intermediate layer interposed therebetween, The outer layer (A) is formed on the base layer side, and the outer layer (B) is formed on the side that comes into contact with the contents, The outer layer (A) and the outer layer (B) are made of a polypropylene resin (C), The intermediate layer is made of a resin composition containing a polypropylene resin (C) and a crystal nucleating agent (D), The ratio of the thickness of the intermediate layer to the total thickness of the laminate is 10 to 30%, The content of the crystal nucleating agent (D) is 0.1 to 10.0 mass% based on the total amount of the polypropylene resin (C) and the crystal nucleating agent (D) in the intermediate layer.

2. 2. The laminate according to claim 1, wherein the intermediate layer has a thickness of 5 to 15 μm.

3. The laminate according to claim 1 or 2, wherein the polypropylene resin (C) comprises a random polypropylene resin and a block polypropylene resin.

4. A packaging material formed using the laminate according to any one of claims 1 to 3.

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