Laminated sheet for lid, lid and chilled food packaging container

Abstract

To provide a laminated sheet for a lid, which uses paper as a lid material of a chilled food packaging container in consideration of environment, and does not degrade gas barrier properties even when having been taken out from high temperature and high humidity.SOLUTION: The laminated sheet for the lid, which is used for the lid of the chilled food packaging container that includes a container body provided with an opening and the lid covering the opening includes at least a heat seal layer, a gas barrier layer, an anchor coat layer and a paper substrate, in this order. A mass of the paper substrate is 50% or more of the mass of the laminated sheet for the lid, and oxygen permeability is 5 cc / m2 atm day, after the laminated sheet has been stored at a temperature of 5°C and then stored in an atmosphere at a temperature of 40°C and a relative humidity of 90%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated sheet for a lid, a lid, and a packaging container for chilled food. [Background technology]

[0002] In recent years, changes in household structure and lifestyles due to the trend toward nuclear families, as well as advances in distribution and freezing / refrigeration technology, have led to an increase in demand for cooked or processed chilled foods sold at convenience stores and supermarkets, etc. At the same time, demand for packaging containers to store chilled foods is also increasing.

[0003] Meanwhile, as efforts to reduce plastic waste continue, there is growing demand for food packaging containers that use paper as a base material, a renewable resource with a low environmental impact. There is also a demand for packaging containers that store chilled foods to use paper as a base material.

[0004] Chilled foods are generally distributed and stored at temperatures between 0 and 10°C, although an optimal temperature range is set for each food. After being manufactured, packaging products containing chilled foods in paper containers are delivered to consumers through various distribution channels, and are typically stored in refrigerators both during distribution and at home. Refrigerated environments are often subject to high humidity. Condensation also forms on the outer surface of paper containers when the temperature drops to room temperature. Because packaging containers for chilled foods are thus affected by moisture, when a paper base is used, a laminated sheet in which a water-resistant gas barrier layer is laminated to the paper base is often used (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-224058 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have found that when a paper base material is used for a packaging container for chilled foods, the following problem occurs with the lid: Specifically, when a packaging article containing chilled food in a container and equipped with a lid using a paper base material laminated with a water-resistant gas barrier layer is stored, for example, at a temperature within the above range, or when the temperature is raised from a temperature within the above range to room temperature and then lowered back to a temperature within the above range, the gas barrier layer deteriorates due to swelling of the paper and moisture from condensation, and the gas barrier property tends to decrease.

[0007] The present invention was developed in consideration of the above-mentioned problems, and aims to provide a laminate sheet for lids that has excellent gas barrier properties as a lid material for packaging containers for chilled foods, even when placed in environments ranging from low temperature to high temperature and humidity. Another aim of the present invention is to provide a lid made of the laminate sheet for lids, and a packaging container for chilled foods that includes the lid. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a laminated sheet for lids according to claim 1, which is used for a lid of a packaging container for chilled food, the container comprising a container body having an opening and a lid covering the opening, the laminated sheet for lids comprising at least a heat seal layer, a gas barrier layer, an anchor coat layer and a paper base material in this order, the mass of the paper base material being 50% or more of the mass of the laminated sheet for lids, and having an oxygen permeability of 5 cc / m or less after being stored at a temperature of 5°C and then stored in an atmosphere at a temperature of 40°C and a relative humidity of 90%. 2 The laminated sheet for a lid body is characterized by having a viscosity of 1000 ppm / day or less.

[0009] In order to solve the above problems, the laminated sheet for a lid according to claim 2 of the present invention is stored at a temperature of 5°C, and then stored in an atmosphere at a temperature of 40°C and a relative humidity of 90%, and the oxygen permeability after this is 5 cc / m 2 ·atm·day or less, and the change in oxygen permeability is 2cc or less compared to the oxygen permeability before storage. / m2 ATM Day 2. The laminated sheet for a lid body according to claim 1, wherein the thickness is within the range of 100 mm to 150 mm.

[0010] In order to solve the above problems, the laminated sheet for a lid according to claim 3 of the present invention is stored at a temperature of 5°C, and then stored in an atmosphere at a temperature of 40°C and a relative humidity of 90%, and the oxygen permeability after this is 5 cc / m 2 3. The laminated sheet for lids according to claim 1 or 2, characterized in that the oxygen permeability is not more than 1 atm·day and the rate of change in oxygen permeability is within 20% compared to the oxygen permeability before storage.

[0011] In order to solve the above problem, the laminate sheet for a lid body according to claim 4 of the present invention is a laminate sheet for a lid body according to any one of claims 1 to 3, characterized in that the gas barrier layer is formed of a thin film of metal or metal oxide.

[0012] In order to solve the above problem, the laminate sheet for a lid body according to claim 5 of the present invention is a laminate sheet for a lid body according to any one of claims 1 to 4, characterized in that the gas barrier layer is an aluminum thin film.

[0013] In order to solve the above problem, the laminate sheet for a lid body according to claim 6 of the present invention is a laminate sheet for a lid body according to any one of claims 1 to 4, characterized in that the gas barrier layer is aluminum oxide (alumina).

[0014] In order to solve the above problem, the lid laminate sheet according to claim 7 of the present invention is a lid laminate sheet according to any one of claims 1 to 4, characterized in that the gas barrier layer is silica (SiO2).

[0015] In order to solve the above problems, the invention of claim 8 is a lid using the laminated sheet for a lid of any one of claims 1 to 7.

[0016] In order to solve the above problem, the invention described in claim 9 is a packaging container for chilled food provided with the lid described in claim 8. [Effects of the Invention]

[0017] According to the present invention, there is provided a laminate sheet for lids, which serves as a lid material for packaging containers for chilled foods and whose gas barrier properties do not deteriorate even after being placed in a low-temperature environment to a high-temperature, high-humidity environment. Also, according to the present invention, there are provided a lid made of the laminate sheet for lids, and a packaging container for chilled foods including the lid. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a partial cross-sectional view schematically showing an example of a laminate sheet for a lid according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a partial cross-sectional view that schematically shows an example of a food packaging container according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. Elements having the same or similar functions are designated by the same reference numerals, and redundant descriptions will be omitted.

[0020] An example of a lid laminate sheet according to an embodiment of the present invention is a lid laminate sheet 10 used for a lid 201 of a packaging container 200 for chilled food, which includes a container body 202 with an opening and a lid 201 that covers the opening, as shown in the schematic cross-sectional view of Figure 2. As shown in the schematic cross-sectional view of Figure 1, the lid laminate sheet 10 is formed by laminating at least a heat seal layer 101, a gas barrier layer 102, an anchor coat layer 103, and a paper substrate 104 in this order. The heat seal layer 101 is the innermost layer that comes into contact with the contents. Each layer will be described in detail below.

[0021] (heat seal layer) The heat seal layer 101 may be any material that can heat seal the container body 202 and lid 201 of the chilled food packaging container 200 shown in FIG. 2 to hermetically seal the container. Typically, films of ethylene-vinyl acetate copolymer (EVA), ionomer resin, or other polyolefins are used. Linear low density polyethylene (LLDPE) or very low density linear polyethylene (VLDPE) is preferred. A sealant layer with a known easy-peel function can also be used.

[0022] The thickness of the heat seal layer 101 is not particularly limited, but is preferably thin in consideration of the paper-making ratio.

[0023] (gas barrier layer) For applications requiring light blocking properties, a layer deposited with metallic aluminum can be used as the gas barrier layer 102, but for microwave oven applications, it is preferable to use a metal oxide. Examples of such metal oxides include, but are not limited to, aluminum oxide (alumina) and silicon oxide (silica).

[0024] By having a vapor-deposited layer of aluminum or metal oxide as the gas barrier layer 102, the lid laminate sheet 10 of the present invention not only has higher oxygen barrier properties than polyvinyl alcohol-based oxygen barrier resins, which are common resin-based coated gas barrier layers, but also has increased water resistance, so that even if water droplets adhere to the paper surface and penetrate into the paper to reach the gas barrier layer 102, deterioration of the oxygen barrier properties due to moisture degradation can be further suppressed. Therefore, the sheet is suitable as a lid material for containers for chilled foods, which are likely to have water droplets adhere to the lid material when removed from a refrigerator and placed in a low-temperature environment followed by a high-temperature, high-humidity environment.

[0025] The gas barrier layer 102 is preferably formed by a vacuum deposition method from the viewpoint of oxygen gas barrier performance and film uniformity. While known deposition methods include vacuum deposition, sputtering, and chemical vapor deposition (CVD), vacuum deposition is preferred due to its high deposition rate and high productivity. Among vacuum deposition methods, electron beam heating is particularly effective because it allows for easy control of the deposition rate via the irradiation area and electron beam current, and allows for rapid heating and cooling of the deposition material.

[0026] (Anchor layer) The anchor coat layer 103 is provided on the surface of the paper substrate to improve adhesion between the paper substrate 104 and the gas barrier layer 102 and to improve gas barrier properties. Examples of resins that can be used for the anchor coat layer 103 include polyvinyl alcohol, polyvinylpyrrolidone, polyvinylidene chloride, polyacrylic, polyester, polyurethane, polycarbonate, polyurea, polyamide, polyimide, melamine, phenol, and polyolefin. Additives such as silane coupling agents and organic titanates may also be mixed in.

[0027] The thickness of the anchor coat layer 103 may be, for example, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the anchor coat layer 103 is 1 μm or more, the unevenness of the paper base material described above can be efficiently filled, allowing the aluminum vapor deposition layer described below to be laminated uniformly. Furthermore, if the thickness of the anchor coat layer 103 is 20 μm or less, the vapor deposition layer can be laminated uniformly while keeping costs down.

[0028] Examples of solvents contained in the solution for the anchor coat layer 103 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination. Among these, from the viewpoint of properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of environmental friendliness, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred. The anchor coat layer 103 can be formed by applying a coating solution containing at least the above-mentioned solvent to the paper substrate 104 and drying it.

[0029] (Paper base material) The paper substrate 104 is not particularly limited and may be selected appropriately depending on the application of the lid to which it is applied, and may be paper whose main component is plant-derived pulp. Specific examples of the paper substrate 104 include fine paper, special fine paper, coated paper, art paper, cast-coated paper, construction paper, kraft paper, and glassine paper. The thickness of the paper substrate 104 is, for example, 20 g / m 2 More than 500g / m 2 Preferably, it is 30 g / m or less. 2 More than 100g / m 2 More preferably, it is:

[0030] The paper substrate 104 may have a coating layer at least on the side that contacts the anchor coating layer 103 described below. By providing the coating layer, it is possible to prevent the anchor coating layer 103 from penetrating into the paper, and it also plays a role of filling in the unevenness of the paper, and it is possible to form the anchor coating layer 103 uniformly without defects. For example, the coating layer may contain various binder resins such as styrene-butadiene, styrene-acrylic, and ethylene-vinyl acetate. Polymers, polyvinyl alcohol resins, cellulose resins, paraffin (wax), etc. may be used, and fillers such as clay, kaolin, calcium carbonate, talc, and mica may also be included.

[0031] The thickness of the coating layer is not particularly limited, but may be, for example, 1 μm or more and 10 μm or less, or 3 μm or more and 8 μm or less.

[0032] The weight of the paper is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the entire lid laminate sheet. If the weight of the paper is 50% by mass or more, based on the entire lid laminate sheet, the amount of plastic material used can be sufficiently reduced, the entire lid laminate sheet can be said to be made of paper, and it has excellent recyclability.

[0033] (Printing layer) The printed layer (not shown) is a layer formed for practical use as a product. The printed layer is made of, for example, a urethane-based, acrylic-based, nitrocellulose-based, rubber-based, vinyl chloride-based, etc. This layer is made of ink containing a conventionally used ink binder resin to which various pigments, extender pigments, plasticizers, drying agents, stabilizers, etc. are added, and on which letters, pictures, etc. are formed. Examples of the formation method that can be used include well-known printing methods such as offset printing, gravure printing, and silk screen printing, and well-known coating methods such as roll coating, knife edge coating, and gravure coating.

[0034] (oxygen permeability) The lid laminate sheet 10 of the present invention can improve the adhesion between the paper substrate 104 and the gas barrier layer 102 by providing an anchor coat layer 103 between the paper substrate 104 and the gas barrier layer 102, and by having an aluminum or metal oxide vapor deposition layer as the gas barrier layer 102, the deterioration of the gas barrier properties is suppressed even after storage in a low-temperature environment to a high-temperature, high-humidity environment. As a result, the oxygen permeability after storage at a temperature of 5°C and then in an atmosphere at a temperature of 40°C and a relative humidity of 90% is 5 cc / m 2 ·atm·day or less, and the change in oxygen permeability is 2cc compared to the oxygen permeability before storage / m 2 ATM Day The rate of change is kept within 20%.

[0035] (Packaging container for chilled food) As described above, the lid body 201 made of the lid body laminated sheet 10 of the present invention and the packaging container 200 for chilled food equipped with it exhibit excellent gas barrier properties even when placed in a low-temperature environment or a high-temperature, high-humidity environment, thereby enabling cooked frozen or chilled foods to be safely stored. [Example]

[0036] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0037] Example 1 Basis weight 80g / m 2 Anchor coating solution 1 was applied to the coating surface of one-sided coated paper (Sinar DG, manufactured by APP) using a bar coater so that the thickness after drying would be 1 μm, and then dried at 100°C for 1 minute. After that, aluminum was formed to a thickness of 50 nm on the anchor coating surface using a vacuum deposition machine, and then a urethane adhesive was applied to the aluminum deposition layer at a rate of 2 g / m. 2 After coating and drying at 100° C. for 1 minute, a 30 μm LLDPE film was dry laminated to obtain a lid laminate sheet of Example 1. <Anchor Coat Layer Liquid 1> Pure water: 90 parts by weight. Polyvinyl alcohol (PVA-105): 10 parts by weight.

[0038] Example 2 Basis weight 80g / m 2 On the paper side of the single-sided coated paper (APP: Sinar DG), OP varnish (DIC: VSP M OP varnish) was applied at a rate of 3 g / m. 2 The coating was carried out using a bar coater so that the coating became as shown in the figure, and then dried for 2 minutes at 100° C. The other conditions were the same as in Example 1, and a lid laminate sheet of Example 2 was obtained.

[0039] Example 3 A lid laminate sheet of Example 3 was obtained in the same manner as Example 1, except that the aluminum vapor deposition layer of Example 1 was replaced with silica (SiO2) formed to a thickness of 50 nm by vacuum deposition.

[0040] Example 4 A laminated sheet for a lid of Example 4 was obtained in the same manner as Example 1, except that the aluminum vapor deposition layer of Example 1 was formed by vacuum vapor deposition of alumina (Al2O3) to a thickness of 50 nm.

[0041] Example 5 The same procedure as in Example 1 was repeated except that an anchor coat layer (a mixed solution of acrylic polyol, γ-isocyanate propyltrimethoxysilane, and aliphatic xylene diisocyanate) was applied with a bar coater so that the thickness after drying would be 1 μm, and then dried at 100°C for 1 minute, to obtain a laminated sheet for a lid body of Example 5.

[0042] (Comparative Example 1) Basis weight 80g / m 2 The coating gas barrier layer liquid was applied to the coating surface of one-side coated paper (APP: Sinar DG) at a coating amount of 15 g / m. 2 The coated gas barrier layer was formed by applying a urethane adhesive at a coating amount of 2 g / m2. 2After coating and drying at 100° C. for 1 minute, a 30 μm LLDPE film was dry laminated to obtain a lid laminate sheet of Comparative Example 1. <Gas barrier layer coating liquid> Pure water: 90 parts by weight. Polyvinyl alcohol (PVA-105): 10 parts by weight. Kaolin (Imerys Varisurf HX): 100 parts by weight.

[0043] (Comparative Example 2) Basis weight 80g / m 2 On the paper side of the single-sided coated paper (APP: Sinar DG), OP varnish (DIC: VSP M OP varnish) was applied at a rate of 3 g / m. 2 The coating was carried out using a bar coater so that the coating had a viscosity of 100° C., and then dried for 2 minutes at 100° C. The other conditions were the same as in Comparative Example 1, and a lid laminate sheet of Comparative Example 2 was obtained.

[0044] (Comparative Example 3) Basis weight 80g / m 2 On the coating surface of one-sided coated paper (Sinar DG, manufactured by APP), aluminum was formed to a thickness of 50 nm using a vacuum deposition machine, and then urethane adhesive was applied to the aluminum deposition layer at a rate of 2 g / m. 2 After coating and drying at 100° C. for 1 minute, a 30 μm LLDPE film was dry laminated to obtain a lid laminate sheet of Comparative Example 3.

[0045] Comparative Example 4 A lid laminate sheet of Comparative Example 4 was obtained in the same manner as Comparative Example 3, except that silica (SiO2) was formed to a thickness of 50 nm using a vacuum deposition machine.

[0046] (Comparative Example 5) A lid laminate sheet of Comparative Example 5 was obtained in the same manner as Comparative Example 3, except that alumina (Al2O3) was formed to a thickness of 50 nm using a vacuum deposition machine.

[0047] (Comparative Example 6) Basis weight 80g / m 2Anchor coating solution 1 was applied to the coating surface of one-sided coated paper (Sinar DG, manufactured by APP) using a bar coater so that the thickness after drying would be 1 μm, and then dried at 100°C for 1 minute. After that, a urethane adhesive was applied to the anchor coating surface at a rate of 2 g / m. 2 After coating and drying at 100° C. for 1 minute, a 30 μm LLDPE film was dry laminated to obtain a lid laminate sheet of Comparative Example 6.

[0048] (Oxygen permeability measurement) The lid laminate sheets of Examples 1 to 5 and Comparative Examples 1 to 6 were stored at room temperature of 23°C and relative humidity of 50%, and samples were stored at 5°C for 3 hours and then stored at 40°C and relative humidity of 90% for 1 hour, and the oxygen permeability of each sample was measured by the MOCON method. The measurement conditions for the MOCON method were a temperature of 30°C and a relative humidity of 70%.

[0049] The results are shown in Table 1. In the samples of Comparative Example 1 and Comparative Example 2, where the gas barrier layer is a coating film, the presence of OP varnish reduces the amount of change in oxygen permeability. However, even if the amount of change is small, it is still within 10 cc / m 2 ·atm·day, and the rate of change is over 65%. Moreover, in Comparative Examples 3 to 5, which do not have an anchor coat layer, the gas barrier layer is not well formed, and all of them are out of range. In contrast, in Examples 1 to 6, which had an anchor coat layer and a gas barrier layer made of a metal or inorganic oxide film, almost no change was observed regardless of whether or not OP varnish was used.The above results demonstrate the effectiveness of the present invention.

[0050] [Table 1] [Explanation of symbols]

[0051] 10. Laminated sheet for lid 101 Heat seal layer 102 Gas barrier layer 103 Anchor coat layer 104...Paper base material 200 Chilled food packaging containers 201 Lid 202... Container body

Claims

1. A lid laminate sheet used in a lid of a packaging container for chilled foods, the lid comprising a container body having an opening and a lid covering the opening, the lid laminate sheet comprising at least a heat seal layer, a gas barrier layer, an anchor coat layer and a paper base material in this order, the gas barrier layer being a vapor-deposited layer of a metal or metal oxide, the anchor coat layer containing a polyvinyl alcohol-based resin or a polyurethane-based resin, the mass of the paper base material being 50% or more of the mass of the lid laminate sheet, and the sheet having an oxygen permeability of 5 cc / m or less after being stored at a temperature of 5°C and then stored in an atmosphere at a temperature of 40°C and a relative humidity of 90%. ２ A laminated sheet for a lid body, characterized in that it has a temperature of 1000 to 2000°C (atm·day) or less.

2. 2. The laminate sheet for a lid according to claim 1, wherein the anchor coat layer contains a polyurethane resin.

3. The lid laminate sheet according to claim 1 or 2, further comprising an OP varnish layer on the surface of the paper substrate opposite to the surface on which the anchor coat layer is formed.

4. After storing at a temperature of 5°C and then storing in an atmosphere at a temperature of 40°C and a relative humidity of 90%, the oxygen permeability is 5 cc / m ２ The laminated sheet for lids according to any one of claims 1 to 3, characterized in that the oxygen permeability is not more than 2 cc / m 2 ·atm·day and the change in oxygen permeability is within 2 cc / m 2 ·atm·day compared to the oxygen permeability before storage.

5. After storing at a temperature of 5°C and then storing in an atmosphere at a temperature of 40°C and a relative humidity of 90%, the oxygen permeability is 5 cc / m ２ The laminated sheet for lids according to any one of claims 1 to 4, characterized in that the oxygen permeability is less than 1 / 2 atm / day and the rate of change in oxygen permeability is within 20% compared to the oxygen permeability before storage.

6. 6. The laminate sheet for a lid body according to claim 1, wherein the gas barrier layer is an aluminum vapor deposition layer.

7. 6. The laminate sheet for a lid body according to claim 1, wherein the gas barrier layer is an aluminum oxide (alumina) vapor-deposited layer.

8. The gas barrier layer is made of silica (SiO ２ 6. The laminated sheet for a lid body according to claim 1, wherein the laminated sheet is a vapor-deposited layer.

9. A lid body using the laminated sheet for lid body according to any one of claims 1 to 8.

10. A packaging container for chilled food, comprising the lid according to claim 9.

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