JP2023077763A - Laminated sheet for lid, lid, food packaging container and packaged food product - Google Patents

Abstract

To provide a lid used in a packaging container for food, containing a paper substrate, and excellent in openability.SOLUTION: A lid laminated sheet 10 according to an embodiment of the present invention is a lid laminated sheet used for a lid of a food packaging container including a container body provided with an opening and the lid covering the opening. The lid laminated sheet 10 includes a water-resistant functional layer 6, a printed layer 5, a paper base material 4, a support layer 2, and a heat seal layer 1 in this order. The mass of the paper base 4 is larger than the mass of any other layer included in the lid laminated sheet 10, and the Young's modulus in MD and TD of the lid laminated sheet 10 are both in the range of 1.2 to 2.9 GPa, and the thickness of the lid laminated sheet is in the range of 80 to 205 μm.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a laminated sheet for a lid, a lid, a food packaging container, and a packaged food.

In addition to changes in household composition and lifestyles due to the trend toward nuclear families in recent years, progress in distribution, freezing and refrigeration technology has contributed to the spread of cooked or processed chilled foods sold at convenience stores and supermarkets. Demand for frozen foods is growing. At the same time, the demand for packaging containers for chilled and frozen foods is also increasing.

On the other hand, as the reduction of plastic waste is progressing, there is a growing demand for food packaging containers that use paper as a base material, which has a low environmental impact and is a renewable resource. Packaging containers for chilled foods are also required to use paper-made packaging containers using paper as a base material.

For example, Patent Literature 1 discloses a food packaging material obtained by laminating two gas barrier layers using ethylene-modified polyvinyl alcohol resin on a paper substrate.

JP 2009-184138 A

An object of the present invention is to provide a lid that is used for a food packaging container, contains a paper substrate, and is excellent in opening properties.

According to the first aspect of the present invention, there is provided a laminated sheet for a lid used for the lid of a food packaging container comprising a container body provided with an opening and a lid covering the opening, the laminated sheet being water resistant a functional layer, a printed layer, a paper substrate, a support layer, and a heat-sealing layer in this order, and the mass of the paper substrate is equal to any other layer contained in the laminated sheet for lid , the Young's modulus in MD and TD of the lid laminated sheet are both in the range of 1.2 to 2.9 GPa, and the thickness of the lid laminated sheet is in the range of 80 to 205 μm. An inner lid laminate sheet is provided.

According to a second aspect of the present invention, there is provided a lid made of the laminated sheet for lid.

According to a third aspect of the present invention, there is provided a food packaging container comprising a container body provided with an opening and the lid covering the opening, wherein the support layer comprises the paper substrate and the food A food packaging container positioned between the interior space of the packaging container is provided.

According to a fourth aspect of the present invention, there is provided a packaged food comprising the food packaging container and food contained in the food packaging container.

ADVANTAGE OF THE INVENTION According to this invention, it is used for the packaging container for foodstuffs, the lid|cover body which contains a paper base material and was excellent in the unsealability is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view schematically showing an example of a laminated sheet for a lid according to a first embodiment of the present invention; FIG. 11 is a partial cross-sectional view schematically showing a laminated sheet for a lid according to a modified example. Sectional drawing which shows roughly the packaging container for food which concerns on 3rd Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. Embodiments described below are more specific to any of the above aspects. Elements having the same or similar functions are denoted by the same reference numerals, and overlapping descriptions are omitted.

[First embodiment]
FIG. 1 is a cross-sectional view schematically showing an example of a laminated sheet for a lid according to a first embodiment of the present invention.
A lid laminated sheet 10 shown in FIG. 1 is used as a lid in a food packaging container comprising a container body provided with an opening and a lid covering the opening. That is, the lid laminated sheet 10 is a lid material that is used as a lid itself or a portion cut out from it is used as a lid.

The laminate sheet for lid 10 comprises a heat seal layer 1, a support layer 2, a gas barrier layer 3, a paper substrate 4, a printing layer 5, and a functional layer having water resistance (water resistance layer) 6. Including in order. As described above, the lid laminate sheet 10 includes the gas barrier layer 3 between the paper base material 4 and the support layer 2 . and the heat seal layer 1. Alternatively, the gas barrier layer 3 may be interposed between the support layer 2 and the heat seal layer 1 . Note that the gas barrier layer 3 may be omitted.
Each layer included in the lid laminate sheet 10 will be described below.

(Paper substrate)
The lid laminate sheet 10 includes a paper base material 4 . The mass of the paper base material 4 is greater than the mass of any other layers included in the lid laminated sheet 10 . The ratio of the mass of the paper base material 4 to the mass of the lid laminated sheet 10 is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. % is more preferred. According to one example, this proportion is less than or equal to 80%, according to another example less than or equal to 70%, and according to yet another example less than or equal to 65%.

When the layers other than the paper base material 4 included in the lid laminated sheet 10 are classified into a layer made of plastic and other layers, the mass of the paper base material 4 is the total mass of the layers made of plastic and It is preferably larger compared to the total mass of the other layers. In this case, in Japan, the lid laminate sheet 10 can be treated as paper under the Containers and Packaging Recycling Law.

Here, the above classification follows the "Explanatory material of the Containers and Packaging Recycling Law". In other words, "plastic" is a material that contains a polymer as an essential component and is shaped and manufactured by utilizing fluidity during processing. Paints and adhesives are not included in plastics, as they are irrelevant to the concept of "shaping". Therefore, in the example shown in FIG. 1, the support layer 2 and the heat seal layer 1 attached thereto are "layers made of plastic". In the example shown in FIG. 1, the printing layer 5 formed from ink, the functional layer 6 formed by coating, and the adhesive layer (not shown) made of adhesive are "other layers."

On the other hand, the gas barrier layer 3 is classified according to the following cases. That is, in the example shown in FIG. 1, if the gas barrier layer 3 is a layer formed on the paper base material 4 by coating or vapor deposition, it can be treated as a "paper base material" according to the above explanatory materials. are treated as "other layers" here. For example, when the paper base material 4 is a barrier paper with the gas barrier layer 3 coated or vapor-deposited on one surface thereof, the gas barrier layer 3 is the "other layer". Further, when a polymer film produced by at least melt molding such as extrusion is used for the barrier layer, it is a "layer made of plastic". On the other hand, in the example shown in FIG. 1, when the gas barrier layer 3 is a layer formed on the support layer 2 by coating, vapor deposition, or melt molding, it is the same "layer made of plastic" as the support layer 2. . For example, when the support layer 2 is a gas barrier film having a gas barrier layer 3 formed on one surface thereof, the gas barrier layer 3 is a "layer made of plastic".

The basis weight of the paper substrate 4, that is, the mass per area is preferably in the range of 40 to 160 g/m ² , more preferably in the range of 50 to 160 g/m ² . When the grammage of the paper base material 4 is increased, the lid body tends to be hard and the unsealability tends to deteriorate. If the grammage is reduced, the strength of the lid is reduced.

The thickness of the paper substrate 4 is preferably in the range of 40 to 160 µm, more preferably in the range of 45 to 150 µm. If the paper base material 4 is too thick, the lid tends to be hard and unsealable. If the paper base material 4 is too thin, the strength of the lid tends to decrease. For example, when the thickness of the heat seal layer 1 is in the range of 30 to 50 μm, the thickness of the paper substrate 4 is preferably in the range of 40 to 160 μm, more preferably in the range of 45 to 150 μm. more preferred.

When the basis weight of the paper base material 4 is increased, the ratio of the mass of the paper base material 4 to the mass of the lid laminated sheet 10 also increases. However, when the basis weight of the paper base material 4 is increased, the amount of carbon dioxide emissions associated with the manufacture of the paper base material 4 and the disposal of the lid laminated sheet 10 increases.

The paper base material 4 is not particularly limited as long as it contains plant-derived pulp as a main component. Examples of the paper base material 4 include coated paper such as high quality paper, medium quality paper, lightly coated paper, single gloss paper, bleached and unbleached kraft paper (acidic paper or neutral paper).

The paper substrate 4 is preferably coated paper having a coat layer on at least one surface. That is, the paper substrate 4 is preferably single-sided coated paper or double-sided coated paper. The surface of the coated paper provided with the coat layer is superior in smoothness compared to the surface of the paper not provided with the coat layer.

When the paper substrate 4 is a coated paper having a coat layer on one side, the print layer 5 can be provided on the coat layer, for example. In this case, it is easy to display a high quality image on the print layer 5 . In addition, by providing the coat layer, the surface of the base of the functional layer 6 becomes smooth, so that the water resistance of the functional layer 6 is also improved. Moreover, when a coat layer is provided, it is possible to suppress the material of the printing layer 5 and the material of the functional layer 6 from soaking into the paper substrate 4 .

When the paper substrate 4 is coated paper having a coat layer on one side, the gas barrier layer 3 can be provided on the coat layer, for example. By doing so, the adhesion of the gas barrier layer 3 to the paper substrate 4 is improved. In addition, the smoothness of the coat layer facilitates uniform formation of the adhesive layer containing the adhesive, so that the adhesion of the gas barrier layer 3 to the paper substrate 4 is improved and the amount of adhesive used can be reduced. Moreover, the thickness of the gas barrier layer 3 required for exhibiting barrier properties can be reduced.

When coated paper having coat layers on both sides is used as the paper base material 4, it becomes easy to display a high-quality image on the printing layer 5, and the water resistance of the functional layer 6 can be improved. In addition, it becomes easy to achieve excellent adhesion between the paper substrate 4 and the gas barrier layer 3 .

The coat layer contains resin. Examples of the resin contained in the coating layer include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α polymerized using a metallocene catalyst (single-site catalyst). - olefin copolymers, polypropylene, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-ethyl acrylate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-propylene copolymers , methylpentene polymer, acid-modified polyolefin resin obtained by modifying polyolefin resin such as polyethylene and polypropylene with unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid, polyethylene terephthalate resin, polybutylene terephthalate thermoplastic resins such as resins, nylon resins, and styrene-butadiene rubbers; These resins may be used in combination of two or more, or may be used by copolymerizing two or more. The coating layer may further contain additives such as fillers such as clay, kaolin, calcium carbonate, talc, mica, and titanium oxide.

The thickness of the coating layer is preferably in the range of 0.5 to 50 µm, more preferably in the range of 1 to 15 µm.

(support layer)
The support layer 2 improves the strength of the lid laminate sheet 10 .
The support layer 2 is made of, for example, polybutylene terephthalate (PBT), polyamide, polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer, polyacrylonitrile (PAN), polymethylpentene (PMP), polyvinyl alcohol resin, olefin resin, or Contains unsaturated polyester resin. The support layer 2 may have a single layer structure or a multilayer structure.

The support layer 2 may be a non-stretched film or a stretched film such as a biaxially stretched film. If it is a stretched film, it is preferred to utilize a biaxially stretched film. This is because biaxial stretching reduces variations in physical properties such as breaking strength in the in-plane direction of the film compared to uniaxial stretching.

The support layer 2 may further contain additives such as curing agents, fillers, antiblocking agents, and antistatic agents. As the material for the support layer 2, a material that is cured by irradiation with active energy rays such as ultraviolet rays and electron beams can also be used.

The support layer 2 preferably contains at least one of polybutylene terephthalate (PBT) and polyamide. For example, the support layer 2 is a layer made of polybutylene terephthalate, a layer made of polyamide, or a laminate containing at least one of them. Polyamides, for example, contain an aliphatic backbone. Polyamides are, for example, nylons such as nylon 6, nylon 66, nylon 612, nylon 11, nylon 12, and nylon 46.

When the support layer 2 contains at least one of polybutylene terephthalate (PBT) and polyamide, the ratio of the total mass of polybutylene terephthalate and polyamide to the mass of the support layer 2 is preferably 50% by mass or more. % or more is more preferable. When the thickness of the support layer 2 is constant, increasing this ratio increases the piercing strength of the lid.

The thickness of the support layer 2 is preferably in the range of 3 to 60 μm, more preferably in the range of 10 to 30 μm. When the support layer 2 is thickened, it becomes easy to increase the piercing strength of the lid, but it becomes difficult to increase the ratio of the mass of the paper substrate 4 to the mass of the laminated sheet 10 for lid.

The breaking strength of the support layer 2 is preferably greater than the heat sealing strength between the lid and the container body. Here, the fact that the breaking strength of the support layer 2 is greater than the heat seal strength between the lid and the container body means that in MD (Machine Direction), the breaking strength of the support layer is greater than that between the lid and the container body. It means that the breaking strength of the supporting layer is greater than the heat sealing strength and that the breaking strength of the support layer is greater than the heat sealing strength between the lid and the container body in TD (Transverse Direction).

The breaking strength of the support layer 2 is a tensile force obtained by a measuring method specified in JIS Z1707:2019 "General Rules for Plastic Films for Food Packaging". The tensile force (N/15 mm) is a value obtained by converting the maximum force when the test piece breaks into a force (N/15 mm) equivalent to the width of the test piece of 15 mm. The heat seal strength between the lid and the container body will be described later.

When the breaking strength of the support layer 2 is greater than the heat seal strength between the lid and the container body, the paper is less likely to peel off when the lid is peeled off from the container body. For example, when the breaking strength of the support layer 2 is greater than 30 N/15 mm, paper peeling can be suppressed up to a heat seal strength of about 30 N/15 mm. Here, "paper peeling" means that when the lid is peeled off from the container body, cohesive failure of the paper base material occurs and part of the lid remains on the container body. If paper peeling occurs, it may become difficult to take out the contents accommodated in the container body.

The heat seal strength is adjusted according to the use and purpose of the packaging container. For example, the heat seal strength may be reduced in order to impart easy openability. Therefore, the breaking strength of the support layer 2 need not exceed 30 N/15 mm. Although the breaking strength of the support layer 2 is not particularly limited, it is preferably in the range of 10 to 100 N/15 mm, more preferably in the range of 25 to 85 N/15 mm. Increasing the above-mentioned breaking strength increases the effect of reinforcing the laminate in order to suppress paper peeling. However, if the thickness of the support layer 2 is increased in order to increase the breaking strength, the production of the support layer 2 and the disposal of the lid laminated sheet 10 increase the amount of carbon dioxide emissions and the cost.

(Gas barrier layer)
The gas barrier layer 3 has gas barrier properties such as oxygen barrier properties and water vapor barrier properties. The gas barrier layer 3 prevents gases such as oxygen, water vapor, and aromatic components outside the container from penetrating into the packaged food described later. As a result, the gas barrier layer 3 suppresses deterioration of the food, which is the content of the packaged food. In addition, the gas barrier layer 3 suppresses the diffusion of odor components and the like of the contents to the outside of the container in the packaged food. According to one example, the gas barrier layer 3 has an oxygen permeability of 0.1 to 100 cc/m ² /day/atm in an atmosphere with a temperature of 30° C. and a relative humidity of 70%.

The gas barrier layer 3 is, for example, a metal layer, an inorganic oxide layer, a resin-containing layer, or a combination of two or more thereof. When microwave heating by a microwave oven is assumed, the gas barrier layer 3 is preferably an inorganic oxide layer, a resin-containing layer, or a combination thereof.

The gas barrier layer 3 may be formed by coating, may be formed by melt molding, or may be formed by depositing an inorganic oxide. Alternatively, the gas barrier layer 3 may be a metal foil such as an aluminum foil, or may be a vapor-deposited metal such as aluminum.

Examples of inorganic oxides include silicon oxide, boron oxide, and metal oxides such as aluminum oxide, magnesium oxide, calcium oxide, potassium oxide, tin oxide, sodium oxide, titanium oxide, lead oxide, zirconium oxide, and yttrium oxide. can use things.

The resin-containing layer can be formed, for example, by coating. In this case, a coating liquid containing resin such as polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyvinylidene chloride, polyacrylonitrile, and epoxy resin can be used. Additives such as organic or inorganic particles, layered compounds, and curing agents may be added to the coating liquid.

When forming the resin-containing layer by melt molding, for example, extrusion molding techniques such as T-die and inflation can be used. In melt molding, for example, the above resin or a mixture of the above resin and additives is heated and melted, and the gas barrier layer 3 is processed into a film or sheet by T-die, inflation, or the like. This film or sheet is attached to at least one of the paper substrate 4 and the support layer 2 .

The gas barrier layer 3 may be interposed between the paper base material 4 and the support layer 2 of the laminated sheet for lid 10 by using a gas barrier film composed of the support layer 2 having the gas barrier layer 3 on one side. good. In this case, the gas barrier film is attached to the paper substrate 4 so that the gas barrier layer 3 and the paper substrate 4 face each other. When the gas barrier layer 3 is a resin-containing layer, the gas barrier film and the support layer 2 may be formed by co-extrusion.

The gas barrier layer 3 is interposed between the paper base material 4 of the lid laminate sheet 10 and the support layer 2 by using a barrier paper made of a paper base material 4 having the gas barrier layer 3 on one side. good too. The paper base material 4 constituting the barrier paper may be coated paper having a coat layer on at least one surface. When the paper base material 4 constituting the barrier paper has a coat layer only on one surface, the gas barrier layer 3 may be provided on the coat layer, or the surface of the paper base material 4 on which the coat layer is not formed. may be provided above.

The thickness of the gas barrier layer 3 is in the range 0.01 to 30 μm according to one example, and in the range 0.1 to 12 μm according to another example.

(Print layer)
The printed layer 5 is a layer formed for practical use of the lid laminate sheet 10 or the lid as a commercial product. The printing layer 5 includes, for example, conventionally used ink binder resins such as urethane, acrylic, nitrocellulose, rubber, and vinyl chloride, various pigments, extenders, plasticizers, desiccants, and stabilizers. It is a layer composed of ink to which additives such as agents are added, and displays patterns such as letters and pictures. As a method for forming the printed layer 5, for example, known printing methods such as offset printing, gravure printing, and silk screen printing, and known coating methods such as roll coating, knife edge coating, and gravure coating are used. be able to.

The thickness of the printing layer 5 is not particularly limited, but is in the range of 0.1 to 5 μm in one example, and in the range of 0.2 to 1 μm in another example.

(Functional layer having water resistance)
The functional layer (water-resistant layer) 6 having water resistance suppresses the penetration of liquids outside the container such as moisture and oil due to dew condensation etc. into the lid in the packaged food described later, and the liquid is prevented from penetrating into the printed layer 5. It is a layer that suppresses reaching the layers such as the paper substrate 4 and the like. The functional layer 6 prevents the liquid outside the container from reaching the layers such as the printed layer 5 and the paper substrate 4, thereby preventing, for example, deterioration, breakage, or loss of adhesion of these layers.

According to one example, the functional layer 6 is formed on the printed layer 5 to increase the water absorbency of the partially laminated sheet, which is the portion from the functional layer 6 to the paper substrate 4 in the lid laminated sheet 10. Control. The functional layer 6 preferably has water resistance such that the water absorbency of the laminated sheet for a lid formed by the Cobb method described below is 20 g/m ^{2 or} less.

Here, the water absorbency is defined in JIS P8140: 1998 "Paper and paperboard-Water absorbency test method-Cobb method", with the surface of the functional layer 6 as the measurement surface, and the contact time between the test piece and water. It is the water absorbency obtained when 300 seconds. As described above, the water absorbency is preferably 20 g/m ² or less, more preferably 10 g/m ² or less, and even more preferably 5 g/m ² or less. The lower limit of this water absorbency is ideally 0 g/m ² . According to one example, this water absorption is greater than or equal to 1 g/m ² .

The functional layer 6 is preferably an overprint varnish layer (hereinafter referred to as "OP varnish layer").
According to one example, the functional layer 6 contains a water-resistant resin. As the water-resistant resin, any resin capable of achieving the above-described water absorbency can be used without limitation. Examples of water-resistant resins include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and polyolefin resins such as vinyl chloride-vinyl acetate copolymers, silicone resins, acrylic resins, epoxy resins, Polyester-based resins, cellulose-based resins, or urethane-based resins can be used. The functional layer 6 can be obtained, for example, by applying a paint containing a water-resistant resin onto the paper substrate 4 having the printed layer 5 formed thereon by a known method. In addition to the water-resistant resin, the paint may further contain additives such as pigments, dyes, curing agents, leveling agents, anti-blocking agents, and lubricating agents, solvents, and the like.

The functional layer 6 preferably has high abrasion resistance and scratch resistance so as to maintain sufficient water resistance. From this point of view, it is preferable that the thickness of the functional layer 6 and the coating amount of the coating material thereof are larger than the thickness of the normal OP varnish layer and the coating amount of the normal OP varnish. Here, the "coating amount" is the solid content mass per area.

For example, in the lid laminated sheet 10 shown in FIG. 1, the paint for forming the functional layer 6 is preferably applied in an amount of 0.2 g/m ² or more. /m ² or more is more preferable. This paint is applied so that the coating amount is, for example, 10 g/m ² or less. The thickness of the functional layer 6 is preferably 0.2 μm or more, more preferably 2.0 μm or more. The thickness of the functional layer 6 is, for example, 10 μm or less. The functional layer 6 may be provided on the printed layer 5 by lamination.

(Heat seal layer)
The heat-seal layer 1 may be any material as long as it can heat-seal the lid 21 to the container body 22 of the food packaging container 20 shown in FIG. 3 to be described later, thereby sealing the container. The ease of peeling of the lid from the container body can be adjusted according to, for example, the peeling mechanism of the heat seal layer, such as interfacial peeling or cohesive failure, and the heat seal strength described later. As the heat seal layer 1, for example, a film made of ethylene-vinyl acetate (EVA), ionomer resin, or other polyolefins is used. The heat seal layer 1 is preferably a layer containing at least one of linear low density polyethylene (LLDPE), very low density linear polyethylene (Very Low Density Polyethylene; VLDPE), or polypropylene. be.

A sealant layer having an easy peel function (simple peeling function) can also be used as the heat seal layer 1 . Easy peelability indicates excellent re-peelability and easy-openability.

The heat seal layer 1 is provided on the support layer 2 by lamination, for example. The heat seal layer 1 can also be formed by applying heat seal varnish on the support layer 2 .

The thickness of the heat seal layer 1 is not particularly limited. The thickness of the heat seal layer 1 may according to one example be in the range of 0.5 to 60 μm and according to another example to be in the range of 1 to 30 μm.

(adhesive layer)
The lid laminate sheet 10 may further include one or more adhesive layers.
For example, the lid laminate sheet 10 may include an adhesive layer between the heat seal layer 1 and the support layer 2 for bonding them. Alternatively, the lid laminate sheet 10 may include an adhesive layer between the support layer 2 and the gas barrier layer 3 to bond them together. Alternatively, the lid laminate sheet 10 may include an adhesive layer between the gas barrier layer 3 and the paper base material 4 for bonding them. Alternatively, the lid laminate sheet 10 may include two or more adhesive layers described above.

As the material of the adhesive layer, an adhesive resin or an adhesive that can obtain the required adhesive strength is appropriately selected and used according to the material of the layer to be adhered through the adhesive layer.

Examples of the adhesive resin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and copolymers with ethylene-α-olefin polymerized using a metallocene catalyst; Vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-maleic acid copolymer, etc. One or more resins selected from ethylene-unsaturated carboxylic acid copolymers; and ionomer resins can be used.

The adhesive is, for example, an adhesive composition obtained by mixing a first composition containing a main agent and a solvent and a second composition containing a curing agent and a solvent. The adhesive layer obtained from this adhesive contains a cured product produced by the reaction of the main agent and the curing agent in the adhesive composition.

A polyol can be mentioned as an example of the main agent. Examples of curing agents include isocyanate compounds. Examples of adhesives include ether-based two-component reactive adhesives and ester-based two-component reactive adhesives.

The cured product of the ether-based two-component reactive adhesive is, for example, polyether polyurethane. A polyether polyurethane is produced by reacting a polyether polyol as a main agent with an isocyanate compound as a curing agent.

The cured product of the ester-based two-liquid reactive adhesive is, for example, polyester polyurethane and polyester. A polyester polyurethane is produced by reacting a polyester polyol as a main agent with an isocyanate compound as a curing agent.

Acrylic polyol may be used as the main agent in the two-component reactive adhesive. In addition, the above adhesive composition does not need to contain a solvent as long as it melts or lowers in viscosity when heated.

The mass per area of the lid laminated sheet 10 is preferably in the range of 50 to 160 g/m ² , more preferably in the range of 60 to 140 g/m ² , and more preferably 90 to 130 g/m 2 . It is more preferably in the range of ^m2 . Decreasing this value reduces the strength of the lid. If this value is too large, the lid tends to be hard and unsealable. Also, increasing this value increases the cost and carbon dioxide emissions associated with manufacturing and exhaust.

The above-described lid laminated sheet 10 has a Young's modulus in both MD and TD within the range of 1.2 GPa to 2.9 GPa. The Young's modulus of the lid laminate sheet 10 is preferably in the range of 1.2 to 2.6 GPa. It is preferable that the difference between the Young's modulus in MD and the Young's modulus in TD is small.

Here, the "Young's modulus" of the lid laminated sheet 10 or the lid is the tensile strength obtained by the method specified in JIS K7161-1: 2014 "Plastics - Determination of tensile properties - Part 1: General rules". It is the value obtained by dividing the stress by the tensile strain obtained by the above method.

The Young's modulus of the lid laminate sheet 10 can be adjusted, for example, according to the material of each layer included in the lid laminate sheet 10 .

In addition, the thickness of the lid laminated sheet 10 described above is in the range of 80 μm to 205 μm. The thickness of the lid laminate sheet 10 is preferably in the range of 80 μm to 180 μm, more preferably in the range of 90 μm to 150 μm.

By the way, a packaging material having a paper base material is often used because of its low environmental load. However, when a packaging material having a paper base material is used as a lid of a packaging container, peeling of the paper may occur when the lid is opened. A support layer containing plastic may be provided between the paper base material and the heat-sealing layer as a cover that is less prone to paper peeling. However, in a lid provided with such a support layer, when the weight of the paper base material in the weight of the packaging material is increased, the rigidity of the lid tends to increase as the rigidity of the paper increases. When the rigidity of the lid is high, that is, when the flexibility of the lid is low, the opening performance may not be excellent, for example, the lid may feel stuck when unsealed, or force may be required for opening. Further, if the rigidity of the lid is too low, the above-mentioned peeling of the paper may occur, the lid may stretch, or a portion of the lid may be torn off. Thus, when the rigidity of the lid body is too low, the unsealability may not be excellent.

As described above, the rigidity of the lid contributes to the ease of opening. Moreover, the rigidity of the lid is proportional to the Young's modulus of the lid. However, the inventors have found that Young's modulus alone does not contribute to unsealability. For example, even if the Young's modulus is within the above-described range, if the lid is too thick, the opening may be unsatisfactory, such as feeling stuck when opening or requiring force to open. . Further, even when the Young's modulus is within the above-described range, if the cover is too thin, the above-mentioned peeling of the paper may occur, the cover may be elongated, or a portion of the cover may be torn off. The rigidity of the lid can be rephrased as stiffness of the lid. Stiffness includes bending stiffness, Clark stiffness and pure bending stiffness.

On the other hand, in the lid laminate sheet 10 described above, both the Young's moduli in MD and TD are within the ranges described above, and the thickness of the lid laminate sheet 10 is also within the ranges described above. Therefore, such a laminate sheet 10 for a lid is excellent in openability.

In addition, in the above-described lid laminate sheet 10, when the support layer 2 contains at least one of polybutylene terephthalate and polyamide, it is possible to realize a lid having particularly excellent puncture strength.

Here, the "penetration strength" of the lid laminate sheet or lid is determined by the method specified in JIS Z1707:2019 "General Rules for Plastic Films for Food Packaging". This is a value obtained by piercing from the layer 6 side. Specifically, a needle having a diameter of 1 mm and a semi-circular tip is pierced into the lid laminated sheet or lid from the functional layer 6 side at a speed of 50 mm / min until the needle penetrates. Measure maximum force. This measurement is performed multiple times and the arithmetic mean of the maximum force is obtained as the puncture strength. In addition, unless otherwise specified, the "penetration strength" means a value obtained when the laminate sheet for lid or the lid is pierced from the functional layer side.

The puncture strength of the lid laminated sheet 10 or the lid is preferably 5.5 N or more, more preferably 7.5 N or more. This piercing strength is, for example, 25 N or less.

In addition, the piercing strength obtained when a needle is pierced from the heat-seal layer side of the lid laminated sheet or lid used in the food packaging container is generally It need not be as high as the puncture strength to be obtained. Moreover, the piercing strength obtained when a needle is pierced from the heat seal layer side is generally higher than the piercing strength obtained when a needle is pierced from the functional layer side.

Moreover, when the laminated sheet 10 for lids mentioned above is provided with the gas barrier layer 3, it is excellent in opening property, and also has high gas barrier property. Furthermore, such a laminate sheet 10 for a lid is less likely to deteriorate gas barrier properties, particularly oxygen barrier properties. This will be explained below.

Food packaging containers are sometimes desired to have excellent oxygen barrier properties to prevent oxygen from entering from the outside, in order to suppress oxidation of the food packed therein. In such food packaging containers, the lid is also required to have oxygen barrier properties.

In order to impart gas barrier properties against oxygen and the like to a lid made of paper as a base material, for example, a metal foil or metal deposition film made of a metal such as aluminum is often provided as a gas barrier layer on a paper base material. However, food packaging containers with a lid containing a metal layer cannot be inspected for metallic foreign matter by a metal detector after filling, and cannot be incinerated as paper because they contain metal, and can be reused as waste paper There is a problem that it cannot be used for packaging containers such as chilled foods that are expected to be heated and cooked in a microwave oven.

As noted above, some gas barrier layers do not include a metal layer. As such gas barrier layers, those containing polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamides such as nylon MXD-6, and resins such as polyacrylonitrile are often used. A metal layer-less lid can avoid the above problems.

Regarding the distribution and storage temperature of chilled food, an optimum temperature range is set for each food, but generally it is within the range of 0 to 10°C. Packaged foods, which are chilled foods contained in food packaging containers, are delivered to consumers through various distribution channels after production. During this process, for example, from the time a consumer purchases a packaged food at a store until it is stored in the refrigerator at home, or from the time the consumer removes the packaged food from the refrigerator to the time the consumer starts cooking the packaged food. is placed in a normal temperature environment.

The present inventors have found that packaged foods in which chilled foods are accommodated in food packaging containers whose lids include a paper base material and a gas barrier layer, particularly packaged foods in which the gas barrier layer is a resin-containing layer are stored in a refrigerated state. It has been found that the gas barrier properties, particularly the oxygen barrier properties, of the lid are greatly reduced during the first few hours of exposure to the normal temperature environment. This is remarkable when the ratio of the mass of the paper substrate to the mass of the lid is large.

The inventors have found that the above problem is caused by dew condensation on the surface of the lid. That is, when the packaged goods under a refrigerated environment are exposed to a room temperature environment, dew condensation occurs on the outer surface of the lid, and the moisture reaches the gas barrier layer, damaging the gas barrier layer. As a result, the oxygen barrier property of the lid is lowered.

The lid laminated sheet 10 includes a functional layer 6 having water resistance. Therefore, in a packaged food using this laminated sheet for lid 10 as a lid material, it is difficult for moisture generated on the outer surface of the lid due to dew condensation to reach the gas barrier layer 3 . Therefore, in a packaged food using the lid laminated sheet 10 as a lid material, the gas barrier layer 3 is less likely to be damaged due to dew condensation on the outer surface of the lid, and the oxygen barrier property is less likely to be deteriorated.

In particular, the present inventors have found that when the lid contains a paper base material, paper peeling occurs when the lid is peeled off from the container body. I find it even easier. As described above, by making the breaking strength of the support layer 2 greater than the heat-sealing strength between the lid and the container body, paper peeling can be made difficult to occur.

In addition, the problems described above regarding the case where the contents are chilled foods may also occur when the contents are frozen foods. The configuration described here can produce the same effect as described above for the case where the content is chilled food, even when the content is frozen food.

<Modification>
Various modifications can be made to the laminated sheet for the lid. As described above, the laminated sheet for a lid according to the present embodiment may include a gas barrier layer between the paper substrate and the heat seal layer, and as described below with reference to FIG. A gas barrier layer may be included between the support layer and the heat seal layer. The matters described with reference to FIG. 1 can be applied singly or in combination to the laminated sheet for a lid according to the modified example described here.

FIG. 2 is a partial cross-sectional view schematically showing a laminated sheet for a lid according to a modified example.
The lid laminate sheet 11 shown in FIG. 2 is similar to the lid laminate sheet 10 described with reference to FIG. is similar to

That is, the lid laminated sheet 11 includes a heat seal layer 1, a gas barrier layer 3, a support layer 2, a paper substrate 4, a printing layer 5, and a functional layer having water resistance (water resistance layer) 6. in that order. The lid laminate sheet 11 has the same effect as the lid laminate sheet 10 described above.

[Second embodiment]
A lid according to the second embodiment of the present invention is a lid obtained from the laminated sheet for a lid according to the first embodiment or the modification described above. An example of the lid according to the second embodiment is the lid 21 described later with reference to FIG. The lid according to the present embodiment is excellent in openability, as described in relation to the lid laminate sheets 10 and 11 .

[Third embodiment]
FIG. 3 is a cross-sectional view schematically showing a food packaging container according to a third embodiment of the present invention. A food packaging container 20 shown in FIG. 3 includes a container body 22 having an opening, and a lid 21 covering the opening.

The container main body 22 is, for example, in the shape of a cylinder with a bottom. The container body 22 here includes a bottom portion, a body portion (or side wall portion) and a flange 22a. The flange 22a widens outward at the upper opening of the barrel.

The container body 22 contains, for example, an olefin resin such as polypropylene. The container body 22 may further contain a component such as an ethylene-vinyl alcohol copolymer in order to enhance its gas barrier properties. Moreover, the container body 22 may further contain additives, for example, additives for the purpose of improving workability, designability, and chemical durability.

The container body 22 may have a single-layer structure or a multi-layer structure. This multi-layer structure may be a two-layer structure or may include three or more layers. In the latter case, the multilayer structure may comprise, as an intermediate layer, a gas barrier layer, for example a layer containing a component such as the ethylene-vinyl alcohol copolymer mentioned above.

Paper can also be used for the container body 22 . When the contents contain a liquid material, the container body 22 includes a paper base material and a layer made of resin or the like provided on the surface facing the contents in order to prevent the liquid material from penetrating into the paper base material. A multi-layer structure including and can be adopted. As the material of the container body 22 containing the paper substrate, for example, paper leaves, paper dust, pulp, or used paper can be used. For molding into the container body 22, it is possible to use general-purpose techniques such as a method of folding and pasting a sheet containing paper leaves as in the manufacture of a paper pack, sheet press molding using a mold, and pulp molding. is. By using paper for the container body 22, it is possible to reduce the amount of carbon dioxide emissions associated with the production and disposal of the food packaging container 20 as a whole, thus reducing the burden on the environment.

The lid 21 is one of the lid laminated sheets 10 and 11, or one of them cut out. The lid body 21 is heat-sealed to the flange 22a via the heat-seal layer 1 after the contents are contained in the container body 22 . In this heat sealing, the sealing temperature, sealing pressure, and sealing time can be appropriately set.

[Fourth embodiment]
A packaged food according to the fourth embodiment of the present invention is obtained by accommodating food in the food packaging container according to the third embodiment. Foods to be accommodated are not particularly limited, but are preferably chilled foods or frozen foods. Chilled and frozen foods are, for example, cooked or processed foods. Chilled and frozen foods are, for example, grilled fish, boiled fish, or side dishes.

In this packaged food, as described above, the heat seal strength between the lid 21 and the container body 22 is preferably smaller than the breaking strength of the support layer 2 included in the lid 21 . This heat seal strength is preferably in the range of 5 to 60 N/15 mm, more preferably in the range of 10 to 50 N/15 mm. The difference between the breaking strength of the support layer 2 and the heat sealing strength between the lid 21 and the container body 22 is preferably within the range of 5 to 60 N/15 mm, and within the range of 10 to 40 N/15 mm. It is more preferable to have Here, the heat seal strength is a value obtained by the method specified in JIS Z0238:1998 "Test method for heat-sealable flexible packaging bags and semi-rigid containers".

In the production of this packaged food, the lid 21 is heat-sealed to the container body 22 before the lid 21 is heat-sealed to the container body 22, for example, after the contents are accommodated in the container body 22. Previously, the gas within container body 22 may be replaced by known methods. For example, the container body 22 may be filled with an inert gas. By appropriately changing the gas composition in the container, it is possible to suppress the growth of bacteria and extend the quality preservation period, to maintain the flavor and color of food for a long time by preventing oxidation, and to prevent the loss of vitamins. be able to. The replacement gas is appropriately selected according to the type of food that is the content. As the replacement gas, a mixed gas of oxygen gas, nitrogen gas and carbon dioxide gas is preferably used.

The lid contained in this packaged food is excellent in opening properties. Therefore, this packaged food is less likely to cause the contents to scatter or the like when opened.

The following describes tests conducted in relation to the present invention.
<1> Production of laminated sheet for lid (Example 1)
A laminate sheet 10 for a lid shown in FIG. 1 was manufactured by the following method.
First, a single-sided coated paper having a basis weight of 52.3 g/m ² was prepared as the paper base material 4 . A print layer 5 and a functional layer 6 were sequentially formed on the coat layer of the paper substrate 4 using a gravure multicolor printer. The printing layer 5 was formed using normal printing ink. The amount of printing ink applied was 1.0 g/m ² . The functional layer 6 was formed using an OP varnish containing nitrocellulose-based resin and polyethylene-based granular wax as main components. The coating amount of the OP varnish was 0.5 g/m ² . The single-sided coated paper is a paper obtained by coating imitation paper having a basis weight of 37.3 g/m ² with the coating layer solution so that the weight per area is 15 g/m ² . The coating layer solution contains polyvinyl alcohol (PVA) and styrene-butadiene rubber (SBR) as main components, and further contains silica and layered silicate. The thickness of the single-sided coated paper was 48 μm.
Next, a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 μm and a mass per area of 16.8 g/m ² was prepared as the support layer 2 . By vapor-depositing alumina as an inorganic oxide on one surface of this support layer 2, a gas barrier film comprising a support layer 2 made of a PET film and a gas barrier layer 3 made of an inorganic oxide layer was obtained.

Next, the above-mentioned gas barrier film was attached to the laminate composed of the paper substrate 4, the printed layer 5 and the functional layer 6 by dry lamination. For the dry lamination, first, a dry lamination agent was applied to the surface of the gas barrier layer 3 of the gas barrier film using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Next, the laminate and the support layer 2 were bonded together with the adhesive layer interposed therebetween so that the gas barrier layer 3 faced the paper substrate 4 .

After that, the heat seal layer 1 was attached to the laminate including the support layer 2, the gas barrier layer 3, the paper substrate 4, the print layer 5 and the functional layer 6 by dry lamination. The heat seal layer 1 includes a support layer and an easy peel layer, has a mass per area of 27.6 g/m ² and a thickness of 30 μm, and is corona-treated on the side opposite to the easy peel layer. A film with applied easy peel properties was used. For the dry lamination, first, a dry lamination agent was applied to the surface of the support layer 2 using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Next, the laminated body and the heat seal layer 1 were bonded together so as to face the corona-treated surface of the heat seal layer 1 with the adhesive layer interposed therebetween.

It was then aged at 40°C. As described above, the laminate sheet 10 for a lid shown in FIG. 1 was obtained.

(Example 2)
A laminate sheet 10 for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this example, instead of using a biaxially oriented polyethylene terephthalate (PET) film as the support layer 2, the thickness is 15 μm, the mass per area is 17.4 g/m ² , and one surface A biaxially oriented nylon (Ny) film having both sides subjected to corona treatment was used while being subjected to easy adhesion treatment. The support layer 2 was arranged so that the surface to which the easy-adhesion treatment was applied faced the heat seal layer 1 .

(Example 3)
A laminate sheet 10 for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this example, instead of using a polyethylene terephthalate (PET) film as the support layer 2, the support layer 2 has a thickness of 15 μm and a mass per area of 20.9 g/m ² , A biaxially oriented polybutylene terephthalate (PBT) film with corona treatment on both sides was used.

(Example 4)
A laminate sheet 10 for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this example, instead of using single-sided coated paper as the paper substrate 4, kraft paper having a thickness of 93 μm and a basis weight of 80 g/m ² was used.

(Example 5)
A laminate sheet 10 for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this example, instead of using single-sided coated paper as the paper substrate 4, kraft paper having a thickness of 137.1 μm and a basis weight of 120 g/m ² was used.

(Example 6)
A laminate sheet 10 for a lid shown in FIG. 1 was manufactured by the following method.
First, kraft paper having a basis weight of 50 g/m ² was prepared as the paper base material 4 . On one main surface of the paper base material 4, a coating solution containing polyvinyl alcohol (PVA) as a main component and a layered compound (synthetic mica) as an inorganic oxide is applied to form a gas barrier layer 3. formed. As a result, barrier paper composed of the gas barrier layer 3 and the paper base material 4 of kraft paper and having a mass per area of 65 g/m ² was obtained. A print layer 5 and a functional layer 6 were sequentially formed on the coat layer of this barrier paper in the same manner as in Example 1 using a gravure multicolor printer.

Next, the support layer 2 was attached to the laminate composed of the gas barrier layer 3, the paper substrate 4, the print layer 5, and the functional layer 6 by dry lamination. As the support layer 2, a biaxially oriented polyethylene terephthalate (PET) film having a thickness of 12 μm and a mass per area of 16.8 g/m ² was used. For the dry lamination, first, a dry laminating agent was applied to one surface of the support layer 2 using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Next, the laminate and the support layer 2 were bonded together with the adhesive layer interposed therebetween so that the support layer 2 faced the gas barrier layer 3 .

Thereafter, in the same manner as in Example 1, the support layer 2 is attached to the laminate including the support layer 2, the gas barrier layer 3, the paper substrate 4, the print layer 5, and the functional layer 6 with the adhesive layer interposed therebetween. The heat seal layer 1 was attached so as to face the heat seal layer 1 .

It was then aged at 40°C. As described above, the laminate sheet 10 for a lid shown in FIG. 1 was obtained.

(Comparative example 1)
A laminate sheet for a lid was produced in the same manner as in Example 1, except that the barrier paper used in Example 6 was used as the paper substrate 4 and the gas barrier layer 3, and the support layer was omitted.

(Comparative example 2)
A laminate sheet for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of single-sided coated paper, art paper with a basis weight of 186 g/m ² and a thickness of 183 μm was used as the paper base material 4 .

(Comparative Example 3)
A laminate sheet for a lid was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of using single-sided coated paper as the paper base material 4, thin paper having a basis weight of 25 g/m ² and a thickness of 28 μm is used, and the heat seal layer 1 is , including a support layer and an easy peel layer, has a mass per area of 46.0 g / m ² , a thickness of 50 μm, and an easy peel property in which the surface opposite to the easy peel layer is corona-treated was used.

<2> Evaluation (Measurement of Young's modulus)
The Young's modulus of the lid laminate sheets according to Examples 1 to 6 and Comparative Examples 1 to 3 was measured by the method described above. Specifically, first, three test pieces whose length direction was parallel to the MD and three test pieces whose length direction was parallel to the TD direction were cut out from the lid laminated sheet. Each test piece had a strip shape with a width of 15 mm and a length of 100 mm. A Tensilon universal testing machine was then used to hold one longitudinal end and the other longitudinal end of each specimen in the jaws of the testing machine and move the jaws away from each other. The relative movement speed of the grippers, that is, the pulling speed was 300 mm/min. Moreover, the distance between gauge lines was set to 50 mm. The movement of the gripper was performed until each specimen broke. Next, the value obtained by dividing the tensile force by the initial cross-sectional area between the marked lines was obtained as the tensile stress. Also, the tensile strain was obtained by dividing the increase in the gauge length by the gauge length. Next, the Young's modulus was obtained by dividing the obtained tensile stress by the tensile strain.

(Opening test)
Lids were cut out from the laminated sheets for lids according to Examples 1 to 6 and Comparative Examples 1 to 3. Using these lid bodies, a plurality of food packaging containers 20 shown in FIG. 3 were manufactured. Here, as the container main body 22, a resin sheet formed into a tray shape is used. The container body 22 had a substantially rectangular opening with a long side dimension of 120 mm and a short side dimension of 90 mm, and a height of 30 mm. Heat sealing of the lid 21 to the flange 22a is performed by using a seal bar with a width of 5 mm, which is made along the shape of the flange 22a, and applying a temperature of 160° C. and a pressure of 0.2 MPa for 1.5 seconds. It was done by

Here, as the resin sheet, a three-layer structure sheet containing a pair of polypropylene layers and a layer interposed between them and made of a mixture of polypropylene and 4% by mass of ethylene-vinyl alcohol copolymer is used. bottom.

Next, for each of the lid laminated sheets, the lids 21 were manually peeled off from the corners of the container bodies 22 of arbitrary ten of the manufactured food packaging containers 20 . After that, whether or not paper peeling occurred, and the unsealability were evaluated.
The results of the above measurements and tests are summarized in the table below.

In the column labeled "Openability" in Table 1 above, "A" felt that it was caught when opening, felt that opening required force, and that the lid body stretched when opening. This indicates that none of the tearing occurred. "B" indicates that at least one of the following applies: feeling caught when opening, feeling that opening required force, and lid stretching or tearing when opening. ing.

In the column labeled "paper peeling" in Table 1 above, "A" indicates that cohesive failure occurred in the heat seal layer and no paper peeling occurred. "B" indicates that although the paper was peeled off, a portion of the lid material remained in the container body only at or around the seal portion. In the case of "B", the contents can be taken out from the container body. "C" indicates that the paper was peeled off and the lid material remained on the container body in areas other than the seal portion and its surroundings. Specifically, "C" indicates that a double lid was formed or the lid was torn. Here, the double lid means that a part of the lid mainly including the paper substrate and the heat seal layer covers the whole or most of the opening of the container body due to the cohesive failure of the paper substrate. It is to remain in the container body for a long time. In the case of "C", it takes time and effort to take out the contents from the container body and separate the lid from the container body.

In the column labeled "Paper mark" in Table 2 above, "A" indicates that it is possible to display a paper mark according to the Container Recycling Law, that is, the paper base material included in the laminated sheet for lid When classifying the other layers into a layer made of plastic and other layers, the mass of the paper substrate was greater than the total mass of the layer made of plastic and the total mass of the other layers "B" indicates that the above paper mark cannot be displayed, that is, the layers other than the paper base material included in the laminated sheet for lid are classified into a layer made of plastic and other layers. In this case, the weight of the paper substrate was smaller compared to one of the total weight of the layer consisting of plastic and the total weight of the other layers.

In Table 2 above, "mass" is mass per area. The classification of "Paper", "Plastic" and "Others" in the column labeled "Mass ratio" is in accordance with the "Container and Packaging Recycling Law Explanatory Material", as explained above.

As shown in Table 1 above, when the laminated sheets for lids according to Examples 1 to 6 were used, the opening properties were excellent, and no paper peeling occurred. On the other hand, when the laminated sheets for lids according to Comparative Examples 1 to 3 were used, the unsealability was not excellent.

<3> Evaluation of oxygen barrier properties <Reference Example 1>
A gas barrier consisting of a coating film (coating amount 13 g/m ² , thickness 10 μm) mainly composed of polyvinyl alcohol on the non-glossy main surface of single glossy paper (basis weight 65 g/m ² ) as the paper base material. A laminated sheet in which layers were laminated was prepared.

A printing ink was applied in a coating amount of 1 g/m ² by gravure printing to the main surface of the paper substrate opposite to the main surface on which the gas barrier layer was formed, and a printing layer was laminated. An OP varnish containing nitrocellulose resin as a main component was applied onto the printed layer by a gravure coating method, and a functional layer consisting of an OP varnish layer with a coating amount of 10 g/m ² (dry state) was laminated.

Next, an adhesive composition containing a polyester-based main agent and an aliphatic isocyanate-based curing agent was applied onto the gas barrier layer by a gravure coating method to laminate an adhesive layer with a coating amount of 2 g/m ² (dry state). A laminated sheet for a lid was obtained by laminating a 30 μm-thick, 27 g/m ² non-stretched film mainly composed of linear low-density polyethylene (LLDPE) as a heat seal layer on the adhesive layer. .

<Comparative Example 4>
A laminated sheet for a lid was produced in the same manner as in Reference Example 1, except that the functional layer made of the OP varnish layer was not provided.

(Preparation of specimen for measuring oxygen permeability)
A test piece was obtained by cutting each of the lid laminate sheets of Reference Example 1 and Comparative Example 4 obtained above into a shape of 4 cm×4 cm. Two test pieces were prepared for each of Reference Example 1 and Comparative Example 4. A test piece is sandwiched between two sheets of aluminum film having a hole of 25 mm in diameter in the center, fixed with an adhesive so that the two holes overlap, and laminated, thereby sandwiching the laminated aluminum sheet for the lid. A body (hereinafter also referred to as "aluminum laminate") was obtained. This aluminum laminate was used as a lid of an aluminum cup in an oxygen permeability measurement test to be described later.

The aluminum cup was tested according to JAPAN TAPPI Paper Pulp Test Method No. 7:2000 Paper and Paperboard—Moisture Permeability Test Method A cup conforming to the aluminum moisture permeation cup specified in Method B was prepared. The opening of this cup is covered by placing the aluminum laminate sandwiching the test piece therebetween, and by fixing it with fasteners, a total of 4 test pieces for environmental storage used in the test described below. made.

(Environmental Storage of Specimen and Measurement Test of Oxygen Permeability)
Each of the specimens obtained above was first stored for 12 hours in a refrigerated environment with a temperature of 5° C. and free of humidity. Next, one of the two test specimens in each of Reference Example 1 and Comparative Example 4 was stored in a high-temperature and high-humidity environment with a temperature of 40 ° C. and a relative humidity of 90% for 1 hour. Condensation was forced on the surface of the specimen located on the side. Next, as static adjustment before measuring the oxygen permeability, each specimen was stored for 24 hours in an environment with a temperature of 24° C. and a relative humidity of 55%, and then the oxygen permeability was measured (Condition 2). In addition, for the other test specimens in each of Reference Example 1 and Comparative Example 4, after being stored in the refrigeration environment, the stationary adjustment was performed without performing environmental storage in the high-temperature and high-humidity environment. After that, the oxygen permeability was measured (Condition 1).

The oxygen transmission rate was measured using an oxygen transmission rate measuring device OX-TRAN2/20 manufactured by MOCON under the conditions of a temperature of 30° C. and a relative humidity of 70%. Table 3 shows the results. The lower the oxygen permeability, the better the oxygen barrier properties.

From the measured values shown in Table 3, the lid using the laminated sheet for the lid provided with both the gas barrier layer and the functional layer showed no improvement in barrier performance due to dew condensation even when exposed to a high-temperature and high-humidity environment from a refrigerated environment. It can be seen that the decrease is controlled and the decrease in oxygen barrier performance is remarkably improved. It usually takes about one hour from the time a consumer purchases a packaged product containing chilled food at a store to the time it is stored in the refrigerator at home, and the time it takes for the consumer to take the packaged product out of the refrigerator and cook it. In view of this fact, it can be seen that a lid using a lid laminated sheet provided with both a gas barrier layer and a functional layer is extremely effective as a lid for a packaging container for chilled foods.

<4> Measurement of puncture strength, heat seal strength and breaking strength <Reference Example 2>
A laminated sheet for a lid according to Reference Example 2 was produced by the following method.
First, a single-sided coated paper having a basis weight of 52.3 g/m ² was prepared as a paper substrate. A print layer and a functional layer were sequentially formed on the coat layer of this paper base using a gravure multicolor printer. The printing layer was formed using normal printing ink. The amount of printing ink applied was 1.0 g/m ² . The functional layer 6 was formed using an OP varnish containing nitrocellulose-based resin and polyethylene-based granular wax as main components. The coating amount of the OP varnish was 0.5 g/m ² .

Next, a biaxially stretched polybutylene terephthalate (PBT) film with a thickness of 15 μm was prepared as a support layer. A support layer made of a PBT film was formed by depositing silica as an inorganic oxide on one surface of the support layer, and then coating the deposition layer with a coating solution containing polyvinyl alcohol (PVA) as a main component. and a gas barrier layer comprising an inorganic oxide layer and a PVA layer. The mass per area of this gas barrier film was 22.2 g/m ² .

Next, the gas barrier film was attached to the laminate composed of the paper substrate, the printed layer, and the functional layer by dry lamination. For the dry lamination, first, a dry lamination agent was applied to the gas barrier layer surface of the gas barrier film using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester polyol and an isocyanate curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Next, with the adhesive layer interposed therebetween, the laminate and the gas barrier film were bonded together so that the gas barrier layer faced the paper substrate.

After that, a heat-sealing layer was attached to the laminate including the support layer, the gas barrier layer, the paper substrate, the print layer and the functional layer by dry lamination. The heat-sealing layer includes a support layer and an easy peel layer, has a mass per area of 26.0 g/m ² , and has easy peel properties due to corona treatment on the opposite side of the easy peel layer. used the film. For dry lamination, first, a gravure coater was used to apply a dry lamination agent to the surface of the support layer to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Next, the laminate and the heat-sealing layer were bonded together with the adhesive layer interposed therebetween so as to face the corona-treated surface of the heat-sealing layer.

It was then aged at 40°C. As described above, a laminated sheet for a lid according to Reference Example 2 was obtained.

(Reference example 3)
A laminate sheet for a lid was produced in the same manner as in Reference Example 2, except for the following points. That is, in this example, instead of using a biaxially oriented polybutylene terephthalate (PBT) film as the support layer, a biaxially oriented nylon (Ny) film having a thickness of 15 μm was used, and the inorganic oxide layer was attached to it. A gas barrier film having a mass per area of 18.6 g/m ² was formed by forming a gas barrier layer containing the above PVA layer.

(Reference example 4)
A laminate sheet for a lid was produced by the following method.
First, a single-sided coated paper having a basis weight of 52.3 g/m ² was prepared as a paper substrate. By applying a coating liquid containing polyvinyl alcohol (PVA) as a main component to the surface of the paper substrate on which the coating layer is not formed and a layered compound (synthetic mica) added as an inorganic oxide, A gas barrier layer was formed. As a result, a barrier paper having a mass per area of 67.3 g/m ² consisting of a gas barrier layer and a single-sided coated paper base material was obtained. A printed layer and a functional layer were sequentially formed on the coat layer of this barrier paper in the same manner as in Reference Example 2 using a gravure multicolor printer.

Next, a support layer was attached to the layered product composed of the gas barrier layer, the paper substrate, the print layer and the functional layer by dry lamination. As the support layer, a biaxially oriented polybutylene terephthalate (PBT) film with a thickness of 15 μm and a weight per area of 20.9 g/m ² with corona treatment on both sides was used. For the dry lamination, first, a dry laminating agent was applied to one surface of the support layer 2 using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-liquid reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used. The coating amount of the dry laminating agent was 3.0 g/m ² . Then, with the adhesive layer interposed therebetween, the laminate and the support layer were bonded together so that the support layer faced the gas barrier layer.

Thereafter, in the same manner as in Reference Example 2, a laminate containing a support layer, a gas barrier layer, a paper substrate, a printing layer, and a functional layer is placed so that the support layer faces the heat seal layer with the adhesive layer interposed therebetween. The heat-seal layers were laminated together, as shown.

It was then aged at 40°C. As described above, a laminated sheet for a lid according to Reference Example 4 was obtained.

(Reference example 5)
A laminate sheet for a lid was produced in the same manner as in Reference Example 4, except for the following points. That is, in this example, instead of using a biaxially oriented polybutylene terephthalate (PBT) film as the support layer, it has a thickness of 15 μm, a mass per area of 17.4 g/m ² , and one surface A biaxially oriented nylon (Ny) film having both sides subjected to corona treatment was used while being subjected to easy adhesion treatment. The support layer was arranged so that the surface to which the easy-adhesion treatment was applied faced the heat seal layer 1 .

(Comparative Example 5)
A laminate sheet for a lid was produced in the same manner as in Reference Example 2, except for the following points. That is, in this comparative example, instead of using a biaxially oriented polybutylene terephthalate (PBT) film as the support layer, a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film was used, and the inorganic oxidation was applied thereto. A gas barrier film having a mass per area of 17.6 g/m ² was formed by forming a gas barrier layer containing the material layer and the PVA layer.

(Comparative Example 6)
A laminate sheet for a lid was produced in the same manner as in Reference Example 2, except that the support layer and the gas barrier layer were omitted.

(Measurement of breaking strength)
The breaking strength of the support layers used in Reference Examples 2 to 5 and Comparative Example 5 was measured by the method described above.

Here, from each support layer, three test pieces with the length direction parallel to the MD and three test pieces with the length direction parallel to the TD were cut. Each test piece had a strip shape with a width of 15 mm and a length of 100 mm.

The distance between gauge lines was 50 mm, and the test speed was 1000 mm/min. The breaking strength was measured using a Tensilon universal testing machine.

The breaking strength in the MD was obtained by arithmetically averaging the measurements obtained using specimens with the length direction parallel to the MD. Moreover, the breaking strength in TD was obtained by arithmetically averaging the measured values obtained using a test piece whose length direction was parallel to TD.

(Measurement of heat seal strength)
The heat seal (HS) strength to the resin sheet described above was measured for the lid laminated sheets according to Reference Examples 2 to 5 and Comparative Examples 5 and 6 by the method described above.

Each lid laminate sheet and resin sheet were heat-sealed using a TP-701-B heat seal tester manufactured by Tester Sangyo Co., Ltd. The heat seal tester used here had a seal bar width of 5 mm. The length direction of the seal bar was perpendicular to MD. Heat sealing was performed by applying a temperature of 190° C. and a pressure of 0.2 MPa to the laminate of the lid laminated sheet and the resin sheet for 2 seconds at each heat sealing position. From each laminate partially heat-sealed in this way, a strip having a width of 15 mm, the length direction parallel to the MD, one end not heat-sealed and the other end 30 mm Three heat-sealed specimens were cut over a length of ∼50 mm.

Separately from this, each lid laminated sheet and the resin sheet were heat-sealed by the same method as described above, except that the length direction of the seal bar was perpendicular to the TD. From each laminate partially heat-sealed in this way, a strip having a width of 15 mm, the length direction parallel to the TD, one end not heat-sealed and the other end 30 mm Three heat-sealed specimens were cut over a length of ∼50 mm.

Next, the heat seal strength of each test piece was measured by the method described above. Specifically, a Tensilon universal tester was used to measure the heat seal strength. The non-heat-sealed lid laminated sheet portion and resin sheet portion of each test piece were gripped by grippers of the tester, and the grippers were moved away from each other. The relative movement speed of these grippers, that is, the peeling speed, was 1000 mm/min. The maximum tensile load applied to each specimen until it broke was recorded.

The heat seal strength in the MD was obtained by arithmetically averaging the maximum values of the tensile loads obtained for three test pieces whose longitudinal direction was parallel to the MD for each lid laminated sheet. In addition, the heat seal strength in the TD was obtained by arithmetically averaging the maximum values of the tensile loads obtained from three test pieces whose length direction was parallel to the TD for each lid laminated sheet.

(Measurement of piercing strength)
The puncture strength of the laminated sheets for lids according to Reference Examples 2 to 5 and Comparative Example 5 was measured by the method described above. Here, the piercing strength when a needle is pierced into the laminated lid sheet from the functional layer side and the piercing strength when the needle is pierced into the laminated lid sheet from the heat seal layer side were determined. . Each puncture strength was obtained by arithmetically averaging the values obtained from three measurements.

(Cup seal test)
Lids were cut out from the laminated sheets for lids according to Reference Examples 2 to 5 and Comparative Examples 5 and 6. Using these lids, the food packaging container 20 shown in FIG. 3 was manufactured. Here, as the container main body 22, a container formed by molding the resin sheet described above into a tray shape was used. The container body 22 had a substantially rectangular opening with a long side dimension of 120 mm and a short side dimension of 90 mm, and a height of 30 mm. Heat sealing of the lid 21 to the flange 22a is performed by using a seal bar with a width of 5 mm, which is made along the shape of the flange 22a, and applying a temperature of 160° C. and a pressure of 0.2 MPa for 1.5 seconds. It was done by

Next, for each food packaging container 20, the lid 21 was peeled off from the corner of the container body 22 by hand. After that, it was confirmed whether or not the paper peeled off.
The results of the above measurements and tests are summarized in Table 4 below.

In Table 4 above, "mass" is mass per area. The classification of "Paper", "Plastic" and "Others" in the column labeled "Mass ratio" is in accordance with the "Container and Packaging Recycling Law Explanatory Material", as explained above. The column labeled "difference" describes the value obtained by subtracting the heat seal strength between the lid laminated sheet and the resin sheet from the breaking strength of the support layer.

In the column labeled "Paper Peeling" in Table 4 above, "A" indicates that cohesive failure occurred in the heat seal layer and no paper peeling occurred. "B" indicates that although the paper was peeled off, a portion of the lid material remained in the container body only at or around the seal portion. In the case of "B", the contents can be taken out from the container body. "C" indicates that the paper was peeled off and the lid material remained on the container body in areas other than the seal portion and its surroundings. Specifically, "C" indicates that a double lid was formed or the lid was torn. Here, the double lid means that a part of the lid mainly including the paper substrate and the heat seal layer covers the whole or most of the opening of the container body due to the cohesive failure of the paper substrate. It is to remain in the container body for a long time. In the case of "C", it takes time and effort to take out the contents from the container body and separate the lid from the container body.

In the column labeled "Puncture strength" in Table 4 above, "upper surface" represents the piercing strength when a needle is pierced into the lid laminated sheet from the functional layer side, and "lower surface" represents the needle. shows the piercing strength when the laminated sheet for lid is pierced from the heat seal layer side. In the column labeled "upper surface" or "lower surface", "A" has a piercing strength that is at least twice as high as the piercing strength obtained for the lid laminated sheet according to Comparative Example 6. indicates that "B" indicates that the piercing strength was more than 1.5 times and less than 2 times the piercing strength obtained for the laminated sheet for a lid according to Comparative Example 6. “C” indicates that the laminate sheet for a lid according to Comparative Example 6 had a puncture strength 1.5 times or less than the puncture strength obtained for the lid laminate sheet.

As shown in Table 4 above, the laminated sheets for lids according to Reference Examples 2 to 5 were pierced with a needle either from the functional layer side or from the heat seal layer side. Also, it had a high piercing strength. In contrast, the laminated sheet for a lid according to Comparative Example 6 had a low piercing strength when the needle was pierced into the laminated sheet for a lid from the functional layer side and the needle was pierced from the heat seal layer side. had a The laminated sheet for a lid according to Comparative Example 5 had a high piercing strength when a needle was pierced into the laminated sheet for a lid from the heat-seal layer side, but the needle did not function in the laminated sheet for a lid. The piercing strength when pierced from the layer side was low.

Further, as shown in Table 4 above, when the laminated sheets for lids according to Reference Examples 2 to 5 and Comparative Example 5 were used, no paper peeling occurred. On the other hand, when the laminated sheet for a lid according to Comparative Example 6 was used, paper peeling occurred.

It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified in the implementation stage without departing from the gist of the present invention. Further, each embodiment may be implemented in combination as appropriate, in which case the combined effect can be obtained. Furthermore, various inventions are included in the above embodiments, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, if the problem can be solved and effects can be obtained, the configuration with the constituent elements deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1... Heat-sealing layer 2... Supporting layer 3... Gas barrier layer 4... Paper base material 5... Printing layer 6... Functional layer having water resistance 10, 11... Laminated sheet for lid 20... For food Packaging container 21 Lid body 22 Container body 22a Flange.

Claims (20)

A lid laminated sheet used for the lid of a food packaging container comprising a container body provided with an opening and a lid covering the opening, the laminated sheet comprising a functional layer having water resistance, a printed layer, comprising a paper substrate, a support layer, and a heat seal layer in that order;
The mass of the paper base material is greater than the mass of any other layer included in the laminated lid sheet,
Young's modulus in MD and TD of the laminated sheet for a lid are both in the range of 1.2 to 2.9 GPa,
The thickness of the lid laminate sheet is in the range of 80 to 205 μm. 2. The laminated sheet for a lid according to claim 1, wherein said Young's modulus is in the range of 1.2 to 2.6 GPa. 3. The lid laminate sheet according to claim 1, wherein the thickness of the lid laminate sheet is in the range of 90 to 150 [mu]m. The laminate sheet for a lid according to any one of claims 1 to 3, wherein the support layer has a breaking strength greater than a heat seal strength between the lid and the container body. The laminated sheet for a lid according to any one of claims 1 to 4, wherein the support layer contains at least one of polybutylene terephthalate and polyamide. When the layers other than the paper base material included in the lid laminated sheet are classified into a layer made of plastic and other layers, the mass of the paper base material is the sum of the layers made of plastic. The laminate sheet for a lid according to any one of claims 1 to 5, which is larger than the total mass of the mass and the other layers. The laminate sheet for a lid according to any one of claims 1 to 6, further comprising a gas barrier layer having gas barrier properties between the paper substrate and the heat seal layer. The laminated sheet for a lid according to claim 7, wherein the gas barrier layer comprises at least one of an inorganic oxide layer and a resin-containing layer. The laminate sheet for a lid according to claim 7 or 8, comprising the gas barrier layer between the paper substrate and the support layer. The laminate sheet for a lid according to any one of claims 7 to 9, wherein the paper base material is a barrier paper having the gas barrier layer on one surface. The laminate for a lid according to any one of claims 1 to 10, wherein the paper substrate is a coated paper having a coat layer on one side, and the printed layer is provided on the coat layer. sheet. The laminate sheet for a lid according to any one of claims 1 to 11, wherein the paper base material has a basis weight in the range of 40 to 160 g/ ^m2 . The laminated sheet for a lid according to any one of claims 1 to 12, wherein the heat seal layer is a sealant having easy peel properties. The laminated sheet for a lid according to any one of claims 1 to 13, wherein the functional layer has a mass per area of 0.2 g/m2 ^or more. A lid comprising the laminated sheet for a lid according to any one of claims 1 to 14. A food packaging container comprising: a container body provided with an opening; and the lid according to claim 15 covering the opening, wherein the support layer covers the paper substrate and the inside of the food packaging container. A food packaging container that is placed between the space. 17. The food packaging container according to claim 16, wherein said container body has a flange around said opening, and said lid is heat-sealed to said flange via said heat-seal layer. 18. The food packaging container according to claim 16 or 17, wherein said internal space of said food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas and carbon dioxide gas. The food packaging container according to any one of claims 16 to 18, wherein the food packaging container is a chilled food packaging container or a frozen food packaging container. A packaged food comprising the food packaging container according to any one of claims 16 to 19 and a food contained in the food packaging container.

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