JP2023074842A - packaged food - Google Patents

Abstract

To provide packaged food exhibiting an excellent opening property together with fall resistance, that comprises a lid body exhibiting excellent gas barrier such as water vapor or the like, the body comprising a paper substrate.SOLUTION: According to a lid body 10 comprising a container body 12 whose opening is provided, that is formed with a flange, a functional layer 6 exhibiting a water-resisting property, a printing layer 5, a paper substrate 4, a support layer 2, and a heat seal layer 1 in this order; packaged food 40 according to an embodiment of the present invention comprises: a food packaging container 20 comprising a lid body heat-sealed by the flange via the heat seal layer, that covers the opening; and food 30 stored in the food packaging container. Mass of the paper substrate is larger than mass of any other layer included in the lid body. Fracture strength of the support layer is larger than peeling strength between the lid body and the container body. A heat seal portion between the lid body and the container body has a width of 2 to 12 mm. The peeling strength between the lid body and the container body is 4 to 32 N/15 mm.SELECTED DRAWING: Figure 1

Description

The present invention relates to packaged foods.

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.

As an example of a paper packaging container, Patent Literature 1 discloses a heat-resistant paper container composed of a body member and a bottom plate member.

Further, Patent Document 2 describes an easy-open container in which a lid having a heat-seal layer on the inner surface is heat-sealed so that the heat-seal layer faces the opening peripheral portion of the container body. The use of paper is disclosed.

JP 2016-78868 A JP 2006-151475 A

An object of the present invention is to provide a packaged food that includes a paper substrate, has a lid that has excellent gas barrier properties against water vapor and the like, and has excellent opening properties and drop resistance.

According to one aspect of the present invention, a container body having a flange and an opening, a water-resistant functional layer, a printing layer, a paper substrate, a support layer, and a heat-sealing layer are combined into this. a lid comprising in sequence, wherein the mass of the paper substrate is greater than the mass of any other layer contained in the lid, covering the opening and heat-sealing the flange through the heat seal layer; a food packaging container comprising a sealed lid; The width of the heat-sealed portion between the lid and the container body is in the range of 2 to 12 mm, and the peel strength between the lid and the container body is in the range of 4 to 32 N/15 mm. A packaged food product is provided.

According to the present invention, there is provided a packaged food that includes a paper substrate, has a lid that has excellent gas barrier properties against water vapor and the like, and has excellent opening properties and drop resistance.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows schematically an example of the packaged food which concerns on one Embodiment of this invention. FIG. 4 is a partial cross-sectional view schematically showing an example of a lid; FIG. 2 is a top view schematically showing the packaged food shown in FIG. 1; The fragmentary sectional view which shows roughly the lid|cover which concerns on a modification.

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

FIG. 1 is a cross-sectional view schematically showing an example of a packaged food according to one embodiment of the present invention.
The packaged food 40 is obtained by housing the food 30 in the food packaging container 20 . The food 30 to be accommodated is not particularly limited, but is preferably chilled food or frozen food. 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.

The food packaging container 20 includes a container body 12 provided with an opening, and a lid body 10 covering the opening.

The container main body 12 is, for example, in the shape of a cylinder with a bottom. The container body 12 here comprises a bottom, a body (or side wall) and a flange 121 . Flange 121 flares outward at the upper opening of the barrel. Here, the flange 121 has ribs 1211 . When the flange 121 has ribs 1211, the strength of the flange 121 is increased, so that the lid and the container body are easily heat-sealed. Note that the rib 1211 may be omitted.

The container body 12 contains, for example, an olefin resin such as polypropylene. The container body 12 may further contain a component such as an ethylene-vinyl alcohol copolymer in order to enhance its gas barrier properties. Further, the container body 12 may further contain additives, for example, additives for the purpose of improving workability, designability, and chemical durability.

The container body 12 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 12 . When the contents contain a liquid material, the container body 12 includes a paper substrate 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 12 containing the paper substrate, for example, paper leaves, paper dust, pulp, or used paper can be used. For molding into the container body 12, 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 12, 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.

FIG. 2 is a partial cross-sectional view schematically showing an example of the lid 10. As shown in FIG. The lid 10 is heat-sealed to the flange 121 via the heat-seal layer 1 described later after the contents are contained in the container body 12 . In this heat sealing, the sealing temperature, sealing pressure, and sealing time can be appropriately set.

The lid body 10 includes 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 in this order. I'm in. As described above, the lid body 10 includes the gas barrier layer 3 between the paper base material 4 and the support layer 2 . may be included between 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 lid 10 is described below.

(Paper substrate)
The lid 10 includes a paper base material 4 . The mass of the paper substrate 4 is greater than the mass of any other layers included in the lid 10 . The ratio of the mass of the paper substrate 4 to the mass of the lid 10 is preferably 40% or more, more preferably 45% or more, even more preferably 50% or more, and more than 50%. It is even more preferable to have 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 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 the other layers. is preferably larger compared to the total mass of the In this case, in Japan, the lid 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. 2, the support layer 2 and the heat seal layer 1 attached thereto are "layers made of plastic". In the example shown in FIG. 2, 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. 2, 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 base material 4, that is, the mass per area is preferably in the range of 20 to 500 g/m ² , more preferably in the range of 40 to 100 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.

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 body 10 also increases. However, if 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 body 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 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. Specifically, the support layer 2 is preferably 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 4 to 50 μm, more preferably in the range of 5 to 40 μm, even more preferably in the range of 12 to 25 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 lid 10 .

The breaking strength of the support layer 2 is greater than the peel strength between the lid 10 and the container body 12 . Here, the fact that the breaking strength of the support layer 2 is greater than the peel strength between the lid 10 and the container body 12 means that the breaking strength of the support layer 2 in MD (Machine Direction) is greater than that between the lid 10 and the container body 12 . and the breaking strength of the support layer 2 in TD (Transverse Direction) is greater than the peel strength between the lid 10 and the container body 12 .

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 peel strength between the lid 10 and the container body 12 will be described later.

When the breaking strength of the support layer 2 is greater than the peel strength between the lid 10 and the container body 12 , paper peeling is less likely to occur when the lid 10 is peeled from the container body 12 . For example, when the breaking strength of the support layer 2 is greater than 30 N/15 mm, the occurrence of paper peeling can be suppressed up to a peel strength of about 30 N/15 mm. Here, "paper peeling" means that when the lid 10 is peeled off from the container body 12, cohesive failure of the paper substrate 4 occurs, and a part of the lid 10 remains in the container body 12. . If paper peeling occurs, it may become impossible or difficult to take out the contents accommodated in the container body 12 .

The peel strength is adjusted according to the use and purpose of the packaging container. For example, the peel strength may be reduced in order to impart easy-open properties. 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 body 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 substrate 4 of the lid 10 and the support layer 2 by using a gas barrier film composed of the support layer 2 having the gas barrier layer 3 on one side. 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 may be interposed between the paper base 4 of the lid 10 and the support layer 2 by using barrier paper made of the paper base 4 having the gas barrier layer 3 on one side. 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 to put the lid 10 into practical use 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 having water resistance (water-resistant layer) 6 suppresses the penetration of liquids outside the container, such as moisture and oil due to dew condensation, into the lid in packaged foods, and the liquids are prevented from penetrating into the printed layer 5 and the paper. It is a layer that suppresses reaching the layers of the 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 control the water absorbency of the partially laminated sheet, which is the portion of the lid 10 from the functional layer 6 to the paper substrate 4 . The functional layer 6 preferably has water resistance such that the water absorbency of the lid according to 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 10 shown in FIG. 2, the paint for forming the functional layer 6 is preferably applied in an amount of 0.2 g/m ² or more, and is 2.0 g/m ^{2 .} It is more preferable to apply the coating so as to achieve the above. 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-sealing layer 1 may be any material as long as it enables the lid 10 to be heat-sealed to the container body 12 of the food packaging container 20, thereby sealing the container. The ease of peeling the lid 10 from the container body 12 can be adjusted according to, for example, the peeling mechanism of the heat seal layer 1, such as interfacial peeling or cohesive failure, or the peel 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 weight per area of the heat seal layer 1 is preferably in the range of 2 to 50 g/ ^m2 , more preferably in the range of 10 to 50 g/ ^m2 , and in the range of 20 to 40 g/ ^m2 . It is more preferable to be in If the mass per unit area of the heat-seal layer 1 is too small, the heat-sealed portion will be damaged by impact such as dropping, and the contents will easily scatter. If the mass per unit area of the heat-seal layer 1 is too large, the opening property is not excellent, and the contents may scatter when an attempt is made to open the package by forcibly applying force.

When a sealant layer having an easy peel function is used as the heat seal layer 1, the mass per area of the heat seal layer 1 is preferably in the range of 10 to 50 g/m ² , more preferably 20 to 40 g/m ² . is more preferably within the range of

When heat seal varnish is used as the heat seal layer 1, the weight per unit area of the heat seal varnish is preferably in the range of 1 to 15 g/m ² , more preferably in the range of 2 to 10 g/m ² . is more preferred.

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.

(adhesion layer)
Lid 10 may further include one or more adhesive layers.
For example, the lid 10 may include an adhesive layer between the heat seal layer 1 and the support layer 2 to adhere them. Alternatively, the lid 10 may include an adhesive layer between the support layer 2 and the gas barrier layer 3 for bonding them. Alternatively, the lid 10 may include an adhesive layer between the gas barrier layer 3 and the paper substrate 4 for bonding them. Alternatively, the lid 10 may include two or more adhesive layers as 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 lid 10 preferably has a mass per area of 50 to 160 g/m ² , more preferably 60 to 140 g/m ² , and more preferably 90 to 130 g/m ² . It is more preferable to be within the range. If this value is made smaller, the strength of the lid body 10 is lowered. If this value is too large, the lid body 10 tends to be hard and unsealable. Also, increasing this value increases the cost and carbon dioxide emissions associated with manufacturing and exhaust.

In the production of the packaged food 40 described above, before the lid 10 is heat-sealed to the container body 12, for example, after the contents are accommodated in the container body 12, the lid 10 is heat-sealed to the container body 12. Prior to sealing, the gas within the container body 12 may be replaced by known methods. For example, the container body 12 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.

In the packaged food 40 described above, the peel strength between the lid 10 and the container body 12 is smaller than the breaking strength of the support layer 2 included in the lid 10, as described above. This peel strength is in the range of 4 to 32 N/15 mm, preferably in the range of 5 to 30 N/15 mm. If the peel strength is too low, for example, less than 4 N/15 mm, the heat-sealed portion will be damaged by impact such as dropping, and the contents will easily scatter. If the peel strength is too high, for example, greater than 32 N/15 mm, the opening property is not excellent, and the contents may scatter when an attempt is made to open the package by applying excessive force.

The difference between the breaking strength of the support layer 2 and the peel strength between the lid 10 and the container body 12 is preferably within the range of 5 to 60 N/15 mm, and within the range of 10 to 40 N/15 mm. is more preferable.

Here, the peel strength is a method for measuring heat seal strength specified in JIS Z0238: 1998 "Test method for heat seal flexible packaging bags and semi-rigid containers" except that the test piece described below was used. is a value obtained by the same method as A test piece was cut out from a portion of the food packaging container 20 where the lid 10 and the flange 121 overlapped. A test piece is cut out so as to include a portion where the lid 10 and the flange 121 are heat-sealed. The test piece has a strip shape with a width of 15 mm. The length direction of the test piece is parallel to the width direction of the flange 121 .

FIG. 3 is a top view schematically showing the packaged food 40 shown in FIG. 1. FIG.
A dashed line B1 shown in FIG. 3 indicates the contour of the opening of the container body 12 . A region R1 is a region surrounded by two dashed-dotted lines. A region R1 indicates a heat-sealed portion between the lid 10 and the flange 121. As shown in FIG. As shown in FIG. 3, the heat-sealed portion has a shape that follows the shape of the flange 121 . As shown in FIG. 3, the lid 10 may have a grip portion.

In this packaged food 40, the shortest distance between the inner contour and the outer contour of the region R1 shown in FIG. . More preferably, the width of this heat-sealed portion is in the range of 4 to 10 mm. If the width of the heat-sealed portion is too narrow, for example, if the width is less than 2 mm, the heat-sealed portion may be damaged by impact such as dropping, and the contents may scatter. If the width of the heat-sealed portion is too wide, for example, if the width is greater than 12 mm, the unsealability is poor. In addition, if the width is too wide, the width of the flange is also widened, and the flange may be bent or the like. In addition, when the width of the flange is wide, there is a possibility that the appearance may deteriorate, and the dead space tends to increase when the packaged food is displayed on the shelf.

Moreover, when the lid 10 described above includes the gas barrier layer 3, such a lid 10 has high gas barrier properties. Furthermore, such a lid body 10 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.

Some gas barrier layers do not include metal layers. 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 body 10 described above includes a functional layer 6 having water resistance. Therefore, in a packaged food using this lid 10 as a lid material, moisture generated on the outer surface of the lid due to dew condensation is less likely to reach the gas barrier layer 3 . Therefore, in the packaged food using this lid 10, the gas barrier layer 3 is unlikely to be damaged due to dew condensation on the outer surface of the lid, and the oxygen barrier property is less likely to deteriorate.

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 peeling 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 are possible for the lid. As noted above, the lid may include a gas barrier layer between the paper substrate and the heat seal layer, and as described below with reference to FIG. 4, between the support layer and the heat seal layer. A gas barrier layer may be included in between. Note that the items described with reference to FIG. 2 can be applied singly or in combination to the cover according to the modified example described here.

FIG. 4 is a partial cross-sectional view schematically showing a lid according to one modification.
The lid 11 shown in FIG. 4 is the same as the lid 10 described with reference to FIG. 2 except that the gas barrier layer 3 is interposed between the support layer 2 and the heat seal layer 1 .

That is, the lid body 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 this order. contains in The lids 11 and 10 have the same effects as described above.

The following describes tests conducted in relation to the present invention.
<1> Manufacture of packaged food (Example 1)
First, the lid body 10 shown in FIG. 2 was manufactured by the following method.
First, as the paper base material 4, a single-sided coated paper having a basis weight of 65 g/m ² was prepared. A coating liquid containing polyvinyl alcohol (PVA) as a main component and layered compound (synthetic mica) as an inorganic oxide is applied to the surface of the paper substrate 4 on which no coat layer is formed by gravure printing. A gas barrier layer 3 was formed. Barrier paper A comprising gas barrier layer 3 and paper substrate 4 of single-sided coated paper was thus obtained. The mass per area of the gas barrier layer 3 was 13 g/m ² . A print layer 5 and a functional layer 6 were sequentially formed on the coat layer of the barrier paper A 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 .

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 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. The heat seal layer 1 can be peeled off from the container body by cohesive failure of the easy peel layer.

It was then aged at 40°C. As described above, the lid body 10 shown in FIG. 2 was obtained.

Next, the obtained lid body was used to manufacture the packaged food 40 shown in FIG. Here, as the container body 12, a resin sheet formed into a tray shape was used, and the container body 12 was filled with 200 ml of tap water. The container body 12 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 10 to the flange 121 is performed by using a seal bar with a width of 5 mm, which is made along the shape of the flange 121, 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.

The packaged food 40 according to Example 1 was produced as described above.

(Example 2)
A packaged food 40 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 with a thickness of 12 μm and a mass per area of 16.8 g/m ² as the support layer 2, the thickness is 25 μm. A biaxially oriented polyethylene terephthalate (PET) film with a weight per area of 35 g/m ² was used.

(Example 3)
First, the lid body 10 shown in FIG. 2 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 base 4 in the same manner as in Example 1 using a gravure multicolor printer.

Next, a polyethylene terephthalate (PET) film having a thickness of 12 μm was prepared as the support layer 2 . By forming an inorganic oxide film made of aluminum oxide on one surface of the support layer 2, a gas barrier film having a mass per area of 16.8 g/m ² was obtained.

Next, the above 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 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 3 faced the paper substrate 4 .

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 lid body 10 shown in FIG. 2 was obtained.

Next, a packaged food 40 shown in FIG. 1 was manufactured in the same manner as in Example 1, except that the obtained lid body was used.

(Example 4)
A packaged food 40 was produced in the same manner as in Example 1, except for the following points. That is, in this example, instead of laminating the heat seal layer 1 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 lamination described above is performed. A heat-sealing varnish was applied to the body by gravure printing so that the mass per area was 3 g/m ² . A heat seal layer 1 was thus formed. An olefin-based water-based emulsion type was used as the heat seal varnish. Also, the width of the heat-sealed portion was changed from 5 mm to 2 mm.

(Example 5)
A packaged food 40 was produced in the same manner as in Example 1, except for the following points. That is, in this example, barrier paper B described below was used instead of barrier paper A described above. The barrier paper B is provided with a single-sided coated paper having a basis weight of 84 g/m ² as the paper base material 4, and the surface of the paper base material 4 on which no coat layer is formed is coated with polyvinyl alcohol (PVA) as a main component. and a layered compound (synthetic mica) as an inorganic oxide is formed by gravure printing. Also, instead of using a biaxially oriented polyethylene terephthalate (PET) film with a thickness of 12 μm and a mass per area of 16.8 g/m ² as the support layer 2, the thickness is 25 μm and the area A biaxially oriented polyethylene terephthalate (PET) film with a per mass of 35 g/m ² was used. The heat seal layer 1 includes a support layer and an easy peel layer, has a mass per area of 46.0 g/m ² and a thickness of 50 μm, and has a corona on the side opposite to the easy peel layer. A treated film having easy peel properties was used. Also, the width of the heat-sealed portion was changed from 5 mm to 12 mm.

(Comparative example 1)
A packaged food was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of laminating the heat seal layer 1 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 above-described The heat seal varnish described above was applied to the laminate by gravure printing so that the mass per area was 1 g/m ² . A heat seal layer 1 was thus formed. Also, the width of the heat-sealed portion was changed from 5 μm to 1 μm.

(Comparative example 2)
A packaged food was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of using the barrier paper A, the barrier paper B described above was used. Also, instead of using a biaxially oriented polyethylene terephthalate (PET) film with a thickness of 12 μm and a mass per area of 16.8 g/m ² as the support layer 2, the thickness is 25 μm and the area A biaxially oriented polyethylene terephthalate (PET) film with a per mass of 35 g/m ² was used. The heat seal layer 1 includes a support layer and an easy peel layer, has a mass per area of 46.0 g/m ² and a thickness of 50 μm, and has a corona on the side opposite to the easy peel layer. A treated film having easy peel properties was used. Also, the width of the heat-sealed portion was changed from 5 mm to 14 mm.

(Comparative Example 3)
A packaged food was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of using the barrier paper A, the barrier paper B described above was used. Also, instead of using a biaxially oriented polyethylene terephthalate (PET) film with a thickness of 12 μm and a mass per area of 16.8 g/m ² as the support layer 2, the thickness is 25 μm and the area A biaxially oriented polyethylene terephthalate (PET) film with a per mass of 35 g/m ² was used. As the heat seal layer 1, a sealant made of polypropylene having a thickness of 50 μm and a mass per area of 46 g/m ² was used instead of using the film having the easy peel property described above. Also, the width of the heat-sealed portion was changed from 5 mm to 12 mm.

(Comparative Example 4)
A packaged food was produced in the same manner as in Example 1, except for the following points. That is, in this comparative example, instead of using a biaxially oriented polyethylene terephthalate (PET) film having a thickness of 12 μm and a mass per area of 16.8 g/m ² as the support layer 2, the thickness was A biaxially oriented polyethylene terephthalate (PET) film with a thickness of 4 μm and an area weight of 5.6 g/m ² was used.

(Comparative Example 5)
A packaged food was produced in the same manner as in Example 1, except that the support layer 2 was omitted.

<2> Evaluation (Measurement of peel strength)
The peel strength of the packaged foods according to Examples 1-5 and Comparative Examples 1-5 was measured by the method described above. Specifically, first, from the portion where the lid 10 and the flange 121 overlap on the flange on the long side of the packaged food 40, to include the portion where the lid 10 and the flange 121 are heat-sealed, Three test pieces were cut. The test piece had a strip shape with a width of 15 mm, and its length direction was parallel to the width direction of the flange 121 . Next, three test pieces were cut out from the short side flange of the packaged food 40 by the same method as described above.

Next, using a Tensilon universal tester, the non-heat-sealed flanges and lids of each specimen were gripped by the tester grips and the grips 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 grip interval was 50 mm.

The peel strength on the long side was obtained by arithmetically averaging the maximum values of the tensile loads obtained from the three test pieces cut out from the flange on the long side of each lid. Further, the peel strength on the short side was obtained by arithmetically averaging the maximum values of the tensile loads obtained from the three test pieces cut out from the flange on the short side of each lid.

(Measurement of breaking strength)
The breaking strength of the support layers used in Examples 1-5 and Comparative Examples 1-4 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 of the support layer used in Example 3 was almost the same as the breaking strength of the barrier film used in Example 3.

(Opening test)
In each of the packaged foods 40 according to Examples 1 to 5 and Comparative Examples 1 to 5, the lids 10 were manually peeled off from the corners of the container bodies 12 for ten arbitrary pieces. After that, whether or not paper peeling occurred, and the unsealability were evaluated.

(Evaluation of drop resistance)
For each of the packaged foods according to Examples 1 to 5 and Comparative Examples 1 to 5, 10 arbitrary pieces were evaluated for drop resistance by the following method.
Specifically, each packaged food was dropped from a height of 1 m in an inverted state to evaluate whether or not the packaged food was torn.
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 "Material" column of the "Heat Seal Layer" in Tables 1 and 2 above, "EP" indicates an easy-peel sealant, "Varnish" indicates a heat seal varnish, and "PP" consists of polypropylene. Indicates sealant.

In the "drop resistance" column of Table 2 above, "A" indicates that none of the packaged foods were damaged in the drop resistance evaluation. A "B" indicates that at least one package failed in the drop resistance rating.

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 Tables 1 and 2 above, the packaged foods according to Examples 1 to 5 and Comparative Example 1 were excellent in ease of opening, and paper peeling did not occur. However, the packaged food according to Comparative Example 1 was not excellent in drop resistance.

Moreover, the packaged foods according to Comparative Examples 2 to 5 were not excellent in opening properties. Furthermore, in the packaged foods according to Comparative Examples 4 and 5, paper peeling occurred.

<3> Evaluation of oxygen barrier property <Reference example>
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 6>
A laminate sheet for a lid was produced in the same manner as in Reference Example 1, except that the OP varnish layer was not provided as a functional layer.

(Preparation of specimen for measuring oxygen permeability)
A test piece was obtained by cutting each of the cover laminated sheets of Reference Example and Comparative Example 6 obtained above into a shape of 4 cm×4 cm. Two test pieces were prepared for each of Reference Example and Comparative Example 6. 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. Then, one of the two test specimens in each of Reference Example 1 and Comparative Example 6 was stored in a high temperature and high humidity environment at 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 and Comparative Example 6, after being stored in the refrigeration environment, the stationary adjustment was performed without carrying out 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.

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... Lid body 12... Container main body 121... Flange 1211 Rib 20 Food packaging container 30 Food 40 Packaged food B1 Broken line R1 Region

Claims (16)

a container body formed with a flange and provided with an opening;
A cover comprising a water-resistant functional layer, a printing layer, a paper base, a support layer, and a heat seal layer in this order, wherein the weight of the paper base is included in the cover. a lid that covers the opening and is heat-sealed to the flange via the heat-seal layer, the lid having a mass larger than that of any other layer; and
and a food contained in the food packaging container,
The breaking strength of the support layer is greater than the peel strength between the lid and the container body,
The width of the heat-sealed portion between the lid and the container body is in the range of 2 to 12 mm,
A packaged food, wherein the peel strength between the lid body and the container body is in the range of 4 to 32 N/15 mm. When the layers other than the paper base contained in the lid are classified into a layer made of plastic and other layers, the mass of the paper base is the total mass of the layers made of plastic and the 2. Packaged food according to claim 1, which is greater than the total mass of the other layers. 3. The packaged food according to claim 1, further comprising a gas barrier layer having gas barrier properties between said paper substrate and said heat seal layer. 4. The packaged food according to claim 3, wherein the gas barrier layer comprises at least one of an inorganic oxide layer and a resin-containing layer. 5. The packaged food according to claim 3 or 4, comprising the gas barrier layer between the paper substrate and the support layer. 6. The packaged food according to any one of claims 3 to 5, wherein the paper substrate is a barrier paper having the gas barrier layer on one side. The packaged food according to any one of claims 1 to 6, wherein the paper substrate is coated paper having a coat layer on one side, and the printed layer is provided on the coat layer. The packaged food according to any one of claims 1 to 7, wherein the paper substrate has a basis weight in the range of 40 to 100 g/ ^m2 . 9. The packaged food according to any one of claims 1 to 8, wherein the heat seal layer is a sealant having easy peel properties. 9. The packaged food according to any one of claims 1 to 8, wherein the heat seal layer is made of heat seal varnish. 11. The packaged food according to any one of claims 1 to 10, wherein the weight per area of the heat seal layer is in the range of 2 to 50 g/m ^<2> . The packaged food according to any one of claims 1 to 11, wherein the functional layer has a mass per area of 0.2 g/m2 ^or more. 13. Packaged food according to any one of claims 1 to 12, wherein the support layer has a thickness in the range of 5 to 40 [mu]m. 14. Packaged food according to any one of claims 1 to 13, wherein said flange has ribs. 15. The packaged food according to any one of claims 1 to 14, wherein the internal space of the food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas and carbon dioxide gas. 16. The packaged food according to any one of claims 1 to 15, wherein the food packaging container is a chilled food packaging container or a frozen food packaging container.

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